JP2002236297A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has an excellently symmetric luminance distribution as well as a high-speed response characteristics based on bend alignment. SOLUTION: In a liquid crystal display device equipped with a liquid crystal panel 100 which holds a liquid crystal layer 4 between a pair of opposed transparent substrates 1 and 2, applies a voltage to the liquid crystal layer 4 to put the liquid crystal layer 4 in a bend alignment state, and performs display by changing the alignment state between a first voltage and a second voltage higher than the first voltage, and an illuminator 200 which illuminates the liquid crystal panel 100 from a panel back surface, the liquid crystal layer 4 has a twisted alignment of the liquid crystal layer when the first voltage is applied in the thickness direction of the liquid crystal layer 4. The illuminator 200 has a luminance distribution which compensates the asymmetry of the transmittance distribution of the liquid crystal panel 100 generated in the direction along which liquid crystal molecules in the central part of the liquid crystal layer is inclined by the twist.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having excellent symmetry of viewing characteristics.

[0002]

2. Description of the Related Art At present, TN (Twisted Nema) is used.
tic) mode, IPS (In-Plane Switch)
hing) mode, VA (Vertical Alig)
An active matrix type liquid crystal display device using a display method such as a liquid crystal display (nent) mode is mass-produced. As these liquid crystal display devices have expanded their application range to applications mainly for displaying moving images such as televisions and multimedia monitors, improvement of response speed has become an important issue. As a display method for realizing a high-speed response, OCB (Optic) has already been used.
All Compensated Bend) mode has been proposed. Regarding the OCB mode, see the literature (Y. Yamaguchi et al., SID93DIGES).
T, p. 277; Miyashita et al.
EuroDisplay93, p. 149).

FIG. 14 shows a configuration of a liquid crystal panel according to a conventional OCB mode system. In the figure, 1 is an electrode substrate, 2
Is a counter substrate. Pixels are formed in a matrix on the electrode substrate 1, and a TFT as a switching element is provided for each pixel.
(Thin Film Transistor) is provided. The opposite substrate 2 has RGB for color display.
A color filter for each color is provided. Reference numeral 3 denotes an alignment film. The alignment film 3 has been subjected to a rubbing treatment. The rubbing direction is substantially parallel between the upper and lower substrates. 4 is a liquid crystal layer, 5 and 6 are optical compensation films, and 7 and 8 are polarizing plates.

In the OCB mode, a p-type liquid crystal having a positive dielectric anisotropy is used. The alignment state is a bend alignment, and a voltage is applied between a pixel electrode provided on the electrode substrate 1 and a counter electrode provided on the counter substrate 2 to change the alignment state. The transmittance is controlled by a change in retardation of the liquid crystal layer 4 accompanying a change in alignment between a first voltage (off voltage) other than 0V and a second voltage (on voltage) higher than the first voltage (off voltage). A case where a film that compensates for the liquid crystal layer retardation when the off voltage is applied is attached so that a black display is obtained when the off voltage is applied is called normally black, and conversely, an on voltage is applied so that the black display is obtained when the on voltage is applied. The case where a film for compensating for the liquid crystal layer retardation at the time is attached is called normally white. Normally white is normally used because normally white has less retardation of the liquid crystal layer during black display and is less susceptible to temperature changes. The response time of the OCB mode is 10 ms or less between all display gradations, and is shorter than the time of one frame of 60 Hz scanning of 16.7 ms. In the OCB mode, backflow does not occur in the liquid crystal layer during response,
It is thought that it has a high-speed response characteristic in principle.

