阅读说明：本技术 液晶显示装置及液晶显示装置的制造方法 (Liquid crystal display device and method for manufacturing liquid crystal display device ) 是由 水崎真伸 川平雄一 于 2018-03-22 设计创作，主要内容包括：本发明提供一种即便在使反应性单体聚合而形成了相位差层的情况下,相对于热而言的相位差的稳定性也优良,且能防止因散射引起对比度下降的液晶显示装置,及适于制造该液晶显示装置的液晶显示装置的制造方法。本发明的液晶显示装置具有一对基板、及设在所述一对基板间的液晶层,所述一对基板中的至少一方包含含有至少1种单体的聚合物的相位差层,所述至少1种单体包含通过偏振光表现取向性的光取向性单体。(The present invention provides a liquid crystal display device which has excellent stability of retardation with respect to heat and can prevent contrast from being lowered due to scattering even when a retardation layer is formed by polymerizing a reactive monomer, and a method for manufacturing the liquid crystal display device which is suitable for manufacturing the liquid crystal display device. The liquid crystal display device of the present invention includes a pair of substrates, and a liquid crystal layer provided between the pair of substrates, wherein at least one of the pair of substrates includes a retardation layer containing a polymer of at least 1 kind of monomer, and the at least 1 kind of monomer includes a photo-alignment monomer exhibiting alignment properties by polarized light.)

1. A liquid crystal display device is characterized by comprising:

a pair of substrates; and

a liquid crystal layer provided between the pair of substrates;

at least one of the pair of substrates comprises a retardation layer comprising a polymer containing at least 1 monomer,

the at least 1 kind of monomer includes a photo-alignment monomer exhibiting alignment by polarized light.

2. The liquid crystal display device according to claim 1, wherein:

the photo-alignment monomer is represented by the following formula (I),

[ solution 1]

In the formula (I), P¹And P²The same or different, represents an acryloyloxy group, a methacryloyloxy group, an acrylamido group, a methacrylamido group, a vinyl group, or a vinyloxy group; sp¹And Sp²The same or different compounds represent straight chain, branched or cyclic alkylene groups having 1 to 6 carbon atoms, straight chain, branched or cyclic alkyleneoxy groups having 1 to 6 carbon atoms, straight chain, branched or cyclic alkyleneamino groups having 1 to 6 carbon atoms, or direct bonds.

3. The liquid crystal display device according to claim 1 or 2, wherein:

the photo-alignment monomer includes at least one amide group and/or amino group.

4. The liquid crystal display device according to any one of claims 1 to 3, wherein:

the photo-alignment monomer is represented by the following formula (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), (I-8), (I-9), (I-10), (I-11) or (I-12).

[ solution 2]

[ solution 3]

5. The liquid crystal display device according to any one of claims 1 to 4, wherein:

the liquid crystal display device further includes a photo alignment film between at least one of the pair of substrates and the liquid crystal layer, the photo alignment film controlling alignment of liquid crystal molecules in the liquid crystal layer.

6. The liquid crystal display device according to claim 5, wherein: the photo-alignment film has a structure derived from a four-membered ring.

7. The liquid crystal display device according to claim 5, wherein: the photo-alignment film has a cinnamate group.

8. A method of manufacturing a liquid crystal display device having a substrate including a retardation layer and a liquid crystal layer, the method comprising the steps of,

the manufacturing method of the liquid crystal display device comprises the following steps:

a step of forming a film containing at least 1 kind of monomer, wherein the monomer contains a photo-alignment monomer represented by the following formula (I); and

a step of irradiating the film with polarized light to orient and polymerize the monomer to form the phase difference layer,

[ solution 4]

In the formula (I), P¹And P²The same or different, represents an acryloyloxy group, a methacryloyloxy group, an acrylamido group, a methacrylamido group, a vinyl group, or a vinyloxy group; sp¹And Sp²The same or different, represent straight chain or branched chain of 1-6 carbon atomsA branched or cyclic alkylene group, a linear, branched or cyclic alkyleneoxy group having 1 to 6 carbon atoms, a linear, branched or cyclic alkyleneamino group having 1 to 6 carbon atoms, or a direct bond.

