JP5364343B2 - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element attaining satisfactory display and to provide a liquid crystal display device. <P>SOLUTION: In the liquid crystal display element including first and second transparent substrates, a liquid crystal layer interposed between the first and second transparent substrates and vertically aligned, a first polarizing plate disposed on the side opposite to the liquid crystal layer of the first transparent substrate, a second polarizing plate disposed on the side opposite to the liquid crystal layer of the second transparent substrate and disposed in crossed Nicol state to the first polarizing plate and a visual angle compensation plate disposed between the first transparent substrate and the first polarizing plate or between the second transparent substrate and the second polarizing plate so that an in-plane delay phase axis thereof is orthogonal to an absorption axis of the nearer polarizing plate of the first and second polarizing plates and having negative biaxial optical anisotropy, sum total retardation Rthall in the thickness direction except the liquid crystal layer in the liquid crystal display element satisfies 250 nm&le;Rthall&le;400 nm, retardation Re in an in-plane direction of the visual angle compensation plate satisfies 5 nm&le;Re&le;40 nm, and retardation &Delta;nd of the liquid crystal layer satisfies 1.12&times;Rthall&le;&Delta;nd&le;1.40&times;Rthall. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display (LCD) and a liquid crystal display device.

  The “vertical alignment type” liquid crystal display element in which the liquid crystal molecular alignment in the liquid crystal layer is vertical or substantially vertical to the substrate has a very good black level when no voltage is applied. Further, on one or both sides of the liquid crystal cell, by introducing an optical compensator having negative optical anisotropy having an appropriate parameter between the liquid crystal cell and the polarizing plate, better viewing angle characteristics can be obtained. Can do.

  An invention of a viewing angle compensation method using an optical compensator having negative uniaxial optical anisotropy, a so-called (negative) C plate is disclosed (for example, see Patent Document 1). In the liquid crystal display element described in Patent Document 1, the C plate is disposed between the glass substrate of the liquid crystal cell adjacent to the upper polarizing plate, the glass substrate of the liquid crystal cell adjacent to the lower polarizing plate, or both. The

  By this method, it is possible to cancel the optical anisotropy of the vertically aligned liquid crystal layer and eliminate the viewing angle dependency of the light transmittance when no voltage is applied.

  However, since the polarizing plates bonded to both sides of the liquid crystal cell are arranged in crossed Nicols, a good black state can be realized during frontal observation, but especially when the viewing angle is changed, especially from the absorption axis of the upper and lower polarizing plates When observed from a direction deviated by 45 °, light leakage is observed. This is a phenomenon caused by the “viewing angle characteristics of the polarizing plate”. It is known that the “viewing angle characteristic of a polarizing plate” deteriorates the viewing angle characteristic of a liquid crystal display element.

  Patent Document 1 also describes a method of preventing deterioration in viewing angle characteristics of a liquid crystal display element due to “viewing angle characteristics of a polarizing plate” using an optical compensator having negative biaxial optical anisotropy.

  There is also a disclosure of an invention of a viewing angle compensation method having a large effect performed by using an optical compensator having negative biaxial optical anisotropy (see, for example, Patent Document 2).

  Patent Document 2 discloses that an optical compensation plate having negative biaxial optical anisotropy having an in-plane retardation of 120 nm or less is disposed on at least one of the upper and lower polarizing plates and the upper and lower glass substrates. The in-plane retardation of the optical compensation plate is more preferably 20 nm or more and 60 nm or less, the retardation in the thickness direction of the optical compensation plate is 2 times or less of the retardation of the liquid crystal layer, and the optical compensation plate has an in-plane slow axis. It is described that the effect of viewing angle compensation can be enhanced by arranging the polarizer so as to be substantially parallel or substantially orthogonal to the absorption axis of the adjacent polarizing plate.

  In particular, an optical compensator having negative biaxial optical anisotropy is arranged when its C-plate is used by arranging the in-plane slow axis so that it is perpendicular to the absorption axis of the adjacent polarizing plate. The problem of deterioration of the viewing angle characteristics of the liquid crystal display element due to the “viewing angle characteristics of the polarizing plate” can be solved. As a result, even when the liquid crystal display element is observed from an oblique direction with a 45 ° azimuth from the polarizing plate absorption axis, it is possible to realize a light transmittance substantially equal to that in frontal observation.

  Hereinafter, an optical compensation plate having negative biaxial optical anisotropy is referred to as a negative biaxial film. For a film-shaped optical compensator, when the in-plane refractive index is nx with respect to the slow axis direction, ny with respect to the fast axis direction, nz is the refractive index in the thickness direction, and d is the thickness, the C plate has nx = An optical compensator having a relationship of ny> nz and a negative biaxial film are defined as an optical compensator having a relationship of nx> ny> nz. The in-plane retardation Re is defined by Re = (nx−ny) * d, and the retardation Rth in the thickness direction is defined by Rth = ((nx + ny) / 2−nz) * d.

