JP5135770B2 - LCD display device - Google Patents

Description

  The present invention relates to a liquid crystal image display device such as a liquid crystal television including a vertical alignment type liquid crystal cell in which liquid crystal molecules are vertically aligned in a state where no voltage is applied.

  In recent years, a liquid crystal television has been widely used since a CRT television can easily realize a thin, large screen and high resolution television. In television, it is very important to reproduce the tone well because of the nature of displaying images. In particular, when the dark part is not reproduced well, for example, when it is too dark, the entire image becomes dark, the impression that the black is crushed, and the stereoscopic effect is impaired. On the other hand, if the dark part is too bright, the overall impression is that it is hazy, and the impression is not tight.

  Thus, the reproduction of the gradation around the dark part is very important. There is a paper of Non-Patent Document 1 as a document showing this well. This represents the relationship between the brightness perceived subjectively by humans in various environments and the actual luminance.

  From this, it can be seen that the recognizable brightness of the dark part changes according to the ambient illuminance. Further, in the conventional CRT system television, the luminance from the inside of the display device is sufficiently low, and the light from the outside is appropriately scattered and reflected, so that the luminance level of black increases naturally depending on the external environment. . In other words, in a dark environment, the brightness of black was sufficiently low, and in a bright environment, it had an appropriate black level. For this reason, luminance reproduction as described in the reference has been relatively natural.

  On the other hand, in the conventional liquid crystal, the dependence on the viewing angle is too strong, and such a theory cannot be sufficiently applied. In view of this, in liquid crystal display devices, devices that change the brightness of the backlight according to the surrounding environment have been proposed (Patent Documents 1 to 5). In addition, as a backlight dimming method, there has been proposed an in-vehicle display in which the brightness of the backlight is interlocked with an instrument panel lamp or the like (Patent Document 6). This is dark during night driving and bright during the day. At this time, the PWM method is used as the adjustment method.

  However, none of the patents mentions maintaining an appropriate black level in the video, and does not take into account the change in the black level depending on the viewing angle. In a display device that is desired to be able to view an appropriate image even from such an angle, the level of black changes in an ordinary liquid crystal television. Changing the brightness of the lights was clearly not enough.

  In addition, in the vertical alignment type liquid crystal, when black display is viewed obliquely, the black luminance increases due to the phase difference, which is suppressed by compensating the phase difference with the phase difference compensation film. There is a way to do it. However, since the phase difference is wavelength-dependent, it is difficult to compensate over the entire visible light range, and there is a problem that black coloring occurs when sufficient compensation is made.

Patent documents etc. are as follows.
JCStevens and SS Stevebs "Brightness Function: Effects of Adaption", Journal of Optical Society of America, 53,375-385 (1963) JP-A-62-235883 JP-A-62-276527 JP-A-3-293320 JP-A-4-254820 Japanese Patent Laid-Open No. 4-20924 JP-A-6-315127

  The brightness level of the dark part is sensitively recognized even by a subtle change, and the brightness level of the dark part is very important because it is deeply related to the three-dimensionality of the video and the tightening. If the brightness of black is too bright, the feeling of floating the black will not be received, and if it is too dark, it will be crushed and the texture and stereoscopic effect of the dark part will be impaired. For this reason, it is necessary to set an optimal black luminance.

  At the same time, the optimum black luminance depends on the illuminance of the surrounding environment as the human eye adapts to the surrounding environment, so it must always be adjusted to the surrounding environment. In order to realize these in a liquid crystal display device, the brightness of black changes depending on the viewing angle, and the brightness automatically changes to the appropriate brightness by surface reflection of the display according to the light in the surrounding environment. There was a problem of not becoming.

  In the present invention, a video display device that can be applied to such a theory is realized by using a liquid crystal display element, thereby providing a device that can obtain a good video expression. According to the present invention, when a video display device (particularly, a liquid crystal television) is viewed, various images can be obtained by automatically adjusting an image in accordance with the property that the human eye adapts according to the brightness of the environment. Color correction that suppresses changes in gradation and color depending on the viewing angle so that there is no black floating or black crushing even in an environment like a living room or in a storefront where the TV watched underneath is possible It is an object of the present invention to provide an image display device capable of displaying a suitable image quality (color) to which a diffuser is applied, and to promote improvement of user's willingness to purchase.