[0005] Further, in the OCB mode, a wide viewing angle characteristic can be obtained at the same time as a high-speed response characteristic by combining the optical compensation films 5 and 6 specially designed. FIG. 15 shows an example of the configuration of the optical compensation film. FIG. 15 shows only the opposing substrate half of the liquid crystal layer 4 and the optical compensation film 6 on the opposing substrate. The configuration of the optical compensation film 5 on the electrode substrate side is the same as that on the counter substrate side. The optical compensation film 6 includes a discotic liquid crystal film 61 having a hybrid orientation, a c-plate 62, and a monoaxial film (or a biaxial film).
63. The liquid crystal molecules 41 near the substrate interface of the liquid crystal layer 4 have a director distribution of a hybrid alignment type, and this is compensated for by a discotic liquid crystal film 61 having a hybrid alignment. Liquid crystal molecules 4 near the center of the liquid crystal layer
2 are oriented almost vertically, which is compensated by the c-plate 62. Further, a uniaxial film or a biaxial film 63 is used in order to reduce light leakage in the oblique direction of the polarizing plate 8 arranged in crossed Nicols. Optical compensation film 6
Is the case where a c-plate and a uniaxial film (or a biaxial film) are replaced with one biaxial film, or a biaxial film is replaced with a single biaxial film in addition to the configuration shown in the figure. There is also. In any case, it is reported that a viewing angle of 160 ° or more in the vertical and horizontal directions can be realized.

As described above, the OCB mode is a very promising display method for a liquid crystal display device mainly for displaying moving images, which can simultaneously realize a high-speed response and a wide viewing angle. However, in order to obtain the bend alignment used in the OCB mode, a transition from the splay alignment in the initial state to the bend alignment is required. FIG. 16 shows a state of an alignment change in a liquid crystal panel according to a conventional OCB mode method. In the OCB mode, a rubbing process is generally performed in a direction substantially parallel to the alignment films of the electrode substrate and the counter substrate. Therefore, the splay orientation (FIG. 16A) is most stable when no voltage is applied. When a voltage is applied, the liquid crystal molecules rise as shown in FIG.
Transition to the bend orientation shown in (c). For this bend transition, a high voltage of 10 V or more needs to be applied for a long time (several minutes to several tens of minutes). When the applied voltage is reduced after the bend transition,
After the twist orientation (FIG. 16 (e)), the film transitions to the splay orientation (FIG. 16 (f)). The transition from the bend alignment to the twist alignment is continuous, and if the applied voltage is increased again, the state easily returns to the bend alignment. On the other hand, if a splay transition has occurred, a high voltage must be applied again to return to the bend orientation. Therefore, it is necessary to always apply a voltage higher than the voltage at which the spray transition does not occur. Spray transition voltage (called Vcr)
Depends on the physical properties of the liquid crystal material, the pretilt angle, and the like, but is approximately in the range of 2.0 V to 2.5 V. So OC
In the B mode, a voltage equal to or higher than Vcr is set as an off voltage, and as shown in FIGS. 16C and 16D, the orientation state of the bend orientation is changed between the off voltage and an on voltage higher than the off voltage. The display is performed while changing the transmittance.

As described above, in the display by the OCB mode method, it is necessary to apply a high voltage to cause the bend transition.
The driving voltage of the liquid crystal display device in each mode of S and VA is 5 V or less, and it is difficult to apply a high voltage of 10 V or more to the pixel. It takes a long time for the transfer to be a practical problem. There is also a problem that it is difficult to bend-transfer all one million or more pixels arranged in a matrix.

[0008] In response to these bend transition problems,
The rubbing direction applied to each of the alignment films of the electrode substrate and the counter substrate is shifted from the parallel direction by several to 30 °, so that the rubbing direction is changed from the splay alignment (more precisely, the splay alignment having a twist angle of several to 30 °). Japanese Patent Application Laid-Open No. 8-87013 discloses that transition to bend orientation is likely to occur.
And JP-A-9-105957.
In Japanese Patent Application Laid-Open No. H11-7018, the rubbing direction is parallel, but by adding a small amount of a chiral agent to the liquid crystal layer, the transition from the splay alignment to the bend alignment can be performed at a low voltage while the initial alignment is the splay alignment. It has been reported to occur in a short time. Japanese Patent Application Laid-Open Nos. 9-96790 and 11-7018 disclose that a chiral agent is added in a large amount to a liquid crystal so that the initial alignment is about 180 °.
It has been proposed to change the twist orientation continuously to bend orientation (or an orientation state similar to bend orientation) by applying a voltage. According to this method, it is not necessary to apply a high voltage for a long time for the bend transition treatment, the bend orientation can be easily obtained, and the OCB
High-speed response characteristics equivalent to the mode can be obtained.

