WO2013042422A1 - Polarizing plate and liquid crystal display device - Google Patents

Abstract

The purpose of the present invention is to provide a polarizing plate in which when attaching an optical film and a polarizer using a photo curable adhesive, attachment is achieved without curling and with sufficient adherence, wherein the polarizing plate combines both excellent light-diffusing properties and light-transmitting properties. A further purpose is to provide a liquid crystal display device equipped with the polarizing plate. This polarizing plate is a polarizing plate in which an optical film containing at least two kinds of resin is attached to a polarizer using a photo curable adhesive, and is characterized in that the two surfaces of the optical film both have a sea-island structure and the arithmetic mean roughness Ra of the two surfaces is within the range of 0.03-1.5μm.

Description

Polarizing plate and liquid crystal display device

The present invention relates to a polarizing plate and a liquid crystal display device provided with the polarizing plate.

A liquid crystal display device (hereinafter also referred to as “LCD”) is generally composed of a backlight unit, a liquid crystal cell, and a polarizing plate. The polarizing plate usually comprises a protective film for polarizing plate (hereinafter also referred to as “optical film”) and a polarizer (also referred to as “polarizing film”). As the polarizer, a polyvinyl alcohol film dyed with iodine and stretched is often used, and a protective film for a polarizing plate is bonded to both surfaces. As a protective film for a polarizing plate, a cellulose triacetate (TAC) film having excellent moisture permeability and excellent adhesion to a polarizer is generally used.

The cellulose triacetate film can be hydrophilized by alkali saponification treatment, and can be adhered to a polarizer with an inexpensive aqueous adhesive. Therefore, the cellulose acetate film is particularly suitable as a polarizing plate protective film, and is an indispensable member for liquid crystal display devices.

By the way, in recent years, a cellulose acetate film has been produced using a photo-curable adhesive so that a polarizing plate can be produced at a high speed without performing the alkali saponification treatment as described above (for example, patents). Reference 1 to 4).

However, when a photocurable adhesive is used in the examination process of the present inventor, a large amount of heat is generated when the photocurable adhesive is cured in the production process of the polarizing plate. It has been found that the film has a problem that the polarizing plate curls due to low heat resistance, and that the adhesion with the polarizer is not sufficient.

On the other hand, in recent years, with the trend of thinning and cost reduction, the number of liquid crystal display devices has been reduced, and liquid crystal display devices having a configuration that does not use a light diffusion sheet have been developed. For example, as an alternative to the light diffusion sheet, an optical film having diffusibility on the surface of the backlight side polarizing plate has been used.

In Patent Documents 5 and 6, a light diffusion film having a sea-island structure in which a dope composed of a plurality of resins is cast on a support and phase-separated, or a mixed solution of a plurality of resins is applied on the support film. The produced light diffusion film is disclosed.

However, it has been found that there is a new problem in that when the film is used as a protective film for a polarizing plate while maintaining the light diffusibility, the light transmittance is lowered and the luminance when the display device is formed is lowered.

In addition, a method for producing a light diffusable optical film by applying a mixed solution of a plurality of resins on a support film must be applied after film formation, and therefore the market is currently undergoing cost reduction. There is also a problem that it is not appropriate.

International Publication No. 2006/106639 Pamphlet JP 2010-39298 A JP 2009-244860 A JP 2009-211057 A JP 2000-239535 A JP 2002-250806 A

The present invention has been made in view of the above-described problems and situations, and its solution is that when an optical film and a polarizer are bonded together using a photocurable adhesive, no curling occurs. The present invention provides a polarizing plate that is bonded with sufficient adhesion, and has both excellent light diffusibility and light transmittance. Moreover, it is providing the liquid crystal display device provided with the said polarizing plate.

In order to solve the above-mentioned problems, the present inventor, in the process of studying a method for solving a problem when using a photo-curable resin, the specific film having a sea-island structure is in close contact with the polarizer, resulting in curling. The present invention has been found out that it has no light diffusivity and light transmittance.

That is, the said subject which concerns on this invention is solved by the following means.
1. An optical film containing two or more kinds of resins is a polarizing plate bonded to a polarizer with a photocurable adhesive, the two surfaces of the optical film both have a sea-island structure, and the two surfaces A polarizing plate characterized by having an arithmetic average roughness Ra of 0.03 to 1.5 μm.
2. The optical film contains at least an acrylic resin and a cellulose acylate resin as two or more kinds of resins, and a mass ratio of the acrylic resin and the cellulose acylate resin is within a range of 51:49 to 90:10. The polarizing plate as described in item 1, wherein
3. The cellulose acylate resin has at least two kinds of cellulose acylates, ie, a cellulose acylate resin having an average total carbon atom number of acyl groups of less than 6.0 and a cellulose acylate resin having a number of 6.0 or more per glucose unit. 3. A polarizing plate according to item 2, containing a rate resin.
4). The cellulose acylate resin has at least an acetyl group or a propionyl group as the acyl group, and the average total number of carbon atoms of the acyl group is less than 6.0 per glucose unit. 4. The polarizing plate according to the second or third item, wherein the degree of propionyl group substitution is 1.0 or less.
5. The polarizing plate according to any one of Items 1 to 4, wherein the photocurable adhesive is a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator.
6). Any one of Items 1 to 5, wherein the image clarity of the optical film is in a range of 0.8 to 5.0% in measurement using an optical comb having a width of 0.25 mm. A polarizing plate according to claim 1.
7). A liquid crystal display device comprising the polarizing plate according to any one of items 1 to 6 on a backlight source side with respect to a liquid crystal cell.

When the optical film and the polarizer are bonded using a photocurable adhesive by the above means of the present invention, the polarizing plate is bonded with sufficient adhesion without causing curling. It is possible to provide a polarizing plate having both light diffusibility and light transmittance. In addition, a liquid crystal display device including the polarizing plate can be provided.

In addition, by providing the polarizing plate of the present invention in a liquid crystal display device, moire can be eliminated without reducing the front luminance.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

When a solvent of a uniform polymer solution in which two or more kinds of resins are mixed is evaporated to be concentrated and saturated, fine phase separation (microphase separation) occurs. Thereafter, by stretching the formed resin film, a resin component having a high glass transition temperature rises, and a sea-island structure having an uneven structure is formed.

Thus, it is presumed that a light transmissive film having a diffusion function was formed. In addition, it is surmised that the surface uneven energy structure increases the surface free energy, improves the leveling property (uniform coating property) of the photocurable adhesive, and improves the adhesion to the polarizer. Furthermore, it is presumed that the heat resistance of the optical film is increased by mixing a resin component having a high glass transition temperature, and the polarizing plate is not curled even when a photo-curable adhesive is used.

The figure which showed typically an example of the dope preparation process, casting process, and drying process of a solution casting film forming method The figure which showed the example of the structure of the conventional liquid crystal display device typically The figure which showed the example of the structure of the conventional liquid crystal display device typically The figure which showed typically the structural example of the liquid crystal display device using the polarizing plate of this invention. The figure which showed typically the structural example of the liquid crystal display device using the polarizing plate of this invention.

The polarizing plate of the present invention is a polarizing plate in which an optical film containing two or more kinds of resins is bonded to a polarizer with a photocurable adhesive, and both surfaces of the optical film have a sea-island structure. The arithmetic mean roughness Ra of the two surfaces is in the range of 0.03 to 1.5 μm. This feature is a technical feature common to the inventions according to claims 1 to 7.

As an embodiment of the present invention, from the viewpoint of the effect of the present invention, the optical film contains at least an acrylic resin and a cellulose acylate resin as two or more resins, and the acrylic resin and the cellulose acylate. The resin mass ratio is preferably in the range of 51:49 to 90:10. The cellulose acylate resin has at least two cellulose acylate resins having an average total carbon atom number of acyl groups of less than 6.0 and a cellulose acylate resin of 6.0 or more per glucose unit. It is preferable that a cellulose acylate resin is contained because an effect of forming a sea-island structure is obtained.

Furthermore, in the present invention, the cellulose acylate resin has at least an acetyl group or a propionyl group as the acyl group, and the average total number of carbon atoms of the acyl group is less than 6.0 per glucose unit. It is preferable that the propionyl group substitution degree of the cellulose acylate resin is 1.0 or less. Thereby, the effect that the sea-island structure (phase separation) is formed is obtained. Moreover, it is preferable that the said photocurable adhesive agent is a photocurable adhesive agent containing an epoxy compound and a cationic polymerization initiator.

The image definition of the optical film according to the present invention is preferably in the range of 0.8 to 5.0% in the measurement using an optical comb having a width of 0.25 mm.

The polarizing plate of the present invention can be suitably provided in a liquid crystal display device.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

(Outline of polarizing plate of the present invention)
The polarizing plate of the present invention is a polarizing plate in which an optical film containing two or more kinds of resins is bonded to a polarizer with a photocurable adhesive, and both surfaces of the optical film have a sea-island structure. It is characterized by that.

In the present application, the “sea-island structure” means that when a plurality of (for example, two) resin components that are incompatible with each other are mixed, the higher-order structure of the mixture is a phase in which one of the resin components is continuous. The other is a structure in which islands or particles are dispersed. That is, it means a structure formed by one resin being a continuous phase (matrix) corresponding to the sea and the other being a dispersed phase corresponding to the island. The “two surfaces of the optical film” means two surfaces on the front and back of the optical film.

As the resin that can be used for the optical film according to the present invention, as described later, various resins such as cellulose ester resin, acrylic resin, cyclic olefin resin, and polycarbonate resin that are used in conventional optical films may be used. it can.

From the viewpoint of expression of the effects of the present invention, the optical film according to the present invention contains at least an acrylic resin and a cellulose acylate resin as two or more resins, and a mass ratio of the acrylic resin and the cellulose acylate resin. Is preferably in the range of 51:49 to 90:10.

The cellulose acylate resin has at least two cellulose acylate resins having an average total carbon atom number of acyl groups of less than 6.0 and a cellulose acylate resin of 6.0 or more per glucose unit. It is preferable that a cellulose acylate resin is contained because an effect of forming a sea-island structure is obtained.

Furthermore, in the present invention, the cellulose acylate resin has at least an acetyl group or a propionyl group as an acyl group, and the average total number of carbon atoms of the acyl group is less than 6.0 per glucose unit. The propionyl group substitution degree of the acylate resin is preferably 1.0 or less.

Among these two types of cellulose acylate resins, cellulose acylate having mainly an acyl group having an average total carbon number of less than 6.0 is a resin which is a main component constituting a dispersed phase corresponding to an island. On the other hand, the cellulose acylate having an acyl group having an average total carbon number of 6.0 or more is more compatible with the acrylic resin than the cellulose acylate having an acyl group having an average total carbon number of less than 6.0. It is added in order to moderate some discontinuity in the boundary region between the continuous phase and the dispersed phase and to prevent peeling at the interface.

In addition, in this application, the average total carbon atom number of the acyl group which cellulose acylate has is the number of carbon atoms of each substituent (for example, acetyl group) in the acyl group substitution degree such as propionyl group substitution degree and butyryl group substitution degree. Is the sum of the number of carbon atoms obtained by multiplying by 2), the number of carbon atoms of the propionyl group is 3, and the number of butyryl groups is 4).

