JP2008083294A - Diffuser, and diffusion film, polarizing plate, and liquid crystal image display device provided with diffuser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffuser with which occurrence of color change, gray scale change etc. caused by change in the angle of observation is suppressed, and a diffusion film, a polarizing plate, and a liquid crystal image display device provided with the diffuser. <P>SOLUTION: The diffuser 10 is used in the liquid crystal image display device A equipped with a vertical alignment mode liquid crystal panel 1, and is arranged on the front face A1 side to display the image of the liquid crystal panel 1 for the purpose of suppressing the color fluctuation of the image, occurring in the case of changing the angle of observation from the front face A1 side, and is equipped with diffusion characteristics of diffusing 10% or more light S into an angular range θ1 of 35-55° with respect to a front face direction T and diffusing 7% or less light S into an angular range θ2 of 60-90° with respect to the front face direction T, when the light S of parallel beams made incident in the front face direction T normal to the front face A1 is transmitted through the diffuser. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a diffuser capable of suppressing a decrease in luminance of a liquid crystal image display device by scattering (diffusing) light and forming a liquid crystal image display device with little color change due to a difference in viewing angle, and the same. The present invention relates to a diffusion film, a polarizing film, and a liquid crystal image display device.

  2. Description of the Related Art Conventionally, a liquid crystal image display device provided in, for example, a liquid crystal television, a car navigation system, a personal computer monitor, 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. ing. 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 for displaying an image of a liquid crystal image display device ( An RGB color filter interposed between one liquid crystal cell substrate arranged on the front side) and a pair of polarizing plates arranged so as to sandwich the liquid crystal cell and transmitting only light in one direction of vibration. It is prepared for.

  In addition, this type of liquid crystal image 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. Type, OCB (Optically Compensated Bend) type, etc. Among these, in the TN type liquid crystal image display device, liquid crystal molecules are twisted and arranged at 90 degrees (twisted orientation) about a direction perpendicular to the substrate in a state where no voltage is applied. The light irradiated from the light and transmitted through the other polarizing plate (incident light) travels along the twisted arrangement of liquid crystal molecules, so that the direction of vibration changes to the same direction as the transmission axis of one polarizing plate. It passes through one polarizing plate. 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 type liquid crystal image display device, the alignment of the liquid crystal molecules is aligned in one vertical direction when a voltage is applied, so that the vertical light is completely blocked, but the oblique light is not blocked. Will leak. 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). ). 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, even in this VA type liquid crystal display device, there is a problem that the gamma (gradation characteristics) 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. there were. In addition, even when a retardation film is applied to the 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 image 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, the black film 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 tone reversal 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 image 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 the oblique direction is focused in the front direction. By averaging the light rays, a liquid crystal image display device with high viewing angle characteristics and high resistance to gradation inversion and color tone change is obtained.
Japanese Patent Laid-Open No. 10-10513 JP 20044763 A

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

  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.

  Therefore, the present invention has been made in view of the above circumstances, and color changes and gradation changes occur depending on the viewing angle with respect to a liquid crystal image display device, particularly a liquid crystal image display device such as a VA type liquid crystal television. It is an object of the present invention to provide a diffuser capable of suppressing the above, a diffusion film and a polarizing film including the same, and a liquid crystal image display device.

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

  The diffuser of the present invention is used in a liquid crystal image display device including a vertical alignment type liquid crystal panel, and is disposed on the front side that displays an image of the liquid crystal panel, and changes the observation angle from the front side. A diffuser for suppressing the color change of the generated image, and when parallel light beams incident in a front direction orthogonal to the front surface are transmitted, 10% or more of the light is 35 in the front direction. It is characterized in that it has a diffusion characteristic that diffuses in an angle range of ˜55 °, and that 7% or less of the light diffuses in an angle range of 60˜90 degrees with respect to the front direction.

