JP2002328355A - Reflection type color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a field-sequential color liquid crystal display device a reflection type. SOLUTION: The reflection type color liquid display device 10 comprises a liquid crystal cell 12 controlled by a field-sequential method and a reflection device 14 arranged at the back face of the liquid crystal cell 12. In the reflection device 14, a band-shaped reflection sheet 18 having reflection regions 18R, 18G and 18B which reflect 3 colors, R/G/B, are arranged. The reflection sheet 18 is driven by a driving device 20, thus sequentially transferring the reflection regions 18R, 18G, 18B to the backside of the liquid crystal cell 12. The liquid crystal cell 12 is synchronized with the colors of the reflection regions and the light transmissiveness thereof is controlled by the order of the colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type color liquid crystal display device of a field sequential system.

[0002]

2. Description of the Related Art In recent years, a color liquid crystal display device using a field sequential method has been proposed with the advantages of energy saving, cost reduction and improvement of resolution.

The principle of color liquid crystal display by the field sequential method is based on a liquid crystal display (hereinafter referred to as LCD).
Is used as an optical shutter, and is illuminated by a light source sequentially lit from the back of the LCD to switch the light source color at a high speed.

[0004]

However, as described above, such a field sequential type color liquid crystal display device needs to be illuminated by a light source which is lit sequentially from the back of the LCD, and power consumption by the light source is large. However, there is a problem that it is not suitable for a liquid crystal display device of a portable electronic device driven by a battery.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a reflection type color liquid crystal display device which consumes little power even though it is a field sequential system.

[0006]

SUMMARY OF THE INVENTION The present inventor has incorporated a reflection sheet having reflection areas of different colors into the back side of an LCD,
It has been found that a reflective color liquid crystal display device of a field sequential system can be configured by moving the LCD in synchronization with switching of a light and dark pattern corresponding to each color display of the LCD.

According to the present invention, a liquid crystal cell of a field sequential system in which light transmittance is sequentially controlled corresponding to two or more colors in one frame of a screen to be displayed for each pixel, and light is transmitted through the liquid crystal cell. A reflection device disposed at a position where light is incident, and a reflection sheet including two or more reflection regions colored in a color corresponding to the display color of the one frame; and This reflection sheet,
A driving device that drives the two or more reflection areas to sequentially move to a position where the incident light is selectively reflected toward the liquid crystal cell, in synchronization with the control of the color order in the pixels of the liquid crystal cell. The above object is achieved by a reflective color liquid crystal display device having the following features.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a reflective type color liquid crystal display device 10 according to the embodiment of the present invention has one frame of R (red), G (green) and Field-sequential liquid crystal cell 12 whose light transmittance is sequentially controlled corresponding to the three colors B (blue).
So that the light transmitted through the liquid crystal cell 12 is incident
A reflection device 14 disposed on the back of the liquid crystal cell 12,
It is provided with.

The liquid crystal cell 12 performs color display by a field sequential (pixel sequential display) method by the control device 16, that is, color display by a method of mixing colors temporally.

More specifically, R, G, and B are divided into three fields (images), and the fields are sequentially switched at high speed to synthesize one color image.

Therefore, only a single color image is displayed at the moment, but if the repetition rate of the field is fast enough not to be recognized as flicker, the colors are mixed due to the afterimage phenomenon of the retina, and a color image is formed. Be recognized.

R.R. incident from the back of the liquid crystal cell 12
The monochromatic light of G and B is formed by the reflection device 14, and each color light is sequentially reflected and formed in accordance with the switching timing of the liquid crystal cell 12 as an optical shutter.

That is, the reflecting device 14 includes three reflecting regions 18R and 1R so as to form reflected light of three colors of R, G, and B.
8G and 18B, an endless strip-shaped reflective sheet 18 (see FIG. 2), a pair of rolls 20A and 20B for winding and driving the reflective sheet 18, and a motor 20C for driving at least one of the rolls. And a driving device 20 including the following.

The motor 20C is controlled by the control device 16 so that the reflection areas 18R, 18G, and 18B are sequentially positioned on the rear surface of the liquid crystal cell 12 within the range of the field switching speed of the liquid crystal cell 12. Is done. The switching of the field of the liquid crystal cell 12 is performed by the reflection regions 18R, 1R,
It is controlled in synchronization with the 8G / 18B switching speed.

The liquid crystal cell 12 is partially enlarged in FIG.
2A, a transparent common electrode 12B, a black matrix 12C formed between an outer peripheral portion of each pixel of the transparent common electrode and the display-side transparent substrate 12A, and an alignment film 1
2D, a liquid crystal layer 12E, an alignment film 12F on the opposite side sandwiching the liquid crystal layer 12E together with the alignment film 12D, a pixel electrode 12G supporting the alignment film 12F, and a pixel electrode 12G.
A TFT array substrate 12H that supports
12L and optical compensation films 12K and 12J.