The invention according to claim 1 of the present invention includes a diffuser including a diffusion layer from the observer side, an analyzer, a first biaxial retardation optical element, a vertical alignment type liquid crystal cell, and a second biaxial position. A liquid crystal image display device having a phase difference optical element, a polarizer, and a backlight, wherein the diffusion layer has an inner diffuser that causes Mie scattering dispersed in a medium, and a phase difference ratio Nz When the refractive indexes along the axes x and y parallel to the substrate surface of the cell and orthogonal to each other are nx and ny, respectively, and the refractive index along the axis z orthogonal to the axes x and y is nz. , Nz = (nx−nz) / (nx−ny), the phase difference ratio Nz of the first and second biaxial phase difference optical elements is in the range of 1.5 to 3, respectively. A liquid crystal image display device characterized by that.

The invention according to claim 2 of the present invention is the liquid crystal video display device according to claim 1, wherein the illuminance of the backlight changes according to a viewing environment .

The invention according to claim 3 of the present invention is provided with a measuring instrument capable of measuring the illuminance of the viewing environment, and further includes means for changing the illuminance of the backlight in accordance with the measured illuminance. Item 3. A liquid crystal image display device according to Item 2 .

The invention according to claim 4 of the present invention is such that the particle size of the inner surface diffuser in the diffusion layer is in the range of 0.5 to 1.0 μm, and the difference in refractive index between the inner surface diffuser and the medium. 4. The liquid crystal image display device according to claim 1, wherein the liquid crystal display device is in a range of 0.05 to 0.6 .

In general, since the sensitivity of the human eye adapts to the ambient brightness, it is desirable to adjust the overall brightness of the video display device to the ambient brightness in a timely manner.

  Further, in order to make the luminance constant, the black level can be made constant by equalizing with a diffusion film or the like that performs Mie scattering.

  At that time, in a relatively dark environment, the brightness of black needs to be relatively low, while in such an environment, the brightness of white may be low, so the backlight illuminance is reduced. By doing so, it is possible to display a better video with tightness and at the same time to reduce power consumption.

  The brightness that is the threshold value of black that can be distinguished depends on the ambient brightness. In order to be able to express gradation in any lighting environment, it is sufficient to set it higher than a threshold that can discriminate the luminance of black in advance. However, in such an image, since black appears to float, the image becomes sleepy.

  Therefore, it is necessary to align the dark part level within an appropriate range. Therefore, the above object is achieved by arranging a diffusion layer using Mie scattering on the front polarizing plate to make the luminance level uniform and optimizing the black level according to the illuminance of the environment.

  In addition, by limiting the range, it is possible to display optimal images without using a low-reflection layer, high-contrast liquid crystal cell, or polarizing plate, thereby reducing costs and increasing the brightness of the backlight in the living environment. In principle, it is possible to reduce the power consumption to 1/3 to 1/6 by suppressing it from the brightness at the store.

  In addition, the inner diffuser that causes Mie scattering such that the diffuser has less backscattering with respect to visible light, has a wide scattering angle, and has wavelength dependency, such as under a dark room, under indirect lighting, under a bright room, and storefront display. The above film is combined with a polarizing film, applied to a liquid crystal display element, placed further on the front side of the polarizing layer on the viewer side, and according to the angle at which the image display device (liquid crystal television) is viewed By uniformizing the change in luminance of black, a liquid crystal television set that takes advantage of the features such as dark area expressiveness and low cost, which are notable for black crushing and black floating, especially with vertical alignment type liquid crystal, is realized.

  Hereinafter, a liquid crystal image display device according to an embodiment of the present invention 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 more particularly to a liquid crystal image display device that suppresses a color change depending on a viewing angle.

