KR20120106590A - Polarizer protective film - Google Patents

Abstract

PURPOSE: A polarizer protecting film is provided to prevent a whitening phenomenon and a rainbow stain due to reflected light. CONSTITUTION: A polarizer protecting film(100) includes a base film(101) with birefringence and a light diffusion layer(102). The light diffusion layer is laminated on the base film. The light diffusion layer has a transmissive resin(103) as a base material and is made by dispersing transmissive corpuscles on the transmissive resin.

Description

Polarizer protective film {POLARIZER PROTECTIVE FILM}

The present invention relates to a polarizer protective film having a light diffusing layer.

In order to prevent scratches on the surface of a display surface of an image display device such as a liquid crystal display, a plasma display panel, a cathode ray tube (cathode ray tube: CRT) display, an organic electroluminescence (EL) display, and the like, protection having high hardness performance Films are generally installed. In addition, visibility is impaired when external light shines on the display surface of the image display device. Therefore, a television or personal computer that values image quality, a video camera or a digital camera used outdoors with strong external light, or a mobile phone that displays using reflected light In some cases, the protective film may be provided with a function of preventing external light from shining in, and an anti-reflective treatment technique using interference by an optical multilayer film or fine irregularities on the surface may scatter incident light to blur the glare image. Anti-glare treatment technology is used. In particular, the latter anti-glare treatment technology is relatively inexpensive, and therefore, the latter is preferably used for applications such as large monitors and personal computers.

In addition, in large screen image display device applications, such as wall-mounted television applications, the necessity of further thinning and weight reduction of the image display device is present, and the protective film responds to the thin large screen of the image display element. The function which reinforces the intensity | strength of an image display element is calculated | required, or the thickness of the protective film itself is calculated | required. As a protective film which meets these requirements, since it is excellent in mechanical strength, durability, and cost, the film containing polyester-based resin is used as a base film, for example. [Japanese Patent Laid-Open No. 2008-3541 (Patent Document) 1) Reference].

Patent Document 1: Japanese Patent Laid-Open No. 2008-3541

When using the film containing polyester-type resin as a base film, since it can adjust to desired intensity | strength and thickness, and it is advantageous in terms of cost, it is usually extended | stretched and used. Since the stretched resin film has birefringence, there was a problem in that rainbow spots derived from retardation were generated and the visibility deteriorated.

In patent document 1, it is described to prevent the rainbow unevenness resulting from the birefringence of a base film by making it into the total haze of 10%-80% of a polarizing plate protective film. However, the removal of the rainbow spot is not only related to the overall haze, and even if the protective film has a total haze within the above range, rainbow spots may occur. In addition, when the total haze is set to a high value, the occurrence of rainbow spots is suppressed, but in this case, there is a problem that so-called "whitening", in which the entire display surface becomes white due to diffused light, becomes a turbid color, is likely to occur.

An object of this invention is to provide the polarizer protective film in which generation | occurrence | production of whitening was suppressed and the generation | occurrence | production of the rainbow spot by the transmitted light mainly resulting from the birefringence of a base film was suppressed.

This invention is made by discovering that the generation | occurrence | production of the rainbow spot by the transmitted light correlates also with the transmission image clarity. The present invention includes the following.

[1] A polarizer protective film having a light diffusing layer,

The total value T _c (%) of the transmission image clarity C _n (%) in the transmission image clarity measurement test satisfies the relationship of the following formula (1), and the total haze value H (%) is the following formula (2) Satisfy the relationship

In the transmission image sharpness measurement test, the amount of light transmitted through the test piece is measured through an optical comb having a width n (mm) moving at a speed of 10 mm / min, orthogonal to the optical axis of the transmitted light,

The transmission image clarity C _n (%) is, the transmission image for the highest value of the amount of transmitted light at the time when the transmitted portion of the optical comb to a beam axis in the sharpness measurement test M _n, the optical comb to the ordinary ray axis When the minimum value of the amount of transmitted light when there is a light shielding portion is m _n , it is calculated by the following equation (3),

The total value of T _c is the width of n (mm) of the optical comb, respectively, 0.125, 0.5, 1, transmission image clarity in the case of _{2 C 0 .125, C 0 .5} , the total value of C _1, C ₂ Polarizer protective film.

0≤T _c ≤125 equation (1)

0≤H≤10 equation (2)

C _n = {(M _n -m _n ) / (M _n + m _n )

[2] The polarizer protective film according to [1], wherein the base film and the light diffusion layer are laminated, and the base film has birefringence.

[3] The polarizer protective film according to [2], wherein the base film has an in-plane retardation value of 400 nm or more.

[4] The polarizer protective film according to [2] or [3], wherein the base film contains polyester resin as a main component.

[5] The polarizer protective film according to any one of [2] to [4], wherein the base film has a thickness of 50 μm or less.

[6] The polarizer protective film according to any one of [1] to [5], wherein the light diffusing layer contains a light transmitting resin and light transmitting fine particles.

[7] The polarizer protective film according to [6], wherein the light transmitting fine particles contain amorphous particles.