  In addition, the diffusion film of the present invention is a diffusion film that is disposed on the front side that displays an image of a vertically aligned liquid crystal panel and diffuses light incident on the liquid crystal panel. It is characterized by being provided with the above diffuser.

  Furthermore, the polarizing film of the present invention is a polarizing film that is disposed on the front side that displays an image of a vertically aligned liquid crystal panel and polarizes light incident on the liquid crystal panel, and displays the image. The diffuser is provided on the front side.

  In addition, a liquid crystal image display device according to the present invention is a liquid crystal image display device including a vertical alignment type liquid crystal panel, and includes the above-described diffuser on the front side displaying an image of the liquid crystal panel.

  According to the diffusing body, the diffusing film, the polarizing film, and the liquid crystal image display device of the present invention, the diffusing body has an angle range of 35 to 55 degrees with respect to the front direction when incident light of parallel rays is transmitted. By providing a diffusion characteristic in which more than% of incident light diffuses, it is possible to suppress a color change even when an image is viewed from different observation angles. Further, by providing diffusion characteristics in which incident light of 7% or less diffuses in an angle range of 60 degrees to 90 degrees with respect to the front direction, it is possible to suppress a decrease in the front luminance of the image. Therefore, according to the present invention, it is possible to provide a liquid crystal image display device capable of displaying a clear image from any place.

  Hereinafter, a diffuser according to an embodiment of the present invention, a diffusion film including the same, a polarizing film, and a liquid crystal image display device will be described with reference to FIGS. The present embodiment relates to a liquid crystal image 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, a diffuser that suppresses a color change and a gradation change depending on a viewing angle, and a diffusion including the diffuser The present invention relates to a film, a polarizing film, and a liquid crystal image display device.

  The liquid crystal image display apparatus A of the present embodiment includes a liquid crystal panel 1 and a backlight 2 that irradiates the liquid crystal panel 1 with light (incident light) S. The liquid crystal panel 1 is shown in FIG. The polarizing films 4 and 5 are laminated and arranged so that the liquid crystal cell 3 is sandwiched between both surfaces of the flat VA liquid crystal cell 3. And this liquid crystal panel 1 arrange | positions the front surface 4a of one polarizing film 4 to the front (front surface) A1 side of the liquid crystal image display apparatus A, and the other polarizing film 5, The backlight 2 is arranged so as to transmit the parallel light S in the order of the liquid crystal cell 6 and the one polarizing film 4.

  Among the pair of polarizing films 4 and 5, the one polarizing film 4 is formed by sandwiching a polarizing layer 7 between a transparent plastic base film 8 and a plastic base film 9, and the liquid crystal display device A. On one surface 8a of the plastic base film 8 disposed on the front surface A1 side, a diffuser 10 formed by dispersing and arranging the inner surface scatterers 10a is laminated. Here, in this embodiment, the diffusion film 11 is comprised by the diffuser 10 which is a component of one polarizing film 4, and the plastic base film 8 on which this diffuser 10 is laminated | stacked. On the other hand, the other polarizing film 5 is formed by sandwiching a polarizing layer 7 between two plastic base films 8 and 9.

  The diffuser 10 of the present invention is provided on the front A1 side of the polarizing layer 7 sandwiched between the plastic base film 8 and the plastic base film 9 on the front (front) A1 side of the liquid crystal display device. In the embodiment of FIG. 1, the diffusion film 11 constitutes a part of the polarizing film 4, but the diffusion film 11 may be used separately from the polarizing film 4.

  The plastic substrate films 8 and 9 of the diffusion film (polarizing films 4 and 5) 11 are, for example, a triacetyl cellulose (TAC) film, a polyethylene terephthalate (PET) film, a cycloolefin-based film, and the like, and a transparent plastic substrate. If it is a film, it is not necessary to limit the material in particular.