9. The method of manufacturing a liquid crystal display device according to claim 8, further comprising the steps of: rubbing a surface of the phase difference layer to exhibit a step of an alignment regulating force for liquid crystal molecules in the liquid crystal layer.

10. The method for manufacturing a liquid crystal display device according to claim 8, comprising the steps of:

a step of forming a polymer film having a cinnamate group on the retardation layer; and

irradiating the polymer film with polarized light to exhibit a step of alignment regulating force for liquid crystal molecules in the liquid crystal layer.

11. The method for manufacturing a liquid crystal display device according to claim 8, comprising the steps of:

a step of forming a polymer film having a four-membered ring on the retardation layer; and

irradiating the polymer film with polarized light to exhibit a step of alignment regulating force for liquid crystal molecules in the liquid crystal layer.

Technical Field

The present invention relates to a liquid crystal display device and a method of manufacturing the liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device having a retardation layer provided in a liquid crystal panel, and a method for manufacturing the liquid crystal display device.

Background

In recent years, a technique of forming a retardation layer in a liquid crystal panel has been studied, and a method of forming a retardation layer by polymerizing a reactive monomer in a state where Alignment is achieved by an Alignment layer (Alignment layer), for example, is known. Regarding this method, patent document 1 discloses a composition for a photo-alignment film containing a polymer obtained by polymerizing a compound having 2 or more azide groups and a compound having 2 or more (meth) acryl groups, and an organic solvent.

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have studied a technique for forming a retardation layer in a liquid crystal panel in order to clearly recognize a display even under external light (bright place). Fig. 4 is a schematic cross-sectional view showing an example of a structure of a liquid crystal panel in which a retardation layer is formed by a conventional method using an alignment layer. As shown in fig. 4, in the liquid crystal display device having a retardation layer formed in a liquid crystal panel by a conventional alignment layer method, a first linear polarizing plate 11, a transparent substrate 21, a color filter/black matrix 22, an alignment layer 101, an in-cell retardation layer 102, an alignment film 103, a liquid crystal layer 30, an alignment film 41, a Thin Film Transistor (TFT) substrate 42, and a second linear polarizing plate 51 are provided in this order from the viewing surface side to the back surface side.

The in-line retardation layer 102 shown in fig. 4 is formed by the method shown in fig. 5. A method of forming the in-line retardation layer 102 using the alignment layer 101 is illustrated in fig. 5. First, as shown in fig. 5(a), the alignment layer 101 formed on the color filter/black matrix 22 is subjected to alignment treatment by rubbing or light irradiation. The alignment layer 101 is usually made of polyimide (polyamic acid) or the like. Then, as shown in fig. 5(b), a solution containing a reactive monomer is applied on the alignment layer 101 to form a film 102a containing a reactive monomer. Finally, the film 102a is heated to polymerize the reactive monomer, thereby hardening the film 102a, and obtaining the in-cell retardation layer 102 shown in fig. 5 (c).

As a result of the studies by the present inventors, it was found that when the in-cell retardation layer 102 is formed using the alignment layer 101 as described above, the alignment property of the reactive monomer is relatively low, and the thermal stability may be lowered and scattering may occur, for the following reasons.

(1) Since the conventional reactive monomer is aligned by the alignment treatment of the alignment layer 101, the reactive monomer itself cannot induce alignment.

(2) The alignment layer 101 is formed only on one side of the film containing the reactive monomer, and therefore, the alignment regulating force of the alignment layer 101 is not sufficient, and if the film 102a containing the reactive monomer is formed to have a thickness of about 1mm, the alignment property of the reactive monomer is low and the randomness is high.

(3) If the reactive monomer has low orientation and high randomness, thermal stability is reduced. That is, the energy for causing the alignment to be random by heat may exceed the energy for stabilizing the alignment, and thus the alignment of the reactive monomer may be further degraded. Therefore, the retardation (retardation) of the in-cell retardation layer 102 obtained by polymerization of the reactive monomer is likely to be decreased by sintering at the time of formation of the alignment film or to be changed (decreased) by long-term use.

