阅读说明：本技术 经聚合物稳定的液晶显示器的制造方法 (Method for producing polymer-stabilized liquid crystal displays ) 是由 S·格瑙克 T·拉霍尔 S·舒普弗 D·乌沙科夫 L·威格尔斯 于 2018-05-08 设计创作，主要内容包括：本发明涉及一种制造聚合物持续配向(PSA)类型液晶(LC)显示器的方法,其使用含有光可聚合单体的LC介质,且使用具有窄发射峰的光源以用于该单体的光聚合。(The invention relates to a method for manufacturing a Liquid Crystal (LC) display of the Polymer Sustained Alignment (PSA) type, using an LC medium containing a photo-polymerisable monomer and using a light source with a narrow emission peak for the photo-polymerisation of the monomer.)

1. A method of fabricating a Polymer Sustained Alignment (PSA) mode Liquid Crystal Display (LCD), comprising:

a) providing a first substrate and a second substrate, wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode,

b) interposing an LC medium between the first and the second substrate, the LC medium comprising one or more polymerizable compounds polymerizable by photopolymerization,

c) exposing the LC medium comprising the polymerisable compound to light emitted from a light source, thereby initiating photopolymerisation of the polymerisable compound,

characterized in that the light source in step c) emits light having an emission peak with a peak wavelength in the range of 280 to 420nm and a full width at half maximum (FWHM) of 30nm or less.

2. The method according to claim 1, characterized in that the light emitted by the light source has an emission peak having a peak wavelength in the range of 350nm to 400 nm.

3. A method according to claim 2, characterized in that the light emitted by the light source has an emission peak with a peak wavelength in the range of 360 to 385 nm.

4. A method according to any one of claims 1 to 3, characterized in that the light emitted by the light source has an emission peak with a FWHM of 20nm or less.

5. A method according to any one of claims 1 to 4, characterized in that the light source has a single emission peak.

6. Method according to any one of claims 1 to 5, characterized in that the light source is an LED lamp.

7. Method according to any one of claims 1 to 6, characterized in that the LCD further comprises a first alignment layer disposed on the surface of the first substrate contacting the LC medium, and optionally a second alignment layer disposed on the surface of the second substrate contacting the LC medium.

8. Method according to one of claims 1 to 7, characterized in that the first substrate is provided with a first electrode structure and the second substrate is provided with a second electrode structure.

9. Method according to one of claims 1 to 7, characterized in that one of the first and second substrates is provided with a first and second electrode structure and the other of the first and second substrates is not provided with an electrode structure.

10. Method according to any one of claims 1 to 9, characterized in that step c) comprises the following steps

c1) Exposing the LC medium containing the polymerizable compound to light emitted from a light source, thereby initiating photopolymerization of the polymerizable compound while applying a voltage to the electrode,

c2) exposing the LC medium comprising the photopolymerized polymerizable compound and any remaining unpolymerized polymerizable compound to light emitted from a light source, thereby initiating photopolymerization of the remaining unpolymerized polymerizable compound, while no voltage is applied to the electrodes,

wherein in one or both of steps c1) and c2), the light source is as defined in any one of claims 1 to 6.

11. Method according to claim 10, characterized in that the radiation intensity of the light source used in step c1) is 75 to 125mW/cm²。

12. Method according to claim 10 or 11, characterized in that in step c1), the LC medium comprising the polymerisable compound is exposed to light for a time of 30 to 240 s.

13. Method according to any one of claims 10 to 12, characterized in that the radiation intensity of the light source used in step c2) is 5 to 500mW/cm²。

14. Process according to any one of claims 10 to 13, characterized in that in step c2), the LC medium comprising the polymerisable compound is exposed to light for a time of 10 to 150 min.

15. The method according to any one of claims 1 to 14, further comprising the steps of: a sealant material is disposed between the first substrate and the second substrate and cured.

16. The method of claim 14, wherein the sealant material is cured by exposure to light radiation, wherein

i) The light radiation is chosen so as not to cause polymerization of the polymerizable compounds in the LC medium, and/or

ii) protecting the LC medium with the polymerizable compound from the light radiation used to cure the encapsulant material.

17. A method according to claim 15 or 16, characterized in that the sealant material is cured by exposure to a light source as defined in any one of claims 1 to 6.

18. Method according to claim 16 or 17, characterized in that the LC medium is protected from the light radiation used for curing the encapsulant material by means of a photomask.

19. Method according to any one of claims 1 to 18, characterized in that in step b) an LC medium comprising the polymerisable compound is inserted between the first and second substrates by means of One Drop Fill (ODF).

20. Method according to claim 19, characterized in that step b) comprises the following steps

b1) Dispensing a droplet or an array of droplets of the LC medium comprising the polymerisable compound on one of the first and second substrates,

b2) the other of the first and second substrates is placed over the substrate with the dispensed droplets of the LC medium, causing the droplets of the LC medium to spread and form a continuous layer between the two substrates.

21. Method according to any one of claims 1 to 20, characterized in that the LC medium additionally contains a self-aligning agent.

22. The method according to any one of claims 1 to 21, characterized in that the light source has an emission peak in the wavelength range in which the polymerizable compound shows absorption.

23. Process according to any one of claims 1 to 22, characterized in that the polymerizable compound is selected from Reactive Mesogens (RMs).

24. Method according to any one of claims 1 to 23, characterized in that the LCD is a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-positive-VA, PS-TN, SA-VA or SA-FFS mode.

25. A method of manufacturing a PSA mode LCD, comprising

a) Providing a first substrate and a second substrate, wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode,

b) interposing an LC medium between the first and the second substrate, the LC medium comprising one or more polymerizable compounds polymerizable by photopolymerization,

c) exposing the LC medium comprising the polymerisable compound to light emitted from a light source, thereby causing photopolymerization of the polymerisable compound,

characterized in that the light source in step c) is an LED lamp.

26. The method according to claim 25, which is as defined according to one or more of claims 2 to 5 and 7 to 24.

Background

Liquid Crystal (LC) display modes that have found both widespread interest and commercial use are the so-called "polymer sustained" (PS) or "polymer sustained alignment" (PSA) modes, which also occasionally use the term "polymer stabilized".

In PSA displays, LC media are used which contain an LC mixture (hereinafter also referred to as "host mixture") and further contain small amounts, typically < 1% by weight, for example 0.2 to 0.4% by weight, of one or more polymerisable compounds, which are typically selected from polymerisable mesogenic compounds or LC compounds, also referred to as "reactive mesogens" or RMs.

In PSA displays, the LC medium containing the polymerisable compounds is contained between two substrates. Each substrate is provided with an electrode structure or both electrode structures are placed on only one of the substrates. In addition, one or both substrates may contain an alignment layer disposed on the substrate or (if present) electrode structure so as to be in contact with the LC medium to induce initial alignment of the LC molecules.

After filling the LC medium into the display, the polymerisable compound or RM is polymerised or crosslinked in situ, typically by UV-photopolymerization, typically while applying a voltage to the electrodes of the display. The polymerization is carried out at a temperature at which the LC medium exhibits an LC phase, generally at room temperature. The polymerized or crosslinked RM is phase separated from the LC medium and forms a polymer layer on the substrate surface, where it creates and stabilizes a pre-tilt angle of the LC molecules with respect to the substrate. The pre-tilt angle generation and polymer stabilization effects have been shown to significantly reduce response times, among other things.

The ps (a) mode is used simultaneously in the various LC display modes. Thus, for example, PS-VA ("vertical alignment"), PS-OCB ("optically compensatory bend"), PS-IPS ("in-plane switching"), PS-FFS ("fringe field switching"), PS-UB-FFS ("ultra-bright FFS"), PS-TN ("twisted nematic") and PS-positive-VA mode ("positive VA") displays are known.

In PS-VA displays, an LC medium with negative dielectric anisotropy is contained between two substrates, each equipped with an electrode structure and optionally with an alignment layer, for example a rubbed polyimide layer. In the initial, non-addressed state, the LC molecules exhibit homeotropic (i.e. vertical or homeotropic) or tilted homeotropic alignment with respect to the substrates. Upon application of a voltage to the electrodes, the LC molecules realign parallel to the substrate.

For PS-VA displays, standard multi-domain VA (mva) or patterned VA (pva) pixel and electrode structure layouts may be used. It is also possible to use only one structured electrode without protrusions, which greatly simplifies the production and improves the contrast and transparency.