  On the other hand, in this embodiment, as shown in FIG. 1, the diffuser 10 is formed by dispersely arranging inner surface scatterers (particles) 10a in a radiation curable resin (medium) 10b. Here, the inner surface scatterer 10b has a refractive index different from the refractive index of the light S of the radiation curable resin 10b, and the inner surface scatterer 10a is dispersedly arranged in the radiation curable resin 10b. In the diffuser 10, a plurality of fine regions having different refractive indexes made of the inner scatterer 10a are formed. The inner surface scatterer 10a scatters the light S irradiated from the backlight 2 and transmitted through the diffuser 10 (Mie scattering). The inner surface scatterer 10a may be uniformly distributed in the radiation curable resin 10b (in the diffuser 10) or may be unevenly distributed.

  The radiation curable resin 10b is preferably a resin having an acrylate functional group, more preferably a polyester acrylate or a 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 10b 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.

  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 10a 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, or 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. Alternatively, the diffuser 10 may be formed by appropriately dispersing two or more types of inner surface scatterers 10a in the radiation curable resin 10b.

  The diffusion film 11 provided with the diffuser 10 composed of the radiation curable resin 10b and the inner scatterer 10a is obtained by mixing a mixed solution (coating solution) obtained by mixing the radiation curable resin 10b and the inner scatterer 10a with the plastic substrate film 8. For example, a die coater, a spin coater, a roll coater, a curtain coater, a screen coater, or the like is applied to the one surface 8a, and after drying, it is cured by irradiation with radiation such as EB (Electron Beam) or ultraviolet rays. Formed.

  And the diffuser 10 of this embodiment formed in this way is 10% or more when the light S of the parallel rays incident in the front direction T perpendicular to the front surface A1 is transmitted as shown in FIG. The light S is diffused in an angle range θ1 of 35 ° to 55 ° with respect to the front direction T, and 7% or less of the light S is diffused in an angle range θ2 of 60 ° to 90 ° with respect to the front direction T. Is formed.

  Next, functions and effects of the diffuser 10 having the above-described configuration, the diffusion film 11 and the polarizing film 4 including the same, and the liquid crystal display device A will be described.

  Here, generally, in the same manner as in the present embodiment, when the diffuser (diffusion film 11) 10 is provided on the front surface A1 side (observer side) of the liquid crystal panel 1, the light of parallel rays irradiated from the backlight 2 is used. S is transmitted through the other polarizing film 5, the liquid crystal cell 3, and the one polarizing film 4 in this order and emitted from the front surface A 1 to the outside. At this time, the diffuser 10 of the one polarizing film (diffusion film 11) 4 A part of the light S is diffused and emitted in an oblique direction with respect to the front direction T. Thereby, the image displayed on the screen of the liquid crystal display device A is displayed by the averaged light S.

However, simply providing a diffuser cannot effectively suppress the color change, and the suppression of the color change is achieved by providing a diffuser having appropriate diffusion characteristics. That is, diffusers having different diffusion characteristics are provided, and eight test colors defined by the CIE (International Lighting Commission) 1974 are displayed as test colors on the liquid crystal display device, and are displayed on the front surface A1 of the liquid crystal display device. CIE1976UCS (Uniform Color Space) chromaticity coordinates (u ₀ ′, v ₀ ′) observed in the frontal direction T facing the CIE 1976UCS color observed at an angle from the frontal direction T (oblique direction) When the color difference (magnitude of color change) Δu′v ′ at different observation angles is obtained from the degree coordinates (u ₁ ′, v ₁ ′) by the following equation:
Δu′v ′ = {(u ₁ ′ −u ₀ ′) ² + (v ₁ ′ −v ₀ ′) ² } ^0.5
As shown in FIG. 2, due to the difference in diffusion characteristics of the diffuser, a large color change occurs depending on the difference in color difference Δu′v ′ of 0.09 at the maximum, that is, the viewing angle.

  FIG. 3 shows the results of measuring diffused light intensity in different observation angle directions by installing diffusers A to E having different diffusion characteristics, and Table 1 shows each diffuser A to E installed. The maximum value of the color difference Δu′v ′ and the reduction rate of the front luminance are shown. From this result, in the diffuser A where the diffusion angle of the diffusing light S is small and the diffusion angle is only about 20 degrees or less, the effect of suppressing the color change is hardly obtained (the color difference Δu′v ′ is large). It is also confirmed that the color difference Δu′v ′ is smaller in the diffuser D having a smaller diffusion angle than the diffuser E in which the diffused light spreads over the widest range. Thereby, it can be confirmed that the diffuser not only diffuses the diffused light in a wide range but also strongly diffuses in an appropriate direction in order to suppress the color change. Further, from the results of FIG. 3 and Table 1, it is recognized that the color difference Δu′v ′ tends to be smaller as the diffuser has a larger diffused light intensity near the diffusion angle of 45 degrees.

  FIG. 4 shows a plurality of diffusers F to J in which the maximum value of the color difference Δu′v ′ at a diffusion angle of 45 degrees is about 0.045 (0.046 to 0.047), that is, the color change can be suppressed. The result of having extracted and diffusing body FJ each and having measured the diffused light intensity in the diagonal direction when the light S of the parallel ray of the front direction T injects is shown. From this result, it is recognized that the spreading method of the diffused light is greatly different depending on each of the diffusers F to J. However, it is recognized that the diffused light intensity is almost equal in the vicinity of the diffusion angle of 45 degrees. Has been confirmed to have a great influence on the suppression of color change.

  On the other hand, in general, when a diffuser is provided, there arises a problem that the front luminance of the displayed image is lowered. Table 2 shows a case where a plurality of diffusers FJ each having a maximum color difference Δu′v ′ of about 0.045 (0.046 to 0.047) at a diffusion angle of 45 degrees shown in FIG. 4 are provided. The color difference Δu′v ′ and the front luminance reduction rate are shown. From these FIG. 4 and Table 2, the diffuser having a larger spread of diffused light has a greater reduction in frontal luminance, and particularly has a large diffused light intensity in a range of 60 degrees or more (how to spread to a range of 60 degrees or greater). It was confirmed that the larger the diffuser E), the more severe the brightness decrease.

  On the other hand, FIG. 5 shows the diffused light intensity with respect to the observation angles of a plurality of diffusers K to N that have different color differences Δu′v ′ but exhibit the same degree of decrease in luminance at about 20%. From this result, it can be confirmed that the diffused light intensity is greatly different in the vicinity of the diffusion angle of 45 degrees, but the diffused light intensity of 60 degrees or more is almost the same. It was confirmed that the intensity of diffused light greatly affected.

  Here, there are two possible causes for the decrease in the front luminance due to the provision of the diffuser. First, a liquid crystal image display device such as a liquid crystal television generally concentrates (collects) the light S in the front direction T. When the spread of the light S is increased by the diffuser, the light S that circulates in the lateral direction increases, thereby causing a reduction in front luminance. As another cause, as shown in FIG. 6, a part of the light S diffused by the diffuser is diffused at a large diffusion angle, and becomes larger than the total reflection angle with respect to the surface (front surface A1). In other words, it is reflected by the surface A1 and is not emitted to the outside, and the front luminance is lowered due to the presence of such diffused light.

  For these reasons, there is strong diffused light near a diffusion angle of 45 degrees, and a diffuser having a diffusion characteristic that reduces diffused light in a direction of 60 degrees or more reduces the front luminance. Therefore, it is judged that the color change due to the difference in the observation angle can be efficiently suppressed.

  Next, the intensity of the diffused light with a diffused angle in the vicinity of 45 degrees and diffused light in the direction of 60 degrees or more is reduced to reduce the front luminance, and the color change due to the difference in viewing angle is efficient. To obtain a diffuser that can be effectively controlled.

