JPH1039285A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a wide visual angle of a liquid crystal display device using a liquid crystal cell in which molecules of liquid crystal are twistingly oriented. SOLUTION: A scattering plate 14 having a scattering angle range S in the direction of one side with respect to a normal and having a scattering characteristic scattering a light made incident at an incident angle within this scattering angle to emit it is provided on the exiting side of a liquid crystal 10 while heading the direction including the scattering angle range S in a prescribed direction and two sheets of discotic liquid crystal films 15, 16 are provided across the liquid crystal 10 while making respective lag phase axes 15a, 16a cross roughly at right angles each other and also polarizing plates 17, 18 are arranged across them. Moreover, a condenser member 19 having a light converging property converging a light toward a direction inclined to a prescribed direction with respect to the normal is provided at the incident side of the incident side polarizing plate 17 while heading the light converging direction of it in a direction opposite to the direction including the scattering angle range S of the scattering plate 14.

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 having a wide viewing angle.

[0002]

2. Description of the Related Art As a liquid crystal display device, TN is generally used.
(Twisted nematic) type or STN (super twisted nematic) type is used. These liquid crystal display devices are composed of a liquid crystal cell in which liquid crystal molecules are twist-aligned between a pair of substrates, and an incident side and an output side polarizing plate interposed between the liquid crystal cells.

[0003]

However, the above-mentioned TN type or STN type liquid crystal display device has a display characteristic whose directionality is determined by the alignment state of liquid crystal molecules in a liquid crystal cell. There is a problem that the observation angle range in which the image can be viewed in a good state is narrow.

This is because the value of Δn · d (the product of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer) of the liquid crystal cell apparently changes depending on the observation angle. Even if the applied voltage between the electrodes provided on the inner surface of the substrate is the same, that is, even if the rising angle of the liquid crystal molecules with respect to the substrate surface is the same, the light transmittance differs depending on the observation direction. The voltage-transmittance characteristic of the liquid crystal display device has an observation angle dependency.

[0005] The liquid crystal display device has a unique viewing angle (observation angle at which the contrast is highest) determined by the orientation state of the liquid crystal molecules in the liquid crystal cell, and has a good contrast when viewed from a direction near the viewing angle. The display is observed, but the contrast is extremely reduced as the observation angle deviates from the viewing angle direction. In a gray scale display in which the brightness is given a gradation, the brightness of the halftone display is observed. Since the grayscale inversion is caused by a large change depending on the angle, the viewing angle range in which the display can be viewed in a satisfactory state with sufficient contrast and no grayscale inversion is limited, and thus the viewing angle is narrow. .

In general, a liquid crystal display device has a viewing angle in a direction slightly inclined (about 2 ° to 5 °) toward the lower edge of the screen with respect to an axis perpendicular to the screen (light emitting surface). A liquid crystal display device in which the orientation direction of liquid crystal molecules in the vicinity of each substrate of the liquid crystal cell is set as described above is used, and the liquid crystal display device thus designed has an observation angle in the lower edge direction of the screen with respect to the axis. When the angle exceeds about 15 °, the gray level is inverted, and when the viewing angle of the perpendicular line toward the upper edge of the screen exceeds about 10 °, the black level rises rapidly (the darkness of black display is reduced due to light leakage). Therefore, the viewing angle is only about 25 °.

The present invention uses a liquid crystal cell in which liquid crystal molecules are twist-aligned between a pair of substrates. However, the present invention provides a viewing angle range in which a satisfactory display with sufficient contrast and no grayscale inversion can be observed. It is an object of the present invention to provide a liquid crystal display device which can be enlarged to realize a wide viewing angle.

[0008]

According to the present invention, there is provided a liquid crystal display device comprising: a liquid crystal cell in which liquid crystal molecules are twist-aligned between a pair of substrates; a scattering plate having an incident angle dependency in light scattering characteristics; Two discotic liquid crystal films are laminated with at least the scattering plate disposed on the exit surface side of the liquid crystal cell, and a polarizing plate is disposed on each of the incident side and the exit side with these interposed therebetween. The scattering plate has a scattering angle range sandwiched between two surfaces having different angles with respect to the perpendicular in one direction with respect to the perpendicular, and transmits light incident at an incident angle within the scattering angle range. The light that is scattered and emitted and has a scattering characteristic of being emitted at a high transmittance without being scattered is hardly scattered, and the scattering plate includes the scattering angle range. Direction Together provided toward the fixed direction, Disukoteikku liquid crystal film of the two sheets is characterized in that are provided respective slow axes were substantially perpendicular to each other.