[0009]

The conventional liquid crystal display device using the OCB mode display system is constructed as described above. The liquid crystal panel is constructed by introducing a chiral agent or by rubbing the rubbing direction from the parallel direction. , There is no need to apply a high voltage for bend transition,
A new problem arises in that the symmetry of the viewing angle characteristic is lost. In normally white, as described above, the compensation film is designed to compensate for the retardation of the liquid crystal layer during black display (when an ON voltage is applied). The asymmetry of characteristics becomes remarkable. As an example, FIG. 17A shows the transmittance distribution of the liquid crystal panel in the OCB mode mode in which no chiral agent is added during white display (when an off voltage is applied), and FIG. The transmittance distribution at the time of white display (at the time of applying an off-voltage) of the liquid crystal panel in the OCB mode mode in which the orientation is twisted by 180 ° is shown. FIG. 17 shows the transmittance distribution as viewed from the front of the panel. Rubbing treatment is 2
In each of the panels, the direction shown by the arrow in FIG. 17 is the rubbing direction applied to the alignment film of each of the electrode substrate and the counter substrate is parallel. The transmittance distribution when the chiral agent is not added (FIG. 17A) is almost symmetrical in the left-right direction and the vertical direction, whereas the transmittance distribution when the chiral agent is added (FIG. 17B) ) Indicates that the symmetry in the left-right direction, that is, the direction orthogonal to the rubbing direction, is significantly impaired.

It is considered that the cause of the loss of the transmittance symmetry is that the stability of the twist alignment in the liquid crystal layer is increased by shifting the rubbing direction or adding a chiral agent. FIGS. 18A and 18B schematically show the orientation states when white display is performed (when an off voltage is applied) when the chiral agent is not added and when the chiral agent is added. When the stability of the twist alignment is high, as shown in FIG. 18B, the alignment of the liquid crystal layer when the off-voltage is applied is twisted in the thickness direction of the liquid crystal layer, and the liquid crystal molecules in the center of the liquid crystal layer are twisted. Is tilted in the direction perpendicular to the rubbing direction and does not rise sufficiently. Therefore, the symmetry of the liquid crystal layer is reduced in the viewing angle direction perpendicular to the rubbing direction.

An asymmetric transmittance distribution when the liquid crystal molecules in the center of the liquid crystal layer do not rise sufficiently will be described. In FIGS. 19A and 19B, the orientation state of the liquid crystal layer when the off-voltage is applied and the refractive index ellipsoid corresponding to the liquid crystal layer in the case where the chiral agent is not added and the case where the chiral agent is added are oblique to the front of the liquid crystal panel. 2 shows a cross section when viewed from the side. FIG.
(A) and (B), (a-1) and (b-1) show the alignment state of the liquid crystal layer when an off-voltage is applied, and (a-2) and (b-).
2) is a cross section of the refractive index ellipsoid in the liquid crystal molecules near the liquid crystal layer interface and near the center when viewed from the front of the liquid crystal panel, and (a-3) (a-4), (b-3) (b- 4) is a cross section when the liquid crystal panel is viewed obliquely. In the sectional view of the refractive index ellipsoid, the rubbing direction is downward when viewed from the front of the liquid crystal panel (the direction of the arrow in FIG. 19). When the liquid crystal panel to which the chiral agent is not added is viewed from the front (FIG. 19 (a-2)), the birefringence such that the phase in the rubbing direction is delayed because the liquid crystal molecules are inclined except for the liquid crystal molecules at the center of the liquid crystal layer. Properties and transmit light. When this is viewed from an oblique right or left direction perpendicular to the rubbing direction (FIGS. 19 (a-3) and (a-4)), the birefringence is lower than when viewed from the front. , Since the change is the same, the transmittance distribution becomes symmetric in the left-right direction. On the other hand, when a chiral agent is added, for example, when a left-chiral liquid crystal is used, the liquid crystal molecules in the center of the liquid crystal layer are tilted in a direction perpendicular to the rubbing direction (left direction) when an off voltage is applied. When viewed, the retardation of the liquid crystal layer decreases (FIG. 19 (b-3)), and increases when viewed obliquely from the left (FIG. 19 (b-4)). Therefore, the transmittance of the right diagonal decreases and the transmittance of the left diagonal increases,
The transmittance distribution becomes asymmetric in the left-right direction.

