JPH05323289A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the visual angle characteristic of a display of the liquid crystal display device having a twisted nematic type liquid crystal by combining a orientation division and a phase different plate. CONSTITUTION:A light exit side panel 3 is divided to a region X and a region Y by the boundary line in the direction on a diagonal line. The rubbing direction of the substrate on the light incident side in the region X exists in an arrow (b) direction and the rubbing direction of the substrate on the light exit side exists in an arrow (a) direction in the region X. The rubbing direction of the substrate on the light incident side exists in the arrow (d) direction and the rubbing direction of the substrate on the light exit side exists in an arrow (c) direction in the region Y. The transmission axis of a polarizer 15 on the light incident side is so arranged as to be perpendicular to the rubbing directions (b), (d) of the substrate on the light incident side. The transmission axis of a polarizer 16 on the light exit side is perpendicular to the transmission axis of the polarizer 15 on the light incident side. The vibration plane of the exit side light of the liquid crystal panel 3 changes and the quantity of the light transmitted through the polarizer 16 on the light exit side increases when a phase difference plate 17 is arranged between the liquid crystal panel 3 and the polarizer 16 on the light exit side.

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 suitable for use in, for example, a projection display device.

[0002]

2. Description of the Related Art In recent years, projection type display devices using liquid crystals as home theaters and large screen displays have been developed. In such a projection display device, for example, as shown in FIG. 2, light is incident on the liquid crystal panel 3 from the light source 1 through the condenser lens 2, and the image light transmitted through the liquid crystal panel 3 is projected by the projection lens 4. It is designed to project on the screen 5. The condenser lens 2 is inserted to converge the image light transmitted through the liquid crystal panel 3 at one point in the projection lens 4. Therefore, light having an angle α enters the liquid crystal panel 3.

A liquid crystal display device comprises a liquid crystal panel in which liquid crystal is inserted between a pair of opposed transparent substrates, and a polarizing plate is provided outside these substrates. These substrates are provided with transparent electrodes that drive the liquid crystal. Twisted nematic liquid crystal is often used as the liquid crystal. The pair of substrates are rubbed in a direction perpendicular to each other, and the liquid crystal molecules are aligned in the rubbing direction of the substrates near the substrates, and twisted spirally from one substrate through the middle portion of the liquid crystal layer toward the other substrate. To go.
When no voltage is applied to the liquid crystal, the liquid crystal molecules are in the above-described state, and the incident light advances while rotating along the twist of the liquid crystal, and a white display is obtained. When a voltage is applied, the liquid crystal molecules rise, the birefringence action of the liquid crystal occurs, and black display can be obtained. In this way, while controlling the voltage applied to the liquid crystal, an image with bright and dark contrast is formed as a whole.

It is known that the twisted nematic liquid crystal has a viewing angle characteristic in which the display performance changes depending on the viewing direction of the viewer. For example, FIG. 7A shows a case where the liquid crystal panel 3 is viewed at a dip angle θ and a rotation angle φ. Dip angle θ
And the angle of rotation φ changes the viewing angle characteristics. FIG. 7 (B)
Shows a case where the solid line arrow shows the liquid crystal panel 3 at an angle of inclination of 40 degrees and a rotation angle φ of 90 degrees, and the broken line arrow shows the liquid crystal panel 3 at an angle of inclination of 40 degrees and a rotation angle φ of 90 degrees. It shows the case of viewing at an angle of 270 degrees. FIG. 7B shows a case where the liquid crystal molecules in the liquid crystal panel 3 are oriented so as to rise in the direction of the solid arrow when a voltage is applied. Since the rising angle of the liquid crystal molecules near the substrate is small due to the regulating force of the alignment film on the substrate, the liquid crystal molecules in the middle part of the liquid crystal layer rise mainly.

