JP2013167910A - Liquid crystal display device and manufacturing method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which is high in front white luminance, can keep uniformity and suppress interference fringes such as moire in a screen, and is adaptable to reduction of thickness, and to provide a manufacturing method of the liquid crystal display device.SOLUTION: A liquid crystal display device comprising a backlight comprises an optical film having light scattering properties and having an image clearness value of 9.5 to 61.5% measured through an optical comb having a width of 2 mm by using an image clearness measuring device on the basis of JIS K 7105 between a light source and a liquid crystal cell.

Description

  The present invention relates to a liquid crystal display device and a method for manufacturing the liquid crystal display device.

In recent years, liquid crystal display devices (LCDs) have been widely used because they are thin, lightweight, and have low power consumption. The liquid crystal display device includes a liquid crystal cell and a polarizing plate. The polarizing plate is usually composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating protective films on both sides thereof. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. In a reflective liquid crystal display device, usually, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. A liquid crystal cell usually comprises liquid crystal molecules, two substrates for encapsulating the liquid crystal molecules, and an electrode layer for applying a voltage to the liquid crystal molecules. A liquid crystal cell performs ON-OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmissive type, a reflective type, and a transflective type. TN (Twisted Nematic), IPS (In-Plane)
Switching, OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), STN (Super)
Display modes such as Twisted Nematic) have been proposed and used.

Since an LCD is not self-luminous, a surface light source is generally required. As an aspect of the surface light source, a backlight type in which a uniform surface light source is widely used by interposing a member having a light diffusing ability such as a diffusion sheet or a prism sheet between the liquid crystal cell and the light emitting light source is widely used. A cold cathode tube (CCFL) or LED is used as the light source. In some LCDs, a light source is arranged at the edge portion of the light guide plate and is combined with a diffusion sheet, a prism sheet, or the like to form a surface light source (edge light type). Since these are generally converted from a line light source or a point light source to a surface light source as described above, a uniform surface light source is formed using a diffusion sheet. In particular, the diffusion sheet is generally disposed between the backlight and the backlight side polarizing plate. By arranging the diffusion sheet, reduction in luminance unevenness due to the light source and uniform display characteristics are achieved (Patent Document 1), and incident light interferes with the pixels in the liquid crystal cell to cause interference fringes such as moire. Can be suppressed.
However, in recent years, attempts have been made to reduce the number of members of a liquid crystal display device or to reduce the number of fluorescent lamps used as a light source in order to reduce power consumption for the purpose of reducing manufacturing costs. Further, since the LCD is made thinner, the distance between the backlight light source and the diffusion sheet becomes closer, so that it has become difficult to achieve uniform light diffusion with the conventional diffusion film. Therefore, in order to earn as much distance as possible, a material having diffusibility on the surface of the backlight side polarizing plate has been used as an alternative to the diffusion sheet.

  For example, Patent Literature 2 proposes a light diffusing polarizing plate having a light diffusing layer having a predetermined characteristic, which contains porous amorphous particles and spherical particles in a dispersed manner, and discloses that a light diffusing sheet can be omitted. ing. Patent Document 3 proposes a method for producing a light diffusion film including a step of casting a dope containing fine particles on a support. According to this method, light diffusion excellent in optical isotropy and the like is proposed. It is disclosed that films can be made.

JP 2002-323700 A JP 2000-75134 A JP 2001-172403 A

However, since the light diffusing film described in the above document has a low total light transmittance, when used in an image display device, it may contribute to a decrease in front white luminance. Moreover, since it is necessary to contain the particle | grains which are not melt | dissolved in a lot of solvent in order to ensure sufficient diffusibility, the brittleness of a film may deteriorate. On the other hand, lowering the haze (or haze), that is, increasing the total light transmittance to suppress the reduction of the front contrast can suppress the deterioration of uniformity (fluorescent lamp unevenness, etc.) and interference fringes such as moire. It may disappear.
The present invention provides a liquid crystal display device having a high front white brightness, uniform interference fringes such as moire in the screen, and capable of being reduced in thickness, and a method of manufacturing the liquid crystal display device. Let it be an issue.

  As a result of intensive studies, the present inventors have arranged an optical film having a light scattering property (also referred to as a light scattering film) that exhibits image sharpness in a specific range between a backlight of a liquid crystal display device and a liquid crystal cell. The present invention finds that it is possible to realize a liquid crystal display device capable of reducing / uniformizing luminance unevenness due to a line light source or a point light source and suppressing interference fringes such as moire, without reducing the front white luminance. It came to complete.

That is, the present inventors achieved the above object with the following configurations.
1. A liquid crystal display device having a backlight having an image definition value of 9.5% to 61.5% measured through an optical comb having a width of 2 mm using an image definition device based on JIS K 7105 A liquid crystal display device comprising an optical film having a light scattering property between a light source and a liquid crystal cell.
2. 2. The liquid crystal display device according to 1 above, wherein the liquid crystal display device has a light-scattering structure including an optical film having a haze of 0.1% to 30% between the light source and the liquid crystal cell.
3. 3. The above 1 or 2, wherein a polarizing plate is provided between the light source and the liquid crystal cell, and an optical film having a light scattering property having a haze of 0.1% to 30% is laminated on the polarizing plate. Liquid crystal display device.
4). The optical film has a light scattering layer, and the value of the center line average roughness Ra on the surface of the optical film having the light scattering layer is 0.004 μm to 0.45 μm. 4. The liquid crystal display device according to any one of 3.
5. The optical film has a scattering intensity value at an emission angle of 4 ° with respect to a light source of a scattered light profile measured by a goniophotometer with a light reception angle of 2 ° is 0.03 to 0.07. The liquid crystal display device in any one of -4.
6). 6. The liquid crystal display device as described in any one of 1 to 5 above, wherein the optical film contains crosslinked resin particles having an average particle size of more than 2.5 μm and 20 μm or less as translucent particles.
7). The optical film includes a light-transmitting substrate containing cellulose acylate and a light scattering layer, and the film thickness of the optical film is 20 μm to 200 μm. Liquid crystal display device.
8). 8. The liquid crystal display as described in any one of 4 to 7 above, which comprises a step of forming a light scattering layer by applying a composition containing translucent particles and a matrix-forming component onto a light transmissive substrate. Device manufacturing method.
9. 8. The liquid crystal display device according to any one of 1 to 7, wherein the optical film is a polarizing plate protective film.

  According to the present invention, there are provided a liquid crystal display device having a high front white brightness, uniform interference fringes such as moire in the screen, and capable of being made thin, and a method of manufacturing the liquid crystal display device. be able to.

FIG. 6 is a schematic diagram illustrating an example of a conventional liquid crystal display device ((a) is a direct type, and (b) is a sidelight type). 1 is a schematic diagram illustrating an example of a liquid crystal display device of the present invention ((a) is a direct type, and (b) is a sidelight type). FIG. It is a schematic diagram showing an example of member arrangement | positioning in the structure which has light-scattering property. It is a schematic diagram showing an example of member arrangement | positioning in the structure which has light-scattering property. (A) It is a schematic diagram which shows a multi-manifold type co-casting die, (b) It is a schematic diagram which shows a feed block type co-casting die. It is sectional drawing which shows an example of the light-scattering film in this invention. It is sectional drawing which shows an example of the light-scattering film in this invention. It is sectional drawing which shows an example of the conventional light-scattering film. It is a figure which shows the solution film forming apparatus using a casting drum. It is a figure which shows the solution casting apparatus using a casting band. It is a schematic diagram of a light-scattering profile measuring apparatus.

  Hereinafter, the present invention will be described in more detail. In the present specification, when a numerical value represents a physical property value, a characteristic value, etc., the description “(numerical value 1) to (numerical value 2)” means “(numerical value 1) or more and (numerical value 2) or less”. . In the present specification, the description “(meth) acrylate” means “at least one of acrylate and methacrylate”. The same applies to “(meth) acrylic acid”, “(meth) acryloyl” and the like.

  The liquid crystal display device of the present invention is a liquid crystal display device having a backlight, and the sharpness (image) of a transmitted image measured through an optical comb having a width of 2 mm using an image sharpness measuring device based on JIS K 7105. A light scattering property optical film (also referred to as a light scattering film) having a value of 9.5% to 61.5%) between the light source and the liquid crystal cell. .

<Configuration of liquid crystal display device>
As an example of the configuration of a conventional liquid crystal display device, in the direct type, as shown in FIG. 1A, from the light source side, [light source 1 / diffusion plate 3 / light collecting sheet 4 (prism sheet etc.) / Upper diffusion Sheet 5 / liquid crystal panel 12 (polarizing film 10 / protective film (retardation film, etc.) 9 / substrate 8 / liquid crystal cell 7 / protective film 11)], which is mainly used for a large LCD such as a television. It is. On the other hand, as shown in FIG. 1 (b), the side light type configuration is such that the light source 1 is composed of a light emitting light source 2 and a light guide plate 13, and is mainly used in small LCDs for monitors, mobile applications and the like. .
The lower diffusion sheet is an optical sheet having a strong light diffusibility for mainly reducing in-plane luminance unevenness of the backlight unit (BLU) 6, and the condensing sheet transmits the diffused light in the front direction of the liquid crystal display device (display device plane). The upper diffusion sheet is used to reduce the moire generated by the periodic structure such as the prism sheet that is the light collection sheet and the pixels in the liquid crystal cell, and the lower diffusion sheet. This optical sheet is used to further reduce in-plane luminance unevenness that cannot be removed by the sheet.
In the liquid crystal display device of the present invention, as shown in FIGS. 2A and 2B, light diffusibility is imparted to the protective film of the lower polarizing plate instead of the upper diffusion sheet (light scattering film 14). In addition, the above-mentioned performance is exhibited similarly to the upper diffusion sheet, and not only reducing moire and in-plane luminance unevenness by the above-described configuration, but also has been an adverse effect in the prior art using the upper diffusion sheet. This brings about an effect of suppressing a decrease in front luminance and front contrast. Furthermore, the cost of the entire liquid crystal display device can be reduced by removing the upper diffusion sheet.

  Specifically, in the prior art using the upper diffusion sheet, incident light is diffused to a wide angle range more than necessary, thereby relatively reducing the amount of light emitted in the front direction. In the liquid crystal display device in which the configuration of the present invention, that is, the light diffusion profile of the light diffusing protective film applied to the lower polarizing plate is optimized, the moire and luminance unevenness can be reduced without reducing the amount of light emitted in the front direction. Since necessary and sufficient diffusibility is imparted, this problem can be solved. In addition, by changing the characteristics of the backlight and the lower diffusion sheet, or by combining these members, the optimum light scattering profile of the optical film having light diffusibility used in the present invention also changes. If it is within the range, the target performance can be exhibited. Note that even if there is an optimum value in a range slightly different from the above range, it can be easily considered by those skilled in the art.

  Furthermore, in some liquid crystal display devices, there is one that uses a brightness enhancement film (for example, DBEF; manufactured by Sumitomo 3M) directly under the lower polarizing plate, and a light scattering film is disposed on the protective film of the lower polarizing plate. Although depolarization may occur and the brightness enhancement performance may be reduced, the liquid crystal display device of the present invention uses an optical film that has a large depolarization and a wide-angle scattering component, so that the reduction in brightness enhancement performance should be extremely reduced. Can do.

