WO2021124905A1

WO2021124905A1 - Composite polarization plate and liquid crystal display device

Info

Publication number: WO2021124905A1
Application number: PCT/JP2020/045007
Authority: WO
Inventors: 江端　範充
Original assignee: 住友化学株式会社
Priority date: 2019-12-18
Filing date: 2020-12-03
Publication date: 2021-06-24
Also published as: CN114829995B; JP2021096456A; JP7444721B2; CN114829995A; TW202130505A; KR20220116023A

Abstract

The objective of the present invention is to provide a composite polarization plate with which external appearance defects can be suppressed even in a high-temperature durability test, and a liquid crystal display device using the same. This composite polarization plate comprises a brightness improvement film and a polarization plate having a protective layer on at least one of the surfaces of a linear polarization layer. Layered on the protective layer side of the polarization plate are a first adhesive layer, a buffer layer, and the brightness improvement film, in this order. The tensile modulus of elasticity of the buffer layer, at a temperature of 23°C and a relative humidity of 55%, is 1.5 GPa or higher.

Description

Composite polarizing plate and liquid crystal display device

The present invention relates to a composite polarizing plate and a liquid crystal display device using the same.

Conventionally, it is known to improve the brightness of a liquid crystal display device by using a composite polarizing plate in which a polarizing plate and a brightness improving film are laminated (Patent Documents 1 to 5). Further, in recent years, with the increase in size of mobile terminals such as smartphones, in order to realize long-term driving with a limited battery capacity, light utilization efficiency has been improved by using a brightness improving film.

Japanese Unexamined Patent Publication No. 11-248941 Japanese Unexamined Patent Publication No. 11-248942 JP-A-11-64840 Japanese Unexamined Patent Publication No. 11-64841 Japanese Patent No. 4880719

It was found that when the above-mentioned composite polarizing plate was subjected to a high temperature durability test, wrinkles were generated in the brightness improving film and the composite polarizing plate had a poor appearance. Such poor appearance can cause a decrease in visibility when the composite polarizing plate is applied to a liquid crystal display device.

An object of the present invention is to provide a composite polarizing plate capable of suppressing appearance defects even in a high temperature durability test and a liquid crystal display device using the same.

The present invention provides the following composite polarizing plate and liquid crystal display device.
[1] A composite polarizing plate having a polarizing plate having a protective layer on at least one side of the linearly polarizing layer and a brightness improving film.
The first pressure-sensitive adhesive layer, the buffer layer, and the brightness improving film are laminated in this order on the protective layer side of the polarizing plate.
A composite polarizing plate having a tensile elastic modulus of 1.5 GPa or more at a temperature of 23 ° C. and a relative humidity of 55% of the buffer layer.
[2] The composite polarizing plate according to [1], wherein the buffer layer and the brightness improving film are bonded to each other via a second pressure-sensitive adhesive layer.
[3] The composite polarizing plate according to [1] or [2], wherein the buffer layer is a resin film.
[4] The composite according to [3], wherein the resin film includes a film made of at least one resin selected from the group consisting of a cellulose ester resin, a (meth) acrylic acid resin, and a cyclic olefin resin. Polarizer.
[5] The composite polarizing plate according to [1], wherein the buffer layer is in direct contact with the brightness improving film.
[6] The composite polarizing plate according to [1] or [5], wherein the buffer layer is a cured product layer of a resin composition containing a curable component.
[7] The composite polarizing plate according to [6], wherein the curable component contains an active energy ray-curable compound.
[8] The composite polarizing plate according to any one of [1] to [7], wherein the in-plane retardation Re (590) of the buffer layer at a wavelength of 590 nm is 20 nm or less.
[9] The composite polarizing plate according to any one of [1] to [8], wherein the first pressure-sensitive adhesive layer is a bonding layer of the protective layer of the polarizing plate and the buffer layer.
[10] The composite polarizing plate according to any one of [1] to [9], wherein the polarizing plate has the protective layers on both sides of the linearly polarizing layer.
[11] The composite polarizing plate according to any one of [1] to [10], which has a third pressure-sensitive adhesive layer on the side of the polarizing plate opposite to the brightness improving film side.
[12] The composite polarizing plate according to [11], which has a release film on the side of the third pressure-sensitive adhesive layer opposite to the polarizing plate side.
[13] A liquid crystal display device including the composite polarizing plate according to any one of [1] to [12] and a liquid crystal cell.
[14] Further, it has a backlight and has a backlight.
The liquid crystal display device according to [13], wherein the composite polarizing plate is arranged between the liquid crystal cell and the backlight so that the brightness improving film side is the backlight side.

According to the present invention, it is possible to provide a composite polarizing plate in which an appearance defect is suppressed in a high temperature durability test and a display device using the same.

It is the schematic sectional drawing which shows an example of the composite polarizing plate of this invention schematically. It is the schematic cross-sectional view which shows typically another example of the composite polarizing plate of this invention. It is schematic cross-sectional view which shows still another example of the composite polarizing plate of this invention schematically. It is schematic cross-sectional view which shows still another example of the composite polarizing plate of this invention schematically. It is schematic cross-sectional view which shows typically an example of the liquid crystal display device of this invention. It is the schematic sectional drawing which shows another example of the liquid crystal display device of this invention schematically.

Hereinafter, preferred embodiments of the composite polarizing plate of the present invention and a liquid crystal display device using the composite polarizing plate will be described with reference to the drawings.

<Composite polarizing plate>
The composite polarizing plate of the present invention is a composite polarizing plate having a polarizing plate having a protective layer on at least one side of the linearly polarizing layer and a brightness improving film.
The first pressure-sensitive adhesive layer, the buffer layer, and the brightness improving film are laminated in this order on the protective layer side of the polarizing plate.
The tensile elastic modulus at a temperature of the buffer layer of 23 ° C. and a relative humidity of 55% is 1.5 GPa or more.

The brightness improving film reflects linearly polarized light of a predetermined polarization axis or circularly polarized light in a predetermined direction among the incident natural light and the like, and other light can be transmitted. Therefore, in a composite polarizing plate in which a brightness improving film and a polarizing plate including a linearly polarizing layer are laminated, light from a light source such as a backlight of a liquid crystal display device or the like is incident to obtain transmitted light in a predetermined polarized state. Light other than the predetermined polarized state can be reflected without being transmitted. When a brightness-improving film and a composite polarizing plate having a linearly polarizing layer are used in a liquid crystal display device, the light reflected on the brightness-improving film surface is further inverted via a reflection layer or the like provided behind the brightness-improving film surface. The amount of light transmitted through the luminance improving film can be increased by re-inciding the light on the luminance improving film and transmitting a part or all of the light as light in a predetermined polarized state. Further, by supplying polarized light that is difficult to be absorbed by the linear polarizing layer to the polarizing plate, the amount of light that can be used for image display or the like can be increased, and the brightness in the liquid crystal display device can be improved.

As described above, in the luminance improving film, light having a polarization direction that is absorbed by the linearly polarizing layer is temporarily reflected by the luminance improving film without being incident on the linearly polarizing layer, and further, a reflecting layer provided behind the linear polarizing layer. It is repeated to invert it and re-enter it on the brightness improving film. As a result, of the light reflected and inverted between the linear polarizing layer and the brightness improving film, only polarized light having a polarization direction capable of passing through the linear polarizing layer passes through the brightness improving film, and this transmitted light is transmitted. It can be supplied to the linearly polarized light layer. Therefore, by using the composite polarizing plate including the brightness improving film and the polarizing plate as described above, the light such as the backlight can be efficiently used for the image display of the liquid crystal display device in the liquid crystal display device or the like, and the screen is brightened. can do.

As will be described later, the buffer layer contained in the composite polarizing plate may be a resin film or a cured product layer of a resin composition containing a curable component. The tensile elastic modulus of the buffer layer may be 3 GPa or more, 5 GPa or more, usually 10 GPa or less, and 8 GPa or less. The tensile modulus can be measured by the method described in Examples described later. The tensile elastic modulus when the buffer layer is a cured product layer can be measured by the following procedure. The resin composition is applied to the release-treated surface of the release-treated polyethylene terephthalate film (hereinafter, may be referred to as “PET film”) using an applicator so that the thickness after drying is 100 μm. Then, it was placed in a room temperature atmosphere for 30 minutes for pre-drying, and then placed for 5 minutes under the condition of a temperature of 100 ° C. for main drying to remove the solvent contained in the resin composition applied to the PET film. Volatilize well. Finally, a predetermined curing treatment (heat treatment, ultraviolet irradiation treatment, etc.) is performed to prepare a cured product layer on the PET film, and the cured product layer obtained by peeling the PET film is used as a sample for measurement, which will be described later. The tensile elastic modulus may be measured by the method described in the examples described above.

It was clarified that the wrinkles generated in the brightness improving film after the high temperature durability test are caused by the shrinkage of the polarizing plate in a high temperature environment. In the composite polarizing plate of the present embodiment, a buffer layer is interposed between the polarizing plate and the brightness improving film. Since the buffer layer has a tensile elastic modulus in the above range, it is not easily deformed. Therefore, even if the polarizing plate shrinks when the high-temperature durability test of the composite polarizing plate is performed, the polarizing plate shrinks due to the presence of a buffer layer that is not easily deformed between the polarizing plate and the brightness improving film. Along with this, it is possible to suppress the shrinkage of the brightness improving film. As a result, it is possible to suppress the occurrence of wrinkles at the edges of the brightness improving film, and thus it is possible to suppress the occurrence of poor appearance of the composite polarizing plate subjected to the high temperature durability test. Further, when this composite polarizing plate is applied to a liquid crystal display device, it is possible to suppress a decrease in visibility of an image displayed on the screen of the liquid crystal display device.

The in-plane retardation Re (590) of the buffer layer at a wavelength of 590 nm is preferably 20 nm or less, may be 10 nm or less, may be 5 nm or less, or may be 0 nm. When Re (590) of the buffer layer is within the above range, it is possible to suppress a decrease in viewing angle characteristics when the composite polarizing plate is applied to a liquid crystal display device. The in-plane retardation Re (590) can be measured by the method described in Examples described later. In the in-plane retardation Re (590) when the buffer layer is a cured product layer, the buffer layer is a cured product layer except that the thickness after drying is the actual thickness of the buffer layer contained in the composite polarizing plate. A sample for measurement may be prepared according to the procedure for preparing a sample for measurement used for measuring the tensile elastic modulus of the case, and the measurement may be carried out by the method described in Examples described later.

The first pressure-sensitive adhesive layer is preferably a pressure-sensitive adhesive layer for bonding the protective layer of the polarizing plate and the buffer layer. In this case, the first pressure-sensitive adhesive layer is provided so as to be in direct contact with both the protective layer and the buffer layer of the polarizing plate.

Hereinafter, embodiments of the above-mentioned composite polarizing plate will be specifically described.
[Embodiment 1]
1 and 2 are schematic cross-sectional views schematically showing an example of the composite polarizing plate of the present embodiment. In the composite polarizing plate 1 of the present embodiment, the polarizing plate 10, the first pressure-sensitive adhesive layer 31, the buffer layer 15a, the second pressure-sensitive adhesive layer 32, and the brightness improving film 18 are laminated in this order. The second pressure-sensitive adhesive layer 32 is a pressure-sensitive adhesive layer for adhering the buffer layer 15a and the brightness-improving film 18, so that the second pressure-sensitive adhesive layer 32 is in contact with both the buffer layer 15a and the brightness-improving film 18. It is provided in.

