JPH10123511A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of realizing a wide visual field angle with a simple constitution without performing a complicated driving control and a complicated orientation processing. SOLUTION: This device has a directional scattering property in which light beams entering at an incident angle in a certain angle range from an angle being along a specific direction and being inclined to the direction of one side with respect to a vertical plane H from among light beams entering from a rear surface and emitting to a front surface side is emitted by being scattered at the light-emitting side of a liquid crystal element 10 and also the scattering starting incident angle of the device in which the incident light beams start to emitting by being scattered is 5 deg.∼10 deg.. The visual field angle B of the liquid crystal display device is expanded in a direction opposite to a direction including the scattering incident angle range S of a scattering plate 15 by providing the scattering plate 15 having a characteristic in which the scattering incident angle range S in which the incident light beams emit by being scattered is larger than 30 deg. while heading a direction including the scattering incident angle range S to a prescribed direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[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 have a configuration in which a planar light source generally called a backlight is arranged behind a liquid crystal element in which a pair of polarizing plates are arranged with a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned. ing.

In the above-mentioned TN type or STN type liquid crystal display device, the display characteristics of the liquid crystal element have directionality determined by the alignment state of liquid crystal molecules in a liquid crystal cell, and the display characteristics are changed according to the direction in which display is observed. Viewing angle (observation angle range where display can be observed with good contrast)
Has the problem of being 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 direction. 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 element has an observation direction dependency.

[0005] The dependence of the voltage-transmittance characteristic on the observation direction is determined by changing the voltage applied between the electrodes to the threshold voltage V of the liquid crystal.
There is also a problem when performing gradation display in which gradation is provided by controlling stepwise between th and a voltage Va at which liquid crystal molecules rise and align to a state almost perpendicular to the substrate surface. In this gradation display, the brightness of the display of the halftone greatly changes depending on the observation direction.

The liquid crystal element has a unique viewing angle (viewing angle at which display is observed in the highest contrast state) determined by the viewing direction dependence of the voltage-transmittance characteristic. Although the contrast when viewing the display from is high, when viewed from a direction deviated to some extent from the viewing angle direction, the contrast is significantly reduced, and the grayscale is inverted.

The viewing angle of the liquid crystal element is slightly inclined in one direction from the frontal direction (the direction perpendicular to the screen). Therefore, the viewing angle of the liquid crystal element is inclined from the frontal direction to the side having the viewing angle. Although the viewing angle to the direction is somewhat wide,
The viewing angle in the opposite direction is narrow.

Therefore, conventionally, a pixel division method has been proposed as a means for improving the viewing angle of the liquid crystal display device. The pixel division method includes a voltage control method and an alignment control method.

In the voltage control method, an electrode on one substrate of a liquid crystal cell is divided into a plurality of electrodes for each pixel, and driving of different voltage values is performed between each divided electrode and an electrode on the other substrate. By applying a voltage, the rising angles of the liquid crystal molecules are made different in each region of the pixel, and the viewing angles of these regions are made different from each other.A plurality of regions having different viewing angles are synthesized and observed. Thus, the dependence of the voltage-transmittance characteristic on the observation direction is reduced.

In the alignment control method, each pixel is divided into a plurality of regions, and the alignment state of liquid crystal molecules is made different for each of the regions, so that the viewing angles of these regions are made different from each other. A plurality of regions having different angles are synthesized and observed, so that the dependence of the voltage-transmittance characteristics on the observation direction is reduced.

[0011]

However, in the above-described voltage control method, it is necessary to supply drive signals having different voltage values to each of the divided electrodes, so that the drive control of the liquid crystal display device becomes complicated. Have.

On the other hand, the alignment control method does not require complicated drive control such as a voltage control method, but the liquid crystal cell is provided with an alignment process for aligning liquid crystal molecules in different alignment states for each pixel region. Since it must be performed, there is a problem that the alignment process in the production of the liquid crystal cell is complicated and the production cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device which can realize a wide viewing angle with a simple configuration without performing complicated drive control and complicated alignment processing.