  As shown in FIG. 1, the liquid crystal image display apparatus A of the present embodiment includes a liquid crystal panel 1 and a backlight (backlight unit) 2 that irradiates the liquid crystal panel 1 with light. Further, the liquid crystal panel 1 includes a diffuser 3, an analyzer 4 having a diffusion layer 3 a having an inner diffuser that causes Mie scattering from visible light from the front surface A 1 side of the liquid crystal display device A that displays images. The first biaxial retardation optical element 5, the vertical alignment type liquid crystal cell 6, the second biaxial retardation optical element 7, the polarizer 8, and the polarizer protective film 9 are laminated and arranged in this order. The brightness enhancement film 10 is disposed between the polarizer 8 and the backlight 2.

For example, the diffuser 3 includes an inner surface diffuser dispersed in a radiation curable resin on a transparent plastic substrate film 3b such as a triacetyl cellulose (TAC) film, a polyethylene terephthalate (PET) film, or a cycloolefin film. Diffusion layer 3 formed by
a is laminated and formed. At this time, the diffusion layer 3a is preferably formed by coating the plastic base film 3b with a thickness of 3 to 50 μm, preferably 3 to 30 μm. Moreover, the inner surface diffuser has a refractive index different from the refractive index of light of the radiation curable resin, and the inner layer diffuser is dispersedly disposed in the radiation curable resin of the binder, whereby the diffusion layer 3a. A plurality of fine regions having different refractive indexes made of an inner surface diffuser are formed inside. And by this inner surface diffuser, according to the particle diameter of the inner surface diffuser, the brightness enhancement film 10, the protective film 9, the polarizer 8, the second biaxial retardation optical element 7, which is irradiated from the backlight 2, Light having a short wavelength in the wavelength range of visible light transmitted through the diffusion layer 3a through the vertical alignment type liquid crystal cell 6, the first biaxial retardation optical element 5, and the analyzer 4 is more strongly (selectively) scattered. (Mie scattering). The inner surface diffuser may be uniformly distributed in the radiation curable resin (in the diffusion layer 3a) or may be unevenly distributed.

  The radiation curable resin is preferably one having an acrylate functional group, more preferably polyester acrylate or urethane (meth) 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. Further, it may be a vinyl acetate resin, epoxy (meth) acrylate, phenoxy resin, butyral resin, silicon (meth) acrylate, styrene resin, cellulose derivative, alicyclic olefin resin, or the like.

  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) Acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, methyl (meth) acrylate, ethyl (meth) Acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, finyl (meth) acrylate, etc. And the like.

  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.

Further, in order to efficiently proceed the polymerization of the radiation curable resin, a polymerization initiator (I) may be blended, and the polymerization initiator (I) is not particularly limited and is not limited to active energy. Any compound that can generate radicals when irradiated with. 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) butane-1 -On, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. 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 (MEK), 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. And alcohols such as methanol, ethanol, isopropyl alcohol (IPA), etc., and a solvent suitable for the polymer can be selected and used at an appropriate time. The radiation curable resin, the raw material monomer, and the solvent may be used singly or in combination.

  On the other hand, silica particles, styrene particles, melamine particles, acrylic particles, alumina particles, titanium oxide particles, hollow particles or composite particles thereof can be used as the inner surface diffuser of the present embodiment. Moreover, these particles may be used alone or in combination, or a plurality of them may be combined. In addition, it is preferable that content of this inner surface diffuser is 3%-50% by mass (mass of the diffusion layer 3a).

  Here, the inner surface diffuser having a refractive index different from the refractive index of the light of the radiation curable resin more strongly scatters short wavelengths in the visible light wavelength range according to the particle diameter (Mie scattering), and backscatters. When scattering in a wide range (Mie scattering), it is determined by the scattering cross section how much light is scattered in the visible wavelength range and how much light is not scattered. This is defined in proportion to the particle size of the inner surface diffuser and the scattering factor.

  Note that the particle size of the inner surface diffuser strongly scatters in the short wavelength region and increases the scattering angle to obtain gradation and color correction effects. It is desirable that the thickness is about 1.0 μm.

  Further, when the refractive index difference between the inner surface diffuser and the medium 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 scattering increases rapidly. For this reason, when the refractive index difference is 0.05 or less, the light diffusion effect by the diffusion layer 3a cannot be obtained. When the refractive index difference is 0.6 to 0.8 or more, the image contrast is low. Will be reduced. Therefore, it is desirable that the difference in refractive index between the inner diffuser and the medium is 0.05 to 0.6 from the viewpoint of suppressing a reduction in image contrast while increasing the viewing angle.