The polarizing plates 10 shown in FIGS. 1 and 2 are arranged on the opposite side of the first protective layer 12 arranged on the brightness improving film 18 side of the linearly polarizing layer 11 and the brightness improving film 18 side of the linearly polarizing layer 11. It has a second protective layer 13. The polarizing plate 10 may have a first protective layer 12 and may not have a second protective layer 13.

As shown in FIG. 2, the composite polarizing plate 1 may have a third pressure-sensitive adhesive layer 33 on the side of the polarizing plate 10 opposite to the brightness improving film 18 side. The third pressure-sensitive adhesive layer 33 can be used for bonding the composite polarizing plate 1 to the liquid crystal cell in the liquid crystal display device described later. The composite polarizing plate 1 may further have a release film 35 for covering and protecting the surface of the third pressure-sensitive adhesive layer 33 on the side of the third pressure-sensitive adhesive layer 33 opposite to the polarizing plate 10 side ( Figure 2).

The buffer layer 15a provided on the composite polarizing plate 1 is preferably a resin film. The resin film is preferably formed of a resin material having excellent transparency, mechanical strength, thermal stability, moisture shielding property, stability of retardation value, etc., and the resin material is preferably a thermoplastic resin. preferable. The resin film may have a single-layer structure or a multi-layer structure. The resin film may be a stretched film. For example, the tensile elastic modulus can be adjusted by selecting the type of resin constituting the resin film, stretching the resin film, and the like. The details of the resin (resin material) for forming the resin film constituting the buffer layer 15a will be described later, but at least one selected from a cellulose ester resin, a (meth) acrylic acid resin, and a cyclic olefin resin. It is preferable to use a film made of the above resin.

In the composite polarizing plate 1, the first protective layer 12 side of the polarizing plate 10 and the buffer layer 15a are bonded together by the first pressure-sensitive adhesive layer 31, and the second pressure-sensitive adhesive layer 15a and the brightness improving film 18 are bonded together. It can be obtained by laminating with the agent layer 32. When the composite polarizing plate 1 has the third pressure-sensitive adhesive layer 33, for example, a pressure-sensitive adhesive sheet having the third pressure-sensitive adhesive layer 33 formed on the release film 35 may be laminated on the polarizing plate 10.

[Embodiment 2]
3 and 4 are schematic cross-sectional views schematically showing another example of the composite polarizing plate of the present embodiment. In the composite polarizing plate 2 of the present embodiment, the polarizing plate 10, the first pressure-sensitive adhesive layer 31, the buffer layer 15b, and the brightness improving film 18 are laminated in this order. The polarizing plates 10 shown in FIGS. 3 and 4 are arranged on the opposite side of the first protective layer 12 arranged on the brightness improving film 18 side of the linearly polarizing layer 11 and the brightness improving film 18 side of the linearly polarizing layer 11. It has a second protective layer 13. The polarizing plate 10 may have a first protective layer 12 and may not have a second protective layer 13.

The composite polarizing plate 2 has a third pressure-sensitive adhesive layer 33 and a release film 35 in this order on the side of the polarizing plate 10 opposite to the brightness improving film 18 side, as described in the composite polarizing plate 1 shown in FIG. It may be (Fig. 4).

The buffer layer 15b provided on the composite polarizing plate 2 is provided so as to be in direct contact with the brightness improving film 18 without interposing another layer such as an adhesive layer. The buffer layer 15b is preferably a cured product layer of a resin composition containing a curable component. The buffer layer 15b, which is a cured product layer, can be formed, for example, by applying the above resin composition to one side of the brightness improving film 18 and curing the curable component. For the buffer layer 15b, which is a cured product layer, the tensile elastic modulus can be adjusted within the above range by selecting, for example, the type of curable component. The details of the curable component constituting the buffer layer 15b will be described later, but it is more preferable that the cured product layer is a resin composition containing an active energy ray-curable compound as the curable component.

In the composite polarizing plate 2, the buffer layer 15b side of the laminate in which the buffer layer 15b is formed on the brightness improving film 18 and the first protective layer 12 side of the polarizing plate 10 are bonded by the first adhesive layer 31. Can be obtained by When the composite polarizing plate 2 has the third pressure-sensitive adhesive layer 33, for example, the third pressure-sensitive adhesive layer 33 can be provided by the method described in the case where the composite polarizing plate 1 is provided with the third pressure-sensitive adhesive layer 33.

<Liquid crystal display device>
5 and 6 are schematic cross-sectional views schematically showing an example of the liquid crystal display device of the present embodiment. The liquid crystal display devices 5 and 6 of the present embodiment include the composite polarizing plate 1 or the composite polarizing plate 2 described above, a liquid crystal cell 41, and usually a backlight 42. The composite

polarizing plates

1 and 2 are preferably provided on the backlight 42 side (opposite side to the viewing side) of the liquid crystal cell 41. In this case, as shown in FIGS. 5 and 6, the composite

polarizing plates

1 and 2 are provided with a third pressure-sensitive adhesive layer 33 on the polarizing plate 10 side so that the brightness improving film 18 side is arranged on the backlight 42 side. It is preferable that the film is laminated on the liquid crystal cell 41 via.

In the liquid crystal display devices 5 and 6 having the composite polarizing plate 1 or the composite polarizing plate 2, since the composite

polarizing plates

1 and 2 include the brightness improving film 18 as described above, the light of the backlight 42 is efficiently displayed on the liquid crystal. It can be used to display images of devices 5 and 6, and can brighten the screen.

Since the composite

polarizing plates

1 and 2 have the above-mentioned

cushioning layers

15a and 15b having a tensile elastic modulus, respectively, appearance defects are unlikely to occur when a high temperature durability test is performed. As a result, the liquid crystal display devices 5 and 6 having the composite polarizing plate 1 or the composite polarizing plate 2 can suppress the deterioration of visibility even when exposed to high temperature conditions.

Hereinafter, details of each member forming the above-mentioned composite polarizing plate and liquid crystal display device will be described.

[Cushioning layer]
The buffer layer has a tensile elastic modulus in the above range. The buffer layer preferably has an in-plane retardation Re (590) in the above range. The buffer layer may be a resin film or a cured product layer of a resin composition containing a curable component.

The thickness of the buffer layer is preferably 20 μm or more, more preferably 25 μm or more, further preferably 30 μm or more, and usually 80 μm or less, 70 μm or less, 60 μm or less. There may be.

[Resin film constituting the buffer layer]
When the buffer layer is a resin film, the resin material (resin) constituting the resin film is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding property, stability of retardation value, and the like. The resin material is preferably a thermoplastic resin. Such a resin material is not particularly limited, and is, for example, a cellulose ester resin; a (meth) acrylic acid resin; an olefin resin such as a chain aliphatic olefin resin or a cyclic olefin resin; a polyvinyl chloride resin. Resin; styrene resin; acrylonitrile / butadiene / styrene resin; acrylonitrile / styrene resin; polyvinyl acetate resin; polyvinylidene chloride resin; polyamide resin; polyacetal resin; polycarbonate resin; modified polyphenylene ether resin; Polybutylene teflate-based resin, polyester-based resin such as polyethylene teftalate-based resin; polysulfone-based resin; polyether sulfone-based resin; polyarylate-based resin; polyamideimide-based resin; polyimide-based resin, etc. Species or a combination of two or more species can be used. Among them, it is preferable to use a resin selected from a cellulose ester resin, a (meth) acrylic acid resin, and a cyclic olefin resin. As used herein, the term "(meth) acrylic" means that it may be either acrylic or methacryl. (Meta) "(Meta)" such as acryloyl has the same meaning.

The resin material constituting the resin film can be used after performing any appropriate polymer modification, and the polymer modification includes, for example, copolymerization, cross-linking, molecular terminalization, stereoregularity control, and dissimilar polymers. Modifications such as mixing, including cases involving a reaction, can be mentioned.

In the cellulose ester-based resin, a part or all of hydrogen atoms in the hydroxyl group of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (perforated tree pulp, coniferous tree pulp) are replaced with acetyl group, propionyl group and / or butyryl group. In addition, it is a cellulose organic acid ester or a cellulose mixed organic acid ester. For example, those composed of acetic acid ester of cellulose, propionic acid ester, butyric acid ester, mixed ester thereof and the like can be mentioned. Among them, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

The (meth) acrylic acid-based resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymers; methyl methacrylate- (meth) acrylic acid esters. Copolymers: Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate-cyclohexyl methacrylate copolymer, methacryl Includes a copolymer of methyl methacrylate such as a methyl- (meth) acrylate norbornyl copolymer and a compound having an alicyclic hydrocarbon group. _{A polymer containing poly (meth) acrylic acid C 1-6} alkyl ester as a main component, such as methyl poly (meth) acrylate, is preferably used, and more preferably methyl methacrylate is used as a main component (50 to 100% by weight). , Preferably 70 to 100% by weight), a methyl methacrylate-based resin is used.

The (meth) acrylic acid-based resin may have a structural unit that expresses positive birefringence. If it has a structural unit that expresses positive birefringence and a structural unit that expresses negative birefringence, the position of the film formed from the (meth) acrylic acid-based resin can be adjusted by adjusting the abundance ratio thereof. The phase difference can be controlled, and a (meth) acrylic acid-based resin film having a low phase difference can be obtained. As the structural unit that expresses positive birefringence, for example, a structural unit constituting a lactone ring, polycarbonate, polyvinyl alcohol, cellulose acetate, polyester, polyarylate, polyimide, polyolefin, etc., is represented by the general formula (1) described later. Structural units can be mentioned. Examples of the structural unit that expresses negative birefringence include structural units derived from styrene-based monomers, maleimide-based monomers, etc., polymethylmethacrylate structural units, structural units represented by the general formula (3) described later, and the like. Can be mentioned.

As the (meth) acrylic acid-based resin, a (meth) acrylic acid-based resin having a lactone ring structure or a glutarimide structure is preferably used. A (meth) acrylic acid-based resin having a lactone ring structure or a glutarimide structure has excellent heat resistance. More preferably, it is a (meth) acrylic acid-based resin having a glutarimide structure. By using a (meth) acrylic acid-based resin having a glutarimide structure, a (meth) acrylic acid-based resin film having low moisture permeability and low phase difference and ultraviolet transmittance can be obtained. Examples of the (meth) acrylic acid-based resin having a glutarimide structure (hereinafter, also referred to as “glutarimide resin”) include JP-A-2006-309033, JP-A-2006-317560, and JP-A-2006-328329. , JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337569, JP-A-2007-9182, It is described in Kai 2009-161744. These statements are incorporated herein by reference.

The glutarimide resin is preferably a structural unit represented by the following general formula (1) (hereinafter, also referred to as “glutarimide unit”) and a structural unit represented by the following general formula (2) (hereinafter, “( Meta) Also referred to as "acrylic acid ester unit").