The liquid crystal cell 12 is not limited to the structure shown in FIG. 3, but may be constituted by other well-known elements. However, it is different from the conventional color liquid crystal display device in that each pixel displays a plurality of colors without providing a color filter for each color.

The reflection sheet 18 in the reflection device 14
As shown in FIG. 4, a reflective layer 19 and colored layers 19R and 19R are formed on a base material 18A such as a resin film or a metal film.
G, 19B, the reflection regions 18R, 18G, 18
B is formed, and as the base material 18A, a plastic film such as a polyethylene terephthalate (PET) film, a polyester film, a polycarbonate film, a polyacryl film, a polyolefin film, or a thin metal plate such as aluminum or copper is used. Although the thickness of the base material 18A is not particularly limited, it is 10 μm to 5 mm.
Is good.

If the thickness of the base material 18A is less than 10 μm, the abrasion resistance in continuous rotation (movement) is inferior, and if it is more than 5 mm, the rigidity becomes excessive and the rotation is not performed smoothly.

The reflection layer 19 formed on the substrate 18A
Is formed, for example, of a metal with high reflectivity such as aluminum or silver by a physical vapor deposition (PVD) method. The PVD method is appropriately selected from ordinary means for forming a metal thin film such as a vacuum evaporation method, a sputtering method, and an ion plating method. or,
The reflection layer 19 may be formed by laminating a plurality of layers. Here, if the thickness of the reflection layer 19 is about 50 nm to 100 nm, a sufficient reflectance can be obtained.

As shown in FIG. 4, colored layers 19R, 19G and 19B are formed on the reflective layer 19 so as to reflect light of a predetermined color. The specific coloring method is the same as the conventional color filter coloring method, that is, means such as a dyeing method and a dispersion method is used.

In the case where the light reflecting layer is formed by PVD such as a vapor deposition method, to prevent the deterioration of the reflecting layer,
On the reflection layer 19 and the coloring layers 19R, 19G, 19B,
As shown by a two-dot chain line in FIG. 4, for example, acrylic resin, epoxy resin, polyester resin, urethane resin,
It is preferable to provide a protective layer 19C made of a coating film of alkyd resin or the like. This coating may be performed by roll coating, gravure coating, spray coating, or the like.
Further, a thin film of an inorganic substance such as silicon oxide can be used as the protective layer.

The liquid crystal used for the liquid crystal layer 12E of the liquid crystal cell 12 has a response of the liquid crystal of 2 to 2 as described later.
It is necessary to set the speed to 3 ms or less, and it is preferable to use a high-speed switch transistor such as polysilicon for the TFT, and to use an OCB (Optically Compensated Birefringenc).
e) High-speed response liquid crystal such as liquid crystal and ferroelectric liquid crystal is preferable.

In the case of the field sequential display, the field period must be set to 17 ms (1/60 sec) or less in order to prevent the screen from flickering.
Therefore, the display period of each of the reflection areas 18R, 18G, 18B needs to be set to 6 ms or less.

The moving speed of the reflection areas 18R, 18G, 18B is proportional to the size of the entire screen in the liquid crystal cell 12, and is inversely proportional to the length of each reflection area 18R, 18G, 18B in the moving direction. .

The reflection area 18 of the reflection sheet 18
The moving directions of R, 18G, and 18B may be any of the vertical direction, the horizontal direction, and the oblique direction with respect to the liquid crystal cell (screen).

In the reflection type color liquid crystal display device 10 according to the above embodiment, in the reflection device 14, the reflection sheet 18 is moved by the driving device 20 to the reflection area 18.
In synchronization with the rotation of R, 18G and 18B in a predetermined direction at a predetermined speed, the control device 1
6, the pixel becomes a reflection area 18R, 18G, 18
When it is located on any front side of B, control for displaying the corresponding color is performed.

Therefore, the reflection areas 18R, 18G, and 18B sequentially move at intervals of 17 ms or less as described above, and accordingly, the display of R, the display of G,
By sequentially controlling the display of B, light incident from the surface of the liquid crystal cell 12 passes through the liquid crystal cell 12 and is reflected by one of the reflection regions 18R, 18G, and 18B to become colored light, and the liquid crystal is again emitted. Color display is performed sequentially through the cells 12.

On the observer side, the R, G, and B color lights of the same pixel are sequentially displayed in the field period of 1/60 second or less, and the colors are temporally mixed due to the afterimage phenomenon of the retina. It will be recognized as a color image.

In particular, in the reflective type color liquid crystal display device 10 according to the embodiment of the present invention, since a backlight light source for forming monochromatic light is not required, the power consumption is small, and a battery-powered portable device is used. It is suitable for use in electronic equipment and the like.

Next, a reflective color liquid crystal display device 30 according to a second embodiment of the present invention shown in FIG. 5 will be described.