  And the diffuser 3 provided with the said diffused layer 3a which consists of said radiation curable resin and an inner surface diffuser scatters more blue light of a short wavelength among visible lights, The color change of the liquid crystal panel 1 And it becomes a layer which reduces black float and suppresses glare.

On the other hand, the analyzer 4 and the polarizer 8 are arranged in crossed Nicols as shown in FIG. Further, the liquid crystal cell 6 is formed so as to sandwich liquid crystal molecules (liquid crystal) 6c between one substrate 6a provided with a color filter and the other substrate 6b provided with a TFT (thin film transistor), as shown in FIG. In addition, the liquid crystal molecules 6c are vertically aligned in a state where no voltage is applied, and the liquid crystal molecules 6c are tilted in a state where a voltage is applied as shown in FIG. In the liquid crystal cell 6, the liquid crystal molecules 6 c in FIG. 3 are vertically aligned, the polarization is not affected by the liquid crystal cell 6, and the transmittance is low. The liquid crystal display device A has a screen (front surface A 1). , Black is displayed.
Further, in the state where the voltage of FIG. 4 is applied and the liquid crystal molecules 6c are tilted, the polarized light rotates and white is displayed on the screen (front surface A1) of the liquid crystal display device A. It should be noted that the intermediate gradation is displayed on the screen in the middle of the state of the liquid crystal molecules 6c in FIGS.

  In the present embodiment, the first biaxial retardation optical element 5 is composed of an analyzer protective film and retardation compensation film, and the second biaxial retardation optical element 7 is phase protection. It consists of a film and polarizer protective film. Further, the first and second biaxial phase difference optical elements 5 and 7 are formed to have the same phase difference, and as shown in FIG. The polarizer 8) is arranged so as to be orthogonal (or parallel) to the absorption axis. Further, in the present embodiment, the second biaxial retardation optical element 7 is arranged so that the slow axis is orthogonal to the absorption axis of the polarizer 8.

  The backlight 2 is a cold-cathode tube, and a brightness enhancement film (BEF: Brightness Enhancement Film for applying light condensing property to the liquid crystal panel 1 or a coating of particles, phase difference) 10 using a film). With this brightness enhancement film 10, the light emitted from the backlight 2 can be condensed, that is, the light in the oblique direction can be reduced, and the brightness at the front surface A <b> 1 of the liquid crystal display device A can be increased.

  Next, the operation and effect of the liquid crystal image display apparatus A having the above configuration will be described.

  In general, a television is sometimes placed in the corner of a room, and a picture is seen from various positions such as a living room. In view of the above, it is considered appropriate to consider that the viewing angle range is about 45 degrees. Therefore, it is important that clear images can be seen within this range.

  Considering a normal living room, the lighting is in the center of the room and the TV is on the wall. In many cases, depending on the size of the room and the height of the ceiling, consider the lighting direction from about 45 degrees. This is considered valid.

  Here, FIG. 5 is a diagram showing the polarization state when light is incident on the VA liquid crystal cell (VA) 6 obliquely as a Poincare spherical behavior. In this figure, P1 shows the polarization state of the incident light that is polarized while the light irradiated from the backlight 2 is transmitted through the brightness enhancement film 10, and P2 is after the liquid crystal cell (VA) 6 is transmitted. The polarization state is shown. E represents the coordinates of light orthogonal to the analyzer 4 and indicates that light leakage occurs when black is displayed by the amount of deviation between P2 and E. As shown in this figure, the light incident on the liquid crystal cell 6 from an oblique direction is polarized by passing through the liquid crystal cell 6 and greatly changes (shifts) from the state orthogonal to the analyzer 4. When the screen displaying black is viewed obliquely, black floating occurs.