In a PS-FFS display, two electrodes are placed on only one of the two substrates. The structure of one electrode is in the form of comb teeth and the other is unstructured. When a voltage is applied to the electrodes, a strong electric field, the so-called "fringing field", is thus generated, which is close to the edges of the electrodes and penetrates the cell, having a strong vertical component and a strong horizontal component. FFS displays have low viewing angle dependence of contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy and an alignment layer, usually of polyimide, which induces planar (i.e. horizontal or parallel) alignment of the LC molecules in the non-addressed state.

Furthermore, PS-FFS displays are known which comprise a layer of an LC medium with a negative dielectric anisotropy instead of an LC medium with a positive dielectric anisotropy. LC media with negative dielectric anisotropy exhibit more favorable director orientations with less tilt and more twisted orientation than LC media with positive dielectric anisotropy, and therefore these displays have higher transmission.

In PS-positive-VA mode displays, the initial orientation of the LC molecules in the unaddressed state is homeotropic, as in PS-VA displays, however, the LC medium has a positive dielectric anisotropy. As in PS-IPS displays, in positive-VA displays, the two electrodes are disposed on only one of the two substrates and preferably exhibit an intermeshing, comb-like (interdigitated) structure. When a voltage is applied to the electrodes, an electric field is formed in a direction substantially parallel to the LC medium layer and the LC molecules realign substantially parallel to the substrates.

Below the layer formed by RM inducing the above-mentioned phase separation and polymerization of the pretilt angle, the PSA display usually contains an alignment layer, e.g. a polyimide alignment layer, which provides an initial alignment of the LC molecules before the polymer stabilization step.

Rubbed polyimide layers have long been used as alignment layers. However, the rubbing method causes several problems such as non-uniformity (mura), contamination, electrostatic discharge problems, residue, and the like. Therefore, instead of rubbing the polyimide layer, it is suggested to use a polyimide layer prepared by photo-alignment using photo-induced alignment surface alignment. This can be achieved by photolysis by means of polarized light, photodimerization, photoisomerization.

However, there is still a need for a suitably derivatized polyimide layer comprising photoreactive groups. Generally, the investment and cost for manufacturing the polyimide layer, processing the polyimide, and using bumps or polymer layers for modification is relatively large.

Furthermore, it is observed that detrimental interactions of the polyimide alignment layer with specific compounds of the LC medium often lead to a reduction of the electrical resistance of the display. Thus, the number of suitable and useful LC compounds is greatly reduced, sacrificing display parameters such as viewing angle dependence, contrast and response time, which are intended to be improved by using the LC compounds. Therefore, it is desirable to omit the polyimide alignment layer.

For some display modes, this is achieved by adding a self-alignment agent or additive to the LC medium, which induces the desired alignment, e.g. homeotropic or planar alignment, by an in situ self-assembly mechanism. Thus, the alignment layer on one or both of the substrates may be omitted. These display modes are also known as "self-aligned" or "self-aligned" (SA) modes.

In SA displays, small amounts, typically 0.1 to 2.5%, of self-aligning additives are added to the LC medium. Suitable self-aligning additives are, for example, compounds having an organic core group and one or more polar anchor groups attached thereto, which are capable of interacting with the substrate surface, causing the alignment of the additives on the substrate and also inducing the desired alignment in the LC molecules. Preferred self-aligning additives comprise, for example, mesogenic groups and linear or branched alkyl side chains which are terminated with one or more polar anchor groups, for example selected from hydroxyl, carboxyl, amino or thiol groups. The self-aligning additive may also contain one or more polymerizable groups, which may be polymerized under conditions similar to the RMs used in PSA processes.

To date, SA-VA displays and SA-FFS displays have been disclosed. Suitable self-alignment additives that induce homeotropic alignment, especially for use in SA-VA mode displays, are disclosed in, for example, US 2013/0182202 a1, US 2014/0838581 a1, US 2015/0166890 a1 and US 2015/0252265 a 1.

The SA mode may also be used in combination with the PSA mode. Thus, the LC media used in the combined mode display contains both one or more RMs and one or more self-aligning additives.

The PSA display may operate as either an Active Matrix (AM) or Passive Matrix (PM) display. In the case of AM displays, individual pixels are typically addressed by integral, non-linear active elements, such as for example Thin Film Transistors (TFTs), whereas in PM displays, individual pixels are typically addressed by multiplexing methods known from the prior art.

Particularly for monitor and especially TV applications, there is still a need for optimization of the response time and contrast and brightness (and thus transmittance) of LC displays. In these applications, the PSA process can provide significant advantages. In particular in the case of PS-VA, PS-IPS, PS-FFS and PS-positive-VA displays, a reduction in the response time associated with a measurable pretilt angle in the test cell can be achieved without significant adverse effects on other parameters.

A preferred method of applying LC media to AM type PSA displays is the so-called "one drop filling" (ODF) method, which is exemplarily and schematically illustrated in fig. 1. In a first step (a), a droplet or an array of droplets (2) of an LC medium is dispensed on a first substrate (1). The sealant material is placed in the region (3) between the LC droplet and the edge of the substrate (1). In a second step (b), in the vacuum assembly station, the second substrate (4) is attached and fixed to the first substrate (1), thus causing the LC droplets (2) to spread and form a continuous layer between the two substrates (1, 4).

After filling the LC medium into the display, the polymerisable compounds contained in the LC medium are typically polymerised or crosslinked in situ by UV-photopolymerisation, which is achieved by exposing the LC medium to UV-radiation, preferably while applying a voltage to the electrode structure. The polymerization is carried out at a temperature at which the LC medium exhibits an LC phase, generally at room temperature. As a result of UV exposure, the polymerized or crosslinked RMs phase separate from the LC medium and form a polymer layer on the substrate surface, where they give rise to a pre-tilt angle of the LC molecules with respect to the substrate.

For example in the case of PS-VA, PS-OCB, PS-FFS, PS-UB-FFS, PS-TN displays, the polymerization of the RM is preferably carried out with the application of a voltage, and in the case of PS-IPS displays, with or without application, preferably without application of a voltage. In the case of a PS-OCB display, it is possible to stabilize the bend structure, so that the offset voltage is either unnecessary or can be reduced. In the case of PS-VA displays, the pretilt has a positive effect on the response time.

However, the methods and methods used in the prior art for manufacturing PSA displays and the materials used therein still have some drawbacks.

For example, one problem observed in the prior art is that not all combinations of LC host mixtures and RMs are suitable for use in PSA displays, since, for example, only insufficient tilt angles can be generated or no tilt angles at all can be generated, or since, for example, the Voltage Holding Ratio (VHR) is insufficient for TFT display applications.

Furthermore, it has been found that LC mixtures and RMs known from the prior art still have some drawbacks when used in PSA displays. For example, in many common LC mixtures, the RMs of the prior art do often have high melting points and do only show limited solubility. Thus, RM tends to crystallize out of the LC mixture spontaneously. Furthermore, the risk of spontaneous polymerization prevents the LC host mixture from getting warm to dissolve the RM better, so high solubility is required even at room temperature. Furthermore, for example when filling LC media into LC displays, there is a risk of phase separation (chromatographic effects), which can greatly impair the uniformity of the display. This is further exacerbated by the fact that: LC media are usually filled into displays at low temperatures in order to reduce the risk of spontaneous polymerization (see above), which in turn has an adverse effect on solubility.

Furthermore, not all known RMs that are soluble in LC host mixtures are also suitable for use in PSA displays. Furthermore, it is often difficult to find a suitable selection criterion for the RM in addition to directly measuring the pre-tilt in a PSA display. If UV photopolymerization without the addition of photoinitiators, which is advantageous for certain applications, is desired, the selection of suitable RMs becomes even smaller.

The selected combination of LC host mixture/RM should have low rotational viscosity, good electrical properties and in particular a high VHR. In PSA displays, a high VHR after irradiation with UV light is particularly important, since UV exposure is not only performed as normal exposure during operation of the finished display, but it is also an essential part of the display production process.

The LC medium used in PSA displays should also be able to produce a small pretilt angle. Suitable and preferred materials are those that can produce a smaller pre-tilt angle after the same exposure time, and/or at least can produce the same pre-tilt angle after a shorter exposure time, as compared to prior art materials. This will allow for a reduction in display production time, also referred to as "takt time", and production costs.

Another problem in the production of PSA displays is that after photopolymerization to create the pretilt, the remaining amount of unpolymerized RM is present and removed. Unreacted RM can adversely affect the properties of the display, for example by polymerizing in an uncontrolled manner during operation of the display. This can cause defects in the display, such as so-called "image sticking".