[In the general formula (1), R ¹ and R ² are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ is hydrogen, an alkyl group having 1 to 18 carbon atoms, and an alkyl group having 1 to 18 carbon atoms. It is a substituent containing 3 to 12 cycloalkyl groups or an aromatic ring having 5 to 15 carbon atoms.
In the general formula (2), R ⁴ and R ⁵ are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁶ is hydrogen, an alkyl group having 1 to 18 carbon atoms, and 3 carbon atoms. It is a substituent containing a cycloalkyl group of up to 12 or an aromatic ring having 5 to 15 carbon atoms. ]

The glutarimide resin may further contain a structural unit represented by the following general formula (3) (hereinafter, also referred to as “aromatic vinyl unit”), if necessary.

[In the general formula (3), R ⁷ is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ is an aryl group having 6 to 10 carbon atoms].

In the above general formula (1), preferably, R ¹ and R ² are independently hydrogen or methyl groups, and R ³ is hydrogen, methyl group, butyl group, or cyclohexyl group, and more preferably. , R ¹ is a methyl group, R ² is a hydrogen, and R ³ is a methyl group.

The glutarimide resin is a glutarimide unit, may include only a single type, R ¹ in the general formula ^(1), R ^2, and R ³ also include a plurality of different types Good.

The glutarimide unit can be formed by imidizing the (meth) acrylic acid ester unit represented by the above general formula (2). The glutarimide unit is an acid anhydride such as maleic anhydride, or a half ester of such an acid anhydride and a linear or branched alcohol having 1 to 20 carbon atoms; crotonic acid, methacrylic acid, maleic acid. It can also be formed by imidizing α, β-ethylenically unsaturated carboxylic acids such as maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, and citraconic acid.

In the above general formula (2), preferably R ⁴ and R ⁵ are independently hydrogen or methyl groups, R ⁶ is hydrogen or methyl group, and more preferably R ⁴ is hydrogen. , R ⁵ is a methyl group and R ⁶ is a methyl group.

Glutarimide resin as (meth) acrylic acid ester unit, may include only a single type, include R ^4, R ^5, and a plurality of types of R ⁶ are different in the above general formula (2) You may be.

The glutarimide resin preferably contains styrene, α-methylstyrene and the like as the aromatic vinyl unit represented by the above general formula (3), and more preferably contains styrene. By using such a glutarimide resin having an aromatic vinyl unit, the positive birefringence of the glutarimide structure can be reduced, and a (meth) acrylic resin film having a lower phase difference can be obtained.

The glutarimide resin may contain only a single type as the aromatic vinyl unit, or may contain a plurality of types in which ^{R 7} and R ^{8 in the above general formula (3) are different.}

The content of the glutarimide unit in glutarimide resin is preferably, for example, vary depending on the structure and the like of R ^3. The content of the glutarimide unit is preferably 1% by weight to 80% by weight, more preferably 1% by weight to 70% by weight, still more preferably 1% by weight, based on the total structural unit of the glutarimide resin. It is about 60% by weight, and particularly preferably 1% by weight to 50% by weight. When the content of the glutarimide unit is in such a range, a low phase difference (meth) acrylic resin film having excellent heat resistance can be obtained.

The content of the aromatic vinyl unit in the glutarimide resin can be appropriately set according to the purpose and required properties. Depending on the application, the content of the aromatic vinyl unit may be zero. When the aromatic vinyl unit is contained, the content thereof is preferably 10% by weight to 80% by weight, more preferably 20% by weight to 80% by weight, based on the glutarimide unit of the glutarimide resin. It is more preferably 20% by weight to 60% by weight, and particularly preferably 20% by weight to 50% by weight. When the content of the aromatic vinyl unit is in such a range, a (meth) acrylic acid-based resin film having a low phase difference and excellent heat resistance and mechanical strength can be obtained.

If necessary, the glutarimide resin may be further copolymerized with other structural units other than the glutarimide unit, the (meth) acrylic acid ester unit, and the aromatic vinyl unit. Other structural units include, for example, a structure composed of nitrile-based monomers such as acrylonitrile and methacrylonitrile; maleimide-based monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. The unit is mentioned. These other structural units may be directly copolymerized or graft-copolymerized in the glutarimide resin.

The olefin-based resin is composed of a structural unit derived from a chain aliphatic olefin such as ethylene and propylene, or an alicyclic olefin such as norbornene or a substitute thereof (hereinafter, these are collectively referred to as a norbornene-based monomer). It is a resin. The olefin resin may be a copolymer using two or more kinds of monomers.

As the olefin resin, a cyclic olefin resin which is a resin mainly containing a constituent unit derived from an alicyclic olefin is preferably used. Typical examples of the alicyclic olefin constituting the cyclic olefin resin include norbornene-based monomers. Norbornene is a compound in which one carbon-carbon bond of norbornane is a double bond, and is named bicyclo [2,2,1] hept-2-ene according to the IUPAC nomenclature. is there. Examples of the substitution product of norbornene include 3-substituted product, 4-substituted product, 4,5-di-substituted product, etc., with the double bond position of norbornene at the 1,2-position, and further. Dicyclopentadiene, dimethanooctahydronaphthalene and the like can also be mentioned.

The cyclic olefin resin may or may not have a norbornane ring as its constituent unit. Examples of the norbornene-based monomer forming a cyclic olefin-based resin having no norbornene ring as a constituent unit include those having a 5-membered ring by ring-opening, typically norbornene, dicyclopentadiene, 1- or 4-. Examples thereof include methylnorbornene and 4-phenylnorbornene. When the cyclic olefin-based resin is a copolymer, the arrangement state of the molecule is not particularly limited, and it may be a random copolymer, a block copolymer, or a graft. It may be a polymer.

More specific examples of the cyclic olefin resin include, for example, a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer of a norbornene-based monomer and another monomer, and addition of maleic acid and cyclopentadiene to them. Examples thereof include polymer modified products made, and polymers or copolymers obtained by hydrogenating them; addition polymers of norbornene-based monomers, and addition copolymers of norbornene-based monomers and other monomers. Examples of other monomers used as copolymers include α-olefins, cycloalkenes, non-conjugated dienes and the like. Further, the cyclic olefin resin may be a copolymer using one or more of norbornene-based monomers and other alicyclic olefins.

As the cyclic olefin resin, a ring-opening polymer using a norbornene-based monomer or a resin obtained by hydrogenating a ring-opening copolymer is preferably used.

The resin material constituting the above-mentioned resin film may contain an appropriate additive as long as the transparency is not impaired. Additives include, for example, antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact resistant aids. , Matters, antibacterial agents, antifungal agents and the like. A plurality of kinds of these additives may be used in combination.

As a method for forming a resin film using the above-mentioned resin material, any optimum method may be appropriately selected. For example, a solvent casting method in which a resin dissolved in a solvent is cast on a metal band or drum and the solvent is dried and removed to obtain a film. The resin is heated above its melting temperature, kneaded and extruded from a die. , A melt extrusion method for obtaining a film by cooling, and the like. In the melt extrusion method, a single-layer film can be extruded, or a multilayer film can be extruded at the same time.

As described above, the resin film may be a stretched film that has been stretched.
The tensile elastic modulus may be adjusted to a desired range by performing a stretching process. Examples of the stretching treatment include uniaxial stretching and biaxial stretching.

[Cured product layer of resin composition containing curable components constituting the buffer layer]
When the buffer layer is a cured product layer of a resin composition containing a curable component, the curable component contained in the resin composition is an active energy ray-curable compound that is cured by irradiation with active energy rays, or a cured product by heating. It is preferably a thermosetting cured product. The curable component is more preferably an active energy ray-curable compound.

[A] Resin Composition Containing Active Energy Ray Curable Compound Examples of the active energy ray curable compound include an electron beam curable compound, an ultraviolet curable compound, and a visible light curable compound. Of these, an ultraviolet curable compound or a visible light curable compound is preferable, and an ultraviolet curable compound is more preferable. The resin composition containing the ultraviolet curable compound or the visible light curable compound may be a radical polymerization type resin composition or a cationic polymerization type resin composition. In the present specification, ultraviolet rays refer to active energy rays having a wavelength in the range of 10 nm or more and less than 380 nm, and visible light means active energy rays having a wavelength of 380 nm or more and 800 nm or less.

[A1] Radical Polymerizable Resin Composition The radically polymerizable resin composition contains a radically polymerizable compound as a curable component. Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group of a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group. As the radically polymerizable compound, either a monofunctional radically polymerizable compound or a bifunctional or higher functional radically polymerizable compound can be used. The radically polymerizable compound may be used alone or in combination of two or more. As the radically polymerizable compound, for example, a compound having a (meth) acryloyl group is suitable.

(Monofunctional radical polymerizable compound)
Examples of the monofunctional radically polymerizable compound include (meth) acrylamide derivatives having a (meth) acrylamide group. The (meth) acrylamide derivative is preferable in terms of ensuring the adhesiveness between the brightness-improving film and the cured product layer, and also in terms of high polymerization rate and excellent productivity. Specific examples of the (meth) acrylamide derivative include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N. -N-alkyl group-containing (meth) acrylamide derivatives such as butyl (meth) acrylamide and N-hexyl (meth) acrylamide; N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N- N-Hydroxyalkyl group-containing (meth) acrylamide derivatives such as propane (meth) acrylamide; N-aminoalkyl group-containing (meth) acrylamide derivatives such as aminomethyl (meth) acrylamide and aminoethyl (meth) acrylamide; N-methoxymethyl N-alkoxy group-containing (meth) acrylamide derivatives such as acrylamide and N-ethoxymethylacrylamide; N-mercaptoalkyl group-containing (meth) acrylamide derivatives such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide can be mentioned. .. Examples of the heterocyclic-containing (meth) acrylamide derivative in which the nitrogen atom of the (meth) acrylamide group forms a heterocycle include N-acrylloylmorpholine, N-acrylloylpiperidin, N-methacryloylpiperidin, and N-acrylloylpyrolidin. Can be mentioned.

Among the (meth) acrylamide derivatives, when the cured product layer is provided so as to be in direct contact with the brightness improving film, an N-hydroxyalkyl group-containing (meth) acrylamide derivative is preferable from the viewpoint of adhesiveness, and N-hydroxyalkyl group-containing (meth) acrylamide derivative is particularly preferable. Hydroxyethyl (meth) acrylamide is preferred.

Examples of the monofunctional radically polymerizable compound include various (meth) acrylic acid derivatives having a (meth) acryloyloxy group. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl. (Meta) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, t-pentyl (meth) acrylate, 3-pentyl (meth) acrylate, 2,2-dimethyl Butyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) acrylate, n -Examples include (meth) acrylic acid (1 to 20 carbon atoms) alkyl esters such as octadecyl (meth) acrylate.

Examples of the (meth) acrylic acid derivative include cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and cyclopentyl (meth) acrylate; aralkyl (meth) acrylates such as benzyl (meth) acrylate; 2-isobornyl (meth). Acrylate, 2-norbornylmethyl (meth) acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl-2-norbornylmethyl (meth) acrylate, dicyclopentenyl (meth) acrylice Polycyclic (meth) acrylates such as to, dicyclopentenyloxyethyl (meth) acrylicate, dicyclopentanyl (meth) acrylicate; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) An alkoxy group such as acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, alkylphenoxypolyethylene glycol (meth) acrylate, or phenoxy. Group-containing (meth) acrylate and the like can be mentioned.

