JP2008058386A - Optical element and polarizing plate having the same, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element that can suppress changes in colors or gradation depending on viewing angles, and to provide a polarizing plate having the optical element, and a liquid crystal display device. <P>SOLUTION: The optical element 10 comprises a plastic base film 8 and a diffusion layer 9, wherein the diffusion layer 9 has an internal scattering body 12 that selectively scatters light at a short wavelength and is specified to have pencil hardness of 2H or higher at 500 g load. When the optical element is used as disposed in the front face A1 side of a liquid crystal display device, a color difference Δu'v' defined below upon displaying colors near eight test colors specified as the test colors by CIE1974 is specified to 0.05 or less: the color difference is obtained from the chromaticity coordinates (u<SB>0</SB>', v<SB>0</SB>') of CIE1976UCS observed from an opposing position straight to the front face A1 of the liquid crystal display device and the chromaticity coordinates (u', v') observed at an observation angle θ changed by ±60° in the horizontal or vertical direction from the above position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element capable of forming a liquid crystal display device which suppresses a decrease in luminance of the liquid crystal display device by scattering (diffusing) light and has little color change due to a difference in viewing angle, and a polarizing plate provided with the optical element The present invention also relates to a liquid crystal display device.

  2. Description of the Related Art Conventionally, for example, a liquid crystal display device provided in a liquid crystal television, a car navigation system, a monitor for a personal computer, and the like includes a liquid crystal panel and a backlight that is disposed opposite to the liquid crystal panel and emits light to the liquid crystal panel. Yes. The liquid crystal panel includes, for example, a liquid crystal cell composed of a pair of substrates provided with electrodes for applying a voltage to liquid crystal composed of rod-shaped liquid crystal molecules and sandwiched liquid crystal, and a front surface (front surface) that displays an image of the liquid crystal display device. ) RGB color filter interposed between one liquid crystal cell substrate disposed on the side, and a pair of polarizing plates disposed so as to sandwich the liquid crystal cell and transmitting only light in one direction of vibration. Configured.

  In addition, this type of liquid crystal display device has a TN (Twisted Nematic) type, a VA (Vertical Alignment) type, and an IPS (In Plane Switching) type depending on a difference in alignment direction (alignment) of liquid crystal molecules according to a voltage application state. , And OCB (Optically Compensated Bend) type. Among these, in the TN type liquid crystal display device, liquid crystal molecules are twisted and arranged at 90 degrees about the direction perpendicular to the substrate (twisted orientation) in a state where no voltage is applied. When the light transmitted through the other polarizing plate travels along the twisted arrangement of liquid crystal molecules, the direction of vibration changes to the same direction as the transmission axis of one polarizing plate, To Penetrate. On the other hand, when a voltage is applied, the alignment of the liquid crystal molecules changes in the vertical direction along the electric field, and the light traveling along the liquid crystal molecules aligned in the vertical direction is blocked by one polarizing plate. The display / non-display of the image is controlled by the arrangement of the liquid crystal molecules and the light transmission state that change in accordance with the voltage application state.

  However, in this TN liquid crystal display device, the alignment of the liquid crystal molecules is aligned in one vertical direction when a voltage is applied, so that the light in the vertical direction is completely blocked, but the light in the oblique direction is not blocked. Leaks. For this reason, when the liquid crystal display device is viewed from the direction facing the front and the oblique direction, the amount of transmitted light is different in each direction and the appearance changes greatly (that is, the viewing angle is small). There was a problem. In addition, since the liquid crystal molecules are twisted, even if the polarization is corrected using a retardation film (a film having biaxial refractive index anisotropy), the contrast is inverted only in one direction. There was a drawback.

  In the VA liquid crystal display device, liquid crystal molecules are arranged in a vertical direction (vertical alignment) without applying a voltage, and when a voltage is applied, the arrangement direction of the liquid crystal molecules changes in a horizontal direction parallel to the substrate. To transmit light. By vertically aligning the liquid crystal molecules in a state where no voltage is applied in this way, the contrast is higher than that of the TN type, and the gradation of the black portion can be easily reproduced. However, this VA liquid crystal display device also has a problem that the gamma (gradation characteristic) changes depending on the viewing angle and the color changes depending on the viewing angle, such as the screen looks whitish when viewed from an oblique direction. It was. In addition, even when a retardation film is applied to this VA liquid crystal display device, the effect is obtained only when the liquid crystal is vertically aligned, and the polarization is corrected for intermediate gradations. Therefore, no effect is obtained with respect to the change in gradation depending on the viewing angle, and the color change for blue having a short wavelength (400 nm to 500 nm) cannot be eliminated particularly in the intermediate gradation.

  On the other hand, for example, the liquid crystal display device disclosed in Patent Document 1 includes a backlight (surface light source), a liquid crystal panel, a polarizing plate, a retardation film, and a light diffusion layer. In this liquid crystal display device, by adding a light diffusing layer, black retardation in the oblique direction is suppressed by the retardation film, gradation inversion is eliminated in the light diffusing layer, and the contrast is high, especially in the downward direction. A wide-field display without inversion is possible.