According to the liquid crystal display device of the present invention, of the light emitted from the liquid crystal cell and incident on the scattering plate, the light incident at an incident angle within the scattering angle range of the scattering plate is scattered and emitted. Therefore, if the scattering plate is provided with a direction including the scattering angle range in a predetermined direction, that is, a direction in which the viewing angle is desired to be widened, and the emitted light in that direction is scattered, the inversion of the gradation is performed. The emission angle range of light that can provide a display that does not occur is widened.

Further, in this liquid crystal display device, the light incident through the polarizing plate on the incident side is transmitted through the two discotic liquid crystal films arranged with the slow axes substantially orthogonal to each other, and the light on the emitting side is transmitted. Since the light is incident on the polarizing plate, the birefringence of these discotic liquid crystal films makes the emission angle range of light from which a display in which gradation inversion does not occur is more complete than the range due to the scattering effect of the scattering plate. As the width increases in the circumferential direction, the black level is suppressed low and the contrast increases.

Therefore, according to the liquid crystal display device of the present invention, although a liquid crystal cell in which liquid crystal molecules are twisted between a pair of substrates is used, a satisfactory contrast is obtained without gradation inversion. The viewing angle range in which display can be observed is widened, and a wide viewing angle can be realized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal display device of the present invention has a scattering function of a scattering plate having an incident angle dependence on light scattering characteristics;
Utilizing the birefringence effect of two discotic liquid crystal films whose slow axes are arranged almost orthogonal to each other, the viewing angle range in which a satisfactory display with sufficient contrast and no gradation inversion can be observed is increased. It was done.

In the liquid crystal display device according to the present invention, the scattering plate has a direction including a scattering angle range in a unique viewing angle direction provided by a liquid crystal display system including the liquid crystal cell and the incident side and the exit side polarizing plates. It is preferable to provide the liquid crystal display system in the direction including the viewing angle. In this case, the viewing angle of the liquid crystal display system in the direction including the viewing angle direction can be widened.

In this case, the liquid crystal display system has two directions in one direction with respect to a perpendicular line of an emission surface (a screen of the liquid crystal display device).
Designed so that the viewing angle comes in a direction inclined by about 5 ° to 5 °, and as the scattering plate, the first surface of the two surfaces that defines the scattering angle range is perpendicular to the scattering plate. A second surface in a direction inclined from the perpendicular by an angle exceeding the first surface in the one direction with respect to the perpendicular, It is desirable to use one having a scattering angle range of about 30 ° to about 50 °.

Further, in the two discotic liquid crystal films, the total value of the product Δn ′ · d ′ of the refractive index anisotropy Δn ′ of each liquid crystal and the film thickness d ′ is:
It is desirable that the value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the thickness d of the liquid crystal layer be substantially the same. In this case, the birefringence effect of the discotic liquid crystal film is reduced. There is no adverse effect on the display.

In this case, for example, when the twist angle of the liquid crystal molecules of the liquid crystal cell is approximately 90 °, one of the discotic liquid crystal films is moved so that the slow axis of the discotic liquid crystal film is shifted toward the liquid crystal near one of the substrates of the liquid crystal cell. It is preferable to provide the other discotic liquid crystal film substantially parallel to the orientation direction of the molecules and to provide the other discotic liquid crystal film with the slow axis thereof substantially parallel to the orientation direction of the liquid crystal molecules near the other substrate of the liquid crystal cell.

Further, in the liquid crystal display device of the present invention,
A light-collecting member having a light-condensing property for condensing light in a direction inclined in a predetermined direction with respect to a vertical line on the incident surface side of the incident-side polarizing plate, the light-condensing direction of the scattering plate If the light is arranged in the direction opposite to the direction including the scattering angle range, the amount of transmitted light is increased even in the direction opposite to the direction including the scattering angle range of the scattering plate, and the light is emitted by two discotic discs. Since the light passes through the liquid crystal film and is incident on the emission-side polarizing plate, a wider viewing angle can be obtained.