According to the polarizer protective film of this invention, generation | occurrence | production of the rainbow spot and whitening by transmitted light are suppressed, and it becomes possible to comprise the image display apparatus with favorable external appearance quality and display quality.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows the preferable example of the polarizer protective film of this invention.
FIG. 2: shows the graph which plotted the relationship between the total haze value H of the polarizer protective film of Example 1, and the optical film of Comparative Examples 1-5, and the total value _Tc of transmission image clarity.

[Polarizer protective film]

The polarizer protective film of this invention has a light-diffusion layer. The light diffusion layer is laminated on the base film, for example. The polarizer protective film may have other layers other than the light-diffusion layer and base film mentioned above.

1 is a schematic cross-sectional view showing a preferred example of the protective film of the present invention. The polarizer protective film 100 shown in FIG. 1 which concerns on this invention is equipped with the base film 101 and the light-diffusion layer 102 laminated | stacked on the base film 101. FIG. The light diffusing layer 102 is a layer based on the light transmitting resin 103, and the light transmitting fine particles 104 are dispersed in the light transmitting resin 103. EMBODIMENT OF THE INVENTION Hereinafter, the polarizer protective film of this invention is demonstrated in detail.

<Optical characteristics of the polarizer protective film>

In the polarizer protective film of the present invention, the total value T _c (%) of the transmission image clarity C _n (%) in the transmission image clarity measurement test is expressed by the following formula (1):

0≤T _c ≤125 equation (1)

Satisfies the relationship, and the total haze value H (%) is expressed by the following equation (2):

0≤H≤10 equation (2)

Lt; / RTI &gt;

The said transmission image sharpness measurement test measures the light quantity of the transmitted light of a test piece (polarizer protective film) through the optical comb of width n (mm) which is orthogonal to the optical axis of transmitted light and moves at a speed of 10 mm / min. Specifically, it measures using a filament measuring device (made by Sugashi Kenki Co., Ltd.). The filamentous measuring instrument is composed of an optical device which vertically injects light transmitted through the slit as a parallel light beam to the test piece, and detects the variation of the detected amount of light as a waveform by detecting an optical device through an optical comb which moves the transmitted light as a waveform. . The ratio of the width | variety of the width | variety and a arm part of an optical comb is 1: 1, the width n (mm) is made into four types of 0.125, 0.5, 1, and 2, and the moving speed is set to 10 mm / min.

Transmission image clarity C _n (%), the transmission image clarity in the measurement test of the optical comb transmission on the beam axis portion (list), the light-blocking of the optical comb to the highest value of the amount of transmitted light on the M _n, light axes of when When the minimum value of the amount of transmitted light when there is a portion (dark portion) is m _n , the following equation (3):

C _n = {(M _n -m _n ) / (M _n + m _n )

Is calculated.

Total value T _c (%) is, of an optical comb width of n (mm) are, respectively, 0.125, 0.5, 1, four transmission image clarity _{C 0 .125 (%), C} 0 .5 (%) in the case of 2 , C ₁ (%), C ₂ (%), and the maximum value that can be taken is 400%.

When the total value T _c (%) satisfies the relationship of the formula (1), and the total haze value H (%) satisfies the relationship of the formula (2), the occurrence of whitening is suppressed and the rainbow caused by transmitted light It becomes possible to provide the polarizer protective film in which generation | occurrence | production of a stain was suppressed.

Here, a "total haze value" means the ratio of the total light transmittance (Tt) which shows the total amount of the light which irradiated and transmitted the light to a polarizer protective film, and the diffused light transmittance (Td) diffused and transmitted by the polarizer protective film. Equation (4) below:

Total haze (%) = (Td / Tt) x 100 (4)

.

The total light transmittance Tt is the sum of the parallel light transmittance Tp and the diffused light transmittance Td that are coaxial with the incident light. The total light transmittance Tt and the diffuse light transmittance Td are values measured based on JIS K7361.

The total haze value of a polarizer protective film is specifically measured as follows. That is, first, in order to prevent the film from bending, by using an optically transparent adhesive, the polarizer protective film is bonded to the base film 101 side to the glass substrate so that the light-diffusion layer 102 becomes the surface, and a test piece is prepared. The total haze value is measured for this test piece. The total haze value was determined by using a haze transmittance meter (e.g., a haze meter "HM-150" manufactured by Murakami Shikisaiki Jutsuken Co., Ltd.) in accordance with JIS K 7136 to determine the total light transmittance (Tt) and the diffuse light transmittance ( Td) is measured and computed by said formula (4).

<Light diffusion layer>

The polarizer protective film 100 shown in FIG. 1 includes a light diffusion layer 102 laminated on the base film 101. The light diffusing layer 102 is a layer based on the light transmitting resin 103, and the light transmitting fine particles 104 are dispersed in the light transmitting resin 103. In addition, you may have another layer (including an adhesive layer) between the base film 101 and the light-diffusion layer 102. FIG.

