KR20130130048A - Protective film for polarizing plate, method for manufacturing same, polarization plate, and liquid crystal display device - Google Patents

Abstract

When the protective film for polarizing plates is used especially as a protective film for backlight side polarizing plates of a liquid crystal display device, moire fringes can be sufficiently eliminated without causing a decrease in front luminance, and excellent image diffusibility while obtaining excellent image display. It provides a protective film for a polarizing plate having a and a manufacturing method that can be produced without process contamination by dropping the fine particles. The present invention also provides a polarizing plate and a liquid crystal display device provided with the protective film for polarizing plate. The protective film for polarizing plates of this invention is a protective film for polarizing plates which has an island-in-water structure, The main component of resin which comprises the said island is cellulose ester resin, The main component of resin which comprises the said sea is glass of resin which comprises the said island. It is a resin having a glass transition temperature lower than the transition temperature, and the arithmetic mean roughness Ra (A) of one surface A of the film is within a predetermined range, while the arithmetic mean roughness Ra (B) of the opposite surface B is within a predetermined range. It features.

Description

Protective film for polarizing plate, its manufacturing method, polarizing plate, and liquid crystal display device {PROTECTIVE FILM FOR POLARIZING PLATE, METHOD FOR MANUFACTURING SAME, POLARIZATION PLATE, AND LIQUID CRYSTAL DISPLAY DEVICE}

This invention relates to the protective film for polarizing plates, its manufacturing method, the polarizing plate with a protective film for polarizing plates, and a liquid crystal display device.

The liquid crystal display (LCD) includes a backlight unit, a liquid crystal cell, and a polarizer. The polarizing plate usually includes a protective film for a polarizing plate and a polarizer (also referred to as a 'polarizing film'). As a polarizer, the thing which dyed the polyvinyl alcohol film with iodine and extended | stretched is used frequently, The both surfaces are covered with the protective film for polarizing plates. As a protective film for polarizing plates, the cellulose triacetate (TAC) film which is excellent in moisture permeability and excellent in adhesiveness with a polarizer is used a lot.

In recent years, in the field of LCD, thickness reduction and cost reduction are progressing. Since the liquid crystal display device is not a self-luminous display device, a light source such as a cold cathode tube (CCFL) or an LED is always disposed on the back side of the liquid crystal cell (backlight type) or the edge portion (edge light type) of the light guide plate. . Since these light sources are generally line light sources or point light sources, a diffusion sheet or a diffusion film (light diffusion sheet or light diffusion film) is used in order to make a surface light source uniformly. In addition, the diffusion sheet can suppress interference fringes such as moire caused by interference between the prism sheet and incident light, which are frequently used as members for giving directivity to light, or incident light between pixels in the liquid crystal cell and incident light.

However, in recent years, in the tendency of thinning and cost reduction, reduction of the number of members of a liquid crystal display device advances, and the LCD of the structure which does not use a diffusion sheet is coming out. In addition, even in the case of using a diffusion sheet, the distance between the light source and the diffusion sheet is short for the thinning of the LCD, and therefore, it is difficult to eliminate interference fringes such as moire only with a conventional diffusion film. Therefore, what has diffusivity on the surface of a backlight side polarizing plate is used as a substitute of a diffusion sheet.

For example, Patent Literature 1 proposes a light diffusion polarizing plate having a light diffusion layer having a predetermined characteristic containing dispersion-containing porous amorphous particles and spherical particles, whereby the light diffusion sheet can be omitted. According to this method, it is possible to surely eliminate the moire fringes, but there are problems such as dropping of fine particles when polarizing plate causing process contamination, and a problem that the front luminance decreases when the display device is used.

Moreover, in patent documents 2 and 3, using the diffusing film containing translucent microparticles | fine-particles and crosslinkable microparticles | fine-particles as a protective film for polarizing plates is proposed. However, this method also had the problem of dropping fine particles during polarizing plate as described above and the inability to manufacture at low cost.

In view of this, there has been a demand for a new film that is free from fine particles and that combines light diffusivity and protective film suitability for polarizing plates sufficient to eliminate moire fringes.

In Patent Documents 4 and 5, a scattering film having a sea island structure in which a dope comprising a plurality of resins is cast on a support and is phase-separated, or a scattering film produced by applying a plurality of resin mixed solutions onto a support film Is disclosed. According to this method, the film provided with light diffusivity can be produced, and since the fine particle is not used, the problem of particle | grain dropping can also be solved. However, when it is going to use it as a protective film for polarizing plates, it turned out that there exists a new problem that a polarizer and a scattering film cannot be directly bonded by the influence of the unevenness | corrugation of a scattering film.

Moreover, in the structure of the Example of patent document 5, it turned out that moire stripe resolution ability is inadequate, and when the moire stripe resolution ability is improved by making a film thickness thick, the front brightness at the time of using a display device will fall large. In addition, a method of producing a scattering film by applying a plurality of resin mixed solutions onto a support film has a fundamental problem that it is not suitable for the market of today, where the demand for cost reduction is increasing, because the application must be performed after film formation.

Thus, fine particles can be used as a protective film for a polarizing plate without causing a decrease in frontal luminance when the display device is often a problem in a conventional scattering film, without causing a decrease in frontal luminance. It was conventionally difficult to fabricate a system that does not use a.

Japanese Patent Laid-Open No. 2000-75134 Japanese Patent Laid-Open No. 2010-277080 Japanese Patent Publication No. 2010-164931 Japanese Patent Laid-Open No. 2000-239535 Japanese Patent Laid-Open No. 2002-250806

This invention is made | formed in view of the said problem and the situation, and the subject that it solves is sufficient moire striation without causing a fall of front brightness, especially when using the protective film for polarizing plates as a protective film for backlight side polarizing plates of a liquid crystal display device. It is possible to solve the problem, to provide an excellent image display, and to provide a protective film for a polarizing plate having excellent light diffusivity. Moreover, it is providing the manufacturing method of the said protective film for polarizing plates which can be manufactured by an easy process, without the process contamination by particle | grain dropping. Moreover, it is providing the polarizing plate and liquid crystal display device with which the said protective film for polarizing plates was equipped.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, as a protective film for polarizing plates which have the island-in-water structure by different resin, the glass transition temperature of resin which comprises the said island, and resin which comprises the said sea has a specific relationship. While having arithmetic mean roughness Ra of one surface of the film and the other surface of the film having a specific range of values, the polarizing plate having excellent light diffusibility while being capable of sufficiently eliminating moire fringes without causing a decrease in front luminance. We found that the protective film for was obtained, and arrived at this invention.

That is, the above object of the present invention is solved by the following means.

(1) A protective film for a polarizing plate having an island-in-water structure comprising a continuous phase corresponding to the sea and a dispersed phase corresponding to the island, wherein a main component of the resin constituting the island is a cellulose ester resin, A main component is resin which has a glass transition temperature lower than the glass transition temperature of resin which comprises the said island, and arithmetic of the opposite surface B, while the arithmetic mean roughness Ra (A) of one surface A of a film exists in the range of 0.08-2.0 micrometers. Average roughness Ra (B) exists in the range of 0.001-0.5 micrometer, The protective film for polarizing plates characterized by the above-mentioned.

(2) The internal haze value obtained by (total haze value)-(surface haze value) exists in the range of 0.25-30%, while the total haze value of one film is in 20 to 80% of range, The protective film for polarizing plates of said (1).

(3) Average film thickness exists in the range of 20-85 micrometers, The protective film for polarizing plates as described in said (1) or (2) characterized by the above-mentioned.

(4) The protective film for polarizing plates in any one of said (1)-(3) containing at least 1 sort (s) of cellulose ester resin and resin which has glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. As a manufacturing method of the protective film for polarizing plates which dope is pliable on a support body, and forms a web, and extends after formation, the amount of residual solvent (g) contained in the said web when peeling the said web from a support body is resin in a web. It exists in the range of 5-45 mass% with respect to total amount g, The manufacturing method of the protective film for polarizing plates characterized by the above-mentioned.

(5) The protective film for polarizing plates in any one of said (1)-(3) containing at least 1 sort (s) of cellulose ester resin and resin which has glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. A method for producing a protective film for polarizing plates wherein dope is flexibly formed on a support to form a web, and the film is stretched after formation, wherein in the stretching, one surface A and the other surface B of the film are stretched at different temperatures. The manufacturing method of the protective film for polarizing plates.

(6) The polarizing plate protective film in any one of said (1)-(3) is provided.

(7) The protective film for polarizing plates in any one of said (1)-(3) is provided, The liquid crystal display device characterized by the above-mentioned.

By the said means of this invention, when using the protective film for polarizing plates especially as a protective film for backlight side polarizing plates of a liquid crystal display device, a moire fringe can fully be eliminated without causing a fall of front brightness, and excellent image display is carried out. While obtaining, the protective film for polarizing plates which have the outstanding light diffusivity can be provided. In addition, it is possible to provide a manufacturing method which can be produced in an easy process without process contamination caused by fine particle dropping. In addition, the polarizing plate and the liquid crystal display device provided with the protective film for polarizing plate can be provided.

Although it is not clear about the effect | action and mechanism of the effect of this invention, it estimates as follows.

The polarizing plate protective film of this invention makes a main component of resin which comprises an island a cellulose ester resin, and makes the main component of resin which comprises an ocean a resin which has a glass transition temperature lower than the glass transition temperature of the said cellulose ester resin, The arithmetic mean roughness of the surface A and the surface B according to the present invention can be controlled within a specific range by controlling the protruding state of the island by stretching the resin constituting the sea in a non-elliptical non-elliptical granular state. .