[0018]

FIG. 1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention. This liquid crystal display device includes a liquid crystal cell 10 in which liquid crystal molecules 13a are twist-aligned between a pair of substrates 11 and 12, a scattering plate 14 whose light scattering characteristic has an incident angle dependence, and two discote chips. The liquid crystal films 15 and 16 are laminated by disposing at least the scattering plate 14 on the emission surface side of the liquid crystal cell 10, and sandwiching the polarizing plate 1 on each of the incident side and the emission side.
7 and 18, and a light condensing member 19 for condensing light from a light source (not shown) in a predetermined direction on the incident surface side of the polarizing plate 17 on the incident side. .

The liquid crystal cell 10 has a liquid crystal layer 13 interposed between a pair of transparent substrates 11 and 12 made of glass or the like.
Transparent electrodes are formed on the inner surfaces of the two substrates 11 and 12, respectively, and an alignment film is provided thereon. The pair of substrates 11 and 12 are joined via a frame-shaped sealing material (not shown).
It is sealed in a region surrounded by the sealing material between 1 and 12.

This liquid crystal is a nematic liquid crystal having a positive dielectric anisotropy, and its liquid crystal molecules 13a are controlled by the alignment films in the direction of alignment in the vicinity of the substrates 11 and 12, so that the two substrates 11, 12 Twist orientation is between them.

The polarizing plate 17 on the incident side of the polarizing plates 17 and 18 has its absorption axis 17a oriented in the orientation direction 11 of the liquid crystal molecules in the vicinity of the incident side substrate 11 of the liquid crystal cell 10.
a, and the polarizing plate 18 on the output side is
The absorption axis 18a is connected to the emission side substrate 12 of the liquid crystal cell 10.
The liquid crystal cell 10 and these polarizing plates 17 and 18 constitute a TN type liquid crystal display system.

In this embodiment, the liquid crystal cell 1
0, the twist angle of the liquid crystal molecules 13a is set to approximately 90 °, and the viewing angle direction (observation direction in which the highest contrast is obtained) F inherent in the TN type liquid crystal display system is determined by the emission surface ( In the vicinity of each of the substrates 11 and 12 of the liquid crystal cell 10, the liquid crystal cell 10 is in a direction slightly inclined toward the lower edge of the screen with respect to an axis (hereinafter, referred to as a vertical axis) Z perpendicular to the screen (the screen of the liquid crystal display device). The orientation directions 11a and 12a of the liquid crystal molecules are set.

That is, as shown in FIG. 1, the orientation direction 11a of the liquid crystal molecules in the vicinity of the incident side substrate 11 of the liquid crystal cell 10 is rightward with respect to the horizontal axis X of the screen of the liquid crystal display device when viewed from the emission side. And the orientation direction 12a of the liquid crystal molecules in the vicinity of the emission-side substrate 12 is approximately 45 ° counterclockwise as viewed from the emission side with respect to the horizontal axis X. 13a is substantially 90 ° clockwise as viewed from the emission side from the incidence side substrate 11 to the emission side substrate 12.
Twist orientation at a twist angle of °.

In the direction of the vertical axis Y of the screen of the liquid crystal display device, when viewed from the vertical axis Z, the lower edge direction of the screen is 6:00, and the upper edge direction of the screen is 12:00. , The viewing angle direction F of the liquid crystal display system is substantially parallel to a plane including the vertical axis Y of the screen and the vertical axis Z, and is slightly inclined at 6:00 from the vertical axis Z. Direction.

On the other hand, the scattering plate 14 is a surface including a specific direction along the plate surface, and has a scattering angle range S between two surfaces having different angles from the perpendicular to the scattering plate.
The light incident at an incident angle within the scattering angle range is scattered and emitted, and the light incident at an incident angle outside the scattering angle range is emitted with high transmittance with little scattering.

Various types of scattering plates having such scattering characteristics are known, but in this liquid crystal display device, the scattering plate 14 has a scattering angle range S that is perpendicular to the scattering plate. The scattering plate 14 is arranged in such a manner that its perpendicular line coincides with the vertical axis Z of the liquid crystal display system, and the direction including the scattering angle range S (the one direction) is changed to the viewing angle. Is provided in the direction that you want to spread. In the liquid crystal display device of this embodiment, the direction including the unique viewing angle direction F of the TN type liquid crystal display system is the direction in which the viewing angle is to be widened.

That is, the scattering angle range S of the scattering plate 14 is substantially parallel to a plane including the vertical axis Y of the screen and the vertical axis Z, and the direction of 6:00 when viewed from the vertical axis Z (screen). And the scattering angle range S
Are the surfaces including the horizontal axis X of the screen.