[0014]

A liquid crystal display device according to the present invention comprises a liquid crystal element having a pair of polarizing plates sandwiched between a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twisted, and an emission side of the liquid crystal element. A scattering plate provided in the, the scattering plate, of the light incident from the back surface and emitted to the front side, is inclined in one direction with respect to a surface perpendicular to the scattering plate surface and along a specific direction. Light having an incident angle within a certain angle range from the direction in which the incident light is scattered and emitted, and the incident angle of light from a direction perpendicular to the scattering plate surface is set to 0.
°, the scattering start incident angle at which the incident light begins to scatter and emerge is 5 ° to 10 °, and the scattering incident angle range at which the incident light scatters and exits is greater than 30 °. The plate is provided with a direction including the scattered incident angle range directed in a predetermined direction.

According to the liquid crystal display device of the present invention, of the light emitted from the liquid crystal element, light incident on the scattering plate at an angle within the scattered incident angle range from a direction including the scattered incident angle range. Since the light is scattered and emitted, the dependence of the voltage-transmittance characteristic of the liquid crystal element on the viewing direction is reduced, and the viewing angle of the liquid crystal display device, that is, there is no grayscale inversion,
Moreover, the range of the viewing angle at which the display can be observed with a good contrast is wider than the viewing angle of the liquid crystal element.

The direction in which the viewing angle is widened is opposite to the direction including the scattered incident angle range of the scattering plate, and therefore, the viewing angle is increased in the direction including the scattered incident angle range. If it is provided in the direction opposite to the desired direction, the viewing angle can be widened in a desired direction.

In this liquid crystal display device, the scattering plate has an incident angle of light of 0 ° from a direction perpendicular to the plate surface.
When the incident light starts scattering and emitting light, the scattering start incident angle is 5 ° to 10 °, and the scattering incident angle range at which the incident light is scattered and emitted is larger than 30 °. In addition, the viewing angle of the liquid crystal display device can be more effectively widened.

In the present invention, since the viewing angle is widened by providing the scattering plate on the exit side of the liquid crystal element, complicated driving control and complicated control like the conventional voltage control system and alignment control system are performed. Without the need to perform
A wide viewing angle can be realized with a simple configuration.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention realizes a wide viewing angle by providing a scattering plate on the exit side of a liquid crystal element. As the scattering plate, light enters from the back surface and exits to the front surface side. Of the light, it has a directional scattering property in which light incident at an incident angle within a certain angle range from a direction perpendicular to the scattering plate surface and inclined in one direction with respect to a surface along a specific direction is scattered and emitted. When the incident angle of light from a direction perpendicular to the surface of the scattering plate is 0 °, the scattering start incident angle at which the incident light starts to be scattered and emitted is 5 ° to 10 °, and the incident light is scattered. The scattered incident angle range to be emitted has a characteristic larger than 30 °, and the scattering plate is provided with a direction including the scattered incident angle range in a predetermined direction, so that the viewing angle of the liquid crystal display device is increased. Expanded in the direction opposite to the direction including the scattering angle range of the scattering plate Than it is.

In the present invention, the scattering plate may be disposed between the exit-side polarizing plate and the liquid crystal cell or on the exit surface of the exit-side polarizing plate as long as the scattering plate is on the exit side of the liquid crystal element. Preferably, a scattering plate is provided between the exit-side polarizing plate and the liquid crystal cell in order to reduce blurring of a display image due to light scattering by the scattering plate.

The scattering angle range of the scattering plate is 3
Any angle range may be used as long as it is greater than 0 °, but a desirable scattered incident angle range is 60 ° or less, and a more preferred scattered incident angle range is approximately 50 °.

Further, in the present invention, only one scattering plate may be provided, but two scattering plates are provided on the emission side of the liquid crystal element so that directions including the respective ranges of scattering incident angles are directed to different directions. With such arrangement, the viewing angle of the liquid crystal display device can be widened in two directions.

Still further, in the present invention, a planar light source is disposed behind the liquid crystal element, and a light collector for increasing the front luminance of light emitted from the light source is provided between the light source and the liquid crystal element. Is provided, it is possible to irradiate the liquid crystal element with high-intensity light and to make the light incident on the scattering plate. Therefore, the brightness of the light emitted from the scattering plate is increased, including the scattered light, to provide a brighter light. You can get the display.

[0024]

FIG. 1 is a side view of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device of this embodiment is
A liquid crystal element 10; and a scattering plate 15 provided on an emission side of the liquid crystal element 10.
A flat light source 20 for irradiating the liquid crystal element 10 with light is disposed behind the liquid crystal device 10. Are provided.