Examples of the (meth) acrylic acid derivative include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth). Hydroxyalkyl (meth) acrylates such as meta) acrylates, 6-hydroxyhexyl (meth) acrylates, 8-hydroxyoctyl (meth) acrylates, 10-hydroxydecyl (meth) acrylates, 12-hydroxylauryl (meth) acrylates; [4 -(Hydroxymethyl) cyclohexyl] Methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate and other hydroxyl group-containing (meth) acrylate; glycidyl (meth) acrylate, 4-hydroxybutyl (Meta) Acrylate Group-containing (meth) acrylate such as glycidyl ether; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,2-trifluoroethylethyl (meth) acrylate, tetrafluoropropyl (meth) ) Halogen-containing (meth) acrylates such as acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate; dimethyl Alkylaminoalkyl (meth) acrylates such as aminoethyl (meth) acrylates; 3-oxetanylmethyl (meth) acrylates, 3-methyl-oxetanylmethyl (meth) acrylates, 3-ethyl-oxetanylmethyl (meth) acrylates, 3-butylate. Oxetane group-containing (meth) acrylates such as ruoxetanyl methyl (meth) acrylate and 3-hexyl oxetanyl methyl (meth) acrylate; having a heterocycle such as tetrahydrofurfuryl (meth) acrylate and butyrolactone (meth) acrylate (meth) Acrylate; Neopentyl glycol (meth) acrylic acid adduct of hydroxypivalate; p-phenylphenol (meth) acrylate and the like can be mentioned.

Examples of the monofunctional radically polymerizable compound include carboxyl group-containing monomers such as (meth) acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

Examples of the monofunctional radically polymerizable compound include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazin, vinylpyrazine, and vinylpyrrole. , Vinyl imidazole, vinyl oxazole, vinyl morpholin, and other vinyl-based monomers having a nitrogen-containing heterocycle.

As the monofunctional radically polymerizable compound, for example, a radically polymerizable compound having an active methylene group can be used. A radically polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth) acrylic group at the terminal or in the molecule and having an active methylene group. Examples of the active methylene group include an acetoacetyl group, an alkoxymalonyl group, a cyanoacetyl group and the like, and the active methylene group is preferably an acetoacetyl group. Specific examples of the radically polymerizable compound having an active methylene group include 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxypropyl (meth) acrylate, 2-acetacetoxy-1-methylethyl (meth) acrylate and the like. Acetoacetoxyalkyl (meth) acrylate; 2-ethoxymalonyloxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N- (2-cyanoacetoxyethyl) acrylamide, N- (2-propionylacetoxybutyl) Examples thereof include acrylamide, N- (4-acetoacetoxymethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide and the like. The radically polymerizable compound having an active methylene group is preferably acetoacetoxyalkyl (meth) acrylate.

(Polyfunctional radical polymerizable compound)
Examples of the bifunctional or higher polyfunctional radical polymerizable compound include N, N'-methylenebis (meth) acrylamide, which is a polyfunctional (meth) acrylamide derivative, tripropylene glycol di (meth) acrylate, and tetraethylene glycol di (meth). ) Acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate , Bisphenol A di (meth) acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (Meta) Acrylate, Tricyclodecanedimethanol Di (Meta) Acrylate, Cyclic Trimethylol Propaneformal (Meta) Acrylate, Dioxane Glycol Di (Meta) Acrylate, Trimethylol Propantri (Meta) Acrylate, Pentaerythritol Tri (Meta) Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, EO-modified diglycerin tetra (meth) acrylate, etc. Eesterates; 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene and the like can be mentioned. Specific examples include Aronix M-220 (manufactured by Toagosei Co., Ltd.), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DCP-A (Kyoeisha Chemical Co., Ltd.). , SR-531 (manufactured by Sartomer), CD-536 (manufactured by Sartomer) and the like are preferable. When these polyfunctional (meth) acrylamide derivatives are used, the radical polymerization type resin composition may contain various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and various (meth) acrylates, if necessary. ) It may contain an acrylate-based monomer or the like. The polyfunctional (meth) acrylamide derivative is preferably contained in the radical polymerization type resin composition because the polymerization rate is high and the productivity is excellent, and the crosslinkability when the resin composition is a cured product is excellent.

The radically polymerizable compound preferably contains a polyfunctional radically polymerizable compound in order to control the water absorption rate of the cured product of the resin composition. Among the polyfunctional radical-polymerizable compounds, those having a high logPow value, which will be described later, are preferable.

The resin composition containing the curable compound for forming the buffer layer preferably has a high octanol / water partition coefficient (hereinafter, may be referred to as “logPow value”). The logPow value is an index showing the lipophilicity of a substance, and means the logarithmic value of the partition coefficient of octanol / water. A high logPow means that it is lipophilic, that is, it has a low water absorption rate. The logPow value can be measured (the flask immersion method described in JIS-Z-7260), but it can also be calculated by calculation. In this specification, the logPow value calculated by ChemDraw Ultra manufactured by Cambridge Soft Co., Ltd. is used. The logPow value of the resin composition can be calculated by the following formula.
Resin composition logPow = Σ (logPowi × Wi)
logPower: LogPower value of each component contained in the resin composition Wi: (number of moles of i component) / (total number of moles of resin composition)
The logPow value of the resin composition is preferably 1 or more, more preferably 2 or more, and most preferably 3 or more.

Examples of the radically polymerizable compound having a high logPow value include alicyclic (meth) such as tricyclodecanedimethanol di (meth) acrylate (logPow = 3.05) and isobornyl (meth) acrylate (logPow = 3.27). Acrylate; Long-chain aliphatic (meth) acrylate such as 1,9-nonanediol di (meth) acrylate (logPow = 3.68), 1,10-decanediol diacrylate (logPow = 4.10); hydroxypivalic acid Multi-branched (meth) acrylates such as neopentyl glycol (meth) acrylic acid adduct (logPow = 3.35), 2-ethyl-2-butylpropanediol di (meth) acrylate (logPow = 3.92); bisphenol A Di (meth) acrylate (logPow = 5.46), bisphenol A ethylene oxide 4 mol adduct Di (meth) acrylate (logPow = 5.15), bisphenol Apropylene oxide 2 mol adduct Di (meth) acrylate (logPow =) 6.10), bisphenol Apropylene oxide 4 mol adduct di (meth) acrylate (logPow = 6.43), 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene (logPow = 7.48), (meth) acrylate containing an aromatic ring such as p-phenylphenol (meth) acrylate (logPow = 3.98) and the like can be mentioned.

For the radically polymerizable compound, a monofunctional radically polymerizable compound and a polyfunctional radically polymerizable compound should be used in combination from the viewpoint of achieving both the adhesiveness between the brightness improving film and the cured product layer and the optical durability in a harsh environment. Is preferable. Usually, it is preferable to use the monofunctional radical polymerizable compound in an amount of 3 to 80% by weight and the polyfunctional radical polymerizable compound in an amount of 20 to 97% by weight based on 100% by weight of the radically polymerizable compound.

(Photopolymerization initiator)
When the radical polymerization type resin composition contains an active energy ray-curable component as a curable component, it can be used as a composition containing an active energy ray-curable compound. In this case, the radical polymerization type resin composition preferably contains a photopolymerization initiator.

As the photopolymerization initiator contained in the radical polymerization type resin composition, a photopolymerization initiator that is cleaved by ultraviolet rays or visible light can be used. Examples of such a photopolymerization initiator include benzophenone compounds such as benzyl, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; 4- (2-hydroxyethoxy) phenyl (2-hydroxy). Aromatic ketone compounds such as -2-propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, α-hydroxycyclohexylphenylketone; methoxyacetophenone, 2,2- Acetphenone compounds such as dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1, etc .; benzoin methyl ether, benzoin Benzophenone ether compounds such as ethyl ether, benzoin isopropyl ether, benzoin butyl ether and anisoine methyl ether; aromatic ketal compounds such as benzyl dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalene sulfonyl chloride; 1-phenone- Photoactive oxime compounds such as 1,1-propanedione-2- (o-ethoxycarbonyl) oxime; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4- Examples thereof include thioxanthone compounds such as dichlorothioxanthone, 2,4-diisopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; benzophenone; halogenated ketone; acylphosphinoxide; acylphosphonate and the like. Among the photopolymerization initiators, those having a high logPow value are preferable. The logPow value of the photopolymerization initiator is preferably 2 or more, more preferably 3 or more, and most preferably 4 or more.

The content of the photopolymerization initiator in the radical polymerization type resin composition is 20 parts by weight or less with respect to 100 parts by weight of the total amount of the curable component (radical polymerizable compound). The blending amount of the photopolymerization initiator is preferably 0.01 to 20 parts by weight, more preferably 0.05 to 10 parts by weight, and further preferably 0.1 to 5 parts by weight.

When the radical polymerization type resin composition contains a visible light curable compound, it is particularly preferable to use a photopolymerization initiator having high sensitivity to light of 380 nm or more.

Examples of the photopolymerization initiator include a compound represented by the following general formula (4) (hereinafter, may be referred to as “compound (4)”).

[In the formula, R ¹¹ and R ¹² are independently -H, -CH ₂ CH ₃ , -iPr (isopropyl group) or -Cl, and R ¹¹ and R ¹² may be the same as each other. It may be very different. ]

In the radical polymerization type resin composition, the compound (4) may be used alone or in combination with a photopolymerization initiator having high sensitivity to light of 380 nm or more, which will be described later. By using the compound (4), the adhesiveness between the brightness improving film and the cured product layer can be improved as compared with the case where a photopolymerization initiator having high sensitivity to light of 380 nm or more is used alone. .. Among the compounds (4), ^{diethylthioxanthone in which R 11} and R ¹² are −CH ₂ CH ₃ is particularly preferable. The content of the compound (4) in the radical polymerization type resin composition is preferably 0.1 to 5 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total amount of the curable component (radical polymerizable compound). It is more preferably 5 to 4 parts by weight, and even more preferably 0.9 to 3 parts by weight.

Examples of the photopolymerization initiator having high sensitivity to light of 380 nm or more include 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino. -1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone , 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-yl) -phenyl) titanium and the like can be mentioned.

The radical polymerization type resin composition preferably contains a compound represented by the following general formula (5) (hereinafter, may be referred to as "compound (5)") in addition to the compound (4).

[In the formula, R ¹³ , R ¹⁴ and R ¹⁵ are independently -H, -CH ₃ , -CH ₂ CH ₃ , -iPr or -Cl, and R ¹³ , R ¹⁴ and R ¹⁵ are They may be the same or different from each other. ]

As the compound (5), for example, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (trade name: IRGACURE907, manufactured by BASF), which is also a commercially available product, can be preferably used. Is. In addition, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (trade name: IRGACURE369, manufactured by BASF), 2- (dimethylamino) -2-[(4-methylphenyl) ) Methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone (trade name: IRGACURE379, manufactured by BASF) is also preferable because of its high sensitivity.