The light-transmissive resin 103 is not particularly limited as long as it is light-transmissive. Examples of the light-transmissive resin 103 include hardened products of ionizing radiation curable resins and thermosetting resins such as ultraviolet curable resins and electron beam curable resins, and cured products of thermoplastic resins and metal alkoxides. It is available. When ionizing radiation curable resin, thermosetting resin, or metal alkoxide is used, the resin is cured by irradiation or heating of ionizing radiation to form a translucent resin 103. Among these, when used as a polarizer protective film which has high hardness and is provided in the liquid crystal display device surface, since high scratch resistance can be provided, ionizing radiation curable resin is suitable.

As an ionizing radiation curable resin, Polyfunctional acrylate like acrylic acid or methacrylic acid ester of polyhydric alcohol; The polyfunctional urethane acrylate synthesize | combined from the diisocyanate, polyhydric alcohol, the hydroxy ester of acrylic acid or methacrylic acid, etc. are mentioned. In addition to these, polyether resins, polyester resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiolpolyene resins and the like having acrylate functional groups can also be used.

As a thermosetting resin, in addition to the thermosetting urethane resin containing an acryl polyol and an isocyanate prepolymer, a phenol resin, a urea melamine resin, an epoxy resin, an unsaturated polyester resin, and a silicone resin are mentioned.

As a thermoplastic resin, Cellulose derivatives, such as acetyl cellulose, nitrocellulose, acetylbutyl cellulose, ethyl cellulose, and methyl cellulose; Vinyl-based resins such as vinyl acetate and its copolymer, vinyl chloride and its copolymer, vinylidene chloride and its copolymer; Acetal resins such as polyvinyl formal and polyvinyl butyral; Acrylic resins such as acrylic resins and copolymers thereof, methacryl resins and copolymers thereof; Polystyrene resin; Polyamide based resin; Polyester-based resin; Polycarbonate resin etc. are mentioned.

As the metal alkoxide, a silicon oxide matrix based on a silicon alkoxide-based material can be used. Specifically, it is tetramethoxysilane, tetraethoxysilane, etc., and it can be set as an inorganic type or organic-inorganic composite matrix (translucent resin) by hydrolysis or dehydration condensation.

As the light-transmitting fine particles 104 used in the present invention, organic particles or inorganic fine particles having light transparency can be used. Examples include organic fine particles containing acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin, acrylic-styrene copolymer, and the like, calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, glass, and the like. And inorganic fine particles to be mentioned. Moreover, the balloon of an organic polymer, and glass hollow beads can also be used. The light-transmitting microparticles | fine-particles 104 may be comprised from 1 type of microparticles | fine-particles, and may contain two or more types of microparticles | fine-particles. The shape of the light-transmitting fine particles 104 may be any of spherical, flat, plate, needle, and irregular shapes, but the interface between the light-transmitting resin 103 and the light-transmitting fine particles 104 by using the light-transmitting particles of the irregular shape. The fine deviation is given to and the production of the polarizer protective filter in which the total value T _c of the transmitted image clarity satisfies the relationship of the above formula (1) becomes easy. As amorphous translucent microparticles | fine-particles, amorphous silica is mentioned, for example.

Here, it is preferable that they are 0.1 micrometer or more and 30 micrometers or less, and, as for the weight average particle diameter of the translucent microparticles | fine-particles, it is more preferable that they are 0.1 micrometer or more and 5 micrometers or less. If the weight average particle diameter of the translucent microparticles | fine-particles is less than 0.1 micrometer, it may hardly contribute to the internal scattering of visible light in some cases. Moreover, when a weight average particle diameter exceeds 5 micrometers, it may become difficult to manufacture a polarizer protective filter so that all the haze value H may satisfy | fill the relationship of said Formula (2), Furthermore, the light-diffusion layer 102 The whole thickness becomes thick and may hinder the thinning of the display. In addition, the weight average particle diameter of the translucent microparticles | fine-particles 104 is measured using the Coulter multisizer (made by Beckman Coulter) using the Coulter principle (pore electrical resistance method). The translucent microparticles | fine-particles 104 may contain 2 or more types from which a weight average particle diameter differs.

It is preferable to make the refractive index of the translucent microparticle 104 larger than the refractive index of the translucent resin 103, and the difference is preferably in the range of 0.04 to 0.15. By setting the difference in refractive index between the light-transmitting fine particles 104 and the light-transmissive resin 103 within the above ranges, proper internal scattering occurs due to the difference in refractive index between the light-transmitting fine particles 104 and the light-transmitting resin 103, and thus the transmission image clarity of the polarizer protective film. It becomes easy to control so that total value _Tc may satisfy | fill the relationship of said Formula (1).

In addition, it is preferable that the surface (surface on the opposite side to the base film 101) of the light-diffusion layer is formed only of the translucent resin 103. That is, it is preferable that the light-transmitting fine particles 104 do not protrude from the surface of the light diffusion layer 102 and are completely embedded in the light diffusion layer 102. When the translucent microparticles | fine-particles 104 protrude from the surface of the light-diffusion layer 102, it may be difficult to produce a polarizer protective film so that the whole haze value T may satisfy | fill the relationship of said Formula (2).