By increasing the arithmetic mean roughness of the surface A and controlling the arithmetic mean roughness of the surface B to be small, it is possible to directly adhere the surface B and the polarizer, while having excellent light diffusivity by the surface A, It does not cause a fall and can fully eliminate a moire fringe.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which showed typically an example of the dope manufacturing process, casting process, and drying process of a solution casting film forming method.
2A is a diagram schematically illustrating an example of a configuration of a conventional liquid crystal display device.
2B is a diagram schematically showing an example of the configuration of a conventional liquid crystal display device.
It is a figure which shows typically the example of the structure of the liquid crystal display device of this invention.
3B is a diagram schematically showing an example of the configuration of a liquid crystal display of the present invention.
4 is a diagram schematically showing a moire resolution performance evaluation method.
5 is a diagram schematically illustrating a front luminance evaluation method.
6 is a diagram schematically illustrating luminance non-uniformity evaluation points.

The protective film for polarizing plates of this invention is a protective film for polarizing plates which has the island-in-water structure which consists of a continuous phase corresponded to the sea, and the dispersed phase corresponded to an island, The main component of resin which comprises the said island is cellulose ester resin, The main component of the resin constituting the sea is a resin having a glass transition temperature lower than the glass transition temperature of the resin constituting the island, while the arithmetic mean roughness Ra (A) of one surface A of the film is in the range of 0.08 to 2.0 μm. And the arithmetic mean roughness Ra (B) of the opposite surface B is in the range of 0.001 to 0.5 µm.

This feature is a technical feature common to the inventions according to claims 1 to 7.

As an embodiment of the present invention, the internal haze obtained from (overall haze value)-(surface haze value) while the total haze value of one film is in the range of 20 to 80% from the viewpoint of the effect expression of the present invention. It is preferable that a value exists in the range of 0.25-30%. Moreover, it is preferable that average film thickness exists in the range of 20-85 micrometers.

As a manufacturing method of the protective film for polarizing plates of this invention, the said protective film for polarizing plates supports dope containing at least 1 sort (s) of cellulose ester resin and resin which has glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. As a manufacturing method of the protective film for polarizing plates which flex | flexes on and forms a web and extends after formation, the residual solvent amount (g) contained in the said web when peeling the said web from a support body is the resin total amount (g) It is preferable that it is a form within the range of 5-45 mass% with respect to).

Moreover, as a manufacturing method of the said protective film for polarizing plates, the dope containing at least 1 sort of cellulose ester resin and resin which has a glass transition temperature lower than the glass transition temperature of the said cellulose ester resin is cast | flexible on a support body, and a web is formed, As a manufacturing method of the protective film for polarizing plates which extend | stretch after formation, it is also preferable that it is a form which extends one surface A and the other surface B of a film in different temperature in the said extending | stretching.

The protective film for polarizing plates of this invention can be used suitably for a polarizing plate and a liquid crystal display device.

In addition, in this application, when the "sea island structure" mixes incompatible multiple (for example, 2 types) resin component with each other, it is a higher order structure of a mixture, and the other one in the phase in which one of the resin components is continuous is used. The structure disperse | distributed to this island shape or particle shape is mentioned. That is, the structure formed by forming one resin into the continuous phase (matrix) corresponded to the sea, and the other forming into the dispersed phase corresponded to an island.

In addition, in this application, "-" uses the numerical value described before and after that by the meaning included as a lower limit and an upper limit.

EMBODIMENT OF THE INVENTION Hereinafter, the form and aspect for implementing this invention, its component, and this invention are explained in full detail. In addition, in the following description, the surface which controlled the uneven | corrugated shape for light scattering property is defined as A surface, and the other surface is defined as B surface.

(Summary of the protective film for polarizing plates of this invention)

The protective film for polarizing plates of this invention is a protective film for polarizing plates which has the island-in-water structure which consists of a continuous phase corresponded to the sea, and the dispersed phase corresponded to an island, It is characterized by the above-mentioned. In addition, the main component of the resin constituting the island is a cellulose ester resin, the main component of the resin constituting the sea is a resin having a glass transition temperature lower than the glass transition temperature of the resin constituting the island, and one surface A of the film The arithmetic mean roughness Ra (A) of is in the range of 0.08-2.0 micrometers, The arithmetic mean roughness Ra (B) of the opposite surface B is characterized by being in the range of 0.001-0.5 micrometer.

That is, this invention is comprised including the some resin (it is also called a "polymer") containing a cellulose ester, and relates to the protective film for polarizing plates which have uneven | corrugated shape by an island structure on one surface.

Specifically, the main component of the resin constituting the island is a cellulose ester, and the resin constituting the sea is a film having a lower glass transition temperature than the resin constituting the island. Moreover, as long as it satisfies the relative relationship of the said glass transition temperature, you may contain resin other than a cellulose ester resin, for example, resin of any of the resin base materials mentioned later as a subcomponent of resin which comprises an island. Moreover, it is preferable that content of the cellulose ester which is a main component is 80 mass% or more in all resin which comprises an island.

In addition, in the protective film for polarizing plates of this invention, arithmetic mean roughness Ra based on JISB0601-2001 exists in the range of 0.08-2.0 micrometers in one surface (A) of a film, and 0.001-0.5 in the opposite surface (B). It is in the range of micrometers, It is a protective film for polarizing plates.

In the present invention, the glass transition temperature of the resin constituting the sea is lower than the glass transition temperature of the resin constituting the island, whereby the granules of the island constitute the sea as it is, rather than an ellipse. By stretching, the protruding state of the island can be controlled to control within the range of arithmetic mean roughness according to the present invention.

When the protective film for polarizing plates of this invention is used as a protective film of the backlight side polarizing plate of a liquid crystal display device, the liquid crystal display device of the outstanding image quality which does not have luminance nonuniformity in which a moire fringe was eliminated without reducing front brightness can be provided. .

<Surface Shape of Light Scattering Substrate>

As for the protective film for polarizing plates of this invention, the arithmetic mean roughness Ra based on JIS B0601-2001 has the range of 0.08-2.0 micrometers with respect to the arithmetic mean roughness Ra (A) of one surface A of a film, The arithmetic mean roughness Ra (B) is characterized by being in the range of 0.001 to 0.5 µm.

That is, the arithmetic mean roughness Ra (A) of the surface (A) exists in the range of 0.08-2.0 micrometers, and a more preferable range exists in the range of 0.15-2.0 micrometers. In addition, the arithmetic mean roughness Ra (B) of the other side (B) exists in the range of 0.001-0.5 micrometer, More preferably, it exists in the range of 0.001-0.1 micrometer.

If the value of Ra (A) is 0.08 µm or more, sufficient scattering effect can be obtained, and the moire fringes can be eliminated.

If Ra (A) is within 2.0 µm, the front luminance is not lowered when the display device is formed, which is preferable. In addition, Ra (B) should be as small as possible in the range which can be observed, and should be 0.001 micrometer or more. When Ra (B) is 0.5 micrometers or less, since adhesiveness with a polarizer is easy to take in a polarizing plate printing process, it is preferable.

Arithmetic mean roughness Ra can be measured using a measuring device according to JIS B0601-2001, for example, Olympus, manufactured by 3D Laser Microscope LEXT OLS4000, manufactured by Kosaka Genkyu Sho, Surfcoder MODEL SE-3500, etc. Can be.

The film of the present invention has an island-in-sea structure by phase separation of the resin, and has a concave-convex shape derived from the island-in-sea structure. It is preferable that this sea island structure is substantially isotropic.

In addition, isotropic means that the shape of an island part is not an elliptical system but a round shape, and there is no anisotropy in the diffusivity of the in-plane light. The shape of the island portion can be observed by the laser microscope described above.

<Haze value>

In the protective film for polarizing plates of this invention, the internal haze value calculated | required by (total haze value)-(surface haze value) is 0.25 to 30%, while the total haze value of one film is in 20 to 80% of range. It is preferable to be in a range.

If the total haze value is 20% or more, the moire fringe can be eliminated, and if it is 80% or less, it is preferable in terms of front luminance. The more preferable range of all the haze value exists in 20 to 50% of range.

It is preferable that an internal haze value exists in 0.25 to 30% of range from a viewpoint of suppression of a moire fringe and prevention of fall of front brightness. The more preferable range of an internal haze value exists in 0.5 to 20% of range.

These haze values can use the value measured according to JISK7136 using Nippon Denshoku Kogyo Co., Ltd. haze meter NDH2000 in 23 degreeC and 55% RH atmosphere.

In addition, a total haze value is a haze value of one film of this invention, and an internal haze value is the value which deducted the surface haze value from the whole haze value.

The internal haze value can use the measured value when covering both surfaces of a film with the glycerin of refractive index 1.47, sandwiching this with two glass plates, and measuring it like all the haze. By doing in this way, the influence of the haze value (namely, surface haze value) by the uneven | corrugated shape of a surface can be disregarded, and only haze value inside a film can be measured.

&Lt; Thickness &

It is preferable that the average film thickness of the protective film for polarizing plates of this invention exists in the range of 20-85 micrometers from a viewpoint of the function as a protective film for polarizing plates, the curl of a polarizing plate, etc.

More preferably, it exists in the range of 20-45 micrometers. The film thickness is measured at any ten points in the film plane with a contact film thickness meter, and the average value is taken.