(4) The decrease in the alignment property of the reactive monomer makes the in-cell retardation layer 102 more likely to scatter, thereby decreasing the contrast of the liquid crystal display device.

When the alignment layer 101 is subjected to alignment treatment by rubbing, the reactive monomer has a pretilt angle of at least about 1 °, and thus the retardation of the in-cell retardation layer 102 cannot be sufficiently obtained or viewing angle dependence of the retardation occurs in some cases.

On the other hand, when the alignment layer 101 is subjected to alignment treatment by light irradiation, the alignment regulating force for the in-cell retardation layer 102 is weak, and the alignment property and the phase difference of the in-cell retardation layer 102 deteriorate with time, and therefore, the function of the in-cell retardation layer 102 may become insufficient if the in-cell retardation layer is used for a long period of time.

The present invention has been made in view of the above-described situation, and an object thereof is to provide a liquid crystal display device which has excellent stability of retardation against heat and can prevent a decrease in contrast due to scattering even when a retardation layer is formed by polymerizing a reactive monomer, and a method for manufacturing the liquid crystal display device which is suitable for manufacturing the liquid crystal display device.

Means for solving the problems

The present inventors have conducted various studies on a technique for forming a retardation layer in a liquid crystal panel, and as a result, have found that when a conventional cured product of a reactive monomer is used, the stability of the retardation with respect to heat is insufficient, and the contrast is lowered by scattering. It has been found that the use of a photo-alignment monomer exhibiting alignment by polarized light can improve the alignment of the reactive monomer. Thus, the present invention has been completed by considering that the above-described problems can be solved well.

That is, one aspect of the present invention is a liquid crystal display device including a pair of substrates, at least one of the pair of substrates including a retardation layer containing a polymer of at least 1 kind of monomer, and a liquid crystal layer provided between the pair of substrates, wherein the at least 1 kind of monomer includes a photo-alignment monomer exhibiting alignment by polarized light.

Another aspect of the present invention is a method for manufacturing a liquid crystal display device including a substrate including a retardation layer and a liquid crystal layer, including the steps of: forming a film containing at least 1 kind of monomer, wherein the monomer contains a photo-alignment monomer represented by the following formula (I); and irradiating the film with polarized light to orient and polymerize the monomer to form the retardation layer.

[ solution 1]

In the formula (I), P¹And P²The same or different, represents an acryloyloxy group, a methacryloyloxy group, an acrylamido group, a methacrylamido group, a vinyl group, or a vinyloxy group. Sp¹And Sp²The same or different, the alkylene groups are linear, branched or cyclic alkylene groups having 1 to 6 carbon atoms, linear, branched or cyclic alkyleneoxy groups having 1 to 6 carbon atoms, linear, branched or cyclic alkyleneamino groups having 1 to 6 carbon atoms, or directly bonded.

Effects of the invention

According to the present invention, a liquid crystal display device can be realized which has excellent stability of retardation against heat and can prevent a decrease in contrast due to scattering even when a retardation layer is formed by polymerizing a reactive monomer.

Drawings

Fig. 1 is a schematic cross-sectional view showing the structure of a liquid crystal display device of embodiment 1.

Fig. 2 is a diagram illustrating a method of forming the in-cell retardation layer 23 using the photo-alignment monomer.

Fig. 3 is a schematic cross-sectional view showing the structure of a liquid crystal display device of embodiment 2.

Fig. 4 is a schematic cross-sectional view showing an example of a structure of a liquid crystal panel in which a retardation layer is formed by a conventional method using an alignment layer.

Fig. 5 is a diagram illustrating a method of forming the in-cell retardation layer 102 using the alignment layer 101.

Detailed Description

Embodiments will be disclosed below, and the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The configurations of the respective embodiments may be appropriately combined and modified without departing from the spirit and scope of the present invention.

In the present specification, the "observation surface side" refers to a side closer to the screen (display surface) of the display device, and the "back surface side" refers to a side farther from the screen (display surface) of the display device.