<Layer structure of optical film>
The optical film in the present invention has a light diffusing ability, and as a preferred embodiment, it has at least one light scattering layer on a light-transmitting substrate (also referred to as a support). In the light scattering layer, it is preferable that translucent particles are dispersed in the matrix of the layer. The light scattering layer may be a single layer, a plurality of layers, for example, 2 to 4 layers, or a structure in which a light scattering layer and a light transmissive substrate are laminated. In addition, the light scattering layer is produced by co-casting a light transmissive substrate with the same material, and the light scattering layer and the light transmissive substrate are integrated (also referred to as a light scattering substrate). (See FIGS. 6 and 7).

  In the optical film of the present invention, layers other than the light scattering layer may be coated. Examples of these layers include a hard coat layer, an antistatic layer, and an antireflection layer. For example, the hard coat layer is provided against the friction between adjacent members, and the antistatic layer is provided against static electricity generated during the assembly of the liquid crystal display device. If necessary, the light scattering layer may have functions such as a hard coat layer and an antistatic layer at the same time.

  An antireflection layer is preferably provided so that light from the light source is not reflected and becomes stray light. In the present invention, a known antireflection film can be used from the viewpoint of low reflection. For example, configurations described in JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706 and the like can be mentioned. In addition, in terms of simple production and high productivity, preferred embodiments of the present invention are an optical film having a single light scattering layer on a support, and a single light scattering layer and a single layer on a support. It is an optical film provided with antireflection properties having a low refractive index layer in this order.

<Configuration of light scattering layer>
As a preferred embodiment of the light scattering layer in the present invention, the light scattering layer comprises a binder resin and translucent particles, and has an uneven shape on at least one surface. For example, it is a layer formed by applying, drying, and curing a coating solution containing translucent particles, matrix-forming components (such as binder monomers) and an organic solvent.

  The coating liquid for forming the light scattering layer is, for example, main monomers for matrix-forming binders, which are cured by ionizing radiation, etc., and used as a raw material for the translucent polymer, translucent particles, a polymerization initiator, and further necessary Depending on the above, a polymer compound for adjusting the viscosity of the coating solution, an inorganic fine particle filler for curling reduction or refractive index adjustment, a coating aid, and the like can be included.

  The thickness of the light scattering layer is preferably 8 μm to 15 μm, more preferably 10 μm to 15 μm, still more preferably 12 μm to 15 μm, and most preferably 13 μm to 14 μm. In the case of 8 μm or more, it is preferable because the surface unevenness does not become too large when the translucent particles described below are used, and the front luminance when mounted on the LCD does not decrease. If it is 15 μm or less, the surface unevenness is not reduced, the light scattering property is sufficient, and the brittleness of the film does not deteriorate, which is preferable.

<Translucent particle of light scattering layer>
The average primary particle size of the light-transmitting particles contained in the light-scattering layer in the present invention is preferably more than 2.5 μm and 20 μm or less, and if within this range, in addition to the formation of convex portions, internal scattering was imparted. In some cases, wide-angle scattering is suppressed and forward scattering tends to occur. Furthermore, it exceeds 3.5 μm and is preferably 15 μm or less, most preferably more than 5 μm and 12 μm or less. If it exceeds 2.5 μm, convex portions are easily formed, and light is scattered at an appropriate wide angle. Moreover, you may add the further particle | grains as needed.

In the present invention, it is preferable to adjust the refractive indexes of the translucent particles and the translucent resin (matrix) in order to obtain necessary internal scattering properties.
Moreover, when using 2 or more types of particle | grains, although the refractive index difference of particle | grains may be 0, it is preferable that they are different.

  Furthermore, it is preferable that at least one kind of particles have a refractive index lower than that of the light-transmitting resin, and another at least one kind of particles has a refractive index higher than that of the light-transmitting resin. For example, the high refractive index particles preferably have a refractive index higher by 0.001 to 0.050 than that of the translucent resin, more preferably 0.015 to 0.030. The particles having a low refractive index are preferably 0.001 to 0.050 lower than that of the translucent resin, and more preferably 0.005 to 0.015 lower. Control of internal scattering is facilitated by the difference in refractive index between two or more kinds of particles.

  In the present invention, at least one of resin particles and inorganic fine particles can be used as the translucent particles.

  Specific examples of the resin particles include, for example, crosslinked polymethyl methacrylate particles, crosslinked methyl methacrylate-styrene copolymer particles, crosslinked polystyrene particles, crosslinked methyl methacrylate-methyl acrylate copolymer particles, crosslinked acrylate-styrene copolymer particles, Preferred examples include resin particles such as melamine / formaldehyde resin particles and benzoguanamine / formaldehyde resin particles. Of these, crosslinked resin particles are preferable, and crosslinked styrene particles, crosslinked polymethyl methacrylate particles, crosslinked methyl methacrylate-styrene copolymer particles, and the like are more preferable. Furthermore, the surface of these resin particles is a so-called surface-modified particle in which a compound containing a fluorine atom, a silicon atom, a carboxyl group, a hydroxyl group, an amino group, an sulfonic acid group, a phosphoric acid group or the like is chemically bonded, or a nano particle such as silica or zirconia. The particle | grains which couple | bonded the inorganic fine particle of the size to the surface are also mentioned preferably.

  Moreover, inorganic fine particles can also be used as the translucent particles. Specific examples of the inorganic fine particles include silica particles and alumina particles, and silica particles are particularly preferably used.

  In the present invention, when the refractive index of the translucent resin is made to be 1.54 or less, particularly preferably 1.53 or less, from the viewpoint of cost, the coating unevenness and interference unevenness are not noticeable. The light-sensitive particles are preferably cross-linked polymethyl methacrylate particles, cross-linked methyl methacrylate-styrene copolymer particles, and silica particles. When using crosslinked methyl methacrylate-styrene copolymer particles, the copolymerization ratio of styrene is preferably 10% or more and 90% or less.

As the particle shape, either a true sphere or an indefinite shape can be used, but a true sphere shape is preferable. The particle size distribution is preferably monodisperse particles because of the haze value, controllability of diffusibility, and uniformity of the coated surface. For example, when particles having a particle size of 33% or more than the average particle size are defined as coarse particles, the proportion of coarse particles is preferably 1% or less, more preferably 0.8% or less of the total number of particles. Yes, and more preferably 0.4% or less.
For example, when a particle having a particle size of 16% or more smaller than the average particle size is defined as a fine particle, the proportion of the fine particle is preferably 10% or less of the total number of particles, more preferably 6% or less. Yes, more preferably 4% or less. Particles having such a particle size distribution are obtained by classification after a normal synthesis reaction, and particles having a more preferable distribution can be obtained by increasing the number of classifications or increasing the degree of classification.

  The particle size distribution of the particles is measured by a Coulter counter method, and the measured distribution is converted into a particle number distribution. The average particle size is calculated from the obtained particle distribution.

The translucent fine particles in the present invention are preferably substantially spherical. The translucent fine particles may be distributed throughout the thickness direction of the light scattering layer, but are preferably unevenly distributed near the surface of the light scattering layer.
The refractive index of the translucent particles is preferably 1.40 to 1.65, more preferably 1.45 to 1.60, and most preferably 1.45 to 1.55.
The absolute value of the difference in refractive index between the translucent particles and the light transmissive substrate is preferably less than 0.09, more preferably 0.07 or less, and even more preferably 0.05 or less. preferable. If it is less than 0.09, the scattering angle at the translucent particle interface does not become too large, and the wide-angle scattering component does not increase. Moreover, if it is in this range, it is possible to obtain appropriate forward scattering optical characteristics by combining internal scattering and surface scattering.

The amount of translucent particles used is preferably 0.0008% by mass to 0.12% by mass in terms of solid content, and 0.1 g / m per unit area by adjusting the film thickness of the light scattering layer. ^{2 ~16.0g} / ^{m 2} are preferred, more ^{preferably, 0.2g / m 2 ~12.0g / m} 2, most preferably from ^{0.3g / m 2 ~8.0g / m 2} . By using the amount within this range, a desired surface shape can be obtained.

<Binder for matrix formation of light scattering layer>
The binder for forming the matrix for forming the light scattering layer is not particularly limited. However, the binder is the same material as the light-transmitting substrate, or a saturated hydrocarbon chain or a polyether chain is formed as a main chain after curing with ionizing radiation or the like. It is preferable that it is a translucent polymer which has. Moreover, it is preferable that the main binder polymer after hardening has a crosslinked structure.

  As the binder polymer having a saturated hydrocarbon chain as the main chain after curing, a polymer obtained from an ethylenically unsaturated monomer selected from the first group of compounds described below is preferred. Moreover, as a polymer which has a polyether chain as a principal chain, the polymer by the ring-opening of the epoxy-type monomer chosen from the compound of the 2nd group described below is preferable. Furthermore, a polymer of a mixture of these monomers is also preferable.

  The binder polymer having a saturated hydrocarbon chain as the main chain and having a crosslinked structure of the first group of compounds is preferably a (co) polymer of monomers having two or more ethylenically unsaturated groups. In order to obtain a polymer having a high refractive index, the monomer structure preferably contains at least one selected from an aromatic ring, a halogen atom other than fluorine, a sulfur atom, a phosphorus atom, and a nitrogen atom. .

  As a monomer having two or more ethylenically unsaturated groups used in a binder polymer for forming a light scattering layer, an ester of a polyhydric alcohol and (meth) acrylic acid {for example, ethylene glycol di (meth) Acrylate, 1,4-cyclohexanediacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) ) Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2,3-chlorohexanetetrameta Relate, polyurethane polyacrylate, polyester polyacrylate}, vinylbenzene and its derivatives (eg, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (eg, , Divinylsulfone), (meth) acrylamide (for example, methylenebisacrylamide) and the like.

Furthermore, resins having two or more ethylenically unsaturated groups, such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins And oligomers or prepolymers such as polyfunctional compounds such as polyhydric alcohols.
Two or more of these monomers may be used in combination. The monomer having two or more ethylenically unsaturated groups is preferably contained in an amount of 10 to 100% by mass based on the total amount of the binder.

  Polymerization of the monomer having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photoradical polymerization initiator or a thermal radical polymerization initiator. Accordingly, a coating solution containing a monomer having an ethylenically unsaturated group, a photo radical polymerization initiator or a thermal radical polymerization initiator, and particles, and if necessary, an inorganic filler, a coating aid, other additives, an organic solvent and the like. After the coating solution is coated on the light-transmitting substrate, it is cured by a polymerization reaction with ionizing radiation or heat to form a light scattering layer. It is also preferable to perform ionizing radiation curing and thermal curing together. Commercially available compounds can be used as the photo and thermal polymerization initiators, and they are described in “Latest UV Curing Technology” (p. 159, publisher: Kazuhiro Takahisa, publisher; Technical Information Association, 1991). Issued) and Ciba Specialty Chemicals catalog.