This reflection type color liquid crystal display device (all not shown) has a liquid crystal cell 12 (not shown) similar to the reflection type color liquid crystal display device 10 shown in FIG. 1, and a reflection region different from the above. And a reflection device 34 including a reflection sheet 32.

The reflection sheet 32 includes the reflection area 1
Similar to 8R, 18G, and 18B, light-shielding colored area 33 in addition to reflection areas 32R, 32G, and 32B of three colors of R, G, and B.
Is provided.

The light-shielding colored area 33 is colored black, for example, and its length in the moving direction on the reflection sheet 32 is 50 to 1 of the length of the reflection areas 32R, 32G, and 32B.
It is about 00%.

On the other hand, in the liquid crystal cell 12, the control device 16 performs black display using a period corresponding to the light-shielding colored region 33 as a blanking period.

Therefore, the reflection sheet 32 in the reflection type color liquid crystal display device has reflection regions 32R, 32G, 3R.
By rotating and moving sequentially in the order of 2B and the light-shielding colored area 33, as schematically shown in FIG. 6, for example, the first frame in the moving image display moving rightward in the figure,
In each of the second and third frames, R →
Black display is always performed after displaying three colors, such as G → B → Black → R → G → B → Black.

Thus, so-called color breakup can be prevented. That is, the light-shielding colored region 33 is not provided,
In addition, when the blanking period for black display is not provided on the liquid crystal cell 12 side, as shown in FIG. 7, the last color B of each frame is changed to the next frame when displaying a moving image similar to the above. Is mixed with the first color R due to the afterimage phenomenon in the retina of the observer, and a so-called color breakup phenomenon may occur. In the reflection type color liquid crystal display device according to the example of this embodiment, R , G, and B, there is a black display by the light-shielding colored region 33 after the display of each color.
No color breakup occurs.

The ratio of the length of the light-shielding colored region 33 in the moving direction to the reflection regions 32R, 32G, and 32B is preferably 1/2 to 1. If the length of the light-shielding colored region 33 is larger than 1/2 of the entire reflection sheet 32, the light source utilization rate is reduced to half or less, which is not preferable.
This is because, in the following cases, the aforementioned color breakup occurs.

In the example of the above-described embodiment, the number of reflection areas for forming reflected color light on the reflection sheets 18 and 32 is only one for each of R, G, and B. However, the present invention is not limited thereto. The present invention is not limited to this. As shown in FIG. 8, two or more sets of R, G, B, reflection areas 36R, 36G, 36B and / or these and light-shielding colored areas 37 are set on one reflection sheet 36. May be.

In this case, the speed of the reflection sheet 36 can be reduced in proportion to the set number of the reflection type liquid crystal display device 10 as compared with the reflection type color liquid crystal display device 10.

Further, in the above embodiment, the reflection sheets 18, 32 and 36 are continuously driven by the motor 20C. However, the present invention is not limited to this. As in the case of a film, frame advance may be performed for each color and each light-shielding colored area. In this case, a pulse motor may be used as the motor 20C.

As described above, when the reflection area and / or the light-shading colored area in the reflection sheet are intermittently driven and rotated, the holding time of the area can be obtained, so that the visibility of the screen is dramatically improved. Can be done.

[0043]

Embodiments of the present invention will be described below in detail.

Example 1 First, PET having a thickness of 70 μm
Using a film as a substrate, 60
A sheet (manufactured by Nippon Metalli Co., Ltd.) in which an aluminum layer having a thickness of nm was formed as a reflective layer was obtained. A photosensitive material which exhibits tackiness upon exposure was applied thereon to form a photosensitive layer (thickness: 1.5 μm).

Next, the photosensitive layer was exposed to ultraviolet light via a photomask for a light-shielding portion. An ultra-high pressure mercury lamp was used as a light source for exposure.

Thus, a reflection sheet having reflection regions of three colors of R, G, and B was formed. The width of the reflection sheet was 40 mm, and the length of the colored reflection area was 27 mm.

Next, two small cylinders each consisting of a motor and a rotary support attached to the motor were arranged side by side, and the endless belt-shaped reflection sheet was wound therearound to be rotatable.

The size of the liquid crystal display panel is 30 m.
mx 40mm, 640x48 with VGA display resolution
0 and a TFT whose display mode is OCB-mode
-Adopted LCD. SE7210 (manufactured by Nissan Chemical Industries, Ltd.) was selected as an alignment film material for this LCD, applied to a TFT substrate and its opposite substrate, and subjected to a parallel rubbing treatment.
The gap between the substrates was 6 μm, and optical compensation films were arranged on both sides of the cell.

As the liquid crystal, LIXON manufactured by Chisso Corporation
TD-6004XX was adopted and its display characteristics were measured. The rotation speed of the two cylinders was synchronized with the response time of the liquid crystal by a control device.