The arithmetic average roughness Ra of the two surfaces of the optical film according to the present invention needs to be in the range of 0.03 to 1.5 μm. A preferred range is 0.4 to 1.4 μm. In this application, “the arithmetic average roughness Ra of the two surfaces is in the range of 0.03 to 1.5 μm” means that the arithmetic average roughness is within the range in the comprehensive evaluation of the two front and back surfaces of the optical film. It means that there is. That is, the arithmetic average value considering the roughness of the two surfaces is within the range.
The optical film according to the present invention preferably has different arithmetic average roughness Ra on each of the two surfaces, and the arithmetic average roughness Ra based on JIS B0601-2001 on at least one surface is 0.05 to It is preferable to be in the range of 2.0 μm. If the Ra value is 0.05 μm or more, it can be determined whether the scattered light is sufficient, and moire fringes can be eliminated. If the value of Ra is 2.0 μm or less, it is possible to effectively suppress a decrease in front luminance when a display device is formed.
In addition, when the arithmetic average roughness Ra of the two surfaces is different, it is preferable that the polarizer is in close contact with the surface having the smaller arithmetic average roughness Ra.

As means for controlling the arithmetic average roughness Ra within a predetermined range, the selection of the resin constituting the sea and the resin constituting the island, the stretching ratio of the web containing the resin, the adjustment by the stretching conditions such as the stretching temperature, etc. Can be mentioned.

In the present invention, the image definition of the optical film is in the range of 0.8 to 5.0% and the total light transmittance is 91.0% in the measurement using an optical comb having a width of 0.25 mm. The above is preferable. Further, the image definition is preferably in the range of 0.9 to 2.5%.

In the present application, the image clarity (also referred to as “image clarity”) of the optical film is a value obtained by measurement by a transmission method based on JIS K7374: 2007. For the total light transmittance, the average value of the light transmittance in the light wavelength region of 450 to 650 nm was defined as the total light transmittance.

Examples of means for controlling the image definition within a predetermined range include selection of a resin that constitutes the sea and a resin that constitutes the island, an adjustment according to stretching conditions such as a stretching ratio of the web containing the resin, and a stretching temperature. Further, as a means for controlling the total light transmittance to a predetermined value or higher, selection of a resin having a resin refractive index difference of 0.08 or less can be cited.

In the present invention, the glass transition temperature of the resin (for example, cellulose acylate resin) as the main component constituting the dispersed phase (island) of the sea-island structure, and the resin as the main component constituting the continuous phase (sea) ( For example, the difference between the glass transition temperature of the acrylic resin and the glass transition temperature is more than 10 ° C., and the difference in refractive index between the resin constituting the sea (for example, acrylic resin) and the resin constituting the island (for example, cellulose acylate resin) is 0.08 or less is preferable.

<acrylic resin>
An example of a preferred embodiment of the optical film according to the present invention is an embodiment containing at least an acrylic resin and a cellulose acylate resin. In this case, the mass ratio of the acrylic resin and the cellulose acylate resin is preferably in the range of 51:49 to 90:10.

The acrylic resin used in the present invention includes a methacrylic resin. The resin is not particularly limited, but a resin comprising 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith is preferable.

Other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and other α, β -Unsaturated group-containing divalent carboxylic acids such as unsaturated acids, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, and α, β-unsaturated materials such as acrylonitrile and methacrylonitrile. Examples thereof include nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These can be used alone or as a copolymer in combination of two or more monomers.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin used in the optical film according to the present invention has a weight average molecular weight (Mw) of 80000 or more, particularly from the viewpoint of improving brittleness as an optical film and improving transparency when used in combination with a cellulose acylate resin. It is preferable. When the weight average molecular weight (Mw) of the acrylic resin is less than 80000, sufficient brittleness improvement cannot be obtained, and compatibility with the cellulose acylate resin deteriorates. The weight average molecular weight (Mw) of the acrylic resin is more preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 100,000 to 600,000, and most preferably in the range of 150,000 to 400,000. Although the upper limit of the weight average molecular weight (Mw) of an acrylic resin is not specifically limited, It is a preferable form that it shall be 1 million or less from a viewpoint on manufacture.

The weight average molecular weight (Mw) of the acrylic resin can be measured using gel permeation chromatography (GPC).

GPC measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

As the acrylic resin used in the optical film according to the present invention, a commercially available product can also be used. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

<Cellulose acylate resin>
The cellulose acylate resin according to the present invention is a resin in which a large number of β-glucose molecules are linearly polymerized by β-1,4-glycoside bonds. The glucose unit constituting cellulose by the β-1,4-glycoside bond has free hydroxy groups (hydroxyl groups) at the 2nd, 3rd and 6th positions. Therefore, the cellulose acylate resin according to the present invention is a polymer (resin) obtained by esterifying part or all of these hydroxy groups (hydroxyl groups) with acyl groups.

The cellulose acylate resin according to the present invention has at least two types of cellulose acylate resin having an average total carbon atom number of acyl group of less than 6.0 and a cellulose acylate resin of 6.0 or more per glucose unit. The cellulose acylate resin is preferably contained.

Among these two types of cellulose acylate resins, cellulose acylate resins having an acyl group having an average total carbon number of less than 6.0 are mainly resins that constitute a dispersed phase corresponding to an island.

In the present invention, from the viewpoint of reducing compatibility with an acrylic resin and forming a dispersed phase, the propionyl of the cellulose acylate resin in which the average total number of carbon atoms of the acyl group is less than 6.0 per glucose unit The group substitution degree is preferably 1.0 or less. The degree of acetyl group substitution is preferably in the range of 1.5 to 3.0.

On the other hand, the cellulose acylate resin having an acyl group having an average total carbon number of 6.0 or more is more compatible with the acrylic resin than the cellulose acylate resin having an acyl group having an average total carbon atom number of less than 6.0. Because of its relatively good quality, it is added to moderate some discontinuity in the boundary region between the continuous phase and the dispersed phase and to prevent delamination at the interface.

In addition, the propionyl group substitution degree of the cellulose acylate resin having an acyl group having an average total carbon number of 6.0 or more is preferably in the range of 1.0 to 2.7. The degree of acetyl group substitution is preferably in the range of 0.1 to 2.0.

In addition, in this application, the average total carbon atom number of the acyl group which cellulose acylate resin has is the carbon atom number of each substituent in acetyl group substitution degree, such as propionyl group substitution degree and butyryl group substitution degree as above-mentioned. (For example, the total number of carbon atoms obtained by multiplying the number of carbon atoms of the acetyl group is 2, the number of carbon atoms of the propionyl group is 3, and the number of butyryl groups is 4).

For example, when the average total carbon atom number of the acyl group is A, the acetyl group substitution degree is X, the propionyl group substitution degree is Y, and the butyryl group substitution degree is Z, the average total carbon atom number A is represented by the following formula. .

A = 2 × X + 3 × Y + 4 × Z
The “acyl group substitution degree” represents the total of the ratios of esterified hydroxy groups (hydroxyl groups) at the 2nd, 3rd and 6th positions of glucose as a repeating unit. Specifically, the substitution degree is 1 when the hydroxy groups (hydroxyl groups) at the 2-position, 3-position and 6-position of cellulose are esterified 100%. Therefore, when all of the 2nd, 3rd and 6th positions of the cellulose are 100% esterified, the degree of substitution is 3 at the maximum.

In the present application, “acyl group substitution degree” refers to an acyl group substitution degree in which the acyl group substitution degree of a plurality of glucose units constituting cellulose acylate is expressed as an average value per unit. In the present application, the average value of the degree of substitution of a specific acyl group, for example, an acetyl group, a propionyl group, etc. is expressed as “average” as “acetyl group substitution degree”, “propionyl group substitution degree”, respectively. It will be expressed for short.

The method for measuring the degree of acyl group substitution can be measured according to ASTM-D817-96.

Examples of the acyl group include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group. Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like.

Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group.

In the case of an aliphatic acyl group, the number of carbon atoms is preferably 2 to 6 and more preferably 2 to 4 from the viewpoint of productivity and cost of cellulose synthesis. Moreover, it is preferable that the part which is not substituted by the acyl group exists normally as a hydroxyl group (hydroxyl group).

There are no particular limitations on cellulose as a raw material for cellulose acylate, but examples include cotton linters, wood pulp (derived from conifers and hardwoods), and kenaf. Moreover, the cellulose acylate obtained from them can be mixed and used at an arbitrary ratio.

The cellulose acylate resin according to the present invention can be produced by a known method.

Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, the three hydroxy groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose acylate resin such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, a cellulose acylate resin having a desired degree of acyl group substitution is synthesized by hydrolyzing the cellulose triester. Thereafter, a cellulose acylate resin is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

Specifically, it can be synthesized with reference to the methods described in JP-A Nos. 10-45804 and 2009-161701.

The cellulose acylate used in the optical film according to the present invention is not particularly limited as long as the above conditions are satisfied. The ester group is a linear or branched carboxylic acid ester having about 2 to 22 carbon atoms. These carboxylic acids may form a ring or may be an ester of an aromatic carboxylic acid. In addition, these carboxylic acids may have a substituent. The cellulose acylate is particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

Specific examples of preferred cellulose acylate resins include cellulose acetate, propionate groups or butyrate groups in addition to acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Mention may be made of mixed fatty acid esters of bound cellulose. Of these, cellulose acetate propionate is particularly preferred.

The cellulose acylate resin having an acyl group having an average total carbon number of 6.0 or more used for the optical film according to the present invention is an acyl group particularly from the viewpoint of transparency when improved in brittleness or compatible with an acrylic resin. An acyl group having a total substitution degree (T) of 2.0 to 3.0, an acyl group having 3 to 7 carbon atoms and a substitution degree of 1.2 to 3.0, and having 3 to 7 carbon atoms The degree of substitution is preferably 2.0 to 3.0. That is, the cellulose acylate resin according to the present invention is a cellulose acylate resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used. Is preferably used.

When the total substitution degree of the acyl group of the cellulose acylate resin is within the range of 2.0 to 3.0, that is, the residual degree of the hydroxy group at the 2, 3, 6 position of the cellulose acylate molecule is less than 1.0. In such a case, the compatibility between the cellulose acylate resin and the acrylic resin is increased, and when used as an optical film, the transparency is increased.

Even when the total substitution degree of the acyl group is less than 2.0, if the substitution degree of the acyl group having 3 to 7 carbon atoms is more than 1.2, compatibility is improved and brittleness is increased. preferable. For example, even when the total substitution degree of the acyl group is less than 2.0, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is low, and the substitution degree of the acyl group having 3 to 7 carbon atoms is low. When exceeding 1.2, compatibility becomes high and transparency improves.

In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

When the cellulose acylate resin has an aromatic acyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably 0 to 5. Also in this case, the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is preferably 1.2 to 3.0.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

In the cellulose acylate resin as described above, a structure having at least one kind of an aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used in the cellulose acylate resin according to the present invention.

The cellulose acylate resin used in the optical film according to the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. That is, those having an acyl group having 3 or 4 carbon atoms as a substituent are preferred.

Among these, particularly preferred cellulose acylate resins are cellulose acetate propionate and cellulose propionate.

The weight average molecular weight (Mw) of the cellulose acylate resin used in the optical film according to the present invention is 75,000 or more, particularly from the viewpoint of improving compatibility with acrylic resin and brittleness, and is in the range of 75,000 to 300,000. Preferably, it is more preferably in the range of 100,000 to 240,000, particularly preferably 160000 to 240000. When the weight average molecular weight (Mw) of the cellulose acylate resin is less than 75,000, the effect of improving heat resistance and brittleness is not sufficient, and the effect of the present invention cannot be obtained. The weight average molecular weight Mw of cellulose acylate can be measured using the gel permeation chromatography (GPC).

(Plasticizer)
In the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

Of these, polyester-based and phthalate-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, and preferably in the range of 600 to 3000, which has a large plasticizing effect.