In the present invention, as the second group of compounds, it is preferable to use a compound having a ring-opening polymerizable group such as an epoxy compound described below in order to reduce curing shrinkage of the cured film. For example, monomers having these epoxy groups are preferably monomers having two or more epoxy groups in one molecule, and examples thereof include JP-A Nos. 2004-264563, 2004-264564, and 2005-37737. Nos., 2005-37738, 2005-140862, 2005-140862, 2005-140863, 2002-322430, and the like.
The monomer having a ring-opening polymerizable group is preferably contained in an amount of 20 to 100% by mass with respect to all binders constituting the layer for reducing curing shrinkage, more preferably 35 to 100% by mass, and more preferably 50 to 50%. More preferably, the content is 100% by mass.

Examples of photoacid generators that generate cations by the action of light for polymerizing monomers and compounds having a ring-opening polymerizable group include ionic compounds such as triarylsulfonium salts and diaryliodonium salts, and sulfonic acids. Non-ionic compounds such as nitrobenzyl ester, etc., and various known photoacids such as compounds described in the “Organic Materials for Imaging” edition published by Bungshin Publishing Co., Ltd. (1997), etc. A generator can be used. Among these, a sulfonium salt or an iodonium salt is particularly preferable, and PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , B (C ₆ F ₅ ) ₄ ^{− and the} like are preferable as a counter ion.

  The polymerization initiator is preferably used in a range of 0.1 to 15 parts by mass with respect to 100 parts by mass of the compound of the first group or the second group in the total amount of the polymerization initiator. Is more preferable.

<High molecular compound of light scattering layer>
The light scattering layer of the present invention may contain a polymer compound. By adding a polymer compound, curing shrinkage can be reduced, and the viscosity of the coating solution can be adjusted.

  The polymer compound has already formed a polymer when added to the coating solution. Examples of the polymer compound include cellulose esters (for example, cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose acetate Pionate, cellulose acetate butyrate, cellulose nitrate, ethyl cellulose, etc.), urethane acrylates, polyester acrylates, (meth) acrylic acid esters (for example, methyl methacrylate / (meth) acrylic acid methyl copolymer, methacrylic acid) Methyl / (meth) ethyl acrylate copolymer, methyl methacrylate / (meth) butyl acrylate copolymer, methyl methacrylate / styrene copolymer, methyl methacrylate / (meth) acrylic acid copolymer, polymethacryl Methyl, etc.), a resin such as polystyrene is preferably used.

  The polymer compound is preferably from 1 to 50% by mass, more preferably from 5 to 40%, based on the total binder contained in the layer containing the polymer compound, from the viewpoint of the effect on curing shrinkage and the effect of increasing the viscosity of the coating solution. It is preferable to contain in the range of mass%. Further, the molecular weight of the polymer compound is preferably from 30,000 to 400,000 in terms of mass average, more preferably from 50,000 to 300,000, and even more preferably from 50,000 to 200,000.

<Inorganic filler of light scattering layer>
In addition to the above light-transmitting particles, the light-scattering layer of the present invention can be used for refractive index adjustment, film strength adjustment, curing shrinkage reduction, and reflectance reduction when a low refractive index layer is provided. Inorganic fillers can also be used. For example, it is made of an oxide containing at least one metal element selected from titanium, zirconium, aluminum, indium, silicon, zinc, tin, and antimony, and the average primary particle diameter is generally 0.2 μm or less. It is also preferable to contain a fine high refractive index inorganic filler that is preferably 0.1 μm or less, more preferably 0.06 μm or less and 1 nm or more.

  When it is necessary to lower the refractive index of the matrix in order to adjust the difference in refractive index with the light-transmitting particles, a fine low refractive index inorganic filler such as silica fine particles or hollow silica fine particles is used as the inorganic filler. be able to. The preferred particle size is the same as that of the fine high refractive index inorganic filler.

  The surface of the inorganic filler is preferably subjected to a silane coupling treatment or a titanium coupling treatment, and a surface treatment agent having a functional group capable of reacting with a binder species on the filler surface is preferably used.

  It is preferable that the addition amount of an inorganic filler is 10-90 mass% of the total mass of a light-scattering layer, More preferably, it is 20-80 mass%, Most preferably, it is 30-75 mass%.

  In addition, since the inorganic filler has a particle size sufficiently shorter than the wavelength of light, scattering does not occur, and the dispersion in which the filler is dispersed in the binder polymer has the property of an optically uniform substance.

<Surfactant of light scattering layer>
In the light scattering layer of the present invention, in order to ensure surface uniformity such as coating unevenness, drying unevenness, and point defects, in particular, either a fluorine-based surfactant or a silicone-based surfactant, or both are used for the light scattering layer. It is preferable to contain in the coating composition. In particular, a fluorine-based surfactant is preferably used because an effect of improving surface defects such as coating unevenness, drying unevenness, and point defects of the optical film of the present invention appears with a smaller addition amount.
The purpose of adding a surfactant is to increase productivity by imparting high-speed coating suitability while improving surface uniformity. Preferable examples of the fluorine-based surfactant include compounds described in paragraph numbers 0049 to 0074 of JP2007-188070A.

  The preferable addition amount of the surfactant (particularly, the fluorine-based polymer) used in the light scattering layer of the present invention is in the range of 0.001 to 5% by mass, preferably 0.005 to 3% by mass with respect to the coating solution. %, And more preferably in the range of 0.01 to 1% by mass. When the addition amount of the surfactant is 0.001% by mass or more, the effect is sufficient, and by setting the addition amount to 5% by mass or less, the coating film is sufficiently dried and good performance as a coating film (for example, reflection) Rate, scratch resistance).

<Organic solvent of coating solution for light scattering layer>
The light scattering layer of the present invention can be formed by applying, drying and curing a coating composition containing the above-described components. An organic solvent can be added to the coating composition for forming the light scattering layer.

  As an organic solvent, for example, in an alcohol system, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, isoamyl alcohol, 1-pentanol, n-hexanol, methyl amyl alcohol In the ketone system, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone, acetone, cyclohexanone, diacetone alcohol, etc., in the ester system, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, n-butyl acetate, Isoamyl acetate, n-amyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetate, methyl lactate, ethyl lactate, ether, acetal, 1,4 dioxane, te In hydrocarbons such as lahydrofuran, 2-methylfuran, tetrahydropyran, diethyl acetal, etc., hexane, heptane, octane, isooctane, ligroin, cyclohexane, methylcyclohexane, toluene, xylene, ethylbenzene, styrene, divinylbenzene, etc., halogen hydrocarbons In, carbon tetrachloride, chloroform, methylene chloride, ethylene chloride, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, tetrachloroethylene, 1,1,1,2-tetrachloroethane In the case of polyhydric alcohols and derivatives thereof, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoacetate, diethylene glycol, Len glycol, dipropylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl acetate, butanediol, hexylene glycol, 1,5-pentanediol, glycerin monoacetate, glycerin ethers, 1,2,6-hexanetriol, fatty acids, etc. Formic acid, acetic acid, propionic acid, entangling acid, isoentangled acid, isovaleric acid, lactic acid, etc., nitrogen compounds, formamide, N, N-dimethylformamide, acetamide, acetonitrile, etc., sulfur compounds, dimethyl sulfoxide Etc.

  Among organic solvents, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, acetone, toluene, xylene, ethyl acetate, 1-pentanol and the like are particularly preferable. In addition, an alcohol or a polyhydric alcohol solvent may be appropriately mixed with the organic solvent for the purpose of controlling cohesion. These organic solvents may be used alone or in combination, and the coating composition preferably contains 20% by mass to 90% by mass, and preferably 30% by mass to 80% by mass, as the total amount of the organic solvent. More preferably, it is most preferable to contain 40 mass%-70 mass%. In order to stabilize the surface shape of the light scattering layer, it is preferable to use a solvent having a boiling point of less than 100 ° C. and a solvent having a boiling point of 100 ° C. or more in combination.

<Curing of light scattering layer>
The light scattering layer can be formed by coating a coating solution for forming a light scattering layer on a support, and then carrying out light irradiation, electron beam irradiation, heat treatment or the like to cause crosslinking or polymerization reaction. In the case of ultraviolet irradiation, ultraviolet rays emitted from light such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. can be used. Curing with ultraviolet rays is preferably carried out by nitrogen purge or the like in an atmosphere having an oxygen concentration of 4% by volume or less, more preferably 2% by volume or less, and most preferably 0.5% by volume or less.

  Below, layers other than a light-scattering layer are demonstrated.

<Low refractive index layer>
The optical film of the present invention preferably has a low refractive index layer in order to reduce the reflectance. The refractive index of the low refractive index layer is preferably 1.20 to 1.48, more preferably 1.25 to 1.46, and particularly preferably 1.30 to 1.40. The thickness of the low refractive index layer is preferably 50 nm to 200 nm, and more preferably 70 nm to 100 nm. The haze of the low refractive index layer is preferably 3% or less, more preferably 2% or less, and most preferably 1% or less.

The low refractive index layer can be obtained by curing a curable composition containing a material for forming the low refractive index layer. As a preferable curable composition for forming the low refractive index layer,
(1) A composition containing a fluorine-containing compound having a crosslinkable or polymerizable functional group,
(2) a composition comprising as a main component a hydrolysis-condensation product of a fluorine-containing organosilane material;
(3) a composition containing a monomer having two or more ethylenically unsaturated groups and inorganic fine particles having a hollow structure;
Is mentioned.

(1) Composition containing a fluorine-containing compound having a crosslinkable or polymerizable functional group As the fluorine-containing compound having a crosslinkable or polymerizable functional group, a fluorine-containing monomer and a crosslinkable or polymerizable functional group are used. The copolymer of the monomer which has can be mentioned. Specific examples of these fluoropolymers are described in JP2003-222702A, JP2003-183322A, and the like.

  As described in JP 2000-17028 A, a curing agent having a polymerizable unsaturated group may be used in combination with the above polymer. Moreover, combined use with a compound having a fluorine-containing polyfunctional polymerizable unsaturated group as described in JP-A No. 2002-145952 is also preferred. Examples of the compound having a polyfunctional polymerizable unsaturated group include the above-described monomers having two or more ethylenically unsaturated groups. Moreover, the hydrolysis-condensation product of the organolane described in Unexamined-Japanese-Patent No. 2004-170901 is also preferable, and the hydrolysis-condensation product of the organosilane containing a (meth) acryloyl group is especially preferable. These compounds are particularly preferred because they have a large combined effect for improving scratch resistance, particularly when a compound having a polymerizable unsaturated group is used in the polymer body.

  When the polymer itself does not have sufficient curability, necessary curability can be imparted by blending a crosslinkable compound. For example, when the polymer body contains a hydroxyl group, various amino compounds are preferably used as the curing agent. The amino compound used as the crosslinkable compound is, for example, a compound containing one or both of a hydroxyalkylamino group and an alkoxyalkylamino group in total, specifically, for example, a melamine compound, Examples include urea compounds, benzoguanamine compounds, glycoluril compounds, and the like. For curing these compounds, an organic acid or a salt thereof is preferably used.

(2) Composition mainly composed of hydrolyzed condensate of fluorine-containing organosilane material The composition mainly composed of hydrolyzed condensate of fluorine-containing organosilane compound also has a low refractive index and the hardness of the coating surface. Is preferable. A condensate of a tetraalkoxysilane with a hydrolyzable silanol-containing compound at one or both ends with respect to the fluorinated alkyl group is preferred. The specific composition is described in Unexamined-Japanese-Patent No. 2002-265866, 317152.