The change in the transmittance distribution when the chiral agent is added has been described above. However, the same phenomenon occurs when the rubbing direction is shifted from parallel without adding the chiral agent. That is, if the rubbing direction is shifted from the parallel direction, the clockwise or counterclockwise twist angle becomes smaller than 180 °, and the twist orientation is stabilized. As a result, the orientation of the liquid crystal layer is twisted when the off-voltage is applied, and the liquid crystal molecules in the central portion of the liquid crystal layer do not rise sufficiently, and are inclined in a direction perpendicular to the middle of the two intersecting rubbing directions. Therefore, the symmetry of the viewing angle characteristic is impaired by the same mechanism as described above.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a liquid crystal display device having a luminance distribution excellent in symmetry in addition to a high-speed response characteristic by bend alignment. I do.

[0014]

According to a liquid crystal display device of the present invention, a liquid crystal layer is sandwiched between a pair of opposing transparent substrates, and a voltage is applied to the liquid crystal layer to bring the liquid crystal layer into a bend alignment state. A liquid crystal panel that performs display by changing the transmittance by changing the alignment state between a first voltage and a second voltage higher than the first voltage, and an illuminating device that illuminates the liquid crystal panel from the back of the panel In the liquid crystal display device, the liquid crystal layer has a first direction in a thickness direction of the liquid crystal layer.
There is a twist in the orientation of the liquid crystal layer when the voltage is applied, and the lighting device compensates for the asymmetry of the transmittance distribution of the liquid crystal panel, which is generated in the direction in which the liquid crystal molecules are inclined in the center of the liquid crystal layer due to the twist. This is a configuration having a luminance distribution.

Further, in the liquid crystal display device according to the present invention, in the above liquid crystal display device, the luminance center of the illuminating device is 5 to 5 which is opposite to the direction in which the liquid crystal molecules are inclined at the center of the liquid crystal layer with respect to the front direction of the liquid crystal panel. In the direction of 20 °.

Further, in the liquid crystal display device according to the present invention, in the above liquid crystal display device, the liquid crystal layer is in a twist alignment state having a twist angle of 180 ° to 240 ° when no voltage is applied.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an exploded view showing a configuration of a liquid crystal display device according to Embodiment 1 of the present invention. In the figure, the upper part is a liquid crystal panel unit 100,
1 is an electrode substrate, 2 is a counter substrate, and 3 is an alignment film provided on the electrode substrate 1 and the counter substrate 2, respectively. The alignment film 3 is subjected to a rubbing treatment, and the rubbing direction is substantially parallel between the upper and lower substrates. 4 is a liquid crystal layer, 5 and 6 are optical compensation films, and 7 and 8 are polarizing plates. The lower part of FIG. 1 shows a lighting unit 200 that illuminates the liquid crystal panel unit 100 from the back of the panel.
9 is a lamp, 10 is a light guide plate, 11 is a reflection film, 12 and 13 are diffusion films, and 14 and 15 are directional films. In the first embodiment, a lighting device having a luminance distribution that compensates for the asymmetric transmittance distribution of the liquid crystal panel unit 100 is used as the lighting device unit 200. That is, the directional film 1 having a light condensing function in a specific direction
4, 15 or a reflection film 11 having a reflection function in a specific direction is used. As the directional films 14 and 15 having a light condensing function in a specific direction, for example, one side,
Alternatively, a prism sheet having a prism structure inclined on both sides is used. FIG. 2A shows the structure of a prism sheet having an inclined prism structure. 16 is an inclined prism, 17 is a base material. As the reflection film 11 having a reflection function in a specific direction, for example, a reflection sheet having an inclined uneven structure as shown in FIG. 2B is used. Reference numeral 18 denotes an inclined reflection film having an inclined uneven structure.