  Here, as shown in FIG. 2 described above, in a liquid crystal image display device having a general VA type liquid crystal panel, eight test colors defined by CIE1974 are displayed on the liquid crystal image display device as test colors. Since the measured color difference (color change magnitude) Δu′v ′ is 0.09 at the maximum, the color difference (color change magnitude is about 0.045 (0.046 to 0.047), which is about half of this. FIG. 7 shows the results of measuring the ratio of diffused light with respect to the observation angle for the diffusers F to J shown in FIG. 4 having Δu′v ′. Table 3 shows the ratio of diffused light that diffuses in the range where the observation angle θ1 of each of the diffusers F to J is 35 degrees to 55 degrees.

  From these results, the diffusers F to J, which have a color difference Δu′v ′ of about 0.045 and can suppress the color change, show some variation, but the observation angle of 35 to 55 degrees out of the total diffused light. It was confirmed that the diffused light diffused in the range of about 10 to 12%. As a result, the diffusion body (the diffusion body 10 of the present embodiment) has diffusion characteristics that diffuse 10% or more of the diffusion light with respect to the total diffusion light in the observation angle range of 35 to 55 degrees. On the other hand, it was confirmed that an effective color change suppression performance that reduces the color change to half or less is provided.

  On the other hand, FIG. 8 shows a ratio of diffused light in an oblique direction in the diffusers O to R in which the front luminance reduction rate is about 30%. Table 4 shows the ratio of diffused light diffused in the range of observation angles of 60 degrees to 90 degrees with the respective diffusers O to R in FIG.

  From these results, when the diffuser has diffusion characteristics in which about 8% of the diffused light is diffused in the observation angle range of 60 to 90 degrees, the reduction rate of the front luminance is suppressed to about 30%. It was confirmed that the reduction rate of the front luminance can be reliably reduced to 30% or less by setting it to 7% or less.

  Therefore, based on the above results, in the diffuser 10 of the present embodiment shown in FIG. 1, the diffusion film 11 and the polarizing film 4 including the diffuser 10, and the liquid crystal image display device A, the diffuser 10 is in the front direction T. 10% or more of light S diffuses in an angle range θ1 of 35 ° to 55 °, and 7% or less of light S diffuses in an angle range θ2 of 60 ° to 90 °. As compared with the conventional liquid crystal image display device, although a slight decrease in front luminance of 30% or less occurs, the color change can be suppressed to be approximately half or less. Therefore, it is possible to obtain the liquid crystal image display apparatus A that allows a clear image to be observed from anywhere.

  In addition, this invention is not limited to said one Embodiment, In the range which does not deviate from the meaning, it can change suitably. For example, in this embodiment, the diffuser 10 of the diffusion film 11 is composed of the radiation curable resin 10b and the inner scatterer (particle) 10a. However, the inner scatterer 10a needs to be a particulate substance. For example, it may be formed by mixing with the radiation curable resin 10b so that the liquid inner surface scatterer is dispersed. In this case, the inner surface scatterer 10a does not need to be formed in a particle shape, that is, in a spherical shape, and the light S is scattered (Mie scattering) according to its size (average diameter). In addition to this, the medium in which the inner scatterer 10a is dispersedly arranged need not be limited to the radiation curable resin 10b, and may be another substance as long as it has transparency.

  The diffuser of this invention should just be provided in the front side rather than the polarizing layer provided in the front side of a liquid crystal display device. In the present embodiment, the diffusion film 11 constitutes a part of the polarizing film 4, but the diffusion film 11 may be used separately from the polarizing film 4.

  Next, Example 1 of the present invention will be specifically described below. However, the present invention is not limited to this embodiment.

  In this embodiment, 10% or more of light S diffuses in an angle range θ1 of 35 to 55 degrees with respect to the front direction T according to the present invention, and 7% or less of light S in an angle range θ2 of 60 to 90 degrees. It will be demonstrated with a specific example that the color change of the liquid crystal image display device A and the decrease in the front luminance can be suppressed by providing the diffuser 10 having the diffusion characteristic of diffusion.