Further, for example, as disclosed in Patent Document 2, a retardation layer (b) is disposed between at least two reflective polarizers (a) in which the wavelength bands of selective reflection of polarized light overlap each other. A backlight system in which a diffusing light source is converted into a parallel light using a polarizing element (A), a liquid crystal cell through which the parallel light is transmitted, a polarizing plate disposed on both sides of the liquid crystal cell, and a liquid crystal cell There is a liquid crystal display device configured to include a viewing angle widening layer that diffuses a transmitted light beam disposed on the viewing side. In this liquid crystal display device, the above-described backlight system focuses the emitted light only in the viewing angle region where the contrast is the highest and the color reproducibility is good, that is, the light passing through in an oblique direction is focused in the front direction. By averaging the light rays, a liquid crystal display device having a high resistance to gradation inversion and color change and a good viewing angle characteristic is obtained.
Japanese Patent Laid-Open No. 10-10513 JP 20044763 A

  However, in the liquid crystal display device disclosed in Patent Document 1 described above, the viewing angle can be expanded and gradation inversion can be prevented, but the color change when viewed from different directions is sufficient. It cannot be suppressed. Also, the liquid crystal display device disclosed in Patent Document 2 is expensive because the structure of the backlight system for focusing light in the front direction is complicated. Further, Patent Document 2 that discloses this liquid crystal display device does not particularly specify the configuration of the diffusion film, and does not refer to the color correction effect, and thus sufficiently suppresses the color change when viewed from different directions. I can't judge it.

  On the other hand, although a diffusion film having an antiglare function (antiglare film) has been put into practical use, since this type of diffusion film does not have a color correction function, it is still possible to sufficiently suppress color change. Can not. In addition, when considering use as a liquid crystal display device, particularly a television application, a hard coat layer for protecting the front (front) side for displaying an image, an antiglare layer for preventing reflection of external light, etc. Must be provided separately. On the other hand, in recent years, liquid crystal display devices are strongly demanded to reduce costs, so that these hard coat layers, antiglare layers, and optical elements having only a color correction effect are individually provided as a panel configuration. This leads to an increase in the number of manufacturing steps of the member, leading to an increase in cost due to a deterioration in manufacturing yield. For this reason, development of an optical element having a color correction effect while having a hard coat property and an antiglare property is strongly demanded.

  Therefore, the present invention has been made in view of the above circumstances. First, a color change and a gradation change are caused by a viewing angle with respect to a liquid crystal display device, particularly a liquid crystal display device such as a VA type liquid crystal television. An object of the present invention is to provide an optical element that can be suppressed, a polarizing plate provided with the optical element, and a liquid crystal display device. Second, the cost due to an increase in the manufacturing process of components by imparting hard coat properties and / or anti-glare properties It is an object of the present invention to provide an optical element capable of suppressing an increase, a polarizing plate including the optical element, and a liquid layer display device.

  In order to achieve the above object, the present invention provides the following means.

The optical element of the present invention is formed by forming a diffusion layer for scattering transmitted light on at least one surface of a plastic substrate film, and is used by being arranged on the front side for displaying an image of a liquid crystal display device. The optical element, wherein the diffusion layer is an inner surface scatterer having a refractive index different from the refractive index of the medium that selectively scatters a short wavelength within the wavelength range of visible light (Mie scattering) in the medium. As a test color, the pencil hardness at a load of 500 g (4.9 N) is set to 2H or more, and when placed on the front side for displaying an image of the liquid crystal display device, it is used as a test color. CIE1976UCS chromaticity coordinates (u ₀ ′, v ₀ ′) observed in a state where the colors near the eight test colors specified in CIE 1974 are displayed on the liquid crystal display device and are directly facing the front surface of the liquid crystal display device. )When The color difference Δu′v ′ obtained by the following equation is within 0.05 based on the chromaticity coordinates (u ′, v ′) of CIE 1976 UCS observed with the observation angle changed ± 60 degrees horizontally or vertically. It is formed as follows.
Δu′v ′ = {(u′−u ₀ ′) ² + (v′−v ₀ ′) ² } ^0.5

  In the optical element of the present invention, it is desirable that the diffusion layer has a thickness of 2 to 30 μm.

  Furthermore, in the optical element of the present invention, it is more desirable that the diffusion layer is constituted by dispersing the inner surface scatterer in the radiation curable resin of the medium.

  In the optical element of the present invention, it is more desirable that the size (average diameter) of the inner surface scatterer is 0.2 to 3 μm.

  Furthermore, in the optical element of the present invention, it is desirable that the refractive index difference between the medium and the inner scatterer is 0.05 to 0.6.

  In the optical element of the present invention, the inner scatterer is more preferably a particle.

  Furthermore, in the optical element of the present invention, it is desirable that the surface of the diffusion layer is formed in an uneven shape and has an antiglare layer.

  Further, in the optical element of the present invention, a part of the unevenness forming particles mixed in the inner surface scatterer and / or the medium of the diffusion layer protrudes outward and the surface is formed in an uneven shape. desirable.

  Furthermore, in the optical element of the present invention, the surface of the diffusion layer may be formed in an uneven shape by embossing.

  In the optical element of the present invention, it is desirable that the liquid crystal display device includes a vertical alignment type liquid crystal cell.

  The polarizing plate of the present invention is characterized in that any one of the optical elements described above is disposed on a polarizing layer.

  The liquid crystal display device of the present invention is characterized in that the above polarizing plate is disposed on the front side for displaying an image of the liquid crystal display device.