It is preferable that the layer thickness of the light-diffusion layer 102 is 10 micrometers or more and 20 micrometers or less. When it is less than 10 micrometers, the translucent microparticles | fine-particles 104 may protrude from the surface of the light-diffusion layer 102 in some cases. On the other hand, when it exceeds 20 micrometers, the whole polarizer protective film will become thick, and it will become easy to roll and split, and it is disadvantageous from the point of handling.

In addition, the polarizer protective film of this invention may further be provided with the anti-reflective layer laminated | stacked on the light-diffusion layer 102 shown in FIG. 1 (the surface on the opposite side to the base film 101). The antireflection layer is provided in order to lower the reflectance infinitely, and the antireflection layer can be prevented from shining on the display screen by forming the antireflection layer. Examples of the antireflection layer include a low refractive index layer made of a material lower than the refractive index of the light diffusing layer 102; The laminated structure of the high refractive index layer which consists of a material higher than the refractive index of the light-diffusion layer 102, and the low refractive index layer which consists of a material lower than the refractive index of this high refractive index layer, etc. are mentioned.

<Substrate film>

The base film 101 is a film having birefringence. Preferably, the in-plane retardation value R with respect to the light of wavelength 590nm is 100-2500 nm, More preferably, it is 400-1500 nm. When the in-plane retardation value of the base film 11 is smaller than 100 nm, the rainbow spot which originates in birefringence is hard to generate | occur | produce, and even if it generate | occur | produces, it is hard to be enough to affect the fall of image quality. In-plane retardation value R of the base film 11 is following formula (5):

R = (n _x -n _y ) × d equation (5)

The value defined by.

In formula (5),

n _x : refractive index in the in-plane slow axis direction of the base film,

n _y : refractive index in the in-plane fast axis direction (direction perpendicular to the ground axis direction) of the base film,

d: average thickness of the base film.

The material of the base film 101 is not specifically limited, A well-known material can be used. For example, polyester resins such as polyethylene terephthalate, polyolefin resins such as polyethylene and polypropylene, ethylene-vinyl acetate resins, acrylic resins such as polymethyl methacrylate, cyclic olefin resins such as norbornene resins, and the like. The synthetic polymer containing these, and the natural polymer containing cellulose resins, such as a cellulose diacetate and a cellulose triacetate, are mentioned. Although it is preferable that the base film 101 is colorless and transparent, it may be colored or translucent in the range which does not interfere with defect detectability for the purpose of surface identification etc.

The method of manufacturing the base film 101 using the above-mentioned material is not specifically limited, It can manufacture by well-known methods, such as a solvent casting method and an extrusion method. Moreover, the base film 101 which performed extending | stretching processes, such as uniaxial stretching or biaxial stretching, after film molding can be used. As the base film 101 in which the in-plane retardation value R exists in the range mentioned above, Preferably the base film 101 containing the polyester-type resin which carried out the extending | stretching process is used. For example, the base film 101 containing the polyethylene terephthalate which performed the extending | stretching process is mentioned.

Stretching is normally performed continuously while winding a film roll, and it extends | stretches in the advancing direction of the roll, the advancing direction and the perpendicular direction, or both in a heating furnace. The temperature of a heating furnace is the range from the glass transition temperature vicinity of resin which comprises the base film 101 to glass transition temperature +100 degreeC normally.

The polyester film used as the base film 101 is a film containing polyester as a main component, and may be a single layer film containing polyester as a main component, or a multilayer film having a layer containing polyester as a main component. In addition, the surface treatment may be performed on both surfaces or one surface of these single | mono layer films or a multilayer film, and this surface treatment may be surface modification by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, etc. Thin film formation by application | coating, vapor deposition, etc. of metal etc. may be sufficient. The weight ratio of polyester to the whole polyester film is 50 weight% or more normally, Preferably it is 70 weight% or more, More preferably, it is 90 weight% or more.

Examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, and 1,4-cyclohexanedimethylene terephthalate. You may use the above. Especially, polyethylene terephthalate is used preferably.

Polyethylene terephthalate is polyester which has a structural unit derived from terephthalic acid as a dicarboxylic acid component, and a structural unit derived from ethylene glycol as a diol component, and it is preferable that 80 mol% or more of all the repeating units is ethylene terephthalate. And the structural unit derived from another copolymerization component may be included. Examples of other copolymerization components include isophthalic acid, p-beta -oxyethoxybenzoic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4- carboxyphenyl) ethane, adipic acid, Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, and 1,4-dicarboxycyclohexane, and aliphatic dicarboxylic acids such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, Adducts, diol components such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

These dicarboxylic acid components and diol components can be used in combination of 2 or more type as needed. Moreover, it is also possible to use together oxycarboxylic acids, such as p-oxybenzoic acid, with the said carboxylic acid component and a diol component. As another copolymerization component, the dicarboxylic acid component and / or diol component containing a small amount of amide bond, urethane bond, ether bond, carbonate bond, etc. may be used. As a method for producing polyethylene terephthalate, a so-called direct polymerization method in which terephthalic acid and ethylene glycol and other dicarboxylic acids and / or other diols are directly reacted, or dimethyl ester and ethylene glycol of terephthalic acid and other dicarboxyl as necessary Any production method, such as a so-called transesterification reaction, in which a dimethyl ester of an acid and / or another diol is transesterified, may be applied.