(3) A composition containing a monomer having two or more ethylenically unsaturated groups and inorganic fine particles having a hollow structure As yet another preferred embodiment, a low refractive index layer comprising low refractive index particles and a binder can be mentioned. . The low refractive index particles may be organic or inorganic, but particles having pores inside are preferable. Specific examples of the hollow particles include silica-based particles described in JP-A No. 2002-79616. The refractive index of the low refractive index particles is preferably 1.15 to 1.40, more preferably 1.20 to 1.30. Examples of the binder monomer in the composition include monomers having two or more ethylenically unsaturated groups described in the page of the light scattering layer.

  In the low refractive index layer in the invention, it is preferable to add the polymerization initiator described in the page of the light scattering layer. When a radically polymerizable compound is contained, 1 to 10 parts by mass, preferably 1 to 5 parts by mass of a polymerization initiator can be used with respect to the compound.

  In the low refractive index layer in the present invention, inorganic particles can be used in combination. In order to impart scratch resistance, it is possible to use inorganic particles having a particle size of 15% to 150%, preferably 30% to 100%, more preferably 45% to 60% of the thickness of the low refractive index layer. it can.

  In the low refractive index layer of the present invention, for the purpose of imparting properties such as antifouling property, water resistance, chemical resistance, and slipping property, a known polysiloxane-based or fluorine-based antifouling agent, slipping agent, etc. are appropriately used. Can be added.

  In the present invention, the integrated reflectance of the antireflection light scattering film provided with a low refractive index layer or the like is preferably 4.0% or less, more preferably 3.0% or less, and most preferably 1.5%. % Or less and 0.3% or more. By reducing the integrated reflectance, reflected light on the surface of the light-scattering film can be suppressed and the transmittance can be increased. Therefore, it is possible to suppress a decrease in front white brightness when mounted on an LCD.

<Light transmissive substrate>
As the light-transmitting substrate that is the support of the optical film of the present invention, a plastic film is preferably used. Examples of the polymer forming the plastic film include cellulose acylate (for example, triacetyl cellulose, diacetyl cellulose, cellulose propionate, typically TAC-TD80U, TD80UF, etc. manufactured by Fuji Film Co., Ltd.), polyamide, polycarbonate, polyester (Eg, polyethylene terephthalate, polyethylene naphthalate), polystyrene, polyolefin, norbornene resin (Arton: trade name, manufactured by JSR Corporation), amorphous polyolefin (ZEONEX: trade name, manufactured by Nippon Zeon Corporation), ( (Meth) acrylic resin (Acrypet VRL20A: trade name, manufactured by Mitsubishi Rayon Co., Ltd., ring structure-containing acrylic resin described in JP-A No. 2004-70296 and JP-A No. 2006-171464). Of these, triacetyl cellulose, polyethylene terephthalate, and polyethylene naphthalate are preferable, and triacetyl cellulose is particularly preferable.

  The optical film in the present invention is preferably disposed on the surface of the backlight-side polarizing plate of the (semi) transmissive liquid crystal display device by providing an adhesive layer on one side. Moreover, you may combine with a polarizing plate so that the optical film in this invention may serve as the protective film of a polarizing plate. In particular, when the light-transmitting substrate is triacetylcellulose, triacetylcellulose is generally used as a protective film for protecting the polarizing film of the polarizing plate. Therefore, it is costly to use the optical film in the present invention as it is for the protective film. It is preferable in terms of space saving.

When the optical film in the present invention is used as it is as a protective film for a polarizing plate, it is preferable to carry out a saponification treatment after forming an outermost layer on a light-transmitting substrate in order to sufficiently bond it. . The saponification treatment is performed by a known method, for example, by immersing the film in an alkali solution for an appropriate time. After being immersed in the alkaline solution, it is preferable to sufficiently wash with water or neutralize the alkaline component by dipping in a dilute acid so that the alkaline component does not remain in the film.
By performing the saponification treatment, at least the surface of the light-transmitting substrate on the side opposite to the side having the outermost layer is hydrophilized.

The hydrophilized surface is particularly effective for improving the adhesion with a polarizing film containing polyvinyl alcohol as a main component. In addition, the hydrophilic surface makes it difficult for dust in the air to adhere to it, making it difficult for dust to enter between the polarizing film and the optical film when bonded to the polarizing film, and is effective in preventing point defects caused by dust. It is.
The saponification treatment is preferably carried out so that the contact angle of water on the surface of the light transmissive substrate opposite to the side having the outermost layer is 40 ° or less. More preferably, it is 30 ° or less, particularly preferably 20 ° or less.

  In the present invention, the material that can be preferably used as the material for the light-transmitting substrate is cellulose acylate, and cellulose acylate is particularly preferably a C2-C22 carboxylic acid ester of cellulose. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, cycloalkylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like, each of which may further have a substituted group.

  The acyl group having 2 to 22 carbon atoms of the cellulose acylate preferably used in the present invention may be an aliphatic acyl group or an aromatic acyl group, and is not particularly limited. Examples of these preferable acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, cyclohexanecarbonyl, adamantanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, (meth) acryloyl, and cinnamoyl groups. Among these, more preferred acyl groups are acetyl, propionyl, butanoyl, pentanoyl, hexanoyl, cyclohexanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, and the like.

The cellulose acylate preferably used in the present invention preferably has a degree of substitution with a hydroxyl group of cellulose satisfying the following mathematical formulas (7) and (8).
Formula (7): 2.3 ≦ SA ′ + SB ′ ≦ 3.0
Formula (8): 0 ≦ SA ′ ≦ 3.0

  Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of hydroxyl groups esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.6 to 3.0, and particularly preferably 2.70 to 3.00. Further, the substitution degree (SA ′) of SA is more preferably 1.4 to 3.0, and particularly preferably 2.3 to 2.9. SA represents an acetyl group substituting a hydrogen atom of a hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting a hydrogen atom of a hydroxyl group of cellulose.

In the present invention, it is preferable that the acyl group substituting the hydrogen atom of the hydroxyl group of cellulose as the SB has 3 or 4 carbon atoms. It is preferable that the degree of substitution substituted by the acyl group having the number of carbon atoms satisfies the following formula (9) in addition to the formulas (7) and (8).
Formula (9): 0 ≦ SB ”≦ 1.2
Here, SB ″ represents an acyl group having 3 or 4 carbon atoms replacing a hydrogen atom of a hydroxyl group of cellulose.

The degree of substitution can be obtained by calculating the degree of binding of fatty acids bound to hydroxyl groups in cellulose. As a measuring method, it can measure based on ASTM-D817-91 and ASTM-D817-96. The state of substitution of the acyl group with the hydroxyl group is measured by ¹³ C NMR method.

  The cellulose acylate film is preferably made of a cellulose acylate in which the polymer component constituting the film substantially satisfies the above mathematical formulas (7) and (8). “Substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the total polymer components. The cellulose acylate may be used alone or in combination of two or more.

  The degree of polymerization of cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 200 to 700, more preferably 230 to 550, still more preferably 230 to 350, and particularly preferably a viscosity average degree of polymerization of 240 to 320. . The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

The number average molecular weight Mn of cellulose acylate is preferably in the range of 7 × 10 ^{4 to} 25 × 10 ⁴ , and more preferably in the range of 8 × 10 ⁴ to 15 × 10 ⁴ . The ratio of the cellulose acylate to the mass average molecular weight Mw, Mw / Mn, is preferably 1.0 to 5.0, more preferably 1.0 to 3.0. In addition, the average molecular weight and molecular weight distribution of a cellulose acylate can be measured using a high performance liquid chromatography, Mn and Mw can be calculated using this, and Mw / Mn can be calculated.

[Plasticizer]
In the present invention, a plasticizer may be used to impart flexibility to the light-transmitting substrate, improve dimensional stability, and improve moisture resistance.

  When cellulose acylate is used as the material for the light-transmitting substrate, a plasticizer having an octanol / water partition coefficient (log P value) of 10 or less is particularly preferably used. If the log P value of the compound is 10 or less, the compatibility with the cellulose acylate is good, there is no problem such as cloudiness or powder blowing of the film, and if the log P value is greater than 0, the hydrophilicity is high. Since it does not become too high, adverse effects such as deterioration of the water resistance of the cellulose acylate film are unlikely to occur. As the logP value, a more preferable range is 1 to 8, and a particularly preferable range is 2 to 7.

  The octanol / water partition coefficient (log P value) can be measured by a flask soaking method described in Japanese Industrial Standard (JIS) Z7260-107 (2000). Further, the octanol / water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, the Crippen's fragmentation method [J. Chem. Inf. Comput. Sci. 27, 21 (1987)], Viswanadhan's fragmentation method [J. Chem. Inf. Comput. Sci. 29, 163 (1989)], Broto's fragmentation method [Eur. J. et al. Med. Chem. -Chim. Theor. 19 (71) (1984)] is preferably used, and the Crippen's fragmentation method is more preferable. When the log P value of a certain compound varies depending on the measurement method or the calculation method, it is preferable to judge by the Crippen's fragmentation method.

  Preferable plasticizers include low molecular to oligomeric compounds having a molecular weight of about 190 to 5000 within the above physical properties, and for example, phosphoric acid esters, carboxylic acid esters, polyol esters and the like are used.

  Examples of phosphate esters include triphenyl phosphate (TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, diethyl hexyl phthalate and the like. Examples of the citrate ester include O-acetyl triethyl citrate, O-acetyl tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.
These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C., and the boiling point is 250 ° C. or higher.

  These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 2 to 30 parts by mass, particularly 5 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate. Moreover, it is preferable to raise a plasticizer content rate for the layer containing a translucent particle | grain in order to improve the affinity of a cellulose acylate and a translucent particle, and brittleness improvement.

[Ultraviolet absorber]
In order to improve light resistance or prevent deterioration of image display members such as polarizing plates and liquid crystal compounds of liquid crystal display devices, it is preferable to add an ultraviolet absorber (ultraviolet ray inhibitor) to the light transmissive substrate.

  As the ultraviolet absorber, an ultraviolet absorber having a wavelength of 370 nm or less is excellent from the viewpoint of preventing deterioration of the liquid crystal compound, and a visible light having a wavelength of 400 nm or more is absorbed as little as possible from the viewpoint of good image display properties. It is preferable to use it. In particular, the transmittance at a wavelength of 370 nm is desirably 20% or less, preferably 10% or less, and more preferably 5% or less. Examples of such ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and ultraviolet absorbing groups as described above. Examples thereof include, but are not limited to, polymer ultraviolet absorbing compounds. Two or more kinds of ultraviolet absorbers may be used.

  In this invention, the usage-amount of a ultraviolet absorber is 0.1-5.0 mass parts with respect to 100 mass parts of thermoplastic resins used for a transparent base material, Preferably it is 0.5-4.0 mass parts, Preferably it is 0.8-2.5 mass parts.