The liquid crystal element 10 has a pair of polarizing plates 13 and 14 interposed between a liquid crystal cell 11 having a liquid crystal layer in which liquid crystal molecules are twist-aligned. The liquid crystal cell 11 has a frame-shaped seal. Nematic liquid crystal is sealed between a pair of transparent substrates 12a and 12b joined via a material (not shown).

The liquid crystal cell 11 is, for example, an active matrix type color image display cell, and its internal structure is not shown. However, on the inner surface of one substrate, a plurality of pixel electrodes and these pixel electrodes are respectively provided. Corresponding switching elements (for example, thin film transistors) are arranged in a matrix and an alignment film is provided thereon. On the inner surface of the other substrate, a color filter of a plurality of colors corresponding to each pixel is formed. A sheet-like counter electrode is formed, and an alignment film is provided thereon.

The liquid crystal element 10 includes, for example, a liquid crystal cell 1
1 is a TN type in which the twist angle of the liquid crystal molecules is substantially 90 °, and a pair of polarizing plates 13 and 14 are arranged so that their transmission axes are substantially orthogonal to each other or substantially parallel to each other;
In this embodiment, the direction F of the visual angle is set so as to be inclined to the lower edge direction of the screen to some extent with respect to a plane H perpendicular to the screen and along the horizontal axis of the screen (a direction perpendicular to the paper surface in the figure). The designed one is used.

That is, in the liquid crystal element 10, the orientation direction of the liquid crystal molecules in the vicinity of the incident side substrate 12a of the liquid crystal cell 11 is approximately 45 ° clockwise with respect to the horizontal axis of the screen when viewed from the emission side. The orientation direction of the liquid crystal molecules in the vicinity of the emission side substrate 12b is set to a direction of approximately 45 ° counterclockwise when viewed from the emission side, and the liquid crystal molecules are directed from the incidence side substrate 12a to the emission side substrate 12b and viewed from the emission side to the right. Around 90 ° around
And the transmission axes of the polarizers 13 and 14 on the incident side and the exit side with respect to the orientation direction of the liquid crystal molecules in the vicinity of the incident side and the exit side substrates 12a and 12b of the liquid crystal cell 11. The direction F of the viewing angle of the liquid crystal element 10 is inclined to the lower edge direction of the screen to a certain extent with respect to a plane H perpendicular to the screen and along the horizontal axis. Direction.

The scattering plate 15 provided on the emission side of the liquid crystal element 10 has a surface h perpendicular to the scattering plate surface and along a specific direction, out of the light incident from the back surface and emitted to the front surface side. On the other hand, it is an optical film having a directional scattering property in which light incident at a certain angle range from a direction inclined in one direction is scattered and emitted, and light from a direction perpendicular to a scattering plate surface (film surface) is emitted. Assuming that the incident angle is 0 °, the scattering start incident angle at which the incident light starts to be scattered and emitted is 5 ° to 10 °,
The scattered incident angle range S at which the incident light is scattered and emitted has a characteristic of greater than 30 °. In this embodiment, a scattering plate whose scattering incident angle range S is approximately 50 ° is used.

That is, the scattering plate 15 has a scattering property with respect to light incident from a specific direction at an incident angle within a specific angle range, and has a little scattering property with respect to incident light from outside the range. Although not shown, the scattering plate 15 used in this embodiment has a surface h perpendicular to the plate surface and along a specific direction.
At an angle of incidence of approximately 50 ° between a direction inclined 5 ° to 10 ° in one direction and a direction inclined 55 ° to 60 ° in the one direction with respect to the surface h with respect to the surface h. Incident light is scattered and emitted, and incident light from outside the range is emitted with little scattering.

The scattering plate 15 is provided with a direction including the scattered incident angle range S (one direction with respect to a surface h perpendicular to the scattering plate surface and along a specific direction) in a predetermined direction. Have been.

In this embodiment, the scattering plate 15 is oriented such that the direction including the scattered incident angle range S is directed toward the upper edge of the screen of the liquid crystal element 10, that is, opposite to the side where the viewing angle of the liquid crystal element 10 is present. It is provided in a state facing the direction of. Further, in this embodiment, the scattering plate 15 is disposed between the output side polarizing plate 14 of the liquid crystal element 10 and the liquid crystal cell 11.