In this embodiment, the liquid crystal display system is designed so that the viewing angle is in a direction inclined by about 2 ° to 5 ° in one direction (direction of 6:00) with respect to the vertical axis Z. Then, as the scattering plate 14, the first surface of the two surfaces defining the scattering angle range S is in the one direction (6:00) with respect to the perpendicular (same as the vertical axis Z) of the scattering plate. Direction) in the range of 0 ° to about 20 °, and the second surface is inclined at an angle exceeding the first surface in the one direction with respect to the perpendicular, and An angle range S of about 30 ° to about 50 ° is used.

Each of the discotic liquid crystal films 15 and 16 is a special retardation film made of a polymer liquid crystal having a disk-shaped molecular shape. The orientation of the discotic molecules is changed so that they rise from the horizontal surface to the other surface and then rise almost vertically from the horizontal plane. The direction along the central axis of the posture change of the discotic molecules is the slow axis, and the direction perpendicular to the slow axis (the direction along the film surface) is the direction parallel to the film surface. Direction) is the fast axis.

One of the two discotic liquid crystal films 15 and 16 is disposed on the incident side of the liquid crystal cell 10, and the other discotic liquid crystal film 17 is disposed on the incident side of the liquid crystal cell 10. Liquid crystal cell 1
The light-exiting side of the light-scattering plate 14 is disposed on the light-exiting side of the light-scattering plate 14.

In this liquid crystal display device, the two discotic liquid crystal films 15 and 16 are oriented such that the surfaces of the discotic molecules have the same orientation state, for example, the discotic molecules are oriented almost vertically. The surfaces on the opposite sides face each other, and the respective slow axes are provided substantially orthogonal to each other.

In FIG. 1, reference numerals 15a and 16a denote slow axes of the two discotic liquid crystal films 15 and 16, respectively. In this embodiment, discotic liquid crystal films 15 and 16 are arranged on the incident surface side of the liquid crystal cell 10. The liquid crystal film 15 is provided with its slow axis 15a oriented approximately 45 ° clockwise with respect to the horizontal axis X of the screen when viewed from the emission side.
Discotic liquid crystal film 1 arranged on the exit surface side of
6 is provided with its slow axis 16a oriented approximately 45 ° counterclockwise with respect to the horizontal axis X when viewed from the emission side.

That is, in this embodiment, by providing the two discotic liquid crystal films 15 and 16 as described above, the respective slow axes 15a and 16a are made substantially orthogonal to each other, and at the same time, The slow axis 15a of the discotic liquid crystal film 15 is
Orientation direction 1 of liquid crystal molecules near the incident side substrate 11
1a, and the slow axis 16a of the discotic liquid crystal film 16 on the emission surface side is made substantially parallel to the orientation direction 12a of the liquid crystal molecules in the vicinity of the emission side substrate 12 of the liquid crystal cell 10.

Furthermore, in this embodiment, the product Δn ′ · product of the refractive index anisotropy Δn ′ of the liquid crystal of each of the two discotic liquid crystal films 15 and 16 and the film thickness d ′.
Each discotic liquid crystal film 15, d is so set that the total value of d ′ is substantially the same as the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell 19 and the liquid crystal layer thickness d.
16 Δn ′ · d ′ values are set.

The light condensing member 19 disposed on the incident surface side of the polarizing plate 17 on the incident side covers the entire surface (outgoing surface) of a transparent sheet made of, for example, acrylic resin, etc. Are formed continuously in the width direction of the prism sheet, and the light condensing member 19 has a light condensing property for condensing light in a direction inclined in a predetermined direction with respect to a perpendicular to the prism sheet.

FIG. 2 is an enlarged view of a part of the light condensing member 19. Each prism portion 19a has its vertex in the normal prism shape shown by a broken line in FIG. It has a cross-sectional shape deviated to one side by a predetermined tilt angle θ. Note that the inclination angle θ is 5 ° to 30 °.
And the vertex angle α of the prism portion 19a is 60 ° to 85 °.

That is, the condensing member 19 refracts incident light from a light source (not shown) by each prism portion 19a as shown by an arrow in FIG. 2 and emits the refracted light. It has a light collecting property of collecting light in a direction inclined in a predetermined direction with respect to the vertical line H).