The undesirable image sticking effect, also known as "image burn," means that the image produced in the display by the temporary addressing of individual pixels is visible even after the electric field in these pixels is switched off, or after other pixels have been addressed.

As mentioned above, image sticking may be caused by the presence of unpolymerized RMs. Uncontrolled polymerization of residual RMs is initiated by UV light or backlighting from the environment. In addressing the display area, this changes the tilt angle after a number of addressing cycles. Thus, the transmittance may change in the addressed areas, while it remains the same in the non-addressed areas.

Image sticking may also occur, for example, if LC media with a low VHR are used in PSA displays. The sunlight or UV components of the backlight may cause undesired decomposition reactions of LC molecules and thus initiate the production of ionic or radical impurities. These impurities may accumulate, in particular, on the electrodes or alignment layers, wherein they reduce the effective applied voltage.

LC media with negative dielectric anisotropy, in particular, for example for use in PS-VA or PS-FFS displays, often exhibit reduced reliability compared to LC media with positive dielectric anisotropy. This can be explained by the interaction of the LC molecules with the polyimide of the alignment layer, thus extracting ions from the polyimide alignment layer, and wherein LC molecules with negative dielectric anisotropy extract the particles more efficiently than LC molecules with positive dielectric anisotropy.

The term "reliability" as used hereinafter means the quality of performance of the LC medium and LC display over a period of time and under different pressure loads such as light load, temperature, humidity, voltage, and includes display effects such as image sticking (area and line image sticking), non-uniformity (mura), stains (yogore), etc., which are known to those skilled in the art of LC displays. The standard parameter for classifying reliability is the Voltage Holding Ratio (VHR) value, which is a measure for maintaining a continuous voltage in a test display. The higher the VHR value, the better the reliability of the LC medium or display.

Summary of The Invention

The invention relates to a method of manufacturing a PSA mode LC display, comprising

a) Providing a first substrate and a second substrate, wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode,

b) interposing an LC medium between the first and second substrates, the LC medium comprising one or more polymerisable compounds which are polymerisable by photopolymerisation,

c) exposing the LC medium comprising the polymerizable compound to light emitted from a light source, initiating photopolymerization of the polymerizable compound,

characterized in that the light source emits light having an emission peak with a peak wavelength in the range of 280 to 420nm and a Full Width Half Maximum (FWHM) of 30nm or less.

The invention further relates to a method of manufacturing a PSA-mode LC display comprising steps a), b) and c) as described above, wherein the light source used in step c) is an LED lamp.

The invention further relates to a PSA-type LC display obtained by the method as described above and below.

The LC display is preferably a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-positive-VA, PS-TN, SA-VA or SA-FFS display.

Brief Description of Drawings

Fig. 1 schematically illustrates an One Drop Fill (ODF) process.

Fig. 2 shows an emission spectrum of a UV LED lamp according to a preferred embodiment of the present invention.

Terms and definitions

As used herein, the term "full width at half maximum" or "FWHM" means the width of the measured spectral curve between those half maximum amplitude points on the y-axis.

Unless otherwise stated, the polymerizable compounds are preferably selected from achiral compounds.

As used herein, the term "electrode structure" includes an electrode layer, or an array of electrodes, patterned electrodes, or pixel electrodes, which may be a continuous layer, or a patterned electrode or pixel electrode.

As used herein, the terms "active layer" and "switchable layer" mean a layer in an electro-optical display, such as an LC display, which comprises one or more molecules with structural and optical anisotropy, such as for example LC molecules, which realign and thus change their orientation upon the occurrence of an external stimulus such as an electric or magnetic field, resulting in a change in the transmittance of the layer for polarized or unpolarized light.

As used herein, the terms "tilt" and "tilt angle" will be understood to mean the tilted alignment of the LC molecules of the LC medium with respect to the cell surfaces in an LC display, here preferably a PSA display. The terms "pre-tilt" and "pre-tilt angle" will be understood to mean the initial tilt angle of the LC molecules in the non-addressed display cell, which is produced by a PSA process involving the polymerisation of the polymerisable components of the LC medium.

The (pre-) tilt angle here denotes the average angle (< 90 °) between the longitudinal molecular axis of the LC molecules (LC director) and the surface of the substrates forming the LC cell. In curved displays the (pre-) tilt angle is given with respect to a tangent on the respective substrate.

A low (pre-) tilt angle value (i.e. a large deviation from 90 °) is equivalent to a large (pre-) tilt and indicates that a strong (pre-) tilt angle is generated, whereas a high (pre-) tilt angle value (i.e. a small deviation from 90 °) is equivalent to a small (pre-) tilt and indicates that a weak tilt angle is generated. Suitable methods for measuring the (pre-) tilt angle are given in the examples. The (pre) tilt angle values disclosed above and below relate to this measurement method, unless otherwise indicated.

As used herein, the terms "homeotropic alignment" and "homeotropic alignment" will be understood to mean an LC molecular alignment in which the molecular long axes of the LC molecules are substantially perpendicular with respect to the substrates.

As used herein, the terms "planar alignment" and "horizontal alignment" will be understood to mean that the LC molecules have their long molecular axes aligned generally parallel with respect to the substrates.

As used herein, the terms "reactive mesogen" and "RM" will be understood to mean a compound containing a mesogen or liquid crystal framework and one or more functional groups attached to the compound suitable for polymerization and also referred to as "polymerizable groups" or "P".

The term "polymerizable compound" as used herein, unless otherwise stated, will be understood to mean a polymerizable monomer compound.

As used herein, the term "low molecular weight compound" will be understood to mean a compound that is in monomeric form and/or a compound that is not prepared by polymerization, as opposed to a "polymeric compound" or "polymer".

As used herein, the term "non-polymerizable compound" will be understood to mean a compound that does not contain functional groups suitable for polymerization under the conditions typically applied for RM polymerization.

The term "mesogenic group" as used herein is known to those skilled in the art and described in the literature and means a group that intrinsically contributes to the creation of a Liquid Crystal (LC) phase in low molecular weight or polymeric substances due to the anisotropy of its attractive and repulsive interactions. The mesogenic group-containing compound (mesogenic compound) does not necessarily have to have an LC phase by itself. It is also possible for the mesogenic compounds to exhibit LC phase behavior only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are for example rigid rod elements or disk elements. A summary of the terms and definitions used in connection with mesogenic or LC compounds is given in Pure appl. chem.2001,73(5),888 and c.tschirske, g.pelzl, s.diele, angelw.chem.2004, 116, 6340-6368.

The term "spacer", hereinafter also referred to as "Sp", as used herein is known to those skilled in the art and is described in the literature, see, e.g., pureeppl. chem.2001,73(5),888 and c.tschieske, g.pelzl, s.diele, angelw.chem.2004, 116, 6340-6368. As used herein, the term "spacer group" or "spacer group" means a flexible group, such as an alkylene group, that connects a mesogenic group to a polymerizable group in a polymerizable mesogenic compound.

Detailed Description

The use of UV lamps, in particular LED lamps, with a narrow emission spectrum in the PSA method according to the invention provides several advantages, as will be explained below.

One advantage is that the light energy transfer to the polymerisable compound or RM in the LC medium is more efficient when using UV lamps, especially LED lamps, with only one narrow emission peak. This allows the UV intensity and/or UV irradiation time to be reduced, thus enabling a reduction in tact time and saving energy and production costs.

Another advantage is that the narrow emission spectrum of the lamp allows easier selection of wavelengths suitable for photopolymerization.

For example, it is no longer necessary to use a cut-off filter, which has been required for the metal halide lamps used hitherto for cutting off dangerous and harmful shorter UV wavelengths.

Furthermore, it may be easier to convert the radiation used for photopolymerization to longer UV wavelengths, thereby reducing or even avoiding the dangerous and detrimental effects of short UV light components.

Both reducing the intensity of UV radiation and shifting to longer UV wavelengths help protect organic materials in the display from damage that can be caused by UV light.

This also allows more flexibility in the selection of suitable and useful organic materials for use in displays, and expands the range of choices thereof, such as LC compounds or polymerisable compounds/RMs in LC media, or organic materials for use in alignment layers or color filters, for example.

For example, alkenyl compounds can now be used more freely in LC media without the risk of decomposition or interaction with the polyimide of the alignment layer. Furthermore, RMs with absorption at the longer wavelength side of the UV spectrum can now be used more efficiently and polymerized. Thus, reliability and VHR values can be improved.