Also, the viscosity of the plasticizer has a correlation with the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the range of 200 to 5000 MPa · s (25 ° C.) is preferable because of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the optical film according to the present invention. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

(UV absorber)
The optical film according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine Examples include hybrid systems having both structures, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

(Other additives)
Furthermore, various antioxidants can also be added to the optical film according to the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

For the optical film according to the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphate esters, halogen-containing condensed phosphonate esters, halogen-containing phosphite esters, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

(Outline of optical film manufacturing method)
The method for producing an optical film according to the present invention is a method for producing an optical film having a sea-island structure composed of a continuous phase corresponding to the sea and a dispersed phase corresponding to an island, and is a resin that is a main component constituting the island B, for example, the difference between the glass transition temperature Tg (B) of the cellulose acylate resin and the glass transition temperature Tg (A) of the resin A, eg, an acrylic resin, which is the main component constituting the sea (Tg (B) −Tg ( A)) is more than 10 ° C., the difference in refractive index between the resin A and the resin B is 0.08 or less, and the production method has the following steps (a) to (d) preferable.
Step (a): Step of forming a dope containing the resin A and the resin B (b): Step of casting the dope on a casting support to form a web (c): The web Drying step evaporating the organic solvent from step (d): the web is stretched at a magnification within a range of 1.03-1.20 times at a temperature at which the stretching temperature T satisfies Tg (A) <T <Tg (B). Specifically, the glass transition temperature Tg (B) of the resin B as the main component constituting the island is higher than the glass transition temperature of the resin A as the main component constituting the sea, and the difference between the two (Tg (B) -Tg (A)) is preferably more than 10 ° C. Moreover, it is preferable that it is a manufacturing method of the optical film whose refractive index difference of resin A and resin B is 0.08 or less. Further, it is preferable that the production method includes the steps (a) to (d).

According to the production method of the present invention, it is possible to provide an optical film having a light diffusing ability that overcomes the brittleness problem that has been a problem with conventional scattering films made of resin blends. In particular, when used as a protective film for a backlight side polarizing plate, it is possible to provide an image display device with excellent image quality in which moire fringes are eliminated without reducing the front luminance.

<Glass transition temperature of resin A and resin B and stretching temperature in stretching process>
In the present invention, the difference (Tg (B) −) between the glass transition temperature Tg (B) of the resin B as the main component constituting the island and the glass transition temperature Tg (A) of the resin A as the main component composing the sea. Tg (A)) is preferably more than 10 ° C. Furthermore, it is preferable to extend | stretch so that the temperature T in an extending process may satisfy | fill Tg (A) <T <Tg (B).

As a result, by extending the resin that constitutes the sea while the island structure is not oval in shape but in a round shape, the protruding state of the island structure can be controlled, and sufficient moire can be achieved without causing a decrease in transmittance. A resolution ability can be imparted.

From the viewpoint of preventing failure such as peeling at the interface between the sea structure and the island structure, and preventing reduction in transmittance and front luminance, a more preferable range is the difference in glass transition temperature between resin B and resin A (Tg (B) −Tg ( A)) is 15 ° C. or higher, that is, (Tg (B) −Tg (A)) ≧ 15 (° C.).

In addition, in this application, a glass transition temperature is the meaning also including apparent Tg in case resin contains a solvent. The glass transition temperature of the resin is the midpoint glass transition temperature (Tmg) determined by measuring at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer). be able to.

Further, the film made by the production method according to the present invention has a sea-island structure due to phase separation of the resin, and has an uneven shape derived from the sea-island structure. In order to observe the shape of the island, Olympus 3D laser microscope LEXT OLS4000 or the like can be used.

<Refractive index difference between resin A and resin B>
In the present invention, the difference between the refractive index (A) of the resin A as the main component constituting the sea and the refractive index (B) of the resin B as the main component constituting the island is 0.08 or less. That is, | refractive index (A) −refractive index (B) | ≦ 0.08.

More preferably, | refractive index (A) −refractive index (B) | ≦ 0.03. By making both refractive index into this range, it can suppress that the internal haze of an optical film increases, and when it is set as a display apparatus, it can suppress that front luminance falls.

In the present invention, the refractive index means an average refractive index, and the refractive index of the resin A and the refractive index of the resin B are measured using Abbe's refractometer or the like by producing a film made of each resin. be able to.

<Stretch ratio in stretching process>
In the present invention, the draw ratio in the drawing step is preferably in the range of 1.03 to 1.20 times at a temperature at which the drawing temperature T satisfies Tg (A) <T <Tg (B).

If the draw ratio is 1.03 times or more, the effect of the present invention is exhibited. If it is 1.20 times or less, it can suppress that front brightness falls, when a haze value raises and it is set as a display apparatus.

(Optical film manufacturing method)
The method for producing an optical film according to the present invention is a method for producing an optical film having a sea-island structure composed of a continuous phase corresponding to the sea and a dispersed phase corresponding to an island, and is a resin that is a main component constituting the island The difference between the glass transition temperature Tg (B) of B (cellulose acylate resin) and the glass transition temperature Tg (A) of the resin A (acrylic resin) as the main component constituting the sea (Tg (B) −Tg ( A)) is more than 10 ° C., the difference in refractive index between the resin A and the resin B is 0.08 or less, and the production method of the embodiment having the steps (a) to (d). preferable.

In the present invention, it is preferable that the stretching speed in the stretching step determined by the following formula (I) is in the range of 20 to 300% / min.

Formula (I): Stretching speed (% / min) = {(width dimension after stretching / width dimension before stretching) -1} × 100 (%) / time required for stretching (min)
By manufacturing by the said method, the optical film which concerns on this invention can be produced with an easy process without the process contamination by fine particle drop-off.

Hereinafter, the method for forming an optical film according to the present invention will be described in more detail, but the present invention is not limited thereto.

As a method for forming an optical film according to the present invention, solution casting by the following casting method is preferable.

FIG. 1 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

(1) Dissolution Step In an organic solvent mainly composed of a good solvent for the resin to be used, the resin B constituting the island, the resin A constituting the sea, and other additives are dissolved in the dissolution vessel while stirring, and the dope is dissolved. It is a process of forming.

For dissolving the resin, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557, or Various dissolution methods such as a method using a cooling dissolution method as described in JP-A-9-95538 and a method using a high pressure as described in JP-A-11-21379 can be used. A method in which pressure is applied as described above is preferable.

(Organic solvent)
In the method for producing an optical film according to the present invention, an organic solvent useful for forming a dope in the case of producing by a solution casting method is one that can simultaneously dissolve a plurality of resins and other additives to be used. Can be used without limitation.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy, and when the proportion of alcohol is small, the role of promoting the dissolution of the resin in a non-chlorine organic solvent system also is there.

In particular, a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in a resin A constituting an ocean and a resin B constituting an island is at least 15 to 45% by mass in total. A dissolved dope composition is preferred.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

After dissolving the resin and additives, it is filtered with a filter medium, defoamed, and sent to the next process with a liquid feed pump. For the filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

Also, a pellet obtained by kneading the resin A constituting the sea and the resin B constituting the island in advance can be preferably used.

(2) Casting process An endless metal belt 31, such as a stainless steel belt, or a rotating metal drum, which feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely. The dope is cast from the pressure die slit to the casting position on the metal support.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

(3) Solvent evaporation step A step of casting a web (a dope is cast on a casting support and the formed dope film is called a “web”) on the casting support to evaporate the solvent. It is.

To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used.

In order to adjust the amount of residual solvent in the subsequent peeling step, the temperature of the liquid brought into contact with the back surface of the support in this solvent evaporation step, the contact time with the support, and the like may be adjusted as appropriate.

(4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 ° C., more preferably 11 to 30 ° C.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 5 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. .

The amount of residual solvent used in the present invention can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at an arbitrary point, and N is the mass when M is dried at 110 ° C. for 3 hours.

(5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through rollers arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. Use to dry the web.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, drying is generally carried out at 40-250 ° C.

When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

The preferred stretching ratio of simultaneous biaxial stretching can be in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

In the tenter stretching, the drying temperature is preferably within 30 to 200 ° C, more preferably within 100 to 200 ° C.

In the method for producing an optical film according to the present invention, it is preferable that the stretching temperature T at this time is stretched so as to satisfy Tg (A) <T <Tg (B). By stretching at a temperature in this range, it is possible to stretch the resin that constitutes the sea while the island structure grain is not elliptical but round, and the projecting state of the island structure can be controlled. Sufficient moire eliminating ability can be imparted without causing a decrease.

In the present invention, the stretching speed represented by the following formula (I) is preferably within 20 to 300% / min.
Formula (I): Stretching speed (% / min) = {(width dimension after stretching / width dimension before stretching) -1} × 100 (%) / time required for stretching (min)
The stretching speed can be set from the viewpoint of productivity and quality, but if it is 20% / min or more, there is no problem in productivity, and if it is 300% / min or less, a failure such as a crack occurs during stretching. Since it becomes difficult to do, it is preferable.

In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C is most preferable.

(6) Winding step This is a step of winding the film as a film by the winder 37 after the residual solvent amount in the web is 2% by mass or less. The dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film having good properties can be obtained. It is particularly preferable to wind up at 0.00 to 0.10% by mass.

As a winding method, a generally used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The film produced by the method for producing an optical film according to the present invention is preferably a long film. Specifically, the film is about 100 m to 5000 m, and is usually provided in a roll form. It is. The width of the film is preferably 1.3 to 4 m, and more preferably 1.4 to 3 m.

Further, the film produced by the method for producing an optical film according to the present invention preferably has a thickness of 20 μm or more. More preferably, it is 30 μm or more. The upper limit of the thickness is not limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. Preferably it is 125 micrometers or less, More preferably, it is 60 micrometers or less.

The optical film manufactured by the method for manufacturing an optical film according to the present invention requires that the arithmetic average roughness Ra of the two surfaces be in the range of 0.03 to 1.5 μm. The arithmetic average roughness Ra is preferably different, and the arithmetic average roughness Ra based on JIS B0601-2001 on at least one surface is preferably in the range of 0.05 to 2.0 μm. When the value of Ra is 0.05 μm or more, a sufficient scattering effect can be obtained and moire fringes can be eliminated. If Ra is 2.0 micrometers or less, it can suppress effectively that front luminance falls when it is set as a display apparatus.

The arithmetic average roughness Ra is measured using a measuring instrument according to JIS B0601-2001, such as Olympus 3D Laser Microscope LEXT OLS4000, Kosaka Laboratory Co., Ltd., Surfcoder MODEL SE-3500, etc. Can be measured.

The optical film manufactured by the method according to the present invention has a total haze value of 20 to 80% in one film, and an internal haze value obtained by (total haze value) − (surface haze value). Is preferably in the range of 0.15 to 30%.

When the total haze value is 20% or more, moire fringes can be eliminated, and when the total haze value is 80% or less, it is preferable in that it is possible to suppress a decrease in front luminance. A more preferable range of the total haze value is within 35 to 50%. The internal haze value is preferably in the range of 0.15 to 30% from the viewpoint of suppressing moire fringes and preventing reduction in front luminance. A more preferable range of the internal haze value is 0.5 to 20%.

These haze values can be values measured according to JIS K7136 using a Nippon Denshoku Industries Co., Ltd. haze meter NDH2000 in an atmosphere of 23 ° C. and 55% RH.

The total haze value is a haze value of one film according to the present invention, and the internal haze value is a value obtained by subtracting the external haze value from the total haze value. As the internal haze value, a measurement value obtained by covering both surfaces of the film with glycerin having a refractive index of 1.47 and sandwiching the two glass plates to measure the same as the total haze can be used. By doing in this way, the influence of the haze value (namely, external haze value) by the uneven | corrugated shape of a surface can be disregarded, and only the haze value inside a film can be measured.

(Photo curable adhesive)
Preferable examples of the photocurable adhesive for bonding the polarizer and the optical film include a photocurable adhesive composition containing the following components (α) to (δ).