On the other hand, the planar light source 20 disposed behind the liquid crystal element 10 is disposed so as to oppose the entire display area of the liquid crystal element 10, and to oppose both end faces of the light guide plate 21. Light source lamp 22 and a reflector 23 provided behind the light guide plate 21 and the light source lamp 22.

The light guide plate 21 is a transparent plate made of an allyl resin or the like, and the light from the light source lamp 22 is taken into the light guide plate 21 from the end face thereof, guided inside the light guide plate 21 and the surface thereof. The light is emitted as scattered light having substantially uniform light brightness from the whole.

The light collector 24 provided between the light source 20 and the liquid crystal element 10 collects light (scattered light) emitted from the light source 20 and enters the liquid crystal element 10. The irradiation light from the light source 20 has a small spread in the width direction of the light guide plate 21 (direction orthogonal to the light guide direction), and extends in the length direction of the light guide plate 21 (direction along the light guide direction). In this embodiment, a prism sheet formed by continuously forming a narrow band-shaped prism portion in the width direction on the entire surface of a transparent sheet made of an allyl resin or the like is used as the light collector 24 because the light spreads greatly. The light collecting plate (prism sheet) 24 is provided so that the length direction of each band-shaped prism portion is substantially parallel to the width direction of the light guide plate.
Irradiation light from the light guide plate 21 is condensed so that the spread in the length direction of the light guide plate 21 is reduced, and the front luminance of the irradiation light is increased.

In FIG. 1, the light collector 24 is provided close to the planar light source 20, but the light collector 24 is attached to the light exit surface of the light source 20 (the surface of the light guide plate 21). Alternatively, it may be provided by sticking to the incident side polarizing plate 13 of the liquid crystal element 10. Also, in FIG. 1, the light source 20 is shown separated from the liquid crystal element 10 in order to illustrate the scattered incident angle range S of the scattering plate 15, but it is desirable that the distance between the light source 20 and the liquid crystal element 10 be as small as possible. .

The liquid crystal display device achieves a wide viewing angle by providing a scattering plate 15 on the emission side of the liquid crystal element 10. According to this liquid crystal display device, the light emitted from the liquid crystal element 10 The scattering incident angle range S from the direction including the scattering incident angle range S with respect to the scattering plate 15.
Since the light incident at an angle within the range is scattered and emitted, the dependence of the voltage-transmittance characteristic of the liquid crystal element 10 on the observation direction is reduced.

That is, although the voltage-transmittance characteristic of the liquid crystal element 10 has an observation direction dependency, if the scattering plate 15 is provided on the emission side of the liquid crystal element 10, the scattering plate 15
Since the light incident at an angle within the scattered incident angle range S from the direction including the scattered incident angle range S is scattered and emitted, the observation angle when the display is observed from the emission direction of the scattered light is The degree of change of the transmittance with respect to the change becomes small, and the voltage-transmittance characteristic in this direction is relaxed.

The liquid crystal element 10 has a unique viewing angle determined by the viewing direction dependence of its voltage-transmittance characteristics. When viewed from a direction slightly deviated from the viewing angle direction F, the viewing angle in a very narrow range is obtained. The brightness of the display also changes drastically due to the change in the contrast, and the contrast is reduced and the gradation is inverted.
5 to alleviate the dependence of the voltage-transmittance characteristic on the observation direction, the viewing angle of the liquid crystal display device, that is, the range of the viewing angle where there is no grayscale inversion and the display can be observed with good contrast, The viewing angle is wider than the liquid crystal element 10 has.

The direction in which the viewing angle is widened depends on the scattering plate 15.
Is a direction opposite to the direction including the scattered incident angle range S, that is, the direction in which light incident at an angle within the scattered incident angle range S is scattered and emitted. In this embodiment, the scattering plate 15 Since the direction including the incident angle range S is provided toward the side having the viewing angle of the liquid crystal element 10, that is, toward the lower edge of the screen, the viewing angle from the frontal direction to the lower edge of the screen can be widened.

In this embodiment, when the angle of incidence of light from the direction perpendicular to the surface of the scattering plate 15 is 0 °, the scattering start incident angle at which the incident light starts to scatter and emerge is Since the scattering incident angle range S at which the incident light is scattered and emitted is as large as approximately 50 ° at 5 ° to 10 °, the viewing angle of the liquid crystal display device can be more effectively widened. .