The LED lamp is particularly suitable for achieving the above-mentioned advantageous effects because the LED lamp has a narrow emission spectrum. Furthermore, LEDs have a significantly longer lifetime and lower power consumption compared to metal halide lamps. Furthermore, LED lamps do not contain mercury, which is beneficial to the environment.

Some advantages of using LED lamps in the method according to the invention compared to common metal halide or UV fluorescent lamps are summarized in table 1 below.

TABLE 1 comparison of UV lamps

The method according to the invention thus achieves the following advantageous effects: fast and thorough RM polymerization, fast and controllable generation of low pretilt angles, and short response times, high stability of pretilt especially after UV exposure, reduced image sticking, and reduced ODF non-uniformity are achieved. Furthermore, it provides advantages related to the display manufacturing process, such as reduced tact time, savings in method costs, equipment and energy, and is also environmentally beneficial.

The LC displays produced using the process according to the invention are preferably PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-positive-VA, PS-TN, SA-VA or SA-FFS displays.

The structure of the display according to the invention conforms to the geometry as described in the prior art for PSA or SA displays.

In step a) of the method according to the invention, first and second substrates forming an LC display cell are provided, wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode.

The first and second substrates are preferably selected from glass or quartz substrates. At least one of the substrates should be capable of transmitting optical radiation for polymerizing the polymerizable components of the LC medium.

In the case of substrates provided with alignment layers prepared by photopolymerization and/or photoalignment, at least one of the substrates should be able to transmit the photopolymerized or photoaligned light radiation for the alignment layer material or a precursor thereof.

In one embodiment, especially for flexible displays, the substrate is selected from plastic substrates, for example comprising or made of polyesters such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyvinyl alcohol (PVA), Polycarbonate (PC) or triacetyl cellulose (TAC).

The display according to the invention further comprises two electrode structures, preferably in the form of transparent layers, applied on one or both of the two substrates.

Depending on the respective display type, the electrode structure can be designed by the skilled person on the basis of methods and materials known from the general knowledge or from the literature.

For example for PS-VA displays, the multi-domain orientation of LC molecules can be induced to form two, four or more different tilt alignment directions by providing electrodes with slits and/or bumps or protrusions.

Geometries without protrusions are preferred, in particular, in addition to those geometries in which the electrodes on the color filter side are unstructured and only the electrodes on the TFT side have slits. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US2006/0066793A 1.

In a preferred embodiment, in particular in a PS-VA, PS-OCB or PS-TN display, the first substrate is provided with a first electrode structure and the second substrate with a second electrode structure.

In a further preferred embodiment, in particular in a PS-positive-VA, PS-IPS, PS-FFS or PS-UB-FFS display, one of the first and second substrates is provided with the first and second electrode structures and the other of the first and second substrates is not provided with the electrode structures.

In another preferred embodiment, especially when the first and second substrates are each provided with one electrode structure, one of the first and second electrodes is a pixel electrode defining a pixel area, the pixel electrode is connected to a switching element disposed in each pixel area and optionally comprises a micro-slit pattern, and the other of the first and second electrodes is a common electrode layer, which may be disposed on an entire portion of the substrate facing the other substrate.

The display according to the present invention preferably comprises an alignment layer on one or both of the first and second substrates, which alignment layer induces an initial alignment of the LC molecules. The alignment layer is typically applied over the electrode (if present) so that it contacts the LC medium.

The alignment layer controls the alignment direction of LC molecules of the LC layer. For example, in PS-VA displays, the alignment layer is chosen such that it induces homeotropic or tilted homeotropic alignment of the LC molecules.

Suitable and preferred alignment layers for inducing homeotropic or tilted homeotropic alignment comprise or consist of, for example, polyimides, which may also be rubbed or prepared by photo-alignment methods.

Suitable polyimide alignment layer materials for homeotropic alignment are commercially available, such as for example AL60702 (from JSR).

Alignment layer materials that can be made from solution are preferred. These materials are preferably prepared from solutions in solvents, preferably organic solvents, such as, for example, N-methylpyrrolidone, 2-butoxyethanol or γ -butyrolactone.

In one embodiment, the alignment layer is formed by: a solution of an alignment layer material, such as for example a polyimide, or a precursor thereof, such as for example a polyimide precursor, is deposited on the substrate and the alignment layer material or precursor thereof is optionally cured by exposure to thermal and/or actinic radiation, for example UV radiation.

The alignment layer material or a precursor thereof may be deposited on the substrate, for example by a coating or printing method.

Preferred deposition techniques include, but are not limited to, dip coating, spin coating, ink jet printing, nozzle printing, letterpress printing, screen printing, gravure printing, doctor blade coating, roller printing, reverse-roller printing, lithography, dry lithography, flexographic printing, web printing, spray coating, curtain coating, brush coating, slot dye coating, or pad printing. For the manufacture of flexible LC displays, area printing methods compatible with flexible substrates are preferred, such as slot dye coating, spray coating and the like.

If a solvent is used to deposit the alignment layer material, it is preferably dried off or evaporated after deposition. Solvent evaporation may be supported, for example, by the application of heat and/or reduced pressure.

Preferred methods for curing the alignment layer are thermal curing and photo-curing, very preferably photo-curing. Photocuring is carried out, for example, by exposure to UV radiation. Suitable curing conditions can be selected by the person skilled in the art on the basis of his general knowledge of the precursor material used and as described in the literature. In the case of commercially available materials, suitable processing and/or curing conditions are often provided with the sale or sampling of the material.

In another preferred embodiment at least one of the substrates, preferably neither substrate, is provided with an alignment layer. Preferably, the LC medium according to this preferred embodiment contains a self-alignment (SA) additive, preferably in a concentration of 0.1 to 2.5%.

Preferred displays according to this preferred embodiment are SA-VA and SA-FFS displays.

Preferred SA additives for use in this preferred embodiment are selected from compounds comprising a mesogenic group and a linear or branched alkyl side chain terminated with one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups. More preferably the SA additive contains one or more polymerisable groups attached to the mesogenic group, optionally via a spacer. These polymerizable SA additives can be polymerized into LC media under similar conditions as the RMs applied in PSA processes.

Suitable SA additives for inducing homeotropic alignment, in particular for use in SA-VA mode displays, are disclosed in e.g. US 2013/0182202 a1, US 2014/0838581 a1, US 2015/0166890 a1 and US 2015/0252265 a 1.

In step b) of the method according to the invention, an LC medium comprising one or more polymerizable compounds which are polymerizable by photopolymerization is inserted between the first and second substrates.

The LC medium in step b) is preferably inserted between the two substrates by the ODF method.

Preferably, step b) comprises the following steps

b1) Dispensing a droplet or an array of droplets of an LC medium comprising a polymerisable compound on one of the first and second substrates, and

b2) the other of the first and second substrates is preferably placed under vacuum over the substrate to which the droplets of the LC medium are dispensed, so that the droplets of the LC medium are dispersed and form a continuous layer between the two substrates.

In one embodiment, the method according to the invention further comprises the following steps

-placing a sealant material between the first and second substrates, preferably in the area between the dispensed LC medium and the edge of the respective substrate, and

-curing the sealant material.

The sealant material is preferably deposited on the first substrate before the LC medium is deposited on said first substrate. The sealant material is then preferably cured after deposition of the LC medium on said first substrate, but before photo-polymerization of the polymerizable compound contained in the LC medium.

Preferably, the encapsulant material is exposed to heat and/or light radiation. In the case where the sealant material is cured by exposure to light radiation, it is preferred that

i) The light radiation is chosen so as not to initiate polymerization of the polymerizable compounds in the LC medium, and/or

i i) shield the LC medium from the light radiation used to cure the encapsulant material.

Preferably, the LC medium is shielded from the light radiation used to cure the encapsulant material by the photomask.

In one embodiment, the sealant material is cured by exposure to light from the same light source as described above and below for photopolymerization of the polymerizable compound in the LC medium.

PSA displays may include other elements such as color filters, black matrices, passivation layers, photo-retardation layers, transistor elements for addressing individual pixels, etc., all of which are well known to those skilled in the art and may be used without invasive technology.

In step c) of the method according to the invention, the LC medium comprising the polymerizable compound is exposed to light emitted from a light source, initiating photopolymerization of the polymerizable compound, wherein the light source emits light having an emission peak with a peak wavelength in the range of 280 to 420nm and a full width at half maximum (FWHM) of 30nm or less.