  According to the optical element of the present invention, when the optical element is disposed and used on the front side displaying an image of the liquid crystal display device, the optical element is changed by ± 60 degrees from the state facing the front of the liquid crystal display device. When the color difference obtained from the chromaticity coordinates is within 0.05, it is possible to suppress a color change or a gradation change depending on the viewing angle without causing a decrease in contrast and luminance. In addition, the short wavelength in the visible light wavelength range is selectively scattered (Mie scattering) by the inner surface scatterer of the diffusion layer, so that the color change with respect to blue having a short wavelength (400 nm to 500 nm) particularly in the intermediate gradation. Can be reliably eliminated. Further, since the optical element is formed so that the pencil hardness at a load of 500 g (4.9 N) is 2H or more, one optical element has a hard coat property in addition to an effect of suppressing color change. Thus, it is possible to suppress an increase in cost due to an increase in manufacturing steps of the constituent members.

  Further, in the optical element of the present invention, the thickness of the diffusion layer is 2 to 30 μm, so that the optical element can be surely formed with a pencil hardness of 2H or more. Light transmitted in different directions can be sufficiently mixed and scattered (diffused) by the inner scatterer, and color correction can be reliably performed by the effect of wavelength dependency of diffusion.

  Further, in the optical element of the present invention, the diffusion layer is configured by dispersing the inner surface scatterer in the radiation curable resin of the medium, thereby reliably scattering the light transmitted through the diffusion layer. In addition, when the diffusion layer is formed, it is cured by a simple method of irradiating with radiation such as ultraviolet rays at the stage where a mixed liquid in which the radiation curable resin and the inner surface scatterer are mixed is applied onto the plastic substrate film. Therefore, it is possible to reliably form a diffusion layer in which the inner surface scatterers are dispersedly arranged.

  Further, in the optical element of the present invention, the size (average diameter) of the inner surface scatterer is 0.2 to 3 μm, so that the backscattering is surely reduced and the short wavelength light is selectively scattered. The scattering angle can be increased, the viewing angle can be enlarged, and the effect of gradation and color correction can be reliably obtained while suppressing the decrease in contrast and the decrease in luminance.

  Furthermore, in the optical element of the present invention, the difference in refractive index between the medium and the inner surface scatterer is 0.05 to 0.6, so that backscattering can be reduced more reliably and light with a short wavelength can be selectively selected. It is possible to scatter, and it is possible to scatter (diffuse) the light with certainty to increase the viewing angle, and to obtain the effect of gradation and color correction reliably while suppressing the decrease in contrast and the decrease in luminance. be able to.

  Further, in the optical element of the present invention, since the inner surface scatterer is a particle, the inner layer scatterer can be reliably dispersed and arranged in the medium, and the diffusion layer and the optical element are provided so as to reliably scatter (diffuse) light. It becomes possible to form.

  Furthermore, in the optical element of the present invention, the surface of the diffusion layer is made uneven by projecting or embossing a part of the unevenness forming particles mixed in the inner scatterer and / or the diffusion layer medium. By forming it in a shape, it is possible to impart antiglare properties, and by arranging the surface of this optical element on the outermost surface of the liquid crystal display device, it becomes possible to prevent reflection of external light. As a result, in addition to the effect of suppressing color change, it is possible to impart anti-glare and hard coat properties to one optical element, so it is possible to reliably suppress an increase in cost due to an increase in the manufacturing process of components. become.

  In addition, the optical element of the present invention can be applied to a liquid crystal display device having a vertical alignment type liquid crystal cell to provide features such as expressive power and low cost of a dark portion of a liquid crystal display device such as a VA type liquid crystal television. It is possible to provide a liquid crystal display device in which color change is eliminated while maintaining.

  Furthermore, according to the polarizing plate and the liquid crystal display device of the present invention, the polarizing plate and the liquid crystal display device having the above effects are formed by arranging the optical element on the polarizing layer and integrally forming the polarizing plate and the liquid crystal display device. be able to.

  It should be noted that in order to have a color correction effect, almost no effect can be obtained outside the scope of the present invention described above, or a decrease in luminance, a decrease in contrast, blurring, etc. are not allowed. These requirements are indispensable in order to achieve the objectives. In addition, in the conventional invention, there is one in which a diffusion film is arranged on the front surface of the liquid crystal panel for the purpose of expanding the viewing area of the liquid crystal of other orientation such as TN type liquid crystal. The invention is not a main purpose but a color correction effect, and the idea itself is different and cannot be easily reached from these conventional techniques.

  Hereinafter, an optical element according to a first embodiment of the present invention, a polarizing plate including the optical element, and a liquid crystal display device will be described with reference to FIGS. The present embodiment relates to a liquid crystal display device such as a liquid crystal television including a VA type liquid crystal panel in which liquid crystal molecules are vertically aligned, and in particular, an optical element (optical film) that suppresses a color change and a gradation change depending on a viewing angle, and the same. The present invention relates to a liquid crystal display device including a polarizing plate.

  The liquid crystal display device A of the present embodiment includes a liquid crystal panel 1 and a backlight 2 that irradiates light to the liquid crystal panel 1, and the liquid crystal panel 1 is a flat VA type as shown in FIG. Polarizing plates 4 and 5 are laminated and arranged on both surfaces of the liquid crystal cell 3 so as to sandwich the liquid crystal cell 3 respectively. In the liquid crystal panel 1, the front surface 4 a of one polarizing plate 4 is disposed on the front (front surface) A 1 side of the liquid crystal display device A, and the other polarizing plate 5 and the liquid crystal are disposed on the back surface 5 a side of the other polarizing plate 5. The backlight 2 is disposed so as to transmit light in the order of the cell 3 and the one polarizing plate 4.