  (I) A vertical alignment type liquid crystal display element to which an optimum viewing angle compensation method using a negative biaxial film described in Patent Document 2 is applied, (ii) a cold cathode tube, an inorganic LED (Light Emitting Diode), etc. A backlight comprising a multi-color light source having a plurality of peak emission wavelengths, which is composed of a configured white light source or organic LED, and (iii) applying an electrical signal to the liquid crystal display element to switch between a light and dark display state In a liquid crystal display device having a drive device, when no voltage is applied, when observed from a direction of a deep polar angle (for example, 50 °) with respect to the normal direction of the liquid crystal display element, 45 ° azimuth from the polarizing plate absorption axis In addition, a light leakage state colored in blue, purple, yellow, or the like may be observed.

  This light leakage state is caused by the in-plane retardation Re of the optical compensation plate and the optical characteristics expressed in the liquid crystal layer (the optical axis exhibits positive uniaxial optical anisotropy in the thickness direction). It is based on the technology that improves the viewing angle characteristics of the polarizing plate by skillfully combining the optical characteristics. The optical compensator compensates the viewing angle characteristics of the liquid crystal layer together with the polarizing plate, but the wavelength dispersion characteristics of the optical compensator required for the viewing angle compensation of the polarizing plate and the viewing angle compensation of the liquid crystal layer are different. When matched with the characteristics, the other viewing angle compensation becomes insufficient. For this reason, the viewing angle compensation method disclosed in Patent Document 2 suppresses a change in color tone even though it can suppress the light transmittance particularly at an observation angle of 45 ° from the polarizing plate absorption axis at a polar angle deep. It is very difficult.

  The inventor of the present application conducted a simulation analysis in order to grasp the above-described phenomenon specifically. For the simulation, a liquid crystal display simulator LCD MASTER6 manufactured by Shintech Co., Ltd. was used.

  FIG. 8 shows the structure of a liquid crystal display element to be simulated.

  A monodomain vertical alignment type liquid crystal cell 10 is disposed between an upper (front side) polarizing plate (polarizing plate with viewing angle compensation plate) 14 and a lower (back side) polarizing plate 15 which are arranged in crossed Nicols. The monodomain vertical alignment type liquid crystal cell 10 includes an upper glass substrate (transparent substrate) 11, a lower glass substrate (transparent substrate) 12, and a monodomain vertical alignment liquid crystal layer 13 sandwiched between the substrates 11 and 12. Composed. Transparent electrodes are formed of, for example, ITO (Indium Tin Oxide) on the surfaces of the upper and lower glass substrates 11 and 12 on the liquid crystal layer 13 side.

  The retardation of the liquid crystal layer 13 was about 320 nm. The liquid crystal layer 13 is assumed to have an anti-parallel alignment structure set at a pretilt angle of 89 ° when the in-plane direction of the substrate is 0 °, and the orientation of the pretilt angle is at the center in the thickness direction of the liquid crystal layer 13. The angle between the absorption axes of the upper and lower polarizing plates 14 and 15 was 45 ° (270 ° azimuth in the illustrated azimuth coordinate system).

  The upper polarizing plate (polarizing plate with viewing angle compensation plate) 14 includes a polarizing layer 14a and a negative biaxial film 14b. The absorption axis of the polarizing layer 14a was set to 135 °. The negative biaxial film 14b is formed of a norbornene-based cyclic olefin film, and the in-plane slow axis orientation is set to 45 ° so as to be orthogonal to the absorption axis of the nearest polarizing layer (polarizing layer 14a). . Furthermore, the in-plane retardation Re of the negative biaxial film 14b was set to 55 nm, and the retardation Rth in the thickness direction was set to 220 nm.

  The lower polarizing plate 15 includes a polarizing layer 15a and a TAC film 15b. The absorption axis of the polarizing layer 15a is 45 ° azimuth. It is known that the TAC film 15b functions as a C plate. The retardation Rth in the thickness direction of the TAC film 15b was set to about 60 nm.

  The upper polarizing plate (polarizing plate with viewing angle compensation plate) 14 does not include a TAC film. Further, the polarizing layers 14a and 15a of the upper and lower polarizing plates 14 and 15 were assumed to be SKN18243T manufactured by Polatechno Co., Ltd. Further, the standard light source C (white light source) was used as the light source of the backlight 20 disposed below the lower polarizing plate 15.

  On the other hand, for the sake of comparison, simulation analysis was also performed on the liquid crystal display element structure (liquid crystal display element structure compensated using a C plate) disclosed in Patent Document 1.

  FIG. 9 shows the liquid crystal display element structure. A point of using the upper polarizing plate 16 in which the TAC film 16b is disposed on the polarizing layer 16a having an absorption axis orientation of 135 °, and between the upper glass substrate 11 and the upper polarizing plate 16 of the monodomain vertical alignment type liquid crystal cell 10. Except for the point where the C plate 17 is arranged, it is the same as the liquid crystal display element structure shown in FIG.

  The upper polarizing plate 16 is the same polarizing plate as the lower polarizing plate 15. The C plate 17 was formed of a norbornene-based cyclic olefin film, and the retardation Rth in the thickness direction was 180 nm.