  In this example, a vinyl acetate resin, a certain acrylic monomer, and an initiator for UV light are dissolved in methyl ethyl ketone (MEK), and these are coated on a TAC film (plastic base film 8). After exposure to light, the diffusion film 11 was formed by heating in an oven. In this embodiment, the diffuser 10 having a thickness of about 20 μm is formed by such a method.

  And the light S of the parallel light perpendicularly entered the diffused film 11 formed in this way, and the intensity of the diffused light emitted after transmission was measured using EZ Contrast manufactured by Eldim. FIG. 9 shows the diffused light intensity with respect to the diffusion angle measured as described above. FIG. 10 shows the result of obtaining the relationship between the observation angle and the light amount ratio based on the result of FIG. Based on the results of FIG. 9 and FIG. 10, the ratio of the light S in the angle range θ1 of the observation angle of 35 ° to 55 ° is determined to be about 11.2%, and the observation angle of 60 ° to 90 °. The ratio of the light S in the angle range θ2 was about 4%.

  Then, as shown in FIG. 1, such a diffusion film 11 is provided in the VA type liquid crystal panel 1 so that the screen of the liquid crystal display device A displays eight test colors defined by CIE1974 as test colors. When the color difference Δu′v ′ was obtained, the result of FIG. 11 was obtained. Note that the observation angle and the light amount ratio of a conventional liquid crystal panel (original liquid crystal panel) that does not include the diffuser of the present embodiment are as shown in FIG. 2 described above. In this original liquid crystal panel, the color difference Δu′v Whereas the maximum value of 'was about 0.09, when the diffusion film 11 of this example was provided, the maximum value of the color difference Δu'v' was about 0.046.

  In addition, the front luminance at this time is about 350 cd when the original liquid crystal panel is about 420 cd, and is provided with the diffusion film 11 of this embodiment, which can be suppressed by about 16% reduction in luminance. did it.

  Furthermore, when actually observing the image, it is possible to observe a good image that is almost unnoticeable, such as a change in color and gradation with respect to the viewing angle, and a decrease in luminance when viewed from the front A1. Met.

  Thereby, 10% or more of light S diffuses in an angle range θ1 of 35 to 55 degrees with respect to the front direction T, and 7% or less of light S diffuses in an angle range θ2 of 60 to 90 degrees. It was proved that the color change of the liquid crystal image display device A and the decrease in front luminance can be suppressed by providing the provided diffuser 10.

  Next, Example 2 of the present invention will be specifically described. However, the present invention is not limited to this embodiment.

  In the present embodiment, the color change of the liquid crystal display device A is achieved by providing the diffuser 10 formed by dispersing the filler (inner surface scatterer 10a) in which the conditions such as the particle diameter and the refractive index are arranged in the resin 10b. It demonstrates that a specific example can show that a front luminance fall can be suppressed.

  In this embodiment, for example, a silica filler 10a having a particle diameter of 1 μm is dispersed in an acrylic UV curable resin 10b, applied on the TAC film 8, and exposed to UV light to form the diffusion film 11. did. In this embodiment, the diffuser 10 having a thickness of about 20 μm is formed by such a method.

  Then, the intensity of the diffused light that was vertically incident on the diffused film 11 formed in this manner, and was transmitted through and emitted from the diffused film 11 was measured using EZContrast manufactured by Eldim. FIG. 12 shows the diffused light intensity with respect to the diffusion angle measured as described above. FIG. 13 shows the result of obtaining the relationship between the observation angle and the light amount ratio based on the result of FIG. Based on the results of FIGS. 12 and 13, the ratio of the light S in the angle range θ <b> 1 with an observation angle of 35 degrees to 55 degrees is calculated to be about 10.6%, and the observation angle is 60 degrees to 90 degrees. The ratio of the light S in the angle range θ2 was about 3.8%.

  Then, such a diffusion film 11 is provided in the VA liquid crystal panel 1 to display the eight test colors defined in CIE1974 as test colors on the screen of the liquid crystal display device A, and the color difference Δu′v ′ is displayed. As a result, the result of FIG. 14 was obtained, and it was confirmed that the maximum value of the color difference Δu′v ′ was about 0.045 by providing the diffusion film 11 of this example.

