JPH0836175A - Liquid crystal color display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal color display device having high luminance. CONSTITUTION:In a twist nematic type or field-controlled double refraction type liquid crystal color display device, the color filter disposed in the incident side of a liquid crystal cell 16 is replaced by a phosphor 24 in which R, G and B dots are arranged in a specified state. By irradiating the phosphor 24 with UV 26 through the back side, the phosphor 24 emits visible rays. Thus, the energy of UV 26 is fully used without loss and the luminance three times as high is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal color display device, and in particular, a liquid crystal cell having electrodes on both sides is arranged between an incident side polarizing plate and an emitting side polarizing plate to form an incident side polarizing plate. The present invention relates to a liquid crystal color display device in which light is emitted from the back side.

[0002]

2. Description of the Related Art A conventional liquid crystal color display device utilizing the twisted nematic effect has a structure as shown in FIG. That is, the liquid crystal cell 1 is provided with the alignment films 2 and 3 on both surfaces thereof, the pixel electrode 4 is formed on the upper surface of one alignment film 2, and the counter electrode 5 is formed on the outer surface of the alignment film 3 on the opposite side. The liquid crystal cell 1 is formed by these electrodes 4 and 5.
The voltage is applied to. A color filter 6 having dots of three primary colors R, G, and B is arranged on the back side of the liquid crystal cell 1, and glass plates 7 and 8 are arranged on both sides thereof. Board 9
The incident side polarization plate 10 is arranged on the back side of the glass plate 8 and the illumination light 11 is emitted from the back side of the incidence side polarization plate 10.

[0003]

As the illumination light 11 emitted from the back side of the incident side polarization plate 10, the light of a white light emitting fluorescent tube in which phosphors of R, G and B colors are mixed is used. Therefore, such illumination light is color-separated by the color filter 6 corresponding to each pixel of the liquid crystal cell 1. Therefore, the R dot portion of the color filter 6 absorbs G and B light, and the G dot portion absorbs the G and B light.
The light of R and B is absorbed, and in the portion of the dot of B, R,
Each G light is absorbed. Therefore, only 1/3 of the energy of the illumination light 11 can be used by the color filter 6, and therefore, when a predetermined white light emitting fluorescent tube is used, the brightness cannot be sufficiently improved. there were.

The present invention has been made in view of the above problems, and is a liquid crystal color in which the energy of incident light for illumination is effectively used without waste, thereby realizing high-luminance color display. It is intended to provide a display device.

[0005]

According to the present invention, a liquid crystal cell having electrodes on both sides is arranged between an incident side polarization plate and an emission side polarization plate, and a pixel provided on each side of the liquid crystal cell. The present invention relates to a liquid crystal color display device in which a voltage applied to a liquid crystal cell is controlled by an electrode and a counter electrode, and light is emitted from the back side of an incident side polarizing plate to perform color display. In particular, the present invention is suitable for use in a single-plate type liquid crystal color display device in which the optical properties of liquid crystal are changed by utilizing the twist nematic effect or the electric field control birefringence effect.

The present invention is characterized in that a phosphor having dots of three primary colors R, G and B is used in place of the conventional color filter, and such a phosphor is used on the incident side. It is arranged on the back side of the polarizing plate, and by irradiating a back light such as ultraviolet rays from the back side of the panel, visible light of R, G, B is emitted by the phosphor to perform color display.

When the pixel electrode is formed on the exit side surface of the liquid crystal cell and the counter electrode is formed on the entrance side surface, the R, G and B dots of the phosphor are opposed to the counter electrode. It is preferable that the dots of R, G, B correctly emit visible light of each color of R, G, B according to each pixel.

A phosphor having R, G, and B dots is provided in place of the color filter, and the phosphor is used to emit visible light by ultraviolet rays emitted from the back side. It is preferable that the side glass plate be made of a UV-transparent glass and that the viewer side, that is, the front side of the liquid crystal panel, be made of a UV-cut glass so that UV rays do not leak.

In the present invention, when it is difficult to make the distance between the phosphor used in place of the color filter of the liquid crystal color display device and the pixel portion of the liquid crystal close in the manufacturing process, the front side of the phosphor It is preferable to dispose a microlens corresponding to each pixel. The microlens has the effect of squeezing the visible light generated by the fluorescent substance and preventing leakage of R, G, and B light. In this case, the microlens may be on the front surface side or the back surface side of the incident side polarization plate.

In the present invention, in order to further increase the brightness, an optical filter that reflects visible light and transmits light from a light source that emits fluorescent material such as ultraviolet rays is provided on the back side of the fluorescent material. Is possible. That is, the R, G, and B visible lights generated by the phosphor are reflected on the back side and emitted to the ultraviolet light source side, and an optical filter that transmits the ultraviolet light from the light source side is provided on the light source side of the phosphor. In this case, the visible light is returned to the viewer side on the front side of the liquid crystal panel, thereby improving the brightness.