  FIG. 10 is a graph showing a spectral spectrum when no voltage is applied in the liquid crystal display element having the structure shown in FIGS. This figure shows a spectrum obtained by observation from the direction of the polar angle of 50 ° when the orientation is 0 ° and the substrate normal direction of the liquid crystal display element is defined as the polar angle of 0 °.

  The horizontal axis of the graph represents the wavelength of light in the unit “nm”, and the vertical axis of the graph represents the light transmittance in the unit “%”. Further, a curve (curve a) indicated by a solid line represents a spectral spectrum in the liquid crystal display element of FIG. 8 provided with a negative biaxial film, and a curve (curve b) indicated by a broken line represents the liquid crystal display of FIG. 9 provided with a C plate. It represents that in the device.

  Reference is made to curve a. In the liquid crystal display element of FIG. 8, a state in which the transmittance of light having a wavelength of about 530 nm is zero is realized, but light leakage increases as the wavelength shifts from about 530 nm to the long wavelength side or the short wavelength side. There is a trend. When the liquid crystal display device manufactured under the same conditions as the simulation conditions was visually observed, the liquid crystal display device was observed to have a red-purple coloration when observed at a deep polar angle from the substrate normal direction and at the polarizing plate absorption axis direction. It was.

  Refer to curve b. It can be seen that the liquid crystal display element of FIG. 9 has a greater degree of light leakage as compared with the liquid crystal display element of FIG. However, it is understood that the light leakage state is flat in a wide wavelength range. When the manufactured actual device was observed from the orientation and observation angle at which coloring was observed in the liquid crystal display element of FIG. 8, light leakage was large, but coloring was hardly recognized.

  In the liquid crystal display element of FIG. 8 that performs viewing angle compensation using a negative biaxial film, the viewing angle characteristics of the polarizing plate cannot be completely eliminated in the entire wavelength range, and light leakage occurs, so that an optical compensation plate and a liquid crystal layer are formed. Depending on the setting parameters, it may be colored in various colors. Further, the negative biaxial film parameters and the variation in the liquid crystal layer thickness remarkably appear as color tone changes, which are likely to cause display unevenness.

  On the other hand, in the liquid crystal display element of FIG. 9 using the C plate, there is a possibility that luminance unevenness may occur, but the color tone change is greatly reduced as compared with the liquid crystal display element of FIG. 8, and the margin of each parameter is large. .

  Reference is made to FIGS. 11A and 11B. Next, the inventors of the present application examined the viewing angle characteristics of the liquid crystal display elements shown in FIGS. 8 and 9 in the 180 ° and 0 ° azimuth directions.

  FIG. 11A shows a spectral spectrum when the liquid crystal display element of FIG. 8 is observed from the polar angle of 50 °, and FIG. 11B shows that of the liquid crystal display element of FIG. In both figures, the horizontal axis of the graph represents the wavelength of light in the unit “nm”, and the vertical axis of the graph represents the light transmittance in the unit “%”. A curve a indicated by a solid line is an observation result at an azimuth of 0 °, and a curve b indicated by a broken line is an observation result at an azimuth of 180 °.

  In both of FIGS. 11A and 11B, there is a difference in spectrum between 0 ° azimuth observation and 180 ° azimuth observation. This is a phenomenon observed only when the liquid crystal layer has a monodomain vertical alignment having a pretilt angle. If the pretilt angle is 90 °, there is no difference in the viewing angle characteristics in the horizontal direction, but the pretilt angle is 90 °. The smaller the size, the greater the left-right asymmetry.

  11A and 11B are compared. In FIG. 11B (the liquid crystal display element using the C plate in FIG. 9), the spectrum is relatively flat. Although only the luminance difference is recognized in the direction, in FIG. 11A (the liquid crystal display element using the biaxial film in FIG. 8), the wavelength at which the minimum transmittance can be obtained differs from left to right. It is thought that different colors are observed in the direction. When the actual device of the liquid crystal display element having the same structure as in FIG. 8 was observed, a difference in color tone was clearly recognized in the left-right direction.

  In recent vertical alignment type liquid crystal display elements, priority is given to good viewing angle characteristics in light transmittance. Therefore, a negative biaxial film with good luminance viewing angle characteristics is used as an optical compensator for compensating the viewing angle characteristics. Is often used.

  As a negative biaxial film, a new ZEONOR manufactured by Optes Co., Ltd. using a norbornene-based cyclic olefin material, an optical film manufactured by Konica Minolta Opto Co., Ltd., which is drawn based on a TAC material, n-TAC Co., Ltd. FUJIFILM V-TAC and other products are on the market and are distributed in large quantities. On the other hand, as an optical film having the same optical characteristics as the C plate, VAC film manufactured by Sumitomo Chemical Co., Ltd. has been put on the market. Is becoming difficult.

Japanese Patent No. 2047880 Japanese Patent No. 3330574

An object of the present invention is to provide a liquid crystal display device capable of realizing good display.

