KR101895077B1 - Polarizer protective film - Google Patents

Abstract

The present invention is characterized in that the total value T _c (%) of the transmitted image sharpness C _n (%) in the transmitted image sharpness measurement test satisfies the relation of the following formula (1) and the total haze value H And a polarizer protective film having a light-diffusing layer satisfying the relationship of the following formula (2). The total value T _c is a total value of the transmitted image sharpness C _{0. 125} , C _{0 .5} , C ₁ , and C ₂ when the width n (mm) of the optical comb is 0.125, 0.5,
0? T _c? 125 (1)
0 ≤ H ≤

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 the display screen of an image display device such as a liquid crystal display, a plasma display panel, a cathode ray tube (CRT) display, and an organic electroluminescence (EL) display, Film is generally installed. Further, since the visibility is impaired when the external light is reflected on the display surface of the image display apparatus, the image is displayed on a television or a personal computer with an emphasis on image quality, a video camera or a digital camera used in outdoor with strong external light, Or the like, a function of preventing external light from entering the protective film may be imparted to the protective film. In this case, anti-reflection treatment technology using interference by the optical multilayer film or fine irregularities on the surface may be used to scatter the incident light, An anti-glare treatment technique is used. Particularly, the latter anti-glare processing technology is relatively inexpensive and thus is preferably used for applications such as a large-sized monitor and a personal computer.

Further, in the use of a large-screen image display device, for example, in the case of a wall-hanging television, the necessity of further thinning and lightening of the image display device is becoming clear, A function of reinforcing the strength of the image display element is required, or the protective film itself is required to be thinned. As a protective film suitable for these demands, a film containing a polyester-based resin is used as a base film, for example, since it is excellent in terms of mechanical strength, durability and cost (JP-A-2008-3541 1).

Patent Document 1: JP-A-2008-3541

When a film containing a polyester-based resin is used as a base film, it can be adjusted to a desired strength and thickness and is cost-effective, so that it is usually stretched and used. Since the stretched resin film has birefringence, a rainbow unevenness originating from a retardation is generated and the visibility is deteriorated.

Patent Document 1 discloses that rainbow stains due to birefringence of a base film are prevented by setting the total haze of the polarizing plate protective film within a range of 10% to 80%. However, elimination of rainbow stains is not only related to the total haze, but even in the case of a protective film having a total haze within the above range, rainbow stains may occur. In addition, when the total haze is set to a high value, occurrence of rainbow stains is suppressed. However, in this case, there arises a problem that so-called " whitening "

An object of the present invention is to provide a polarizer protective film in which occurrence of whitening is suppressed and generation of rainbow stains due to transmitted light mainly caused by birefringence of the base film is suppressed.

The present invention has been made in view of the fact that the occurrence of rainbow stains by transmitted light has a correlation with the clarity of transmitted images. The present invention includes the following.

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

Transmission image clarity total value of C _n (%) T _c and (%) satisfy the relationship of the formula (1), and to the entire haze value H (%) Formula (2) in the transmission image clarity measured test Lt; / RTI >

The transmitted image sharpness measurement test is carried out by measuring an amount of transmitted light of a test piece through an optical comb having a width n (mm) perpendicular to the ray axis of transmitted light and moving at a speed of 10 mm / min,

The transmitted image sharpness C _n (%) is defined as M _n , where M _n is the maximum value of the amount of transmitted light when the transmitted portion of the optical comb exists on the optical axis in the transmitted image sharpness measurement test, When the minimum value of the amount of transmitted light when there is a shielding portion is m _n , it is calculated by the following formula (3)

The total value T _c is a total value of transmitted image sharpness C _{0. 125} , C _{0 .5} , C ₁ , and C ₂ when the width n (mm) of the optical comb is 0.125, 0.5, Polarizer protective film.

0? T _c? 125 (1)

0 ≤ H ≤

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

[2] A polarizer protective film according to [1], wherein a 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 comprises a 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 comprises a light-transmitting resin and a light-transmitting fine particle.

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

INDUSTRIAL APPLICABILITY According to the polarizer protective film of the present invention, iridescent spots and whitening due to transmitted light are suppressed, and an image display device having excellent appearance quality and display quality can be constructed.

1 is a schematic cross-sectional view showing a preferred example of the polarizer protective film of the present invention.
2 is a graph plotting the relationship between the total haze value H of the polarizer protective film of Example 1 and the optical films of Comparative Examples 1 to 5 and the total value T _c of the transmitted image sharpness.