  On the other hand, when the first and second biaxial retardation optical elements 5 and 7 are provided, as shown in FIG. 6 showing the polarization state as a Poincare spherical behavior as in FIG. It is possible to compensate for the polarization state so that the light state is orthogonal to the analyzer 4 to reduce the black light leakage. At this time, the first and second biaxial retardation optical elements 5 and 7 are formed so as to have biaxiality and the same phase difference, respectively, and the respective slow axes are connected to the analyzer 4 or By arranging the polarizer 8 so as to be orthogonal (or parallel) to the absorption axis of the polarizer 8, it is possible to reduce black light leakage as described above. Further, by making the slow axis of the second biaxial retardation optical element 7 orthogonal to the absorption axis of the polarizer 8, it is possible to reliably reduce black light leakage.

Further, the retardation film provided in the conventional liquid crystal panel has refractive indexes along axes x and y that are parallel to and orthogonal to the substrates 6a and 6b of the liquid crystal cell, respectively, and nx and ny, respectively. , Where the refractive index along the axis z orthogonal to y is nz, the phase difference ratio Nz (Nz = (nx−nz) / (nx−ny)) is set to 2 or more, usually about 5 to 10 It is said that. In this conventional phase difference film, as shown in FIG. 7, the degree of polarization in the phase difference film differs depending on the wavelength of the transmitted light (three primary colors B, R, G), and the occurrence of coloring due to the wavelength is suppressed. For this purpose, the retardation ratio Nz is set to 2 or more, or about 5 to 10, that is, as shown in FIG. 8, coloring is suppressed by weakening the compensation effect of the retardation film.

On the other hand, by providing the diffuser (diffusion layer 3a, diffusion film) 3 in addition to the first and second biaxial retardation optical elements 5 and 7 as in the liquid crystal image display apparatus A of the present embodiment. As shown in FIG. 9, in a state where black is displayed on the screen, black color shift is suppressed depending on the viewing angle. In addition, in the liquid crystal image display apparatus A of the present embodiment, as shown in FIG. 10, the transmittance (black luminance) when viewed obliquely in a state where black is displayed is near the center wavelength of visible light. With a minimum value of transmittance in the range from 410 nm to 610 nm, which is half of this sensitivity, centered around 555 nm, which has the highest specific visual sensitivity in a two-degree field of view, black luminance can be particularly reduced. Is possible. The first and second biaxial phase difference optical elements 5 and 7 having a phase difference ratio Nz with little black light leakage even when black coloring is strengthened by the diffusion layer 3a are desirable. Each of the first and second biaxial phase difference optical elements 5 and 7 has a phase difference ratio Nz close to 2, preferably 1.5 to 3. At this time, it is possible to suppress the influence of the phase difference due to the wavelength to some extent by matching the phase difference of the phase difference compensation film phase difference between the viewer side and the viewer side.

Therefore, in the liquid crystal image display apparatus A of the present embodiment, the diffusion in which the color change (color shift) when viewing the image from an oblique characteristic peculiar to the vertical alignment type liquid crystal is arranged on the viewer (observation surface, front surface A1) side. Suppressing by the layer 3a, and further compensating for oblique light leakage, which is a defect of the liquid crystal image display device including the vertical alignment type liquid crystal cell 6, by the first and second biaxial retardation optical elements 5 and 7. Thus, it is possible to suppress a color change when viewed from an oblique direction, and to obtain a high contrast with particularly suppressed black float to some extent.

  In addition, when a diffusion layer 3a that can diffuse (scatter) light over a wide diffusion range is used, external light is also scattered, particularly when a liquid crystal image display device is used in a bright room. Although the floating is conspicuous, in the liquid crystal image display device A of the present embodiment, the diffusion layer 3a is formed with an inner surface diffuser that causes Mie scattering, so that backscattering is small and the scattering angle is wide. By using the inner surface diffuser having wavelength dependency, it is possible to suppress black float to some extent while providing a wide diffusion range.

  Furthermore, by providing the brightness enhancement film 10 disposed on the backlight 2 side, the light can be condensed in the front direction where the performance of the liquid crystal panel 1 is the most, and the condensed light is diffused in the diffusion layer 3a. The liquid crystal image display apparatus A with higher performance can be obtained by diffusing with. In general, since the contrast is high on the front side of the liquid crystal panel, higher contrast can be obtained as a whole by condensing light on the backlight side in the front direction and diffusing it on the front side of the liquid crystal panel.