The light condensing member 19 has its perpendicular line coincident with the vertical axis Z of the liquid crystal display system, the length direction of each prism portion 19a is substantially parallel to the horizontal axis X of the screen, and the light condensing direction is set as described above. The scattering plate 14 is arranged in a direction opposite to the direction including the scattering angle range S (direction of 6:00) (direction of 12:00).

FIG. 3 shows an observation angle-luminance characteristic of the light-collecting member 19. The light-collecting member 19 is formed by a normal prism sheet shown by a broken line in FIG. ), The brightness of the emitted light when viewed from around 0 ° is relatively low, as compared with the observation angle-luminance characteristic of
When observed from the direction of 6:00 (the direction including the scattering angle range S of the scattering plate 14), the observation angle range in which sufficient luminance is obtained is slightly narrower than that of a normal prism sheet.
12:00 direction, that is, the scattering angle range S of the scattering plate 14
Is almost the same as the luminance near the observation angle 0 ° over a wide observation angle.

The light source is, for example, a surface light source in which a light source lamp such as a straight tube fluorescent lamp is disposed so as to face one or both end surfaces of a transparent light guide plate made of an acrylic light guide resin or the like. Yes, the light source lamp is taken into the light guide plate from its end face, and the light is guided by the light guide plate,
The light is emitted from the surface of the light guide plate.

According to this liquid crystal display device, the liquid crystal cell 10
Out of the light incident on the scattering plate 14 is scattered and emitted from the scattering plate 14 at an incident angle within the scattering angle range S of the scattering plate 14, so that the scattering plate 14 Is provided in a predetermined direction, that is, a direction in which the viewing angle is desired to be widened, and if light emitted in that direction is scattered, a light emission angle range in which display in which gradation inversion does not occur is obtained. Becomes wider.

Moreover, in this liquid crystal display device, the light that has passed through the polarizing plate 17 on the incident side and has entered the slow axis 15a, 1
6a are transmitted through the two discotic liquid crystal films 15 and 16 arranged substantially orthogonal to each other and enter the output-side polarizing plate 18, so that the birefringence of the discotic liquid crystal films 15 and 16 causes The light emission angle range in which a display in which gradation inversion does not occur is obtained depends on the scattering plate 1.
In addition to being wider in the entire circumferential direction than the range due to the scattering action of No. 4, the black level is suppressed low and the contrast is increased.

FIG. 4 is an observation angle-transmittance characteristic diagram of a display device having only the TN type liquid crystal display system, and FIG. 5 is an observation angle-transmission ratio characteristic of a display device in which the scattering plate 14 is added to the liquid crystal display system. FIG. 6 is an observation angle-transmittance characteristic diagram of a display device in which two discotic liquid crystal films 15 and 16 are added to the liquid crystal display system, and FIG. 7 is a scattering plate 1 in the liquid crystal display system.
FIG. 7 is an observation angle-transmittance characteristic diagram of a display device to which four and two discotic liquid crystal films 15 and 16 are added. In each of the drawings, (a) is a graph with respect to a vertical axis Z of the liquid crystal display system. The characteristics when observed from the direction of 6:00 are shown,
(B) shows the characteristics when observed from the direction of 12:00 with respect to the vertical axis Z.

A comparison of the viewing angle-transmittance characteristics of these display devices shows that the display device having only a liquid crystal display system has a 6: 0 ratio.
The characteristic in the direction of 0 is about 3 as shown in FIG.
Up to the observation angle of 0 °, the floating of the black level is small,
When the viewing angle exceeds about 15 °, the gray scale is inverted on the low gray scale side, and the characteristic in the direction of 12:00 is about 18 ° as shown in FIG. The gray level is not inverted up to the corner, but when the viewing angle exceeds about 10 °, the black level rapidly rises.

Next, looking at the viewing angle-transmittance characteristic of the display device in which the scattering plate 14 is added to the above-mentioned liquid crystal display system, the sixth is:
As shown in FIG. 5 (a), the characteristics in the direction of 00 are such that there is no gradation inversion up to an observation angle of about 45 °, and the floating of the black level is small over an observation angle of more than 30 °. Therefore, the viewing angle in the direction of 6:00 is greatly improved as compared with a display device having only the liquid crystal display system.

However, the characteristics of this display device in the direction of 12:00 are not so different from those of the display device having only the liquid crystal display system as shown in FIG. Although the viewing angle range in which inversion does not occur is slightly widened, when the viewing angle exceeds about 10 °, the black level rises sharply.