[Other additives]
Furthermore, the composition (dope) for forming the light-transmitting substrate has various other additives (for example, deterioration inhibitors (for example, antioxidants, peroxide decomposition agents) according to applications in each preparation step. , Radical inhibitors, metal deactivators, acid scavengers, amines, etc.), optical anisotropy control agents, release agents, antistatic agents, infrared absorbers, etc.), which may be solid It may be an oil. That is, the melting point and boiling point are not particularly limited. Furthermore, as an infrared absorber, the thing as described in Unexamined-Japanese-Patent No. 2001-194522 can be used, for example.

  These additives may be added at any time in the dope preparation step, but may be added to the final preparation step of the dope preparation step by adding an additive preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. In addition, when the light-transmitting substrate is formed from multiple layers, the types and amounts of the thermoplastic resin and additive in each layer may be different. For example, although it describes in Unexamined-Japanese-Patent No. 2001-151902 etc., these are techniques conventionally known. These details including the ultraviolet absorbers described above are the materials described in detail on pages 16 to 22 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Institute of Invention). Preferably used.

  It is preferable that the usage-amount of these additives is suitably used in the range of 0.001-20 mass% in all the compositions which comprise a transparent base material.

[Organic solvent]
Next, the organic solvent which dissolves the material forming the light transmissive substrate will be described. Examples of the organic solvent to be used include conventionally known organic solvents. For example, those having a solubility parameter in the range of 17 to 22 are preferable. Solubility parameters are described in, for example, J. Brandrup, E.I. “Polymer Handbook (4th. Edition)” such as H and the like described in VII / 671 to VII / 714. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, fat having 5 to 8 carbon atoms Group hydrocarbons, aromatic hydrocarbons having 6 to 12 carbon atoms, fluoroalcohols (for example, described in paragraph No. [0020] of JP-A-8-143709, paragraph No. [0037] of JP-A-11-60807) Compound) and the like.

The material for forming the light-transmitting substrate is preferably dissolved in an organic solvent in an amount of 10 to 30% by mass, more preferably 13 to 27% by mass, and particularly preferably 15 to 25% by mass. The methods for preparing these concentrations may be prepared so as to have a predetermined concentration at the stage of dissolution, or prepared in advance as a low concentration solution (for example, 9 to 14% by mass) and then in a concentration step described later. You may adjust to a high concentration solution. Furthermore, it is good also as a solution of the predetermined | prescribed low concentration by adding various additives later as a solution of the material which forms a high concentration light transmissive base material beforehand.
One or more organic solvents may be used.

<Preparation of dope>
Regarding the preparation of a solution (dope) of a material forming a light-transmitting substrate such as cellulose acylate, the dissolution method is not particularly limited, and a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, It can be implemented by a combination of these. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, JP JP-A Nos. 2000-273184, 11-323017, and 11-302388 describe methods for preparing cellulose acylate solutions. These methods for dissolving cellulose acylate in an organic solvent can be used as appropriate in the present invention. About these details, especially a non-chlorine type | system | group solvent system, it can implement by the method described in detail on pages 22-25 of the technical number 2001-1745. Furthermore, the cellulose acylate dope solution can be usually subjected to solution concentration and filtration. These are described in detail on page 25 of Kokai No. 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, In that case, it can be used in a pressurized state.

<Method for producing optical film>
The optical film in the present invention can be produced by applying a composition containing translucent particles and a matrix-forming component on a light transmissive substrate to form the light scattering layer. Moreover, the light-scattering base material which formed the light-transmitting base material and the light-scattering layer with the same kind of material can be manufactured as follows. <Method for producing light-scattering substrate>
The main component constituting the light transmissive substrate and the light scattering layer of the present invention (a material having a solid content of 51% by mass or more) is preferably a thermoplastic resin. Cellulose acylate (for example, triacetyl cellulose, diacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose), polyamide, polycarbonate, polyester (for example, polyethylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexanedimethylene) Terephthalate, polyethylene-1,2-diphenoxyethane-4,4′-dicarboxylate, polybutylene terephthalate), polystyrene (eg, syndiotactic polystyrene), polyolefin (eg, polypropylene, poly Ethylene, polymethylpentene, polycycloalkane), polysulfone, polyethersulfone, polyarylate, polyetherimide, polymethyl methacrylate, polyetherketone, norbornene resin (Arton: trade name, manufactured by JSR Corporation), amorphous Polyolefin (Zeonex: trade name, manufactured by Nippon Zeon Co., Ltd.), (meth) acrylic resin (Acrypet VRL20A: trade name, Mitsubishi Rayon Co., Ltd., Japanese Patent Application Laid-Open No. 2004-70296 and Japanese Patent Application Laid-Open No. 2006-171464 Ring structure-containing acrylic resin) described in the Japanese Patent Publication. Triacetyl cellulose, diacetyl cellulose, propionyl cellulose, polyethylene terephthalate and polyethylene naphthalate are particularly preferred.

  As a transparent protective film for polarizing plates, the hydrophobic / hydrophilic balance of the film, the bonding property with the vinyl alcohol film of the polarizing film and the uniformity of the optical properties in the entire film plane are important. Fatty acid ester (cellulose acylate) is preferable, and triacetyl cellulose, diacetyl cellulose, and propionyl cellulose are more preferable.

In order to produce a light-scattering substrate in which the light-transmitting substrate and the light-scattering layer of the present invention are integrated, lamination casting such as a co-casting method (simultaneous layer casting) or a sequential casting method is performed. The method can be used. In the case of manufacturing by the co-casting method and the sequential casting method, first, a plurality of dopes are prepared. The co-casting method is a casting gussa (casting die) that extrudes a plurality of dopes (three layers or more) simultaneously from another slit on a casting support (band or drum). The dope is extruded from each of the layers, and the layers are cast at the same time. After the layers are appropriately dried, they are peeled off from the casting support and dried to form a light-scattering substrate. At this time, the light-scattering base material which has a light-scattering layer is producible by using the dope which added the above-mentioned translucent particle to at least 1 layer among several dope. As the casting die, either the multi-manifold type shown in FIG. 5 (a) or the feed block type shown in FIG. 5 (b) can be used. An apparatus provided with a decompression chamber in the dope protrusion is preferable.
9 and 10 are diagrams showing an example of a solution film forming apparatus that performs casting. FIG. 9 shows an example in which a casting drum is used for the support, and in particular, by cooling the drum, the dope can be cooled to gel or contacted with the gel while it is in contact with the support. It can be peeled off at the right time, resulting in high productivity. FIG. 10 shows an example in which an endless belt is used as a support. This is a method in which the solvent is dried after the solvent is dried to a certain concentration while the dope is in contact with the belt.

  In the sequential casting method, a first casting dope is first extruded from a casting gear on a casting support, and then dried or dried without being dried or dried. The dope is extruded from a casting gieser and casted. Thereafter, the third and subsequent dopes are successively cast and laminated, peeled off from the casting support at an appropriate time, and dried to form a light scattering base. This is a casting method for forming a material. Moreover, you may extend | stretch a light-scattering base material to a fixed direction between drying and application | coating. For example, it is preferable to stretch about 0.9 to 1.5 times in the machine direction and / or the transverse direction.

  Moreover, a light-scattering base material can also be produced by a melt extrusion film forming method. That is, the above thermoplastic resin and translucent particles are mixed and dissolved, melt-extruded, and stretched to produce a light-scattering substrate. In the present invention, it is preferable to perform biaxial stretching such that the stretching ratio in a certain direction is 1.0 to 2.0 times, and the stretching ratio in the direction perpendicular thereto is 1.5 to 7.0 times. The draw ratio in the direction is 1.1 to 1.8 times, and the draw ratio in the transverse direction is 3.0 to 5.0 times. By setting the draw ratio within this range, it is possible to easily make a shape in which the translucent particles protrude on the surface of the light-scattering substrate.

  As described above, any of the co-casting method, the sequential casting method, and the melt extrusion film-forming method may be used to manufacture the light-scattering substrate. However, in general, the sequential casting method is complicated and large, and it is difficult to maintain the flatness of the light-scattering substrate. However, the co-casting method is simple and the productivity is low. Since it is high, it is preferable to manufacture by a co-casting method. In melt film formation, raw materials are dissolved without using a solvent to form a film, so that depending on the substrate, a foreign matter failure due to partial dissolution may occur.

  Furthermore, in the co-casting method, it is preferable that the dope containing the light-transmitting particles forms the outermost layer of the light-scattering substrate. Specifically, at the time of casting, the dope is preferably placed on the casting support surface or the air interface side, and more preferably placed on the air interface side from the viewpoint of peelability. Further, the temperature of the casting support is preferably 20 ° C. or less so as not to be leveled at the beginning of casting, and further the temperature of the casting support is set to 0 ° C. or less so as to cool and gel after casting. It is also preferable.

  In the light-scattering substrate, it is preferable that regions having different amounts of translucent particles are formed in the depth direction of the light-scattering substrate. The region having a large amount of the translucent particles is preferably present on the A surface side when the surface near the light scattering region of the light scattering substrate or the surface on which the unevenness is formed is defined as the A surface. It is preferable to exist in a region having a depth of up to 90% in the thickness direction depth of the light-scattering substrate from the surface, more preferably a depth of up to 75% from the A-side surface, most preferably the A-plane. It is preferably present at a depth of up to 50% from the side surface. Moreover, a particle | grain can also be contained in the area | region of the depth to 25% from the A surface side surface. An appropriate surface shape can be given by making translucent particles exist in these ranges. To segregate translucent particles in a specific depth direction, multiple dopes with different particle contents can be cast simultaneously or sequentially, or multiple dissolved resins with different particle contents can be coextruded to produce light. It is possible to form a scattering base material. Furthermore, as long as peeling does not occur, the kind of the thermoplastic resin may be different in each layer. For example, a cellulose acylate substituent or a dope having a different substitution amount may be laminated.

  The film thickness of the light-transmitting substrate is preferably 20 μm to 200 μm, more preferably 20 μm to 100 μm, more preferably 20 μm to 80 μm, and most preferably 25 μm to 25 μm, regardless of whether the substrate has light scattering properties. 50 μm. In the case of forming a light-scattering substrate using a plurality of dopes by co-casting, the surface layer dope (total thickness if present on both sides) and the base layer dope thickness ratio {(surface dope thickness / base layer dope thickness) ) × 100} is preferably 0.25% to 50%, and more preferably 0.6% to 40%. When the thickness ratio is 0.25% or more, it is easy to form a uniform layer. Further, when the thickness ratio is 50% or less, the interface of the dope is stabilized and the surface shape is rarely damaged. Here, the thickness of the dope refers to the thickness after the solvent is volatilized. In addition, the terms surface layer dope and base layer dope represent a state in which a thermoplastic resin is dissolved in a solvent and forms a surface layer and a base layer adjacent to each other through a casting die, and the solvent has evaporated. It does not necessarily indicate that an interface is present in the light-scattering substrate later. For this reason, in FIG. 6, FIG. 7, it represented with the broken line as a boundary part of each dope.