Hereinafter, the configuration of the liquid crystal display device according to the present embodiment will be described in detail. In the first embodiment, the liquid crystal panel unit 100 has an initial orientation of the liquid crystal layer 4 having a twist angle of 180 degrees.
The one having a twist orientation of ° was used. JS for alignment film 3
Using a soluble polyimide AL3046 made by R, parallel rubbing was performed on both the alignment film 3 on the electrode substrate 1 side and the alignment film 3 on the counter substrate 2 side downward as viewed from the front of the panel. Thereafter, the panel gap was adjusted to 7.5 using a 7.5 μm spherical spacer (Micropearl manufactured by Sekisui Fine Chemical).
It was adjusted to μm. As the liquid crystal, a chiral nematic liquid crystal to which a chiral agent was added was used. The physical properties are shown in Table 1.

[0019]

[Table 1]

The chiral pitch p of the liquid crystal is 25 μm.
However, in order to set the initial orientation to the twist orientation, the chiral pitch p may be within the range represented by the formula (1).

[0021]

(Equation 1)

More preferably, the range of equation (2) is good.

[0023]

(Equation 2)

If the chiral pitch p is within the range of the formula (1), the initial orientation is a twist orientation. However, as the pitch is shorter, the twist orientation becomes more stable. The molecules are more difficult to rise, and the symmetry of the transmittance distribution is worsened. Conversely, if the pitch is too close to the upper limit, the initial alignment may be splay alignment due to uneven cell gap or uneven structure in the pixel, and a bend transition process may be required.

Although the chiral direction of the chiral agent added to the liquid crystal is the left chiral, the chiral agent may of course be the right chiral. On the outer surfaces of the electrode substrate 1 and the opposing substrate 2, laminated optical compensation films 5, 6 composed of a discotic liquid crystal film having a hybrid orientation, a c-plate, and a uniaxial film, and polarizing plates 7, 8 were adhered. The front retardation of each of the optical compensation films 5 and 6 was 50 nm, and the optical retardation films 5 and 6 each had a front retardation of 100 nm. The drive voltage was an off voltage of 2.5 V, an on voltage of 6.5 V, and a normally white mode was used.

The liquid crystal panel unit 100 manufactured by the above procedure
FIG. 3 shows the dependency of the transmittance on the applied voltage. A liquid crystal evaluation device LCD5000 manufactured by Otsuka Electronics Co., Ltd. was used for the measurement. Also,
FIG. 17B shows the transmittance distribution of the liquid crystal panel during white display (when an off voltage is applied). A liquid crystal evaluation device LCD5000 manufactured by Otsuka Electronics Co., Ltd. was used for the measurement. FIG. 17B shows the transmittance distribution as viewed from the front of the panel, and the rubbing direction is the direction indicated by the arrow. The transmittance distribution was almost symmetrical in the panel vertical direction (rubbing direction), but the panel left-right direction perpendicular to the rubbing direction was asymmetric, and the transmittance in the diagonal right direction was low. The transmittance distribution in the left-right direction of FIG. 17B is extracted in FIG.

As the illuminating device unit 200 for illuminating the liquid crystal panel unit 100 from behind the panel, an illuminating device having a luminance distribution that compensates for the asymmetric transmittance distribution of the liquid crystal panel unit 100 as described above is used. That is, the directional films 14 and 15 are provided in the lighting device as prism sheets capable of condensing light in the front direction of the panel in the vertical direction of the front of the panel, and about 10 cm from the front in the horizontal direction.
Using a tilted prism sheet capable of condensing light in a tilted direction, two sheets were installed orthogonally. Each of the prism sheets used had an acrylic resin inclined prism formed at intervals of about 50 μm on a polyester substrate. FIG. 5 shows the luminance distribution in the left-right direction of the illumination device according to the first embodiment (solid line). As a result, an asymmetric luminance distribution was obtained in which the luminance became maximum in a direction inclined to the right by 10 ° from the front. FIG. 5 also shows a luminance distribution in a conventional illumination device having a symmetric luminance distribution (broken line). In the conventional configuration, two prism sheets having a light-collecting property are arranged orthogonally on the front of the panel.

FIG. 6 shows the luminance distribution in the left-right direction of the liquid crystal display device according to the present embodiment when the liquid crystal panel portion 100 and the lighting device portion 200 are combined. In the liquid crystal display device of the present embodiment, the asymmetry of the transmittance of the liquid crystal panel unit 100 as shown in FIG. 4 is compensated by the illumination device unit 200 having an asymmetric luminance distribution, and is substantially symmetric in the left-right direction. A liquid crystal display device having an excellent luminance distribution can be obtained. As a result, a liquid crystal display device having high front luminance and less eye fatigue can be realized. On the other hand, as shown by the dashed line in FIG. 6, when the liquid crystal display device is configured using the illuminating device of the conventional configuration having a symmetrical luminance distribution, the luminance distribution is largely different between the left and right.