You may mix | blend a well-known additive with polyester as needed, As an example, a lubricant, an antiblocking agent, a thermal stabilizer, antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improvement agent are mentioned. However, when using a polyester film as a base film of an anti-glare film, since transparency is generally needed, it is preferable to keep the addition amount of an additive to the minimum.

It is preferable that the polyester film is uniaxially stretched or biaxially stretched (The polyester film thus uniaxially stretched or biaxially stretched is simply referred to as "stretched polyester film" hereinafter). The stretched polyester film is a film excellent in mechanical properties, solvent resistance, scratch resistance, cost, and the like. The optical film using such a polyester film is excellent in mechanical strength and the like and can be reduced in thickness.

The stretched polyester film can be produced by shape | molding polyester in a film form and performing uniaxial stretching process or biaxial stretching process. By performing an extending | stretching process, the polyester film with high mechanical strength can be obtained. Although the manufacturing method of the stretched polyester film is arbitrary and it is not specifically limited, For example, as a uniaxially-stretched polyester film, the non-oriented film melted polyester and extrusion-molded by sheet form at the temperature more than glass transition temperature. The method of performing a heat setting process after lateral stretch by a tenter is mentioned. In addition, in a biaxially stretched polyester film, after melt | dissolving a polyester and longitudinally extending | stretching the non-oriented film extruded into the sheet form with the tenter at the temperature more than glass transition temperature, after heat-setting, it carries out transverse stretching, The method of performing a heat setting process is mentioned. In this case, extending | stretching temperature is 80 degreeC-130 degreeC normally, Preferably it is 90 degreeC-120 degreeC, and draw ratio is 2.5-6 times normally, Preferably it is 3-5.5 times. When the draw ratio is low, the polyester film tends not to exhibit sufficient transparency.

Moreover, in order to reduce the distortion of an orientation main axis, it is preferable to loosen a polyester film, before performing the heat setting process after extending | stretching. The temperature at the time of a relaxation process is 90 degreeC-200 degreeC normally, Preferably it is 120 degreeC-180 degreeC. The amount of relaxation varies depending on the stretching conditions, and it is preferable to set the amount of relaxation and the temperature at the time of relaxation treatment so that the thermal contraction rate at 150 ° C. of the polyester film after the relaxation treatment becomes 2% or less.

The heat setting treatment temperature can be 180 degreeC-250 degreeC, Preferably it is 200 degreeC-245 degreeC. In the heat setting treatment, first, after performing the heat setting treatment to a predetermined length, it is preferable to further perform the relaxation treatment in the width direction in order to reduce the distortion of the orientation main axis and improve the strength such as heat resistance. In this case, the amount of relaxation is preferably adjusted so that the heat shrinkage at 150 ° C. of the polyester film after the relaxation treatment is 1% to 10%, and more preferably 2% to 5%. The maximum value of the distortion of the orientation main axis of the stretched polyester film used in the present invention is usually 10 degrees or less, preferably 8 degrees or less, and more preferably 5 degrees or less. When the maximum value of the orientation principal axis is larger than 10 degrees, there is a tendency for color defects to increase when bonded to the liquid crystal display screen. In addition, the "maximum value of the distortion of an orientation main axis" of an extending | stretching polyester film can be measured, for example by the retardation film inspection apparatus RETS system manufactured by Otsuka Denshi Corporation.

The thickness of the base film 101 is preferably 20 µm to 100 µm, and more preferably 30 µm to 50 µm. When the thickness of the base film 101 is less than 20 micrometers, it exists in the tendency to be difficult to handle, and when thickness exceeds 100 micrometers, there exists a tendency for the merit of thinning to become small.

<Method of manufacturing polarizer protective film>

Next, the method for manufacturing the polarizer protective film shown in FIG. 1 is demonstrated. The polarizer protective film 100 is preferably manufactured by a method including the following steps (A) and (B).

(A) Coating process which coats the coating liquid containing translucent resin in which translucent microparticles | fine-particles 104 were disperse | distributed on base film 101, and forms a coating layer, and

(B) The hardening process of hardening the said coating layer.

Coating liquid used in the said process (A) is translucent resin 103 which comprises the translucent microparticle 104 and the light-diffusion layer 102, or resin which forms this (for example, ionizing radiation curable resin, thermosetting resin, or metal alkoxide). ) And other components, such as a solvent, as needed. When ultraviolet curable resin is used as resin which forms translucent resin 103, the said coating liquid contains a photoinitiator (radical polymerization initiator). As a photoinitiator, an acetophenone type photoinitiator, a benzoin type photoinitiator, a benzophenone type photoinitiator, a thioxanthone type photoinitiator, a triazine type photoinitiator, an oxadiazole type photoinitiator, etc. are used, for example. Moreover, as a photoinitiator, For example, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'- tetraphenyl- 1, 2'-biimidazole, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, benzyl, 9,10-phenanthrenequinone, camphorquinone, methyl phenylglyoxylate, titanocene compound and the like can also be used. . The usage-amount of a photoinitiator is 0.5-20 weight part with respect to 100 weight part of resin normally contained in a coating liquid, Preferably it is 1-5 weight part. On the other hand, in order to make the optical characteristic and surface shape of a light-diffusion film homogeneous, it is preferable that dispersion of the translucent microparticles 104 in a coating liquid is isotropic dispersion.