Preferably, the light emitted by the light source used in step c) has an emission peak with a peak wavelength in the range of 350 to 400 nm.

Very preferably, the light emitted by the light source used in step c) has an emission peak with a peak wavelength in the range of 360 to 385 nm.

Preferably, the light emitted by the light source used in step c) has an emission peak with a FWHM of 20nm or less.

Preferably, the light emitted by the light source used in step c) emits a spectrum with a single emission peak.

Preferably, the light source used in step c) emits UV light having a radiant energy of 0.1 to 50J/cm 2.

Preferably, the light source used in step c) is an LED lamp.

Very preferably, the light source in step b) is an LED lamp having an emission peak at 365 nm.

LED lamps are known to the skilled person and are commercially available.

Suitable and preferred LED lamps include, but are not limited to, those comprising or consisting of: semiconductor LEDs (p-n junction diodes), semiconductor laser diodes (LDs, another type of p-n junction diodes), also known as Injection Laser Diodes (ILDs) and Organic Light Emitting Diodes (OLEDs).

Preferred laser diodes include Double Heterostructure (DH) lasers, Quantum Well Lasers (QWLs), Quantum Cascade Lasers (QCLs), Interband Cascade Lasers (ICLs), distributed bragg reflector lasers (DBRs), Distributed Feedback Lasers (DFLs), vertical-cavity surface-emitting lasers (VCSELs), vertical external-cavity surface-emitting lasers (VECSELs), and external cavity diode lasers (EDLs).

Preferred OLEDs include Polymer Light Emitting Diodes (PLEDs) and small molecule OLEDs (SM-OLEDs), depending on the emissive material, and passive matrix OLEDs (pmoleds) and active matrix OLEDs (amoleds), depending on the addressing scheme.

LED lamps emitting UV light are commercially available from, for example, dr. The emission spectrum of a UV lamp having an emission peak at 365nm is shown in FIG. 2.

Upon polymerization, the polymerizable compounds in the LC medium form polymers or cross-linked polymers, which create a pre-tilt angle of the LC molecules in the LC medium.

Without wishing to be bound by a particular theory, it is believed that at least a portion of the crosslinked polymer formed by the polymerizable compound phase separates or precipitates out of the LC medium and forms a polymer layer or alignment layer disposed thereon on the substrate or electrode. Microscopic measurement data (e.g., SEM and AFM) have confirmed that at least a portion of the formed polymer accumulates at the LC/substrate interface.

The photopolymerization of the polymerizable compounds in the LC medium can be carried out in one step. Alternatively and preferably, the photopolymerization of the polymerizable compounds in the LC medium is carried out in two steps, preferably a first polymerization step with an applied voltage for generating the pre-tilt angle, and a second polymerization step with no applied voltage for polymerizing compounds that are not reacted, or not completely reacted, in the first step ("end cure").

Preferably, step c) comprises the following steps

c1) Exposing the LC medium containing the polymerizable compound to light emitted from a light source to initiate photopolymerization of the polymerizable compound while applying a voltage to the electrodes,

c2) exposing the LC medium comprising the photopolymerized polymerizable compound and any remaining unpolymerized polymerizable compound to light emitted from a light source to initiate photopolymerization of the remaining unpolymerized polymerizable compound without applying a voltage to the electrodes,

wherein in one or both of steps c1) and c2), preferably at least in step c1), very preferably in both step c1) and step c2), the light source is as defined above and below.

Preferably, the same light source is used in steps c1) and c 2).

Preferably, the radiation intensity of the light source used in step c1) is 5 to 500mW/cm²Very preferably 25 to 125mW/cm²。

Preferably, in step c1), the LC medium comprising the polymerisable compound is exposed to light for a time of 5 to 600s, very preferably 30 to 240 s.

Preferably, the radiation intensity of the light source used in step c2) is 5 to 500mW/cm 2.

Preferably, in step c2), the LC medium comprising the polymerizable compound is exposed to light for a time of 10 to 150 min.

Preferably, the light sources used in steps c), c1) and c2) have emission peaks in the wavelength range in which the photopolymerizable compound shows absorption.

Preferably, a voltage is applied to the electrodes during polymerization of the polymerizable compound in the LC medium.

In a preferred embodiment, the LC medium contains a photoinitiator for initiating photopolymerization of the polymerizable compound in the LC medium.

Suitable photoinitiators are described in the literature and can be readily selected by the skilled person, depending on the polymerizable compound and the desired polymerization method.

Suitable photoinitiators for free-radical polymerization are, for exampleOrCommercially available photoinitiators of the series (Ciba AG), such as, for example IrgacureOr

If a photoinitiator is added to the LC medium, the proportion thereof is preferably from 0.001 to 5% by weight, particularly preferably from 0.001 to 3% by weight, based on the total amount of polymerizable compounds in the LC medium.

If a photoinitiator is added to the LC medium, the proportion thereof is preferably from 1 to 10,000ppm, very preferably from 10 to 500ppm, based on the total solids content of the LC medium (excluding solvent).

Preferably, the polymerisable compounds used in the polymerisable component of the LC medium are selected such that they can be photopolymerised without initiator. This provides advantages, such as for example lower material costs and less contamination of the LC medium by possible residual amounts of initiator or decomposition products thereof.

In another preferred embodiment, the LC medium contains a polymerization inhibitor or stabilizer, which inhibits photopolymerization of the polymerizable compound in the LC medium. It may be advantageous to add inhibitors or stabilizers to prevent undesired spontaneous polymerization of the polymerizable compounds in the LC medium, for example during storage or transport.

Suitable types and amounts of inhibitors and stabilizers are known to those skilled in the art and are described in the literature. Particularly suitable stabilizers are, for example, those fromCommercially available stabilizers of the series (Ciba AG), such as for example1076 or1010. Other suitableAnd preferred initiators are selected from those of table D below.

If inhibitors or stabilizers are added to the LC medium, the proportion thereof is preferably from 10 to 500,000ppm, particularly preferably from 50 to 50,000ppm, based on the total amount of polymerizable compounds in the LC medium (excluding solvent).

If inhibitors or stabilizers are added to the LC medium, the proportion thereof is preferably from 1 to 10,000ppm, very preferably from 10 to 500ppm, based on the total amount of solids in the LC medium (excluding solvent).

The LC medium preferably comprises a polymerizable component a) comprising, preferably consisting of, one or more polymerizable compounds, and a liquid-crystalline component B) comprising, preferably consisting of, one or more mesogenic or liquid-crystalline compounds.

The liquid-crystalline component B) of the LC media according to the invention is also referred to hereinafter as "LC host mixture" and preferably contains only LC compounds selected from non-polymerizable low-molecular-weight compounds and optionally additives, such as polymerization initiators, inhibitors, etc.

The proportion of the total polymerisable constituents in the LC medium is preferably from > 0 to ≦ 5%, very preferably from > 0 to ≦ 1%, most preferably from 0.05 to 0.5%.

Preferred are achiral polymerizable compounds, and preferred are LC media wherein the compounds of the polymerizable component are exclusively selected from the group consisting of achiral compounds.

In a preferred embodiment, the polymerizable compounds in component a) have an absorption maximum at longer UV wavelengths, preferably 340nm or longer, to avoid short UV light exposure in PSA processes.

In a preferred embodiment of the invention, the polymerizable compound is selected from the group consisting of formula I

R^a-B¹-(Z^b-B²)_m-R^b I

Wherein the individual radicals are identical or different on each occurrence and each, independently of one another, has the following meaning:

R^aand R^bP, P-Sp-, H, F, Cl, Br, I, -CN, -NO₂、-NCO、-NCS、-OCN、-SCN、SF₅Or a straight-chain or branched alkyl group having 1 to 25C atoms, wherein, in addition, one or more non-adjacent CH groups₂The radicals may, independently of one another, be composed of-C (R)⁰)＝C(R⁰⁰)-、-C≡C-、-N(R⁰⁰) -, -O-, -S-, -CO-O-, -O-CO-O-in such a way that O and/or S atoms are not directly linked to one another, and wherein, in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, wherein if B is B¹And/or B²Containing saturated C atoms, then R^aAnd/or R^bIt may also represent a group spiro-linked to this saturated C atom,

wherein the radical R^aAnd R^bOne of which represents or contains the group P or P-Sp-,

p is a polymerizable group, and P is a polymerizable group,

sp is a spacer group or a single bond,

B¹and B²Is an aromatic, heteroaromatic, cycloaliphatic or heterocyclic radical, preferably having from 4 to 25 ring atoms, which may also contain fused rings and which is unsubstituted or mono-or polysubstituted by L,