[Polarizer Protective Film]

The polarizer protective film of the present invention has a light diffusion layer. The light diffusion layer is laminated, for example, on a base film. The polarizer protective film may have a separate layer other than the light diffusion layer and the base film described above.

1 is a schematic sectional view showing a preferred example of the protective film of the present invention. The polarizer protective film 100 shown in Fig. 1 according to the present invention comprises a base film 101 and a light diffusion layer 102 laminated on the base film 101. Fig. The light-diffusing layer 102 is a layer based on the light-transmitting resin 103 and is formed by dispersing the light-transmitting fine particles 104 in the light-transmitting resin 103. Hereinafter, the polarizer protective film of the present invention will be described in more detail.

≪ Optical properties of polarizer protective film >

The polarizer protective film of the present invention is characterized in that the total value T _c (%) of the transmitted image sharpness C _n (%) in the transmitted image sharpness measurement test satisfies the following expression (1)

0? T _c? 125 (1)

And the total haze value H (%) satisfies the following expression (2):

0 ≤ H ≤

Lt; / RTI >

In the transmitted image sharpness measurement test, the light quantity of the transmitted light of the test piece (polarizer protective film) is measured through an optical comb having a width n (mm) which is orthogonal to the ray axis of the transmitted light and moves at a speed of 10 mm / min. Specifically, the measurement is carried out using a mapping meter (manufactured by Suga Shikeki Co., Ltd.). The mismatch measuring device is constituted by an optical device that vertically enters a specimen with light transmitted through a slit, detects the transmitted light through an optical comb to be moved, and a metering device that records fluctuation of the detected light amount as a waveform . In the optical comb, the ratio of the width of the name portion to the width of the arm portion is 1: 1, and the width n (mm) is set to 0.125, 0.5, 1, and 2, and the moving speed is 10 mm / min.

The transmitted image sharpness C _n (%) is defined as M _n , the maximum value of the amount of transmitted light when a transmitted portion (list portion) of the optical comb is present on the optical axis in the transmitted image sharpness measurement test, And m _n is the minimum value of the amount of transmitted light when there is a portion (arm portion), the following expression (3):

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

.

The total value T _c (%) is calculated from the four transmitted image sharpness C _{0. 125} (%), C _{0 .5} (%) in the case where the width n (mm) of the optical comb is 0.125, 0.5, , C ₁ (%) and C ₂ (%), so the maximum value that can be taken is 400%.

The occurrence of whitening is suppressed by the total value T _c (%) satisfying the relation of the above formula (1) and the total haze value H (%) satisfying the relation of the above formula (2) It becomes possible to provide a polarizer protective film in which the occurrence of stains is suppressed.

Here, the "total haze value" is a value obtained by subtracting the total light transmittance (Tt) representing the total amount of light transmitted by irradiating light to the polarizer protective film from the ratio of the diffused light transmittance (Td) diffused and transmitted by the polarizer protective film (4) below:

Total Haze (%) = (Td / Tt) x 100 Equation (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 diffused light transmittance (Td) are values measured in accordance with JIS K 7361.

The total haze value of the polarizer protective film is specifically measured as follows. That is, first, in order to prevent warping of the film, a polarizer protective film is bonded to the glass substrate on the side of the base film 101 so that the light-diffusing layer 102 becomes the surface using an optically transparent pressure-sensitive adhesive, The total haze value of the test piece is measured. The total haze value is calculated by dividing the total light transmittance (Tt) and the diffuse light transmittance (占 퐉) by using a haze transmittance meter conforming to JIS K 7136 (e.g., haze meter " HM- 150 ", manufactured by Murakami Shikisai, Td) is measured and calculated by the above equation (4).

≪ Light diffusion layer &

The polarizer protective film 100 shown in FIG. 1 has a light diffusion layer 102 laminated on a base film 101. The light-diffusing layer 102 is a layer based on the light-transmissive resin 103, and the light-transmitting fine particles 104 are dispersed in the light-transmitting resin 103. On the other hand, another layer (including an adhesive layer) may be provided between the base film 101 and the light diffusion layer 102.

The translucent resin 103 is not particularly limited as far as it has translucency. Examples of the translucent resin 103 include an ionizing radiation curable resin such as an ultraviolet curable resin and an electron beam curable resin, a cured product of a thermosetting resin, a thermoplastic resin and a cured product of a metal alkoxide Can be used. When an ionizing radiation curing resin, a thermosetting resin or a metal alkoxide is used, the resin is cured by irradiation with ionizing radiation or heating to form the light transmitting resin 103. Among them, an ionizing radiation curable resin is suitable because it can give high scratch resistance when used as a polarizer protective film having a high hardness and provided on the surface of a liquid crystal display device.