[0011]

According to the present invention, when the phosphor is irradiated with light such as ultraviolet rays emitted from the backlight on the back side of the liquid crystal panel, the respective dots of R, G and B of the phosphor correspond to the corresponding colors. Emits visible light. Therefore, by controlling the voltage applied to the liquid crystal cell via the electrodes on both sides,
Control is performed as to whether the light from each of the R, G, and B dots of the phosphor is emitted to the front side or blocked, whereby a predetermined liquid crystal color display is performed.

[0012]

1 shows a liquid crystal color display device according to a first embodiment of the present invention, in which a liquid crystal cell 16 has alignment films 17 and 18 on both sides thereof. A pixel electrode 19 is provided on the front surface side of the liquid crystal cell 16, and a counter electrode 20 is attached to the opposite surface. A glass plate 21 is arranged on the front side of the liquid crystal cell 16, and an emission side polarizing plate 22 is arranged on the outer surface side of the glass plate 21.

On the other hand, on the back side of the liquid crystal cell 16, an incident side polarization plate 23 is arranged. And the incident side polarization plate 2
A phosphor 24 is disposed on the back side of the No. 3. The phosphor 24 is a phosphor in which dots of R, G, and B are alternately formed at predetermined intervals. A glass plate 25 is attached to the back side of the phosphor 24, and the ultraviolet light 6 from the light source is emitted from the glass plate 2
The phosphor 24 is irradiated through the light source 5. Quartz glass or the like may be used as the glass plate 25.

In the twisted nematic liquid crystal color display device having such a structure, ultraviolet rays 26 are incident from the rear side, that is, the lower side in FIG. The ultraviolet rays pass through the glass plate 25 made of quartz glass or the like, and are irradiated to the R, G, B dots of the phosphor 24 corresponding to each pixel,
As a result, each dot of the phosphor 24 emits R, G, and B visible light.

The visible lights R, G and B, which are generated by the phosphor 24 in this way, pass through the polarizing plate 23 and are converted into linearly polarized light. Then, the light enters the liquid crystal cell 16. When linearly polarized light passes through the liquid crystal cell 16,
The polarization direction is twisted by 90 ° due to the twist of the spiral (twisted nematic effect).

The liquid crystal cell 16 has electrodes 19 and 20 on both sides.
When a voltage is applied, the major axis direction of the liquid crystal molecules begins to tilt in the direction of the electric field, and when a predetermined voltage is applied, the liquid crystal molecules become a homeotropic array arranged in the electrolytic direction and the spiral twist is eliminated and the liquid crystal penetrates. Like Then, the untwisted linearly polarized light passes through the glass plate 21 from the liquid crystal cell 16 and reaches the emission side polarization plate 22. However, since the polarization direction of the polarizing plate 22 is orthogonal to the incident side polarizing plate 23, this light is blocked by the emitting side polarizing plate 22. Therefore, in FIG. 1, this light cannot be seen from above. .

When no voltage is applied to each dot of the liquid crystal cell 16, the light emitted by the phosphor 24 and linearly polarized by the polarizing plate 23 is transmitted through the liquid crystal cell. Twists 90 °. Therefore, the visible light can be seen from the exit side through the exit side polarization plate 22 as it is. .

In the above embodiment, the polarization directions of the incident side polarization plate 23 and the emission side polarization plate 22 arranged on both sides of the liquid crystal cell 16 are set to be at right angles to each other. , 23 are arranged so that the polarization directions thereof are parallel to each other, the relationship between the transmission and blocking of light is just opposite to that in the case where they are orthogonal to each other. When the voltage is applied, the light is transmitted and the voltage is applied. If it comes to shut off.

In such a liquid crystal color display device,
If the thickness of the polarizing plate 23 is made smaller than the size of the pixel, most of the visible light scattered and emitted by each dot of the phosphor 24 can be made incident on the corresponding pixel, and the phosphor 24 can be formed.
Therefore, it is possible to provide a liquid crystal color display device in which the efficiency of using light emitted from is extremely high.

As described above, in the liquid crystal color display device of this embodiment, the light source for emitting the ultraviolet rays 26 and the liquid crystal cell 16 are used.
And a visible light generating means composed of R, G, and B phosphors attached to the light source side in the vicinity of the pixel corresponding to each pixel, and color display is performed by these means. In the conventional single-plate color filter type display device, only one of the R, G, and B lights passes through the color filter, so only 1/3 of the incident light amount is used.

On the other hand, in this embodiment, the phosphor 24 is used in place of the color filter, and most of the energy of the incident ultraviolet light is emitted from the R, G, and B dots of the phosphor 24. It is designed to be used as energy. Therefore, when the energy is the same when used as a backlight, it is about 3
It is possible to obtain double the brightness.

The above embodiment relates to a liquid crystal color display device utilizing the twisted nematic effect, but is also applied to other types of liquid crystal color display device, for example, a liquid crystal color display device utilizing the electric field control birefringence effect. It is possible.