<Resin base material which can be used for film of this invention>

The resin base material which comprises the film of this invention uses cellulose ester resin (henceforth "cellulose ester") for 1 type, and resin (polymer) mixed with this is styrene-type resin, (meth) acrylic-type resin, for example. , Vinyl ester resins, vinyl ether resins, halogen-containing resins, olefin resins (including alicyclic olefin resins), polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins , Polysulfone resins (polyether sulfone, polysulfone, etc.), polyphenylene ether resins (such as polymers of 2,6-xylenol), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubber or elastomer (Diene rubbers such as polybutadiene, polyisoprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylic rubber, urethane rubber, silicone rubber, etc.) It can select from combination suitably from these. Moreover, you may combine the heterogeneous cellulose ester from which the total acyl-group substitution degree and substituent differ, and you may use cellulose derivatives, such as cellulose carbamate and cellulose ether, in combination with a cellulose ester.

Examples of the cellulose esters include aliphatic organic acid esters (cellulose acetates such as cellulose diacetate and cellulose triacetate; C1-6 organic acid esters such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate); Aromatic organic acid ester (C7-12 aromatic carboxylic acid ester, such as cellulose phthalate and cellulose benzoate), etc. are mentioned. In the present invention, the cellulose ester may be composed of a main polymer constituting an island portion of an island-in-sea structure.

Styrene-based resins include styrene-based monomers or copolymers (polystyrene, styrene-α-methylstyrene copolymers, styrene-vinyltoluene copolymers, etc.), styrene-based monomers and other polymerizable monomers ((meth) acrylic monomers, anhydrous Copolymers of maleic acid, maleimide monomers, dienes, and the like. As a styrene-type copolymer, for example, a styrene-acrylonitrile copolymer (AS resin), a copolymer of styrene and a (meth) acrylic monomer [styrene-methyl methacrylate copolymer, styrene-methyl methacrylate-(meth ) Acrylic acid ester copolymer, styrene-methyl methacrylate (meth) acrylic acid copolymer, etc.], a styrene maleic anhydride copolymer, etc. are mentioned. Preferable styrene resins include polystyrene, copolymers of styrene and (meth) acrylic monomers [copolymers containing styrene and methyl methacrylate as main components] such as styrene-methyl methacrylate copolymers, AS resins, styrene-butadiene air Coalescing and the like.

As (meth) acrylic-type resin, the copolymer of a single or copolymer of a (meth) acrylic-type monomer, and a (meth) acrylic-type monomer and a copolymerizable monomer can be used. As a (meth) acrylic-type monomer, For example, (meth) acrylic acid; Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylate (Meth) acrylic acid C1-10 alkyl such as ethylhexyl; Aryl (meth) acrylates such as phenyl (meth) acrylate; Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; Glycidyl (meth) acrylate; N, N-dialkylamino alkyl (meth) acrylates; (Meth) acrylonitrile; (Meth) acrylate which has alicyclic hydrocarbon groups, such as a tricyclodecane, etc. can be illustrated. Examples of the copolymerizable monomers include styrene monomers, vinyl ester monomers, maleic anhydride, maleic acid, and fumaric acid. These monomers can be used individually or in combination of 2 or more types.

As (meth) acrylic-type resin, For example, poly (meth) acrylic acid ester, such as polymethyl methacrylate, methyl methacrylate (meth) acrylic acid copolymer, methyl methacrylate (meth) acrylic acid ester copolymer, meta Methyl acrylate- (meth) acrylic acid copolymer, (meth) acrylic acid ester-styrene copolymer (MS resin etc.) etc. are mentioned. As preferable (meth) acrylic-type resin, the poly (meth) acrylic-acid C1-6 alkyls, such as methyl poly (meth) acrylate, especially the meta which make methyl methacrylate the main component 50-100 mass%, Preferably it is about 70-100 mass% Methyl methacrylate resin is mentioned.

As the vinyl ester resin, a vinyl ester monomer alone or a copolymer (polyvinyl acetate, polypropionate, etc.), a vinyl ester monomer, a copolymerizable monomer and a copolymer (ethylene-vinyl acetate copolymer, vinyl acetate-vinyl chloride) Copolymers, vinyl acetate- (meth) acrylic acid ester copolymers, and the like) or derivatives thereof. Polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl acetal resin, etc. are contained in the derivative of vinyl ester resin.

As the vinyl ether resin, a copolymer or a copolymer of vinyl C1-10 alkyl ether, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl t-butyl ether, or a vinyl C1-10 alkyl ether with a copolymerizable monomer (Vinyl alkyl ether-maleic anhydride copolymer, etc.) are mentioned.

Examples of the halogen-containing resin include polyvinyl chloride, polyvinylidene fluoride, vinyl chloride-vinyl acetate copolymers, vinyl chloride- (meth) acrylic acid ester copolymers, vinylidene chloride- (meth) acrylic acid ester copolymers, and the like.

Examples of the olefin resins include homopolymers of olefins such as polyethylene and polypropylene, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene- (meth) acrylic acid copolymers, and ethylene- (meth) acrylic acid esters. And copolymers such as copolymers. Examples of the alicyclic olefin resins include cyclic olefins (norbornene, dicyclopentadiene, and the like) or copolymers (for example, polymers having alicyclic hydrocarbon groups such as three-dimensionally rigid tricyclodecane), and the cyclic olefins. Copolymers of olefins and copolymerizable monomers (ethylene-norbornene copolymers, propylene-norbornene copolymers, etc.) and the like can be exemplified. Alicyclic olefin resin is available as a brand name "ARTON", a brand name "ZEONEX", etc., for example.

The polycarbonate resin includes aliphatic polycarbonates such as aromatic polycarbonates based on bisphenols (such as bisphenol A), diethylene glycol bisaryl carbonate, and the like.

Aromatic polyesters (such as poly C2-4 alkylene terephthalates such as polyethylene terephthalate and polybutylene terephthalate, poly C2-4 alkylene naphthalate, etc.) using an aromatic dicarboxylic acid such as terephthalic acid in the polyester resin Copolyester containing homopolyester, C2-4 alkylene arylate units (C2-4 alkylene terephthalate and / or C2-4 alkylene naphthalate units) as main components (eg, 50 mass% or more) Etc.) can be exemplified. As the copolyester, a part of the C2-4 alkylene glycol in the structural unit of the poly C2-4 alkylene arylate is selected from polyoxy C2-4 alkylene glycol, C6-10 alkylene glycol, and alicyclic diol (cyclohexane). Dimethanol, hydrogenated bisphenol A and the like), diol having an aromatic ring (9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, bisphenol A, bisphenol A-alkylene jade having a fluorenone side chain A part of the copolyester and aromatic dicarboxylic acid substituted with a seed adduct) or the like, and an aliphatic C6-12 dicarboxylic acid such as phthalic acid, isophthalic acid, adipic acid, etc. Substituted copolyesters are included. The polyester-based resin also includes a single or copolymer of an aliphatic polyester using an aliphatic dicarboxylic acid such as polyarylate-based resin, adipic acid, or lactone such as ε-caprolactone. Preferred polyester resins are usually amorphous, such as amorphous copolyesters (e.g., C2-4 alkylene arylate copolyesters, etc.).

As polyamide resin, aliphatic polyamide, such as nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, dicarboxylic acid (for example, terephthalic acid, isophthalic acid, adipic acid, etc.). ) And polyamide obtained from diamine (for example, hexamethylenediamine, metha xylylenediamine), etc. are mentioned. The polyamide-based resin may be a single or a copolymer of lactams such as ε-caprolactam, or may be copolyamide, without being limited to homopolyamide.

In the present invention, a cellulose ester and a cellulose derivative may be combined and mixed. Examples of the cellulose esters in the cellulose derivatives include aliphatic organic acid esters (cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose propionate, C1-6 organic acid esters such as cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, etc., aromatic organic acid esters (C7-12 aromatic carboxylic acid esters such as cellulose phthalate, cellulose benzoate), inorganic esters (e.g. For example, cellulose phosphate, cellulose sulfate, etc.) etc. can be illustrated, and mixed acid esters, such as an acetic acid and nitric acid cellulose ester, may be sufficient. In the cellulose derivative, hydroxy C2-4 such as cellulose carbamates (for example, cellulose phenylcarbamet, etc.), cellulose ethers (for example, cyanoethyl cellulose; hydroxyethyl cellulose, hydroxypropyl cellulose, etc.). Alkyl cellulose, C1-6 alkyl cellulose such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose or a salt thereof, benzyl cellulose, acetylalkyl cellulose and the like).

Preferred resins include, for example, styrene resins, (meth) acrylic resins, vinyl ester resins, vinyl ether resins, halogen-containing resins, alicyclic olefin resins, polycarbonate resins, polyester resins, and poly Amide resins, cellulose derivatives, silicone resins and rubber or elastomers. Usually, while being amorphous, the resin which is soluble in an organic solvent (especially the common solvent which can melt | dissolve a some polymer) is used. In particular, resins having high film forming properties and transparency, for example, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters), and the like are preferable.

The glass transition temperature of the resin is, for example, in the range of -100 to 250 ° C, preferably in the range of -50 to 230 ° C, and more preferably in the range of 0 to 200 ° C (eg, 50 to 180 ° C). Within the range of ° C. Moreover, in this invention, it is preferable to use what whose glass transition temperature is 150 degreeC or more as a cellulose ester which can comprise an island.

Moreover, as resin which can comprise an ocean, resin with a glass transition temperature lower than the said cellulose ester can be used, The difference of the glass transition temperature of resin combined with a cellulose ester is in the range of 10-80 degreeC, Preferably It is good to exist in the range of 12-50 degreeC. By combining the polymer of this range, it becomes easy to control a haze value, surface roughness, etc. to a desired value in extending | stretching. That is, if the difference of the glass transition temperature of resin which comprises an island and resin which comprises an ocean exists in this range, haze value and surface roughness can be raised by extending | stretching conditions, and it can adjust to a desired value.

In addition, the "glass transition temperature" here is the intermediate point measured by the temperature increase rate of 20 degree-C / min using a differential scanning calorimeter (DSC-7 type | mold by Perkin Elmer), and calculated | required according to JISK7121 (1987). Glass transition temperature (Tmg).

The ratio of resin constituting the island and resin constituting the sea is, for example, island / sea = 10/90 to 50/50 (mass ratio), preferably 15/85 to 45/55 (mass ratio), more preferably Can be selected from the range of 20/80-40/60 (mass ratio).

(Plasticizer)

In the protective film for polarizing plates of this invention, it is also possible to use a plasticizer together in order to improve the fluidity | liquidity and flexibility of a composition. Phthalic acid ester type, fatty acid ester type, trimellitic acid ester type, phosphate ester type, polyester type, or epoxy type etc. are mentioned as a plasticizer.

In this, the plasticizer of polyester type and phthalic acid ester type is used preferably. The polyester plasticizer is excellent in non-migration and extraction resistance compared to phthalic ester plasticizers such as dioctyl phthalate, but the plasticizing effect and compatibility are slightly inferior.

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

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

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

The ester plasticizer may be any of ester, oligoester and polyester type, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

In addition, although the viscosity of a plasticizer has a correlation with a molecular structure and molecular weight, in the case of an adipic acid type plasticizer, the range of 200-5000 Mpa * s (25 degreeC) is good with respect to compatibility and plasticization efficiency. Moreover, you may use several polyester plasticizers together.

It is preferable to add a plasticizer in 0.5-30 mass parts with respect to 100 mass parts of films of this invention. When the addition amount of a plasticizer exceeds 30 mass parts, since the surface is sticky, it is not preferable practically.

(Ultraviolet absorber)

It is also preferable that the protective film for polarizing plates of this invention contains a ultraviolet absorber, The thing of a benzotriazole type, 2-hydroxy benzophenone type, or a salicylic acid phenyl ester type etc. is mentioned as a ultraviolet absorber used. For example, there can be mentioned 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5- , Triazole compounds such as 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy- Phenone, and 2,2'-dihydroxy-4-methoxybenzophenone.

Here, among the ultraviolet absorbers, the ultraviolet absorber having a molecular weight of 400 or more is difficult to volatilize at a high boiling point and difficult to scatter even at high temperature molding, so that weather resistance can be effectively improved by the addition of a relatively small amount.

Examples of the ultraviolet absorbent having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylene bis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] such as benzotriazole-based, bis (2,2,6,6-tetramethyl-4-piperidyl) Hindered amines, such as sebacate and bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and also 2- (3,5-di-t-butyl-4- Hydroxybenzyl) -2-n-butylmalonic acid bis (1, 2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6 And hybrid systems having a structure of a hindered phenol and a hindered amine in a molecule such as tetramethylpiperidine, and these may be used alone or in combination of two or more thereof. Among them, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole or 2,2-methylene bis [4- (1,1,3,3 -Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

(Other additives)

Moreover, in order to improve the thermal decomposition property and thermal coloring property at the time of shaping | molding process, various antioxidant can also be added to the protective film for polarizing plates of this invention. It is also possible to add an antistatic agent to impart antistatic performance to the optical film.

You may use the flame-retardant acrylic resin composition which mix | blended the phosphorus flame retardant with the protective film for polarizing plates of this invention.

Examples of the phosphorus flame retardant used herein include triaryl phosphate esters, diaryl phosphate esters, monoaryl phosphate esters, aryl phosphonic acid compounds, aryl phosphine oxide compounds, condensed aryl phosphate esters, halogenated alkyl phosphate esters and halogen-containing condensed phosphoric acid. 1 type, or 2 or more types of mixtures chosen from ester, halogen containing condensation phosphonic acid ester, halogen containing phosphite ester, etc. are mentioned.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) phosphate, Tris (tribromoneopentyl) phosphate etc. are mentioned.

<Film forming of the protective film for polarizing plates of this invention>

As a manufacturing method of the protective film for polarizing plates of this invention, the said protective film for polarizing plates supports dope containing at least 1 sort (s) of cellulose ester resin and resin which has glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. As a manufacturing method of the protective film for polarizing plates which flex | flexes on and forms a web and extends after formation, the residual solvent amount (g) contained in the said web when peeling the said web from a support body is the resin total amount (g) It is preferable that it is a form within the range of 5-45 mass% with respect to).

Moreover, as a manufacturing method of the said protective film for polarizing plates, the dope containing at least 1 sort (s) of cellulose ester resin and resin which has glass transition temperature lower than the glass transition temperature of the said cellulose ester resin is cast | flexible on a support body, and a web is formed, As a manufacturing method of the protective film for polarizing plates which extend | stretch after formation, it is also preferable that it is a form which extends one surface A and the other surface B of a film in different temperature in the said extending | stretching.

By manufacturing by the method of this invention, the arithmetic mean roughness Ra (A) of one surface (A) exists in the range of 0.08-2.0 micrometers, and the arithmetic mean roughness Ra (B) of the opposite surface (B) is 0.001-0.5 micrometer. It is in the range of, The protective film for polarizing plates can be produced.

In addition, the resin according to the present invention is characterized in that the glass transition temperature of the resin constituting the sea is lower than the glass transition temperature of the resin constituting the island. By stretching the resin constituting the sea, the protruding state of the island can be controlled to control within the range of the arithmetic mean roughness according to the present invention.

Hereinafter, although the example of the film forming method of the protective film for polarizing plates of this invention is demonstrated, this invention is not limited to this.

As a film forming method of the protective film for polarizing plates of this invention, the solution film forming by the casting method is preferable.

(Organic solvent)

The organic solvent useful for forming the dope in the case of manufacturing the protective film for polarizing plates of this invention by the solution casting method can be used, without limitation, if it melt | dissolves the several polymer and other additives to be used simultaneously.

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

It is preferable to make dope contain the linear or branched aliphatic alcohol of 1-4 carbon atoms in the range of 1-40 mass% other than the said organic solvent. When the proportion of alcohol in the dope increases, the web gels, and the peeling from the metal support becomes easy, and when the proportion of alcohol is small, there is also a role of promoting dissolution of the polymer in the non-chlorine organic solvent system.

In particular, it is preferable that it is a dope composition which melt | dissolved the sea polymer and the island polymer in the range of 15-45 mass% at least in the solvent containing methylene chloride and a C1-C4 linear or branched aliphatic alcohol. .

Examples of the straight chain or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Ethanol is preferable from the viewpoint of stability of these dope, comparatively low boiling point, and good dryness.

Hereinafter, the preferable film forming method of the protective film for polarizing plates of this invention is demonstrated.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically an example of the dope manufacturing process, the casting process, and the drying process of the preferable solution casting film forming method of this invention.

1) Dissolution Process

It is a process of forming an dope by stirring in an organic solvent which mainly uses both solvents with respect to the polymer to be used, stirring an island polymer, a sea polymer, and other additives in a stirring kiln.

For dissolving the polymer, a method performed at ordinary pressure, a method performed below the boiling point of the main solvent, a method performed by pressing above the boiling point of the main solvent, Japanese Patent Laid-Open No. 9-95544, Japanese Patent Laid-Open No. 9-95557, Alternatively, various dissolution methods such as a method performed by the same cooling dissolution method described in JP-A 9-95538 and a method performed at high pressure as described in JP-A 11-21379 can be used, but in particular, the boiling point of the main solvent. The method of pressing and performing above is preferable.

After dissolving the polymer and the additive, it is filtered through a filter medium, degassed and sent to the next step in the feed pump. Filtration is in the range of 0.5-5 micrometers of trapped particle diameters, and it is preferable to use the filter medium of 10-25 sec / 100 ml of filtered water time.

After that, the main dope is filtered by the main filter 3, and the ultraviolet absorber addition liquid is added inline from the conduit 16 to this.

In most cases, main dope may be contained within the range of 10-50 mass% of recycled raw materials. The recycled raw material is a finely pulverized optical film, which cuts off both side portions of the film generated when forming the optical film, or uses an optical film raw material specified out of scratches or the like.

Moreover, what knead | mixed and pelletized the cellulose ester and sea polymer which are island polymers beforehand can be used preferably.

2) Flexible process

The dope is fed to the pressure die 30 via a liquid feeding pump (for example, a pressure metering gear pump), and an endless metal belt 31 for transferring infinitely, for example, a stainless steel belt, a rotating metal drum, or the like. It is a process of casting dope from a pressurized die slit in the casting position on the metal support body of this.

The pressurized die which can adjust the slit shape of the die member part of die | dye and is easy to make film thickness uniform is preferable. There exist a coat hanger die, a T die, etc. in pressurization die | dye, and all are used preferably. The surface of the metal support is mirror-finished. In order to raise a film forming speed | rate, two or more press dies may be provided on a metal support body, and dope amount may be divided | segmented and layered. Or it is also preferable to obtain the film of a laminated structure by the covalent smoke method which simultaneously casts a plurality of dope.

3) Solvent evaporation process

It is a process of heating a web (doping on a flexible support, and forming a dope film | membrane called a "web") on a casting support, and evaporating a solvent.

In order to evaporate the solvent, there is a method of blowing air from the web side, and / or a method of heat transfer with liquid from the back side of the support, or a method of heat transfer from the front and back by radiant heat. Do. Moreover, the method of combining these is also used preferably.

In this invention, in order to adjust the amount of residual solvent at the time of subsequent peeling, what is necessary is just to adjust suitably the liquid temperature brought into contact with the back surface of a support body in this solvent evaporation process, the contact time with a support body, etc.

4) Peeling process

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

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

Moreover, it is preferable that the amount of residual solvent at the time of peeling of a web on a metal support at the time of peeling peels in 5 to 120 mass% by the strength of dry conditions, the length of a metal support, etc.

In the present invention, the arithmetic mean roughness Ra (A) of one side (A) of the film is within the range of 0.08 to 2.0 μm, and the arithmetic mean roughness Ra (B) of the opposite side (B) is within the range of 0.001 to 0.5 μm. As one of the manufacturing methods for following, it is preferable to make the residual solvent amount of the web in the time of peeling into the range of 5-45 mass%. More preferably, it exists in the range of 10-40 mass%. When the amount of residual solvent is in this range, the protective film for polarizing plates of this invention can be obtained.

Moreover, as another manufacturing method of this invention, even when the amount of residual solvents of a web at the time of peeling is larger than 45%, extending | stretching is performed on the conditions from which film surface temperature of A surface of film and film surface temperature of B surface differ in subsequent extending | stretching. By carrying out, the protective film for polarizing plates of this invention can be obtained. This will be described later.

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

Amount of residual solvent (mass%) = {(M-N) / N} 100

Here, M is the mass at the arbitrary time point of a web, N is the mass when M thing is dried at 110 degreeC for 3 hours.

5) drying and stretching

After peeling, a web is made using the drying apparatus 35 which alternately passes a web through rollers arrange | positioned in multiple drying apparatuses, and / or the tenter extending | stretching apparatus 34 which clips and conveys both ends of a web with a clip. To dry.

Drying means generally blow hot air on both sides of the web, but there is also a means of heating microwaves instead of the wind. Too rapid drying tends to impair the planarity of the finished film. It is preferable to perform drying by high temperature from about 8 mass% or less of residual solvent. Through and drying are performed in general within the range of 40-250 degreeC.

When using a tenter stretching apparatus, it is preferable to use the apparatus which can independently control the holding | gripping length (distance from holding start to holding end) of a film by the left and right holding means of a tenter. In the tenter process, it is also desirable to make compartments with intentionally different temperatures in order to improve planarity.

It is also desirable to form a neutral zone so that each compartment does not cause interference between different temperature compartments.

Moreover, extending | stretching operation may be divided | segmented into multistep, and it is also preferable to carry out biaxial stretching in the casting | flow_spread direction and the width direction. In addition, when biaxial stretching is performed, simultaneous biaxial stretching may be performed and you may carry out in steps.

In this case, with stage, it is also possible, for example, to perform extending | stretching different from each other, and it is also possible to apply extending | stretching of a different direction to any one of them, dividing extending | stretching of the same direction into multiple steps. That is, the following extending steps are also possible, for example.

Stretching in the flexible direction-Stretching in the width direction-Stretching in the flexible direction-Stretching in the flexible direction

Stretch in the width direction-Stretch in the width direction-Stretch in the flex direction-Stretch in the flex direction

In addition, simultaneous biaxial stretching also includes extending | stretching in one direction and reducing the tension and shrinking the other. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

The inside of the range of 30-200 degreeC is preferable, and, as for the drying temperature in the case of tenter extending | stretching, the inside of the range which is 100-200 degreeC is more preferable.

As one manufacturing method of the film for polarizing plate protections of this invention, the method of extending | stretching on conditions different from the film surface temperature of the front surface and the back surface of a film is mentioned. Specifically, in the film for polarizing plate protection of this invention, since the glass transition temperature of resin (cellulose ester) which comprises an island among resin which forms an island-in-water structure is higher than resin which comprises the sea, arithmetic mean roughness is 0.08-2.0 In order to produce the surface A which exists in the range of micrometers, it is good to extend | stretch at the temperature which the surface A becomes between the glass transition temperature of resin (cellulose ester) which comprises an island, and resin which comprises an ocean, and the opposite surface What is necessary is just to extend | stretch at the temperature where the film surface temperature of the surface (B) is higher than the glass transition temperature of resin which comprises an island, in order to make the arithmetic mean roughness of (B) into 0.001 to 0.5 micrometer. The temperature control at the time of extending | stretching can use well-known means, such as a hot air and a microwave, as long as it is a means which can temperature-control independently on the A surface side and B surface side of a film.

In a tenter process, it is preferable from a viewpoint of improving the uniformity of a film that there is little temperature distribution of the width direction of an atmosphere, and, as for the temperature distribution of the width direction in a tenter process, within ± 5 degreeC is preferable, and within ± 2 degreeC More preferably, it is most preferable within +/- 1 degreeC.

6) winding process

After the amount of residual solvent in a web becomes 2 mass% or less, it is a process of winding up by the winding machine 37 as a film, and the film with favorable dimensional stability can be obtained by making the amount of residual solvent into 0.4 mass% or less. In particular, it is preferable to wind up the amount of residual solvent within the range of 0.00-0.10 mass%.

As a winding method, what is generally used may be used, and there exist a static torque method, the positive tension method, the taper tension method, the program tension control method with constant internal stress, etc., and may use them separately.

It is preferable that it is a long film, The film of this invention shows the thing in the range of 100 m-5000 m specifically, and is a thing of the form normally provided in roll shape. Moreover, it is preferable to exist in the range of 1.3-4 m, and, as for the width | variety of a film, it is more preferable to exist in the range of 1.4-2 m.

<Polarizer>

A polarizing plate is mainly comprised by the protective film for two polarizing plates which protects the front side and the back side of a polarizer. The film of this invention is used for at least 1 piece of the protective film for polarizing plates of 2 sheets which attach a polarizer from both surfaces. Since the film of this invention has not only moire resolution but also protective film property, the manufacturing cost of a polarizing plate can be reduced. The polarizing plate of this invention can be used also as a polarizing plate of the backlight side of an image display apparatus, or as a polarizing plate of a visual recognition side. When using for a backlight unit side polarizing plate, the film of this invention is arrange | positioned so that it may become the backlight side most. When using for the polarizing plate of a visual recognition side, it arrange | positions so that the film of this invention may become outermost layer. When used for the polarizing plate of the visual recognition side, projection of external light etc. can be prevented, and it can be set as the polarizing plate which can improve contrast in the environment (light room) with external light.

<Liquid Crystal Display Device>

As an example of the structure of the conventional liquid crystal display device, in the direct type | mold, as shown to FIG. 2A, from the light source side, [light source 1a / diffuser 3a / condensing sheet 4a / prism sheet etc. / upper diffusion]. Sheet 5a / liquid crystal panel 12a (polarizer 10a / protective film (9a: retardation film or the like) / substrate 8a / liquid crystal cell 7a / protective film 11a)). This is the configuration used for large LCD. On the other hand, in the side light type structure, as shown in Fig. 2B, the light source 1a is composed of a light emitting light source 2a and a light guide plate 13a, and is mainly used for small LCDs such as monitors and mobile applications. .

The lower diffusion sheet is mainly an optical sheet having a strong light diffusing property for reducing in-plane luminance unevenness of the backlight unit 6a (BLU), and the light collecting sheet transmits diffused light in the front direction of the liquid crystal display device (normal direction of the display device plane). An optical sheet for condensing light into an optical sheet, and the upper diffusion sheet is used to reduce moire caused by a periodic structure such as a prism sheet, which is a condensing sheet, or a pixel in a liquid crystal cell, and to remove in-plane luminance unevenness that cannot be completely removed from the lower diffusion sheet. It is an optical sheet used to further reduce.

In the liquid crystal display device of the present invention, as shown in FIGS. 3A and 3B, the light diffusing property is given to the protective film for the polarizing plate of the lower polarizing plate instead of the upper diffusion sheet (film 14a), and the upper diffusion sheet and By exhibiting the same or more performance, by setting it as such a structure, moire fringes can be suppressed without reducing front brightness. Further, the protective film for polarizing plate of the present invention can be manufactured without requiring a coating step or a complicated step, and the cost reduction of the entire liquid crystal display device can be realized by using the above structure in which the upper diffusion sheet is removed.

When using the protective film for polarizing plates of this invention for a liquid crystal display device, the surface whose arithmetic mean roughness Ra (A) is 0.08 micrometers or more and 2.0 micrometers or less is arrange | positioned at the light source side, and arrange | positions so that the other surface B may become a liquid crystal cell side. do. At this time, since thinning becomes further possible by using what has an optical compensation function as a protective film for polarizing plates of the other surface, it is preferable. Moreover, you may bond and use the board | substrate of a liquid crystal cell, and a polarizing plate.

As a display method of a liquid crystal cell, a transmissive type of mode, such as twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), optically compensated bend cell (OCB), etc. , A reflection type or a transflective liquid crystal display device.

As a light emitting light source (light emitting body) used for the light source, CCFL (Cold Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), LED (Light Emitting Diode), OLED (Organic Light-Emitting Diode) , An organic light emitting diode [organic EL]), an inorganic EL, or the like can be preferably used.

[Example]

In the following Examples the present invention will be described in detail. The list of used resins is shown in Table 1.

&Lt; Example 1 >

28.4 parts by mass of polymethyl methacrylate (VB-7103, manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 300,000, glass transition temperature 105 ° C: resin H) and cellulose acetate propionate (56% acetonitrile, weight average molecular weight 190,000) 9.5 mass parts of glass transition temperature (178 degreeC: resin C) was melt | dissolved in the mixed solvent of 98.7 mass parts of methylene chlorides, and 13.5 mass parts of ethanol, and the dope was produced.This dope was cast on the stainless steel belt using the belt casting apparatus. After contacting hot water at a temperature of 35 ° C. from the back of the stainless steel belt for 1 minute on a temperature controlled stainless steel belt, 15 ° C. cold water was brought into contact with the back of the stainless steel belt for 15 seconds, and peeled off from the stainless steel belt. A part of peeled web was cut out and the amount of residual solvent at this time was computed based on the following formula, and the amount of residual solvent was 40%.

<Calculation method of residual solvent amount>

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

Amount of residual solvent (mass%) = {(M-N) / N} 100

Here, M is the mass at the arbitrary time point of a web, N is the mass when M thing is dried at 110 degreeC for 3 hours.

The solvent was evaporated at 35 degreeC on the web which peeled from the support body, and it extended | stretched by 1.1 times in the width direction, conveying using the tenter which temperature was set so that film surface temperature might be 140 degreeC for both A surface and B surface. After extending | stretching, after relaxation at 135 degreeC, drying was wound up while conveying by a large number of rollers in a 120 degreeC and 140 degreeC drying zone, and the film of Example 1 of this invention with an average film thickness of 40 micrometers was obtained. .

<Surface shape observation>

When the film produced in Example 1 was observed and analyzed using an Olympus Co., Ltd. 3D measurement laser microscope LEXT OLS4000, the film forms irregularities due to the island-in-sea structure, and the arithmetic mean roughness according to JIS B0601-2001. When Ra was determined, the arithmetic mean roughness Ra (A) of the A surface was 1.2 µm and the arithmetic mean roughness Ra (B) of the B surface was 0.09 µm.

<Haze value>

In addition, when the whole haze of one film was measured using Nippon Denshoku Co., Ltd. product NDH2000, the total haze of this film was 37%. In addition, when the internal haze of the film was measured in the state which sandwiched both surfaces of the film through the glass plate via glycerin (refractive index 1.47), the internal haze of the film of Example 1 was 13%.

<Example 2>

A film was formed in the same manner as in Example 1 except that cellulose diacetate (55% acetization degree, 150,000 weight average molecular weight, glass transition temperature 189 ° C: Resin D) was used instead of cellulose acetate propionate (resin C). Thereafter, both the A and B surfaces were stretched 1.1 times in the width direction at 140 ° C. to obtain a film of Example 2 of the present invention having an average film thickness of 41 μm. In addition, when the amount of residual solvent of the web at the time of peeling from a belt was calculated by the method similar to Example 1, the amount of residual solvent was 35%.

When the surface of the film of Example 2 was observed by the method of Example 1, the unevenness | corrugation by sea-island structure was formed, and when the arithmetic mean roughness Ra was calculated | required, the arithmetic mean roughness Ra (A) of A surface was 1.7 micrometers. And arithmetic mean roughness Ra (B) of surface B were 0.2 µm.

In addition, when the haze value measurement of Example 1 measured the whole haze and internal haze of the film of Example 2, it was 48% and 17%, respectively.

<Example 3>

17.4 parts by mass of cellulose acetate propionate (degree of acetization 59%, weight average molecular weight 200,000, glass transition temperature 145 ° C: resin E) and cellulose diacetate (degree of acetization 55%, weight average molecular weight 150,000, glass transition temperature 189 ° C) : 9.4 mass parts of resin D) was melt | dissolved in 103 mass parts of methylene chlorides, and 19.6 mass parts of ethanol, and dope was produced. This dope was cast on the stainless steel belt using the belt casting apparatus. After contacting hot water at a temperature of 35 DEG C from the rear surface of the stainless steel belt and drying it for 70 seconds on the temperature controlled stainless steel belt, 15 DEG C cold water was brought into contact with the rear surface of the stainless steel belt for 15 seconds and peeled off from the stainless steel belt. The amount of residual solvent of the web at the time of peeling was 20%. The solvent of the web which peeled at 35 degreeC was evaporated, and after extending | stretching after extending | stretching in the width direction at 180 degreeC surface temperature of both A surface and B surface using a tenter, it dried, and the average film thickness of Example 3 of this invention A film was obtained.

The film of Example 3 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.31 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.05 micrometer. In addition, the total haze was 39% and the internal haze was 0.5%.

<Example 4>

After using dope produced in Example 1, dope was made to be flexible on a stainless steel belt, 35 degreeC hot water was dripped from the back surface of a stainless steel belt, it dried, and 15 degreeC cold water was made to contact, and the amount of residual solvent was 70%. The web was peeled off. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter internal temperature was set so that it might be set to 140 degreeC of A surface, and 180 degreeC of membrane surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 4 of this invention with an average film thickness of 41 micrometers.

The film of Example 4 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.9 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.09 micrometer. In addition, the total haze was 35% and the internal haze was 13%.

<Example 5>

After using dope of Example 2, dope was pliable on the stainless steel belt, the web was peeled off in the state of 65% of residual solvent amount. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter internal temperature was set so that it might become the film surface temperature of 155 degreeC of A surface, and 195 degreeC of film surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 5 of this invention with an average film thickness of 40 micrometers.

The film of Example 5 forms an unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 1.2 micrometers, and the arithmetic mean roughness Ra (B) of B surface was 0.03 micrometer. In addition, the total haze was 44% and the internal haze was 17%.

<Example 6>

20.1 parts by mass of cellulose acetate propionate (degree of acetation 59%, weight average molecular weight 200,000, glass transition temperature 145 ° C: resin E) and cellulose diacetate (degree of aceticity 55%, 150,000 weight average molecular weight, glass transition temperature 189 ° C) : 6.7 mass parts of resin D) and 0.6 mass parts of ultraviolet absorbers (tinuvin 928, BASF Japan company) were melt | dissolved in 103 mass parts of methylene chlorides, and 19.6 mass parts of ethanol, and dope was produced. After dope was pliable on a stainless steel belt, the web was peeled off in the state of 60% of residual solvent amount. Subsequently, the solvent was evaporated at 35 degreeC, conveying, the heater in a tenter was set so that it might become the film surface temperature of 165 degreeC of A surface, and the film surface temperature of 195 degreeC of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 6 of this invention with an average film thickness of 40 micrometers.

The film of Example 6 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.20 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.03 micrometer. Moreover, all the haze was 29% and the internal haze was 0.5%.

&Lt; Example 7 >

After the dope was pliable on the stainless steel belt using the dope of Example 3, the web was peeled off in the state of 55% of residual solvent amount. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter internal temperature was set so that it might become 150 degreeC of A surface, and 195 degreeC of film surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 7 of this invention with an average film thickness of 80 micrometers.

The film of Example 7 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.8 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.02 micrometer. Moreover, all the haze was 55% and the internal haze was 0.5%.

&Lt; Example 8 >

The dope of Example 6 was used, and after peeling a dope on a stainless steel belt, the web was peeled off in the state of 60% of the residual solvent amount. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter internal temperature was set so that it might become the film surface temperature of 185 degreeC of A surface, and 195 degreeC of film surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 8 of this invention with an average film thickness of 40 micrometers.

The film of Example 8 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.09 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.02 micrometer. Moreover, all the haze was 19% and the internal haze was 0.5%.

&Lt; Example 9 >

20.2 parts by mass of cellulose acetate propionate (degree of acetization 59%, weight average molecular weight 200,000, glass transition temperature 145 ° C: resin E) and cellulose triacetate (degree of acetization 61%, weight average molecular weight 300,000, glass transition temperature 156 ° C) : 6.7 mass parts of resin F) was dissolved in 103.4 mass parts of methylene chloride, and 19.7 mass parts of ethanol, and dope was produced. After dope was pliable on a stainless steel belt, the web was peeled off in the state of 60% of residual solvent amount. Then, the solvent was evaporated at 35 degreeC, conveying, the tenter internal temperature was set so that it might become 150 degreeC of membrane surface temperature of A surface, and 160 degreeC of membrane surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 9 of this invention with an average film thickness of 40 micrometers.

The film of Example 9 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.18 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.01 micrometer. Moreover, all the haze was 21% and internal haze was 0.20%.

&Lt; Example 10 >

28.4 parts by mass of polymethyl methacrylate (VB-7103, manufactured by Mitsubishi Rayon, weight average molecular weight 300,000, glass transition temperature 105 ° C: resin H) and cellulose acetate propionate (53% acetization rate, 180,000 weight average molecular weight) Glass transition temperature 176 degreeC: 9.5 mass parts of resin G) was melt | dissolved in the mixed solvent of 98.7 mass parts of methylene chloride, and 13.5 mass parts of ethanol, and dope was produced. After dope was pliable on a stainless steel belt, the web was peeled off in the state of 70% of residual solvent amount. Subsequently, the solvent was evaporated at 35 degreeC, conveying, the tenter internal temperature was set so that it might become 130 degreeC of membrane surface temperature of A surface, and 180 degreeC of membrane surface surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 10 of this invention with an average film thickness of 41 micrometers.

The film of Example 10 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 1.1 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.4 micrometer. In addition, the total haze was 48% and the internal haze was 31%.

<Example 11>

After the dope was cast on the stainless steel belt using the dope of Example 6, the web was peeled off in the state of 35% of the residual solvent amount. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter internal temperature was set so that it might become the film surface temperature of 165 degreeC of A surface, and 195 degreeC of film surface of B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of Example 11 of this invention with an average film thickness of 42 micrometers.

The film of Example 11 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 0.25 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.005 micrometer. In addition, the total haze was 32% and the internal haze was 0.6%.

&Lt; Comparative Example 1 &

3 mass parts of cellulose triacetate (degree of acemination 55.0%, weight average molecular weight 200,000, glass transition temperature 180 degreeC; resin A), and polymethyl methacrylate (VB-7103, Mitsubishi Rayon company make, weight average molecular weight 300,000, glass) Transition temperature 105 degreeC: 3 mass parts of resin H) was melt | dissolved in 94 mass parts of acetone, and dope was produced. After this dope was flexible on a glass plate, it was left to stand for 3 minutes in 30 degreeC oven, and it peeled and dried further at 120 degreeC for 20 minutes, and obtained the film of the comparative example 1 of 40 micrometers of average film thicknesses. In addition, the amount of residual solvent in the web at the time of peeling was 55%.

When the arithmetic mean roughness was calculated | required by the method similar to Example 1, the arithmetic mean roughness Ra (A) of the A surface of the film of Comparative Example 1 was 1.1 micrometers, and the arithmetic mean roughness Ra (B) of the B surface was 1.1 micrometers. Moreover, all the haze was 55% and the internal haze was 32%.

Comparative Example 2

Cellulose triacetate (acetization degree 61.1 times, weight average molecular weight 300,000, glass transition temperature 182 degreeC: resin B) is melt | dissolved in methylene chloride / methanol (9/1, mass ratio), and the cellulose tri of polymer concentration Cs = 15 mass% 653 mass parts of acetate solutions were prepared. On the other hand, hydroxypropyl cellulose (trade name M, manufactured by Nippon Soda Co., Ltd .: Resin I) was dissolved in methylene chloride / methanol (9/1, mass ratio), and a hydroxypropyl cellulose solution 20 having a polymer concentration of CI = 10 mass%. Mass parts were prepared. After mixing these solutions and being flexible on a glass plate, it left for 3 minutes at 25 degreeC, and peeled, and further drying at 120 degreeC for 20 minutes, and obtained the film of the comparative example 2 of 44 micrometers of average film thickness. The amount of residual solvent of the web at the time of peeling was 80%.

Unevenness | corrugation was formed when the film of Comparative Example 2 was observed with the 3D laser microscope, and the arithmetic mean roughness Ra (A) of the A surface of the film was 1.2 micrometers, and the arithmetic mean roughness Ra (B) of the B surface was 1.2 micrometers. Moreover, all the haze was 70% and the internal haze was 36%.

&Lt; Comparative Example 3 &

60 mass parts of cellulose triacetate (acetization degree 61.1 times, weight average molecular weight 300,000, glass transition temperature 182 degreeC: resin B) was melt | dissolved in the mixed solvent of 900 mass parts of methylene chloride / methanol = 9/1 (mass ratio). 40 mass parts of crosslinked polymethyl methacrylate microparticles | fine-particles (PMMA, Sekisui Seiko Co., Ltd. product, MBX-2AB) were added and knead | mixed to this solution, it was flexible on a glass plate, left to stand at 25 degreeC for 3 minutes, and peeled off at 120 degreeC. The film of Comparative Example 3 having an average film thickness of 45 µm was obtained by further drying for 20 minutes. The amount of residual solvent of the web at the time of peeling was 90%.

When the film after drying was observed with the 3D laser microscope, the unevenness | corrugation was formed, and the arithmetic mean roughness Ra (A) of A surface was 1.3 micrometers, and the arithmetic mean roughness Ra (B) of B surface was 1.2 micrometers. Moreover, all the haze was 59% and internal haze was 33%.

&Lt; Comparative Example 4 &

After the dope was cast on the stainless steel belt using the dope produced in Example 1, the web was peeled off in the state of 60% of the amount of residual solvent. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, the tenter temperature was set so that it might be set to 140 degreeC when both A surface and B surface were closed, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of the comparative example 4 with an average film thickness of 42 micrometers.

The film of Example 4 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 1.0 micrometer, and the arithmetic mean roughness Ra (B) of B surface was 0.9 micrometer. In addition, the total haze was 39% and the internal haze was 14%.

&Lt; Comparative Example 5 &

20.2 parts by mass of cellulose acetate propionate (56% acetization rate, 190,000 weight average molecular weight, glass transition temperature 178 ° C: resin C) and cellulose diacetate (55% acetization degree, 150,000 weight average molecular weight, glass transition temperature 189 ° C) : 6.7 mass parts of resin D) was dissolved in 103.4 mass parts of methylene chloride, and 19.7 mass parts of ethanol, and dope was produced. After this dope was pliable on a stainless steel belt, the web was peeled off in the state of 60% of residual solvent amount. Subsequently, while conveying, the solvent was evaporated at 35 degreeC, tenter temperature was set so that it might be set to 183 degreeC on both surface A and surface B, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of the comparative example 5 of 41 micrometers of average film thickness.

The film of Comparative Example 5 slightly formed irregularities, and the arithmetic mean roughness Ra (A) of the A surface was 0.07 μm, and the arithmetic mean roughness Ra (B) of the B surface was 0.07 μm. Moreover, all the haze was 20% and the internal haze was 0.5%.

&Lt; Comparative Example 6 >

19.6 parts by mass of polymethyl methacrylate (VB-7103, manufactured by Mitsubishi Rayon, weight average molecular weight 300,000, glass transition temperature 105 ° C: resin H) and cellulose acetate propionate (53% acetization rate, 180,000 weight average molecular weight) Glass transition temperature 176 degreeC: 10.6 mass parts of resin G) was melt | dissolved in the mixed solvent of 100.6 mass parts of methylene chloride, and 19.2 mass parts of ethanol, and dope was produced. After this dope was pliable on a stainless steel belt, the web was peeled off in the state of 30% of residual solvent amount. Subsequently, the solvent was evaporated at 35 degreeC, conveying, the temperature in a tenter was set so that it might become 110 degreeC of film surface on A surface, and 180 degreeC of film surface on B surface, and it extended | stretched 1.1 times in the width direction. It dried at 140 degreeC after extending | stretching, and obtained the film of the comparative example 6 with an average film thickness of 42 micrometers.

The film of the comparative example 6 formed the unevenness | corrugation, and the arithmetic mean roughness Ra (A) of A surface was 2.5 micrometers, and the arithmetic mean roughness Ra (B) of B surface was 0.4 micrometer. Moreover, all the haze was 50% and the internal haze was 29%.

<Evaluation>

With respect to the films produced in Examples 1 to 11 and Comparative Examples 1 to 6, fine particle dropping property, moire resolution ability, front brightness, and polarizer adhesion were evaluated. Furthermore, the display apparatus in which the film of Examples 1-11 and Comparative Examples 1-6 were mounted was produced, and the brightness nonuniformity was evaluated. In description of the following evaluation methods, an "evaluation film" refers to the film produced in Examples 1-11 and Comparative Examples 1-6.

<Particle deciduousity>

The dropping property of the particle | grains was evaluated using the surface property measuring instrument (TriboStation TYPE32) by Shinto Kagaku Corporation. First, a nonwoven fabric (Bencourt, manufactured by Asahi Kasei Co., Ltd.) was installed on the friction slipper surface of the surface measuring instrument, and the evaluation film was loaded so that the A side of the film faced thereunder, and a load of 200 g was applied 10 times. It was reciprocated. Thereafter, the adhesion state of the dropped fine particles on the surface of the nonwoven fabric was observed with an optical microscope (450 times), and the fine particle dropping property of the film was evaluated based on the following criteria. (Double-circle): The fallen fine particle was not observed at all. (Circle): A trace amount of fallen fine particles was observed. X: A large amount of falling fine particles was observed.

<Moire resolution>

A commercially available notebook (Samsung Electronics R430) was disassembled, the backlight unit was taken out, and two built-in prism sheets were taken out. These two prism sheets were placed on the shakasten so as to have the same order and same positional relationship as those incorporated in the backlight unit. In this state, when viewed in the dark room, strong moire stripes were observed. As shown in FIG. 4, the evaluation film cut into the size of 10 cm x 10 cm above the prism sheet of a surface is installed so that the A side of a film may face a prism sheet, and it observes in a dark room, and moire stripes The dissolution state of was evaluated based on the following criteria. The "commercial product" used as a reference of (triangle | delta) and x is an anti-glare film arrange | positioned adjacent to a backlight among the films used as the protective film for rear side (backlit side) polarizing plates of the said notebook, and liquid-crystals the rear side polarizing plate of the said notebook. After peeling from a cell and immersing in pure water for 4 hours, what peeled and taken out a polarizer from the film was fully dried, and it used after humidifying at 23 degreeC and 55% RH.

◎: Moire disappears completely

(Circle): Moire remains a little, but is the same as a commercial item

X: Moire remains and is a level below a commercial item

<Front luminance>

The front side polarizing plate, liquid crystal cell, and rear side polarizing plate of the commercially available liquid crystal monitor (Samsung Electronics, SyncMaster743BM) were removed, and the back light unit was brought out. The backlight unit had a structure of a light guide plate / lower diffusion sheet / prism sheet / prism sheet in order from the light source side. The B surface of the evaluation film was bonded to a glass plate having a thickness of 1 mm via glycerin, and the A surface of the evaluation film was opposed to the prism sheet as shown in FIG. 5 on the prism sheet of the outermost surface of the liquid crystal monitor on which the backlight unit was exposed. It arrange | positioned for every glass plate and fixed the glass plate so that a prism sheet and a glass plate may have a 500 micrometer space | gap.

The power source of the light source of the liquid crystal monitor which fixed the glass plate with an evaluation film was turned on, and it installed so that a panel surface might become perpendicular | vertical with respect to a floor surface, and it lighted for 120 minutes in 23 degreeC and 55% RH environment. Subsequently, the front luminance of the central portion of the monitor was measured in a dark room using a Konica Minolta spectroradiometer. As an evaluation standard, the ratio of the front brightness of an evaluation film is computed with respect to the front brightness of 4UY measured by the same method using the commercially available cellulose ester film 4UY (made by Konica Minolta Opto Co., Ltd.), Evaluated.

◎: 99% or more of the front luminance of 4UY

○: less than 99% of the front luminance of 4UY

X: less than 90% of the front luminance of 4UY

<Polarizer adhesion>

According to the following processes 1-6, the polarizer and the polarizing plate were produced, and adhesiveness was evaluated.

Process 1

The 50-micrometer-thick polyvinyl alcohol film was uniaxially stretched in the film forming direction (temperature 110 degreeC, draw ratio 5 times). This was immersed for 60 seconds in the aqueous solution containing the ratio of 0.075g of iodine, 6g of potassium iodide, and 100g of water, and then immersed in the 68 degreeC aqueous solution containing the ratio of 6g of potassium iodide, 7.5g of boric acid, and 100g of water. This was washed with water and dried to obtain a polarizer. This polarizer had an absorption axis in the film forming direction.

Step 2

As a polarizing plate protective film, the produced evaluation film was immersed in 50 degreeC 4 aqueous potassium hydroxide aqueous solution for 60 second, and then water washing and drying were saponified the B surface side which joins with a polarizer.

Similarly, saponification of the commercially available cellulose ester film 4UY (made by Konica Minolta Opto Corporation) was also performed as a polarizing plate protective film on the opposite side.

Step 3

The polarizer was immersed for 1 to 2 seconds in a polyvinyl alcohol adhesive bath having a solid content of 2% by mass.

Step 4

The excess adhesive adhering to the polarizer in step 3 was lightly wiped off, and this was placed on the B surface of the evaluation film treated in step 2, and the saponified surface of a commercially available cellulose ester film 4UY treated in step 2 as a polarizing plate protective film on the opposite side. It laminated | stacked so that this polarizer might be contacted and it was set as the polarizing plate.

Step 5

The pressure of 20-30 N / cm <2> and conveyance speed were bonded by the polarizing plate which laminated | stacked the film and the polarizer at the process 4 at about 2 m / min.

Step 6

The polarizing plates bonded at the step 5 were each cut to a size of 5 cm × 7 cm, and both ends of the long side of the obtained polarizing plate piece were securely fitted with a clip, and the polarizing plate pieces were vertically suspended for each clip in an oven at 60 ° C. and dried.

5 minutes later, after taking out from an oven and fully humidifying in 23 degreeC and 55% RH environment, the adhesiveness of the film of this invention and a polarizer is performed on the following references | standards by performing the test which peels an evaluation film from a polarizer by hand from the edge part of a polarizing plate. Was evaluated.

(Double-circle): It does not peel at all even if it tries to peel by force.

(Circle): When a force is applied, it peels to within 1 mm of an edge from an edge part.

X: It can peel in the range larger than 1 mm from an edge part

The above evaluation results are shown in Table 2 and Table 3.

As apparent from the results shown in Table 2 and Table 3, since the film of the present invention does not use fine particles, there is no process contamination due to particle dropping, and the front brightness is not lowered, and the moire by the prism sheet can be effectively eliminated. Can be. Moreover, since it is excellent in adhesiveness with a polarizer, it turns out that it is excellent as a protective film for polarizing plates which have moire-resolving ability.

<Production of display device>

The rear side polarizing plate of the commercially available liquid crystal monitor (Samsung Electronics, SyncMaster743BM) was peeled off, and the polarizing plate of this invention produced according to the polarizing plate steps 1-6 described in the term of polarizer adhesive evaluation instead was bonded. However, the size to cut | disconnect in step 6 is set to 20 cm square size, and when bonding to a liquid crystal cell, an absorption axis is further aligned in the same direction as the polarizing plate previously bonded so that the surface of an evaluation film may become arrangement | positioning toward a backlight side. It bonded so that it could face, and produced the liquid crystal display devices 1-11 of this invention and the liquid crystal display devices 1-6 of a comparison corresponding to the films of Examples 1-11 and Comparative Examples 1-6, respectively.

<Luminance unevenness evaluation>

The produced liquid crystal display device was displayed white under a dark room, and as shown in Fig. 6, the measuring points of the nine points were determined by five points in the horizontal direction and the vertical direction including the center part and the center part of the display device, and the spectroradiometer manufactured by Konica Minolta Co., Ltd. The luminance of each measuring point was measured using CS-2000, and the luminance nonuniformity was evaluated based on the following criteria. The luminance nonuniformity was represented by {(maximum value-minimum value) / average value} x 100 using the average value, the maximum value, and the minimum value of the brightness | luminance of nine measuring points. In the liquid crystal monitor used, since the luminance nonuniformity of 7% was originally seen when the brightness was measured by this method in a commercially available state, the following reference | standard was set based on this value.

○: luminance unevenness is less than 7%

X: luminance nonuniformity is 7% or more

The above evaluation results are shown in Table 4 and Table 5.

As apparent from the results shown in Tables 4 and 5, in the liquid crystal display device provided with the film of the present invention, there is an effect of suppressing luminance unevenness. This is because the film of the present invention is free from defects such as lifting between the polarizer and the light diffusing ability of sufficiently moire-resolving without lowering the front luminance, which can also solve the original luminance unevenness. By extending | stretching and manufacturing the film which has a suitable condition, when not extending | stretching, it is thought that the point which the molecular orientation of resin further matches in one direction, and the uniformity of the film itself improved contributes.

When the protective film for polarizing plates of this invention is used as a protective film for backlight side polarizing plates of a liquid crystal display device, it can fully eliminate moire striation without causing a fall of front brightness, and is excellent light, while being able to obtain the outstanding image display. It has diffusivity and can be used suitably for a polarizing plate and a liquid crystal display device.

1: melting kiln
3, 6, 12, 15: filter
4, 13: storage tank
5, 14: liquid pump
8, 16: conduit
10: UV absorber input kiln
20: confluence
21: Mixer
30: die
31: metal support
32: Web
33: peeling position
34: tenter device
35: roller drying device
41: particle injection kiln
42: storage tank
43: pump
44: filter
1a: light source
2a: luminescent light source
3a: lower diffusion sheet (or diffuser plate)
4a: condensing sheet (prism sheet, lens sheet)
5a: top diffusion sheet
6a: backlight unit
7a: liquid crystal cell
8a: transparent substrate (glass, plastic)
9a: protective film (or retardation film)
10a: polarizer
11a: protective film
12a: liquid crystal panel
13a: light guide plate
14a: protective film for polarizing plates of the present invention (with diffusion ability)
1b: side A
2b: plane B
3b: evaluation film
4b: prism sheet
5b: prism sheet
6b: shakasten
1c: LCD monitor
2c: light guide plate
3c: lower diffusion sheet
4c: prism sheet
5c: evaluation film
6c: fixed plate
7c: glass plate
8c: spectroradiometer

Claims (7)

A protective film for a polarizing plate comprising a continuous phase corresponding to the sea and a dispersed phase corresponding to the island, wherein the main component of the resin constituting the island is a cellulose ester resin, and the main component of the resin constituting the sea is It is resin which has glass transition temperature lower than the glass transition temperature of resin which comprises an island, the arithmetic mean roughness Ra (A) of one surface A of a film exists in the range of 0.08-2.0 micrometers, and the arithmetic mean roughness of the opposite surface B is Ra (B) exists in the range of 0.001-0.5 micrometer, The protective film for polarizing plates characterized by the above-mentioned. The method of claim 1,
The total haze value of one film is in the range of 20 to 80%, and the internal haze value determined by (total haze value)-(surface haze value) is within the range of 0.25 to 30%. Protective film. 3. The method according to claim 1 or 2,
An average film thickness exists in the range of 20-85 micrometers, The protective film for polarizing plates characterized by the above-mentioned. The dope containing the protective film for polarizing plates of any one of Claims 1-3 containing at least 1 type of cellulose ester resin and resin which has a glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. The manufacturing method of the protective film for polarizing plates which flex | flexes on and forms a web and extends after formation, The residual solvent amount (g) contained in the said web at the time of peeling the said web from a support body is the total amount of resin (g) It exists in the range of 5-45 mass% with respect to the manufacturing method of the protective film for polarizing plates. The dope containing the protective film for polarizing plates of any one of Claims 1-3 containing at least 1 type of cellulose ester resin and resin which has a glass transition temperature lower than the glass transition temperature of the said cellulose ester resin. A method for producing a protective film for polarizing plate, which is flexible on and forms a web and is stretched after formation, wherein the surface A and the other surface B of the film are stretched at different temperatures in the stretching. Method for producing a film. The protective film for polarizing plates of any one of Claims 1-3 is equipped, The polarizing plate characterized by the above-mentioned. The protective film for polarizing plates of any one of Claims 1-3 is equipped, The liquid crystal display device characterized by the above-mentioned.

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