In FIG. 1, A indicates the viewing angle of the liquid crystal element 10, and B indicates the viewing angle of the liquid crystal display device in which the scattering plate 15 is provided on the exit side of the liquid crystal element 10. In the device, the viewing angle from the frontal direction to the upper edge direction of the screen, that is, the viewing angle in the direction opposite to the side where the viewing angle of the liquid crystal element 10 is present is substantially equal to the viewing angle A of the liquid crystal element 10, but the viewing angle The viewing angle in the lower edge direction (the side where the viewing angle of the liquid crystal element 10 is present) is significantly wider than the viewing angle A of the liquid crystal element 10.

FIGS. 2 and 3 show that the liquid crystal display device without the scattering plate 15 and the liquid crystal display device of the above embodiment have gradations 1 to 3.
FIG. 2 is an observation angle-transmittance characteristic diagram from the frontal direction to the lower edge direction of the screen (the side where the viewing angle of the liquid crystal element 10 is present) when 8 gradations of gradation 8 are displayed. FIG. 3 shows the characteristics of the liquid crystal display device having no 15 and FIG. 3 shows the characteristics of the liquid crystal display device of the embodiment.

As shown in the viewing angle-transmittance characteristic in FIG. 2, in the liquid crystal display device without the scattering plate 15, the change in transmittance with respect to the change in the viewing angle (θ) from the frontal direction to the lower edge direction of the screen. When the viewing angle exceeds about 15 °, the grayscale inversion occurs on the low grayscale side, and the brightness of the halftone greatly decreases as the viewing angle increases. Therefore, there is no grayscale inversion. Moreover, the range of the viewing angle at which the display can be observed with good contrast is narrow. In this liquid crystal display device, when the observation angle is close to 40 °, the brightness of the high gradation sharply drops, and the entire screen becomes dark.

On the other hand, the scattering start incident angle is 5 ° to 1 °.
The viewing angle-transmittance characteristic of the liquid crystal display device of the above-described embodiment including the scattering plate 15 having a scattering incident angle range of about 50 ° at 0 °, as shown in FIG. And the change in brightness of each gradation with an increase in the viewing angle is gradual, so that an image with sufficient brightness and contrast can be observed over a wide viewing angle range near 50 °. .

As described above, in the liquid crystal display device of the above embodiment, the viewing angle-transmittance characteristic is greatly improved as compared with the liquid crystal display device without the scattering plate 15, and the viewing angle is widened.

Then, the liquid crystal display device has a liquid crystal element 1
Since the viewing angle is widened by providing the scattering plate 15 on the output side of the light emitting element 0, simple driving control and complicated alignment processing are not performed as in the conventional voltage control method or alignment control method. With the configuration, a wide viewing angle can be realized.

In the above embodiment, the planar light source 20 is disposed behind the liquid crystal element 10, and the light source 20 and the liquid crystal element 10 are arranged between the light source 20 and the liquid crystal element 10 to increase the front luminance of the light emitted from the light source 20. Since the light body (prism sheet) 24 is provided, it is possible to irradiate the liquid crystal element 10 with high-intensity light and to make the light incident on the scattering plate 15.
By increasing the brightness of the light exiting from No. 5 including the scattered light, a brighter display can be obtained.

In the first embodiment, the scattering plate 15
Is provided so that the direction including the scattered incident angle range S is directed in the direction opposite to the side where the viewing angle of the liquid crystal element 10 is located (the upper edge direction of the screen). S
May be provided in another direction, and the direction in which the viewing angle is widened is opposite to the direction including the scattered incident angle range S of the scattering plate 15, so that the scattering plate 15 If the direction including the incident angle range S is provided in a direction opposite to the direction in which the viewing angle is desired to be widened, the viewing angle can be widened in a desired direction.