In the present embodiment, an illuminating device having a luminance center in a direction obliquely 10 ° to the right from the front of the liquid crystal panel is used. However, if it is within the range of 5 ° to 20 °, an asymmetric transmittance is obtained. The effect of compensating is obtained. 5 shifts in luminance center
If it is less than °, the effect of compensating for the asymmetric transmittance distribution becomes insufficient, and the luminance in the oblique right direction becomes smaller than the luminance in the oblique left direction. On the other hand, if the deviation of the luminance center exceeds 20 °, the luminance in the diagonally right direction becomes too high, becomes higher than that in the diagonally left direction, resulting in an asymmetric luminance distribution. FIG. 7 shows a luminance distribution (FIG. 7B) of the liquid crystal panel when an illuminating device (FIG. 7A) having a luminance center in a direction obliquely 30 ° to the right from the front of the liquid crystal panel is used.

In this embodiment, the liquid crystal panel 1
Although the liquid crystal layer 4 was initially twisted at a twist angle of 180 ° when no voltage was applied, the amount of the chiral agent was small, and the initial alignment of the liquid crystal layer 4 was not twisted. Even when a liquid crystal panel with a splay alignment is used, or a liquid crystal panel with a rubbing direction shifted from parallel without adding a chiral agent to the liquid crystal, the transmittance of the liquid crystal panel when off-voltage is applied In order to compensate for the asymmetry of the distribution,
When 0 is provided, a liquid crystal display device having a luminance distribution with excellent symmetry in addition to the high-speed response characteristics due to the bend alignment can be obtained.

Embodiment 2 In Embodiment Mode 2, a liquid crystal display device using a liquid crystal panel in which the initial alignment of the liquid crystal layer when no voltage is applied is a twist alignment with a twist angle of 210 °. FIG. 8 shows a rubbing direction in the liquid crystal panel according to the present embodiment. As shown in FIG. 8, the rubbing directions on the electrode substrate side and the counter substrate side are directions shifted from the lower side of the liquid crystal panel by 15 ° left and right, respectively. The alignment film material is J
AL3046 manufactured by SR was used. Panel gap is 7.
The thickness was 5 μm. The liquid crystal material is the same as the liquid crystal material of the first embodiment except for the chiral pitch. In the second embodiment, the chiral pitch is a 20 μm pitch (left chiral) within the range of Expression (2). The structure of the compensation film was the same as that of the first embodiment. The drive voltage is the off voltage.
The normally white mode was used at 5 V and the ON voltage was 6.5 V.

FIG. 9 shows the transmittance distribution of the liquid crystal panel during white display (when an off voltage is applied) according to the present embodiment. FIG. 9 shows the transmittance distribution as viewed from the front of the panel. A liquid crystal evaluation device LCD5000 manufactured by Otsuka Electronics was used for the measurement. The transmittance distribution was almost symmetric in the vertical direction when viewed from the front of the panel, but was asymmetric in the left-right direction, and the transmittance in the diagonal right direction was low. The transmittance distribution in the left-right direction of FIG. 9 is extracted in FIG. However, the transmittance distribution at a twist angle of 210 ° (Embodiment 2) was not as asymmetric as at 180 ° (Embodiment 1). This is considered to be due to the difference in the angle of rise of the liquid crystal molecules at the center of the liquid crystal layer. FIG. 11 shows that the twist angle is from 120 ° to 240 °.
4 shows the applied voltage dependence (calculated value) of the liquid crystal molecule tilt angle at the center of the liquid crystal layer in the case of °. OFF voltage (2.5V)
In the vicinity, liquid crystal molecules rise as the twist angle increases. Therefore, the larger the twist angle,
It is considered that the symmetry of the transmittance distribution is improved.