The radical polymerization type resin composition may contain a polymerization initiation aid, if necessary. Examples of the polymerization initiator include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate and the like. , And ethyl 4-dimethylaminobenzoate is particularly preferable. When a polymerization initiator is used, the content of the polymerization initiator in the radical polymerization type resin composition is usually 0 to 5 parts by weight with respect to 100 parts by weight of the total amount of the curable component (radical polymerizable compound). , Preferably 0 to 4 parts by weight, most preferably 0 to 3 parts by weight.

(Radical polymerizable compound (a1) having an active methylene group and radical polymerization initiator (a2) having a hydrogen abstraction action)
When a radically polymerizable compound (a1) having an active methylene group is used as the radically polymerizable compound contained in the radically polymerizable resin composition, it should be used in combination with a radical polymerization initiator (a2) having a hydrogen abstraction action. Is preferable. According to such a radical polymerization type resin composition, good adhesiveness can be ensured even when a cured layer is provided so as to be in direct contact with the brightness improving film, particularly in a high humidity environment. The reason for this is not clear, but it is speculated as follows. The radically polymerizable compound (a1) having an active methylene group is incorporated into the main chain and / or side chain of the base polymer in the cured product layer while being polymerized together with other radically polymerizable compounds constituting the cured product layer. Form a cured product layer. In this polymerization process, when a radical polymerization initiator (a2) having a hydrogen abstraction action is present, hydrogen is drawn from the radical polymerizable compound (a2) having an active methylene group while forming the base polymer constituting the cured product layer. It is extracted and a radical is generated in the methylene group. Then, the methylene group in which radicals are generated reacts with the hydroxyl group of the brightness improving film, and a covalent bond is formed between the cured product layer and the brightness improving film. As a result, it is considered that the adhesiveness between the brightness improving film and the cured product layer is improved even in a particularly high humidity environment.

Examples of the radical polymerization initiator (a2) having a hydrogen abstraction action include a thioxanthone-based radical polymerization initiator and a benzophenone-based radical polymerization initiator. The radical polymerization initiator (a2) is preferably a thioxanthone-based radical polymerization initiator. Examples of the thioxanthone-based radical polymerization initiator include the above-mentioned compound (4). Specific examples of compound (4) include thioxanthone, dimethylthioxanthone, diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone and the like. Among the compounds (4), ^{diethylthioxanthone in which R 11} and R ¹² are −CH ₂ CH ₃ is particularly preferable.

When the radical polymerization type resin composition contains a radical polymerization compound (a1) having an active methylene group and a radical polymerization initiator (a2) having a hydrogen abstraction action, a curable component (radical polymerizable compound) is contained. ) Is 100% by weight, the radical polymerization compound (a1) having an active methylene group is 1 to 50% by weight, and the radical polymerization initiator (a2) is added to 100 parts by weight of the total amount of the curable component. It is preferably contained in an amount of 0.1 to 10 parts by weight.

As described above, in the presence of the radical polymerization initiator (a2) having a hydrogen abstraction action, radicals are generated in the methylene group of the radical polymerizable compound (a1) having an active methylene group, and the methylene group and the brightness improving film are formed. It is considered that the hydroxyl group reacts with the hydroxyl group to form a covalent bond. Therefore, in order to generate a radical in the methylene group of the radically polymerizable compound (a1) having an active methylene group and sufficiently form such a covalent bond, the total amount of the curable component (radical polymerizable compound) is set to 100% by weight. The radical polymerizable compound (a1) having an active methylene group is preferably contained in an amount of 1 to 50% by weight, more preferably 3 to 30% by weight. In order to sufficiently improve the water resistance and improve the adhesiveness between the brightness improving film and the cured product layer in a high humidity environment, the amount of the radically polymerizable compound (a1) having an active methylene group should be 1% by weight or more. Is preferable. On the other hand, if it exceeds 50% by weight, curing failure of the cured product layer may occur. Further, the radical polymerization initiator (a2) having a hydrogen abstraction action is preferably contained in an amount of 0.1 to 10 parts by weight, more preferably 0.3 to 9 parts by weight, based on 100 parts by weight of the total amount of the curable component. It is more preferable to do so. In order to sufficiently proceed with the hydrogen abstraction reaction, it is preferable to use 0.1 part by weight or more of the radical polymerization initiator (a2). On the other hand, if it exceeds 10 parts by weight, it may not be completely dissolved in the radical polymerization type resin composition.

[A2] Cationic Polymerized Resin Composition The cationically polymerized resin composition contains a cationically polymerizable compound as a curable component. The cationically polymerizable compound is classified into a monofunctional cationically polymerizable compound having one cationically polymerizable functional group in the molecule and a polyfunctional cationically polymerizable compound having two or more cationically polymerizable functional groups in the molecule. .. Since the monofunctional cationically polymerizable compound has a relatively low liquid viscosity, the liquid viscosity of the resin composition can be lowered by containing it in the cationically polymerizable resin composition. In addition, monofunctional cationically polymerizable compounds often have functional groups that express various functions, and by containing them in a cationically polymerizable resin composition, the resin composition and / or a cured product of the resin composition Various functions can be expressed in the layer.

The polyfunctional cationically polymerizable compound is preferably contained in the resin composition because the cured product layer can be three-dimensionally crosslinked. The blending ratio of the monofunctional cationically polymerizable compound and the polyfunctional cationically polymerizable compound in the cationically polymerizable resin composition is 10 parts by weight or more and 1000 parts by weight or more with respect to 100 parts by weight of the monofunctional cationically polymerizable compound. It is preferably contained in the range of parts by weight or less.

Examples of the cationically polymerizable functional group include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of the compound having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. As a cationically polymerizable resin composition, the alicyclic epoxy is excellent in curability and adhesiveness. It is particularly preferable to contain a compound.

Examples of the alicyclic epoxy compound include caprolactone-modified products and trimethylcaprolactone-modified products of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. , Valerolactone modified products, etc., and specifically, seroxide 2021, seroxide 2021A, seroxide 2021P, seroxide 2081, seroxide 2083, seroxide 2085 (all manufactured by Daicel Chemical Industry Co., Ltd., Cyclocure UVR-6105, CyclohexylUVR). -6107, Cyracure 30, R-6110 (all manufactured by Dow Chemical Japan Co., Ltd.) and the like can be mentioned.

A compound having an oxetanyl group is preferably contained because it has the effect of improving the curability of the cationically polymerized resin composition and lowering the liquid viscosity of the composition. Compounds having an oxetane group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, and the like. Di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, phenol novolac oxetane and the like can be mentioned, including Aron Oxetane OXT-101 and Aron Oxetane OXT-121. , Aron Oxetane OXT-221, Aron Oxetane OXT-221, Aron Oxetane OXT-212 (all manufactured by Toa Synthetic Co., Ltd.) and the like are commercially available.

A compound having a vinyl ether group is preferably contained because it has the effect of improving the curability of the cationically polymerized resin composition and lowering the liquid viscosity of the composition. Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol vinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, and tricyclodecane vinyl ether. , Cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol type tetravinyl ether and the like.

(Photocationic polymerization initiator)
The cationically polymerizable resin composition contains at least one compound selected from the above-mentioned curable component having an epoxy group, a compound having an oxetanyl group, and a compound having a vinyl ether group. Since all of these compounds are cured by cationic polymerization, it is preferable that the cationically polymerizable resin composition further contains a photocationic polymerization initiator. This photocationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of an epoxy group or an oxetanyl group. As the photocationic polymerization initiator, a photoacid generator described later is preferably used.

When the resin composition containing the curable compound contains a visible light curable compound, it is particularly preferable to use a photocationic polymerization initiator having high sensitivity to light of 380 nm or more, but the photocationic polymerization initiator is generally used. Since it is a compound that exhibits maximum absorption in the wavelength range around 300 nm or shorter, it is possible to add a light sensitizer that exhibits maximum absorption to light in a longer wavelength range, specifically, a wavelength longer than 380 nm. Sensitive to light of a wavelength near this range, it is possible to promote the generation of cation species or acids from the photocationic polymerization initiator. Examples of the photosensitizer include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreducing dyes and the like. Two or more types may be mixed and used. In particular, the anthracene compound is preferable because it has an excellent photosensitizing effect, and specific examples thereof include anthracene UVS-1331 and anthracene UVS-1221 (manufactured by Kawasaki Kasei Chemicals, Inc.). The content of the photosensitizer is preferably 0.1% by weight to 5% by weight, more preferably 0.5% by weight to 3% by weight.

[A3] Other components The resin composition containing the active energy ray-curable compound is a (meth) acrylic oligomer, a photoacid generator, a compound containing an epoxy group or an alkoxy group, a silane coupling agent, and a compound having a vinyl ether group. , Additives other than these may be contained. Hereinafter, these components will be described.

((Meta) acrylic oligomer)
The radically polymerizable resin composition or the cationically polymerizable resin composition comprises a (meth) acrylic oligomer obtained by polymerizing a (meth) acrylic monomer in addition to a radically polymerizable compound or a cationically polymerizable compound (curable component). Can be contained. By containing a (meth) acrylic oligomer in the resin composition, the curing shrinkage when the resin composition is irradiated with active energy rays to be cured is reduced, and the cured product layer and the brightness improving film are formed. The interfacial stress can be reduced. As a result, it is possible to suppress a decrease in the adhesiveness between the cured product layer of the resin composition and the brightness improving film. In order to sufficiently suppress the curing shrinkage of the cured product layer, it is preferable to contain 3 parts by weight or more of the (meth) acrylic oligomer with respect to 100 parts by weight of the total amount of the curable component, and 5 parts by weight or more is contained. Is preferable. If the content of the (meth) acrylic oligomer in the resin composition is too large, the reaction rate when the resin composition is irradiated with active energy rays is drastically reduced, which may result in poor curing. In order to sufficiently suppress a decrease in the reaction rate, it is preferable to contain 20 parts by weight or less of the (meth) acrylic oligomer, and 15 parts by weight or less, based on 100 parts by weight of the total amount of the curable component. Is more preferable.

Since the radical polymerization type resin composition or the cationic polymerization type resin composition preferably has a low viscosity in consideration of workability and uniformity during coating, the (meth) acrylic oligomer also has a low viscosity. Is preferable. As the (meth) acrylic oligomer having a low viscosity and capable of preventing the curing shrinkage of the cured product layer, those having a weight average molecular weight (Mw) of 15,000 or less are preferable, those having a weight average molecular weight (Mw) of 15,000 or less are more preferable, and those having a weight average molecular weight (Mw) of 10,000 or less are more preferable. Those are particularly preferable.
On the other hand, in order to sufficiently suppress the curing shrinkage of the cured product layer, the weight average molecular weight (Mw) of the (meth) acrylic oligomer is preferably 500 or more, more preferably 1000 or more, and 1500 or more. Is particularly preferable.