FIG. 4 is a side view of a liquid crystal display device according to a second embodiment of the present invention. In this embodiment, the scattering plate 1 is used.
5 and the direction including the scattered incident angle range S
The viewing angle B of the liquid crystal display device is widened in the direction opposite to the viewing angle of the liquid crystal element 10 by providing the viewing angle B toward the side having the viewing angle (the lower edge direction of the screen). B is
The viewing angle from the frontal direction to the lower edge direction of the screen (the side where the viewing angle of the liquid crystal element 10 is present) is almost the same as the viewing angle A of the liquid crystal element 10, but the viewing angle from the frontal direction to the upper edge direction of the screen (liquid crystal element 1).
The viewing angle in the direction opposite to the side having a viewing angle of 0) is significantly wider than the viewing angle A of the liquid crystal element 10.

In the second embodiment, the scattering plate 15
Is provided so that the direction including the scattered incident angle range S is directed in the direction opposite to that of the first embodiment, and the other configuration is the same as that of the first embodiment. Description is omitted.

FIGS. 5 and 6 show the case where the liquid crystal display device without the scattering plate 15 and the liquid crystal display device of the second embodiment display eight gradations of gradations 1 to 8. 2 is a viewing angle-transmittance characteristic diagram from the frontal direction to the upper edge direction of the screen (the direction opposite to the side where the viewing angle of the liquid crystal element 10 is present). FIG. 2 shows the characteristics of the liquid crystal display device without the scattering plate 15. FIG. 3 shows the characteristics of the liquid crystal display device of the embodiment.

As shown in the viewing angle-transmittance characteristic of FIG. 5, the liquid crystal display device without the scattering plate 15 has a change in transmittance with respect to a change in the viewing angle (-θ) from the frontal direction to the upper edge of the screen. However, when the viewing angle exceeds about 15 °, grayscale inversion occurs on the high grayscale side, and as the viewing angle increases, the brightness from low grayscales to halftones rises significantly. There is no reversal and the range of the viewing angle at which the display can be observed with good contrast is extremely narrow. In this liquid crystal display device, when the observation angle is close to 35 °, the brightness of all gradations sharply drops, and the entire screen becomes dark.

On the other hand, when the scattering start incident angle is 5 ° to 1
The viewing angle-transmittance characteristic of the liquid crystal display device of the above-described embodiment including the scattering plate 15 having a scattering incident angle range of about 50 ° at 0 ° has a gradation even at an viewing angle of about 50 ° as shown in FIG. Is not inverted, and the change in brightness of each gradation with an increase in the observation angle (−θ) is gradual.
An image with sufficient brightness and contrast is observed over a wide observation angle range near 0 °.

FIG. 7 shows the liquid crystal display device without the scattering plate 15 and the liquid crystal display device of the second embodiment from the frontal direction to the upper edge of the screen (opposite to the side where the viewing angle of the liquid crystal element 10 has a viewing angle). ), The broken line shows the characteristics of the liquid crystal display device without the scattering plate 15, and the solid line shows the characteristics of the liquid crystal display device of the embodiment.

As shown in the viewing angle-contrast characteristic diagram, the liquid crystal display device without the scattering plate 15 has the viewing angle (-
Although the contrast is considerably high when θ) is small, the contrast is greatly reduced as the observation angle (−θ) increases.

On the other hand, in the liquid crystal display device of the above embodiment, the contrast when the observation angle (−θ) is small is lower than that without the scattering plate 15, but the contrast value is sufficient. Also, the change in contrast with the increase of the observation angle (-θ) is gradual,
An image with sufficient contrast is observed even at an observation angle near 50 °.

In the first and second embodiments,
Although only one scattering plate 15 is provided, if two scattering plates 15 are arranged on the emission side of the liquid crystal element 10 so that the directions including the respective scattered incident angle ranges S are oriented in different directions,
The viewing angle of the liquid crystal display device can be expanded in two directions.

FIG. 8 is a side view of a liquid crystal display device according to a third embodiment of the present invention. In this embodiment, the liquid crystal element 10
The two scattering plates 15 having the same characteristics are stacked and arranged between the exit-side polarizing plate 14 and the liquid crystal cell 11, and one of the scattering plates 15 (in FIG. Plate 15 is provided so that the direction including the scattered incident angle range S is directed in the direction opposite to the side where the viewing angle of the liquid crystal element 10 is located (the upper edge direction of the screen), and the other scattering plate (the liquid crystal cell in FIG. The liquid crystal element 10 is provided with a direction including the scattered incident angle range S facing the side where the viewing angle of the liquid crystal element 10 is present (the lower edge direction of the screen).