The coating on the base film of the coating solution can be performed by, for example, the gravure coating method, the microgravure coating method, the rod coating method, the knife coating method, the air knife coating method, the kiss coating method, the die coating method, or the like. In coating a coating liquid, it is preferable to adjust a coating layer thickness so that the layer thickness of the light-diffusion layer 102 after hardening may be 10 micrometers or more and 20 micrometers or less as mentioned above.

Various surface treatments may be performed on the surface (light diffusion layer side surface) of the base film 101 for the purpose of improving the coating property of the coating liquid or improving the adhesiveness with the light diffusing layer 102. Examples of the surface treatment include corona discharge treatment, glow discharge treatment, acid surface treatment, alkali surface treatment, ultraviolet irradiation treatment, and the like. Moreover, you may make it form other layers, such as a primer layer, on a base film, and to coat a coating liquid on another layer.

Moreover, in order to improve the adhesiveness of the polarizer protective film and polarizer of this invention, it is preferable to make the surface (surface on the opposite side to a light-diffusion layer) of the base film 101 hydrophilized by various surface treatment.

In the said process (B), a coating layer is hardened. When ionizing radiation curable resin, thermosetting resin, or a metal alkoxide is used as resin which forms translucent resin 103, the said coating layer is formed, if necessary, drying (solvent removal) is performed, and irradiation of ionizing radiation is performed. (In the case of using ionizing radiation curable resin) or heating (in case of using thermosetting resin or metal alkoxide), the coating layer is cured. The ionizing radiation can be appropriately selected from ultraviolet rays, electron beams, near ultraviolet rays, visible light, near infrared rays, infrared rays, X rays, and the like depending on the type of resin contained in the coating solution. Among them, ultraviolet rays and electron beams are preferable, and handling is particularly easy. Ultraviolet light is preferable because high energy can be obtained.

As the ultraviolet light source, for example, low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, carbon arc lamp, metal halide lamp, xenon lamp and the like can be used. Moreover, ArF excimer laser, KrF excimer laser, an excimer lamp, a synchrotron radiation, etc. can also be used. Among these, ultra high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, xenon arcs, and metal halide lamps are preferably used.

Moreover, as an electron beam, it emits from various electron beam accelerators, such as a cockcroft-walton type, van de graaff type, a resonance transformation type, an insulation core transformation type, a linear type, a dynamtron type, and a high frequency type. Electron beams having an energy of 50 keV? 1000 keV, preferably 100 keV? 300 keV.

_Tc and H in a polarizer protective film can be adjusted to the range prescribed | regulated by this invention, for example by the method shown below. First, a polarizer protective film is manufactured by the above-mentioned material and method, and _Tc and H are measured. As a result, when the value of T _c is too high, either one of the procedures or two of these treatments may be increased, the particle size of the transparent particles may be increased, or the layer thickness of the light diffusing layer may be thickened. When more than two are combined, and the value of H is too high, the addition number of translucent microparticles | fine-particles may be reduced, the treatment of any of what makes the shape of a translucent microparticles spherical, or these treatments may be combined, and a polarizer protective film is again prepared. It _prepares and the _Tc and H are measured. The manufacture of the said polarizer protective film and the measurement of its _Tc and H are repeated until it becomes the value of target _Tc and the value of H.

[Polarizing Plate]

The polarizer protective film of this invention is bonded to the surface of a polarizer, and comprises the polarizing plate containing a polarizer and a polarizer protective film. According to the polarizer protective film of this invention, generation | occurrence | production of whitening is suppressed, generation | occurrence | production of the rainbow spot by the transmitted light is further suppressed, and mechanical strength is also excellent, The polarizing plate using this is suppressed generation | occurrence | production of whitening similarly to this, and rainbow The occurrence of unevenness is further suppressed, and the polarizing plate also has excellent mechanical strength. As a polarizer, a well-known polarizer can be used. A polarizer generally contains the polyvinyl alcohol-type resin film by which the iodine or dichroic dye was adsorption-oriented. The polarizer protective film of this invention is bonded to at least one surface of a polarizer, and a polarizing plate is comprised. Both the polarizing plate arrange | positioned and used at the visual recognition side of an image display element, and the polarizing plate arrange | positioned and used at the back side can be comprised. For example, a polarizer protective film and a polarizer can be arrange | positioned so that the light-diffusion layer 102, the base film 101, and a polarizer may be laminated | stacked from the visual recognition side, and a polarizing plate of a visual recognition side can be comprised. For example, a polarizer protective film and a polarizer can be arrange | positioned so that a polarizer, a base film 101, and the light-diffusion layer 102 may be laminated | stacked from the visual recognition side, and a polarizing plate of a back side can be comprised. The polarizer protective film concerning this invention may be bonded to both surfaces of one polarizer, and a polarizing plate may be comprised.