Examples of the (meth) acrylic monomer constituting the (meth) acrylic oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and 2-methyl-2. -Nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, t-pentyl ( Meta) acrylate, 3-pentyl (meth) acrylate, 2,2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) ) Alkyl esters of (meth) acrylic acid (1 to 20 carbon atoms) such as acrylate, 4-methyl-2-propylpentyl (meth) acrylate, N-octadecyl (meth) acrylate; cycloalkyl (meth) acrylate (eg,) Cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, etc.); Aralkyl (meth) acrylate (eg, benzyl (meth) acrylate, etc.); Polycyclic (meth) acrylate (eg, 2-isobornyl (meth) acrylate, 2- Norbornylmethyl (meth) acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl-2-norbornylmethyl (meth) acrylate, etc.); hydroxyl group-containing (meth) acrylic acid esters (For example, hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2,3-dihydroxypropylmethyl-butyl (meth) methacrylate, etc.); alkoxy group- or phenoxy group-containing (meth) acrylic acid esters (2) -Methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxyethyl (meth) acrylate Etc.); Epoxy group-containing (meth) acrylic acid esters (eg, glycidyl (meth) acrylate, etc.); Halogen-containing (meth) acrylic acid esters (eg, 2,2,2-trifluoroethyl (meth) acrylate, etc.) 2,2,2-Trifluoroethyl ethyl Ta) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, etc.); alkylaminoalkyl (meth) acrylate (eg, dimethyl) Aminoethyl (meth) acrylate, etc.) and the like. These (meth) acrylates can be used alone or in combination of two or more.

Specific examples of the (meth) acrylic oligomer include "ARUFON" manufactured by Toagosei Co., Ltd., "Actflow" manufactured by Soken Chemical Co., Ltd., and "JONCRYL" manufactured by BASF Japan Ltd. Among the (meth) acrylic oligomers, those having a high logPow value are preferable. The logPow value of the (meth) acrylic oligomer is preferably 2 or more, more preferably 3 or more, and most preferably 4 or more.

(Photoacid generator)
The resin composition containing the active energy ray-curable compound can contain a photoacid generator. When the resin composition contains a photoacid generator, the water resistance and durability of the cured product layer can be dramatically improved as compared with the case where the photoacid generator is not contained. The photoacid generator can be represented by the following general formula (6).

[In the formula, L ⁺ represents any onium cation. Further, X ^- _{^{_{^{_{is, PF 6 -, SbF 6 -}}}}} , AsF 6 -, SbCl 6 -, BiCl 5 -, SnCl 6 -, ClO 4 -, dithiocarbamate anion, SCN ^- counter anion more selected from the group consisting of Represents. ]

For X ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , or AsF ₆ ⁻ is preferable, and PF ₆ ⁻ or SbF ₆ ⁻ is more preferable.

Preferred onium salts constituting the photoacid generator include, for example, "Cyracure UVI-6992", "Cyracure UVI-6974" (all manufactured by Dow Chemical Japan Co., Ltd.), "Adeka Putmer SP150", and "" ADEKA OPTMER SP152 ”,“ ADEKA OPTMER SP170 ”,“ ADEKA PTMER SP172 ”(above, manufactured by ADEKA Corporation),“ IRGACURE250 ”(manufactured by Ciba Specialty Chemicals),“ CI-5102 ”,“ CI-2855 (Above, manufactured by Nippon Soda Co., Ltd.), "Sun Aid SI-60L", "Sun Aid SI-80L", "Sun Aid SI-100L", "Sun Aid SI-110L", "Sun Aid SI-180L" (above, Sanshin Kagaku) (Made by), "CPI-100P", "CPI-100A" (above, manufactured by Sun Appro Co., Ltd.), "WPI-069", "WPI-113", "WPI-116", "WPI-041", "WPI" Examples thereof include "-044", "WPI-054", "WPI-055", "WPAG-281", "WPAG-567", and "WPAG-596" (all manufactured by Wako Junyaku Co., Ltd.).

The photoacid generator is 10 parts by weight or less, and 0.01 to 10 parts by weight, based on 100 parts by weight of the total amount of the curable component contained in the resin composition containing the active energy ray-curable compound. It is preferably 0.05 to 5 parts by weight, and particularly preferably 0.1 to 3 parts by weight.

(Compound containing epoxy group or alkoxy group)
The resin composition containing an active energy ray-curable compound can contain a compound containing an epoxy group or an alkoxy group together with a photoacid generator.

Examples of the compound containing an epoxy group include a compound having one or more epoxy groups in the molecule or a compound having two or more epoxy groups in the molecule, even if it is a polymer compound (epoxy resin). Good. When these compounds are used, a compound having two or more functional groups having reactivity with an epoxy group in the molecule may be used in combination. Examples of the functional group having reactivity with the epoxy group include a carboxyl group, a phenolic hydroxyl group, a mercapto group, a primary or secondary aromatic amino group and the like. It is particularly preferable to have two or more of these functional groups in one molecule in consideration of three-dimensional curability.

Examples of the compound having one or more epoxy groups in the molecule include an epoxy resin, a bisphenol A type epoxy resin derived from bisphenol A and epichlorohydrin, and a bisphenol F type epoxy resin derived from bisphenol F and epichlorohydrin. , Bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, diphenyl ether type epoxy resin, hydroquinone type epoxy resin, naphthalene Polyfunctional epoxy resin such as type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, trifunctional type epoxy resin and tetrafunctional type epoxy resin; glycidyl ester type epoxy resin; glycidylamine type epoxy resin; hidden toin type epoxy resin; There are isocyanurate type epoxy resins; aliphatic chain epoxy resins and the like, and these epoxy resins may be halogenated or hydrogenated.

The epoxy resin products on the market are not particularly limited, but for example, JER Coat 828, 1001, 801N, 806, 807, 152, 604, 630, 871, YX8000, YX8034, YX4000, DIC manufactured by Japan Epoxy Resin Co., Ltd. Epicron 830, EXA835LV, HP4032D, HP820 manufactured by ADEKA Co., Ltd., EP4100 series, EP4000 series, EPU series manufactured by ADEKA Co., Ltd., Serokiside series manufactured by Daicel Chemical Co., Ltd. (2021, 2021P, 2083, 2085, 3000, etc.), Epoxide series, EHPE series, YD series, YDF series, YDCN series, YDB series manufactured by Nippon Steel Chemical Co., Ltd., phenoxy resin (polyhydroxypolyether synthesized from bisphenols and epichlorohydrin, which has epoxy groups at both ends; YP series, etc.), Denacol series manufactured by Nagase ChemteX Corporation, Epoxy series manufactured by Kyoeisha Chemical Co., Ltd., etc. Two or more of these epoxy resins may be used in combination.

The compound having an alkoxy group in the molecule is not particularly limited as long as it has one or more alkoxyl groups in the molecule, and known compounds can be used. Examples of such compounds include melamine compounds, amino resins, silane coupling agents and the like.

The compound containing an epoxy group or an alkoxy group is usually contained in an amount of 30 parts by weight or less and 20 parts by weight or less based on 100 parts by weight of the total amount of the curable component contained in the resin composition containing the active energy ray-curable compound. Is preferable. If the content of the compound containing an epoxy group or an alkoxy group is too large, the adhesiveness of the cured product layer to the luminance improving film may be lowered, and the impact resistance to the drop test may be deteriorated. From the viewpoint of water resistance, the compound containing an epoxy group or an alkoxy group preferably contains 2 parts by weight or more, and 5 parts by weight or more, based on 100 parts by weight of the total amount of the curable component contained in the resin composition. Is more preferable.

(Silane coupling agent)
The resin composition containing the active energy ray-curable compound can contain a silane coupling agent. In this case, the silane coupling agent is preferably an active energy ray-curable compound, but even if it is not an active energy ray-curable compound, water resistance can be imparted to the cured product layer.

Examples of the active energy ray-curable silane coupling agent include vinyl trichlorosilane, vinyl trimethoxysilane, vinyl triethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltri. Methoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3 -Methoxyloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane and the like can be mentioned. Of these, 3-methacryloxypropyltrimethoxysilane and 3-acryloxypropyltrimethoxysilane are preferable.

As the silane coupling agent that is not active energy ray curable, a silane coupling agent having an amino group is preferable. Examples of the silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropylmethyldimethoxysilane, and γ-aminopropyl. Methyldiethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ-( 2-Aminoethyl) Aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltriisopropoxysilane, γ- (2- (2-aminoethyl) aminoethyl) aminopropyltrimethoxysilane, γ-( 6-Aminohexyl) Aminopropyltrimethoxysilane, 3- (N-ethylamino) -2-methylpropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-phenyl-γ- Aminopropyltrimethoxysilane, N-benzyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, N-cyclohexylaminomethyltriethoxysilane, N-cyclohexylaminomethyldiethoxymethylsilane, Amino group-containing silanes such as N-phenylaminomethyltrimethoxysilane, (2-aminoethyl) aminomethyltrimethoxysilane, N, N'-bis [3- (trimethoxysilyl) propyl] ethylenediamine; N- (1) , 3-Dimethylbutylidene) -3- (Triethoxysilyl) -1-propaneamine and other ketimine-type silanes.

Examples of the non-active energy ray-curable silane coupling agent other than the above include 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and bis. (Triethoxysilylpropyl) Tetrasulfide, 3-isocyanatepropyltriethoxysilane, imidazolesilane and the like can be mentioned.

Of these, in order to ensure good adhesion, γ-aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane , Γ- (2-Aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl)- 1-Propanamine is preferred. As the silane coupling agent having an amino group, only one type may be used, or two or more types may be used in combination.

The silane coupling agent preferably contains 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight, based on 100 parts by weight of the total amount of the curable component contained in the resin composition containing the active energy ray-curable compound. It is more preferable to contain parts, and it is further preferable to contain 0.1 to 10 parts by weight. If the content of the silane coupling agent is too large, the storage stability of the resin composition deteriorates, and if the content of the silane coupling agent is too small, the effect of adhesive water resistance is not easily exhibited.

(Compound with vinyl ether group)
The resin composition containing the active energy ray-curable compound can contain a compound having a vinyl ether group. By containing a compound having a vinyl ether group, the adhesive water resistance between the brightness improving film and the cured product layer can be improved. It is presumed that this is because the vinyl ether group interacts with the brightness improving film to increase the adhesive force. In order to further enhance the adhesive water resistance between the brightness improving film and the cured product layer, it is preferable to use a radically polymerizable compound as the compound having a vinyl ether group. The compound having a vinyl ether group is preferably contained in an amount of 0.1 to 19 parts by weight based on 100 parts by weight of the total amount of the curable component contained in the resin composition containing the active energy ray-curable compound.

(Additive)
The resin composition containing the active energy ray-curable compound includes a (meth) acrylic oligomer, a photoacid generator, a compound containing an epoxy group or an alkoxy group, a silane coupling agent, and a compound having a vinyl ether group, in addition to the above-mentioned compounds having a vinyl ether group. Various additives may be contained as long as the object and effect of the present invention are not impaired. Examples of such additives include epoxy resins, polyamides, polyamideimides, polyurethanes, polybutadienes, polychloroprenes, polyethers, polyesters, styrene-butadiene block copolymers, petroleum resins, xylene resins, ketone resins, cellulose resins, and fluorine-based oligomers. Polymers or oligomers such as silicone-based oligomers and polysulfide-based oligomers; polymerization inhibitors such as phenothiazine and 2,6-di-t-butyl-4-methylphenol; polymerization initiators; leveling agents; wettability improvers; surface activity Agents; plasticizers; UV absorbers; inorganic fillers; pigments; dyes and the like. Among the above-mentioned additives, those having a high logPow value are preferable. The logPow value of the above-mentioned additive is preferably 2 or more, more preferably 3 or more, and most preferably 4 or more. The additive usually contains 0 to 10 parts by weight and preferably 0 to 5 parts by weight, based on 100 parts by weight of the total amount of the curable component contained in the resin composition containing the active energy ray-curable compound. It is more preferable to include ~ 3 parts by weight.