Examples of ionizing radiation curable resins include multifunctional acrylates such as acrylic acid or methacrylic acid esters of polyhydric alcohols; Polyfunctional urethane acrylates synthesized from diisocyanates, polyhydric alcohols and hydroxy esters of acrylic acid or methacrylic acid, and the like. In addition to these, a polyether resin having an acrylate functional group, a polyester resin, an epoxy resin, an alkyd resin, a spiroacetal resin, a polybutadiene resin, a polythiol polyene resin and the like can also be used.

Examples of the thermosetting resin include phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin in addition to a thermosetting urethane resin including an acrylic polyol and an isocyanate prepolymer.

Examples of the thermoplastic resin include cellulose derivatives such as acetylcellulose, nitrocellulose, acetylbutylcellulose, ethylcellulose, and methylcellulose; Vinyl resins such as vinyl acetate and its copolymers, vinyl chloride and its copolymers, vinylidene chloride and copolymers thereof; Acetal resins such as polyvinyl formal, polyvinyl butyral and the like; Acrylic resins such as acrylic resins and their copolymers, methacrylic resins and their copolymers; Polystyrene type resin; Polyamide based resin; Polyester-based resin; And polycarbonate-based resins.

As the metal alkoxide, a silicon oxide-based matrix using a silicon alkoxide-based material as a raw material can be used. Specifically, tetramethoxysilane, tetraethoxysilane or the like can be used, and an inorganic or organic-inorganic composite matrix (translucent resin) can be obtained by hydrolysis or dehydration condensation.

As the translucent fine particles 104 used in the present invention, organic fine particles or inorganic fine particles having translucency can be used. Examples thereof include organic fine particles including acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin, acryl-styrene copolymer and the like, calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, , And the like. Balloons or glass hollow beads of organic polymers may also be used. The light-transmitting fine particles 104 may be composed of one kind of fine particles or two or more kinds of fine particles. The shape of the light transmitting fine particles 104 may be any of a spherical shape, a flat shape, a plate shape, a needle shape and an irregular shape. However, by using the light transmitting fine particles 104 of the indefinite shape, And it is easy to manufacture a polarizer protection filter in which the total value T _c of the transmitted image sharpness satisfies the relation of the above formula (1). As the translucent fine particles of irregular shape, for example, amorphous silica can be mentioned.

Here, the weight average particle diameter of the light-transmitting fine particles 104 is preferably 0.1 mu m or more and 30 mu m or less, more preferably 0.1 mu m or more and 5 mu m or less. If the weight average particle diameter of the light-transmitting fine particles 104 is less than 0.1 占 퐉, the light-transmitting fine particles 104 may not contribute substantially to the internal scattering of visible light. In addition, when the weight average particle diameter exceeds 5 占 퐉, it may become difficult to manufacture the polarizer protective filter so that the total haze value H satisfies the relationship of the formula (2). In addition, The thickness of the entire body becomes large, which may interfere with the thinness of the display. The weight average particle diameter of the light-transmitting fine particles 104 is measured using a Coulter multisizer (manufactured by Beckman Coulter Co.) using the core-breaker principle (pore electric resistance method). The light transmitting fine particles 104 may include two or more kinds of particles having different weight average particle diameters.

It is preferable that the refractive index of the light transmitting fine particle 104 is larger than the refractive index of the light transmitting resin 103, and the difference is preferably in the range of 0.04 to 0.15. By setting the refractive index difference between the light transmitting fine particles 104 and the light transmitting resin 103 within the above range, appropriate internal scattering due to the difference in refractive index between the light transmitting fine particles 104 and the light transmitting resin 103 occurs, It is easy to control so that the total value T _c satisfies the relationship of the above formula (1).

The surface of the light-diffusing layer (the surface opposite to the base film 101) is preferably formed only by the light-transmitting resin 103. That is, it is preferable that the light-transmitting fine particles 104 are not completely protruded from the surface of the light-diffusing layer 102 but are completely buried in the light-diffusing layer 102. When the light-transmitting fine particles 104 protrude from the surface of the light diffusing layer 102, it may be difficult to produce a polarizer protective film so that the total haze value H satisfies the relation of the formula (2).