  The polarizing plate 4 is formed by sandwiching a polarizing layer 6 between a transparent plastic base film 7 and a plastic base film 8. Further, the polarizing plate 5 that forms a pair with the polarizing plate 4 has a structure in which a polarizing layer is sandwiched between two plastic substrates, similarly to the polarizing plate 4. In one polarizing plate 4 arranged on the front surface A1 side of the liquid crystal display device A, as shown in FIGS. 1 and 2, a diffusion layer 9 is further laminated on one surface 8a of the plastic substrate film 8. The optical film (optical element) 10 is laminated and formed so that the diffusion layer 9 is disposed on the front surface A1 side and the other surface 8b of the plastic base film 8 of the optical film 10 is in contact with the polarizing layer 6. Has been. The optical film 10 may be configured by laminating and forming a diffusion layer 9 on the other surface 8b of the plastic base film 8. In this case, the diffusion layer 9 on the other surface 8b side is used as the polarizing layer. 6 is placed in contact with the optical film 10.

  The plastic base film 8 of the optical film 10 is, for example, a triacetyl cellulose (TAC) film, a polyethylene terephthalate (PET) film, a cycloolefin-based film, etc. There is no need to limit the material.

  On the other hand, in the present embodiment, as shown in FIGS. 1 to 3, the diffusion layer 9 is formed by dispersely arranging inner surface scatterers (particles) 12 in a radiation curable resin (medium) 11. Here, the inner surface scatterer 12 has a refractive index different from the refractive index of light of the radiation curable resin 11, and the inner surface scatterer 12 is dispersedly arranged in the radiation curable resin 11. In the diffusion layer 9, a plurality of fine regions having different refractive indexes made of the inner scatterer 12 are formed. And by this inner surface scatterer 12, according to the particle diameter (size) of the inner surface scatterer, the short wavelength light in the wavelength range of visible light irradiated from the backlight 2 and transmitted through the diffusion layer 9 becomes stronger. It is formed so as to be (selectively) scattered (Mie scattering). The inner scatterer 12 may be uniformly distributed in the radiation curable resin 11 (in the diffusion layer 9) or may be unevenly distributed.

  The radiation curable resin 11 is preferably one having an acrylate functional group, more preferably polyester acrylate or urethane acrylate. Here, the polyester acrylate is preferably composed of a polyester polyol oligomer acrylate or methacrylate (hereinafter, acrylate and / or methacrylate is simply referred to as (meth) acrylate) or a mixture thereof. . Moreover, urethane acrylate is comprised from what acrylate-ized the oligomer which consists of a polyol compound and a diisocyanate compound.

 The monomer constituting the acrylate is preferably methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) ) Acrylate, phenyl (meth) acrylate, and the like.

 A polyfunctional monomer may be used in combination. For example, as the polyfunctional monomer, trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) Examples include acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate.

 Examples of polyester oligomers include adipic acid and glycol (ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butylene glycol, polybutylene glycol, etc.) and triol (glycerin, trimethylolpropane, etc.), sebacic acid, glycol, and triol. And polyadipate polyol, which is a condensation product with polysebacate polyol, and the like.

 Moreover, in order to advance the polymerization of the radiation curable resin 11 efficiently, a polymerization initiator (I) may be blended, and this polymerization initiator (I) is not particularly limited and is active. Any compound that generates radicals when irradiated with energy may be used. For example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2, 2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl 1-propan-1-one, 2-benzyl-2 -Dimethylamino-1- (4-morpholinophenyl) butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like can be used. The blending amount of the polymerization initiator (I) is 0.1 to 10 parts by weight, preferably 1 to 7 parts by weight, and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the radiation curable resin.

  Examples of the solvent include ketones such as methyl ethyl ketone, acetone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate, aromatic compounds such as toluene and xylene, ethers such as diethyl ether and tetrahydrofuran, methanol And alcohols such as ethanol and isopropanol.

  On the other hand, the inner surface scatterer 12 of the present embodiment includes, for example, powdery powder, glass beads, finely pulverized glass fibers, titanium oxide, calcium carbonate, silicon dioxide (silica), aluminum oxide, various clays, and other inorganic powders or PMMA ( (Polymethyl methacrylate), polyurethane, melamine resin, and other polymer powders such as crosslinked or uncrosslinked organic fine particles, and may be hollow particles, porous particles, composite particles, and the like. For example, as shown in FIG. 4, two or more types of inner surface scatterers 12 (12a, 12b) may be appropriately dispersed in the radiation curable resin (medium) 11 to form the diffusion layer 9. The content of the inner surface scatterer 12 in the diffusion layer 9 is preferably 3% to 50% by mass.

  The optical film 10 having the diffusion layer 9 composed of the radiation curable resin 11 and the inner surface scatterer 12 is obtained by mixing a mixed solution (coating solution) obtained by mixing the radiation curable resin 11 and the inner surface scatterer 12 with a plastic substrate. One surface 8a of the film 8 is applied by a conventional coating method such as a die coater, spin coater, roll coater, curtain coater, screen printing, etc., and after drying, irradiated with radiation such as EB (Electron Beam) or ultraviolet rays. It is formed by curing.