(Α) a cationically polymerizable compound,
(Β) a cationic photopolymerization initiator,
(Γ) Photosensitizer exhibiting maximum absorption in light having a wavelength longer than 380 nm (δ) Naphthalene photosensitizer (cationic polymerizable compound (α))
The cationically polymerizable compound (α), which is a main component of the photocurable adhesive composition and serves as a component that gives adhesive force by polymerization and curing, may be any compound that can be cured by cationic polymerization. It is preferable to include an epoxy compound having one epoxy group. The epoxy compound includes an aromatic epoxy compound having an aromatic ring in the molecule, an alicyclic epoxy compound having at least two epoxy groups in the molecule, and at least one of which is bonded to the alicyclic ring. A fatty acid that does not have an aromatic ring in the molecule and one carbon atom of the ring containing the two carbon atoms to which it is bonded (usually an oxirane ring) is bonded to another aliphatic carbon atom Group epoxy compounds. The photocurable adhesive composition used in the present invention is preferably a cation polymerizable compound (α) having, as a main component, an epoxy resin not containing an aromatic ring or an alicyclic epoxy compound. If a cationically polymerizable compound having an alicyclic epoxy compound as a main component is used, a cured product having a high storage elastic modulus is provided, and an optical film and a polarizer are bonded via the cured product (adhesive layer). In this case, the polarizer is difficult to break.

As described above, the alicyclic epoxy compound has at least two epoxy groups in the molecule, and at least one of them is bonded to the alicyclic ring. Here, the epoxy group bonded to the alicyclic ring is, as shown in the following formula (ep), two bonds in which two bonds of the epoxy group (—O—) constitute the alicyclic ring. Each of the carbon atoms (usually adjacent carbon atoms). In the following general formula (ep), m represents an integer of 2 to 5.

A compound in which a group in which one or a plurality of hydrogen atoms in (CH ₂ ) m in formula (ep) are removed is bonded to another chemical structure can be an alicyclic epoxy compound. Hydrogen constituting the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Of these, compounds having an epoxycyclopentane ring (m = 3 in the above formula (ep)) or an epoxycyclohexane ring (m = 4 in the above formula (ep)) are preferable.

Among the alicyclic epoxy compounds, any of the following formulas (ep-1) to (ep-11) is more preferable because they are easily available and have a large effect of increasing the storage elastic modulus of the cured product.

In the above formula, R ³ to R ²⁴ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and when R ³ to R ²⁴ are alkyl groups, the position bonded to the alicyclic ring is 1 It is an arbitrary number from the first to sixth positions. The alkyl group having 1 to 6 carbon atoms may be a straight chain, may be branched, or may have an alicyclic ring. Y ⁸ represents an oxygen atom or an alkanediyl group having 1 to 20 carbon atoms. Y ¹ to Y ⁷ each independently represents a straight chain, may be branched, and may represent an alkanediyl group having 1 to 20 carbon atoms which may have an alicyclic ring. n, p, q and r each independently represents a number from 0 to 20.

Among the compounds represented by the above formulas (ep-1) to (ep-11), the alicyclic diepoxy compound represented by the formula (ep-2) is preferable because it is easily available. The alicyclic diepoxy compound of the formula (ep-2) includes 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexane. An ester compound with a carboxylic acid (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). Specific examples of such an ester compound include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (a compound in which R5 = R6 = H and n = 0 in the formula (ep-2)), 3 , 4-Epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate (a compound in which R5 = 6-methyl, R6 = 6-methyl, n = 0 in the formula (ep-2)) ) And the like.

Also, it is effective to use an alicyclic epoxy compound in combination with an epoxy resin substantially free of an alicyclic epoxy group. If a cation-polymerizable compound containing an alicyclic epoxy compound as the main component and an epoxy resin substantially free of an alicyclic epoxy group is used as a cationically polymerizable compound, the cured product has a high storage elastic modulus. However, the adhesion between the polarizer and the optical film can be further enhanced. As used herein, an epoxy resin having substantially no alicyclic epoxy group means that one carbon atom of a ring (usually an oxirane ring) containing an epoxy group and two carbon atoms to which the epoxy group is bonded in the molecule. A compound bonded to another aliphatic carbon atom. Examples thereof include polyglycidyl ether of polyhydric alcohol (phenol). Among these, a diglycidyl ether compound represented by the following general formula (ge) is preferable because it is easily available and has a great effect of improving the adhesion between the polarizer and the optical film.

[In the general formula (ge), X represents a direct bond, a methylene group, an alkylidene group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group, O, S, SO ₂ , SS, SO, CO, OCO, or the following formula: This represents a substituent selected from the group consisting of three kinds of substituents represented by (ge-1) to (ge-3), and the alkylidene group may be substituted with a halogen atom. ]

In the formula (ge-1), R ²⁵ and R ²⁶ may be each independently substituted with a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group. Represents a cycloalkyl group having 3 to 10 carbon atoms which may be substituted by a phenyl group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group, and R ²⁵ and R ²⁶ may be linked to each other to form a ring. Good.

In the formula (ge-2), A and D are each independently an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or 6 carbon atoms which may be substituted with a halogen atom. Represents an aryl group of ˜20, an arylalkyl group of 7 to 20 carbon atoms that may be substituted with a halogen atom, a heterocyclic group of 2 to 20 carbon atoms that may be substituted with a halogen atom, or a halogen atom; The methylene group in the alkyl group, aryl group or arylalkyl group may be interrupted by an unsaturated bond, —O— or —S—. a represents a number from 0 to 4, and d represents a number from 0 to 4.

Examples of the diglycidyl ether compound of the general formula (ge) include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; glycidyl ether of tetrahydroxyphenylmethane , Glycidyl ether of tetrahydroxybenzophenone, polyfunctional epoxy resin such as epoxidized polyvinylphenol; polyglycidyl ether of aliphatic polyhydric alcohol; polyglycidyl ether of alkylene oxide adduct of aliphatic polyhydric alcohol; Examples thereof include diglycidyl ether, and among them, polyglycidyl ether of aliphatic polyhydric alcohol is preferable because it is easily available.

Examples of the aliphatic polyhydric alcohol include those having 2 to 20 carbon atoms. More specifically, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl -2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, -Aliphatic diols such as methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol; cyclohexanedi Cycloaliphatic diols such as ethanol, cyclohexanediol, hydrogenated bisphenol A, hydrogenated bisphenol F; trimethylolethane, trimethylolpropane, hexitols, pentitols, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, tetramethylol Examples include trivalent or higher polyols such as propane.

When an alicyclic epoxy compound and an epoxy resin having substantially no alicyclic epoxy group are used in combination, the blending ratio of both is 50 to 50 based on the total amount of the cationic polymerizable compound. It is preferable that 95% by mass and an epoxy resin substantially not having an alicyclic epoxy group be 5% by mass or more. By blending 50% by mass or more of the alicyclic epoxy compound in the whole cationic polymerizable compound, the storage elastic modulus at 80 ° C. of the cured product becomes 1,000 MPa or more, and such a cured product (adhesive layer) is obtained. In the polarizing plate in which the polarizer and the optical film are bonded to each other, the polarizer is hardly broken. Moreover, the adhesiveness of a polarizer and an optical film improves by mix | blending 5 mass% or more of epoxy resins which do not have an alicyclic epoxy group substantially with respect to the whole cationically polymerizable compound. The amount of the epoxy resin having substantially no alicyclic epoxy group is 50 based on the total amount of the cation polymerizable compound when the cation polymerizable compound is a two-component system with the alicyclic epoxy compound. However, if the amount is too large, the storage elastic modulus of the cured product is lowered and the polarizer is easily cracked. Therefore, the amount is 45% by mass or less based on the total amount of the cationically polymerizable compound. Is preferred.

As the cationically polymerizable compound (α) constituting the photocurable adhesive composition, when using an alicyclic epoxy compound and an epoxy resin substantially free of an alicyclic epoxy group as described above, In the range where becomes the above-mentioned amount, in addition to these, other cationically polymerizable compounds may be included. Examples of other cationically polymerizable compounds include epoxy compounds other than formulas (ep-1) to (ep-11) and general formula (ge), oxetane compounds, and the like.

Epoxy compounds other than those represented by formulas (ep-1) to (ep-11) and formula (ge) include at least one alicyclic ring in the molecule other than those represented by formulas (ep-1) to (ep-11). An alicyclic epoxy compound having an epoxy group to be bonded, an aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the formula (ge), an aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule, aromatic There are hydrogenated epoxy compounds in which aromatic rings in group epoxy compounds are hydrogenated.

Examples of alicyclic epoxy compounds having an epoxy group bonded to at least one alicyclic ring in a molecule other than those represented by formulas (ep-1) to (ep-11) include 4-vinylcyclohexene diepoxide, 1, 2: diepoxides of vinylcyclohexenes such as 8,8,9-diepoxy limonene.

Examples of the aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the general formula (ge) include triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, and diglycidyl ether of polyethylene glycol.

The aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule can be a glycidyl ether of an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in the molecule. Bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, phenol novolac resin glycidyl ether, and the like.

A hydrogenated epoxy compound in which an aromatic ring in an aromatic epoxy compound is hydrogenated is an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in a molecule as a raw material of the aromatic epoxy compound. Can be obtained by performing a hydrogenation reaction selectively under pressure in the presence of a catalyst and glycidyl etherifying the resulting hydrogenated polyhydroxy compound. Specific examples include diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol F, diglycidyl ether of hydrogenated bisphenol S, and the like.

Of these epoxy compounds other than formulas (ep-1) to (ep-11) and general formula (ge), they have an epoxy group bonded to an alicyclic ring, and are classified as the alicyclic epoxy compounds defined above. When the compound is added, the sum of the alicyclic epoxy compounds represented by the formulas (ep-1) to (ep-11) does not exceed 95% by mass based on the total amount of the cationic polymerizable compound Used in a range.

An oxetane compound that can be any cationically polymerizable compound is a compound having a 4-membered cyclic ether (oxetanyl group) in the molecule. Specific examples thereof include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [ (3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl) oxetane, phenol novolak oxetane, 1,3-bis [(3-Ethyloxetane-3-yl) methoxy] benzene, oxetanylsilsesquioxane, oxetanyl silicate and the like.

By blending the oxetane compound at a ratio of 30% by mass or less based on the total amount of the cationic polymerizable compound, an effect of improving curability is expected compared to the case where only the epoxy compound is used as the cationic polymerizable compound. There are things you can do.
(Photocationic polymerization initiator (β))
In the present invention, the cationically polymerizable compound as described above is cationically polymerized by irradiation with active energy rays and cured to form an adhesive layer. Therefore, the photocurable adhesive composition has photocationic polymerization initiation. It is preferable to blend the agent (β).

The cationic photopolymerization initiator generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of the cationic polymerizable compound (α). It is. Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with the cationically polymerizable compound (α). Examples of compounds that generate cation species and Lewis acids upon irradiation with active energy rays include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-allene complexes.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexafluoro. 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexa Fluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfoni O] -2-Isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfo Nio-diphenyl sulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) tris (tri Fluoromethylsulfonyl) methanide and the like.

These photocationic polymerization initiators may be used alone or in admixture of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength. .

The blending amount of the photocationic polymerization initiator (β) is 1 to 10 parts by mass with respect to 100 parts by mass of the whole cationic polymerizable compound (α). By blending 1 part by mass or more of the cationic photopolymerization initiator per 100 parts by mass of the cationic polymerizable compound (α), the cationic polymerizable compound (α) can be sufficiently cured, and the resulting polarizing plate has high mechanical strength. And give adhesive strength. On the other hand, when the amount is increased, the ionic substance in the cured product increases, so that the hygroscopic property of the cured product increases and the durability performance of the polarizing plate may be lowered. ) Is 10 parts by mass or less per 100 parts by mass of the cationically polymerizable compound (α).