The thickness of the light-diffusing layer 102 is preferably 10 mu m or more and 20 mu m or less. When the thickness is less than 10 탆, the light-transmitting fine particles 104 sometimes protrude from the surface of the light-diffusing layer 102. On the other hand, if it exceeds 20 탆, the whole polarizer protective film becomes thick, which makes it easy to be rolled or split, and is disadvantageous in terms of handling.

On the other hand, the polarizer protective film of the present invention may further include an antireflection layer laminated on the light diffusing layer 102 (the side opposite to the base film 101) shown in Fig. The antireflection layer is provided to minimize the reflectance, and it is possible to prevent the antireflection layer from being reflected on the display screen due to the formation of the antireflection layer. As the antireflection layer, a low refractive index layer made of a material lower than the refractive index of the light diffusion layer 102; A lamination structure of a high refractive index layer made of a material higher than the refractive index of the light diffusing layer 102 and a low refractive index layer made of a material lower than the refractive index of the high refractive index layer.

<Base film>

The base film 101 is a film having birefringence. Preferably, the in-plane retardation value (R) for light with a wavelength of 590 nm is 100 to 2,500 nm, more preferably 400 to 1,500 nm. When the retardation value in the plane of the base film 11 is smaller than 100 nm, rainbow stains derived from birefringence are unlikely to occur and even if they occur, it is hard to affect the deterioration of image quality. The retardation value R in the plane of the base film 11 is expressed by the following equation (5):

R = (n _x -n _y ) x d Equation (5)

.

In equation (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 orthogonal to the slow axis direction) of the base film,

d is the average thickness of the base film.

The material of the base film 101 is not particularly limited and a known material can be used. For example, a polyester resin such as polyethylene terephthalate, a polyolefin resin such as polyethylene or polypropylene, an ethylene-vinyl acetate resin, an acrylic resin such as polymethyl methacrylate, a cycloolefin resin such as norbornene resin And natural polymers including cellulose acetate and cellulose-based resins such as cellulose acetate triacetate. The base film 101 is preferably colorless and transparent, but may be colored or semitransparent for the purpose of, for example, identifying the surface, without deteriorating the defect detection property.

The method for producing the base film 101 using the above-mentioned materials is not particularly limited, and the base film 101 can be produced by a known method such as a solvent casting method or an extrusion method. After the film formation, the base film 101 subjected to the stretching treatment such as uniaxial stretching or biaxial stretching can be used. As the base film 101 whose in-plane retardation value R is within the above-mentioned range, a base film 101 comprising a polyester resin subjected to stretching treatment is preferably used. For example, a base film 101 comprising polyethylene terephthalate subjected to stretching treatment can be mentioned.

Stretching is usually carried out while winding a film roll, and is stretched in the heating furnace in the direction of advancement of the roll, in the direction perpendicular thereto, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the resin constituting the base film 101 to the glass transition temperature + 100 占 폚.

The polyester film used as the base film 101 may be a film containing polyester as a main component, a single layer film containing polyester as a main component, or a multilayer film having a layer mainly composed of polyester. The surface treatment may be performed on both sides or one side of the single layer film or the multilayer film. The surface treatment may be surface modification by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, etc., A thin film may be formed by coating or vapor deposition of metal or the like. The weight ratio of the polyester to the entire polyester film is generally 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more.

Examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate and 1,4-cyclohexanedimethylene terephthalate. If necessary, two kinds of these polyesters Or more may be used. Among them, polyethylene terephthalate is preferably used.

Polyethylene terephthalate is a polyester having a constituent unit derived from terephthalic acid as a dicarboxylic acid component and a constituent unit derived from ethylene glycol as a diol component, and it is preferable that 80 mol% or more of the total repeating units are ethylene terephthalate And may contain a constituent unit derived from another copolymerizable component. 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 may be used in combination of two or more as necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid together with the carboxylic acid component or the diol component. As the other copolymerization component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used. Examples of the method for producing polyethylene terephthalate include a so-called direct polymerization method in which terephthalic acid is directly reacted with ethylene glycol and, if necessary, another dicarboxylic acid and / or other diol, a direct polymerization method in which terephthalic acid is reacted with dimethylester and ethylene glycol, A transesterification reaction method in which a dimethyl ester of an acid and / or another diol is transesterified, and the like, can be applied.

The polyester may be blended with known additives, if necessary. Examples thereof include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light stabilizers, and impact resistance improvers. However, when a polyester film is used as a substrate film of an antiglare film, since transparency is generally required, it is preferable to suppress the addition amount of the additive to a minimum.