As a result, a good color display could be obtained.

(Embodiment 2) The structure is the same as that of Embodiment 1, except that the reflection sheet is provided with the R, G, and B reflection areas, followed by the light-shielding colored areas of the same length as one color reflection area. Was provided.

In the same manner as in the first embodiment, the rotational speed of the cylinder is adjusted to the response time of the liquid crystal, and a black display period corresponding to the light-shielding colored area is provided on the liquid crystal side.
When the display characteristics were measured, so-called color breakup could be observed in the case of a moving image.

(Example 3) A reflection sheet similar to that of Example 2, wherein the total length of the light-shielding colored area is the same as that of the three-color reflection area, that is, に 対 し て of the total length of the reflection sheet, A good color display screen could be obtained without causing color breakup.

Further, in any of Examples 1 to 3,
Since there was no blinking of the light source, there was no change in light intensity at the time of a rising response and a falling response as in the case of using a short afterglow light source such as an LED, and it was possible to obtain an eye-friendly display with high visibility. did it.

[0055]

Since the present invention is constructed as described above, it is possible to obtain a reflection type color liquid crystal display device of a field sequential display system, which can be used for a battery-driven portable electronic device or the like. Has excellent effects.

[Brief description of the drawings]

FIG. 1 is a schematic exploded perspective view showing a reflective color liquid crystal display device according to a first example of an embodiment of the present invention.

FIG. 2 is a developed view showing a reflection sheet in the reflection type color liquid crystal display device.

FIG. 3 is an enlarged cross-sectional view showing one pixel of a liquid crystal cell in the reflective color liquid crystal display device.

FIG. 4 is an enlarged sectional view showing a part of a reflection sheet in the reflection type color liquid crystal display device.

FIG. 5 is a perspective view including a development view showing a reflection sheet in a reflection type color liquid crystal display device according to a second example of an embodiment of the present invention.

FIG. 6 is a schematic diagram showing a color display state of the reflective color liquid crystal display device in a relationship between a horizontal position on a screen and a time axis direction.

FIG. 7 is a schematic diagram similar to FIG. 6 when a light-shielding colored region is not provided on a reflection sheet.

FIG. 8 is a developed view showing a reflection area of a reflection sheet according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Reflection type color liquid crystal display device 12 ... Liquid crystal cell 14,34 ... Reflection device 16 ... Control device 18,32,36 ... Reflection sheet 18R, 18G, 18B, 32R, 32G, 32B, 3
6R, 36G, 36B: Reflecting area 19: Reflecting layer 19R, 19G, 19B: Coloring layer 20A, 20B: Roll 20C: Motor 33, 37 ... Light-shielding colored area

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H048 BB02 BB10 BB42 2H088 EA03 EA20 HA06 HA21 HA28 MA05 2H091 FA01Z FA14Z FA34Z GA11 LA15 LA16 LA17 2H093 NA21 NA65 NA80 NC14 NC43 ND03 ND17 ND39 NE06 NE07 NE10 NG01 AGB5 EE33 FF03 FF05 GG12 GG13 LL07

Claims (5)

[Claims] 1. A field-sequential liquid crystal cell in which light transmittance is sequentially controlled corresponding to two or more colors in one frame of a screen to be displayed for each pixel, and light transmitted through the liquid crystal cell is A reflection device disposed at a position where the light is incident, the reflection device including at least two reflection regions colored in a color corresponding to the color of the one frame, and the reflection sheet. In synchronization with the control of the color order in the pixels of the liquid crystal cell, such that the two or more reflection areas are sequentially moved to positions where the incident light is selectively reflected toward the liquid crystal cell. And a reflection type color liquid crystal display device. 2. The reflection sheet according to claim 1, wherein the reflection sheet has an endless strip shape, and the two or more reflection areas are arranged in a longitudinal direction on a front side thereof, and the driving device winds the endless strip reflection sheet. A reflection type color liquid crystal display device, comprising: a roll to be hung and supported; and a motor to rotate the roll. 3. The liquid crystal cell according to claim 1, wherein the liquid crystal cell is controlled by setting a blanking period in which color display is not performed between frames of a screen to be displayed. At least one set of reflection areas is provided as one set of colors, and a strip-shaped low reflectance area in a direction orthogonal to the sequential movement direction is provided at a rear end or a front end of each set of reflection areas in the sequential movement direction. The reflection type color liquid crystal display device, wherein the low reflectance area is moved in synchronization with a blanking period in the liquid crystal cell. 4. The method according to claim 3, wherein the low reflectance area includes:
A reflective color liquid crystal display device characterized by being colored black. 5. The reflective color liquid crystal according to claim 3, wherein the length of the low reflectance region in the moving direction is 50 to 100% of the length of the pair of reflecting regions in the moving direction. Display device.