The amount of the cationic photopolymerization initiator (β) is preferably 2 parts by mass or more and preferably 6 parts by mass or less per 100 parts by mass of the cationic polymerizable compound (α).
(Photosensitizer (γ))
The photocurable adhesive composition that can be used in the present invention is suitable for light having a wavelength longer than 380 nm in addition to the cationic polymerizable compound (α) and the cationic photopolymerization initiator (β) including the epoxy compound as described above. Contains a photosensitizer (γ) exhibiting maximum absorption. The cationic photopolymerization initiator (β) exhibits maximum absorption at a wavelength near or shorter than 300 nm, generates a cationic species or a Lewis acid in response to light having a wavelength near the wavelength, and generates a cationic polymerizable compound (α ) Is initiated, but a photosensitizer (γ) that exhibits maximum absorption in light having a wavelength longer than 380 nm is blended so as to be sensitive to light having a longer wavelength than that.

As such a photosensitizer (γ), an anthracene compound represented by the following general formula (at) is advantageously used.

[Wherein, R ⁵ and R ⁶ each independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms. R7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ]
Specific examples of the anthracene compound represented by the general formula (at) include 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9 , 10-dibutoxyanthracene, 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene, 9,10-bis (2-methoxyethoxy) anthracene, 9,10-bis (2-ethoxyethoxy) anthracene, 9 , 10-bis (2-butoxyethoxy) anthracene, 9,10-bis (3-butoxypropoxy) anthracene, 2-methyl or 2-ethyl-9,10-dimethoxyanthracene, 2-methyl or 2-ethyl-9, 10-diethoxyanthracene, 2-methyl or 2 Ethyl-9,10-dipropoxyanthracene, 2-methyl or 2-ethyl-9,10-diisopropoxyanthracene, 2-methyl or 2-ethyl-9,10-dibutoxyanthracene, 2-methyl or 2-ethyl Examples include -9,10-dipentyloxyanthracene, 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

By mix | blending the above photosensitizers ((gamma)) with a photocurable adhesive composition, the sclerosis | hardenability of a photocurable adhesive composition improves compared with the case where it is not mix | blended. Curability is improved by setting the blending amount of the photosensitizer (γ) to 100 parts by mass of the cationic polymerizable compound (α) constituting the photocurable adhesive composition to be 0.1 parts by mass or more. The effect is manifested. On the other hand, when the blending amount of the photosensitizer (γ) increases, problems such as precipitation during low-temperature storage occur, so the blending amount of 2 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (α) To do. From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the amount of the photosensitizer (γ) in a range in which the adhesiveness between the polarizer and the optical film is maintained appropriately. For example, with respect to 100 parts by mass of the cationically polymerizable compound (α), the amount of the photosensitizer (γ) is in the range of 0.1 to 0.5 parts by mass, further 0.1 to 0.3 parts by mass. Is preferred.
(Photosensitizer (δ))
The photocurable adhesive composition that can be used in the present invention includes the following cationic polymerizable compound (α) containing an epoxy compound, a cationic photopolymerization initiator (β), and a photosensitizer (γ). It contains a naphthalene-based photosensitization aid (δ) represented by the general formula (nf).

[Wherein, R ¹ and R ² are each an alkyl group having 1 to 6 carbon atoms. ]
Specific examples of the naphthalene photosensitizer (δ) include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1, 4-dibutoxynaphthalene and the like can be mentioned.

By blending the naphthalene-based photosensitization aid (δ) with the photocurable adhesive composition, the curability of the photocurable adhesive composition is improved as compared with the case where it is not blended. By setting the blending amount of the naphthalene photosensitizer (δ) to 100 parts by mass of the cationic polymerizable compound (α) constituting the photocurable adhesive composition to be 0.1 parts by mass or more, curability is improved. The improvement effect is manifested. On the other hand, if the amount of the naphthalene-based photosensitization aid (δ) increases, problems such as precipitation during low-temperature storage occur, and therefore the amount is 10 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). The blending amount. Preferably, the blending amount is 5 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α).

Furthermore, the photocurable adhesive composition that can be used in the present invention can contain an additive component as an optional component as long as the effects of the present invention are not impaired. As additive components, in addition to the above-mentioned photocationic polymerization initiator and photosensitizer (γ), photosensitizers other than the photosensitizer (γ), thermal cationic polymerization initiators, polyols, ion trapping agents , Antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, leveling agents, dyes, organic solvents, and the like.

When the additive component is contained, the amount of the additive component used is preferably 1000 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). When the amount used is 1000 parts by mass or less, a cationically polymerizable compound (α), a photocationic polymerization initiator (β), and a photosensitizer, which are essential components of the photocurable adhesive composition that can be used in the present invention. By combining (γ) and the photosensitizing aid (δ), the effects of improving storage stability, preventing discoloration, improving curing speed, and ensuring good adhesion can be exhibited well.

Other preferable examples of the adhesive for laminating the polarizer and the optical film include a photocurable adhesive composition containing the following three components (α1), (α2) and (β1) as essential components: Is included.

(Α1) Epoxy compound having at least two epoxy groups in the molecule (α2) Oxetane compound having at least one oxetanyl group in the molecule (β1) Photocationic polymerization initiator Hereinafter, the epoxy compound of (α1) above, The oxetane compound (α2) and the photocationic polymerization initiator (β1) are simply referred to as epoxy compound (α1), oxetane compound (α2), and photocationic polymerization initiator (β1), respectively.

The mass ratio of the epoxy compound (α1) to the oxetane compound (α2) (epoxy compound (α1): oxetane compound (α2)) is preferably about 90:10 to 10:90. The cationic photopolymerization initiator (β1) is preferably blended in the composition at a ratio of about 0.5 to 20% by mass.

This photo-curable adhesive can optionally contain an unsaturated compound having at least one ethylenically unsaturated bond in the molecule as the (ε) component. When such an unsaturated compound (ε) is contained, it is preferable to contain a radical photopolymerization initiator as the (ζ) component. Furthermore, this photocurable adhesive agent can also contain the other component which does not have polymerizability as ((eta)) component.

The unsaturated compound (ε), the photoradical polymerization initiator as the (ζ) component, and the other non-polymerizable component as the (η) component are simply referred to as the unsaturated compound (ε) and the photoradical, respectively. It is referred to as a polymerization initiator (ζ) and other component (η) having no polymerizability.
(Epoxy compound (α1))
In the photo-curable adhesive composition that can be used in the present invention, the epoxy compound (α1) is not particularly limited as long as it has at least two epoxy groups in the molecule, and various kinds of generally known curings. A functional epoxy compound can be used. As a preferable epoxy compound (α1), a compound having at least two epoxy groups and at least one aromatic ring in the molecule (hereinafter referred to as an aromatic epoxy compound), or having at least two epoxy groups in the molecule. Examples of the compound include at least one compound formed between two adjacent carbon atoms constituting the alicyclic ring (hereinafter referred to as an alicyclic epoxy compound).

The aromatic epoxy compound is not particularly limited as long as the effect of the present invention is not hindered, but bisphenol type epoxy such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of brominated bisphenol A, and the like. Resin; Novolac type epoxy resin such as phenol novolac type epoxy resin, cresol novolak type epoxy resin; other, biphenyl type epoxy resin, hydroquinone diglycidyl ether, resorcin diglycidyl ether, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester, Epoxidized styrene-butadiene copolymer, epoxidized styrene-isoprene copolymer, addition of terminal carboxylic acid polybutadiene and bisphenol A type epoxy resin Applied Physics, etc. as an example.

Here, the epoxy resin means a compound or polymer having an average of two or more epoxy groups in the molecule and cured by reaction. In accordance with the practice in this field, a monomer may be referred to as an epoxy resin as long as it has two or more curable epoxy groups in the molecule.

The alicyclic epoxy compound is not particularly limited as long as the effects of the present invention are not hindered, but dicyclopentadiene dioxide, limonene dioxide, 4-vinylcyclohexene dioxide, 3,4-epoxycyclohexylmethyl-3,4- Examples include compounds having at least one epoxidized cyclohexyl group such as epoxycyclohexanecarboxylate and bis (3,4-epoxycyclohexylmethyl) adipate.

In addition to the above, aliphatic epoxy compounds such as 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, polytetramethylene glycol diglycidyl ether; dihydrogenated bisphenol A Epoxy compounds with aromatic rings hydrogenated, such as glycidyl ethers; compounds with both ends of hydroxybutadiene (hydroxyl group) glycidyl ethers, polybutadiene internal epoxidation products, styrene-butadiene copolymers A compound in which the double bond is partially epoxidized (for example, Epofriend manufactured by Daicel Chemical Industries, Ltd.), a block copolymer of ethylene-butylene copolymer and polyisoprene is partially epoxidized Objects (e.g., KRATON Co. L-207) polymeric epoxy compounds, such as, may also be an epoxy compound ([alpha] 1).

Among these, aromatic epoxy compounds are preferable because they are excellent in durability and the like when used for polarizing plates, and particularly excellent in adhesion to polarizers and optical films. Furthermore, preferred examples of the aromatic epoxy compound include glycidyl ethers of aromatic compounds or glycidyl esters of aromatic compounds. Specific examples of glycidyl ethers of aromatic compounds include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of brominated bisphenol A; phenol novolac type epoxy resin, cresol novolak type Preferred examples include novolak-type epoxy resins such as epoxy resins; biphenyl-type epoxy resins; hydroquinone diglycidyl ether; resorcin diglycidyl ether and the like. Specific examples of glycidyl esters of aromatic compounds include terephthalic acid diglycidyl ester and phthalic acid diglycidyl ester.

Among them, glycidyl ether of an aromatic compound is particularly preferable because it is more excellent in adhesion between a polarizer and an optical film and durability when used for a polarizing plate. Among the glycidyl ethers of aromatic compounds, particularly preferable compounds include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and phenol novolac type epoxy resin.

An epoxy compound ((alpha) 1) can also be used individually by 1 type, and 2 or more types can also be mixed and used for it. For example, two or more aromatic epoxy compounds can be mixed and used, or an aromatic epoxy compound as a main component and an alicyclic epoxy compound can also be mixed.
(Oxetane compound (α2))
In the photocurable adhesive that can be used in the present invention, the oxetane compound (α2) is not particularly limited as long as it has at least one oxetanyl group in the molecule, and various compounds having an oxetanyl group are also used. be able to. Preferred examples of the oxetane compound (α2) include a compound having one oxetanyl group in the molecule (hereinafter referred to as monofunctional oxetane) and a compound having two or more oxetanyl groups in the molecule (hereinafter referred to as polyfunctional oxetane). As mentioned.

As monofunctional oxetane, monofunctional oxetane containing alkoxyalkyl group such as 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, and monofunctional containing aromatic group such as 3-ethyl-3-phenoxymethyloxetane. Preferred examples include hydroxy group (hydroxyl group) -containing monofunctional oxetane such as oxetane and 3-ethyl-3-hydroxymethyloxetane.

Examples of the polyfunctional oxetane include 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, 1,4-bis [(3-ethyloxetane-3-yl) methoxymethyl] benzene, 1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,2-bis [(3-ethyl Oxetane-3-yl) methoxy] benzene, 4,4'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,2'-bis [(3-ethyloxetane-3-yl) methoxy] Biphenyl, 3,3 ′, 5,5′-tetramethyl-4,4′-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,7-bis [(3-ethy Oxetane-3-yl) methoxy] naphthalene, bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] methane, bis [2-{(3-ethyloxetane-3-yl) methoxy} phenyl] Etherified modification of methane, 2,2-bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] propane, novolak type phenol-formaldehyde resin with 3-chloromethyl-3-ethyloxetane, 3 (4), 8 (9) -bis [(3-ethyloxetane-3-yl) methoxymethyl] -tricyclo [5.2.1.02,6] decane, 2,3-bis [(3-ethyloxetane -3-yl) methoxymethyl] norbornane, 1,1,1-tris [(3-ethyloxetane-3-yl) methoxymethyl] propane, Butoxy-2,2-bis [(3-ethyloxetane-3-yl) methoxymethyl] butane, 1,2-bis [{2- (3-ethyloxetane-3-yl) methoxy} ethylthio] ethane, bis [ {4- (3-Ethyloxetane-3-yl) methylthio} phenyl] sulfide, 1,6-bis [(3-ethyloxetane-3-yl) methoxy] -2,2,3,3,4,4,4 Hydrolysis condensate of 5,5-octafluorohexane, 3-[(3-ethyloxetane-3-yl) methoxy] propyltriethoxysilane, condensation of tetrakis [(3-ethyloxetane-3-yl) methyl] silicate Thing etc. are mentioned.