When viewing the viewing angle-transmittance characteristics of a display device in which two discotic liquid crystal films 15 and 16 are added to the liquid crystal display system, the characteristics in the direction of 6:00 are as shown in FIG. As shown in (a), there is no gradation inversion up to an observation angle close to 30 °, and the floating of the black level is small over an observation angle exceeding 40 °, and therefore, the viewing angle in the direction of 6:00. Is better than a display device having only a liquid crystal display system. However, the characteristic shown in FIG. 5A, that is, 6:
Compared with the viewing angle-transmittance characteristic in the direction of 00, the viewing angle range in which no grayscale inversion occurs is smaller.

However, the characteristics in the direction of 12:00 of the display device to which the two discotic liquid crystal films 15 and 16 are added, as shown in FIG. Since the angle range is widened to nearly 20 °, and the floating of the black level is small over the observation angle exceeding 30 °, the viewing angle in the direction of 12:00 is smaller than that of the display device in which the scattering plate 14 is simply added. Be improved.

In contrast to the characteristics of these display devices, the characteristics of the display device in which the scattering plate 14 and the two discotic liquid crystal films 15 and 16 are added to the liquid crystal display system in the direction of 6:00 are shown in FIG. As shown in FIG. 7 (a), there is no gradation inversion over a wide observation angle range near 50 °.
The characteristic is that the rise of the black level is small over a wide observation angle up to near 0 °, and thus the viewing angle in the direction of 6:00 is even better than that obtained by simply adding the scattering plate 14 to the liquid crystal display system. .

However, as shown in FIG. 7B, the characteristics of this display device in the direction of 12:00 are such that although the black level rise is small up to an observation angle of about 30 °, the observation angle is about 12 °. Exceeds the threshold value, the gradation is inverted on the high gradation side.

However, the improvement of the viewing angle required for the liquid crystal display device is mainly to widen the viewing angle in the viewing direction F inherent to the liquid crystal display system. In the case of a liquid crystal display device using a liquid crystal display system designed to be in the direction of 6:00 from the axis Z, the viewing angle in the direction of 6:00 is to be widened.

Therefore, the scattering plate 14 is provided in the liquid crystal display system.
According to the display device in which the liquid crystal molecules 13a are twisted between the pair of substrates 11 and 12, the contrast is increased. And the viewing angle range in which good display without gradation inversion can be observed is increased in both the direction of 6:00 and the direction of 12:00 to realize a wide viewing angle.

Since the two discotic liquid crystal films 15 and 16 have substantially the same total value of Δn ′ · d ′ as the value of Δn · d of the liquid crystal cell 10, Disco Liquid Crystal Film 1
The birefringence of 5, 16 does not adversely affect the display.

In the above embodiment, the scattering plate 14 and the two discotic liquid crystal films 1 were added to the liquid crystal display system.
5 and 16, and a light-collecting member 19 having a light-condensing property for condensing light in a direction inclined in a predetermined direction with respect to a perpendicular to the incident surface side of the polarizing plate 17 on the incident side. Since the light-condensing direction is arranged in the direction opposite to the direction including the scattering angle range S of the scattering plate 14, the light-collecting direction is opposite to the direction including the scattering angle range S of the scattering plate 14. Since the amount of transmitted light also increases, and the light is transmitted through the two discotic liquid crystal films and enters the output side polarizing plate, the scattering plate 14 and the two discotic liquid crystal films 15, 16 are provided to the liquid crystal display system. It is possible to obtain a wider viewing angle than that obtained by adding only.

FIG. 8 shows that the scattering plates 14 and 2 are provided in the liquid crystal display system.
FIG. 9 is an observation angle-transmittance characteristic diagram of a display device in which two discotic liquid crystal films 15 and 16 are added, and the light collecting member 19 is arranged on the incident surface side of the polarizing plate 17 on the incident side. ) Shows the characteristics when observed from the direction of 6:00 with respect to the vertical axis Z of the liquid crystal display system, and (b) shows the characteristics when observed from the direction of 12:00 with respect to the vertical axis Z. ing.

As shown in FIG. 8A, the characteristics of this display device in the direction of 6:00 are such that there is no grayscale inversion and a small rise in the black level over an observation angle range close to 50 °. In addition, in the characteristic in the direction of 12:00, as shown in FIG. 8B, there is no gradation inversion up to an observation angle of about 18 °, and the black level rises up to an observation angle of about 30 °. It is a small characteristic.

