JP2000047195A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dot displaying liquid crystal display device permitting a negative mode display with high contrast and fine visibility. SOLUTION: Fixed places of a liquid crystal cell 21 in which liquid crystal molecules are twistedly oriented in directions ranging downwardly from about 90 deg. constitute a display region 29 where voltages are selectively applied and a background region 30 where voltages are not applied. Two polarizing plates 31, 32 are located so that a transmission axis 31a of the front side polarizing plate 31 and a transmission axis 32p of the rear side reflective polarizing plate 32 are parallel with each other. And, a color backlight 33 is located on the back surface of the rear side reflective polarizing plate 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative display type liquid crystal display device of a dot display type with improved visibility.

[0002]

2. Description of the Related Art In a negative display type liquid crystal display device, when a voltage is not applied to a liquid crystal layer, that is, in an initial alignment state of liquid crystal molecules, light is produced by a cooperative action of a polarizing action by a polarizing plate and an optical rotation action by a liquid crystal layer. Block the transmission of light.

[0003]

However, instead of forcibly blocking the progress of light by disposing a light-blocking member, the progress of light is prevented by utilizing the polarization action and the optical rotation action of light. Therefore, it is difficult to completely block light. In particular, in a negative-type liquid crystal display device mounted on a vehicle, a high-luminance backlight is used. Therefore, a negative-type dot display-type liquid crystal display in which a simple-matrix liquid crystal display device in which signal electrodes and scanning electrodes cross each other is time-divisionally driven. In the device, light leakage from the background portion easily occurs due to crosstalk.
An object of the present invention is to provide a dot display type liquid crystal display device capable of obtaining a negative display with high contrast and good visibility.

[0004]

According to the present invention, a pair of substrates are opposed to each other with a liquid crystal interposed therebetween, and a plurality of stripe-shaped electrodes are formed on opposite surfaces of each substrate in directions orthogonal to each other. At the same time, an alignment film is applied to cover these electrodes, and an alignment process is performed on each alignment film so that the liquid crystal molecules are arranged to be twisted from one substrate side to the other substrate side in a range of 80 ° to 120 °. And a polarizing plate having a transmission axis for transmitting incident light of a polarization component along one direction, and a polarizing plate disposed on the surface side of the liquid crystal cell, and one of directions substantially orthogonal to each other. And a transmission axis for transmitting the incident light of the polarization component along the other direction, the transmission axis being parallel to the transmission axis of the polarizing plate. On the back side of the liquid crystal cell It comprises a reflective polarizing plate disposed and a display member disposed on the back side of the reflective polarizing plate.

According to the present invention, the background area where no voltage is applied to the liquid crystal of the liquid crystal cell is mirror-displayed, and the mirror surface is less noticeable in brightness variation. Therefore, even if the brightness varies due to crosstalk, the contrast is high and the visibility is high. A high good negative display is obtained.

[0006]

FIG. 1A shows a main part of a liquid crystal display device according to an embodiment of the present invention. This liquid crystal display device includes a liquid crystal cell 21 of a simple matrix type. The liquid crystal cell 21 has a pair of substrates 22 and 23 opposed to each other with a liquid crystal 24 interposed therebetween.
23, a plurality of stripe-shaped electrodes 2
5 and 26 are formed in directions orthogonal to each other, and alignment films 27 and 28 are attached so as to cover the electrodes 25 and 26.
It has a structure in which an alignment process is performed so as to be twisted over a range of 80 ° to 120 ° from one side toward the other substrate 23 side. However, in this embodiment, the twist angle is set to approximately 90 °. Liquid crystal cell 2
1 includes a display area 29 and a background area 30.
In this case, the display area 29 is an area where a voltage is applied to the liquid crystal 24 in the area 29. Background area 30
Is a region where no voltage is applied to the liquid crystal 24 in the region 30. A polarizing plate 31 is arranged on the surface side of the liquid crystal cell 21. On the back side of the liquid crystal cell 21, a reflective polarizing plate 32 is arranged. On the back side of the reflective polarizing plate 32,
A color backlight 33 is provided as a display member. The color backlight 33 includes a combination of a color filter and a white light backlight, a white light backlight subjected to color printing, color electroluminescence or a color light emitting diode.

Next, FIG. 2 is a perspective view for explaining the reflective polarizing plate 32. As shown in FIG. This reflective polarizing plate 32
Are a reflection axis 32s and a transmission axis 32p that are substantially orthogonal to each other.
And reflects incident light of a polarization component (hereinafter, referred to as S-polarized component) along the reflection axis 32s, and transmits incident light of a polarization component (hereinafter, referred to as P-polarized component) along the transmission axis 32p. It has become. That is, when light containing both the S-polarized light component along the reflection axis 32s and the P-polarized light component along the transmission axis 32p is incident from the back side of the reflective polarizing plate 32, the reflection axis 32s of the incident light Is reflected by the reflective polarizer 32, and the P-polarized component light along the transmission axis 32p is transmitted through the reflective polarizer 32. It should be noted that the same characteristic is obtained for the incident light from the surface side of the reflective polarizing plate 32.