In the present specification, the "retardation layer" refers to a retardation layer which imparts an in-plane retardation of 10nm or more to light having a wavelength of at least 550 nm. Thus, light having a wavelength of 550nm is light having the highest human visibility. The in-plane retardation is defined as R ═ (ns-nf) × d. Here, ns represents the larger one of the principal refractive indices nx and ny in the in-plane direction of the retardation layer, and nf represents the smaller one of the principal refractive indices nx and ny in the in-plane direction of the retardation layer. The main refractive index is a value with respect to light having a wavelength of 550nm unless otherwise specified. The in-plane slow axis of the retardation layer is a shaft in the direction corresponding to ns, and the in-plane slow axis is an axis in the direction corresponding to nf. d represents the thickness of the phase difference layer. In the present specification, unless otherwise specified, "retardation (retardation)" means an in-plane retardation with respect to light having a wavelength of 550 nm.

In the present specification, the retardation layer disposed on the back surface side of the transparent base material on the observation surface side of the liquid crystal panel is referred to as an "in-cell retardation layer".

< embodiment 1 >

Fig. 1 is a schematic cross-sectional view showing the structure of a liquid crystal display device of embodiment 1. As shown in fig. 1, the liquid crystal display device of embodiment 1 includes, in order from the viewing surface side to the back surface side, a first linear polarizer 11, a Color Filter (CF) substrate 20, a liquid crystal layer 30, an alignment film 41, a Thin Film Transistor (TFT) substrate 42, a second linear polarizer 51, and a backlight 60.

As the first linear polarizer 11, for example, a polarizing element (absorption-type polarizer) obtained by dyeing a polyvinyl alcohol (PVA) film with an anisotropic material such as an iodine complex (or dye) and adsorbing the anisotropic material and extending the film in an orientation can be used. In addition, in general, protective films such as triacetyl cellulose (TAC) films are stacked on both sides of a PVA film to ensure mechanical strength and moist heat resistance, and are put into practical use.

The CF substrate 20 includes a transparent base material 21, a color filter/black matrix 22, and an in-cell retardation layer 23 in this order from the viewing surface side to the back surface side.

Examples of the transparent substrate 21 include a glass substrate and a plastic substrate.

The color filter/black matrix 22 is configured such that a red color filter, a green color filter, and a blue color filter are arranged in a plane and partitioned by a black matrix. The red color filter, the green color filter, the blue color filter, and the black matrix are made of, for example, a transparent resin containing a pigment. In general, a combination of a red color filter, a green color filter, and a blue color filter is disposed in all pixels, and the amounts of color lights transmitted through the red color filter, the green color filter, and the blue color filter are controlled to mix colors, thereby obtaining a desired color in each pixel.

The in-cell retardation layer 23 contains a polymer of at least 1 monomer. As the monomer to be used as a material of the polymer, a Reactive monomer having a Mesogen site in the molecule, i.e., a Reactive Mesogen (RM) monomer is preferably used. At least 1 kind of monomers among monomers to be a material of the polymer is a photo-alignment monomer exhibiting alignment by polarized light. The photo-alignment monomers can be aligned in accordance with the direction of polarized light, and are uniformly aligned in the thickness direction of the in-cell retardation layer 23 regardless of the thickness of the in-cell retardation layer 23. Therefore, as compared with the case where the alignment layer is provided only on one side of the retardation layer and the alignment is controlled as in the conventional technique, the alignment property of the entire retardation layer in the layer can be improved. This improves the stability of the phase difference, and specifically, the phase difference is less likely to change even after long-term use, and the stability of the phase difference with respect to heat is improved. Further, since the entire retardation layer has a high orientation, the contrast is prevented from being lowered by scattering.

The photo-alignment monomer is preferably a radical polymerizable monomer having a photoreactive group, and the photoreactive group is more preferably a radical polymerizable monomer having a chalcone group. As the radical polymerizable monomer having a chalcone group, a monomer represented by the following formula (I) is preferable.