FIG. 8 shows the voltage-transmittance characteristics of the liquid crystal panel 3 depending on the viewing angles in three directions. The curve L shows the characteristics when the dip angle θ and the rotation angle φ are 0, that is, when the liquid crystal panel 3 is viewed from the center. Shows. The curve M corresponds to the case of viewing from the solid arrow in FIG. 7B, and the curve N corresponds to the case of viewing from the broken arrow in FIG. 7B. The curve L is a relatively smooth curve, but the curve M has a bump K. Therefore, in the curve M, when the voltage is increased from 0, the display gradually becomes black and becomes bright again at the bump K, a so-called display. Inversion phenomenon occurs. Therefore, if the applied voltage is determined with reference to the case where the liquid crystal panel 3 is viewed from the center, black display is provided when viewed from the center, while white display is provided when viewed from the solid arrow in FIG. 7B. Further, in the case of the curve N, the display is whitish as a whole as compared with the case of viewing from the center.

FIG. 10 shows a simple summary of the above. FIG. 10 shows a display screen 6 projected on the screen 5 of the projection display apparatus of FIG. 2, for example. On this display screen 6, the image of the person has a contrast between black hair and a white face at the center of the screen, but black and white of the hair and face are reversed at the upper position of the screen, and at the position of the lower part of the screen the whole image is totally reversed. It looks whitish. In FIG. 2, since incident light having an angle of 0 to α is incident on the liquid crystal panel 3, an image can be formed by the light that has vertically transmitted through the liquid crystal panel 3 at the center of the screen. Panel 3
Since an image is formed by the light obliquely transmitted through, the projected image has an in-plane distribution as shown in FIG.

Such a viewing angle characteristic of the display screen is also found in a direct-viewing type display device, but in order to improve this viewing angle characteristic, the display area is divided into two areas, and the alignment state of the liquid crystal in each area. It is known to perform so-called orientation division, which is different. It is said that the problems described above can be alleviated by performing orientation division. Display when this configuration is simply applied as a projection type will be described. FIG. 6 shows an example of orientation division in which the display area is divided into two. In (A), in the region X above the central boundary line, the rubbing direction of the substrate on the light incident side is the direction indicated by arrow b, and the rubbing direction of the substrate on the light emitting side is indicated by the arrow a. To be done. By this rubbing treatment, the liquid crystal molecules are twisted according to the arc-shaped arrow, and the liquid crystal molecules in the middle portion of the liquid crystal layer are in an alignment state of rising toward the upper end side of FIG. That is, the direction indicated by the upper double arrow in FIG. 6 is the same as the direction indicated by the double arrow in FIG. Therefore, in the upper area X of FIG. 6A, when the light coming from the direction of the double arrow is seen, when the light coming from the direction of the solid arrow of FIG. 7B is seen. As described above (as indicated by the curve M in FIG. 8), the display inversion phenomenon occurs. Further, in the region Y below the center boundary line in FIG. 6A, the rubbing direction of the substrate on the light incident side is the direction indicated by the arrow d, and the rubbing direction of the substrate on the light emitting side is the arrow. It is performed in the direction indicated by c. As a result, in the lower area Y of FIG. 6A, the display inversion phenomenon occurs when the light coming from the lower side is viewed.

FIG. 11A shows the characteristics of the projection type display at this time similarly to FIG. In FIG. 11 (A), the display difference between the upper position and the lower position of the projected display screen 6 disappears, but the display inversion phenomenon cannot be solved. FIG. 6B shows a case where the display inversion direction is opposite to that in FIG. 6A (double arrow). The characteristics of the display at this time are shown in FIG.
Shown in. In FIG. 11B, the display difference between the upper position and the lower position of the display screen 6 disappears, but the display is whitish as a whole.

[0009]

As described above, the liquid crystal display device having the twisted nematic liquid crystal has characteristics depending on the viewing angle of the display, and there is a limit to improving the viewing angle characteristic of the display only by the alignment division. An object of the present invention is to provide a liquid crystal display device in which the viewing angle characteristics of display are improved by combining alignment division and a retardation plate.