For a liquid crystal panel having such a viewing angle characteristic, a prism sheet capable of condensing light in the front direction of the panel in the vertical direction and about 10 ° from the front in the horizontal direction is used as a directional film used in the lighting device. Using an inclined prism sheet having a light condensing property in an inclined direction, two sheets were installed orthogonally. However, an inclined prism sheet having a lower light-collecting performance than that used in the first embodiment was used. FIG. 12 shows the luminance distribution in the left-right direction of the illumination device according to the second embodiment by a solid line. As a result, an asymmetric luminance distribution was obtained in which the luminance became maximum in a direction inclined by 10 ° from the front. FIG. 12 also shows the luminance distribution in a conventional illumination device having a symmetric luminance distribution by a broken line.

FIG. 13 shows the luminance distribution in the left-right direction of the liquid crystal display device according to the present embodiment when the liquid crystal panel and the lighting device are combined. In the liquid crystal display device of the present embodiment, the asymmetry of the transmittance of the liquid crystal panel as shown in FIG. 10 is compensated for by the illumination device having an asymmetrical luminance distribution, and the luminance distribution of the liquid crystal panel is substantially symmetric in the left-right direction. A liquid crystal display device is obtained. As a result, a liquid crystal display device having high front luminance and less eye fatigue can be realized. on the other hand,
As shown by the dashed line in FIG. 13, when the liquid crystal display device is configured using a lighting device having a symmetrical luminance distribution and a conventional configuration, the luminance distribution is significantly different between the left and right.

In the first and second embodiments, the twist angles when no voltage is applied are 180 ° and 210 °.
However, the twist angle may be in the range of 180 ° to 240 °. However, as the angle deviates from 180 °, the influence of the backflow increases, and the response speed increases. If the twist angle is set beyond 240 °, hysteresis appears in the transmittance / applied voltage curve.
It is not suitable for active driving. In addition, since the liquid crystal layer is in a twist alignment state with a twist angle of 180 ° to 240 ° when no voltage is applied, a liquid crystal display by an OCB mode display method can be performed without performing a bend transition process by applying a high voltage.

In each of the above embodiments, the illuminating device having a luminance distribution that compensates for the asymmetry of the transmittance distribution of the liquid crystal panel is configured by devising the configuration of the directional films 14 and 15. By devising the configuration of the reflective film 11, an illumination device having a luminance distribution that compensates for the asymmetry of the transmittance distribution of the liquid crystal panel may be configured.

[0037]

As described above, in the liquid crystal display device of the present invention, a liquid crystal layer is sandwiched between a pair of opposing transparent substrates, and a voltage is applied to the liquid crystal layer to bring the liquid crystal layer into a bend alignment state. A liquid crystal panel that performs display by changing the transmittance by changing the alignment state between a first voltage and a second voltage higher than the first voltage; and an illumination that illuminates the liquid crystal panel from the back of the panel. In the liquid crystal display device provided with the device, the liquid crystal layer has a first direction in a thickness direction of the liquid crystal layer.
There is a twist in the orientation of the liquid crystal layer when the voltage is applied, and the lighting device compensates for the asymmetry of the transmittance distribution of the liquid crystal panel, which is generated in the direction in which the liquid crystal molecules are inclined in the center of the liquid crystal layer due to the twist. Since a configuration having a luminance distribution is used, a liquid crystal display device having a luminance distribution with excellent symmetry can be realized. As a result, in addition to the high-speed response characteristics due to the bend alignment, there is an effect that a liquid crystal display device with less eye fatigue can be realized.

Further, in the liquid crystal display device of the present invention, in the above liquid crystal display device, the luminance center of the illuminating device is 5 to 5 opposite to the direction in which the liquid crystal molecules are inclined at the center of the liquid crystal layer with respect to the front direction of the liquid crystal panel. Since the direction is 20 °, a liquid crystal display device having a luminance distribution with excellent symmetry can be realized.

Further, in the liquid crystal display device of the present invention, in the liquid crystal display device described above, when no voltage is applied, the liquid crystal layer is in a twist alignment state having a twist angle of 180 ° to 240 °, so that a bend transition process by applying a high voltage is performed. Without OCB
The liquid crystal display by the mode display method becomes possible.