<Other coating methods>
The optical film of the present invention can be formed by the following method other than the above-described method by co-casting or sequential coating, but is not limited to this method. First, a composition (coating liquid) containing components for forming each layer is prepared. Next, a coating solution for forming various functional layers is applied onto the light-transmitting substrate by dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, or die coating. It is applied, heated and dried, but a micro gravure coating method, a wire bar coating method, and a die coating method (see US Pat. No. 2,681,294 and JP-A-2006-122889) are more preferable, and a die coating method is particularly preferable. The film can be continuously produced by feeding out a long roll of a film to be a light-transmitting substrate, and sequentially performing coating, drying, and curing as necessary. Furthermore, it can also produce more efficiently by performing the process after application | coating subsequent to support body film forming. When the light-transmitting substrate is produced by the solution casting method, the coating step can be performed simultaneously with the casting step. For example, a support casting die and a light scattering layer coating die are combined. A die can also be used.

  Thereafter, the monomer for forming the functional layer is polymerized and cured by light irradiation or heating. Thereby, a functional layer is formed. If necessary, the functional layer can be a plurality of layers.

  Next, a coating solution for forming a low refractive index layer is applied onto the functional layer in the same manner, and is irradiated with light or heated (irradiated with ionizing radiation such as ultraviolet rays, preferably irradiated with ionizing radiation under heating. Cured) to form a low refractive index layer. In this way, the optical film of the present invention is obtained.

  In the light-scattering film of the present invention, the image definition measured through an optical comb having a width of 2 mm using an image definition measuring device based on JIS K 7105 is 9.5% to 61.5%, preferably Is 10% to 60%, more preferably 25% to 60%, still more preferably 30% to 55%, and particularly preferably 35% to 50%. The image definition can be controlled by characteristics such as the material and configuration of the light scattering region and the surface shape. In the present invention, the image sharpness can be interpreted as a scale representing the degree of image blur in the light scattering film. For example, the image sharpness is caused by the period of each of the prism sheet and the liquid crystal cell pixels used on the backlight side of the liquid crystal display device. This correlates with the appearance of the moiré that occurs. As a result of the inventors investigating various liquid crystal display devices, the image sharpness when the comb width is 2 mm correlates well with the intensity of moire. If the image definition with a comb width of 2 mm is larger than 61.5%, the moire suppressing effect is weak, and if it is smaller than 9.5%, the moire becomes invisible, but the front luminance during white display decreases. Controlling the image definition within the above range can be achieved, for example, by adjusting the haze and surface shape of the film. By reducing the ratio of the flat part of the film surface and creating a gentle slope (2 to 12 °), the sharpness can be lowered even if the haze due to internal scattering is small. This can be achieved by controlling the particle diameter, particle concentration, film thickness of the light scattering layer, etc. of the translucent particles in order to produce an appropriate surface shape so that the image definition is included in the above range.

In the light scattering film of the present invention, the value of the center line average roughness Ra on the surface on the light scattering layer side is preferably 0.004 μm to 0.45 μm, more preferably 0.01 μm to 0.40 μm, and More preferably, the thickness is from 05 μm to 0.35 μm. The average interval Sm between the irregularities is preferably 30 μm or more and 350 μm or less, more preferably 50 μm or more and 200 μm or less, or 250 μm or more and 350 μm or less, and most preferably 60 μm or more and 150 μm or less or 300 μm or more and 350 μm or less.
In the light scattering film of the present invention, the haze value is preferably from 0.1% to 30%, more preferably from 10% to 30%, and further preferably from 15% to 30%.
By setting the surface roughness and the haze value in the above ranges, in addition to suppressing moire and maintaining front white luminance, stray light inside the liquid crystal cell during black display can be reduced, and a decrease in front contrast can be prevented. . This effect is considered to be because unnecessary scattered light to the wide angle side can be suppressed among the scattered light by the light scattering film.

In order to suppress moiré and in-plane luminance unevenness, the light scattering film preferably has a large light scattering intensity ratio toward the low angle side (strong forward scattering), and is a straight line incident from the film normal. A film having a relatively large intensity of scattered light with respect to light in the vicinity of 2 ° to 6 ° as compared with scattered light at other angles is preferable. Specifically, the value of the scattered light intensity at an output angle of 4 ° with respect to the light source of the scattering profile measured with a photogoniometer with a light receiving angle of 2 ° with respect to the linear light incident from the normal direction of the film is 0.03 to 0. 0.07 is preferable. Moreover, in order to achieve both the maintenance of front white luminance and front contrast and the suppression of moire and in-plane luminance unevenness, 0.03 to 0.05 is preferable, and 0.035 to 0.00 is more preferable. A light scattering film of 045 is preferred.
On the other hand, as shown in FIGS. 8 (a) and 8 (b), the conventional light scattering film is formed by coating the outermost layer with a cured layer obtained by curing a curable resin or the like to change the surface shape. However, it is common to use a low-viscosity coating solution that is easy to level, and although the Ra value can be adjusted in the height direction, the frequency of each low-gradient component near several degrees that is effective in eliminating moire is increased. It is difficult to eliminate both moire and front luminance. Moreover, unless a special apparatus is used, the number of steps for applying the cured layer increases, and an increase in production cost is inevitable.

<Polarizing plate>
The polarizing plate is mainly composed of two protective films that protect both the front and back sides of the polarizing film. The optical film of the present invention is preferably used for at least one of the two protective films sandwiching the polarizing film from both sides. The manufacturing cost of a polarizing plate can be reduced because the optical film of the present invention also serves as a protective film. The optical film of the present invention can also be used as the outermost layer of an image display device. In this case, reflection of outside light is prevented, and contrast in an environment with bright light (light room) is increased. It can be set as the polarizing plate which can be improved.

<Liquid crystal display device>
The optical film in the present invention is applied to a liquid crystal display (LCD). The optical film of the present invention can be used in combination with a polarizing plate as described above. When combined with a polarizing plate, the surface having light scattering properties is disposed on the light source side, and the other surface is on the liquid crystal cell side. To place. At this time, it is preferable to use a protective film having the optical compensation function as the protective film on the other side because the thickness can be further reduced. Alternatively, the liquid crystal cell substrate and a polarizing plate may be attached to each other.

  The optical film in the present invention, when used as one side of the surface protective film of the polarizing film, is twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), optically. It can be preferably used for a transmissive, reflective, or transflective liquid crystal display device in a mode such as a compensated bend cell (OCB).

<Configuration of backlight unit (BLU)>
The light-scattering film of the present invention can be used as a component of a surface light source device that requires uniform brightness, but is a backlight unit (light source of a liquid crystal display device such as a liquid crystal television, a PC monitor, and a mobile phone). (BLU).
The backlight unit is generally composed of a light emitting light source, a light guide plate, a reflection plate, a sheet having a condensing / diffusing function, and the like. For example, in FIG. 2B, the backlight unit 6 includes a light emitting light source 2, a light guide plate 13, a lower diffusion sheet 3, and a light collecting sheet 4. Each component will be described below.

In the present invention, the light source refers to a mechanism that is incident on the light scattering structure in a planar manner from a light emitting light source described later. For example, in FIG. 2B, the light source 1 includes a light emitting light source 2 and a light guide plate 13. A direct type (FIG. 2 (a)) that spreads the luminous flux by taking a distance from the light emitting light source, and a mode in which a light guide plate is used to make the light emitting light source that is a line light source or a point light source planar ( FIG. 2 (b)). In the edge light type, a light guide plate is essential, but it may be used even in a direct type. The light guide plate uses light reflection or scattering within the light guide plate by providing a through hole, unevenness or serrated portion on the light guide plate, and further providing a reflection portion or a scattering portion on the surface thereof. Is diffused in a planar shape.
Further, in order to effectively use light that does not go to the viewing side, a structure that reflects light in the viewing side direction using a reflector or the like is also used.
In the present invention, a plurality of types of light sources including a surface light source may be combined as the light emitting light source.
As a light-emitting light source (illuminant) used for the light source, CCFL (Cold Cathode)
Fluorescent Lamp, Cold Cathode Tube), HCFL (Hot Cathode)
Fluorescent Lamp (hot cathode tube), LED (Light Emitting Diode, light emitting diode), OLED (Organic light-emitting diode, organic light emitting diode [organic EL]), inorganic EL, and the like are used.

In order to collect and diffuse light from the light source described above to obtain uniform brightness, a structure that scatters light is used. These are formed by disposing a diffusion sheet, a lens sheet (prism sheet), etc. on a light source. In the present invention, including the above-mentioned light scattering film disposed as a protective film for a polarizing plate, “Structure having light scattering property” (also referred to as “light scattering structure”). For example, in FIG. 2B, the light scattering structure 15 includes a lower diffusion sheet 3, a light collecting sheet 4, and a light scattering film 14. The haze value of the light-scattering film 14 is preferably 0.1% or more from the viewpoint of preventing luminance unevenness, and is preferably 30% or less in consideration of the loss of front white luminance. For this reason, in terms of both luminance unevenness prevention and front white luminance, the haze value of the light-scattering film is preferably from 0.1% to 30%, particularly preferably from 10% to 30%.
Among these member configurations, an example of a configuration excluding the above-described light scattering film disposed as a protective film for a polarizing plate is shown in FIGS. 3 and 4. 3 and 4, the lower side of the structure is the light source side and the light source is disposed below the structure, while the upper side is the viewing side and the lower polarizing plate and the liquid crystal cell are disposed on the upper side. The light takes an optical path that passes from the lower side to the upper side to the viewer side. In addition, the light scattering characteristics required for the screen size and the arrangement of the light source are different. In addition, as a high-quality image application, there is a form in which a lens sheet or a diffusion sheet is frequently used to obtain more uniform luminance. In order to reduce the manufacturing cost, there is a form configured with a smaller number of parts, and therefore, the present invention is not limited to the mode shown in FIGS.
A lens sheet is a sheet (film or plate) that has a light condensing effect forward (perpendicular to the surface) to be a surface light source. The lens sheet has a sawtooth shape or a semi-elliptical shape (semi-elliptical column shape), and includes a so-called prism sheet in which quadrangular pyramidal protrusions are arranged in a planar shape. For example, BEF (manufactured by Sumitomo 3M) is known as a representative one.
The diffusion sheet is a translucent sheet (film or plate) for scattering and diffusing light, and is also called a diffusion film or a diffusion plate. Mainly used to make the entire wide surface uniform brightness by greatly diffusing light.
Furthermore, a functional sheet (film) such as a multifunctional sheet (film) having both functions of a lens sheet and a diffusion sheet and a polarized light separation film having a polarization selective layer (for example, DBEF (manufactured by Sumitomo 3M)), It may be used for thinning and high functionality.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” are based on mass.

Composition of coating solution A-1 for light scattering layer PET-30 65.0 g
Irgacure 127 3.0g
8μm cross-linked acrylic / styrene particles (30%) 15.0g
SP-13 0.2g
CAB 1.0g
MIBK 72.6g
MEK 32.5g

Composition of coating liquid A-2 for light scattering layer PET-30 40.0 g
Irgacure 127 3.0g
8 μm crosslinked acrylic particles (30%) 6.0 g
12μm cross-linked acrylic / styrene particles (30%) 18.0g
SP-13 0.2g
CAB 25.0g
MIBK 72.6g
MEK 32.5g

Composition of coating solution A-3 for light scattering layer PET-30 65.0 g
Irgacure 127 3.0g
8μm cross-linked acrylic particles (30%) 4.5g
12μm cross-linked acrylic / styrene particles (30%) 22.5g
SP-13 0.2g
CAB 1.0g
MIBK 72.6g
MEK 32.5g

  Each coating solution for the light scattering layer was filtered through a polypropylene filter having a pore size of 30 μm to prepare a coating solution. The refractive index of the matrix (light scattering layer excluding translucent particles) after curing in the coating solution was 1.525 for coating solution A-1 and coating solution A-3, and 1.510 for coating solution A-2. It was.