[0010]

A liquid crystal display device according to the present invention has a twisted nematic liquid crystal, and a display region is divided into a plurality of regions X and Y having different alignment states of the liquid crystal. Retardation film 17 covering a plurality of regions
Are arranged.

[0011]

In the above-mentioned structure, the liquid crystal panel having the divided orientation has a function of drawing out the characteristic originally possessed by the liquid crystal panel only on one side. The retardation film has the effect of suppressing the display inversion phenomenon. Therefore, when the inversion phenomenon of the conventional display is caused by the orientation division and the inversion phenomenon of the display is suppressed by the retardation film, a good display can be obtained on the front surface.

[0012]

FIG. 2 is a diagram showing a projection type display device applied to the present invention. As described above, this projection display device
Light is incident on the liquid crystal panel 3 from the light source 1 via the condenser lens 2, and the image light transmitted through the liquid crystal panel 3 is projected on the screen 5 by the projection lens 4. The condenser lens 2 is inserted to converge the image light transmitted through the liquid crystal panel 3 at one point in the projection lens 4. Therefore, light is incident on the liquid crystal panel 3 at the angle α.

The liquid crystal panel 3 is, for example, as shown in FIG. 7B, a liquid crystal 12 inserted between a pair of transparent substrates 10 and 11 facing each other. The liquid crystal 12 is a twisted nematic liquid crystal. 2 is a diagram in which the polarizers and the like are omitted, but FIG. 1 is a diagram in which the polarizers 15 and 16 and the retardation film 17 are arranged for ease of explanation.

In FIG. 1, the liquid crystal panel 3 is divided into an area X and an area Y by a boundary line in the diagonal direction. In the region X above the boundary line, the rubbing direction of the substrate on the light incident side is performed in the direction indicated by the arrow b, and the rubbing direction of the substrate on the light emitting side is performed in the direction indicated by the arrow a. By this rubbing treatment, the liquid crystal molecules are twisted according to the arc-shaped arrows, and the liquid crystal molecules in the middle portion of the liquid crystal layer are in an alignment state of rising toward the outside of the boundary line. That is, in the display based on light that rises in the direction indicated by the double arrow and travels in parallel with the direction of the double arrow, a display inversion phenomenon has conventionally occurred. In the area Y below the boundary line,
The rubbing direction of the substrate on the light incident side is performed in the direction indicated by arrow d, and the rubbing direction of the substrate on the light emitting side is performed in the direction indicated by arrow c. As a result, in the lower region Y, the liquid crystal molecules are twisted according to the arc-shaped arrow,
The liquid crystal molecules in the middle part of the liquid crystal layer are in an alignment state that rises toward the outside of the boundary line. That is, in the display based on light that rises in the direction indicated by the double arrow and travels in parallel with the direction of the double arrow, a display inversion phenomenon has conventionally occurred.

In FIG. 1, the transmission axis of the polarizer 15 on the light incident side is arranged so as to be perpendicular to the rubbing directions b and d of the substrate on the light incident side as indicated by the arrow. The transmission axis of the light exit side polarizer 16 is perpendicular to the transmission axis of the light entrance side polarizer 15. In the present invention, the retardation plate 17 is disposed between the liquid crystal panel 3 and the light emitting side polarizer 16. This retardation plate 17 has an optical axis in the direction of the arrow, and this optical axis is arranged parallel to the transmission axis of the polarizer 16 on the light emitting side. The retardation plate 17 causes a phase difference due to a speed difference between ordinary light and extraordinary light while the polarized light is transmitted at an angle with the optical axis.

Therefore, when no voltage is applied, a predetermined polarized light passes through the polarizer 15 on the light incident side and is incident on the liquid crystal panel 3, and is twisted by 90 degrees in the liquid crystal panel 3 and then the liquid crystal panel 3 is rotated.
Exit from. The vibrating surface of the polarized light at this time is the phase difference plate 17
Since it is parallel to the optical axis of and the transmission axis of the polarizer 16 on the light emitting side, they are transmitted and projected on the screen 5 by the projection lens 4.

When a voltage is applied, a predetermined polarized light is transmitted through the polarizer 15 on the light incident side and is incident on the liquid crystal panel 3, and is birefringent in the liquid crystal panel 3 so that it cannot be twisted by 90 degrees and is emitted from the liquid crystal panel 3. To do. At this time, the phase difference plate 17
Without it, the amount of polarized light transmitted through the polarizer 16 on the light emitting side is as shown in FIG. That is, the polarized light traveling in the direction of the double arrow shows the inversion of the display as shown by the curve M, and the polarized light traveling with the opposite inclination becomes whitish as shown by the curve N.

FIG. 9 shows the transmission characteristics of the polarizer 16 on the light emitting side in the case where the retardation plate 17 is provided.
M and N correspond to FIG. In the curve M of FIG. 9, the bump K, which has been the cause of the inversion of the conventional display, disappears, and the curve M approaches the characteristics of the curve L. Considering the cause of the bump K of the curve M in FIG. 8, for example, the action of birefringence occurs when the obliquely rising liquid crystal molecules in FIG. 7B and the light transmission direction indicated by the solid arrow coincide. Is small, and without the phase difference plate 17, the amount of outgoing polarized light of the liquid crystal panel 3 can be transmitted through the polarizer 16 on the light outgoing side. The liquid crystal molecules further rise from this state as the voltage rises, and the action of birefringence increases, and the polarizer 16 on the light emission side is increased.
The amount of light that passes through becomes large and becomes Kobu K.

The retardation plate 17 changes the directions of various vibration planes of the polarized light emitted from the liquid crystal panel 3. Therefore, the vibrating surface of the outgoing polarization of the liquid crystal panel 3 that could not pass through the light exit side polarizer 16 is changed so that the light exit side polarizer 16 can be transmitted to some extent. In this way, by arranging the retardation film 17, the vibrating plane of the outgoing polarization of the liquid crystal panel 3 is changed, and the amount of light transmitted through the polarizer 16 on the light outgoing side is somewhat increased overall.

FIG. 5 is a diagram showing the characteristics of the display screen 6 as in FIG. 11 (A). The alignment division of the liquid crystal panel 3 of FIG. 1 is oriented so that the liquid crystal molecules in each of the regions X and Y rise outward with respect to the boundary line, so that the same as in FIG. 11A without the retardation plate 17. In the image of the person, the black hair and the white face have a contrast in the center, but the black and white of the hair and the face are reversed at the upper position and the lower position.
However, in the present invention, since the phase difference plate 17 is provided, black and white inversion is eliminated, and as shown in FIG. 5, an image in which black hair and a white face are contrasted everywhere can be obtained.

FIG. 3 is a diagram showing a second embodiment of the present invention. Similar to the first embodiment, this projection display device includes a light source 1, a condenser lens 2, a light-incident side polarizer 15, a liquid crystal panel 3, a phase difference plate 17, and a light-exit side polarized light. Child 16
And a projection lens 4 and a screen 5. The liquid crystal panel 3 is aligned and divided substantially in the same manner as the liquid crystal panel 3 of FIG. 1 except that it is divided by a boundary line that extends horizontally at the center of the panel. The transmission axis of the polarizer 15 on the light incident side is arranged so as to be parallel to the rubbing directions b and d of the substrate on the light incident side. The transmission axis of the light exit side polarizer 16 is perpendicular to the transmission axis of the light entrance side polarizer 15. The optical axis of the phase difference plate 17 is arranged perpendicular to the transmission axis of the polarizer 16 on the light emitting side. The operation is similar to that of the first embodiment.

FIG. 4 is a diagram showing a third embodiment of the present invention. In this embodiment, the liquid crystal panel 3 is divided into two by a boundary line.
The orientation is divided into two regions X and Y. The orientation division method is the same as in the previous embodiment. However, if the screen is simply divided into two, the boundary line may be visible as an image. Therefore, in FIG. 4, two or more kinds of orientation directions are mixed in each pixel or in a small area in the vicinity 20 of the boundary line.

In the above examples, the slow axis taken in the stretching direction of the synthetic resin film is used as the optical axis of the retardation film 17, and this is combined with the transmission axes of the polarizers 15 and 16 for explanation. .. The present invention can be similarly used with the fast axis of the retardation plate 17 (perpendicular to the slow axis) and the absorption axes of the polarizers 15 and 16 as references.

For example, the phase difference plate 17 shown in FIG. 1 has an arrow as a fast axis and the phase difference plate 17 as shown in FIG. 3 has an arrow as a fast axis. Further, the polarizers 15 and 16 of FIG. 1 have the absorption axis and the retardation plate 17 has the slow axis, or the polarizers 15 and 16 of FIG. A structure in which the arrow of the phase difference plate 17 is used as a fast axis is possible.
In addition, the configuration is such that the arrows of the polarizers 15 and 16 in FIG. 3 are absorption axes and the arrow of the retardation plate 17 is a slow axis, or the arrows of the polarizers 15 and 16 in FIG. A structure in which the arrow of the phase difference plate 17 is used as a fast axis is possible.

For example, FIG. 12 shows a configuration similar to FIG. 1, and FIG. 13 shows a configuration similar to FIG.
Also, in FIG. 13, the arrows of the polarizers 15 and 16 indicate the transmission axis, and the arrow of the retardation film 17 indicates the optical axis. The optical axis can be a slow axis or a fast axis.

In FIG. 12, the polarizer 15 on the light incident side is shown.
Has a transmission axis parallel to the rubbing directions b and d of the light incident side substrate of the liquid crystal panel 3, and the transmission axis of the light emitting side polarizer 16 is perpendicular to the transmission axis of the light incident side polarizer 15. is there.
The slow axis or the fast axis of the retardation plate 17 is parallel to the transmission axis of the light exit side polarizer 16.

In FIG. 13, the polarizer 15 on the light incident side is shown.
Has a transmission axis perpendicular to the rubbing directions b and d of the light incident side substrate of the liquid crystal panel 3, and the transmission axis of the light emitting side polarizer 16 is perpendicular to the transmission axis of the light incident side polarizer 15. is there.
The slow axis or the fast axis of the retardation plate 17 is perpendicular to the transmission axis of the light exit side polarizer 16.

[0028]

As described above, according to the present invention,
It is possible to obtain a high-contrast display on the entire screen by eliminating the inversion and whitishness of the display that is caused by the conventional viewing angle.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a projection display device.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a display obtained in the first embodiment.

FIG. 6 is a diagram showing orientation division.

FIG. 7 is a diagram illustrating viewing angle characteristics of a liquid crystal display device.

FIG. 8 is a diagram showing viewing angle characteristics of a liquid crystal display device.

FIG. 9 is a diagram showing viewing angle characteristics of the liquid crystal display device of the example.

FIG. 10 is a diagram showing a conventional display.

FIG. 11 is a diagram showing a conventional display.

FIG. 12 is a diagram showing a fourth embodiment of the present invention.

FIG. 13 is a diagram showing a fifth embodiment of the present invention.

[Explanation of symbols]

 3 ... Liquid crystal panel 15, 16 ... Polarizer 17 ... Phase difference plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Hamada 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (3)

[Claims] 1. A plurality of regions (X, having a twisted nematic liquid crystal, wherein display regions have different alignment states of the liquid crystals.
The liquid crystal display device is characterized in that the retardation film (17) is divided into Y) and covers the plurality of regions. 2. The liquid crystal molecules in each of the plurality of regions are oriented so as to rise outward with respect to a boundary line that divides the plurality of regions with the application of an electric field. The described liquid crystal display device. 3. The liquid crystal display device according to claim 1, wherein two or more kinds of alignment directions are mixed in the vicinity of a boundary line dividing the plurality of regions.