Next, referring to FIG. 1B, the liquid crystal cell 2
A description will be given of a case where the relationship between the alignment processing directions of the two alignment films 27 and 28 and the optical axis such as the transmission axis of the reflective polarizing plate 32 is viewed from the front side. Orientation processing direction 2 of alignment film 28 on front side
8a is a direction from the lower left side to the upper right side.
The alignment processing direction 27a of the alignment film 27 on the back side is a direction from the upper left to the lower right. Therefore, the liquid crystal molecules of the liquid crystal 24 in this case are twist-oriented at a twist angle of approximately 90 ° in the clockwise direction indicated by the arrow 24a from the back side to the front side. The transmission axis 31a of the polarizing plate 31 is substantially parallel to the alignment direction 28a of the alignment film 28 on the front side, and the absorption axis 31b is orthogonal. The transmission axis 32p of the reflective polarizing plate 32 is substantially orthogonal to the alignment processing direction 27a of the alignment film 27 on the back surface side. Therefore, the reflection axis 32s of the reflective polarizing plate 32 is substantially parallel to the alignment processing direction 27a of the alignment film 27 on the back surface side.
Thus, the transmission axis 31a of the polarizing plate 31 and the reflective polarizing plate 32
, A negative dot display type liquid crystal display device in which the transmission axis 32p is disposed in parallel with the liquid crystal display device is obtained.

Next, the display operation of the liquid crystal display device will be described. In the background region 30 where no voltage is applied, the incident external light passes through the polarizing plate 31 to become linearly polarized light, undergoes an optical rotation in the process of passing through the liquid crystal cell 21, and is rotated by approximately 90 °. However, since the linear polarization plane (oscillation plane) of the incident light at this time is in the direction along the reflection axis 32s of the reflection polarization plate 32,
Here, the light is specularly reflected (specular reflection). This reflected light is subjected to an optical rotation in the process of transmitting through the liquid crystal cell 21 again, and is almost 9
The light is rotated by 0 °, and then passes through the polarizing plate 31 and is emitted to the front side. Further, of the light from the color backlight 33, the light of the P-polarized component along the transmission axis 32p of the reflective polarizer 32 is transmitted through the reflective polarizer 32 and then subjected to an optical rotation in the process of transmitting through the liquid crystal cell 21. About 90 ° rotation,
Next, the light is absorbed by the polarizing plate 31. Color backlight 3
The light of the S-polarized component along the reflection axis 32s of the reflective polarizer 32 among the light from 3 is reflected by the reflective polarizer 32. Therefore, the background region 30 is mirror-displayed by the external light that is specularly reflected by the reflective polarizing plate 32. On the other hand, in the display area 29 to which a voltage is applied, the transmission axis 32 of the reflective polarizing plate 32 of the light from the color backlight 33 is used.
The light of the P-polarized component along p passes through the reflective polarizer 32, then passes through the region of the liquid crystal cell 21 to which the voltage is applied without being affected by the optical rotation, and then passes through the polarizer 31 to reach the surface. Emitted to the side. Therefore, the display area 2
The display of 9 is a display by the backlight light.

As described above, according to the liquid crystal display device of the present embodiment, a simple matrix type dot display with a mirror background can be obtained, and as a result, display defects due to crosstalk, which is a drawback of the simple matrix type display, are alleviated. be able to. In other words, since the luminance of the background mirror is less noticeable, there is little possibility of display failure even if the luminance varies due to crosstalk. As a result, a favorable negative display with high contrast can be obtained.

Note that the display of the mirror background as in the above embodiment is not suitable for a liquid crystal display device, because a certain degree of decrease in visibility is unavoidable instead of obtaining novelty. . In such a case, the polarizing plate 31
An anti-glare treatment may be applied to the surface of the substrate. This allows
The degree of the mirror surface of the background area 30 is appropriately suppressed, and the visibility of the display is improved while the background is the mirror surface. Further, the display member is not limited to a backlight, and a colored plate or a black plate colored in a desired color can be used. In this case, a reflection type negative dot liquid crystal display device is obtained.

[0012]

As described above, according to the present invention, the background area where no voltage is applied to the liquid crystal of the liquid crystal cell is mirror-displayed, and the mirror-surface is less noticeable in luminance variation, so that the luminance varies due to crosstalk. However, a favorable negative display with high contrast and high visibility can be obtained.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a main part of a liquid crystal display device according to an embodiment of the present invention, and FIG. FIG.

FIG. 2 is a perspective view illustrating a reflective polarizing plate.

[Explanation of symbols]

 Reference Signs List 21 liquid crystal cell 24 liquid crystal 29 display area 30 background area 31 polarizing plate 32 reflective polarizing plate 33 color backlight

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H090 LA09 MA04 MA06 2H091 FA02Z FA08X FA08Z FA14Z FA37X FA41Z FC25 FD08 HA07 LA03 LA16 LA17 LA18 5C094 AA03 AA06 BA44 CA23 EA05 ED11 ED12 ED14 HA05

Claims (4)

[Claims] A pair of substrates are opposed to each other with a liquid crystal interposed therebetween, and a plurality of stripe-shaped electrodes are formed on opposite surfaces of each substrate in directions orthogonal to each other, and cover the electrodes with an alignment film. Is applied, and the liquid crystal molecules are formed on each alignment film in an angle of 80 ° from one substrate side to the other substrate side.
A liquid crystal cell that has been subjected to an alignment treatment for twisting over a range of 120 °, and a transmission axis that transmits incident light of a polarization component along one direction, and is disposed on the surface side of the liquid crystal cell. A polarizing plate, having a reflection axis that reflects incident light of a polarization component along one direction of directions substantially orthogonal to each other and a transmission axis that transmits incident light of a polarization component along the other direction, A reflective polarizing plate disposed on the back side of the liquid crystal cell such that a transmission axis is parallel to the transmission axis of the polarizing plate; and a display member disposed on the back side of the reflective polarizing plate. A liquid crystal display device characterized by the above-mentioned. 2. The liquid crystal display device according to claim 1, wherein the display member is a backlight that emits predetermined colored light. 3. The liquid crystal display device according to claim 1, wherein the display member is a colored plate colored in a predetermined color. 4. The liquid crystal display device according to claim 1, wherein a surface of said polarizing plate is subjected to an anti-glare treatment.