  In addition, the black matrix disposed on one substrate (front glass) 6a of the liquid crystal cell 6 can be thinned without increasing the color blur from the adjacent liquid crystal cell by increasing the degree of light collection. As a result, the aperture ratio can be further increased. Similarly, since the rate at which obliquely scattered light is scattered by a photo spacer or the like is reduced, an effect of increasing the contrast as a whole can be expected.

The diffusion layer 3a is composed of a radiation curable resin and an inner surface diffuser, and the inner surface diffuser does not need to be a particulate material. For example, a radiation curable type is used so that the liquid inner surface diffuser is dispersed. A fine region having a different refractive index made of an inner surface diffuser may be formed in the diffusion layer 3a in a state where it is mixed with a resin and this mixed solution is applied and cured on the plastic substrate film 3b. . In this case, the inner surface diffuser does not need to be formed into particles, that is, spherical, and the short wavelength in the wavelength range of visible light is more strongly scattered (Mie scattering) depending on the size (average diameter). become. In addition to this, the medium in which the inner surface diffuser is dispersedly arranged need not be limited to the radiation curable resin, and may be another substance as long as it has transparency.

  Furthermore, the surface (screen, front surface A1) of the diffusion layer 3a (the diffuser 3) is formed in a concavo-convex shape, that is, the surface is subjected to anti-glare treatment. You may make it provide the glare-proof property which prevents that it reflects.

  However, this alone is not sufficient to prevent black floating and black crushing. That is, as the luminance level of black, 1 brim to 2 bris as a unit of brightness described in Non-Patent Document 1 is appropriate. If it is up to 3 bris, it is within the allowable range. If the level is darker than this, the threshold that can be discriminated is not reached. Also, when it gets brighter than this, you will get the impression of black floating.

For example, the formula for obtaining the brightness at 100 lx under the illuminance like living room is ψ [bril] = 3.7 × (L [cd / m] where the luminance is L and the brightness is ψ. ² ] /3.18-0.037) ^0.38 , the brightness corresponding to 1 brilli and ² brilli is 0.2 cd / m ² and 0.7 cd / m ² at this time. It is better to keep the brightness level within this range.

Even in the case where black floats due to the influence of external light, it is preferable to keep the brightness equivalent to ² to 3 bril, the black luminance level of 0.7 cd / m ² and 2 cd / m ² . Practically, this range is considered appropriate considering the influence of surface reflection and the like.

The white level is preferably about 13 to 17 bris centering on 15 bris in consideration of highlights and the like. Therefore, the luminance is about 85 cd / m ² to 175 cd / m ² .

It is appropriate that the skin color level is centered around 10 bris, and the brightness at this time is about 45 cd / m ² . As the skin color at this time, for example, the skin color specified by the Macbeth color chart can be used. At this time, the contrast is between 43 and 250.

Similarly, at the store, the formula for obtaining the brightness under 1000 lx of the general illuminance at the store is ψ = 2.2 × (L / 3.18−0.16) ^0.41. , the brightness of the corresponding 2bril is 1 cd / m ² and 3 cd / m ^2, in the shop environment, it is preferable accommodate the black luminance level in this range.

Even when black floats due to the influence of external light, the brightness equivalent to ^{2 to 3} bril is 3 cd / m ² and 7 cd / m ² , and the brightness level of black falls within this range in the storefront environment. It is good. Practically, this range is considered appropriate considering the influence of surface reflection and the like.

  The white level is preferably about 13 to 17 bris centering on 15 bris in consideration of highlights and the like.

Therefore, the luminance is about 250 to 450 cd / m ² .

It is appropriate that the skin color level is centered around 10 bris, and the luminance at this time is about 130 cd / m ² .

  At this time, the contrast is between 83 and 150. In other words, even if the viewing angle changes, the black level needs to be within about three times even within the range of 45 degrees.

  By the way, in the vertically oriented liquid crystal, the gradation near the middle is hard to change. Therefore, if the dark part is stabilized, it is possible to obtain an image that hardly changes as a whole.

  Such a display makes it possible to express delicate images, and to display images that are natural and do not make you sleepy.

  In some cases, the signal at the lowest level of the input signal itself is not at a level of 0. If such a signal is output as it is, black will be floated. Therefore, in such an image, it is desirable that the minimum level of the signal is automatically adjusted so as to be the optimum black.