[ solution 2]

In the formula (I), the compound has the following structure,P¹and P²The same or different, represents an acryloyloxy group, a methacryloyloxy group, an acrylamido group, a methacrylamido group, a vinyl group, or a vinyloxy group. Sp¹And Sp²The same or different compounds represent straight chain, branched or cyclic alkylene groups having 1 to 6 carbon atoms, straight chain, branched or cyclic alkyleneoxy groups having 1 to 6 carbon atoms, straight chain, branched or cyclic alkyleneamino groups having 1 to 6 carbon atoms, or direct bonds.

The photo-alignment monomer preferably contains at least one amide group (-NH-) and/or amino group (-CONH-). Since the monomer has an amino group and/or an amide group in its molecule, hydrogen bonds are induced between molecules, and thus thermal stability is improved. An example of the intermolecular hydrogen bond is shown in the following formula.

[ solution 3]

As specific examples of the monomer having at least one amide group and/or amino group among the monomers represented by the above formula (I), monomers represented by, for example, the following formulae (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), (I-8), (I-9), (I-10), (I-11) or (I-12) are suitably used.

[ solution 4]

[ solution 5]

As another specific example of the monomer represented by the above formula (I), there may be mentioned, for example, a monomer represented by the following formula (I-13), (I-14), (I-15), (I-16) or (I-17).

[ solution 6]

The retardation (retardation) of the in-cell retardation layer 23 is determined by the product of the birefringence Δ n of the polymer constituting the in-cell retardation layer 23 and the thickness d of the in-cell retardation layer 23. The retardation of the in-cell retardation layer 23 is not particularly limited, but the in-cell retardation layer 23 is preferably of a type (λ/4 plate) which imparts an in-plane retardation of 1/4 wavelengths to light having a wavelength of 550nm, and specifically, imparts an in-plane retardation of 100nm or more and 176nm or less to light having a wavelength of at least 550 nm. The combination of the first linear polarizing plate 11 and the λ/4 plate functions as a circular polarizing plate. This can reduce the internal reflection of the liquid crystal panel, and thus can realize favorable black display in which the reflection (reflection) of external light is suppressed, and the visibility of a display image is greatly improved particularly when the liquid crystal panel is used outdoors.

Fig. 2 is a diagram illustrating a method of forming the in-cell retardation layer 23 using the photo-alignment monomer. As shown in fig. 2(a), after a film 23a containing a photo-alignment monomer is formed on a color filter/black matrix 22, the film 23a is heated to a nematic phase-isotropic phase transition temperature T of the photo-alignment monomer_NIIn this way, the film 23a is irradiated with polarized light UV. This enables the photo-alignment monomer in the film 23a to be polymerized while being aligned. Thereby, the film 23a is cured, and as shown in fig. 2(b), the in-cell retardation layer 23 is obtained. If necessary, the film 23a may be heated after irradiation with polarized light UV in order to remove the solvent or complete polymerization of the photo-alignment monomer.

Examples of the solvent used for coating the photo-alignment monomer include toluene, ethylbenzene, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, dibutyl ether, acetone, methyl ethyl ketone, ethanol, propanol, cyclohexane, cyclopentanone, methylcyclohexane, tetrahydrofuran, dioxane, cyclohexanone, N-hexane, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate (PEGMEA), methoxybutyl acetate, N-methylpyrrolidone, and dimethylacetamide. Any one of them may be used alone, or two or more of them may be used in combination.

Further, after the in-cell retardation layer 23 is formed by irradiating the photo-alignment monomer with polarized light UV, the surface of the in-cell retardation layer 23 is directly rubbed, thereby exhibiting alignment regulating force for the liquid crystal molecules of the liquid crystal layer 30. Since the in-cell retardation layer 23 is uniformly aligned not only on the surface but also on the entire surface by irradiation of polarized light UV, even when the surface of the in-cell retardation layer 23 is rubbed with rubbing cloth, retardation is not lowered due to alignment disorder of the in-cell retardation layer 23. The rubbing direction for inducing alignment of the liquid crystal layer 30 is preferably 45 ° to the slow axis of the in-cell retardation layer 23.