According to the liquid crystal display device of this embodiment, the viewing angle B is changed from the frontal direction to the lower edge direction of the screen (the side where the viewing angle of the liquid crystal element 10 is present) and to the upper edge direction of the screen (the liquid crystal element 10).
(The direction opposite to the side where the visual angle is) can be extended in both directions.

In the third embodiment, two scattering plates 15 each having a characteristic that the scattering start incident angle is 5 ° to 10 ° and the scattering incident angle range is approximately 50 ° are used. Since the directions including the range S are arranged in the opposite directions, and the other configuration is the same as that of the above-described first embodiment, the overlapping description will be omitted.

FIG. 9 is a viewing angle-transmittance characteristic diagram when the liquid crystal display device of the third embodiment displays eight gradations of gradations 1 to 8. FIG. 5B shows the viewing angle-transmittance characteristic from the frontal direction to the lower edge direction of the screen (the side where the viewing angle of the liquid crystal element 10 is present), and FIG. (In the direction opposite to the above)).

Like the viewing angle-transmittance characteristic, the liquid crystal display device of the third embodiment has a transmittance change characteristic with respect to a change in the viewing angle (θ) from a frontal direction to a lower edge direction of the screen. , The viewing angle from the frontal direction to the upper edge of the screen (-
θ), the change characteristics of the transmittance with respect to the change of
Even at an observation angle near 50 °, there is no grayscale inversion, and the change in brightness of each grayscale with an increase in the observation angle has a gradual characteristic. Therefore, even from the frontal direction to the lower edge direction of the screen, Also in the upper edge direction, an image with sufficient brightness and contrast is observed over a wide observation angle range close to 50 °.

In this embodiment, two scattering plates 15
Are arranged such that the directions including the respective scattered incident angle ranges S are opposite to each other. However, these scattering plates 15 are arranged such that the directions including the scattered incident angle ranges S are oriented in arbitrary directions. For example, if two scattering plates 15 are arranged so that the directions including the respective scattered incident angle ranges S are substantially orthogonal to each other, one direction from the frontal direction (for example, the lower edge direction of the screen) and the frontal direction The viewing angle can be widened to a direction shifted from the one direction by approximately 90 ° (for example, toward the right edge of the screen).

In the first to third embodiments, the scattering plate 15 is disposed between the output-side polarizing plate 14 and the liquid crystal cell 11, but the scattering plate 15 is disposed on the output side of the liquid crystal element. If so, it may be arranged on the exit surface of the exit side polarizing plate 14. However, in order to reduce the bleeding of the display image due to the scattering of light on the scattering plate 15, it is preferable to provide the scattering plate 15 between the emission-side polarizing plate 14 and the liquid crystal cell 11, as in each of the above embodiments. .

In each of the above embodiments, when the angle of incidence of light from the direction perpendicular to the surface of the scattering plate 15 is set to 0 °, the scattering start incident angle at which the incident light starts to be scattered and emitted is reduced. 5 to 10 °, and the scattering incident angle range S at which incident light is scattered and emitted is approximately 50 °. The scattering incident angle range S of the scattering plate 15 is 30 °. If the scattered incident angle range S is larger than 30 °, the viewing angle of the liquid crystal display device can be made sufficiently wide.

The scattering angle range S of the scattering plate 15
Is desirably selected in an angle range of more than 30 ° and 60 ° or less, and a more preferable scattered incident angle range S is approximately 50 ° selected in the above embodiment.

Further, in each of the above embodiments, the liquid crystal element 10
A light source 20 is disposed between the light source 20 and the liquid crystal element 10, and a light collector 24 for increasing the front luminance of light emitted from the light source 20 is provided between the light source 20 and the liquid crystal element 10. 2
4 may not be provided.

The light source for irradiating the liquid crystal element 10 with light is not limited to the planar light source 20 used in the above embodiment, but may be, for example, an electroluminescence panel or the like. And the illumination light from the light source
The light may enter the liquid crystal element 10 via a refraction optical path having a mirror or the like.

[0070]

According to the liquid crystal display device of the present invention, of the light emitted from the liquid crystal element, the scattered light is incident on the scattering plate provided on the emission side of the liquid crystal element from the direction including the scattered incident angle range. Since the light incident at an angle within the angular range is scattered and emitted, the dependence of the voltage-transmittance characteristic of the liquid crystal element on the viewing direction is reduced, and the viewing angle of the liquid crystal display device is reduced.
That is, the range of the viewing angle at which the display can be observed with good contrast without grayscale inversion is wider than the viewing angle of the liquid crystal element.