[B] Thermosetting Compound As the thermosetting compound, a thermosetting adhesive, a hot melt adhesive, or the like can be used from the viewpoint of adhesiveness between the brightness improving film and the cured product layer. Specific examples include natural rubber adhesives, α-olefin adhesives, urethane resin adhesives, ethylene-vinyl acetate resin emulsion adhesives, ethylene-vinyl acetate resin hot melt adhesives, and epoxy resin adhesives. , Vinyl chloride resin solvent adhesive, chloroprene rubber adhesive, cyanoacrylate adhesive, silicone adhesive, styrene-butadiene rubber solvent adhesive, nitrile rubber adhesive, nitrocellulose adhesive, reactive hot Melt adhesive, phenol resin adhesive, modified silicone adhesive, polyester hot melt adhesive, polyamide resin hot melt adhesive, polyimide adhesive, polyurethane resin hot melt adhesive, polyolefin resin hot melt adhesive, poly Vinyl acetate resin solvent-based adhesive, polystyrene resin solvent-based adhesive, polyvinyl alcohol-based adhesive, polyvinylpyrrolidone resin-based adhesive, polyvinyl butyral-based adhesive, polybenzimidazole adhesive, polymethacrylate resin solvent-based adhesive, melamine resin Examples thereof include based adhesives, urea resin based adhesives, resorcinol based adhesives and the like. Such an adhesive can be used alone or in combination of two or more, and a base polymer corresponding to the type of the adhesive is used.

The thermosetting adhesive develops adhesive strength by being thermoset and solidified by heating. Examples of the thermosetting adhesive include epoxy-based thermosetting adhesives, urethane-based thermosetting adhesives, acrylic-based thermosetting adhesives, and the like. The curing temperature of the thermosetting adhesive is, for example, 100 to 200 ° C.

The hot melt adhesive is melted or softened by heating, heat-sealed to the brightness improving film, and then solidified by cooling to adhere to the brightness improving film. Examples of the hot melt adhesive include rubber hot melt adhesives, polyester hot melt adhesives, polyolefin hot melt adhesives, ethylene-vinyl acetate resin hot melt adhesives, polyamide resin hot melt adhesives, and polyurethane resins. Examples include hot melt adhesives. The softening temperature (ring ball method) of the hot melt adhesive is, for example, 100 to 200 ° C. The melt viscosity of the hot melt adhesive is 180 ° C., for example, 100 to 30,000 mPa · s.

[Linearly polarized light layer]
The linearly polarized light layer has a property of transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis when unpolarized light is incident. The linearly polarizing layer preferably contains a polyvinyl alcohol (hereinafter, may be abbreviated as “PVA”)-based resin film.

Examples of the linearly polarizing layer containing the PVA-based resin film include a polyvinyl alcohol (hereinafter, may be abbreviated as "PVA") -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer system partially saponified film. Examples thereof include those obtained by subjecting a hydrophilic polymer film such as, etc. to a dyeing treatment with a bicolor substance such as iodine or a bicolor dye, and a stretching treatment. Since it is excellent in optical characteristics, it is preferable to use a linearly polarizing layer obtained by dyeing a PVA-based resin film with iodine and uniaxially stretching it.

The polyvinyl alcohol-based resin can be produced by saponifying the polyvinyl acetate-based resin. The polyvinyl acetate-based resin can be a copolymer of polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film for a linearly polarizing layer. The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. The film thickness of the polyvinyl alcohol-based resin raw film is, for example, about 10 to 100 μm, preferably about 10 to 60 μm, and more preferably about 15 to 30 μm.

As another method for producing a linear polarizing layer containing a PVA-based resin film, first prepare a base film, apply a resin solution such as a polyvinyl alcohol-based resin on the base film, and dry the base film to remove the solvent. Examples thereof include a step of forming a resin layer on the base film. A primer layer can be formed in advance on the surface of the base film on which the resin layer is formed. As the base film, a resin film such as PET can be used. Examples of the material of the primer layer include a resin obtained by cross-linking a hydrophilic resin used for the linearly polarizing layer.

Then, if necessary, the amount of solvent such as water content of the resin layer is adjusted, then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a bicolor dye such as iodine to obtain two colors. The sex dye is adsorbed and oriented on the resin layer. Subsequently, if necessary, the resin layer in which the dichroic dye is adsorbed and oriented is treated with a boric acid aqueous solution, and a washing step of washing off the boric acid aqueous solution is performed. As a result, a film of a resin layer in which the dichroic dye is adsorption-oriented, that is, a linearly polarizing layer is produced. A known method can be adopted for each step.

The uniaxial stretching of the base film and the resin layer may be performed before dyeing, during dyeing, or during boric acid treatment after dyeing, and each of these multiple steps is uniaxial. Stretching may be performed. The base film and the resin layer may be uniaxially stretched in the MD direction (film transport direction), in this case, uniaxially stretched between rolls having different peripheral speeds, or uniaxially stretched using a thermal roll. You may. Further, the base film and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction), and in this case, the so-called tenter method can be used. Further, the stretching of the base film and the resin layer may be a dry stretching in which the resin layer is stretched in the air, or a wet stretching in which the resin layer is swollen with a solvent. In order to exhibit the performance of the linearly polarized light layer, the draw ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit to the draw ratio, but it is preferably 8 times or less from the viewpoint of suppressing breakage and the like.

The linearly polarized light layer produced by the above method can be obtained by laminating a protective layer described later and then peeling off the base film.

The thickness of the linearly polarizing layer is preferably 5 μm or more, more preferably 10 μm or more, 15 μm or more, or 20 μm or more. The thickness of the linearly polarizing layer is 50 μm or less, preferably 40 μm or less, and may be 30 μm or less.

〔Polarizer〕
The linearly polarizing layer has a first protective layer or a first protective layer and a second protective layer (hereinafter, first protective layer and second protective layer) via a known pressure-sensitive adhesive layer or adhesive layer on one or both sides thereof. Can be collectively referred to as a "protective layer") to form a polarizing plate. This polarizing plate is a so-called linear polarizing plate. The protective layer that can be laminated on one side or both sides of the linearly polarizing layer is formed of, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, stretchability, and the like. Film is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether sulfone resins; polysulfone resins; polycarbonate resins; polyamides such as nylon and aromatic polyamides. Resin; Polygon resin; Polyethylene resin such as polyethylene, polypropylene, ethylene / propylene copolymer; Cyclic polyolefin resin having cyclo-based and norbornene structure (also referred to as norbornene-based resin); (meth) acrylic resin; polyallylate resin; polystyrene resin Polyvinyl alcohol resins, as well as mixtures thereof, can be mentioned. When the protective layers are laminated on both sides of the linearly polarizing layer, the resin compositions of the two protective layers may be the same or different.

The film formed from the thermoplastic resin may be surface-treated (for example, corona-treated) in order to improve the adhesion to the linearly polarizing layer, and the primer layer (also referred to as the undercoat layer) is thin. Layers may be formed.

The protective layer may be, for example, one in which the above-mentioned thermoplastic resin is stretched or one in which the above-mentioned thermoplastic resin is not stretched (hereinafter, may be referred to as “unstretched resin”). Examples of the stretching treatment include uniaxial stretching and biaxial stretching.

Examples of the pressure-sensitive adhesive layer used for laminating the protective layer on the linearly polarized light layer include the pressure-sensitive adhesive described in the first pressure-sensitive adhesive layer and the like described later. A known adhesive can be used as the adhesive layer used for laminating the protective layer on the linearly polarized light layer. Examples of the adhesive include adhesives other than pressure-sensitive adhesives (adhesives), such as water-based adhesives and active energy ray-curable adhesives. Examples of the water-based adhesive include an adhesive in which a polyvinyl alcohol-based resin is dissolved or dispersed in water. Examples of the active energy ray-curable adhesive include solvent-free active energy ray-curable adhesives containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Can be mentioned.

[Brightness improvement film]
As the brightness improving film, a polarization conversion element having a function of separating the emitted light from a light source such as a backlight into transmitted polarized light and reflected polarized light or scattered polarized light is used. The brightness improving film can improve the emission efficiency of linearly polarized light by utilizing the retrolight from the light source of reflected polarized light or scattered polarized light.

An anisotropic reflection polarizer can be used as the brightness improving film. Anisotropy reflectors transmit linearly polarized light of a predetermined polarization axis and reflect other light, such as a multilayer film of dielectrics and a multilayer laminate of layers having different refractive anisotropies. It reflects either left-handed or right-handed circularly polarized light and transmits other light, such as those exhibiting properties, an oriented film of cholesteric liquid crystal polymer or one in which the oriented liquid crystal layer is supported on a film substrate. Those showing characteristics and the like can be mentioned. The types of layers constituting the anisotropic reflection polarizer may be two or more.

Examples of the brightness improving film include a material that generates a phase difference due to stretching represented by polyethylene naphthalate, polyethylene terephthalate, and polycarbonate, an acrylic resin represented by polymethylmethacrylate, and "Arton" manufactured by JSR Corporation. A laminate obtained by uniaxially stretching a resin obtained by alternately laminating a resin having a small amount of phase difference expression such as a norbornene-based resin typified by (registered trademark) can be used. Specific examples of such a structure include "DBEF" (registered trademark), "APF-V4" (product name), "APF-V3" (product name) and "APF-V2" (product name) manufactured by 3M. First name) and so on.

The brightness improving film may be, for example, a laminate of a cholesteric liquid crystal layer and a λ / 4 plate. Specific examples of such a laminate include the trade name "PCF" manufactured by Nitto Denko KK.

The brightness improving film may be a reflective grid polarizer. Examples of the reflection grid polarizer include a metal grid reflection polarizer in which the metal is finely processed to generate reflected polarized light even in the visible light region.

The thickness of the luminance improving film is usually 5 μm or more and may be 10 μm or more, and is usually 100 μm or less, preferably 50 μm or less, and may be 35 μm or less.

[First adhesive layer, second adhesive layer, third adhesive layer]
The first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the third pressure-sensitive adhesive layer (hereinafter, these may be collectively referred to as "sticking agent layer") are layers composed of a pressure-sensitive adhesive. In the present specification, the "adhesive" exhibits adhesiveness by sticking itself to an adherend such as a polarizing plate or a liquid crystal layer, and is a so-called pressure-sensitive adhesive. .. Further, the active energy ray-curable pressure-sensitive adhesive described later can adjust the degree of cross-linking and the adhesive force by irradiating with energy rays.

As the pressure-sensitive adhesive, a conventionally known pressure-sensitive adhesive having excellent optical transparency can be used without particular limitation. For example, a pressure-sensitive adhesive having a base polymer such as an acrylic type, a urethane type, a silicone type, or a polyvinyl ether type is used. be able to. Further, it may be an active energy ray-curable pressure-sensitive adhesive, a thermosetting pressure-sensitive adhesive or the like. Among these, an adhesive based on an acrylic resin having excellent transparency, adhesive strength, removability (hereinafter, also referred to as reworkability), weather resistance, heat resistance and the like is preferable. The pressure-sensitive adhesive layer is preferably composed of a reaction product of a pressure-sensitive adhesive composition containing a (meth) acrylic resin, a cross-linking agent, and a silane compound, and may contain other components.