The liquid crystal material contained in the liquid crystal layer 30 is not particularly limited, and for example, a liquid crystal material that is horizontally aligned when no voltage is applied can be used. The liquid crystal molecules in the liquid crystal layer 30 are horizontally aligned in a predetermined azimuth by a confining force of the embedded retardation layer 23 and the alignment film 41 in a state where no voltage is applied to the electrodes provided on the TFT substrate 42 (when no voltage is applied), and are rotated in an in-plane direction by a lateral electric field generated in the liquid crystal layer 30 in a state where a voltage is applied to the electrodes (when a voltage is applied).

As the alignment film 41, an alignment film commonly used in the field of liquid crystal display panels of polyimide or the like can be used. Rubbing, light irradiation, or the like can be used for the alignment treatment of the alignment film 41.

The Thin Film Transistor (TFT) substrate 42 may use an active matrix substrate commonly used in the field of liquid crystal display panels. When the liquid crystal driving mode of the liquid crystal display device of the present embodiment is an FFS (Fringe Field Switching) mode, the TFT substrate 42 includes, for example, a support substrate, a common electrode (planar electrode) disposed on a surface of the support substrate on the liquid crystal layer 30 side, an insulating film covering the common electrode, and a pixel electrode (comb-teeth electrode) disposed on a surface of the insulating film on the liquid crystal layer 30 side. With this configuration, a lateral electric field (fringe electric field) can be generated in the liquid crystal layer 30 by applying a voltage between the common electrode and the pixel electrode which constitute the pair of electrodes. Accordingly, by adjusting the voltage applied between the common electrode and the pixel electrode, the alignment of the liquid crystal in the liquid crystal layer 30 can be suppressed. Further, when the liquid crystal driving mode of the liquid crystal display device of the present embodiment is an IPS (In-Plane-Switching) mode, a voltage is applied to a pair of comb-teeth electrodes provided on the TFT substrate 42, whereby a lateral electric field is generated In the liquid crystal layer 30, and the alignment of liquid crystals In the liquid crystal layer 30 is controlled.

The second linear polarizer 51 may be the same as the first linear polarizer 11. The transmission axis of the first linear polarizing plate 11 and the transmission axis of the second linear polarizing plate 51 are preferably orthogonal to each other. According to this structure, the first linear polarizing plate 11 and the second linear polarizing plate 51 are arranged in a crossed nicols manner, and thus, a good black display state can be realized when no voltage is applied. In the present specification, the term "2 axes (directions) orthogonal to each other" means that the angle (absolute value) formed by the two axes is in the range of 90 ± 3 °, preferably in the range of 90 ± 1 °, more preferably in the range of 90 ± 0.5 °, and particularly preferably in the range of 90 ° (complete orthogonal).

The backlight 60 is not particularly limited, and may be of an edge-lit type or a direct-lit type. The type of light source of the backlight 60 is not particularly limited, and examples thereof include a Light Emitting Diode (LED), a Cold Cathode Fluorescent Lamp (CCFL), and the like. The amount of light transmitted through the liquid crystal panel is controlled by the voltage applied to the liquid crystal layer 30 provided in the liquid crystal display panel, with respect to the light emitted from the backlight 60.

The liquid crystal display device of embodiment 1 may include other components, and for example, the reflectance of the liquid crystal panel may be further reduced by providing an antireflection film on the viewing surface side of the first linear polarizing plate 11. As the antireflection film, a moth-eye film having a moth-eye-shaped surface structure is suitably used.

As described above, in embodiment 1, since the RM monomer constituting the in-cell retardation layer 23 induces the alignment, the entire in-cell retardation layer 23 is aligned. As the RM monomer having such a function, a monomer having a chalcone group represented by the above formula (I) is suitably used. Since the chalcone group exhibits alignment properties by absorbing polarized UV light, it is not necessary to form an alignment layer for aligning the RM monomer. Since the in-cell retardation layer 23 is entirely oriented, the orientation stability with respect to heat is improved, and the deterioration of the orientation, that is, the retardation, due to heat is suppressed. Further, since the in-cell retardation layer 23 is excellent in the alignment of the mesogen portion, the decrease in contrast due to scattering can be suppressed.