Next, a second embodiment will be described with reference to FIG. This embodiment is characterized in that a micro lens 31 is provided. In the structure shown in FIG. 1, the structure of the phosphor 24 and the polarizing plate 23 cannot be made thin, or it cannot be adhered to the liquid crystal cell 16 in the manufacturing process.
It is preferable to provide the microlens 31 when 0 is inserted. The microlens 31 is R of the phosphor 24,
The fluorescent substance 2 is provided corresponding to each of the G and B dots, and the visible light generated from these dots is narrowed down.
The visible light can be made incident on the pixels of the liquid crystal cell 16 corresponding to the R, G, and B dots of No. 4.

If the microlens 31 is brought close to the phosphor 24, a larger amount of visible light energy of the phosphor 24 spread in a wide angle can be collected. The microlens 31 has a function of narrowing the visible light emitted from the phosphor 24 so as to pass through the corresponding pixel even when the visible light does not leak to the adjacent pixel. It also contributes to the improvement of the effective aperture ratio of the liquid crystal color display device.

If the aperture is insufficient, the phosphor 24
Partition walls 32 may be provided between the respective dots R, G, B. Further, in the embodiment shown in FIG. 2, the microlens 31 is provided on the exit side of the incident side polarizing plate 23, but the positional relationship between the microlens 31 and the incident side polarizing plate 23 may be reversed. That is, the visible light that has passed through the microlens 31 may be linearly polarized by the incident side polarization plate 23.

FIG. 3 shows a third embodiment. The feature of this embodiment resides in the optical filter 36. That is, the optical filter 36 is arranged so that the ultraviolet rays 26 are transmitted immediately before entering the phosphor 24.

The optical filter 36 may be composed of, for example, a vapor deposition multi coat filter. Such a filter 3
Reference numeral 6 is a filter that transmits the ultraviolet ray 26 and reflects visible light. Therefore, the ultraviolet light incident through the glass plate 25 passes through the filter 36, but the visible light generated by the phosphor 24 that returns to the light source side is reflected by the filter 36 toward the observer side, that is, the emitting side. Will be done. Therefore, the use efficiency of visible light is further improved by such an optical filter 36, and the brightness is further improved.

[0028]

As described above, according to the present invention, a phosphor having dots of R, G, and B arranged in a predetermined state is provided on the back side of the incident side polarizing plate, and the fluorescent light is emitted by the light from the back side. The body is designed to emit visible light.

Therefore, the light energy of the light source light emitted from the rear side can be utilized without waste, and display can be performed with high brightness. In principle, a liquid crystal color display device having about 3 times the brightness of the conventional liquid crystal color display device. It becomes possible to provide.

By disposing microlenses corresponding to the dots of R, G, and B of the phosphor on the back side of the liquid crystal cell and on the front side or the back side of the incident side polarizing plate, the microlens can be used to emit light from the phosphor. The visible light can be narrowed down, and it is possible to improve the bleeding of adjacent colors and the aperture ratio. In addition, by forming a reflective coating layer that transmits light from the light source and reflects visible light from the phosphor on the surface of the phosphor on the light source side, visible light that tries to return to the light source side is also reflected to the emission side. It is possible to improve the brightness.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a liquid crystal color display device of a first embodiment.

FIG. 2 is an enlarged sectional view of a liquid crystal color display device of a second embodiment.

FIG. 3 is an enlarged cross-sectional view of a liquid crystal color display device of a third embodiment.

FIG. 4 is an enlarged cross-sectional view of a conventional liquid crystal color display device.

[Explanation of symbols]

 16 Liquid crystal cells 17 and 18 Alignment film 19 Pixel electrode 20 Counter electrode 21 Glass plate 22 Emission side polarizing plate 23 Incident side polarizing plate 24 Phosphor 25 Glass plate 26 Ultraviolet light 30 Shielding glass plate 31 Microlens 32 Partition wall 36 Optical filter

Claims (4)

[Claims] 1. A liquid crystal color display in which a liquid crystal cell having electrodes on both sides is arranged between an incident side polarizing plate and an emitting side polarizing plate, and light is irradiated from the back side of the incident side polarizing plate. In the device, a liquid crystal color display device comprising a phosphor having R, G, B dots arranged in a predetermined state on the back surface side of the incident side polarization plate. 2. A pixel electrode is formed on the exit side surface of a liquid crystal cell, and a counter electrode is formed on the entrance side surface, and R, G, and B dots of the phosphor are arranged corresponding to the pixel electrode. The liquid crystal color display device according to claim 1, wherein the liquid crystal color display device is a liquid crystal color display device. 3. A microlens corresponding to the dots of R, G, B of the phosphor is arranged on the back side of the liquid crystal cell and on the front side or the back side of the incident side polarizing plate. The liquid crystal color display device according to claim 1 or 2. 4. A liquid crystal color display device, characterized in that a reflective coat layer is formed on the surface of the phosphor on the light source side to transmit light from the light source and reflect visible light from the phosphor.