In adjusting the brightness of the display depending on the environment, a device for directly measuring the illuminance of the environment may be provided to optimize the brightness from the measured illuminance.
Further, even if a mode for selling at a store and a mode for installing in a living room after purchase are provided, a realistic solution can be obtained.

  Table 1 is an example of the optimum luminance at each signal level presented in the invention.

  In addition, this invention is not limited to said embodiment, In the range which does not deviate from the meaning, it can change suitably.

1 is a conceptual cross-sectional view showing a liquid crystal image display device according to an embodiment of the present invention. It is a perspective view which shows the arrangement | positioning state of the analyzer of the liquid crystal image display apparatus which concerns on one Embodiment of this invention, a polarizer, and the 1st and 2nd biaxial phase difference optical element. It is a figure which shows the state which has not applied the voltage to the vertical alignment type liquid crystal cell with which the liquid crystal image display apparatus which concerns on one Embodiment of this invention comprises. It is a figure which shows the state which applied the voltage to the vertical alignment type liquid crystal cell with which the liquid crystal image display apparatus which concerns on one Embodiment of this invention comprises. It is the figure which showed the state of the polarization | polarized-light when light injects into VA type | mold liquid crystal cell from diagonal as a behavior in Poincare sphere. It is the figure which showed the state of the polarization | polarized-light when light injects into the liquid crystal panel provided with the 1st and 2nd biaxial phase difference optical element from diagonal as a behavior in Poincare sphere. It is the figure which showed the state of the polarization | polarized-light when light injects into the liquid crystal panel provided with the conventional phase difference film from diagonal as behavior in Poincare sphere. It is the figure which showed the state of the polarization | polarized-light when light inclines into the liquid crystal panel provided with the conventional phase difference film which adjusted phase difference ratio as a behavior in Poincare sphere. It is a figure which shows the state of the black color shift with respect to the presence or absence of the diffusion layer of the liquid crystal video display apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the wavelength at the time of seeing from the diagonal in the state which displayed black with respect to the liquid crystal image display device which concerns on one Embodiment of this invention, and black luminance. It is a figure which shows the relationship between the wavelength at the time of seeing from the diagonal in the state which displayed black with respect to the conventional liquid crystal image display device, and black luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight 3 Diffuser 3a Diffusion layer 3b Plastic base film 4 Analyzer 5 1st biaxial phase difference optical element (biaxial phase difference optical element)
6 Liquid crystal cell 6a One substrate 6b The other substrate 6c Liquid crystal molecules (liquid crystal)
7 Second biaxial retardation optical element (biaxial retardation optical element)
8 Polarizer 9 Polarizer Protective Film 10 Brightness Enhancement Film A Liquid Crystal Image Display Device

Claims (4)

From the observer side, it has a diffuser with a diffusion layer, an analyzer, a first biaxial retardation optical element, a vertical alignment type liquid crystal cell, a second biaxial retardation optical element, a polarizer, and a backlight. A liquid crystal display device,
The diffusion layer has dispersed therein an inner surface diffuser that causes Mie scattering in the medium; and
The phase difference ratio Nz is a refractive index along axes x and y parallel to the substrate surface of the liquid crystal cell and orthogonal to each other, and nx and ny, respectively, and refraction along an axis z orthogonal to the axes x and y. When the rate is nz, when Nz = (nx−nz) / (nx−ny),
A liquid crystal image display device, wherein a phase difference ratio Nz of the first and second biaxial retardation optical elements is in a range of 1.5 to 3, respectively.   The liquid crystal image display device according to claim 1, wherein the illuminance of the backlight changes according to a viewing environment.   3. The liquid crystal display device according to claim 2, further comprising a measuring instrument capable of measuring the illuminance of the viewing environment, and further comprising means for changing the illuminance of the backlight in accordance with the measured illuminance. The particle size of the inner surface diffuser in the diffusion layer is in the range of 0.5 to 1.0 μm, and the refractive index difference between the inner surface diffuser and the medium is in the range of 0.05 to 0.6. The liquid crystal image display device according to claim 1, wherein the liquid crystal image display device is a liquid crystal image display device.

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