According to one aspect of the present invention, the first and second transparent substrates, the vertically aligned liquid crystal layer sandwiched between the first and second transparent substrates and having a retardation Δnd of less than 350 nm , and the first The first polarizing plate disposed on the opposite side of the transparent substrate to the liquid crystal layer and the second transparent substrate on the opposite side of the liquid crystal layer are disposed in crossed Nicols with the first polarizing plate. a second polarizing plate, between the first transparent substrate and the first polarizing plate, or, to either between the second transparent substrate and the second polarizing plate, the surface A viewing angle compensator having a negative biaxial optical anisotropy disposed so that an inner slow axis is perpendicular to an absorption axis of a neighboring polarizing plate of the first and second polarizing plates A liquid crystal display element; and a white light source disposed on a side of the second polarizing plate opposite to the second transparent substrate. In the liquid crystal display element, the total retardation Rthall in the thickness direction other than the liquid crystal layer is 250 nm ≦ Rthall ≦ 400 nm, and the retardation Re in the in-plane direction of the viewing angle compensation plate is 5 nm ≦ Re ≦ 40 nm, The retardation Δnd of the liquid crystal layer is 1.24 × Rthall < Δnd ≦ 1.40 × Rthall, and the liquid crystal display element is illuminated with the white light source and observed from the normal direction of the first transparent substrate. Chromaticity when observed from the direction of 50 ° with the normal direction of the first transparent substrate in the direction of 45 ° with the absorption axis of the second polarizing plate, with the chromaticity at that time being x0 and y0 And x, y, a liquid crystal display device in which x0−0.02 ≦ x ≦ x0 + 0.02 and y0−0.02 ≦ y ≦ y0 + 0.02 is provided.

According to another aspect of the present invention, the first and second transparent substrates, said first and sandwiched between the second transparent substrate, and a liquid crystal layer which retardation Δnd is vertical orientation below 350nm The first polarizing plate disposed on the opposite side of the liquid crystal layer of the first transparent substrate and the first polarizing plate on the opposite side of the liquid crystal layer of the second transparent substrate. An in-plane slow axis is orthogonal to the absorption axis of the first polarizing plate between the second polarizing plate arranged in Nicol, the first transparent substrate, and the first polarizing plate. Between the first viewing angle compensation plate having negative biaxial optical anisotropy and the second transparent substrate and the second polarizing plate, an in-plane slow axis is provided between the first viewing angle compensation plate and the second polarizing plate. A liquid crystal display element having a second viewing angle compensator having negative biaxial optical anisotropy disposed so as to be orthogonal to the absorption axis of the two polarizing plates; A white light source disposed on the opposite side of the second polarizing plate from the second transparent substrate, and a total retardation Rthall in a thickness direction other than the liquid crystal layer in the liquid crystal display element is 250 nm. ≦ Rthall ≦ 700 nm, the retardation Re in the in-plane direction of the first and second viewing angle compensators is 5 nm ≦ Re ≦ 30 nm, and the retardation Δnd of the liquid crystal layer is 1.08 × Rthall ≦ Δnd ≦ 1.43 × Rthall, the liquid crystal display element is illuminated with the white light source, and the chromaticity when observed from the normal direction of the first transparent substrate is x0, y0, and the second polarizing plate X0-0.02 ≦ x ≦, where x and y are the chromaticities when observed from the direction of 50 ° to the normal direction of the first transparent substrate in the direction of 45 ° with the absorption axis of A liquid crystal display device in which x0 + 0.02 and y0−0.02 ≦ y ≦ y0 + 0.02 is provided.

ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which can implement | achieve favorable display can be provided.

  The inventor of the present application fixed the thickness direction retardation Rth of the negative biaxial film 14 b to 200 nm in the liquid crystal display element structure shown in FIG. 8, the in-plane retardation Re of the negative biaxial film 14 b, and the liquid crystal layer 13. A simulation analysis was performed on the viewing angle characteristics in the left-right direction (180 ° -0 ° direction) when no voltage was applied when the retardation Δnd was changed.

  For the simulation, a liquid crystal display simulator LCD MASTER6 manufactured by Shintech Co., Ltd. was used. The polarizing layers 14a and 15a of the upper polarizing plate (polarizing plate with viewing angle compensation plate) 14 and the lower polarizing plate 15 were formed by SHC13U manufactured by Polatechno Co., Ltd. The absorption axis of the polarizing layer 14a of the upper polarizing plate 14 was 135 ° azimuth, and the in-plane slow axis of the negative biaxial film 14b formed of a norbornene-based cyclic olefin resin was 45 ° azimuth perpendicular to this. The TAC film 15b of the lower polarizing plate 15 has a retardation in the thickness direction of about 50 nm and an in-plane retardation of about 3 nm, and the in-plane slow axis is arranged parallel to the absorption axis of the polarizing layer 15a (45 ° azimuth). He said.