Z^bis-O-, -S-, -CO-O-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-(CH₂)_n1-、-CF₂CH₂-、-CH₂CF₂-、-(CF₂)_n1-、-CH＝CH-、-CF＝CF-、-C≡C-、-CH＝CH-COO-、-OCO-CH＝CH-、CR⁰R⁰⁰Or a single bond, or a mixture of single bonds,

R⁰and R⁰⁰Each independently of the others, represents H or an alkyl radical having 1 to 12C atoms,

m represents 0, 1,2,3 or 4,

n1 represents 1,2,3 or 4,

l is P, P-Sp-, OH, CH₂OH、F、Cl、Br、I、-CN、-NO₂、-NCO、-NCS、-OCN、-SCN、-C(＝O)N(R^x)₂、-C(＝O)Y¹、-C(＝O)R^x、-N(R^x)₂Optionally substituted silyl, optionally substituted aryl having 6 to 20C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25C atoms, wherein additionally one or more H atoms may be replaced by F, Cl, P or P-Sp-,

p and Sp have the meanings indicated above,

Y¹represents a halogen, and is characterized in that,

R^xdenotes P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25C atoms, wherein, in addition, one or more non-adjacent CH₂The groups may be replaced by-O-, -S-, -CO-O-, -O-CO-O-in such a way that the O and/or S atoms are not directly attached to each other, and wherein in addition, one or more H atoms may be replaced by F, Cl, P, or P-Sp-, an optionally substituted aryl or aryloxy group having 6 to 40C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40C atoms.

Preferred compounds of formula I are those of the following: wherein B is¹And B²Each independently of the others, 1, 4-phenylene, 1, 3-phenylene, naphthalene-1, 4-diyl, naphthalene-2, 6-diyl, phenanthrene-2, 7-diyl, 9, 10-dihydro-phenanthrene-2, 7-diyl, anthracene-2, 7-diyl, fluorene-2, 7-diyl, coumarin, flavone, wherein in addition one or more CH groups in these groups may be replaced by N, cyclohexane-1, 4-diyl, wherein in addition one or more non-adjacent CH groups₂The radicals being replaced by O and/or S, 1, 4-cyclohexenylene, bicyclo [1.1.1]Pentane-1, 3-diyl, bicyclo [2.2.2]Octane-1, 4-diyl, spiro [3.3]Heptane-2, 6-diyl, piperidine-1, 4-diyl, decahydronaphthalene-2, 6-diyl, 1,2,3, 4-tetrahydronaphthalene-2, 6-diyl, indan-2, 5-diyl or octahydro-4, 7-methanoindan-2, 5-diyl, wherein all these radicals may be unsubstituted or mono-or polysubstituted with L as defined above.

Very preferred compounds of the formula I are those in which B¹And B²Those which each, independently of one another, represent 1, 4-phenylene, 1, 3-phenylene, naphthalene-1, 4-diyl or naphthalene-2, 6-diyl.

Very preferably, the compound of formula I is selected from the following formulae:

wherein the individual radicals are identical or different on each occurrence and each, independently of one another, has the following meaning:

P¹、P²、P³is vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane or epoxy,

Sp¹、Sp²、Sp³is a single bond or a spacer as defined for Sp, wherein additionally the group P¹-Sp¹-、P¹-Sp²-and P³-Sp³One or more of (A) may represent R^aaProvided that the group P present¹-Sp¹-、P²-Sp²And P³-Sp³One of-and R^aaIn contrast to this, the present invention is,

R^aais H, F, Cl, CN or a linear or branched alkyl radical having 1 to 25C atoms, where, in addition, one or more non-adjacent CH₂The radicals may each, independently of one another, be composed of (R)⁰)＝C(R⁰⁰)-、-C≡C-、-N(R⁰) -, -O-, -S-, -CO-O-, -O-CO-O-in such a way that O and/or S atoms are not directly linked to one another, andwherein additionally one or more H atoms may be replaced by: F. cl, CN or P¹-Sp¹Particular preference is given to linear or branched, optionally monofluorinated or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12C atoms (where alkenyl and alkynyl have at least two C atoms and the branched radical has at least three C atoms),

R⁰、R⁰⁰is H or alkyl having 1 to 12C atoms,

R^yand R^zIs H, F, CH₃Or CF₃，

X¹、X²、X³is-CO-O-, -O-CO-or a single bond,

Z¹is-O-, -CO-, -C (R)^yR^z) -or-CF₂CF₂-，

Z²、Z³is-CO-O-, -O-CO-, -CH₂O-、-OCH₂-、-CF₂O-、-OCF₂-、-(CH₂)_n-, -CH-, -CF-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond, wherein n is 2,3 or 4, and Z²And Z³One of which is not a single bond,

l is F, Cl, CN, P¹-Sp¹Or a linear or branched, optionally mono-or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12C atoms,

l ', L' are H, F or Cl,

r is 0, 1,2,3 or 4,

s is 0, 1,2 or 3,

t is 0, 1 or 2,

x is 0, 1 or 2.

Particularly preferred are compounds of formula M2, M13, M17, M22, M23, M24 and M30.

More preferred are the tri-reactive compounds M15 to M30, in particular M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31.

In the compounds of the formulae M1 to M31, the radicals

Preferably is

Or

Wherein L, identically or differently on each occurrence, has one of the meanings given above or below and is preferably F, Cl, CN, NO₂、CH₃、C₂H₅、C(CH₃)₃、CH(CH₃)₂、CH₂CH(CH₃)C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Or P-Sp-, very preferably F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃、OCF₃Or P-Sp-, more preferably F, Cl, CH₃、OCH₃、COCH₃Or OCF₃In particular F or CH₃。

Preferred compounds of the formulae M1 to M31 are those in which P¹、P²And P³Those compounds which represent acrylate, methacrylate, oxetane or epoxy groups, very preferably acrylate or methacrylate groups.

More preferred compounds of formulae M1 to M31 are those wherein Sp¹、Sp²And Sp³Those compounds which are single bonds.

More preferred compounds of formulae M1 to M31 are those wherein Sp¹、Sp²And Sp³One of them is a single bond and Sp¹、Sp²And Sp³The other of which is different from those of the single bond.

More preferred compounds of formulae M1 to M31 are those in which the group Sp is different from a single bond¹、Sp²And Sp³Is represented by- (CH)₂)_s1-X "-those compounds in which s1 is an integer from 1 to 6, preferably 2,3,4 or 5, and X" is a bond to the phenyl ring and is-O-, -O-CO-, -CO-O, -O-CO-O-or a single bond.

More preferably, the polymerizable compound and RM are selected from those of table E below.

Especially preferred are LC media comprising one, two or three polymerisable compounds of formula I.

Preferably, the proportion of compounds of formula I in the LC medium is from 0.01 to 5%, very preferably from 0.05 to 1%, most preferably from 0.1 to 0.5%.

In a preferred embodiment of the present invention, the polymerizable component a) medium comprises, very preferably consists of, one or more polymerizable compounds of the preferred embodiments as described above.

In addition to the polymerizable component a) as described above, the LC medium contains an LC component B), or an LC host mixture comprising one or more, preferably two or more, LC compounds selected from the group of non-polymerizable low molecular weight compounds. These LC compounds are selected so as to be stable and/or non-reactive to the polymerization reaction under the conditions applied for the polymerization of the polymerizable compounds.

The proportion of LC component B) in the LC medium is preferably from 95 to < 100%, very preferably from 99 to < 100%.

Examples of these compounds are the compounds shown below.

Preference is given to LC media in which the LC component B) or the LC host mixture has a nematic LC phase, and preferably no chiral liquid crystal phase.

Furthermore, preference is given to LC media which are achiral polymerizable compounds and in which the compounds of component A) and/or B) are selected exclusively from the group consisting of achiral compounds.

The LC component B) or the LC host mixture is preferably a nematic LC mixture.

In a first preferred embodiment, the LC medium contains an LC component B), or an LC host mixture, based on a compound with negative dielectric anisotropy. The LC medium is particularly suitable for use in PS-VA, SA-VA and PS-UB-FFS displays.

Preferred compounds for use in the LC host mixture with negative dielectric anisotropy according to this first preferred embodiment are selected from table a below.

In a second preferred embodiment, the LC medium contains an LC component B), or an LC host mixture, based on a compound with positive dielectric anisotropy. The LC media are particularly suitable for use in PS-OCB, PS-TN, PS-positive-VA, PS-IPS, PS-FFS or SA-FFS displays.