The oxetane compound (α2) is preferably liquid at room temperature with a molecular weight of 500 or less from the viewpoint of coating properties and adhesion to an optical film when used for a polarizing plate. Furthermore, in terms of excellent durability of the polarizing plate, a monofunctional oxetane is more preferably an aromatic ring in the molecule or a polyfunctional oxetane. Examples of such preferred oxetane compounds include 3-ethyl-3-phenoxymethyloxetane, 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, 1,4-bis [(3 -Ethyloxetane-3-yl) methoxymethyl] benzene and the like.

The oxetane compound (α2) can also be used alone or in combination of two or more.

The mass ratio of the epoxy compound (α1) to the oxetane compound (α2) (epoxy compound (α1): oxetane compound (α2)) is 90:10 to 10:90. If this mass ratio is excessive or insufficient, the effect of curing in a short time, which is one of the important characteristics in the photocurable adhesive composition that can be used in the present invention, is not sufficiently exhibited. A preferred mass ratio is about 70:30 to 20:80, more preferably 60:40, because it has a low viscosity before curing, excellent coating properties, and can exhibit sufficient adhesion and flexibility after curing. It is about 25:75.
(Photocationic polymerization initiator (β1))
The photocurable adhesive composition that can be used in the present invention contains the above-described epoxy compound (α1) and oxetane compound (α2) as curing components, and these are all cured by cationic polymerization. In order to start the cationic polymerization, a photocationic polymerization initiator (β1) is blended. The cationic photopolymerization initiator (β1) generates cationic species or a 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.

By blending the cationic photopolymerization initiator (β1), curing at room temperature is possible, and there is little need to consider the heat resistance of the polarizer and distortion due to expansion or contraction. it can. In addition, since the cationic photopolymerization initiator (β1) acts catalytically upon irradiation with active energy rays, it is excellent in storage stability and workability even when mixed with the epoxy compound (α1) and the oxetane compound (α2). .

Photocationic polymerization initiators (β1) that generate cationic species and Lewis acids upon irradiation with such active energy rays include, for example, onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, iron- An allene complex etc. can be mentioned.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium hexafluorophosphate, diphenyl [ 4- (phenylthio) phenyl] sulfonium hexafluoroantimonate, 4,4'-bis (diphenylsulfonio) diphenyl sulfide bishexafluorophosphate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl Sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfur 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) Borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4- (p -Tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris ( (Trifluoromethylsulfonyl) methanide and the like.

These photocationic polymerization initiators (β1) may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and therefore can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

As the cationic photopolymerization initiator (β1), commercially available products can be easily obtained. For example, Kayrad PCI-220 and Kayalad PCI-620 (above, manufactured by Nippon Kayaku Co., Ltd.) under the trade names, respectively. UVI-6992 (manufactured by Dow Chemical Co.), Adeka optomer SP-150, Adeka optomer SP-170 (above, manufactured by ADEKA), CI-5102, CIT-1370, CIT-1682S, CIP-1866S , CIP-2048S, CIP-2064S (manufactured by Nippon Soda Co., Ltd.), DPI-101, DPI-102, DPI-103, DPI-105, MPI-103, MPI-105, BBI-101, BBI-102 , BBI-103, BBI-105, TPS-101, TPS-102, TPS-103, TPS-105 MDS-103, MDS-105, DTS-102, DTS-103 (manufactured by Midori Chemical Co., Ltd.), PI-2074 (manufactured by Rhodia), Irgacure 250, Irgacure PAG103, Irgacure PAG108, Irgacure PAG121, Irgacure PAG203 ( As mentioned above, BASF), CPI-100P, CPI-101A, CPI-200K, CPI-210S (above, San Apro Co., Ltd.) and the like can be mentioned. Among these, UVI-6992, CPI-100P, CPI-101A, CPI-200K, and CPI-210S containing diphenyl [4- (phenylthio) phenyl] sulfonium as a cation component are preferable.

The blending ratio of the cationic photopolymerization initiator (β1) is in the range of 0.5 to 20% by mass based on the entire photocurable adhesive. When the blending ratio is less than 0.5% by mass, curing of the photocurable adhesive becomes insufficient, and mechanical strength and adhesive strength are lowered. On the other hand, when the blending ratio exceeds 20% by mass, the ionic substance in the cured product is increased, so that the hygroscopic property of the cured product is increased and the durability may be lowered.
(Unsaturated compound (ε))
The photocurable adhesive may contain an unsaturated compound (ε) having at least one ethylenically unsaturated bond in the molecule, if necessary.

A typical example of such an unsaturated compound (ε) includes a (meth) acrylic compound having at least one (meth) acryloyl group in the molecule.

The (meth) acrylic compound is not particularly limited, and examples thereof include (meth) acrylates, (meth) acrylamides, (meth) acrylic acid, (meth) acryloylmorpholine, and (meth) acrylaldehyde.

The (meth) acrylates having one (meth) acryloyl group in the molecule (hereinafter referred to as monofunctional (meth) acrylate) are not particularly limited, but for example, methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, Alkyl (meth) acrylates such as stearyl (meth) acrylate; hydrides such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate Roxyalkyl (meth) acrylates; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1,4-cyclohexanedimethylol mono (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, Alicyclic monofunctional (meth) acrylates such as dicyclopentenyloxyethyl (meth) acrylate; benzyl (meth) acrylate, (meth) acrylate of p-cumylphenol alkylene oxide adduct, o-phenylphenol alkylene oxide (Meth) acrylates of adducts, (meth) acrylates of phenol alkylene oxide adducts, (meth) acrylates of nonylphenol alkylene oxide adducts, (Meth) acrylates (wherein alkylene oxides include ethylene oxide and propylene oxide); addition of alkylene oxide of 2-methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, 2-ethylhexyl alcohol Alkoxyalkyl (meth) acrylates such as (meth) acrylates; such as ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, pentanediol mono (meth) acrylate, hexanediol mono (meth) acrylate Mono (meth) acrylates of dihydric alcohols; mono (meth) acrylate of diethylene glycol, mono (meth) acrylate of triethylene glycol, tetraethylene glycol Polyalkylenes such as Cole mono (meth) acrylate, Polyethylene glycol mono (meth) acrylate, Dipropylene glycol mono (meth) acrylate, Tripropylene glycol mono (meth) acrylate, Polypropylene glycol mono (meth) acrylate Mono (meth) acrylates of glycols; glycidyl (meth) acrylates; tetrahydrofurfuryl (meth) acrylates; tetrahydrofurfuryl (meth) acrylates such as caprolactone-modified tetrahydrofurfuryl (meth) acrylates; 3,4-epoxycyclohexyl Examples include methyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl isocyanate.

Further, (meth) acrylates having two or more (meth) acryloyl groups in the molecule are not particularly limited, and examples thereof include the following compounds.

Alicyclic rings such as tricyclodecane dimethylol di (meth) acrylate, 1,4-cyclohexane dimethylol di (meth) acrylate, norbornane dimethylol di (meth) acrylate, di (meth) acrylate of hydrogenated bisphenol A Di (meth) acrylates having bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate containing di (meth) acrylate, bisphenol A Di (meth) acrylates having an aromatic ring such as di (meth) acrylate of A diglycidyl ether; ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, penta Di (meth) acrylates of alkylene glycols such as diol di (meth) acrylate and hexanediol di (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate Di (meth) acrylates of polyalkylene glycols such as polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate; Di- or tri (meth) acrylates, di- or tri (meth) acrylates of glycerols such as di- or tri (meth) acrylates of diglycerol; glycerol Di- or tri (meth) acrylates of bisphenol alkylene oxide adducts; di (meth) acrylates of bisphenol A alkylene oxide adducts, di (meth) acrylates of bisphenol F alkylene oxide adducts (Meth) acrylates; trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, di Polyol poly (meth) acrylates such as pentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate; And poly (meth) acrylates of polyol alkylene oxide adducts; di- or tri (meth) acrylates of isocyanuric acid alkylene oxide adducts; 1,3,5-tri (meth) acryloylhexahydro-s-triazine and the like Can be mentioned.

(Meth) acrylamides include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N- (3-N, N- Examples thereof include dimethylaminopropyl) (meth) acrylamide, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide.

Also, oligomers such as urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate can be used as the (meth) acrylic compound.

Furthermore, a compound having an ethylenically unsaturated bond other than the (meth) acryloyl group can also be used as the (meth) acrylic compound. Specific examples thereof include allyl (meth) acrylate and N, N-diallyl (meth) acrylamide.

The unsaturated compound (ε) is not particularly limited, and in addition to the above (meth) acrylic compounds, vinyl compounds such as N-vinyl-2-pyrrolidone, divinyl adipate and divinyl sebacate; triallyl isocyan Allyl compounds such as nurate, triallylamine, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetraallylammonium salt, allylamine; such as maleic acid and itaconic acid Unsaturated carboxylic acids and the like can also be used.

Among these unsaturated compounds (ε), (meth) acrylic compounds are preferable. Furthermore, when a polarizer and an optical film are bonded via an adhesive containing the same to produce a polarizing plate, at least one alicyclic skeleton in the molecule or from the viewpoint of enhancing durability such as heat resistance A (meth) acrylic compound having an aromatic ring skeleton is more preferable. Specific examples of the (meth) acrylic compound having at least one alicyclic skeleton or aromatic ring skeleton in the molecule include the above-described alicyclic monofunctional (meth) acrylates and monofunctional having an aromatic ring. Preferable examples include (meth) acrylates, di (meth) acrylates having an alicyclic ring, or di (meth) acrylates having an aromatic ring. Among these, di (meth) acrylate having a tricyclodecane skeleton is preferable, and specific examples of such (meth) acrylic compounds are tricyclodecane dimethylol di (meth) acrylate and the like. be able to.

The unsaturated compound (ε) can be used to adjust the curing speed, the adhesion between the polarizer and the optical film, the elastic modulus of the adhesive layer, the durability of the adhesive, and the like. An unsaturated compound ((epsilon)) can be used individually by 1 type or in mixture of 2 or more types.

When the unsaturated compound (ε) is blended, the blending ratio is preferably 35% by mass or less based on the entire composition. Thereby, the adhesiveness between a polarizer and an optical film will be excellent. When the amount of the unsaturated compound (ε) exceeds 35% by mass, it is difficult to obtain sufficient adhesive strength with the polarizer. Therefore, the blending ratio of the unsaturated compound (ε) is more preferably 30% by mass or less, and further preferably about 5 to 25% by mass, especially about 10 to 20% by mass.
(Photoradical polymerization initiator (ζ))
When the photocurable adhesive contains an unsaturated compound (ε), it is preferable to add a photoradical polymerization initiator (ζ) in order to promote the radical polymerizability and make the curing rate sufficient.

Specific examples of the radical photopolymerization initiator (ζ) are not particularly limited, but for example, 4′-phenoxy-2,2-dichloroacetophenone, 4′-tert-butyl-2,2-dichloroacetophenone, 2,2- Dimethoxy-2-phenylacetophenone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 1-hydroxycyclohexyl phenyl ketone, α, α-diethoxyacetophenone, 2-hydroxy-2 -Methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methyl Propan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2- Acetophenone photopolymerization initiators such as tilpropan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin Benzoin ether photopolymerization initiators such as isopropyl ether and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 2,4,6-trimethylbenzophenone Benzophenone-based photopolymerization initiators such as: 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, thioxanes such as 1-chloro-4-propoxythioxanthone 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) ) Acylphosphine oxide photopolymerization initiators such as phenylphosphine oxide; Oxime esters such as 1,2-octanedione, 1- [4- (phenylthiophenyl)]-2- (O-benzoyloxime) Photopolymerization initiator; camphorquinone and the like can be mentioned.

The radical photopolymerization initiator (ζ) can be used alone or in combination of two or more according to the desired performance. When the radical photopolymerization initiator (ζ) is blended, the blending ratio is preferably 10% by mass or less, more preferably about 0.1 to 3% by mass based on the entire composition. If the amount of the photo radical polymerization initiator (ζ) is too large, sufficient strength may not be obtained. Moreover, when the amount is insufficient, the adhesive may not be sufficiently cured.
(Other components (η))
Furthermore, in the photocurable adhesive composition that can be used in the present invention, other components different from the components (α1) to (ζ) are optionally blended within a range not impairing the effects of the present invention. Can do.

As one type belonging to such other components, there may be mentioned compounds having cationic polymerizability other than the epoxy compound (α1) and the oxetane compound (α2). Specific examples include, but are not limited to, an epoxy compound having one epoxy group in the molecule, and the like. Further, as another type belonging to the other component, other component (η) having no polymerizability can be exemplified. When the other component (η) having no polymerizability is blended, the blending ratio is preferably about 10% by mass or less based on the entire composition.

Although it does not specifically limit as an example of the other component ((eta)) which does not have polymerizability, A photosensitizer is mentioned. By blending a photosensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

Specific photosensitizers are not particularly limited. For example, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o Benzophenone derivatives such as methyl benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, 4,4′-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone; 2 Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone; other α, α-diethoxyacetophenone, benzyl, Luenone, xanthone, uranyl compound, halogen compound and the like can be mentioned.

Among these, there is a compound corresponding to the above-mentioned photo radical polymerization initiator (ζ), but the photo sensitizer here is particularly one that functions as a sensitizer for the photo cationic polymerization initiator (β 1). It is not limited. These may be used alone or in combination of two or more.

The photosensitizer is a cationically polymerizable monomer (including the above epoxy compound (α1) and oxetane compound (α2) in the photocurable adhesive composition that can be used in the present invention, and has the other cationic polymerization properties described above. The total amount of the compound (including the compound when it is blended) is preferably 100 parts by mass and is preferably contained in the range of 0.1 to 20 parts by mass.

Further, a thermal cationic polymerization initiator can also be used as another component (η) having no polymerizability. Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These initiators can be easily obtained as commercial products. For example, both of these initiators are indicated by trade names, and ADEKA OPTON CP77 and ADEKA OPTON CP66 (manufactured by ADEKA Corporation), CI-2639, CI- 2624 (manufactured by Nippon Soda Co., Ltd.), Sun Aid SI-60L, Sun Aid SI-80L, Sun Aid SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.) and the like.

Since polyols have the property of promoting cationic polymerization, they can also be used as other components (η) that do not have polymerizability. As the polyols, those having no acidic group other than the phenolic hydroxy group (hydroxyl group) are preferable. For example, a polyol compound having no functional group other than the hydroxy group (hydroxyl group), a polyester polyol compound, a polycaprolactone polyol compound, and a phenolic compound. Examples thereof include a polyol compound having a hydroxy group (hydroxyl group) and a polycarbonate polyol compound.

Furthermore, as long as the effects of the present invention are not impaired, other components (η) having no polymerizability include silane coupling agents, ion trapping agents, antioxidants, light stabilizers, chain transfer agents, sensitizers, and tackifiers. An agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, a leveling agent, a dye, an organic solvent, and the like can be blended.

It is also effective to add a thermoplastic resin as another component (η) having no polymerizability for the purpose of further improving the adhesion with the optical film. As the thermoplastic resin, those having a glass transition temperature of 70 ° C. or higher are preferable from the viewpoint of enhancing the durability of the polarizer, and particularly preferred examples include a methyl methacrylate polymer.
(Polarizer)
The polarizing plate is mainly composed of two optical films that protect both the front side and the back side of the polarizer. The optical film according to the present invention is used for at least one of two optical films sandwiching a polarizer from both sides. Since the optical film according to the present invention has not only a moire eliminating ability but also a protective film property, the manufacturing cost of the polarizing plate can be reduced.

The polarizing plate according to the present invention can be used as a polarizing plate on the backlight source side of the image display device or a polarizing plate on the viewing side. When used for the backlight unit-side polarizing plate, it is preferable that the optical film according to the present invention is disposed so as to be closest to the backlight source.

<Production method of polarizing plate>
Hereinafter, an example of the manufacturing method of the polarizing plate using a photocurable adhesive agent is demonstrated.

The polarizing plate adheres the polarizer and the optical film to each other through an adhesive coating step of applying the following photocurable adhesive to at least one of the adhesive surfaces of the polarizer and the optical film, and an adhesive layer. It can manufacture by the manufacturing method including the bonding process to bond, and the hardening process which hardens an adhesive bond layer in the state to which the polarizer and the optical film were adhere | attached through the adhesive bond layer.

In addition, you may provide the pre-process process which performs the easy adhesion process by corona (discharge) process, plasma process, etc. on the surface which adhere | attaches the polarizer of an optical film.
(Pretreatment process)
In the pretreatment step, the surface of the optical film that adheres to the polarizer is subjected to an easy adhesion treatment. When an optical film is bonded to both surfaces of the polarizer, an easy adhesion process is performed on each optical film. In the next adhesive application process, the surface subjected to the easy adhesion treatment is treated as an adhesion surface with the polarizer.
(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When the photocurable adhesive is directly applied to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.
(Bonding process)
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, an optical film is superimposed thereon. When a photocurable adhesive is applied to the surface of the optical film in the previous application step, a polarizer is superimposed thereon. In addition, when a photocurable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In the case where the optical film is bonded to both surfaces of the polarizer, and the photocurable adhesive is used on both surfaces, the optical film is superimposed on the both surfaces of the polarizer via the photocurable adhesive. Usually, in this state, both sides (if the optical film is superimposed on one side of the polarizer, the polarizer side and the optical film side, and if the optical film is superimposed on both sides of the polarizer, The film is pressed with a roller or the like from the film side). As the material of the roller, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.
(Curing process)
In the curing process, an uncured photocurable adhesive is irradiated with active energy rays to cure the adhesive layer containing an epoxy compound or an oxetane compound, and the polarizer and the optical layer overlapped via the photocurable adhesive. Adhere to the film. When bonding an optical film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or an optical film side. Moreover, when bonding an optical film on both surfaces of a polarizer, an active energy ray is applied from either one of the optical films in a state where the optical film is superimposed on both surfaces of the polarizer via a photocurable adhesive. It is advantageous to irradiate and simultaneously cure the photocurable adhesive on both sides. However, when an ultraviolet absorber is blended in one of the optical films and the active energy ray is ultraviolet, normally, ultraviolet rays are irradiated from the other optical film side not blended with the ultraviolet absorber. Is done.

As the active energy ray, visible light, ultraviolet ray, X-ray, electron beam and the like can be used, but ultraviolet ray is generally preferably used because it is easy to handle and has a sufficient curing rate. The light source of the active energy ray is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less. An LED lamp or the like can be used.

The light irradiation intensity to the photocurable adhesive is determined for each target composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is UV. Adjustment is preferably made so that it is in the range of 1 to 3,000 mW / cm ² as -B (ultraviolet light in the middle wavelength range of 280 to 320 nm). When the irradiation intensity is less than 1 mW / cm ² , the reaction time becomes too long, and when the irradiation intensity exceeds 3,000 mW / cm ² , due to the heat radiated from the lamp and the heat generated during polymerization of the photocurable adhesive, There is a possibility of causing yellowing of the photocurable adhesive and deterioration of the polarizer.

The light irradiation time to the photocurable adhesive is controlled for each composition to be cured and is not particularly limited. However, the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ / cm. It is preferably set to be in the range of ² . When the integrated light quantity is less than 10 mJ / cm ² , active species derived from the polymerization initiator are not sufficiently generated, and the adhesive layer may be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

When curing the photocurable adhesive by irradiating with active energy rays, it is possible to cure under conditions that do not deteriorate the various functions of the polarizing plate, such as the degree of polarization of the polarizer, the transmittance, the hue, and the transparency of the optical film. preferable.

In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less.

(Liquid crystal display device)
The polarizing plate of this invention can be used for the liquid crystal display device of a various aspect.

As an example of the configuration of the liquid crystal display device, in the backlight type (direct type), as shown in FIG. Etc.) / Upper diffusion sheet 5a / liquid crystal panel 12a (polarizer 10a / protective film (retardation film etc.) 9a / substrate 8a / liquid crystal cell 7a / protective film 11a)] It is the structure used.

On the other hand, in the side light type configuration, as shown in FIG. 2B, the light source 1a is composed of a light emitting light source 2a and a light guide plate 13a, and is mainly used for small LCDs for monitors and mobile applications.

The lower diffusion sheet is an optical sheet having strong light diffusibility mainly for reducing in-plane luminance unevenness of the backlight unit (BLU) 6a, and the condensing sheet transmits diffused light in the front direction of the liquid crystal display device (display device plane). The upper diffusion sheet is used to reduce the moire generated by a periodic structure such as a prism sheet that is a light condensing sheet or a pixel in a liquid crystal cell, and the lower diffusion sheet. This optical sheet is used to further reduce in-plane luminance unevenness that cannot be removed by the sheet.

In the liquid crystal display device according to the present invention, at least the upper diffusion sheet is removed from the surface light source device in FIGS. 2A and 2B, and the polarizing plate of the present invention can be used as shown in FIGS. 3A and 3B.

When the optical film according to the present invention is used, the polarizing plate protective film for the polarizing plate (lower polarizing plate) on the backlight unit side is removed, and the optical film according to the present invention is attached to the polarizing plate instead. It may be configured as follows. Even with such a configuration, moire fringes can be suppressed without reducing the front luminance. Furthermore, the cost reduction of the whole liquid crystal display device is realizable by setting it as the structure which removed the protective film for upper polarizing plates in this way.

Liquid crystal cell display methods include twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), and optically compensated bend cells (OCB). It can be preferably used for a transmissive, reflective, or transflective liquid crystal display device.

As light emitting light sources (light emitters) used for the light source, CCFL (Cold Cathode Fluorescent Lamp, cold cathode tube), HCFL (Hot Cathode Fluorescent Lamp, hot cathode tube), LED (Light Emitting Diode, light emitting diode), OLED (Org diode) Light-emitting diode, organic light emitting diode [organic EL]), inorganic EL, and the like can be preferably used.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

[Production of optical film]
<Preparation of optical film 1>
A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester and sugar ester compound were added to a pressure dissolution tank containing a solvent while stirring. This was completely dissolved while stirring, and Azumi Filter Paper No. The main dope was prepared by filtration using 244.