In the above embodiment, the light-collecting member 19 having a light-collecting property for condensing light in a direction inclined in a predetermined direction with respect to the perpendicular is provided on the incident surface side of the polarizing plate on the incident side. However, the condensing member 19 may be omitted, or a normal prism sheet having an observation angle-luminance characteristic as shown by a broken line in FIG. 3 may be provided. The observation angle-transmittance characteristics shown in FIG.

In the liquid crystal display device of the above embodiment, the viewing angle in the lower edge direction of the screen, that is, in the direction of 6:00, is widened. In this case as well, the scattering plate 14 is oriented in a direction including the scattering angle range S in the liquid crystal cell 1.
If it is provided in a direction including the unique viewing angle direction F of the liquid crystal display system having the liquid crystal display system including the zero and the polarizing plates 117 and 18 on the incident side and the output side, the view in the direction including the viewing angle direction F of the liquid crystal display system is provided. The corners can be widened.

In this case as well, the liquid crystal display system is designed such that the viewing angle is in a direction inclined by about 2 ° to 5 ° in one direction with respect to a perpendicular line of the emission surface (the screen of the liquid crystal display device). The first surface of the two surfaces defining the scattering angle range S of the scattering plate 14 is in a range of 0 ° to about 20 ° in the one direction with respect to a perpendicular to the scattering plate 14. And the second surface is in a direction inclined with respect to the perpendicular to the one direction at an angle exceeding the first surface, and the scattering angle range is about 30 ° to about 50 °. It is desirable to use some.

Further, in the above embodiment, the twist angle of the liquid crystal molecules 13a of the liquid crystal cell 10 was set to approximately 90 °, but the twist angle is not limited to 90 °, and the liquid crystal display system is also TN type. The liquid crystal molecule of the liquid crystal cell is not limited to 1
S twist-oriented at a twist angle of 80 ° to 270 °
It may be of the TN (super twisted nematic) type.

In this case as well, the two discotic liquid crystal films 15 and 16 are provided with respective Δn ′ ·
It is desirable that the total value of d ′ is substantially the same as the value of Δn · d of the liquid crystal cell.
The birefringence of the discotic liquid crystal film does not adversely affect the display.

In the above embodiment, the discotic liquid crystal film 16 disposed on the light exit side of the liquid crystal cell 10 is
The discotic liquid crystal film 16 may be arranged on the incident surface side of the scattering plate 14, although the discotic liquid crystal film 16 is arranged so as to overlap the emission surface of the scattering plate 14.

Further, both of the two discotic liquid crystal films 15, 16 may be arranged on the incident side or the outgoing side of the liquid crystal cell 10, and both discotic liquid crystal films 15, 16 may be disposed. When the scattering plate 14 is arranged between the discotic liquid crystal films 15 and 16 when the scattering plate is arranged on the emission side of the liquid crystal cell 10,
The discotic liquid crystal films 15 and 16 may be laminated, and the scattering plate 14 may be arranged on any one of the surfaces.

[0064]

According to the liquid crystal display device of the present invention, of the light emitted from the liquid crystal cell and incident on the scattering plate, the light incident at an incident angle within the scattering angle range of the scattering plate is scattered. In order to emit the light, if the scattering plate is provided with a direction including the scattering angle range in a predetermined direction, that is, in a direction in which the viewing angle is to be widened, and scatters the emitted light in that direction,
The emission angle range of light from which a display in which gradation inversion does not occur can be widened, and the light transmitted through the incident-side polarizing plate and incident thereon has two slow axes arranged substantially orthogonal to each other. Since the light is transmitted through the discotic liquid crystal film and is incident on the emission-side polarizing plate, the birefringence effect of these discotic liquid crystal films makes it possible to obtain a light emission angle range in which display without inversion of gradation is obtained. A liquid crystal cell in which liquid crystal molecules are twist-aligned between a pair of substrates is used because the width becomes wider in the entire circumferential direction than the range due to the scattering action of the scattering plate, and the black level is suppressed low to increase the contrast. In spite of this, it is possible to widen the viewing angle range in which a favorable display with sufficient contrast and no grayscale inversion can be observed, and a wide viewing angle can be realized.