The pressure-sensitive adhesive layer may be formed by using an active energy ray-curable pressure-sensitive adhesive. The active energy ray-curable pressure-sensitive adhesive is a harder pressure-sensitive adhesive by blending a pressure-sensitive adhesive composition with an ultraviolet-curable compound such as a polyfunctional acrylate, forming a pressure-sensitive adhesive layer, and then irradiating the pressure-sensitive adhesive with ultraviolet rays to cure the pressure-sensitive adhesive. Layers can be formed. The active energy ray-curable pressure-sensitive adhesive has a property of being cured by being irradiated with energy rays such as ultraviolet rays and electron beams. Since the activated energy ray-curable adhesive has adhesiveness even before irradiation with energy rays, it adheres to an adherend such as an optical film or a liquid crystal layer, and is cured by irradiation with energy rays to improve adhesion. A pressure-sensitive adhesive having adjustable properties.

The active energy ray-curable pressure-sensitive adhesive generally contains an acrylic pressure-sensitive adhesive and an energy ray-polymerizable compound as main components. Usually, a cross-linking agent is further blended, and if necessary, a photopolymerization initiator, a photosensitizer, or the like can be blended.

The storage elastic modulus of the pressure-sensitive adhesive layer is preferably 0.10 to 10.0 MPa, more preferably 0.15 to 5.0 MPa at 23 ° C. When the storage elastic modulus at 23 ° C. is 0.10 MPa or more, problems such as peeling can be suppressed when a temperature change occurs, which is preferable. Further, when it is 10.0 MPa or less, the durability is less likely to be lowered due to the decrease in the adhesive strength, which is preferable. The storage elastic modulus of the pressure-sensitive adhesive layer can be measured by the method described in Examples.

The thickness of the pressure-sensitive adhesive layer is preferably 3 μm or more, and more preferably 5 μm or more. The thickness of the pressure-sensitive adhesive layer is preferably 40 μm or less, and more preferably 30 μm or less.

[Release film]
The release film covers and protects the pressure-sensitive adhesive layer or supports the pressure-sensitive adhesive layer, and has a function as a separator that can be peeled off from the pressure-sensitive adhesive layer. Examples of the release film include a film in which the surface of the base film on the pressure-sensitive adhesive layer side is subjected to a mold release treatment such as a silicone treatment. Examples of the resin material forming the base film include the same resin materials as those forming the protective layer described above. The resin film may have a one-layer structure or may be a multilayer resin film having a multilayer structure of two or more layers.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

[Measurement of thickness]
The thickness of each layer was measured using MH-15M, a digital micrometer manufactured by Nikon Corporation.

[Measurement of in-plane retardation]
In-plane retardation Re (590) at a wavelength of 590 nm of the buffer layer was measured using AxoScan (manufactured by Axometrics, Inc.).

[Measurement of tensile modulus]
A rectangular measurement sample having an MD length of 100 mm and a TD length of 20 mm was cut out from the film used as the buffer layer. The MD length was defined as the length in the direction corresponding to the absorption axis direction of the linearly polarizing layer of the composite polarizing plate. With the upper and lower grippers of the tensile tester [Autograph AG-Xplus tester manufactured by Shimadzu Corporation], sandwich both ends of the measurement sample in the MD length direction so that the distance between the grippers is 5 cm, and the temperature is 23 ° C. In an environment with a relative humidity of 55%, the measurement sample was pulled in the MD length direction at a tensile speed of 1 mm / min, and from the slope of the initial straight line in the obtained stress-strain curve, the temperature was 23 ° C. and the relative humidity was 55%. The tensile elasticity [GPa] in the MD length direction was calculated.

[High temperature durability test]
From the composite polarizing plate obtained in Examples or Comparative Examples, a sample having a size of MD length of 160 mm and a TD length of 100 mm was obtained, a release film was peeled off from this sample, and an exposed pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer) was obtained. ) Was attached to a glass plate to prepare a test piece. This test piece was autoclaved at a temperature of 50 ° C. and a pressure of 0.5 MPa for 15 minutes, and then placed in an oven at a temperature of 95 ° C. for 500 hours, and then the appearance of the test piece on the brightness improving film side was visually observed. did.

[Example 1]
(Preparation of linearly polarized light layer)
A 75 μm-thick polyvinyl alcohol film made of polyvinyl alcohol having an average degree of polymerization of about 2,400 and a saponification degree of 99.9 mol% or more was uniaxially stretched about 5 times by a dry method, and 60 while maintaining a tense state. After immersing in pure water at ° C. for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the mixture was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a linearly polarized light layer having a thickness of 28 μm in which iodine was adsorbed and oriented on polyvinyl alcohol.

(Adhesive preparation)
50 g of a modified PVA resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Corporation: Gosenex Z-410) was dissolved in 950 g of pure water, heated at 90 ° C. for 2 hours and then cooled to room temperature to obtain a PVA solution. .. Next, a PVA solution, maleic acid, glyoxal, and pure water were blended so that each compound had the following concentration to prepare a PVA-based adhesive.
PVA 3.0% by weight
Maleic acid 0.01% by weight
Glyoxal 0.15% by weight

(Preparation of polarizing plate)
The above adhesive is applied to one surface of the linearly polarizing layer obtained above, and a first protective layer (a triacetyl cellulose film having a thickness of 40 μm [trade name “KC4UYW” manufactured by Konica Minolta Opto Co., Ltd.]) is attached. , The above adhesive is applied to the other surface, a second protective layer (acrylic resin film with a thickness of 40 μm [trade name “HX-40NE” manufactured by Toyo Steel Co., Ltd.]) is attached, dried and polarized. A plate was made. When these materials were bonded, a corona treatment was performed on the bonded surface of each material.

(Preparation of composite polarizing plate)
A commercially available sheet-like acrylic pressure-sensitive adhesive having a thickness of 25 μm is bonded to the first protective layer side of the polarizing plate obtained above to form the first pressure-sensitive adhesive layer. A triacetyl cellulose film [trade name "TJ40UL" manufactured by Fujifilm Co., Ltd.] as a buffer layer was attached to the opposite side. Subsequently, a commercially available sheet-like acrylic pressure-sensitive adhesive having a thickness of 25 μm is bonded to the side of the buffer layer opposite to the first pressure-sensitive adhesive layer side to form a second pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer is buffered. A brightness improving film (“AFP-V3 HCS” manufactured by 3M Co., Ltd.) was attached to the side opposite to the layer side. Further, on the second protective layer side of the polarizing plate, a pressure-sensitive adhesive layer (referred to as a third pressure-sensitive adhesive layer) of an acrylic pressure-sensitive adhesive having a thickness of 25 μm is formed on a release film (thickness 38 μm, polyethylene terephthalate film). The adhesive layer side of the agent sheet was bonded. As described above, the release film, the third pressure-sensitive adhesive layer, the polarizing plate (the second protective layer, the linearly polarized light layer, and the first protective layer are laminated in this order from the third pressure-sensitive adhesive layer side), the first pressure-sensitive adhesive layer, A composite polarizing plate in which a buffer layer, a second pressure-sensitive adhesive layer, and a brightness improving film were laminated in this order was obtained. At the time of bonding each material, a corona treatment was performed on the bonded surface of each material.

The in-plane retardation Re (590) of the triacetyl cellulose film used as the buffer layer at a wavelength of 590 nm was measured and found to be 0.5 nm. The tensile elastic modulus of the buffer layer at a temperature of 23 ° C. and a relative humidity of 55% was 5200 MPa. Further, when the obtained composite polarizing plate was subjected to a high temperature durability test, no wrinkles were observed on the brightness improving film, and the appearance of the composite polarizing plate was good.

[Comparative Example 1]
A release film, a third pressure-sensitive adhesive layer, and a polarizing plate (from the third pressure-sensitive adhesive layer side, a second protective layer, linearly polarized light) in the same manner as in Example 1 except that a buffer layer and a second pressure-sensitive adhesive layer are not provided. A composite polarizing plate in which a layer, a first protective layer were laminated in this order), a first pressure-sensitive adhesive layer, and a brightness improving film were laminated in this order was obtained. When the obtained composite polarizing plate was subjected to a high temperature durability test, many fine wrinkles were confirmed at the end on the long side of the brightness improving film.

1, 2, composite polarizing plate, 5, 6 liquid crystal display device, 10 polarizing plate, 11 linear polarizing layer, 12 first protective layer, 13 second

protective layer

15a, 15b buffer layer, 18 brightness improving film, 31 first adhesive Layer, 32 second adhesive layer, 33 third adhesive layer, 35 release film, 41 liquid crystal cell, 42 backlight.

Claims

A composite polarizing plate having a polarizing plate having a protective layer on at least one side of the linearly polarizing layer and a brightness improving film.
The first pressure-sensitive adhesive layer, the buffer layer, and the brightness improving film are laminated in this order on the protective layer side of the polarizing plate.
A composite polarizing plate having a tensile elastic modulus of 1.5 GPa or more at a temperature of 23 ° C. and a relative humidity of 55% of the buffer layer.
The composite polarizing plate according to claim 1, wherein the buffer layer and the brightness improving film are bonded to each other via a second pressure-sensitive adhesive layer.
The composite polarizing plate according to claim 1 or 2, wherein the buffer layer is a resin film.
The composite polarizing plate according to claim 3, wherein the resin film includes a film made of at least one resin selected from the group consisting of a cellulose ester resin, a (meth) acrylic acid resin, and a cyclic olefin resin.
The composite polarizing plate according to claim 1, wherein the buffer layer is in direct contact with the brightness improving film.
The composite polarizing plate according to claim 1 or 5, wherein the buffer layer is a cured product layer of a resin composition containing a curable component.
The composite polarizing plate according to claim 6, wherein the curable component contains an active energy ray-curable compound.
The composite polarizing plate according to any one of claims 1 to 7, wherein the in-plane retardation Re (590) of the buffer layer at a wavelength of 590 nm is 20 nm or less.
The composite polarizing plate according to any one of claims 1 to 8, wherein the first pressure-sensitive adhesive layer is a bonding layer of the protective layer of the polarizing plate and the buffer layer.
The composite polarizing plate according to any one of claims 1 to 9, wherein the polarizing plate has the protective layers on both sides of the linearly polarizing layer.
The composite polarizing plate according to any one of claims 1 to 10, which has a third pressure-sensitive adhesive layer on the side of the polarizing plate opposite to the brightness improving film side.
The composite polarizing plate according to claim 11, which has a release film on the side of the third pressure-sensitive adhesive layer opposite to the polarizing plate side.
A liquid crystal display device comprising the composite polarizing plate according to any one of claims 1 to 12 and a liquid crystal cell.
In addition, it has a backlight,
The liquid crystal display device according to claim 13, wherein the composite polarizing plate is arranged between the liquid crystal cell and the backlight so that the brightness improving film side is the backlight side.