  In the present embodiment, the diffusion layer 9 is formed so that the thickness d1 thereof is 2 to 30 μm, as shown in FIG. The optical film 10 thus formed has a pencil hardness of 2H or more at a load of 500 g (4.9 N) based on a pencil hardness test (JIS K 5600-5-4), and is reliably provided with a hard coat property. Is done. The optical film 10 is preferably formed with a pencil hardness of 3H or higher, or 4H or higher.

Furthermore, the optical film 10 of the present embodiment is used by being arranged on the viewer side of the liquid crystal display device A (the front A1 side on which an image is displayed). Further, the colors near the eight test colors defined by CIE (International Lighting Commission) 1974 are displayed on the liquid crystal display device A as test colors, and are observed in a state of facing the front surface A1 of the liquid crystal display device A ( With the chromaticity coordinates (u ₀ ′, v ₀ ′) of CIE 1976 UCS (Uniform Color Space) (observed from the direction of arrow T1 in FIG. 3) and the observation angle θ changed ± 60 degrees horizontally or vertically. It is formed so that the color difference Δu′v ′ obtained by the following expression is within 0.05 from the observed chromaticity coordinates (u ′, v ′) of CIE1976UCS (observed from the direction of arrow T2 in FIG. 3). Have
Δu′v ′ = {(u′−u ₀ ′) ² + (v′−v ₀ ′) ² } ^0.5

  Next, functions and effects of the optical film 10 having the above-described configuration, the polarizing plate 4 including the optical film 10 and the liquid crystal display device A will be described.

  Here, when viewing a liquid crystal television (liquid crystal display device A), it is generally recommended to view in a bright room. At this time, in order to sufficiently secure the contrast in the bright room of the liquid crystal display device A, since the sensitivity to the dark part of the image displayed on the liquid crystal display device A is less than that in the dark room, the contrast is 100: It may be set to 1 (white luminance: black luminance) or more.

  In addition, in the conventional VA liquid crystal display device, the orientation of liquid crystal molecules looks different when viewed from the front and when viewed from an oblique direction, so that the gamma becomes smaller and the color becomes light when viewed from an oblique direction. When the color difference Δu′v ′ is about 0.10, the color appears to change greatly. Furthermore, there was a tendency to look blue when viewed from the front and yellow when viewed from the side. On the other hand, in order to correct this color change, a retardation film (a film having a biaxial refractive index anisotropy) is arranged. Even when this retardation film is used, a specific film is used. There is a problem that an effect is obtained only in the orientation, that is, in a black state, and a sufficient effect cannot be obtained for correction of the intermediate gradation.

  On the other hand, in this embodiment, the optical film 10 is provided on the polarizing layer 6 of one polarizing plate 4, that is, provided on the front (front) A1 side of the liquid crystal panel 1 (liquid crystal display device A). Therefore, the light (visible light) irradiated from the backlight 2 and sequentially transmitted through the other polarizing plate 5, the liquid crystal cell 3, and the one polarizing plate 4 is scattered (diffused) by the inner surface scatterer 12, and the viewing angle Thus, a liquid crystal display device having an image with little color change even when observed from the direction of the mark.

  Further, when the optical film 10 is used in the liquid crystal display device A, the color difference Δu′v ′ is formed so as to be within 0.05, so that even when an image is viewed from an oblique direction. Since the color difference of the image when viewed from the front A1 is small, it is possible to suppress color change and gradation change depending on the viewing direction. At this time, the diffusion layer 9 of the optical film 10 is formed so as to more strongly (selectively) scatter (Mie scattering) light having a short wavelength in the wavelength range of visible light transmitted through the diffusion layer 9. In other words, since it is formed so that more light with a short wavelength is scattered, it becomes possible to surely eliminate the color change with respect to blue having a short wavelength (400 nm to 500 nm) in the middle gradation. The color change and black float of the liquid crystal panel 1 are surely reduced, and the glare of the screen is suppressed.

  Furthermore, it is virtually impossible to measure all colors when measuring the color change. In this way, colors in the vicinity of 8 test colors defined in CIE1974 are used, that is, representative colors are used. By using the optical film 10 and the polarizing plate 4 having the optical film 10 and the liquid crystal display device A, the evaluation can be performed efficiently and with high reliability, and high quality without any color change is ensured. The optical film 10, the polarizing plate 4 including the optical film 10, and the liquid crystal display device A can be obtained.

  Further, the optical film 10 is formed such that the thickness d1 of the diffusion layer 9 is 2 to 30 μm, so that the light transmitted through the diffusion layer 9 in different directions can be sufficiently mixed and diffused. Thus, the color correction can be reliably performed by the effect of the wavelength dependency of the diffusion. Further, since the thickness d1 of the diffusion layer 9 is 2 to 30 μm, it can surely have a pencil hardness of 2H or more, a sufficient hard coat property is imparted, and the front surface of the liquid crystal display device A (most Even if it is disposed on the surface (A1), the liquid crystal display device A can be reliably secured without being easily damaged. Thereby, since it is possible to impart hard coat properties to one optical film 10 in addition to the effect of suppressing color change, it is not necessary to separately provide an optical element or a hard coat layer for color correction. It is possible to suppress an increase in cost due to an increase in the manufacturing process of the member. Moreover, the optical film 10 can be used in the form which serves as the protective film of the polarizing plate 4 of outermost surface A1.