  The pretilt angle in the liquid crystal layer 13 of the monodomain vertical alignment type liquid crystal cell 10 was about 89 °. Further, when a voltage is applied, the liquid crystal molecules in the central portion in the thickness direction of the liquid crystal layer 13 are inclined downward (270 ° azimuth) where the angle formed by the absorption axes of the upper and lower polarizing plates 14 and 15 is approximately 45 °. Antiparallel orientation was adopted. Furthermore, a standard light source C (white light source) was used as the light source of the backlight 20 disposed below the lower polarizing plate 15 (on the side opposite to the liquid crystal cell 10).

  The optimum conditions of the prior art in the liquid crystal display element structure shown in FIG. 8 are that the in-plane retardation Re is about 65 nm and the retardation Δnd of the liquid crystal layer 13 when the thickness direction retardation Rth of the negative biaxial film 14b is 200 nm. Is about 280 nm.

  FIG. 1 is an xy chromaticity diagram showing simulation results. In this figure, the in-plane retardation Re of the negative biaxial film 14b is set variously, and the polar angle 50 ° of the right direction (0 ° direction) that is 45 ° to the absorption axis direction of the polarizing layer 15a. The dependence of the xy chromaticity on the liquid crystal layer 13 retardation Δnd when observed from the direction was shown.

  In the figure, the horizontal axis indicates x chromaticity coordinates, and the vertical axis indicates y chromaticity coordinates. Curves a, b, c, d, e, and f show the simulation results when the in-plane retardation Re of the negative biaxial film 14b is 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, and 50 nm, respectively. A curve g is a result obtained by performing a simulation on a liquid crystal display element in which a C plate (a norbornene-based cyclic olefin film of Rth = 200 nm) is arranged instead of the negative biaxial film 14b.

  The chromaticity when the liquid crystal display element was observed from the front (in the normal direction of the substrate) was x = 0.310 and y = 0.306. In this figure, the range within ± 0.02 centered on the chromaticity coordinates at the time of frontal observation is represented by a square periphery and an inner region. Under the Re and Δnd conditions included in this region, coloring is hardly observed, and a relatively neutral light leakage state is obtained.

  For all the curves a to g, as the retardation Δnd of the liquid crystal layer 13 was increased, the combination of the x chromaticity coordinates and the y chromaticity coordinates moved from the upper right to the lower left on the chromaticity diagram. That is, in all the Re conditions, when Δnd is small, both the x value and the y value are large, and as the Δnd increases, the x value and the y value tend to decrease. As is clear from this figure, the smaller Re is, the smaller the change in x value and y value due to Δnd is, and the x value and y value change in the vicinity where the achromatic color display can be realized (in the vicinity of the square area). become.

  FIG. 2 is a graph showing the Δnd dependence of the light transmittance for each Re value when observed from the right angle (0 ° azimuth) polar angle 50 ° direction. The horizontal axis of the graph indicates the retardation Δnd of the liquid crystal layer 13 in the unit “nm”, and the vertical axis indicates the light transmittance in the right azimuth polar angle 50 ° observation in the unit “%”.

  Curves a, b, c, d, and e show Δnd dependency when the in-plane retardation Re of the negative biaxial film 14b is 10 nm, 15 nm, 20 nm, 30 nm, and 40 nm, respectively. Curve g shows light transmission when observing Δnd and right polar angle of 50 ° for a liquid crystal display element in which a C plate (Rth = 200 nm norbornene-based cyclic olefin film) is arranged instead of the negative biaxial film 14b. The relationship with the rate is shown. Furthermore, the hatched area in this figure is an area included in the circumference and the inner area of the square in FIG. That is, a region that is included within a range of ± 0.02 around the chromaticity coordinates at the time of front viewing of the liquid crystal display element, and that is a region in which coloring is not observed and a relatively neutral light leakage state is obtained. Show.

  Comparing the hatched area on the negative biaxial film 14b (curves a to e) with that on the C plate (curve g), the light transmittance in the former is the light transmittance in the latter, regardless of the value of Δnd. The rate is 2/3 or less. In the case of Re> 15 nm, the light transmittance in the hatched area on the negative biaxial film 14b is ½ or less of the light transmittance in the hatched area on the C plate.

  Referring to this figure, when the chromaticity when observed from the direction of right azimuth polar angle 50 ° is within ± 0.02 centered on the chromaticity at the time of front observation, and when observed from the direction of right azimuth polar angle 50 ° The Re and Δnd conditions for setting the light transmittance to about 2/3 or less in the case of a liquid crystal display device in which a C plate (Rth = 200 nm norbornene-based cyclic olefin film) is arranged instead of the negative biaxial film 14b are: It can be considered that approximately 5 nm ≦ Re ≦ 40 nm and 310 nm ≦ Δnd <350 nm. In this range, it is possible to realize a good display in which coloring and light leakage are suppressed.

  It can be considered that more preferable Re and Δnd conditions for setting the light transmittance to about ½ or less are approximately 15 nm <Re <30 nm and 310 nm ≦ Δnd <335 nm. In this range, better display can be realized.

  By the way, in the liquid crystal display element subjected to the simulation analysis, the thickness direction retardation expression elements other than the liquid crystal layer 13 are the optical compensator (negative biaxial film 14b, Rth = 200 nm) and the TAC film of the lower polarizing plate 15. 15b (Rth = 50 nm), and the sum of these (thickness direction retardation by optical compensation element: Rthall) is 250 nm.