[Brief description of the drawings]

FIG. 1 is an exploded view showing a configuration of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a directional film and a reflective film in the lighting device according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing the applied voltage dependence of the transmittance of the liquid crystal panel according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a transmissivity distribution in the left-right direction during white display of the liquid crystal panel according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a left-right luminance distribution of the lighting device according to the first embodiment of the present invention;

FIG. 6 is a diagram showing a left-right luminance distribution during white display of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a luminance distribution of the illumination device and the liquid crystal display device according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a rubbing direction of a liquid crystal panel according to Embodiment 2 of the present invention.

FIG. 9 is a diagram showing a transmittance distribution during white display of the liquid crystal panel according to Embodiment 2 of the present invention.

FIG. 10 is a diagram showing a transmissivity distribution in the left-right direction during white display of the liquid crystal panel according to the second embodiment of the present invention.

FIG. 11 is a diagram showing the applied voltage dependence (calculated value) of the liquid crystal molecule tilt angle in the center of the liquid crystal layer of the liquid crystal panel according to Embodiment 2 of the present invention.

FIG. 12 is a diagram showing a luminance distribution in the left-right direction of the lighting apparatus according to Embodiment 2 of the present invention.

FIG. 13 is a diagram showing a left-right luminance distribution during white display of the liquid crystal display device according to the second embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a liquid crystal panel in an OCB mode mode and an alignment state of liquid crystal molecules.

FIG. 15 is a diagram illustrating a configuration of an optical compensation film of a liquid crystal panel according to an OCB mode method.

FIG. 16 is a diagram showing a state of a change in an alignment state of liquid crystal molecules in a liquid crystal panel according to an OCB mode method.

FIG. 17 is a diagram showing the transmittance distribution of the liquid crystal panel in the OCB mode when white is displayed, with and without the addition of a chiral agent.

FIG. 18 is a diagram showing a difference in the alignment state of a liquid crystal panel in the OCB mode when white display is performed, with and without addition of a chiral agent.

FIG. 19 is a view for explaining a mechanism in which the transmittance of the liquid crystal panel in the OCB mode mode when displaying white is asymmetric when the chiral agent is added or not.

[Explanation of symbols]

Reference Signs List 1 electrode substrate, 2 counter substrate, 3 alignment film, 4 liquid crystal layer, 5, 6 optical compensation film, 7, 8 polarizing plate, 9
Lamp, 10 light guide plate, 11 reflection film, 12, 1
3 Diffusion film, 14, 15 Directional film, 16
Tilted prism, 17 base material, 18 tilted reflective film, 4
1,42 liquid crystal molecules, 61 discotic liquid crystal film, 62 c-plate, 63 uniaxial film, 100
Liquid crystal panel section, 200 lighting section.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kasuko Wakita 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Hiroyuki Fuchigami 2-3-2 Marunouchi, Chiyoda-ku, Tokyo 3 Rishi Electric Co., Ltd. FA14Z FA21Z FA23Z FA31Z FA41Z GA13 HA09 HA10 KA10 LA19 LA30

Claims (3)

[Claims] 1. A liquid crystal layer is sandwiched between a pair of opposing transparent substrates, a voltage is applied to the liquid crystal layer to bring the liquid crystal layer into a bend alignment state, and a first voltage and a first voltage higher than the first voltage. In a liquid crystal panel that performs display by changing the transmittance by changing the alignment state between the voltage of 2 and a liquid crystal display device that includes an illumination device that illuminates the liquid crystal panel from the back of the panel, the liquid crystal layer is The orientation of the liquid crystal layer when the first voltage is applied is twisted with respect to the thickness direction of the liquid crystal layer, and the illuminating device causes the liquid crystal to be generated in the direction in which the liquid crystal molecules are inclined at the center of the liquid crystal layer due to the twist. A liquid crystal display device having a luminance distribution that compensates for the asymmetry of the transmittance distribution of the panel. 2. The lighting device according to claim 1, wherein the center of luminance of the lighting device is in a direction of 5 to 20 ° with respect to a front direction of the liquid crystal panel, which is opposite to a direction in which liquid crystal molecules are inclined in a central portion of the liquid crystal layer. The liquid crystal display device as described in the above. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is in a twist alignment state having a twist angle of 180 ° to 240 ° when no voltage is applied.