  Furthermore, since the diffusion layer 9 is configured by dispersing and arranging the inner surface scatterers 12 in the radiation curable resin 11, the light transmitted through the diffusion layer 9 can be reliably scattered and the diffusion layer 9 can also be scattered. 9 can be cured by a simple method of irradiating with radiation at a stage where a mixed liquid in which the radiation curable resin 11 and the inner surface scatterer 12 are mixed is applied onto the plastic substrate film 8. It becomes possible to form the diffusion layer 9 in which the inner scatterers 12 are dispersedly arranged.

  Therefore, by applying the optical film 10 according to the present invention to the liquid crystal display device A having the vertical alignment type liquid crystal cell 3, the expressive power and low cost of the dark portion of the liquid crystal display device A such as a VA liquid crystal television. In the state where the features such as the above are maintained, it is possible to improve the gradation characteristics and to perform a suitable color correction with a wide diffusion angle while suppressing a decrease in contrast and luminance.

  In addition, this invention is not limited to said 1st Embodiment, In the range which does not deviate from the meaning, it can change suitably. For example, by using the optical film 10 and the polarizing plate 4 of the present embodiment, the liquid crystal display device A having no color change can be obtained by forming the color difference Δu′v ′ within 0.05. However, when more strict quality is required, it is desirable that the color difference Δu′v ′ be 0.04 or less. Further, when the optical film 10 of the present embodiment is added, there is a possibility that the brightness of the front surface A1 may be reduced, and this can be corrected by the backlight 2, but if it is extremely reduced, the backlight 2 In this case, the correction cannot be performed. Therefore, it is desirable to keep the brightness within 30% of that before adding the optical film 10, and more desirably within 20%. Further, white defined by JISZ8721 has a V of 8.5 or 9.0 or more, which is about 30% or less in terms of luminance reduction. That is, if it is 30% or less of the original luminance, it can be defined as white of the same color.

  In the present embodiment, the diffusion layer 9 of the optical film 10 is composed of the radiation curable resin 11 and the inner surface scatterer (particle) 12. However, the inner surface scatterer needs to be a particulate material. For example, the inner surface of the diffusion layer 9 is mixed with the radiation curable resin 11 so that the liquid inner scatterer 12 is dispersed, and this mixed solution is applied onto the plastic substrate film 8 and cured. You may make it form the fine area | region where the refractive index which consists of the scatterer 12 differs. In this case, the inner surface scatterer 12 does not need to be formed in a particle shape, that is, in a spherical shape, and a short wavelength in the wavelength range of visible light is more strongly scattered (Mie scattering) depending on the size (average diameter). It will be. In addition to this, the medium 11 in which the inner scatterer 12 is dispersedly arranged need not be limited to the radiation curable resin, and may be another substance as long as it has transparency.

  Furthermore, in this embodiment, although the optical film 10 shall comprise a part of polarizing plate 4, this optical film 10 may be used separately from a polarizing plate. In this embodiment, the optical film 10 (polarizing plate 4) is provided in the VA type liquid crystal display device A. However, the optical film 10 and the polarizing plate 4 according to the present invention are, for example, a TN type liquid crystal. It may be applied to a display device.

  Furthermore, the optical film 10 and the polarizing plate 4 may be formed with an antifouling layer and an antistatic layer. Further, an anti-fouling property may be imparted by adding an additive to the coating liquid at the stage of forming the diffusion layer 9. Examples of such additives include silicone-based and fluorine-based surfactants.

  In the present embodiment, the inner surface scatterer 12 has a refractive index different from the light refractive index of the radiation curable resin 11, so that the wavelength of visible light depends on the particle diameter (size) of the inner surface scatterer 12. In the range, the short wavelength is more strongly scattered (Mie scattering), the backscattering is less, and the light is scattered in a wide range (Mie scattering). How much light is not scattered is defined by the scattering cross section, which is defined in proportion to the particle size of the inner scatterer 12 and the scattering factor.

  Here, FIG. 5 shows a case in which light having a wavelength of 550 nm is irradiated onto a diffusion layer 9 composed of a radiation curable resin (medium) 11 having a refractive index of 1.5 and an inner scatterer 12 having a refractive index of 1.6. The relationship between the particle diameter of the inner scatterer 12 and the scattering efficiency / ratio is shown. From this figure, when the particle size is 0.1 μm to 0.2 μm, it is confirmed that the backscattering increases rapidly, and when a large amount of such an inner scatterer having such a small particle size that rapidly increases the backscattering is contained. In this case, the contrast of the image is lowered.

  FIG. 6 shows the relationship between the particle diameter of the inner surface scatterer 12 and the scattering efficiency when irradiated with light of different wavelengths. From this figure, when the particle diameter is larger than 3 μm, the short wavelength It is confirmed that not only the light but also the whole range of wavelengths are scattered, and if many such inner scatterers 12 having a particle diameter larger than 3 μm are included, the luminance and the sharpness are lowered.

  Furthermore, FIG. 7 shows the relationship between the scattering angle and the relative scattering intensity for the inner surface scatterer 12 having different particle diameters. From this figure, it is confirmed that the scattering angle decreases as the particle diameter increases. It is confirmed that the effect of gradation and color correction is enhanced by including many inner scatterers 12 having a small particle diameter.