Preferred compounds for use in the LC host mixture with positive dielectric anisotropy according to this second embodiment are selected from table B below.

The nematic phase range of the LC medium and LC host mixture used in the displays according to the invention is at least 80K, particularly preferably at least 100K, and the rotational viscosity is 250mPa or less at 20 DEG C^.s, preferably ≦ 200mPa^.s。

The LC media based on compounds with negative dielectric anisotropy, in particular for use in PS-VA and PS-UB-FFS displays, according to the first preferred embodiment have a negative dielectric anisotropy Δ ∈ at 20 ℃ and 1kHz, preferably from-0.5 to-10, in particular from-2.5 to-7.5.

Based on the compounds with negative dielectric anisotropy according to the first preferred embodiment, in particular for use in PS-VA and PS-UB-FFS displays, the birefringence Δ n of the LC medium is preferably less than 0.16, particularly preferably from 0.06 to 0.14, very particularly preferably from 0.07 to 0.12.

The positive dielectric anisotropy Δ ∈ of the LC media at 20 ℃ and 1kHz is preferably from +2 to +30, very preferably from +3 to +20, most preferably from +4 to +17, based on the compounds according to the second preferred embodiment, in particular for use in PS-OCB, PS-TN, PS-IPS, PS-positive-VA, PS-FFS and SA-FFS displays.

Based on the compounds with positive dielectric anisotropy used in PS-OCB displays according to the second preferred embodiment, the birefringence Δ n of the LC medium is from 0.14 to 0.22, very preferably from 0.16 to 0.22.

The birefringence Δ n of the LC medium is preferably from 0.07 to 0.15, very preferably from 0.08 to 0.13, based on compounds with positive dielectric anisotropy, according to the second preferred embodiment, of the type used in PS-TN, PS-positive-VA, PS-IPS, PS-FFS or SA-FFS.

Based on the compounds with positive dielectric anisotropy used in the displays of the type PS-TN-, PS-positive-VA-, PS-IPS-or PS-FFS-according to the second preferred embodiment, the LC medium according to the invention has a positive dielectric anisotropy Δ ε of from +2 to +30, particularly preferably from +3 to +20, at 20 ℃ and 1 kHz.

Preferably, the LC medium according to the invention consists essentially of polymerizable component a) and LC component B) (or LC host mixture), as described above and below.

In another preferred embodiment, the LC medium additionally comprises one or more further components or additives, which are preferably selected from the list comprising, but not limited to: comonomers, chiral dopants, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricants, dispersants, hydrophobing agents, binders, flow improvers, defoamers, oxygen scavengers, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

These additives may be polymerizable or non-polymerizable. Accordingly, the polymerizable additives are classified as polymerizable component or component a). Accordingly, the non-polymerizable additive is classified as non-polymerizable component or component B).

In a preferred embodiment, the LC medium preferably contains one or more chiral dopants in a concentration of 0.01 to 1%, very preferably 0.05 to 0.5%. The chiral dopant is preferably selected from the group consisting of the compounds from table B below, very preferably from the group consisting of: r-1011 or S-1011, R-2011 or S-2011, R-3011 or S-3011, R-4011 or S-4011 and R-5011 or S-5011.

In another preferred embodiment, the LC medium contains a racemate of one or more chiral dopants, preferably selected from the chiral dopants mentioned in the preceding paragraphs.

Furthermore, it is possible to add the following to the LC medium, for example as described in DE-a 2209127, 2240864, 2321632, 2338281, 2450088, 2637430 and 2853728: for example 0 to 15% by weight of pleochroic dyes, furthermore nanoparticles, conductive salts, preferably ethyldimethyldodecylammonium 4-hexyloxybenzoate, tetrabutyltetraphenylammonium borate or crown ether double salts for improving the conductivity, or agents for adjusting the dielectric anisotropy, the viscosity and/or the alignment of the nematic phase.

The individual LC compounds used in component B) of the LC mediｃA are known or the preparation thereof is readily obtainable from the prior art by the person skilled in the relevant art, since it is based on standard methods described in the literature, for example EP-A-0364538, DE-A-2636684 and DE-A-3321373.

The LC media used according to the invention can be prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned compounds with one or more polymerisable compounds as defined above, and optionally with further LC compounds and/or additives. In general, the desired amount of the components used in lesser amounts is advantageously dissolved in the components making up the main constituent at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation after thorough mixing.

It is obvious to the person skilled in the art that the LC medium as used in the present invention may also comprise compounds in which e.g. H, N, O, Cl, F have been replaced by corresponding isotopes, such as deuterium and the like.

Tables a-E show suitable and preferred components of LC media as used in the present invention. Compounds suitable for use in LC host mixtures having negative dielectric anisotropy are listed in table a. Suitable compounds for LC host mixtures with positive dielectric anisotropy are listed in table B. Suitable compounds for use as chiral dopants are listed in table C. Suitable compounds for use as stabilizers are listed in table D. Suitable compounds for use as RMs are listed in table E.

TABLE A

The following abbreviations are used:

(n, m, z: in each case independently of one another 1,2,3,4, 5 or 6)

AIK-n-F

AIY-n-Om

AY-n-Om

B-nO-Om

B-n-Om

B-nO-O5i

CB-n-m

CB-n-Om

PB-n-m

PB-n-Om

BCH-nm

BCH-nmF

BCN-nm

C-1V-V1

CY-n-Om

CY(F,Cl)-n-Om

CY(Cl,F)-n-Om

CCY-n-Om

CCY(F,Cl)-n-Om

CCY(Cl,F)-n-Om

CCY-n-m

CCY-V-m

CCY-Vn-m

CCY-n-OmV

CBC-nmF

CBC-nm

CCP-V-m

CCP-Vn-m

CCP-nV-m

CCP-n-m

CPYP-n-(O)m

CYYC-n-m

CCYY-n-(O)m

CCY-n-O2V

CCH-nOm

CCC-n-m

CCC-n-V

CY-n-m

CCH-nm

CC-n-V

CC-n-V1

CC-n-Vm

CC-V-V

CC-V-V1

CC-2V-V2

CVC-n-m

CC-n-mV

CCOC-n-m

CP-nOmFF

CH-nm

CEY-n-Om

CEY-V-n

CVY-V-n

CY-V-On

CY-n-O1V

CY-n-OC(CH₃)＝CH₂

CCN-nm

CY-n-OV

CCPC-nm

CCY-n-zOm

CPY-n-Om

CPY-n-m

CPY-V-Om

CQY-n-(O)m

CQIY-n-(O)m

CCQY-n-(O)m

CCQIY-n-(O)m

CPQY-n-(O)m

CPQIY-n-(O)m

CPYG-n-(O)m

CCY-V-Om

CCY-V2-(O)m

CCY-1V2-(O)m

CCY-3V-(O)m

CCVC-n-V

CCVC-V-V

CPYG-n-(O)m

CPGP-n-m

CY-nV-(O)m

CENaph-n-Om

COChrom-n-Om

COChrom-n-m

CCOChrom-n-Om

CCOChrom-n-m

CONaph-n-Om

CCONaph-n-Om

CCNaph-n-Om

CNaph-n-Om

CETNaph-n-Om

CTNaph-n-Om

CK-n-F

CLY-n-Om

CLY-n-m

LYLI-n-m

CYLI-n-m

LY-n-(O)m

COYOICC-n-m

COYOIC-n-V

CCOY-V-O2V

CCOY-V-O3V

COY-n-Om

CCOY-n-Om

D-nOmFF

PCH-nm

PCH-nOm

PGIGI-n-F

PGP-n-m

PP-n-m

PP-n-2V1

PYP-n-mV

PYP-n-m

PGIY-n-Om

PYP-n-Om

PPYY-n-m

YPY-n-m

YPY-n-mV

PY-n-Om

PY-n-m

PY-V2-Om

DFDBC-n(O)-(O)m

Y-nO-Om

Y-nO-OmV

Y-nO-OmVm'

YG-n-Om

YG-nO-Om

YGI-n-Om

YGI-nO-Om

YY-n-Om

YY-nO-Om

In a preferred embodiment of the present invention, the LC medium according to the present invention comprises one or more compounds selected from the group consisting of the compounds from table a.

TABLE B

(n＝1-15；(O)C_nH_2n+1Means C_nH_2n+1Or OC_nH_2n+1)

In a preferred embodiment of the present invention, the LC medium according to the present invention comprises one or more compounds selected from the group consisting of the compounds from table B.