[Image display device]

The polarizing plate using the polarizer protective film of this invention is used with an image display element, and comprises an image display apparatus. Here, the liquid crystal panel which has the liquid crystal cell in which the liquid crystal was enclosed between the upper and lower substrates, and changes the orientation state of a liquid crystal by voltage application is typical, and displays an image. Thus, the image display apparatus provided with the polarizer protective film of this invention suppresses generation | occurrence | production of the rainbow spot by whitening and transmitted light in a display screen, and becomes excellent in mechanical strength.

Example

Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples. In addition, the measuring method of the optical characteristic of the polarizer protective film in the following examples, and the weight average particle diameter of translucent microparticles | fine-particles is as follows.

(a) Total value T _c of transmitted image clarity C _n

The transmission image clarity measurement test mentioned above was performed using a filamentous measuring instrument (made by Sugashi Kenki Co., Ltd.), and the transmission image clarity C0 when the width of an optical comb is 0.125 mm, 0.5 mm, 1 mm, and 2 mm, respectively _. was calculated on the basis of a _{.125, C 0 .5, C 1} , C 2 in formula (3). And it was calculated to _{.125 0} C, _0.5 C, the total value of _{C 1,} C ₂ T _c.

(b) Total haze value H

Diffusion diffused and transmitted by total light transmittance (Tt) and a polarizer protective film using the haze transmittance | permeability meter (Hazmeter "HM-150" by Murakami Shikisai Jutsuken Co., Ltd.) based on JISK 7136. The light transmittance Td was measured and the total haze value H was computed based on Formula (4).

(c) weight average particle diameter of the light transmitting fine particles

It measured using the Coulter multisizer (manufactured by Beckman Coulter) using the Coulter principle (pore electric resistance method).

&Lt; Example 1 >

92 parts by weight of acrylic ultraviolet curable resin [100% of solid content, brand name: light acrylate DPE-6A, manufactured by Kyoeisha Kagaku Co., Ltd.] and 8 parts by weight of amorphous silica having an average particle diameter of 1.3 μm (Coulter principle). AZ-204, manufactured by Tosoh Silica Co., Ltd., 0.24 parts by weight of a dispersant [trade name: DISPERBYK102, manufactured by Big Chemi Japan Co., Ltd.], 0.16 parts by weight of anti-settling agent [brand name: BYK411, manufactured by Big Chemi Japan Co., Ltd.] It mixed with the fur and obtained the dispersion (A). To 47.6 parts by weight of the dispersion, 2.4 parts by weight of a photoinitiator (trade name: IRGACURE184, manufactured by Chiba Specialty Chemicals Co., Ltd.), 25 parts by weight of toluene, and 25 parts by weight of isobutyl alcohol were mixed and stirred with a dispersing coating solution ( B) was obtained. Coating liquid (B) was apply | coated to the 38-micrometer polyethylene terephthalate (PET) film [brand name: Lumira, Toray Corporation make, in-plane retardation value 1000 nm] with a # 10 bar coater, and 300 mJ / cm <2> of It hardened | cured by ultraviolet-ray, and the polarizer protective film was obtained.

&Lt; Comparative Example 1 &

As the optical film of the comparative example 1, it is mainly a pentaerythritol tetraacrylate (PETA) and trimethylolhexyl on a biaxially stretched polyethylene terephthalate (PET) film (base film) (brand name: Lumira, Toray Corporation make). An optical film having an antiglare layer formed of lactone (HDI) and not containing light-transmitting fine particles in the antiglare layer was used.

Comparative Example 2

As an optical film of the comparative example 2, a pentaerythritol tetraacrylate (PETA) and triallyl are mainly on a biaxially stretched polyethylene terephthalate (PET) film (base film) (brand name: Lumira, Toray Corporation make). It has a hard coat layer formed of isocyanurate (trade name: TAIC®) and isophorone diisocyanate (IPDI), and has a perfluoropolyether (antifouling agent) and a weight average particle diameter in the hard coat layer of 6 탆. The optical film containing phosphorescent microparticles | fine-particles (copolymer of styrene, ethylene glycol dimethacrylate (EDMA), and methyl methacrylate (MMA)) was used.

&Lt; Comparative Example 3 &

As the optical film of the comparative example 3, it is mainly a pentaerythritol tetraacrylate (PETA) and isophorone di on a biaxially stretched polyethylene terephthalate (PET) film (base film) (brand name: Lumira, Toray Corporation make). Light-transmitting fine particles (styrene, ethylene glycol dimethacrylate (EDMA), and methyl methacrylate (MMA)) having a hard coat layer formed of isocyanate (IPDI) and having a weight average particle diameter of 6.5 μm in the hard coat layer. Copolymer), an optical film containing Al particles having a weight average particle diameter of 100 nm and Mg aggregates.