  Further, at this time, the front luminance is about 420 cd in the state where the diffuser 10 of the present example is not provided, whereas when the diffusion film 11 of the present example is provided, it is about 360 cd, which is about 14 % Brightness reduction.

  Further, as in Example 1, when actually observing the image, a good image that is almost unnoticeable, such as a change in color and gradation with respect to the viewing angle, and a decrease in luminance when viewed from the front. Was able to be observed.

  Thereby, also in the diffusion film (diffuser 10) 11 of this example, 10% or more of the light S is diffused in an angle range θ1 of 35 to 55 degrees with respect to the front direction T, and an angle of 60 to 90 degrees. It has been proved that the color change of the liquid crystal image display device A and the decrease in front luminance can be suppressed by providing diffusion characteristics in which 7% or less of light S diffuses in the range θ2.

It is a figure which shows the liquid crystal image display apparatus provided with the diffuser which concerns on one Embodiment of this invention. It is a figure which shows the color change with respect to the angle of the conventional liquid crystal image display apparatus. It is a figure which shows an example of the diffused light intensity with respect to the angle of a diffuser. It is a figure which shows an example of the diffused light intensity with respect to the angle of a diffuser. It is a figure which shows an example of the diffused light intensity with respect to the angle of a diffuser. It is a figure for demonstrating the cause of the front luminance fall by diffuser installation. It is a figure which shows an example of the ratio of the diffused light with respect to an angle. It is a figure which shows an example of the ratio of the diffused light with respect to an angle. It is a figure which shows an example of the diffused light intensity with respect to the angle of the diffuser which concerns on this invention. It is a figure which shows an example of the light quantity ratio with respect to the angle of the diffuser which concerns on this invention. It is a figure which shows an example of the color change with respect to the angle of the liquid crystal image display apparatus provided with the diffuser which concerns on this invention. It is a figure which shows an example of the diffused light intensity with respect to the angle of the diffuser which concerns on this invention. It is a figure which shows an example of the light quantity ratio with respect to the angle of the diffuser which concerns on this invention. It is a figure which shows an example of the color change with respect to the angle of the liquid crystal image display apparatus provided with the diffuser which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight 3 Liquid crystal cell 4 Polarizing film (one polarizing film)
5 Polarizing film (the other polarizing film)
7 Polarizing layer 8 Plastic base film 9 Plastic base film 10 Diffuser 10a Internal scattering body 10b Radiation curable resin (medium)
11 Diffusion film A LCD image display device A1 Front (front)
S light T front direction θ1 angle range θ2 angle range

Claims (4)

Used in a liquid crystal image display device including a vertical alignment type liquid crystal panel, and disposed on the front side of the liquid crystal panel for displaying an image, the color change of the image that occurs when the observation angle from the front side is changed. A diffuser to suppress,
When parallel rays incident in a front direction orthogonal to the front face are transmitted, 10% or more of the light diffuses in an angle range of 35 to 55 degrees with respect to the front direction, and 7% or less of the light. Has a diffusion characteristic of diffusing in an angle range of 60 degrees to 90 degrees with respect to the front direction. A diffusion film disposed on the front side for displaying an image of a vertical alignment type liquid crystal panel, for diffusing light incident on the liquid crystal panel,
A diffusion film comprising the diffuser according to claim 1 on a plastic substrate film. A polarizing film disposed on the front side for displaying an image of a vertical alignment type liquid crystal panel and polarizing light incident on the liquid crystal panel,
A polarizing film comprising the diffuser according to claim 1 on the front side for displaying an image. A liquid crystal image display device comprising a vertical alignment type liquid crystal panel,
A liquid crystal image display device comprising the diffuser according to claim 1 on a front side displaying an image of the liquid crystal panel.

Images