In the liquid crystal display device according to the present invention, the scattering plate has a direction including a scattering angle range, which is a unique viewing angle direction provided by a liquid crystal display system including the liquid crystal cell and the incident side and the exit side polarizing plates. It is preferable to provide the liquid crystal display system in the direction including the viewing angle. In this case, the viewing angle of the liquid crystal display system in the direction including the viewing angle direction can be widened.

Further, in the two discotic liquid crystal films, the total value of the product Δn ′ · d ′ of the refractive index anisotropy Δn ′ of each liquid crystal and the film thickness d ′ is:
It is desirable that the value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the thickness d of the liquid crystal layer be substantially the same. In this case, the birefringence effect of the discotic liquid crystal film is reduced. There is no adverse effect on the display.

In the liquid crystal display of the present invention,
A light-collecting member having a light-condensing property for condensing light in a direction inclined in a predetermined direction with respect to a vertical line on the incident surface side of the incident-side polarizing plate, the light-condensing direction of the scattering plate If the light is arranged in the direction opposite to the direction including the scattering angle range, the amount of transmitted light is increased even in the direction opposite to the direction including the scattering angle range of the scattering plate, and the light is emitted by two discotic discs. Since the light passes through the liquid crystal film and is incident on the emission-side polarizing plate, a wider viewing angle can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a part of a light collecting member used in the liquid crystal display device.

FIG. 3 is an observation angle-luminance characteristic diagram of the light condensing member.

FIG. 4 is an observation angle-transmittance characteristic diagram of a display device including only a liquid crystal display system including a liquid crystal cell and a polarizing plate on an incident side and an emitting side.

FIG. 5 is an observation angle-transmittance characteristic diagram of a display device in which a scattering plate is added to the liquid crystal display system.

FIG. 6 is an observation angle-transmittance characteristic diagram of a display device in which two discotic liquid crystal films are added to the liquid crystal display system.

FIG. 7 is an observation angle-transmittance characteristic diagram of a display device in which a scattering plate and two discotic liquid crystal films are added to the liquid crystal display system.

FIG. 8: Observation angle vs. transmittance of a display device in which a scattering plate and two discotic liquid crystal films are added to the liquid crystal display system, and a light-condensing member is arranged on the incident surface side of the polarizing plate on the incident side. Characteristic diagram.

[Explanation of symbols]

 Reference Signs List 10: liquid crystal cell 11a: liquid crystal molecule alignment direction near entrance side substrate 12a: liquid crystal molecule orientation direction near exit side substrate 14: scattering plate S: scattering angle range 15, 16, discotic liquid crystal film 15a, 16a Slow axis 17, 18 ... Polarizing plate 17, 18 ... Absorption axis 19: Light collecting member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G02F 1/1347 G02F 1/1347

Claims (4)

[Claims] 1. A liquid crystal cell in which liquid crystal molecules are twisted between a pair of substrates, a scattering plate having an incident angle dependence of light scattering characteristics, and two discotic liquid crystal films. The scattering plate is arranged and laminated on the emission surface side of the liquid crystal cell, and a polarizing plate is arranged on each of the incident side and the emission side with these layers interposed therebetween. In one direction, it has a scattering angle range sandwiched between two surfaces having different angles with respect to the perpendicular, and scatters and emits the incident light at an incident angle within the scattering angle range, and out of the scattering angle range. Light incident at an incident angle has a scattering characteristic of being emitted at a high transmittance with little scattering, and the scattering plate is provided with a direction including the scattering angle range directed in a predetermined direction. With 2. The liquid crystal display device according to claim 1, wherein the two discotic liquid crystal films are provided with their slow axes substantially orthogonal to each other. 2. A direction in which the scattering plate includes a scattering angle range is directed to a direction including a unique viewing angle direction of a liquid crystal display system including the liquid crystal cell and a polarizing plate on an incident side and an emitting side. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided. 3. The total value of the product Δn ′ · d ′ of the refractive index anisotropy Δn ′ of each liquid crystal of the two discotic liquid crystal films and the film thickness d ′ is defined by the following formula: Product Δn of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d
The liquid crystal display device according to claim 1, wherein the value of d is substantially the same. 4. A light-collecting member having a light-collecting property for condensing light in a direction inclined in a predetermined direction with respect to a perpendicular line is provided on the light-incident side of the light-incident surface of the polarizing plate. The liquid crystal display device according to any one of claims 1 to 3, wherein the liquid crystal display device is arranged so that a direction is opposite to a direction including a scattering angle range of the scattering plate.