  Here, the refractive index of the matrix was directly measured with an Abbe refractometer. Further, the refractive index of the translucent particles was changed by changing the mixing ratio of two kinds of solvents having different refractive indexes selected from methylene iodide, 1,2-dibromopropane, and n-hexane. The turbidity was measured by dispersing an equal amount of translucent particles in the solvent, and the refractive index of the solvent when the turbidity was minimized was measured by an Abbe refractometer.

The refractive index of the translucent particles was as follows.
8 μm crosslinked acrylic particles 1.500
8μm cross-linked acrylic / styrene particles 1.515
12μm cross-linked acrylic / styrene particles 1.555

Composition of coating liquid L-1 for low refractive index layer Ethylenically unsaturated group-containing fluorine-containing polymer (A-1) 3.9 g
Silica dispersion A (22%) 25.0 g
Irgacure 127 0.2g
DPHA 0.4g
MEK 100.0g
MIBK 45.5g

The coating solution for the low refractive index layer was filtered through a polypropylene filter having a pore size of 1 μm to prepare a coating solution.
The refractive index after curing of the low refractive index layer obtained by coating and curing the coating solution was 1.360.

The compounds used are shown below.
PET-30: A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate [manufactured by Nippon Kayaku Co., Ltd.];
DPHA: a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate [manufactured by Nippon Kayaku Co., Ltd.];
8 μm cross-linked acrylic particles (30%): MIBK dispersion with a solid content concentration of 30%, in which an average particle size of 8.0 μm [manufactured by Soken Chemical Co., Ltd.] is dispersed for 20 minutes at 10,000 rpm with a Polytron disperser)
8 μm cross-linked acrylic / styrene particles (30%): average particle size 8.0 μm [manufactured by Sekisui Plastics Co., Ltd.] dispersed with a Polytron disperser at 10,000 rpm for 20 minutes, a 30% solid content concentration of MIBK dispersion )
12 μm cross-linked acrylic / styrene particles (30%): average particle size 12.0 μm [manufactured by Sekisui Plastics Co., Ltd.] dispersed at 10,000 rpm for 20 minutes in a Polytron disperser MIBK dispersion with a solid content concentration of 30% )
Irgacure 127: Polymerization initiator [Ciba Specialty Chemicals Co., Ltd.];
CAB: cellulose acetate butyrate [Eastman Chemical Co., Ltd.];
MEK: methyl ethyl ketone;
MIBK: methyl isobutyl ketone;
Ethylenically unsaturated group-containing fluoropolymer (A-1): fluoropolymer (A-1) described in Production Example 3 of JP-A-2005-89536;

  SP-13: Fluorine-based surfactant (used after dissolving as a 10% by mass solution of MEK)

(Silica dispersion A)
Hollow silica fine particle sol (Isopropyl alcohol silica sol, average particle diameter 60 nm, shell thickness 10 nm, silica concentration 20 mass%, silica particle refractive index 1.31, change size according to Preparation Example 4 of JP-A-2002-79616. Prepared) 10 g of acryloyloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of diisopropoxyaluminum ethyl acetate were added and mixed, and then 3 g of ion-exchanged water was added. After making it react at 60 degreeC for 8 hours, it cooled to room temperature and added 1.0 g of acetylacetone. While adding cyclohexanone to 500 g of this dispersion so that the content of silica was almost constant, solvent substitution by vacuum distillation was performed. There was no generation of foreign matter in the dispersion, and the viscosity when the solid content concentration was adjusted to 22% by mass with cyclohexanone was 5 mPa · s at 25 ° C. When the residual amount of isopropyl alcohol in the obtained silica dispersion A was analyzed by gas chromatography, it was 1.0%.

[Examples 1 to 5, Comparative Examples 2 and 3, Reference Example 2]
<Preparation of optical film samples 1-8>

(1) Coating of light scattering layer A triacetyl cellulose film (TAC-TD80U, manufactured by Fuji Film Co., Ltd.) having a thickness of 80 μm is unwound in a roll form, and coating liquid A-1 for light scattering layer is specially prepared. In a die coating method using a slot die as described in Example 1 of Kokai 2006-122889, coating was performed at a conveyance speed of 30 m / min, drying at 60 ° C. for 150 seconds, and oxygen concentration under a nitrogen purge of about 0.1. Using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) of 160 W / cm, the coating layer was cured by being irradiated with ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 100 mJ / cm ² . The coating amount was adjusted so that the film thickness of each light scattering layer was the value shown in Table 1.

(2) Coating of low refractive index layer The triacetylcellulose film coated with the light scattering layer is unwound again, and the coating solution L-1 for the low refractive index layer is formed by a die coating method using the slot die. , Coated at a transfer speed of 30 m / min, dried at 90 ° C. for 75 seconds, and then air-cooled metal halide lamp (produced by Eye Graphics Co., Ltd.) with an oxygen concentration of 0.01 to 0.1% and 240 W / cm under a nitrogen purge. ) Was irradiated with ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 240 mJ / cm ² to form a low refractive index layer having a thickness of 100 nm, and wound up to produce an optical film.

[Example 6]
<Preparation of optical film sample 9>
The light scattering layer coating liquid A-2 is used as the light scattering layer coating liquid, and the conveying speed is set to 5 m / min when the light scattering layer is applied. An optical film sample 9 was produced. The coating amount was adjusted so that the thickness of the light scattering layer was the value shown in Table 1.

[Example 7]
<Preparation of optical film sample 10>
Optical film sample 10 was produced in the same manner as optical film samples 1 to 8, except that light scattering layer coating liquid A-3 was used as the light scattering layer coating liquid. The coating amount was adjusted so that the film thickness of each light scattering layer was the value shown in Table 1.

[Example 8]
<Preparation of optical film sample 11>
An optical film sample 11 was produced in the same manner as the optical film sample 10 except that the low refractive index layer was not applied. The coating amount was adjusted so that the thickness of the light scattering layer was the value shown in Table 1.

(Evaluation of optical film)
About these obtained optical film samples, the following items were evaluated. The results are shown in Table 1.

(1) Transmission image definition For the measurement of the image definition (%) of the optical film, ICM-1T manufactured by Suga Test Instruments Co., Ltd. was used in accordance with JIS K7105 (1999 edition). The image definition optical comb in the present invention is defined as a value measured at 2.0 mm.

(2) Haze The total haze value (H) of the obtained optical film was measured according to JIS-K7136.

(3) Centerline average roughness Ra:
According to JIS-B0601 (1982), the center line average roughness (Ra) (μm) was measured using a surf coder MODEL SE-3F manufactured by Kosaka Laboratory.
The measurement conditions were an evaluation length of 2.5 mm, a cutoff of 0.25 mm, a speed of 0.5 mm / s, a probe diameter of 2 μm, and a load of 30 μN.

(4) Light Scattering Profile Measurement was performed using a photogoniometer (GP-5, manufactured by Murakami Color Research Laboratory) (see FIG. 11). The light source was converged at an angle of 1.5 °, and the light receiving angle of the detector was 2 °. Light was incident from the normal direction of the obtained optical film, and the amount of transmitted and scattered light was measured while continuously changing the angle in a plane including the film normal, thereby obtaining a light scattering profile. The amount of transmitted and scattered light was expressed as a relative value with respect to the light amount of the light source, with the light amount of the light source in the absence of the film being 1.

(Saponification of optical film)
About the optical film samples 1-11 obtained above, the following processes were performed.
A 1.5 mol / L aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.01 mol / L dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The produced optical film was immersed in the aqueous sodium hydroxide solution for 2 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C.
In this way, a saponified optical film was produced.

(Preparation of polarizing plate)
An 80 μm-thick triacetyl cellulose film (TAC-TD80U, manufactured by Fuji Film Co., Ltd.), which was neutralized and washed with water after being immersed in a 1.5 mol / L, 55 ° C. NaOH aqueous solution for 2 minutes, and the produced optical Polarizer samples 1 to 11 were prepared by adhering and protecting both sides of a polarizing film prepared by adsorbing iodine to polyvinyl alcohol and stretching the film on each film sample (saponified).

<Production of liquid crystal display device>
LG Display's notebook PC (R700-XP50K) is a product obtained by performing AG (anti-glare) treatment on the backlight side polarizing plate of the liquid crystal panel, and the performance of each sample was evaluated using this. As a result of disassembling and examining the notebook PC, the configuration shown in FIG. 1B (specifically, the backlight unit is laminated on the light guide plate in the order of a lower diffusion sheet, two prism sheets, and an upper diffusion sheet). Structure). The upper diffusion sheet of this backlight unit was removed and used for evaluation. In the evaluation, the polarizing plate on the backlight side was peeled off, and the polarizing plate samples 1 to 11 were attached thereto with adhesive materials so that the protective film (TAC-TD80U) side was the liquid crystal cell side. In addition, the case where the polarizing plate (TAC-TD80U is used as a backlight side protective film) without a light-scattering film was affixed as [Comparative Example 1]. Moreover, the case where the AG process polarizing plate with which the said notebook PC product was equipped was used as [Reference example 1].

(Evaluation of liquid crystal display devices)
<Luminance unevenness>
A signal is input from the video signal generator (VG-848; manufactured by ASTRODESIGN Co., Ltd.) to the liquid crystal display device thus produced, and the entire screen is displayed in gray with 128/256 gradations, and the screen is displayed from various directions under a dark room. Visual observation was performed to evaluate the presence or absence of luminance unevenness (sensory evaluation of display unevenness including occurrence of moire and the like).
○: Brightness unevenness is not observed. Δ: Brightness unevenness is observed weakly. ×: Brightness unevenness is clearly observed. In addition, although in-plane brightness unevenness was observed in the above-described environment, the examples were uniform without unevenness. Met. On the other hand, in the comparative example, there was an apparently unnatural luminance unevenness in the surface.

<Front white brightness>
The liquid crystal display device is made to display a 256/256 gray scale white display on the entire surface in the same manner as the evaluation of luminance unevenness, and a luminance meter (BM5-A; Co., Ltd.) from the normal (front) direction of the liquid crystal display device plane in a dark room. The brightness was measured by Topcon). In addition, the case where a light-scattering film is not used for the surface of the backlight side polarizing plate is used as a reference.
○: Not lowered at all (99% or more of the standard value)
Δ: Slightly decreased (95% to less than 99% of the reference value)
X: Decreasing (less than 95% of the reference value)
The results are shown in Table 1 below.