  Therefore, the inner surface scatterer 12 has a particle diameter (size) of 0.5 to 3.0 μm, thereby more reliably scattering light in the short wavelength region and increasing the scattering angle. It is possible to enhance the effect of tone and color correction.

  FIG. 8 shows the relationship between the refractive index difference between the inner surface scatterer 12 having a particle diameter of 0.5 μm and the medium 11 and the scattering efficiency. From this figure, the refractive index difference is 0.05 or less. It is confirmed that the total scattering factor becomes extremely small, and when the refractive index difference becomes 0.6 to 0.8 or more, it is confirmed that the backscattering increases rapidly. For this reason, when the refractive index difference is 0.05 or less, the light diffusion effect by the diffusion layer 9 cannot be obtained, and when the refractive index difference is 0.6 to 0.8 or more, the contrast of the image is low. Will be reduced. Therefore, by setting the difference in refractive index between the inner scatterer 12 and the medium 11 to 0.05 to 0.6, the viewing angle can be more reliably expanded and the reduction in the contrast of the image is suppressed. Is possible.

  Further, as shown in FIG. 9, the optical film 20 of the present embodiment has an inner surface scatterer 12 protruding partly on the surface 9a of the diffusion layer 9 (front surface and front surface of the polarizing plate and the liquid crystal display device). It may be formed. Thereby, the surface 9a of the diffusion layer 9 is formed in an uneven shape.

  In the optical film 20 configured in this manner, due to the unevenness of the surface 9a of the diffusion layer 9, even when the surface 9a is irradiated with, for example, external light, the external light is reflected and the polarizing plate 4 and the optical film 20 are formed. It is possible to prevent the visibility of transmitted light from being lowered. That is, by forming the surface 9a of the diffusion layer 9 in a concavo-convex shape, the antiglare property can be greatly improved.

  In addition to forming the surface 9a of the diffusion layer 9 in a concavo-convex shape by causing a part of the inner surface scatterer 12 to protrude outward from the surface 9a of the diffusion layer 9, for example, as shown in FIG. Further, together with the inner surface scatterer 12, the optical film 20 is formed by separately including the irregularity-forming particles 21 mixed so as to protrude outward from the surface 9 a of the diffusion layer 9 and forming the surface 9 a in an irregular shape. Also good. The unevenness-forming particles 21 are, for example, powdered glass, glass beads, finely pulverized glass fibers, titanium oxide, calcium carbonate, silicon dioxide (silica), aluminum oxide, various clays, or other inorganic powders or PMMA (polymethyl methacrylate). Resin powders such as crosslinked or uncrosslinked organic fine particles composed of various polymers such as polyurethane and melamine resin, and may be hollow particles, porous particles, composite particles, etc., and two or more kinds of unevenness forming particles as appropriate 21 may be used. Furthermore, when using such uneven | corrugated particle | grains 21, it is preferable to mix the uneven | corrugated particle | grains 21 about 2-50 mass parts with respect to 100 mass parts of transparent resin (medium 11), and 5-25. It is more preferable to set it as a mass part. And even when it has such uneven | corrugated particle | grains 21, anti-glare property can be improved similarly to this embodiment. Moreover, the inner surface scatterer 12 may be protruded from the surface 9a together with the unevenness forming particles 21, and the surface 9a may be formed in an uneven shape by using these particles 12 and 21 together.

  In addition to improving the antiglare property by causing the inner surface scatterer 12 and the unevenness forming particles 21 to protrude outward from the surface 9a, as shown in FIG. 11, the surface of the optical film 20 (the surface 9a of the diffusion layer 9). May be formed in an uneven shape by embossing. That is, the antiglare property can also be improved by applying the antiglare treatment to form the uneven surface 9a.

  Examples of the present invention will be specifically described below. However, the present invention is not limited to this embodiment.

  In this embodiment, the optical film (optical element) 10 according to the present invention is defined by CIE (International Lighting Commission) 1974 as a test color in a state in which the liquid crystal display device A is provided and a state in which the liquid crystal display device A is not provided. Using the colors in the vicinity of the eight test colors, the chromaticity coordinates shown in CIE 1976 UCS are directly opposed to the front (front) A1 of the liquid crystal display device A, and the observation angle in the horizontal or vertical direction with respect to the front A1. The optical film 10 according to the present invention, the polarizing plate 4 having the same, and the liquid crystal display device are obtained by measuring θ in a state changed by ± 60 degrees and obtaining the color difference Δu′v ′ obtained from these chromaticity coordinates. This shows the superiority of A.

In this example, the refractive index is 1.52-1 for the mixed solution obtained by adding Seahoster P100 (made by Nippon Shokubai Co., Ltd.) (inner surface scatterer 12) having a refractive index of 1.42 to methyl ethyl ketone so as to be 30 wt%. Add BYK-P105 (by Big Chemie Japan Co., Ltd.) to a clear resin solution of 53 UV curable resin 11 (Daiichi Seika Kogyo Co., Ltd., Seika Beam EXF37T) so that the mass ratio is 2: 0.07 The mixed liquid was mixed at a mass ratio of 1: 2 to prepare a coating liquid. Then, using a Gap 75 μm applicator, this coating solution is applied to a TAC film (80 μm thickness) manufactured by Fuji Photo Film Co., Ltd., the solvent is volatilized by heating, and ultraviolet rays are irradiated at about 500 mJ / cm ^2. To form a diffusion layer 9 and an optical film 10. At this time, the content of the inner surface scatterer 12 in the diffusion layer 9 is about 23% by mass ratio. Furthermore, the optical film 10 thus formed had a pencil hardness of 3H. Furthermore, the antiglare property was confirmed.