< embodiment 2 >

Fig. 3 is a schematic cross-sectional view showing the structure of a liquid crystal display device of embodiment 2. As shown in fig. 3, the liquid crystal display device of embodiment 2 includes, in order from the viewing surface side to the back surface side, a first linear polarizer 11, a Color Filter (CF) substrate 20, a liquid crystal layer 30, an alignment film 41, a Thin Film Transistor (TFT) substrate 42, a second linear polarizer 51, and a backlight 60.

The CF substrate 20 includes a transparent base material 21, a color filter/black matrix 22, an in-cell retardation layer 23, and a photo-alignment film 24 in this order from the viewing surface side to the back surface side. In the present embodiment, the optical alignment film 24 is provided on the liquid crystal layer 30 side of the embedded retardation layer 23, and the alignment property of the liquid crystal layer 30 can be improved. This improves the contrast of the liquid crystal display device.

The photo-alignment film 24 is not particularly limited as long as it can control alignment of liquid crystal molecules in the liquid crystal layer 30 by light irradiation, and is formed of a material exhibiting photo-alignment properties. The material exhibiting photo-alignment properties is a material exhibiting properties (alignment regulating force) of regulating the alignment of liquid crystal molecules in the vicinity thereof by changing the structure by irradiation with light (electromagnetic wave) such as ultraviolet light or visible light, or any material in which the magnitude and/or direction of the alignment regulating force is changed.

Examples of the material exhibiting photo-alignment properties include materials containing a photoreactive site (photo-functional group) that causes reactions such as dimerization (dimerization), isomerization, photo-fries rearrangement, and decomposition by light irradiation. Examples of the photoreactive site that undergoes dimerization and isomerization by light irradiation include cinnamate, chalcone, coumarin, and stilbene. The photoreactive site that is isomerized by light irradiation may be, for example, azobenzene. The photoreactive site on which the photo-fries rearrangement occurs by light irradiation includes, for example, a phenol ester structure. Examples of the photoreactive site (photolytic functional group) that is decomposed by light irradiation include a four-membered ring.

When the in-cell type phase difference layer 23 is formed using a monomer having a chalcone group, the photo alignment film 24 is preferably formed using an alignment film material having a photodegradable functional group or a cinnamate group. Since the light absorption of the chalcone group has 365nm as the center wavelength, the center wavelength of the light absorption of the photodegradable functional group is 250nm, and the center wavelength of the light absorption of the cinnamate group is 310nm, the wavelength of the light used for the alignment treatment of the photo-alignment film 24 can be prevented from overlapping the light absorption wavelength of the RM monomer of the in-cell retardation layer 23 when the alignment film material having the photodegradable functional group or the cinnamate group is used.

Specific examples of the method for forming the photo-alignment film 24 using an alignment film material having a four-membered ring include the following methods: after a polymer film having a four-membered ring is formed on the embedded retardation layer 23, the polymer film is irradiated with polarized light to exhibit an alignment regulating force for liquid crystal molecules in the liquid crystal layer 30.

As a specific method for forming the photo-alignment film 24 using an alignment film material having a cinnamate group, the following method may be mentioned: after a polymer film having a cinnamate group is formed on the in-type retardation layer 23, the polymer film is irradiated with polarized light, and a force of alignment regulation of liquid crystal molecules in the liquid crystal layer 30 is exhibited.

In embodiments 1 and 2, the in-cell retardation layer 23 formed using the photo-alignment monomer is formed only on the CF substrate 20, but in the present invention, the substrate provided with the retardation layer formed using the photo-alignment monomer is not particularly limited, and may be provided on the TFT substrate 42, or may be provided on both the CF substrate 20 and the TFT substrate 42.

Hereinafter, examples and comparative examples will be disclosed to explain the present invention in more detail, but the present invention is not limited to these examples.

< example 1 >