&Lt; Comparative Example 4 &

As the optical film of the comparative example 4, it is mainly pentaerythritol tetraacrylate (PETA) and isophorone diisocyanate on a biaxially stretched polyethylene terephthalate (PET) film (base film) (brand name: Lumira, Toray Corporation make). An optical film having a hard coat layer formed of IPDI) and containing light-transmitting fine particles (copolymer of styrene and ethylene glycol dimethacrylate) having a weight average particle diameter of 3 µm in the hard coat layer was used.

&Lt; Comparative Example 5 &

As an optical film of Comparative Example 5, a hard coat layer mainly formed of pentaerythritol tetraacrylate (PETA) on a biaxially stretched polyethylene terephthalate (PET) film (base film) (trade name: Lumira, manufactured by Toray Industries, Inc.). And an optical film containing amorphous silica fine particles in a hard coat layer.

(Fabrication of liquid crystal display device)

Moreover, the liquid crystal display device was produced using the obtained polarizer protective film of Example 1 and the optical film of Comparative Examples 1-4, and the rainbow unevenness and whitening by transmitted light were evaluated in accordance with the following method. First, the visual recognition side polarizing plate of the visual recognition side polarizing plate is peeled off from the liquid crystal display device "AQUOS (registered trademark) LC-20AX5" of Sharp Co., Ltd., Instead, the polarizer protective film of Example 1, the comparative examples 1-4 The polarizing plate which bonded each optical film of this as a visual recognition side protective film was bonded by the original polarizing plate in the coaxial direction, and the liquid crystal display device was produced.

(Evaluation of the rainbow stain)

The obtained liquid crystal display is white-displayed, and generation | occurrence | production of the rainbow spot by the transmitted light is based on the following criteria:

A: Almost no rainbow stain

C: Rainbow stains are clearly visible

According to, visually confirmed and evaluated. Table 1 shows the results.

(Evaluation of white flower)

Black display of the obtained liquid crystal display device, and whitening of the black display in the room which lit a fluorescent lamp is based on the following criteria:

A: clear black, less whitening

C: Black is whitening

According to, visually confirmed and evaluated. Table 1 shows the results.

As can be seen from Table 1, the polarizer protective film of Example 1 in which the total value T _c of the transmission image clarity satisfies the relationship of Formula (1), and the total haze value H satisfies the relationship of Formula (2). The generation of rainbow spots by the transmitted light was suppressed, and the occurrence of whitening was suppressed.

(Interpretation of test results)

FIG. 2: shows the graph which plotted the relationship between the total haze value H of the polarizer protective film of Example 1 of Table 1, and the optical film of Comparative Examples 1-5, and the total value _Tc of transmission image clarity.

As shown in FIG. 2, the relationship of the straight line 200 is from the plot point of the relationship between the total haze value H of the optical film (general optical film) of Comparative Examples 1-5 and the total value T _c of the transmission image clarity. Derived. On the other hand, the plot point of Example 1 deviated greatly from the straight line 200. In the relationship with the straight line 200, if the plot point of the relationship between the total haze value H and the total value T _c of the transmission image clarity is positioned in the peripheral region 201 of Example 1, the transmitted light is the same as in Example 1 It was predicted that the image display device in which the generation of the rainbow spots by the ink was suppressed and the occurrence of the whitening was suppressed was predicted, and the relationship between the equations (1) and (2) was derived.

Claims (7)

As a polarizer protective film which has a light-diffusion layer,
The total value T _c (%) of the transmission image clarity C _n (%) in the transmission image clarity measurement test satisfies the relationship of the following formula (1), and the total haze value H (%) is the following formula (2) Satisfy the relationship
The transmission image sharpness measurement test is to measure the amount of light transmitted through the test piece through an optical comb having a width n (mm) orthogonal to the optical axis of the transmitted light and moving at a speed of 10 mm / min,
The transmission image clarity C _n (%) is, the transmission image for the highest value of the amount of transmitted light at the time when the transmitted portion of the optical comb to a beam axis in the sharpness measurement test M _n, the optical comb to the ordinary ray axis When the minimum value of the amount of transmitted light when there is a light shielding portion is m _n , it is calculated by the following equation (3),
The total value of T _c is the width of n (mm) of the optical comb, respectively, 0.125, 0.5, 1, transmission image clarity in the case of _{2 C 0 .125, C 0 .5} , the total value of C _1, C ₂ Polarizer protective film.
0≤T _c ≤125 equation (1)
0≤H≤10 equation (2)
C _n = {(M _n -m _n ) / (M _n + m _n ) The substrate film and the light diffusion layer are laminated,
The said base film is a polarizer protective film which has birefringence. The said base film is a polarizer protective film of Claim 2 whose in-plane retardation value is 400 nm or more. The polarizer protective film of Claim 2 in which the said base film has polyester resin as a main component. The said base film is a polarizer protective film of Claim 2 whose thickness is 50 micrometers or less. The polarizer protective film of claim 1, wherein the light diffusing layer comprises a light transmitting resin and light transmitting fine particles. The polarizer protective film according to claim 6, wherein the light transmitting fine particles contain amorphous fine particles.

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