  And when this optical film 10 is bonded to the front (front surface, surface) A1 of VA type liquid crystal television (manufactured by Sharp Corporation, LC-20SA-S) A, the scattering property and color difference Δu′v ′ are confirmed. It was confirmed that sufficient scattering properties could be obtained, and the color difference Δu′v ′ was 0.05, and it was confirmed that the color change could be suppressed. On the other hand, the color difference Δu′v ′ when the optical film 10 was not bonded was 0.10. Moreover, the brightness | luminance reduction by bonding an optical film was 13%.

  Therefore, it was proved that by bonding the optical film 10 according to the present invention to the liquid crystal display device A, it is possible to obtain a liquid crystal display device in which color change does not occur depending on the viewing direction while suppressing a decrease in front luminance.

It is a figure which shows the liquid crystal display device which concerns on 1st Embodiment of this invention. It is a figure which shows the polarizing plate which concerns on 1st Embodiment of this invention. It is a figure which shows the optical element which concerns on 1st Embodiment of this invention. It is a figure which shows the modification of the optical element which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the particle diameter of an inner surface scatterer, and scattering efficiency and ratio. It is a figure which shows the relationship between the particle diameter of the inner surface scatterer with respect to the wavelength of different light, and scattering efficiency. It is a figure which shows the relationship between the scattering angle with respect to the inner surface scatterer of a different particle diameter, and relative scattering intensity. It is a figure which shows the relationship between the refractive index difference of an internal surface scatterer and a medium, and scattering efficiency. It is a figure which shows the optical element which concerns on 2nd Embodiment of this invention. It is a figure which shows the modification of the optical element which concerns on 2nd Embodiment of this invention. It is a figure which shows the modification of the optical element which concerns on 2nd Embodiment of this invention.

Explanation of symbols

1 liquid crystal panel 2 backlight 3 liquid crystal cell 4 polarizing plate (one polarizing plate)
4a Front 5 Polarizer (the other polarizer)
5a Back 6 Polarizing layer 7 Plastic base film 8 Plastic base film 8a One side 8b The other side 9 Diffusion layer 10 Optical element (optical film)
11 Radiation curable resin (medium)
12 Inner scatterer 20 Optical element (optical film)
21 Concavity and convexity forming particles A Liquid crystal display device A1 Front (front)
θ Observation angle d1 Diffusion layer thickness

Claims (12)

A diffusion layer for scattering light to be transmitted is formed on at least one surface of a plastic substrate film, and is an optical element used by being arranged on the front side for displaying an image of a liquid crystal display device,
The diffusion layer is formed with an inner surface scatterer having a refractive index different from the refractive index of the medium that selectively scatters a short wavelength in the visible light wavelength range (Mie scattering). In addition, the pencil hardness at 500 g load (4.9 N) is 2H or more,
When the liquid crystal display device is arranged and used on the front side for displaying an image, the liquid crystal display device displays colors in the vicinity of 8 test colors defined by CIE1974 as test colors. CIE 1976 UCS chromaticity coordinates (u ₀ ′, v ₀ ′) observed in front of the front, and CIE 1976 UCS chromaticity observed with the observation angle changed ± 60 degrees horizontally or vertically An optical element characterized in that the color difference Δu′v ′ obtained from the coordinates (u ′, v ′) by the following formula is within 0.05.
Δu′v ′ = {(u′−u ₀ ′) ² + (v′−v ₀ ′) ² } ^0.5 The optical element according to claim 1, wherein
An optical element having a thickness of the diffusion layer of 2 to 30 μm. The optical element according to claim 1 or 2,
The optical element, wherein the diffusion layer is formed by dispersing and disposing the inner scatterer in a radiation curable resin of the medium. The optical element according to any one of claims 1 to 3,
An optical element having a size (average diameter) of the inner surface scatterer of 0.2 to 3 μm. The optical element according to any one of claims 1 to 4,
An optical element, wherein a refractive index difference between the medium and the inner scatterer is 0.05 to 0.6. The optical element according to any one of claims 1 to 5,
The optical element, wherein the inner scatterer is a particle. The optical element according to any one of claims 1 to 6,
An optical element, wherein the surface of the diffusion layer is formed in an uneven shape. The optical element according to claim 7.
An optical element characterized in that a part of the irregularity-forming particles mixed in the medium of the inner surface scatterer and / or the diffusion layer protrudes outward and the surface is formed in an irregular shape. The optical element according to claim 7.
An optical element, wherein the surface of the diffusion layer is formed in an uneven shape by embossing. The optical element according to any one of claims 1 to 9,
An optical element, wherein the liquid crystal display device comprises a vertical alignment type liquid crystal cell.   A polarizing plate comprising the optical element according to any one of claims 1 to 10 disposed on a polarizing layer. 12. A liquid crystal display device comprising: the polarizing plate according to claim 11 disposed on a front side displaying an image of the liquid crystal display device.

Images