  When describing the preferable range of Δnd using Rthall, 310 nm ≦ Δnd <350 nm is expressed as 1.24 × Rthall <Δnd <1.40 × Rthall, and 310 nm ≦ Δnd <335 nm is set to 1.24 × Rthall < It may be expressed as Δnd <1.34 × Rthall.

  FIG. 3 shows that in the liquid crystal display element (Rth = 200 nm) subjected to simulation analysis, the in-plane retardation Re of the negative biaxial film 14b is 25 nm, and the retardation Δnd of the liquid crystal layer 13 is about 320 nm (about 1.28 Rthall). For the liquid crystal display device in which the C plate (Rth = 200 nm norbornene-based cyclic olefin film) is arranged in place of the negative biaxial film 14b and the retardation Δnd of the liquid crystal layer 13 is about 280 nm, It is a graph which shows the transmittance | permeability spectrum observed from the polar angle 50 degree direction.

  The horizontal axis of the graph represents the wavelength of light in the unit “nm”, and the vertical axis of the graph represents the light transmittance in the unit “%”. Curves a and b respectively show the liquid crystal display element (Rth = 200 nm, Re = 25 nm, Δnd = 320 nm) as the object of simulation analysis when observed from the right azimuth polar angle 50 ° direction and the left azimuth polar angle 50 °. The transmittance when observed from the direction is shown. Curves c and d are for a liquid crystal display element in which a C plate (Rth = 200 nm norbornene-based cyclic olefin film) is arranged in place of the negative biaxial film 14b, and the retardation Δnd of the liquid crystal layer 13 is about 280 nm. Show them.

  In the case of the negative biaxial film (curves a and b) and in the case of the C plate (curves c and d), there is a difference in the left-right transmittance spectrum due to the influence of the pretilt angle, but the light transmittance is wide in a wide wavelength range. Is almost flat. From this, it is understood that the light omission state is an achromatic color.

  In the right direction, the light transmittance of the negative biaxial film (curve a) is 0.236%, and that of the C plate (curve c) is 0.586%. In the left direction, the light transmittance in the case of the negative biaxial film (curve b) is 0.286%, and in the case of the C plate (curve d), it is 0.653%. Thus, it was confirmed that the light transmittance (light leakage) can be reduced to ½ or less in the liquid crystal display element using the negative biaxial film as compared with the liquid crystal display element using the C plate. It was.

  Next, the inventor of the present application relates to the liquid crystal display element subjected to simulation analysis and the liquid crystal display element in which the retardation Rth in the thickness direction of the biaxial film 14b of the upper polarizing plate 14 is 350 nm. The relationship between Re and Δnd / Rthall in which the chromaticity at the time of azimuth polar angle 50 ° observation is within ± 0.02 of the chromaticity at the time of frontal observation (x = 0.310, y = 0.306) was examined. .

  FIG. 4 shows the analysis results. 4 represents the in-plane retardation Re of the negative biaxial film 14b of the upper polarizing plate 14 in the unit of “nm”. The vertical axis represents the ratio (Δnd / Rthall) of the retardation Δnd of the liquid crystal layer 13 and the total sum Rthall of the retardation in the thickness direction by the optical compensation element in arbitrary units. The hatched area in the figure indicates a range where the chromaticity when observed in the direction of the right polar angle of 50 ° is within ± 0.02 of the chromaticity when viewed from the front.

  From the results shown in this figure, it can be seen that when the retardation Rth in the thickness direction is large, the range of Re and Δnd at which good display is possible becomes small.

  In addition, when 200 nm ≦ Rth ≦ 350 nm, that is, 250 nm ≦ Rthall ≦ 400 nm, when 5 nm ≦ Re ≦ 40 nm and 1.12 × Rthall ≦ Δnd ≦ 1.40 × Rthall are satisfied, the right polar angle is observed in the 50 ° direction. It can be seen that the chromaticity of is within ± 0.02 of the chromaticity during frontal observation.

  In the simulation analysis whose results are shown in FIG. 1 to FIG. 4, the liquid crystal display element structure shown in FIG. In the liquid crystal display element structure shown in FIG. 8, the same result is obtained when a polarizing plate including a polarizing layer and a TAC film is used as an upper polarizing plate and a polarizing plate with a viewing angle compensation plate is used as a lower polarizing plate. Can do.

  Further, the inventor of the present application also performs the same analysis on the liquid crystal display element structure shown in FIG. 5, that is, the liquid crystal display element shown in FIG. 9, in which the C plate 17 is replaced with the negative biaxial film 18. It was.

  As a result, FIG. 8 shows both the case where Rth of the negative biaxial plate 18 is 150 nm and Rthall is 250 nm, and the case where Rth of the negative biaxial plate 18 is 300 nm and Rthall is 400 nm. It was confirmed that suitable conditions substantially equivalent to suitable conditions (for example, suitable conditions for Rthall, Re, and Δnd) obtained by simulation analysis for the liquid crystal display element structure were obtained.