In this liquid crystal display device, the scattering plate has an incident angle of light of 0 ° from a direction perpendicular to the plate surface.
When the incident light starts scattering and emitting light, the scattering start incident angle is 5 ° to 10 °, and the scattering incident angle range at which the incident light is scattered and emitted is larger than 30 °. In addition, the viewing angle of the liquid crystal display device can be more effectively widened.

In the present invention, the viewing angle is widened by providing the above-mentioned scattering plate on the exit side of the liquid crystal element. Therefore, complicated drive control and complicated control like the conventional voltage control method and alignment control method are performed. Without the need to perform
A wide viewing angle can be realized with a simple configuration.

In the present invention, only one scattering plate may be provided, but two scattering plates are arranged on the emission side of the liquid crystal element so that the directions including the respective ranges of the scattered incident angles are different from each other. For example, the viewing angle of the liquid crystal display device can be expanded in two directions.

Further, in the present invention, a planar light source is disposed behind the liquid crystal element, and a light collector for increasing the front luminance of light emitted from the light source is provided between the light source and the liquid crystal element. Is provided, it is possible to irradiate the liquid crystal element with high-intensity light and to make the light incident on the scattering plate. You can get the display.

[Brief description of the drawings]

FIG. 1 is a side view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an observation angle-transmittance characteristic diagram from a direction directly in front of a liquid crystal display device without a scattering plate to a lower edge direction of a screen (a side where a viewing angle of a liquid crystal element is present).

FIG. 3 is a view showing an observation angle-transmittance characteristic in a direction from the front directly to the lower edge of the screen of the liquid crystal display device of the first embodiment.

FIG. 4 is a side view of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is an observation angle-transmittance characteristic diagram from a direction directly in front of a liquid crystal display device without a scattering plate to an upper edge direction of the screen (a direction opposite to the side where the viewing angle of the liquid crystal element is present).

FIG. 6 is an observation angle-transmittance characteristic diagram in a direction from the front directly to the upper edge of the screen of the liquid crystal display device of the second embodiment.

FIG. 7 is a diagram comparing the viewing angle-contrast characteristics of the liquid crystal display device without a scattering plate and the liquid crystal display device of the second embodiment from the frontal direction to the upper edge direction of the screen.

FIG. 8 is a side view of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is an observation angle-transmittance characteristic diagram in the lower edge direction and the upper edge direction of the liquid crystal display device according to the third embodiment from the front direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal element 11 ... Liquid crystal cell 13, 14 ... Polarizer 15 ... Scattering plate S ... Scattering incidence angle range of a scattering plate 20 ... Planar light source 24 ... Condenser

Claims (4)

[Claims] A liquid crystal element having a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-aligned, a liquid crystal element having a pair of polarizing plates disposed therebetween, and a scattering plate provided on an emission side of the liquid crystal element; The plate is incident at an angle within a certain angle range from the direction perpendicular to the surface of the scattering plate and inclined in one direction to the surface perpendicular to the scattering plate surface and out of the light emitted from the back surface and emitted to the front surface side. Having a directional scattering property in which the emitted light is scattered and emitted, and when the incident angle of light from a direction perpendicular to the surface of the scattering plate is set to 0 °, scattering of the incident light starts to be scattered and emitted. The incident angle is 5 ° to 10 °, and the range of the scattered incident angle at which the incident light is scattered and emitted is greater than 30 °. The scattering plate moves the direction including the scattered incident angle range in a predetermined direction. A liquid crystal display device, which is provided to face. 2. A scattering angle range of said scattering plate is approximately 50 °.
The liquid crystal display device according to claim 1, wherein 3. The liquid crystal device according to claim 1, wherein two scattering plates are provided on an emission side.
3. The liquid crystal display device according to claim 1, wherein directions including the respective scattered incident angle ranges are arranged in different directions. 4. A flat light source is disposed behind the liquid crystal element, and a light collector for increasing the front luminance of light emitted from the light source is provided between the light source and the liquid crystal element. The liquid crystal display device according to claim 1, wherein: