阅读说明：本技术 光学膜 (Optical film ) 是由 村重毅 稻垣淳一 佐藤启介 岸敦史 于 2020-03-26 设计创作，主要内容包括：本发明提供尽管具备具有凹部或贯穿孔的偏振片,但处理性优异、偏振片的应变得到抑制、并且由环境变化引起的尺寸变化小的光学膜。本发明的光学膜依次具备玻璃膜、偏振片及粘合剂层,该偏振片具有凹部或贯穿孔,所述凹部在该偏振片的与该玻璃膜相反侧的一面开口,该粘合剂层的一部分填埋该凹部或该贯穿孔,该玻璃膜的厚度为30μm～150μm。(The invention provides an optical film which has excellent handling property, can restrain the strain of a polaroid and has small dimension change caused by environmental change, even though the optical film is provided with a polaroid with a concave part or a through hole. The optical film of the present invention comprises a glass film, a polarizing plate having a recess or a through-hole, the recess being open on one surface of the polarizing plate on the side opposite to the glass film, and an adhesive layer in this order, wherein a part of the adhesive layer fills the recess or the through-hole, and the glass film has a thickness of 30 to 150 μm.)

1. An optical film comprising a glass film, a polarizing plate and an adhesive layer in this order,

the polarizing plate has a recess or a through-hole, the recess being open on one surface of the polarizing plate on the side opposite to the glass film,

a portion of the adhesive layer fills the recess or the through-hole,

the thickness of the glass film is 30 to 150 μm.

2. The optical film according to claim 1, further comprising an adhesive layer disposed between the glass film and the polarizing plate.

3. The optical film according to claim 2,

the adhesive layer has a thickness of 10 [ mu ] m or less.

4. The optical film according to any one of claims 1 to 3,

the polarizer comprises a polarizer and a polarizer,

the area of the recess or the through hole on the glass film side of the polarizer in plan view is 0.310^-6m²～20×10^-4m²。

Technical Field

The present invention relates to an optical film.

Background

A camera is sometimes mounted in an image display device such as a notebook Personal Computer (PC) or a mobile device. In such an image display device, since a configuration having no height difference in the outermost layer is required from the viewpoint of design, a polarizing plate may be disposed on the visible side of a camera incorporated therein. In such a case, there is a problem that the polarizing plate absorbs light and sufficient light cannot reach the camera. In order to solve this problem, a technique has been studied in which a portion of the polarizing plate is removed in the thickness direction at a position corresponding to the camera, and an optical adhesive is filled in a recess (removed portion) that is generated (for example, patent document 1). However, the formation of the removed portion causes process problems such as a reduction in the rigidity of the polarizing plate and cracking during handling, and also causes a problem that local deformation occurs in an environment where temperature changes after mounting, resulting in a reduction in the quality of an image.

Documents of the prior art

Patent document

Patent document 1: U.S. Pat. No. 9075199 publication

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above problems, and a main object thereof is to provide an optical film which has excellent handling properties, suppresses strain in a polarizing plate, and has little dimensional change due to environmental changes, despite having a polarizing plate with a concave portion or a through-hole.

Means for solving the problems

The optical film of the present invention includes a glass film, a polarizing plate having a recess or a through-hole, the recess having an opening on one surface of the polarizing plate on the side opposite to the glass film, and an adhesive layer in this order, and the glass film has a thickness of 30 to 150 μm, wherein the recess or the through-hole is partially filled with the adhesive layer.

In one embodiment, the optical film further includes an adhesive layer disposed between the glass film and the polarizing plate.

In one embodiment, the adhesive layer has a thickness of 10 μm or less.

In one embodiment, the polarizing plate includes a polarizer, and the area of the concave portion or the through-hole on the surface of the polarizer on the glass film side in a plan view is 0.3 × 10^-6m²～20×10^-4m²。

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an optical film having excellent handleability and small dimensional change due to environmental change can be provided despite having a polarizing plate with a recess or a through-hole.

Drawings

Fig. 1(a) is a schematic plan view of an optical film according to an embodiment of the present invention, and fig. 1(b) is an i-i sectional view of the optical film shown in fig. 1 (a).

Fig. 2(a) is a schematic top view of an optical film according to another embodiment of the present invention, and fig. 2(b) is a sectional view ii-ii of the optical film shown in fig. 2 (a).

Description of the symbols

10 glass film

20 polarizing plate

30 adhesive layer

40 adhesive layer

100. 100' optical film

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Outline of optical film

Fig. 1(a) is a schematic plan view of an optical film according to an embodiment of the present invention, and fig. 1(b) is an i-i sectional view of the optical film shown in fig. 1 (a). The optical film 100 includes a glass film 10, a polarizing plate 20, and a pressure-sensitive adhesive layer 30 in this order. The polarizing plate 20 has a recess 21 that is open on the surface opposite to the glass film 10 (the lower surface of the polarizing plate). A part of the adhesive layer 30 fills the recess 21. More specifically, the pressure-sensitive adhesive layer 30 is formed so as to be able to attach the optical film 100 to any appropriate adherend (for example, a liquid crystal cell), and fills the concave portion 21. In the present specification, for convenience, the glass film side of the optical film is defined as the upper side and the pressure-sensitive adhesive layer side is defined as the lower side. In one embodiment, when the optical film is applied to an image display device, the upper side of the optical film may correspond to the visible side of the image display device.

Fig. 2(a) is a schematic top view of an optical film according to an embodiment of the present invention, and fig. 2(b) is a sectional view of the optical film shown in fig. 2(a) taken along ii-ii. The optical film 100' includes a glass film 10, a polarizing plate 20, and a pressure-sensitive adhesive layer 30 in this order. The polarizing plate 20 has a through-hole 22. A portion of the adhesive layer 30 fills the through-hole 22. More specifically, the adhesive layer 30 is formed so as to be able to attach the optical film 100' to any appropriate adherend (for example, a liquid crystal cell), and fills the through-hole 22.

The optical film of the present invention can be suitably used for an image display device with a camera. The optical film of the present invention can function as a polarizing plate on the viewing side of an image display device, and can be disposed on the viewing side of a predetermined member (for example, a liquid crystal cell) so that the glass film is the viewing side. In the image display device with a camera, the optical film is disposed so that the position of the camera corresponds to the position of the recess or the through-hole. In one embodiment, the optical film of the present invention can be used for an image display device having a touch sensor. The image display device may include a liquid crystal cell including a substrate on which the touch sensor is mounted. In the optical film of the present invention, the polarizing plate is formed with a recess or a through-hole, and the recess or the through-hole is filled with the pressure-sensitive adhesive layer, and therefore, the optical film can be disposed on the visible side of the camera without preventing light from reaching the camera. Further, in the present invention, although the polarizing plate having a concave portion or a through hole and thus having insufficient rigidity as such is provided, by providing the glass film, it is possible to prevent the occurrence of cracking or the like in the polarizing plate, and to obtain an optical film which is excellent in handling property, in which strain of the polarizing plate is suppressed, in which dimensional change due to environmental change (for example, temperature change) is small, and in which local deformation is not easily caused. The optical film can be applied to a roll-to-roll process, can prevent occurrence of defects, is excellent in production efficiency, and can provide an image display device with a camera and the like excellent in image pickup quality when used.

In one embodiment, the glass film 10 and the polarizing plate 20 are laminated via an adhesive layer 40.

The optical film may further comprise any suitable additional layer. For example, the optical film may further include optical functional layers such as a retardation layer, an antireflection layer, an antiglare layer, and a brightness enhancement film; an antifouling layer; hard coatings, and the like. When another layer (for example, a retardation layer) is disposed between the polarizing plate and the pressure-sensitive adhesive layer, the recess or the through-hole is preferably formed in a portion of the laminate of the other layer and the polarizing plate, and the pressure-sensitive adhesive layer preferably fills the recess or the through-hole.

In one embodiment, the above optical film may be provided in a long shape.

B. Glass film

Any suitable glass film may be used as the glass film. The glass film may be, for example, soda lime glass, boric acid glass, aluminosilicate glass, quartz glass, or the like, depending on the composition. When the glass is classified according to the alkali component, alkali-free glass and low-alkali glass are exemplified. Alkali metal component (e.g., Na) of the above glass₂O、K₂O、Li₂O) is preferably 15 wt% or less, more preferably 10 wt% or less.

The thickness of the glass film is 30 to 150. mu.m, more preferably 50 to 140. mu.m, still more preferably 70 to 130. mu.m, and particularly preferably 80 to 120. mu.m. In such a range, occurrence of cracks or the like can be prevented, and an optical film which is excellent in handling property, in which strain of a polarizing plate is suppressed, in which dimensional change due to environmental change (for example, temperature change) is small, and in which local deformation is less likely to occur can be obtained. Further, an optical film which is excellent in flexibility, can be processed by a roll-to-roll process, is less likely to break and is excellent in productivity can be obtained.

The glass film preferably has a light transmittance of 85% or more at a wavelength of 550 nm. The refractive index of the glass film at a wavelength of 550nm is preferably 1.4 to 1.65.

The density of the glass film is preferably 2.3g/cm³～3.0g/cm³More preferably 2.3g/cm³～2.7g/cm³. In such a range, an optical film with reduced strain and dimensional change of the polarizing plate can be obtained. If a glass film having a density in the above range is used, an optical film contributing to weight reduction of image display can be provided.

Any suitable method can be used for the method for forming the glass film. Typically, the glass film can be produced as follows: a mixture containing a main raw material such as silica or alumina, a defoaming agent such as mirabilite or antimony oxide, and a reducing agent such as carbon is melted at a temperature of 1400 to 1600 ℃, formed into a thin plate, and then cooled. Examples of the method for forming the glass film include: flow-hole down-draw, fusion, float, etc. In order to make the glass film formed into a plate shape by these methods thin or improve smoothness, chemical polishing using a solvent such as hydrofluoric acid may be performed as necessary.

C. Polarizing plate

The polarizing plate has a polarizer. Typically, as shown in fig. 1(b) and 2(b), the polarizing plate 20 further includes protective films 24a and 24b disposed on at least one side of the polarizer 23.

As described above, the polarizing plate has a recess or a through-hole.

The concave portion is preferably formed so as to penetrate the polarizer. The thickness of the concave portion (thickness T in fig. 1) based on the upper surface (surface on the glass film side) of the polarizer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and still more preferably 1 μm or more. The thickness of the concave portion (thickness T in fig. 1) based on the upper surface (surface on the glass film side) of the polarizer is preferably 1% to 99%, more preferably 5% to 95%, of the thickness (thickness X in fig. 1) from the upper surface (surface on the glass film side) of the polarizer to the upper surface of the polarizing plate. When the thickness T is within the above range, an optical film which is less likely to prevent light from reaching the camera can be obtained.

The recess may be formed in any suitable shape. Examples of the cross-sectional shape of the recess include: rectangular, trapezoidal, triangular, etc. As a plan view shape of the recess viewed from the opening portion side (lower side of the polarizing plate), for example: circular, oval, square, rectangular, polygonal, etc. As a planar shape of the concave portion viewed from the side opposite to the opening (upper side of the polarizing plate), for example: circular, oval, square, rectangular, polygonal, etc. The through-hole may have a prismatic or cylindrical shape, for example. Alternatively, the columnar shape may be tapered.

The planar area of the recess and the through-hole may be set to an appropriate area according to the size of a camera provided in an image display device to which the optical film is applied. The planar area of the recess and the through-hole on the upper surface (surface on the glass film side) of the polarizer is preferably 0.3 × 10^-6m²～20×10^-4m²More preferably 0.7X 10^-6m²～10×10^-4m²More preferably 0.7X 10^-6m²～3×10^-4m²。

The recess and the through-hole may be formed by any suitable method. As a typical method for forming the concave portion and the through hole, a method of irradiating laser light is given. As the laser beam, any appropriate laser beam may be used as long as a recess or a through hole can be formed in the polarizing plate. Preferably, a laser beam capable of emitting light having a wavelength in the range of 150nm to 11 μm is used. Specific examples thereof include CO₂Gas lasers such as laser; solid laser such as YAG laser; a semiconductor laser. Preference is given to using CO₂And (4) laser.

The irradiation conditions of the laser beam can be set to any appropriate conditions according to the laser beam used, for example. In the use of CO₂In the case of the laser, the output condition is preferably 10W to 1000W, more preferably 100W to 400W.

The thickness of the polarizing plate (the thickness of the portion where no recess or through-hole is formed) is preferably 5 to 300 μm, more preferably 10 to 250 μm, still more preferably 25 to 200 μm, and particularly preferably 25 to 100 μm.

C-1 polarizer

The thickness of the polarizer is not particularly limited, and an appropriate thickness may be used according to the purpose. The thickness is typically about 1 μm to 80 μm. In one embodiment, a thin polarizer is used, and the thickness of the polarizer is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and particularly preferably 6 μm or less.

The polarizer preferably exhibits dichroism of absorption at any wavelength of 380nm to 780 nm. The monomer transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, and particularly preferably 43.0% or more. The degree of polarization of the polarizer is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

Preferably, the polarizer is an iodine polarizer. More specifically, the polarizer may be formed of a film of polyvinyl alcohol resin containing iodine (hereinafter referred to as "PVA-based resin").

As the PVA-based resin forming the PVA-based resin film, any suitable resin can be used. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K6726-. By using the PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained. When the saponification degree is too high, gelation may occur.

The average polymerization degree of the PVA-based resin may be appropriately selected depending on the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 5000, and more preferably 1500 to 4500. The average polymerization degree can be determined in accordance with JIS K6726-.

Examples of the method for producing the polarizer include: a method (I) of stretching and dyeing the PVA-based resin film monomer; and (II) a method of stretching and dyeing the laminate (i) having the resin base material and the polyvinyl alcohol resin layer. The method (I) is a conventional method well known in the art, and thus, a detailed description thereof will be omitted. The production method (II) preferably includes a step of stretching and dyeing a laminate (i) including a resin base and a polyvinyl alcohol resin layer formed on one side of the resin base to produce the polarizer on the resin base. The laminate (i) can be formed by applying a coating solution containing a polyvinyl alcohol resin on a resin substrate and drying the coating solution. The laminate (i) may be formed by transferring a polyvinyl alcohol resin film onto a resin substrate. The details of the above-mentioned production method (II) are described in, for example, Japanese patent laid-open No. 2012 and 73580, which are incorporated herein by reference.

C-2 protective film

As the protective film, any appropriate resin film can be used. Examples of the material for forming the protective film include: polyester resins such as polyethylene terephthalate (PET), cellulose resins such as Triacetylcellulose (TAC), cycloolefin resins such as norbornene resins, olefin resins such as polyethylene and polypropylene, and (meth) acrylic resins. Among them, polyethylene terephthalate (PET) is preferable. The term "(meth) acrylic resin" means an acrylic resin and/or a methacrylic resin.

In one embodiment, a (meth) acrylic resin having a glutarimide structure may be used as the (meth) acrylic resin. The (meth) acrylic resin having a glutarimide structure (hereinafter also referred to as a glutarimide resin) is described, for example, in: japanese patent application laid-open Nos. 2006-309033, 2006-317560, 2006-328329, 2006-328334, 2006-337491, 2006-337492, 2006-337493, 2006-337569, 2007-009182, 2009-161744 and 2010-284840. These descriptions are incorporated herein by reference.

The protective film and the polarizer are laminated via an arbitrary appropriate adhesive. The resin base material used for producing the polarizer may be peeled off before or after the protective film and the polarizer are laminated. The concave portion and the through-hole may be formed by the above-described method after the polarizing plate is formed by laminating the polarizer and the protective film.

The thickness of the protective film is preferably 4 to 250. mu.m, more preferably 5 to 150. mu.m, still more preferably 10 to 100. mu.m, and particularly preferably 10 to 50 μm.

D. Adhesive layer

The pressure-sensitive adhesive layer is formed of any appropriate light-transmitting pressure-sensitive adhesive. As the adhesive, for example, an adhesive containing a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber polymer as a base polymer can be used. Acrylic adhesives are preferably used. This is because: the acrylic pressure-sensitive adhesive is excellent in optical transparency, can exhibit adhesive properties such as appropriate wettability, cohesiveness and adhesiveness, and is excellent in weather resistance, heat resistance and the like. Particularly preferably an acrylic pressure-sensitive adhesive comprising an acrylic polymer having 4 to 12 carbon atoms.

As shown in fig. 1(b) and 2(b), the pressure-sensitive adhesive layer includes a bonding region 31 formed to be bonded to an adherend (for example, a liquid crystal cell), and a filling region 32 formed to fill the recess 21 or the through-hole 22 of the polarizing plate 20 (or a laminated portion formed of the polarizing plate and another layer). The thickness of the bonding region 31 (thickness Y in FIG. 1) is preferably 1 to 100. mu.m, more preferably 3 to 80 μm, and still more preferably 3 to 50 μm. In such a range, an optical film having excellent flexibility can be obtained.

Preferably, 80% by volume or more, more preferably 90% by volume or more, particularly preferably 99% by volume or more, and even more preferably 100% by volume of the recesses or through-holes of the polarizing plate (or the laminated portion formed of the polarizing plate and another layer) are filled with the adhesive layer. By filling the entire recess or through hole with the adhesive layer, the air layer can be eliminated, and unnecessary interface reflection can be prevented.

As a method for forming the pressure-sensitive adhesive layer, any appropriate method can be used. Specifically, there can be adopted: a method of applying and drying the adhesive on a polarizing plate (polarizing plate provided with the concave portion or the through-hole) so as to obtain a desired shape; and a method of separately forming an adhesive layer having a desired shape on a substrate (for example, a separator) and bonding the adhesive layer to a polarizing plate (a polarizing plate provided with the above-described concave portion or through-hole). Examples of the method for applying the adhesive include: roll coating methods such as reverse coating method and gravure coating method, spin coating method, screen coating method, curtain coating method, dipping method, and spraying method.

E. Adhesive layer

The adhesive layer is formed of any appropriate light-transmitting adhesive. Examples of the adhesive include a polyester adhesive, a polyurethane adhesive, a polyvinyl alcohol adhesive, and an epoxy adhesive. Among them, epoxy adhesives are preferable. This is because particularly good adhesion can be obtained.

When the adhesive is a thermosetting adhesive, the adhesive can be cured (solidified) by heating to exhibit peeling resistance. In the case of a photocurable adhesive such as an ultraviolet-curable adhesive, the adhesive can be cured by irradiation with light such as ultraviolet light, and thus exhibits peel resistance. In addition, when the adhesive is a moisture-curable adhesive, the adhesive can be cured by reaction with moisture in the air or the like, and therefore, the adhesive can be cured by merely leaving it to stand, and the peeling resistance can be exhibited.

The adhesive may be a commercially available adhesive, or may be prepared as an adhesive solution (or dispersion) by dissolving or dispersing various curable resins in a solvent.

The thickness of the adhesive layer is preferably 10 μm or less, more preferably 1 to 10 μm, still more preferably 1 to 8 μm, and particularly preferably 1 to 6 μm. In the case where the thickness is within such a range, the effect of suppressing the strain and dimensional change of the polarizing plate by disposing the glass film can be remarkably exhibited.

The elastic modulus of the adhesive layer is preferably 1GPa to 10GPa, more preferably 1GPa to 5GPa, and still more preferably 1.5GPa to 3 GPa. In the case where the thickness is within such a range, the effect of suppressing the strain and dimensional change of the polarizing plate by disposing the glass film can be remarkably exhibited. In addition, an optical film having excellent flexibility can be obtained. In the present specification, the elastic modulus can be measured using a universal tester (Autograph) under the following conditions.

< method for measuring elastic modulus >

Measuring temperature: 23 deg.C

Sample size: 2cm wide and 15cm long

The distance between the clamps: 10cm

Stretching speed: 10mm/min