The polyester film is preferably uniaxially or biaxially stretched (the uniaxially or biaxially stretched polyester film is hereinafter simply referred to as "stretched polyester film"). The stretched polyester film is 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 can be reduced in thickness.

The stretched polyester film can be produced by forming the polyester into a film shape and then subjecting it to a uniaxial stretching treatment or a biaxial stretching treatment. By conducting the stretching treatment, a polyester film having high mechanical strength can be obtained. There is no particular limitation on the method for producing the stretched polyester film, and for example, as the uniaxially stretched polyester film, a polyester film is produced by melting a polyester film and extruding the film in a sheet form at a temperature not lower than the glass transition temperature Followed by transverse stretching with a tenter, followed by heat fixing treatment. In the biaxially oriented polyester film, the polyester is melted and the unoriented film extruded in a sheet form is longitudinally stretched by a tenter at a temperature not lower than the glass transition temperature, followed by thermal fixation treatment, And a method of performing a heat fixing process. In this case, the stretching temperature is usually 80 to 130 占 폚, preferably 90 to 120 占 폚, and the stretching magnification is usually 2.5 to 6 times, preferably 3 to 5.5 times. When the draw ratio is low, the polyester film tends not to show sufficient transparency.

Further, in order to reduce the distortion of the orientation principal axis, it is preferable that the polyester film is relaxed before the heat fixation treatment after stretching is performed. The temperature at the time of relaxation treatment is usually 90 ° C to 200 ° C, preferably 120 ° C to 180 ° C. The amount of relaxation depends on stretching conditions, and it is preferable to set the relaxation amount and the temperature at the time of relaxation treatment so that the heat shrinkage rate of the polyester film after the relaxation treatment at 150 ° C is 2% or less.

The heat setting treatment temperature may be 180 占 폚 to 250 占 폚, and preferably 200 占 폚 to 245 占 폚. In the heat fixation treatment, it is preferable to further perform the widthwise relaxation treatment in order to reduce the distortion of the orientation main axis after heat fixation treatment is performed with a predetermined length and to improve the strength such as heat resistance. The amount of relaxation in this case is preferably adjusted so that the heat shrinkage rate of the polyester film after the relaxation treatment at 150 ° C is 1% to 10%, more preferably 2% to 5%. The maximum value of distortion of the oriented main axis of the drawn polyester film used in the present invention is usually 10 degrees or less, preferably 8 degrees or less, more preferably 5 degrees or less. If the maximum value of the orientation principal axis is larger than 10 degrees, the coloring deficiency tends to become large when bonded to the liquid crystal display screen. On the other hand, the "maximum value of the distortion of the orientation principal axis" of the stretched polyester film can be measured, for example, by a RETS system of a phase difference film inspection apparatus manufactured by Otsuka Denshi K.K.

The thickness of the base film 101 is preferably 20 占 퐉 to 100 占 퐉, and more preferably 30 占 퐉 to 50 占 퐉. If the thickness of the base film 101 is less than 20 탆, handling tends to be difficult. When the thickness exceeds 100 탆, the merit of thinning tends to be reduced.

&Lt; Polarizer Protective Film Manufacturing Method >

Next, a method for producing the polarizer protective film shown in Fig. 1 will be described. The polarizer protective film 100 is preferably manufactured by a method including the following steps (A) and (B).

(A) a coating process for forming a coating layer on a base film 101 by coating a coating liquid containing a light-transmitting resin in which light-transmitting fine particles 104 are dispersed, and

(B) a curing step of curing the coating layer.

The coating liquid to be used in the step (A) is a mixture of the light-transmitting fine particles 104, the light-transmissive resin 103 constituting the light-diffusing layer 102 or a resin (e.g., ionizing radiation curable resin, thermosetting resin or metal alkoxide ) And other components such as solvents if necessary. When an ultraviolet curable resin is used as the resin forming the light transmitting resin 103, the coating liquid contains a photopolymerization initiator (radical polymerization initiator). As the photopolymerization initiator, for example, an acetophenone photopolymerization initiator, a benzoin photopolymerization initiator, a benzophenone photopolymerization initiator, a thioxanthone photopolymerization initiator, a triazine photopolymerization initiator, and an oxadiazole photopolymerization initiator. Examples of the photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'- 2-chloroacridone, 2-ethyl anthraquinone, benzyl, 9,10-phenanthrenequinone, camphaquinone, methyl phenylglyoxylate, and titanocene compounds can also be used . The photopolymerization initiator is used usually in an amount of 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the resin contained in the coating liquid. On the other hand, in order to make the optical characteristics and the surface shape of the light diffusion film homogeneous, it is preferable that the dispersion of the light transmitting fine particles 104 in the coating liquid is isotropic dispersion.

The application of the coating liquid onto the base film can be performed by, for example, a gravure coating method, a micro gravure coating method, a rod coating method, a knife coating method, an air knife coating method, a kiss coating method, a die coating method and the like. In coating the coating solution, it is preferable to adjust the thickness of the coating layer so that the thickness of the light-diffusing layer 102 after curing is 10 占 퐉 or more and 20 占 퐉 or less as described 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 diffusion layer 102. Examples of the surface treatment include a corona discharge treatment, a glow discharge treatment, an acid surface treatment, an alkali surface treatment, and an ultraviolet ray irradiation treatment. Further, another layer such as a primer layer may be formed on the base film, and a coating solution may be coated on the other layer.

In order to improve the adhesion between the polarizer protective film of the present invention and the polarizer, it is preferable that the surface (the surface opposite to the light diffusion layer) of the base film 101 is made hydrophilic by various surface treatments.

In the step (B), the coating layer is cured. When an ionizing radiation curable resin, a thermosetting resin or a metal alkoxide is used as the resin forming the light transmitting resin 103, the coating layer is formed, drying (removal of solvent) is carried out if necessary, (When an ionizing radiation curable resin is used) or by heating (when a thermosetting resin or metal alkoxide is used). As the ionizing radiation, ultraviolet rays, electron beams, near-ultraviolet rays, visible rays, near-infrared rays, infrared rays, X-rays and the like can be appropriately selected depending on the type of resin contained in the coating liquid. Of these, ultraviolet rays and electron beams are preferable. Ultraviolet rays are preferable because high energy can be obtained.

As a light source of ultraviolet rays, for example, a low-pressure mercury lamp, a medium pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a carbon arc lamp, a metal halide lamp and a xenon lamp can be used. An ArF excimer laser, a KrF excimer laser, an excimer lamp, or a synchrotron radiation can also be used. Of these, ultra-high pressure mercury lamps, high-pressure mercury lamps, low-pressure mercury lamps, xenon arc lamps, and metal halide lamps are preferably used.

The electron beam may be emitted from various electron beam accelerators such as Cockcroft-Walton type, Van de Graaff type, resonance type, insulation core type, linear type, dynamictron type, Electron beam having an energy of 50 keV to 1000 keV, preferably 100 keV to 300 keV.

The T _c and H in the polarizer protective film can be adjusted within the range specified in the present invention, for example, by the following method. First, a polarizer protective film is prepared by the above-described materials and methods, and _Tc and H are measured. As a result, in the case where the value of T _c is excessively high, either the treatment of increasing the number of addition of the light-transmitting fine particles, increasing the particle diameter of the light-transmitting fine particles or increasing the thickness of the light- When the value of H is excessively high, any one of the processes of lowering the number of addition of the light-transmitting fine particles or making the shape of the light-transmitting fine particles spherical, or a combination of these treatments, And its _Tc and H are measured. The production of the polarizer protective film and the measurement of its T _c and H are repeated until the value of the target T _{c and} the value of H are obtained.

[Polarizer]

The polarizer protective film of the present invention is bonded to the surface of a polarizer to constitute a polarizer including a polarizer and a polarizer protective film. According to the polarizer protective film of the present invention, occurrence of whitening is suppressed, occurrence of rainbow stains due to transmitted light is further suppressed, and mechanical strength is also excellent, so that the occurrence of whitening is suppressed in the polarizing plate using the polarizer protective film, The occurrence of stains is further suppressed, and the polarizing plate is also excellent in mechanical strength. As the polarizer, a known polarizer can be used. The polarizer generally includes a polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorbed and oriented. The polarizer protective film of the present invention is bonded to at least one surface of the polarizer to constitute a polarizing plate. A polarizing plate disposed on the viewer side of the image display device and a polarizing plate disposed on the backside can be constituted. For example, a polarizer protective film and a polarizer may be arranged so as to be laminated in this order from the viewing side to the light diffusion layer 102, the base film 101, and the polarizer, thereby constituting a polarizing plate on the viewing side. For example, the polarizer protective film and the polarizer can be arranged so as to be stacked in this order from the viewer side to the polarizer, the base film 101, and the light diffusion layer 102, thereby forming the polarizer on the rear side. The polarizer protective film according to the present invention may be bonded to both sides of one polarizer to constitute a polarizing plate.

[Image display device]

The polarizing plate using the polarizer protective film of the present invention is used together with an image display element to constitute an image display apparatus. Here, the image display element is typically a liquid crystal panel that includes a liquid crystal cell in which liquid crystal is enclosed between upper and lower substrates, and changes an alignment state of the liquid crystal by applying a voltage to display an image. As described above, in the image display apparatus provided with the polarizer protective film of the present invention, occurrence of rainbow stains due to whitening and transmitted light on the display screen is suppressed, and mechanical strength is also excellent.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. On the other hand, the optical characteristics of the polarizer protective film and the method of measuring the weight average particle diameter of the light transmitting fine particles in the following examples are as follows.

(a) the total value of the transmitted image sharpness C _n T _c

The above-described clear image sharpness measurement test was carried out using a mismatch measuring machine (manufactured by Suga Shikenki Co., Ltd.), and the sharpness of the transmitted image C ₀ when the width of the optical comb was 0.125 mm, 0.5 mm, 1 mm, was calculated on the basis of a _{.125, C 0 .5, C 1} , C 2 in formula (3). Then, the total value T _c of C _{0 .125} , C _0.5 , C ₁ , and C ₂ was calculated.

(b) total haze value H

The total light transmittance (Tt) and the diffused (scattered) light transmitted by the polarizer protective film were measured using a haze transmittance meter according to JIS K 7136 (Hayes meter "HM-150" manufactured by Murakami Shikisai Seisakujutsu Kenshiku Co., The light transmittance Td was measured, and the total haze value H was calculated based on the formula (4).

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

Was measured using a Coulter Multisizer (manufactured by Beckman Coulter Co.) using the Coulter principle (pore electric resistance method).

&Lt; Example 1 >

Acrylic UV-curable resin 92 parts by weight (solid content: 100%, trade name: Light Acrylate DPE-6A, manufactured by Kayei Shakagaku Co., Ltd.) and 8 parts by weight of amorphous silica having an average particle diameter of 1.3 탆 (Coulter principle) (Trade name: BYK411, manufactured by Big Chemical Japan Co., Ltd.) was dispersed in an aqueous solution of bisphenol A (trade name: AZ-204, manufactured by Tosoh Silica Co., Ltd.), 0.24 parts by weight of a dispersing agent [trade name: DISPERBYK102, manufactured by Big Chemical Japan Co., Followed by mixing to obtain a dispersion (A). To 47.6 parts by weight of the dispersion of the above compound, 2.4 parts by weight of a photoinitiator (trade name: IRGACURE 184, manufactured by Ciba Specialty Chemicals), 25 parts by weight of toluene and 25 parts by weight of isobutyl alcohol were mixed by a disper and stirred, B). The coating liquid (B) was applied to a 38 占 퐉 -thick polyethylene terephthalate (PET) film (trade name: Lumirra, Toray Co., Ltd., in-plane retardation value 1000 nm) with a # 10 bar coater, And cured by ultraviolet rays to obtain a polarizer protective film.

&Lt; Comparative Example 1 &

(PETA) and trimethylol hexyl (PETA) were placed on the biaxially oriented polyethylene terephthalate (PET) film (base film) (trade name: manufactured by Lumira, Toray Co., An optical film having an antiglare layer formed of lactone (HDI) and containing no light-transmitting fine particles was used in the antiglare layer.

&Lt; Comparative Example 2 &

(PETA), triallyl isocyanurate (PETA), and triallyl isocyanate were added to an optical film of Comparative Example 2 on a biaxially oriented polyethylene terephthalate (PET) film (base film) (trade name: (Antifouling agent) and a hard coat layer formed of isophorone diisocyanate (IPDI) and having a weight average particle diameter of 6 占 퐉 (antifouling agent) in a hard coat layer, (A copolymer of styrene, ethylene glycol dimethacrylate (EDMA), and methyl methacrylate (MMA)) was used as an optical film.

&Lt; Comparative Example 3 &

(PETA) and isophorone diisocyanate on the biaxially stretched polyethylene terephthalate (PET) film (base film) (trade name: Lumirra, Toray Co., Ltd.) (Styrene, ethylene glycol dimethacrylate (EDMA), and methyl methacrylate (MMA)) having a weight average particle diameter of 6.5 占 퐉 in a hard coat layer having a hard coat layer formed of isocyanate (IPDI) Copolymer), an Al particle having a weight average particle diameter of 100 nm, and an Mg aggregate.

&Lt; Comparative Example 4 &

(PETA) and isophorone diisocyanate (PETA) on the biaxially stretched polyethylene terephthalate (PET) film (base film) (trade name: Lumirra, IPDI), and an optical film containing a light-transmitting fine particle (copolymer of styrene and ethylene glycol dimethacrylate) having a weight average particle diameter of 3 占 퐉 was used as a hard coat layer.

&Lt; Comparative Example 5 &

A hard coat layer (PETA) mainly composed of pentaerythritol tetraacrylate (PETA) was formed on the biaxially oriented polyethylene terephthalate (PET) film (base film) (trade name: And an optical film containing amorphous silica fine particles in a hard coat layer was used.

(Fabrication of liquid crystal display device)

A liquid crystal display was manufactured by using the obtained polarizer protective film of Example 1 and the optical films of Comparative Examples 1 to 4, and rainbow stains and whitening by transmitted light were evaluated according to the following methods. First, from the liquid crystal display apparatus "AQUOS (registered trademark) LC-20AX5" manufactured by Sharp Corporation, the viewer-side polarizing plate of the viewer-side polarizing plate was peeled off. Instead, the polarizing plate protective film of Example 1, Was adhered to the original polarizing plate in the coaxial direction to produce a liquid crystal display device.

(Evaluation of rainbow stains)

The obtained liquid crystal display device was displayed in white, and occurrence of rainbow stains due to transmitted light was evaluated according to the following criteria:

A: Rainbow stains are hardly visible

C: Rainbow stain clearly visible

, And evaluated with eyes. Table 1 shows the results.

(Evaluation of whiteness)

The obtained liquid crystal display device was displayed in black, and whitening on a black display in a room where a fluorescent lamp was lit was performed according to the following criteria:

A: Black is clear and white is few

C: Black is white.

, And evaluated with eyes. 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 transmitted image clarity satisfies the relationship of the formula (1) and the total haze value H satisfies the relation of the formula (2) The occurrence of rainbow stains due to the transmitted light was suppressed and the occurrence of whitening was suppressed.

(Interpretation of test results)

2 is a graph plotting the relationship between the total haze value H of the polarizer protective film of Example 1 of Table 1 and the optical films of Comparative Examples 1 to 5 and the total value T _c of transmitted image sharpness.

As shown in Fig. 2, from the plotted point of the relationship between the total haze value H of the optical film (general optical film) of Comparative Examples 1 to 5 and the total value _Tc of the transmitted image sharpness, . On the other hand, the plotting point of Example 1 was largely deviated from the straight line 200. In the relationship with the straight line 200, the plotted point of the relationship between the total haze value H and the total value T _c of the transmitted image sharpness is plotted in the peripheral region 201 of Embodiment 1, It is predicted that the occurrence of rainbow stains due to the occurrence of white spots can be suppressed and the occurrence of whitening can be suppressed, and the relationship of the formulas (1) and (2) is derived.

Claims (7)

A polarizer protective film laminated with a base film and a light diffusion layer,
Transmission image clarity total value of C _n (%) T _c and (%) satisfy the relationship of the formula (1), and to the entire haze value H (%) Formula (2) in the transmission image clarity measured test Lt; / RTI &gt;
The transmitted image sharpness measurement test is carried out by measuring an amount of transmitted light of a test piece through an optical comb having a width n (mm) perpendicular to the ray axis of transmitted light and moving at a speed of 10 mm / min,
The transmitted image sharpness C _n (%) is defined as M _n , where M _n is the maximum value of the amount of transmitted light when the transmitted portion of the optical comb is present on the optical axis in the transmitted image sharpness measurement test, When the minimum value of the amount of transmitted light when there is a shielding portion is m _n , it is calculated by the following formula (3)
The total value T _c is a total value of transmitted image sharpness C _0.125 , C _0.5 , C ₁ , and C ₂ when the width n (mm) of the optical comb is 0.125, 0.5,
0? T _c? 125 (1)
0 &amp;le; H &amp;le;
C _n = {(M _n -m _n ) / (M _n + m _n )
Wherein the light-diffusing layer comprises a light-transmitting resin and light-transmitting fine particles. The polarizer protective film according to claim 1, wherein the base film is birefringent. The polarizer protective film according to claim 2, wherein the base film has a retardation value in plane of 400 nm or more. The polarizer protective film according to claim 2, wherein the base film comprises a polyester-based resin as a main component. The polarizer protective film according to claim 2, wherein the base film has a thickness of 50 m or less. delete The polarizer protecting film according to claim 1, wherein the light transmitting fine particles comprise amorphous fine particles.

Images