[Production of light-scattering substrate]
With the dope formulation shown in Table 2, each dope was prepared, and the base layer dope and the surface layer dope were cast simultaneously so as to have the configuration shown in Table 3, to prepare light scattering base material samples 21 to 35. The samples 21 to 33 and 35 were cast using the casting apparatus shown in FIG. 9 so that the dope for the surface layer 1 was mirror-finished and cooled to −10 ° C., and the solvent was volatilized. The gel was formed by cooling, and the web was peeled off. It was dried with hot air at 100 ° C. until the residual solvent amount was 10% by mass, and then dried with hot air at 140 ° C. for 10 minutes. The light scattering substrate sample 34 was cast on a mirror-finished band of 18 ° C. using the casting apparatus shown in FIG. All of the obtained light-scattering substrate samples had a refractive index of 1.48.

  Table 4 below shows the evaluation results of each light-scattering substrate sample and the display performance when it is used as the backlight-side polarizing plate protective film of the liquid crystal display device.

The materials used are shown below.
Cellulose triacetate: Degree of acetyl substitution 2.86, Viscosity average degree of polymerization 310
Ultraviolet absorber: Benzotriazole ultraviolet absorber (20/80 mass% mixture of TINUVIN326 / TINUVIN328, each manufactured by Ciba Japan Co., Ltd.)
R972: primary particle size of about 16 nm, AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd. S431: average particle size of about 2.5 μm, silicia 431, manufactured by Fuji Silysia Chemical Co., Ltd. 2000M: melamine resin spherical particles, average particle size of 2. 0 μm, Optobead 2000M, manufactured by Nissan Chemical Co., Ltd. KEP-150: Silica spherical particles, average particle size 2.5 μm, Seahosta KEP-150, manufactured by Nippon Shokubai Co., Ltd. MX-350: Crosslinked polymethylmethacrylate spherical particles XX-82S: Cross-linked polymethyl methacrylate true spherical particles, average particle size 6 μm, Sekisui Plastics Co., Ltd. XX-76S: Cross-linked polymethyl methacrylate true spherical particles , Average particle size 8 μm, manufactured by Sekisui Plastics Co., Ltd. XX-147S: crosslinked polymethyl methacrylate Len copolymer true spherical particles, average particle size 8 μm, manufactured by Sekisui Plastics Co., Ltd. MX-1500: Cross-linked polymethylmethacrylate true spherical particles, average particle size 20 μm, manufactured by Soken Chemical Co., Ltd. The concentration was adjusted to 23 mass%, and the solid content concentration of the surface layer dope was adjusted to 18 mass% with a mixed solvent of methylene chloride: methanol 90:10 mass ratio.
In addition, the refractive index of the particles is measured by measuring the turbidity by dispersing the same amount of particles in the solvent in which the refractive index is changed by changing the mixing ratio of two types of solvents having different refractive indexes. The refractive index of the solvent was measured by measuring with an Abbe refractometer.

<Production of polarizing plate and liquid crystal display device>
About the film samples 21-35, the polarizing plate and the liquid crystal display device were produced similarly to the said Examples 1-8. In addition, the polarizing plate was produced so that the surface layer 1 side of a light-scattering base material might be a polarizing film side, and the liquid crystal display device was produced so that the TAC-TD80U side of a polarizing plate might be a liquid crystal cell side.

<Evaluation of Light Scattering Substrate and Liquid Crystal Display>
The light-scattering substrate and the liquid crystal display device were evaluated in the same manner as in Examples 1-8. The results are shown in Table 4 below.

  From Table 4, by using the optical film of the present invention as a backlight-side polarizing plate protective film of a liquid crystal display device, a liquid crystal display device in which a decrease in white luminance and moire in the front did not occur was obtained. As described above, the liquid crystal display device according to the present invention has an optical comb having a width of 2 mm using the image sharpness measuring device based on JIS K 7105 as the light scattering characteristic of the optical film used instead of the upper diffusion sheet. It has been found that moire and luminance unevenness can be reduced by having a light scattering property with an image definition value of 9.5% to 61.5%. In addition, the present inventor prepared the sample of the example so that the scattering intensity is given only to the scattering angle that effectively acts. In other words, the forward scattering property is slightly strong and the relative scattering intensity in the vicinity of 2 ° to 6 ° is large, and the wide angle scattering due to multiple scattering is prevented. It has been found that both the maintenance of contrast can be achieved.

1 Light source 2 Light emitting light source 3 Lower diffusion sheet (or diffusion plate)
4 Light collecting sheet (prism sheet, lens sheet)
5 Upper diffusion sheet 6 Backlight unit 7 Liquid crystal cell 8 Transparent substrate (glass, plastic)
9 Protective film (or phase difference film)
DESCRIPTION OF SYMBOLS 10 Polarizing film 11 Protective film 12 Liquid crystal panel 13 Light guide plate 14 Optical film having scattering properties (also serving as a protective film)
15 Structure 21 with Light Scattering 21 Diffusion Sheet 22 Lens Sheet 23 Diffusion Plate 24 Multifunctional Sheet 30 Casting Die 32 Manifold 33 Feed Block 41 Light Transmitting Base Material 42 Base Layer 43 Surface Layer 44 Surface Layer 44a Surface Layer 44b Surface Layer 45 Cured Layer 46 Transparent Photoconductive particle 47 Second hardened layer 51 Stirrer 52 Transfer pump 53 Filter 54 Stock tank 55a Casting liquid pump for back layer 55b Casting liquid pump for base layer 55c Casting liquid pump for surface layer 55d Flow for outermost layer Extended liquid pump 56a Additive injection pump (solvent, matting agent, etc.)
56c Additive infusion pump (solvent, translucent particles, etc.)
56d Additive infusion pump (solvent, translucent particles, etc.)
57 Casting die 58 Casting band 59 Decompression chamber 60 Casting drum

That is, the present inventors achieved the above object with the following configurations.
<1>
A liquid crystal display device having a backlight having an image definition value of 30% to 61.5% measured through an optical comb having a width of 2 mm using an image definition measuring device based on JIS K 7105 A liquid crystal display device comprising a light-scattering optical film as a backlight-side polarizing plate protective film, a condensing sheet between a light source and a liquid crystal cell, and no upper diffusion sheet.
<2>
<1> The liquid crystal display device according to <1>, wherein the optical film has an image definition value of 30% to 55%.
<3>
The liquid crystal display device according to <1> or <2>, having a light-scattering structure including an optical film having a haze of 0.1% to 30% between the light source and the liquid crystal cell.
<4>
<1> to <1, wherein a polarizing plate is provided between the light source and the liquid crystal cell, and an optical film having a light scattering property having a haze of 0.1% to 30% is laminated on the polarizing plate. 3. A liquid crystal display device according to any one of 3>.
<5>
The optical film has a light scattering layer, and the center line average roughness Ra of the surface of the optical film having the light scattering layer is 0.004 μm to 0.45 μm <1> The liquid crystal display device according to any one of to <4>.
<6>
The optical film has a scattering intensity value at an emission angle of 4 ° with respect to a light source of a scattered light profile measured by a goniophotometer with a light reception angle of 2 ° is 0.03 to 0.07, <1 The liquid crystal display device according to any one of> to <5>.
<7>
<1>-<6> The liquid crystal display device according to any one of <1> to <6>, wherein the optical film includes cross-linked resin particles having translucent particles having an average particle diameter of more than 2.5 μm and not more than 20 μm.
<8>
Any one of <1> to <7>, wherein the optical film includes a light-transmitting substrate containing cellulose acylate and a light scattering layer, and the film thickness of the optical film is 20 μm to 200 μm. 2. A liquid crystal display device according to item 1.
<9>
Any one of <5> to <8>, comprising a step of forming a light scattering layer by applying a composition containing translucent particles and a matrix-forming component onto a light transmissive substrate. A method for producing a liquid crystal display device according to claim 1.
<10>
The liquid crystal display device according to any one of <1> to <8>, wherein the optical film is a polarizing plate protective film.
In addition, although this invention is related to said <1>-<10>, the other matter (For example, the matter regarding following 1.-9.) Was also described for reference.
1. A liquid crystal display device having a backlight having an image definition value of 9.5% to 61.5% measured through an optical comb having a width of 2 mm using an image definition device based on JIS K 7105 A liquid crystal display device comprising an optical film having a light scattering property between a light source and a liquid crystal cell.
2. 2. The liquid crystal display device according to 1 above, wherein the liquid crystal display device has a light-scattering structure including an optical film having a haze of 0.1% to 30% between the light source and the liquid crystal cell.
3. 3. The above 1 or 2, wherein a polarizing plate is provided between the light source and the liquid crystal cell, and an optical film having a light scattering property having a haze of 0.1% to 30% is laminated on the polarizing plate. Liquid crystal display device.
4). The optical film has a light scattering layer, and the value of the center line average roughness Ra on the surface of the optical film having the light scattering layer is 0.004 μm to 0.45 μm. 4. The liquid crystal display device according to any one of 3.
5. The optical film has a scattering intensity value at an emission angle of 4 ° with respect to a light source of a scattered light profile measured by a goniophotometer with a light reception angle of 2 ° is 0.03 to 0.07. The liquid crystal display device in any one of -4.
6). 6. The liquid crystal display device as described in any one of 1 to 5 above, wherein the optical film contains crosslinked resin particles having an average particle size of more than 2.5 μm and 20 μm or less as translucent particles.
7). The optical film includes a light-transmitting substrate containing cellulose acylate and a light scattering layer, and the film thickness of the optical film is 20 μm to 200 μm. Liquid crystal display device.
8). 8. The liquid crystal display as described in any one of 4 to 7 above, which comprises a step of forming a light scattering layer by applying a composition containing translucent particles and a matrix-forming component onto a light transmissive substrate. Device manufacturing method.
9. 8. The liquid crystal display device according to any one of 1 to 7, wherein the optical film is a polarizing plate protective film.

Claims (9)

  A liquid crystal display device having a backlight having an image definition value of 9.5% to 61.5% measured through an optical comb having a width of 2 mm using an image definition device based on JIS K 7105 A liquid crystal display device comprising an optical film having a light scattering property between a light source and a liquid crystal cell.   2. The liquid crystal display device according to claim 1, further comprising a light-scattering structure including an optical film having a haze of 0.1% to 30% between the light source and the liquid crystal cell.   3. A polarizing plate is provided between the light source and the liquid crystal cell, and an optical film having a light scattering property having a haze of 0.1% to 30% is laminated on the polarizing plate. The liquid crystal display device described.   The optical film has a light scattering layer, and the center line average roughness Ra of the surface of the optical film on the side having the light scattering layer is 0.004 μm to 0.45 μm. The liquid crystal display device in any one of -3.   The value of the scattering intensity at an outgoing angle of 4 ° with respect to the light source of the scattered light profile measured by a goniophotometer with a receiving angle of 2 ° of the optical film is 0.03 to 0.07. The liquid crystal display device in any one of 1-4.   The liquid crystal display device according to claim 1, wherein the optical film includes crosslinked resin particles having an average particle size of more than 2.5 μm and 20 μm or less as translucent particles.   The optical film includes a light-transmitting substrate containing cellulose acylate and a light scattering layer, and the film thickness of the optical film is 20 μm to 200 μm. Liquid crystal display device.   The liquid crystal according to any one of claims 4 to 7, further comprising a step of forming a light scattering layer by applying a composition containing translucent particles and a matrix-forming component onto a light transmissive substrate. Manufacturing method of display device.   The liquid crystal display device according to claim 1, wherein the optical film is a polarizing plate protective film.

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