Watch C

Table C shows possible chiral dopants that can be added to the LC media according to the invention.

The LC medium preferably comprises from 0 to 10% by weight, in particular from 0.01 to 5% by weight, particularly preferably from 0.1 to 3% by weight, of a dopant. The LC medium preferably comprises one or more dopants selected from the group consisting of the compounds from table C.

Table D

Table D shows possible stabilizers that may be added to the LC media according to the invention.

(where n represents an integer of 1 to 12, preferably 1,2,3,4, 5, 6, 7 or 8, the terminal methyl group not being shown).

The LC medium preferably comprises from 0 to 10% by weight, in particular from 1ppm to 5% by weight, particularly preferably from 1ppm to 1% by weight, of stabilizer. The LC medium preferably comprises one or more stabilizers selected from the group consisting of the compounds from table D.

TABLE E

Table E shows illustrative reactive mesogenic compounds that can be used in LC media according to the invention.

In a preferred embodiment, the mixture according to the invention comprises one or more polymerizable compounds selected from the group of compounds of table E. Of these compounds, the compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122 are particularly preferred.

The following examples illustrate the invention without limiting it. However, it shows the concept of mixtures of the compounds to be used preferably and their individual concentrations and their combinations with one another, which are preferred by the person skilled in the art. Furthermore, embodiments may be obtained in which features and combinations of features are described.

The following abbreviations and symbols are used:

V₀representing the threshold voltage at 20 ℃, capacitive[V]，

n_eRepresents an extraordinary refractive index at 20 ℃ and 589nm,

n_oshowing the ordinary refractive index at 20 c and 589nm,

an represents optical anisotropy at 20 ℃ and 589nm,

ε_⊥represents the dielectric constant perpendicular to the director at 20 c and 1kHz,

ε_||represents the dielectric constant parallel to the director at 20 c and 1kHz,

Δ ε represents the dielectric anisotropy at 20 ℃ and 1kHz,

p. and T (N, I) represents clearing point [ ° C ],

γ₁shows the rotational viscosity [ mPas ] at 20 DEG C]，

K₁Denotes the elastic constant at 20 ℃ for "splay" deformation [ pN]，

K₂Denotes the elastic constant at 20 ℃ for "distortion" deformation [ pN]，

K₃Denotes the elastic constant at 20 ℃ for "bending" deformation pN]。

All concentrations in this application are given in weight percent and refer to the corresponding whole mixture, which contains all solid or liquid crystal components (without solvent), unless explicitly stated otherwise.

Unless otherwise indicated, all temperature values indicated in the present application, such as melting point T (C, N), transition T (S, N) from smectic phase (S) to nematic phase (N) and clearing point T (N, I) are expressed in degrees celsius (° C). M.p. denotes melting point, cl.p. ═ clearing point. Furthermore, C ═ liquid crystal phase, N ═ nematic phase, S ═ smectic phase and I ═ isotropic phase. The data between these symbols represents the transition temperature.

All Physical Properties are and have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals" Status 1997 for 11 months, Merck KGaA, Germany and apply at temperatures of 20 ℃ and Δ n is determined at 589nm and Δ ε is determined at 1kHz, unless explicitly stated otherwise in each case.

The term "threshold voltage" as used in the present invention relates to the capacitive threshold (V)₀) It is also referred to as Freedericks threshold unless otherwise noted. In an embodiment, the optical threshold is also for a relative contrast (V) of 10% as usual₁₀) Given below.

Unless otherwise indicated, the process of polymerizing the polymerizable compounds in a PSA display as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably at room temperature.

Unless otherwise indicated, methods of preparing test cartridges and measuring their electro-optic and other properties are performed by the methods described below or similar methods thereto.

Examples

LC host mixtures

Host mixture 1

Nematic LC host mixtures N1 were formulated as follows.

Host mixture 2

Nematic LC host mixtures N2 were formulated as follows.

Host mixture 3

Nematic LC host mixtures N3 were formulated as follows.

2. Polymerizable mixture

The polymerizable mixture was prepared by: in each case, one of the Reactive Mesogens (RMs) shown below was added to one of the nematic LC host mixtures N1-N3, respectively, at a concentration of 0.3 wt.%.

RM structure

Unless otherwise stated, the methods of preparing the test cartridges and measuring their electro-optical and other properties are performed by methods as described below or similar thereto.

VHR, reliability

The display used for measuring the voltage holding ratio consists of two plane-parallel glass outer plates spaced 6 μm apart, each having an electrode layer inside and an ungrased VA-polyimide alignment layer (JSR-PI2) on top, which affects the homeotropic edge alignment of the liquid crystal molecules.

The polymerizable mixture according to the invention is introduced into a display or a test cell and the polymerizable compound is polymerized by irradiation with UV light of defined intensity. Two UV irradiation steps are performed, the first step being hereinafter referred to as "UV 1" and the second step being hereinafter referred to as "UV 2". In the UV1 step, the irradiation time is 5 minutes while applying a voltage (typically 40V) to the display_ppSquare wave, 200 Hz). In step UV2, the irradiation time was 60 minutes, and no voltage was applied. In the examples, the 365nm LED lamp from hounle described above, with an intensity of 85mW/cm, was used for polymerization in two UV steps, unless otherwise indicated²And has an emission spectrum as shown in fig. 2. UV intensity was measured using a standard UVA meter (advanced hounle UV meter with UVA sensor).

For comparison reasons, some test cartridges use current standard UV lamps instead of LED lamps for UV1 and UV2 illumination. In these cases, forUV1, Metal-Halide lamps from Hoyle with an intensity of 100mW/cm2 and a 320nm cut-off filter were used for the polymerization. For UV2, there will be 3.5mW/cm²UV fluorescent lamps of intensity and without any cut-off filter were used for polymerization. The illumination time is the same as that of the LED method. The UV intensity was measured using a standard UVA meter without a cut-off filter (advanced hounle UV meter with UVA sensor).

VHR values were determined before and after 1V, 60Hz, 64. mu.s pulse, UV exposure at 100 ℃ (measuring device: Autronic-Melchers VHRM-105).

VHR values are shown in table 2.

TABLE 2 VHR values (in%)

As can be seen from table 2, the VHR values of all mixtures after UV irradiation and polymerization process using LED UV lamps according to the invention were higher compared to after UV irradiation and polymerization using standard UV lamps. This results in better reliability.

It can also be seen from table 2 that even LC host mixtures without any polymerisable compounds show higher VHR values after irradiation with LED UV lamps compared to after irradiation with standard UV lamps. This means that UV irradiation using LED lamps is milder (softer) for the LC host mixture and therefore less risky to damage the LC host mixture than standard UV polymerization methods.

This shows that the UV irradiation method using LED lamps is highly suitable for maintaining a high VHR after UV exposure, independent of the LC host mixture or polymerizable compound.

Pre-tilt angle

The PS-VA display test cell used to measure tilt angle consisted of two flat parallel glass outer plates spaced 4 μm apart, each with an electrode layer inside, with a discontinuous gap (dashed gap) on top of the electrode layer and an ungrasped VA-polyimide alignment layer (JSR-PI2) that affected the homeotropic edge alignment of the LC molecules. The electrodes of the top and bottom glasses are parallel but moved. The top glass has an extra resin black mask to cover the unaligned (misalignment) regions.

The polymerizable mixture according to the present invention was introduced into a test cell, and the polymerizable compound was polymerized by irradiation with UV light for 2 minutes (unless otherwise stated), while a voltage (typically 40V) was applied to the display_ppSquare wave, 200 Hz). In the examples, the intensity from Hoyle described previously was 85mW/cm unless otherwise indicated²The 365nm LED lamp was used for polymerization. UV intensity was measured using a standard UVA meter (advanced hounle UV meter with UVA sensor).

The pre-tilt angle is determined after UV irradiation and polymerization of the polymerizable compound are performed under the conditions as described above. The tilt angle was determined by Axo-Scan (Axometrics, Inc.). Here, a high value (i.e., a large deviation from the 90 ° angle) corresponds to a large inclination.

The pre-tilt angle is shown in table 3.

TABLE 3 Pre-Tilt Angle

¹⁾5 minutes irradiation time

²⁾Irradiation with 405nm LED

As can be seen from Table 3, different combinations of RM and LC mastermix using LED UV lamps may produce pre-tilt angles. This shows that the UV irradiation and polymerization method using LED lamps according to the present invention is suitable for manufacturing PS-VA displays.