  Subsequently, the inventor of the present application also conducted a similar study on the liquid crystal display element having the structure shown in FIG. 6, with a chromaticity of ± 0. The relationship between Rthall, Re, and Δnd falling within the range of 02 was analyzed by simulation.

  Compared to that shown in FIG. 8, the liquid crystal display element shown in FIG. 6 is replaced with the lower polarizing plate 15 including the polarizing layer 15a and the TAC film 15b, and the lower polarizing plate including the polarizing layer 19a and the negative biaxial film 19b. The difference is that (polarizing plate with viewing angle compensation plate) 19 is provided. Further, the absorption axis direction of the polarizing layer 14a of the upper polarizing plate 14 and the in-plane slow axis direction of the negative biaxial film 14b are also different. However, also in the liquid crystal display element shown in FIG. 6, the upper and lower polarizing plates 14 and 19 are arranged in crossed Nicols.

  In the liquid crystal display element shown in FIG. 6, the absorption axis of the polarizing layer 14a of the upper polarizing plate 14 is arranged at 45 ° azimuth, and the in-plane slow axis of the negative biaxial film 14b is arranged at 135 ° azimuth perpendicular thereto. The Further, the absorption axis of the polarizing layer 19a of the lower polarizing plate 19 is arranged in the 135 ° azimuth, and the in-plane slow axis of the negative biaxial film 19b is arranged in the 45 ° azimuth perpendicular thereto.

  The upper polarizing plate 14 and the lower polarizing plate 19 have the same optical parameters. Also in the liquid crystal display element shown in FIG. 6, a backlight 20 having a white light source is disposed below the lower polarizing plate 19. A standard light source C was used as the light source.

  FIG. 7 mainly shows the chromaticity during frontal observation when the thickness direction retardation Rth of the negative biaxial films 14b and 19b of the upper and lower polarizing plates 14 and 19 is set to 125 nm, 220 nm, and 350 nm. The range of combinations of Re and Δnd / Rthall that fall within ± 0.02 is indicated by hatching.

  As in the case of the liquid crystal display element structure shown in FIG. 8, the range of Re and Δnd at which good display is possible decreases as the retardation Rth in the thickness direction increases.

  From the results shown in this figure, if 250 nm ≦ Rthall ≦ 700 nm, 5 nm ≦ Re ≦ 30 nm, 1.08 × Rthall ≦ Δnd ≦ 1.43 × Rthall, the chromaticity difference is within 0.02 from that at the front observation, It can be seen that an almost achromatic display can be obtained.

  In addition, in the liquid crystal display element structure shown in FIG. 6, the inventor of the present application is between the polarizing layer 14a and the negative biaxial film 14b and / or between the polarizing layer 19a and the negative biaxial film 19b. Analysis was also performed for the case where the TAC film was disposed, and a result almost equivalent to the result shown in FIG. 7 was obtained.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  For example, in the example, the standard light source C was used as the light source, but the same result was obtained when the standard light source D65 was used. That is, at least when the light source is white, it has been found that the above-described preferable optical parameter range is effective.

  In the embodiment, a liquid crystal display element including a liquid crystal layer having a monodomain alignment and an antiparallel alignment without a twisted structure between the upper and lower substrates is a simulation target, but is not limited thereto. A chiral material may be added in the liquid crystal layer, or an alignment treatment may be performed on the glass substrate so as to take a twisted structure between the upper and lower substrates. Further, a multi-domain structure in which liquid crystal molecules have a plurality of orientation directions when a voltage is applied may be adopted.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be used in general for liquid crystal display elements and liquid crystal display devices. For example, the present invention can be suitably used for an in-vehicle information display device that performs segment display or both segment display and dot matrix display, a display unit for car audio, an operation panel display unit such as a copy machine, and other information display panels.

It is an xy chromaticity diagram showing a simulation result. It is a graph which shows (DELTA) nd dependence of the light transmittance at the time of observing from the right angle (0 degree azimuth | direction) polar angle 50 degree direction about each Re value. When the in-plane retardation Re of the negative biaxial film 14b is set to 25 nm and the retardation Δnd of the liquid crystal layer 13 is set to about 320 nm (about 1.28 Rthall) in the liquid crystal display element (Rth = 200 nm) subjected to the simulation analysis, A liquid crystal display element in which a C plate (Rth = 200 nm norbornene-based cyclic olefin film) is disposed in place of the negative biaxial film 14b and the retardation Δnd of the liquid crystal layer 13 is about 280 nm is used. 5 is a graph showing a transmittance spectrum observed from the ° direction. It is a figure which shows an analysis result. 9 shows a liquid crystal display element having a structure in which the C plate 17 is replaced with a negative biaxial film 18 in the liquid crystal display element of FIG. In the liquid crystal display device shown in FIG. 8, instead of the lower polarizing plate 15 including the polarizing layer 15a and the TAC film 15b, the lower polarizing plate (polarizing plate with viewing angle compensation plate) including the polarizing layer 19a and the negative biaxial film 19b. 19 is a liquid crystal display element. When the thickness direction retardation Rth of the negative biaxial films 14b and 19b of the upper and lower polarizing plates 14 and 19 is set to 125 nm, 220 nm, and 350 nm, the chromaticity at the time of frontal observation is set to ± 0. The range of combinations of Re and Δnd / Rthall that fall within 02 is shown. A structure of a liquid crystal display element to be simulated is shown. The liquid crystal display element structure shown by patent document 1 is shown. 10 is a graph showing a spectral spectrum when no voltage is applied in the liquid crystal display element having the structure shown in FIGS. 8 and 9. 8A shows a spectral spectrum when the liquid crystal display element of FIG. 8 is observed from the polar angle of 50 °, and FIG. 9B shows that of the liquid crystal display element of FIG.

Explanation of symbols

10 Monodomain vertical alignment type liquid crystal cell 11 Upper glass substrate 12 Lower glass substrate 13 Liquid crystal layer 14 Upper polarizing plate (polarizing plate with viewing angle compensation plate)
14a Polarizing layer 14b Negative biaxial film 15 Lower polarizing plate 15a Polarizing layer 15b TAC film 16 Upper polarizing plate 16a Polarizing layer 16b TAC film 17 C plate 18 Negative biaxial film 19 Lower polarizing plate (polarizing plate with viewing angle compensation plate) )
19a Polarizing layer 19b Negative biaxial film 20 Backlight

Claims (2)

First and second transparent substrates;
A vertically aligned liquid crystal layer sandwiched between the first and second transparent substrates and having a retardation Δnd of less than 350 nm ;
A first polarizing plate disposed on a side opposite to the liquid crystal layer of the first transparent substrate;
A second polarizing plate disposed on the side opposite to the liquid crystal layer of the second transparent substrate, in a crossed Nicol manner with the first polarizing plate;
Between the first polarizer and the first transparent substrate or, either one of between the second transparent substrate and the second polarizing plate, the in-plane slow axis, said first 1, a liquid crystal display element having a viewing angle compensator having negative biaxial optical anisotropy disposed so as to be orthogonal to the absorption axis of the adjacent polarizing plate among the second polarizing plates;
A white light source disposed on the opposite side of the second polarizing plate from the second transparent substrate,
The total retardation Rthall in the thickness direction other than the liquid crystal layer in the liquid crystal display element is 250 nm ≦ Rthall ≦ 400 nm,
The retardation Re in the in-plane direction of the viewing angle compensation plate is 5 nm ≦ Re ≦ 40 nm,
The retardation Δnd of the liquid crystal layer is 1.24 × Rthall < Δnd ≦ 1.40 × Rthall,
The liquid crystal display element is illuminated with the white light source, and the chromaticity when observed from the normal direction of the first transparent substrate is x0, y0, and forms 45 ° with the absorption axis of the second polarizing plate. In azimuth, x0−0.02 ≦ x ≦ x0 + 0.02 and y0− when the chromaticity when observed from the direction that forms 50 ° with the normal direction of the first transparent substrate is x and y A liquid crystal display device satisfying 0.02 ≦ y ≦ y0 + 0.02. First and second transparent substrates;
The sandwiched between first and second transparent substrates, a liquid crystal layer retardation Δnd is vertical orientation below 350 nm,
A first polarizing plate disposed on a side opposite to the liquid crystal layer of the first transparent substrate;
A second polarizing plate disposed on the side opposite to the liquid crystal layer of the second transparent substrate, in a crossed Nicol manner with the first polarizing plate;
Negative biaxial optical anisotropy arranged between the first transparent substrate and the first polarizing plate so that an in-plane slow axis is perpendicular to the absorption axis of the first polarizing plate A first viewing angle compensator having
Negative biaxial optical anisotropy disposed between the second transparent substrate and the second polarizing plate so that an in-plane slow axis is perpendicular to the absorption axis of the second polarizing plate A liquid crystal display element having a second viewing angle compensation plate having a property;
A white light source disposed on the opposite side of the second polarizing plate from the second transparent substrate,
In the liquid crystal display element, the total sum Rthall of retardations in the thickness direction other than the liquid crystal layer is 250 nm ≦ Rthall ≦ 700 nm,
The retardation Re in the in-plane direction of the first and second viewing angle compensation plates is 5 nm ≦ Re ≦ 30 nm,
The retardation Δnd of the liquid crystal layer is 1.08 × Rthall ≦ Δnd ≦ 1.43 × Rthall,
The liquid crystal display element is illuminated with the white light source, and the chromaticity when observed from the normal direction of the first transparent substrate is x0, y0, and forms 45 ° with the absorption axis of the second polarizing plate. In azimuth, x0−0.02 ≦ x ≦ x0 + 0.02 and y0− when the chromaticity when observed from the direction that forms 50 ° with the normal direction of the first transparent substrate is x and y A liquid crystal display device satisfying 0.02 ≦ y ≦ y0 + 0.02.

Images