(Main dope composition)
Resin A: Cellulose acetate propionate (acetyl group substitution degree: 1.64, propionyl group substitution degree: 1.12, weight average molecular weight: 190,000, glass transition temperature: 150 ° C., refractive index: 1.490) 2 parts by mass Resin B: Cellulose diacetate (acetyl group substitution degree: 2.14, weight average molecular weight: 180,000, glass transition temperature: 196 ° C., refractive index: 1.488)
6.7 parts by mass Sugar ester compound A (average substitution degree: 5.5) 2.5 parts by mass Methylene chloride 103 parts by mass Ethanol 19.7 parts by mass

The above was put into a sealed container and dissolved with stirring to prepare a dope. Next, after evaporating the solvent on the belt, the web is peeled from the stainless steel belt, stretched 1.15 times with a tenter at 160 ° C. in the direction perpendicular to the conveying direction, and the drying zone at 120 ° C. is conveyed by a number of rollers. The optical film 1 having an average film thickness of 40 μm was obtained by finishing drying while winding.

<Preparation of optical film 2>
(Dope composition 2)
Polymethyl methacrylate (VB-7103, manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 300,000, glass transition temperature 105 ° C., refractive index 1.490) 55 parts by weight Cellulose acylate (cellulose acetate propionate acyl group total substitution degree 2 .46, acetyl group substitution degree 1.58, propionyl group substitution degree 0.88, weight average molecular weight 190,000, glass transition temperature 170 ° C., refractive index 1.489) 45 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The composition was sufficiently dissolved while heating to prepare a dope.

The produced dope was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 154 N / m.

The solvent of the peeled resin web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at the drying temperature while stretching 1.1 times in the width direction with a tenter at 135 ° C. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

After stretching with a tenter, relaxation was performed at 130 ° C., and then drying was completed while conveying a drying zone at 120 ° C. and 140 ° C. with many rollers, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process of 5 μm was performed, and the film was wound around a core having an initial tension of 220 N / m and a final tension of 110 N / m and an inner diameter of 15.24 cm to obtain an optical film 2 which is a resin film having a sea-island structure.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

The residual solvent amount of the optical film 2 was 0.1%, the film thickness was 60 μm, and the winding length was 4000 m.

<Preparation of optical film 3>
(Dope composition 3)
Polymethyl methacrylate (VB-7103, manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 300,000, glass transition temperature 105 ° C., refractive index 1.490)
55 parts by mass Cellulose acylate (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, weight average molecular weight 200,000, glass transition temperature 140 ° C., refraction (Rate 1.487) 25 parts by mass Cellulose acylate (cellulose acetate propionate acyl group total substitution degree 2.46, acetyl group substitution degree 1.58, propionyl group substitution degree 0.88, weight average molecular weight 190,000, glass transition Temperature 170 ° C., Refractive index 1.489) 20 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope.

The produced dope was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 154 N / m.

The solvent of the peeled resin web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at the drying temperature while stretching 1.1 times in the width direction with a tenter at 135 ° C. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

After stretching with a tenter, relaxation was performed at 130 ° C., and then drying was completed while conveying a drying zone at 120 ° C. and 140 ° C. with many rollers, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process of 5 μm was performed, and the film was wound around a core having an initial tension of 220 N / m and a final tension of 110 N / m and an inner diameter of 15.24 cm, thereby obtaining an optical film 3 which is a resin film having a sea-island structure.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

The residual solvent amount of the optical film 3 was 0.1%, the film thickness was 60 μm, and the winding length was 4000 m.
(Preparation of optical films 4 to 11)
Dopes were produced with the resin compositions shown in Table 1, and various optical films 4 to 11 were produced in the same manner as the optical film 3.

[Evaluation of optical film]
The following measurements / evaluations were performed on the optical films 1 to 11 produced above.

<Measurement of total light transmittance>
Measured every 1 nm in the haze calculation mode using an extra-UV visible near-infrared spectrophotometer (V-670 manufactured by JASCO Corporation), and the average value of the transmittance within the range of 450 to 650 nm was measured as the total light transmittance. Calculated as

<Surface shape observation and measurement of arithmetic average surface roughness Ra>
The film prepared above was observed and analyzed on the front and back surfaces of the optical film using a 3D measurement laser microscope LEXT OLS4000 manufactured by Olympus Corporation. The optical films 1 to 8 according to the present invention formed irregularities due to the sea-island structure. It was confirmed that the comparative optical film did not form the unevenness. In addition, the arithmetic average roughness Ra of the two front and back surfaces of the optical film was determined in accordance with JIS B0601-2001.

<Measurement of image clarity>
The image sharpness of the film is determined by the transmission method according to JIS K7374: 2007, using the image clarity tester ICM-1T manufactured by Suga Test Instruments Co., Ltd. Measurements were made in the range of 0.125 to 2.0 mm.

The measurement and evaluation results are shown in Table 2.

As is apparent from the measurement results of the total light transmittance and the image definition shown in Table 2, it can be seen that the optical film according to the present invention maintains high light transmittance and has light diffusibility. .

<Preparation of polarizing plate>
(Production of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. The uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 20 μm.

(Preparation of photocurable adhesive)
Each of the following components was mixed and then defoamed to prepare a photocurable adhesive liquid. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

(Composition of photocurable adhesive liquid)
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries)
40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass (Preparation of polarizing plate)
Polarizing plates using the optical films 1 to 11 prepared above were prepared as follows.

First, the surface of the optical film was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the adhesive solution prepared above was applied to the corona discharge treated surface of the optical film with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. A polyvinyl alcohol-iodine polarizer prepared as described above was bonded to the obtained adhesive layer.

Similarly, a KC6UY (Konica Minolta Opto Co., Ltd.) film was prepared, and the surface was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the adhesive solution prepared above was applied to the corona discharge treated surface of the film with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. A polarizer of a polarizer having a polarizing plate protective film bonded on one side is bonded to this adhesive layer to obtain a laminate of an optical film / polarizer / KC6UY (Konica Minolta Opto Co., Ltd.) film. It was. Using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), the laminated polarizing plate protective film is irradiated with ultraviolet rays so that the integrated light amount becomes 750 mJ / cm ^2. The adhesive layer was cured.

Thus, using each of the optical films 1 to 11, a polarizing plate in which a polarizer was sandwiched between two optical films was produced.

<Evaluation of polarizing plate>
The following evaluation was performed for each polarizing plate produced using the optical films 1 to 11.

(Polarizer adhesion)
The produced polarizing plate was cut into a square having a size of 5 cm × 5 cm, left in an atmosphere of 23 ° C. and 55% RH for 24 hours, and then peeled off from the corner portion at the interface between the polarizer and the film. This operation was performed with 100 polarizing plates for one type of sample, and the number of polarizing plates in which peeling was observed between the polarizer and the film was counted and evaluated as follows.

◎: 0 to 2 sheets ○: 3 to 5 sheets △: 6 to 20 sheets ×: 21 sheets or more The polarizer adhesion is preferably evaluated as ◯ or ◎.

(Polarizing plate curl)
The polarizing plate was cut into a width direction of 35 mm and a longitudinal direction of 1 mm to prepare a curl measurement sample. This was allowed to stand for 3 days in an atmosphere of 25 ° C. and 55% RH, and then the degree of curl was measured. The curl degree represents the reciprocal of the radius of curvature. Specifically, the curl degree was measured according to the method A of JIS-K7619-1988. The evaluation with respect to the curl degree is as follows.

○: 0 to 5%
Δ: 5-30%
×: 30% to 100%
(Production of display device)
The rear side polarizing plate of a commercially available liquid crystal monitor (manufactured by Samsung, SyncMaster 743BM) was peeled off, and the polarizing plate prepared above was bonded instead. However, when bonding to the liquid crystal cell, the optical film is bonded so that the surface of the optical film faces the backlight side and the absorption axis faces in the same direction as the previously bonded polarizing plate. did. The backlight unit has a configuration of light guide plate / lower diffusion sheet / prism sheet / prism sheet in order from the light source side.

According to the above method, liquid crystal display devices 1 to 11 having the various polarizing plates described above were produced.

<Front brightness>
A signal is input from the video signal generator (VG-848; manufactured by ASTRODESIGN Co., Ltd.) to the manufactured liquid crystal display device to obtain a 256/256 gradation white display on the entire surface, and the method of the liquid crystal display device plane in the dark room The luminance was measured from a line (front) direction with a luminance meter (CS-2000; manufactured by Konica Minolta Sensing). A total of 5 points were measured at an interval of 3 cm from the center point of the screen, one for each of the top and bottom and one for each of the left and right.

Evaluation was performed in the following three stages based on the case where a base material (commercially available cellulose ester film 4UY (manufactured by Konica Minolta Opto)) having no light diffusibility was used on the surface of the backlight side polarizing plate.

○: Almost no decrease (98% to 100% of reference value)
Δ: Slightly decreased (95% or more of the standard value and less than 98%)
X: Decreasing (less than 95% of the reference value)
<Moire>
A signal is input from the video signal generator (VG-848; manufactured by ASTRODESIGN Co., Ltd.) to the manufactured liquid crystal display device, and the entire surface is displayed in gray with 128/256 gradations, and the screen is displayed from various directions under a dark room. The presence or absence of moire was evaluated by visual observation.

◯: Moire is not observed Δ: Moire is observed and slightly anxious ×: Moire is clearly observed Evaluation was performed by five persons, and the evaluation was determined by an average value for each liquid crystal display device. As a level of moiré, ○ or more is practically necessary.

The above evaluation results are summarized in Table 3.

As is clear from the results shown in Table 3, it can be seen that the polarizing plate of the present invention is excellent in the evaluation of polarizer adhesion and polarizing plate curl. Moreover, it turns out that the liquid crystal display device provided with the polarizing plate of this invention is excellent in evaluation of front luminance and moire.

The polarizing plate of the present invention is a polarizing plate that is bonded with sufficient adhesion without causing curling when the optical film and the polarizer are bonded using a photocurable adhesive, and is excellent. It has both light diffusibility and light transmission.

DESCRIPTION OF SYMBOLS 1 Melting pot 3,6,12,15 Filter 4,13 Stock tank 5,14 Liquid feed pump 8,16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roller dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter 1a Light source 2a Light emission source 3a Lower diffusion sheet (or diffusion plate)
4a Light collecting sheet (prism sheet, lens sheet)
5a Upper diffusion sheet 6a Surface light source device (backlight unit)
7a Liquid crystal cell 8a Transparent substrate (glass, plastic)
9a Protective film (or retardation film)
10a Polarizer 11a Protective film 12a Liquid crystal panel 13a Light guide plate 14a Optical film according to the present invention

Claims (7)

1. An optical film containing two or more kinds of resins is a polarizing plate bonded to a polarizer with a photocurable adhesive, the two surfaces of the optical film both have a sea-island structure, and the two surfaces A polarizing plate characterized by having an arithmetic average roughness Ra of 0.03 to 1.5 μm.
2. The optical film contains at least an acrylic resin and a cellulose acylate resin as two or more kinds of resins, and a mass ratio of the acrylic resin and the cellulose acylate resin is within a range of 51:49 to 90:10. The polarizing plate according to claim 1, wherein:
3. The cellulose acylate resin has at least two kinds of cellulose acylates, ie, a cellulose acylate resin having an average acyl group having an average total carbon atom number of less than 6.0 and a cellulose acylate resin of 6.0 or more per glucose unit. The polarizing plate according to claim 2, comprising a rate resin.
4. The cellulose acylate resin has at least an acetyl group or a propionyl group as the acyl group, and the average total number of carbon atoms of the acyl group is less than 6.0 per glucose unit. The polarizing plate according to claim 2 or 3, wherein the substitution degree of propionyl group is 1.0 or less.
5. The polarizing plate according to any one of claims 1 to 4, wherein the photocurable adhesive is a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator.
6. 6. The optical film according to claim 1, wherein the image clarity of the optical film is in a range of 0.8 to 5.0% in a measurement using an optical comb having a width of 0.25 mm. A polarizing plate according to claim 1.
7. A liquid crystal display device, wherein the polarizing plate according to any one of claims 1 to 6 is provided on a backlight source side with respect to a liquid crystal cell.

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