JPH0876104A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE: To provide such a liquid crystal display panel that can be used both as a reflection type and transmission type and that in any cases used as a reflection type or transmission type, a sharp image with high luminance image can be obtd. and that modes can be easily switched over to each other. CONSTITUTION: An optical shutter 102 which can reversibly switch the state between a state of high reflectance and low transmittance and a state of high transmittance and low reflectance is disposed between a liquid crystal display cell 101 and a back light unit 103. The state of the optical shutter 102 is switched to one of the two states linked with the control of the back light unit 103 to turn on or off, so that the liquid crystal display panel is used as a reflection type or a transmission type.

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 panel used as a display device for information equipment such as personal computers and word processors.

[0002]

2. Description of the Related Art A display panel using a liquid crystal element is a CR
Compared with other display panels such as T-displays and plasma displays, they have advantages such as thinness and low power consumption, and in recent years, they have been widely used particularly as display panels for information devices such as personal computers and word processors.

Since the liquid crystal element is not a self-luminous element, a light source is required to use it as a display panel, and a reflection type display panel utilizing natural light and a dedicated illumination device on the back surface of the display panel (hereinafter referred to as a backlight unit). Is provided, and two types of transmissive display panels that perform display by the transmitted light from this illumination are used properly.

Although the reflective liquid crystal display panel can perform display with extremely low power consumption, its display quality is limited due to the low screen brightness, and it looks particularly good in an environment where the illumination light is dark. It has the drawback of getting worse.

On the other hand, since the transmissive liquid crystal display panel can always ensure a high display brightness as compared with the reflective liquid crystal display panel, it is possible to obtain good display quality, and the display quality is less influenced by the surrounding environment. However, on the other hand, in the transmissive liquid crystal display panel, a lot of power is consumed to light the backlight unit, so that the battery life is significantly shortened when the information device is driven by the battery. There is.

[0006]

In order to solve these problems, a transflective liquid crystal panel which uses a semi-transmissive reflector and can be used as a transmissive type when the backlight is on and as a reflective type when the backlight is off is commercially available. .

Many inventions relating to a liquid crystal display panel having a mechanism in which a reflecting plate is detachable have been devised, such as Japanese Patent Laid-Open Nos. 2-179611, 4-130490, and 5-188368.

However, in the conventional reflective / transmissive liquid crystal panel using the semi-transmissive reflection plate, the light utilization efficiency becomes low both in the reflective type and in the transmissive type, and only an inconvenient display with low display brightness is obtained. It has the drawback of not having it.

In addition, the liquid crystal display panel with the removable reflection plate requires a lot of time and effort to perform the removal operation each time the mode is switched, and dust and the like easily enter the attachment / detachment portion, which may cause a failure or the like. The current situation is that it has not been put to practical use.

[0010]

In order to solve the above problems, the liquid crystal display panel of the present invention has a first state in which the reflectance is high and the transmittance is low, and a second state in which the transmittance is high and the reflectance is low. In addition, an optical shutter that can be reversibly switched is provided between the liquid crystal display cell and the backlight unit. When the backlight unit is off, the optical shutter is set to the first state and the backlight unit is turned on. In this case, the optical shutter is configured to be in the second state.

[0011]

【Example】

Example 1 The basic structure of the present invention is shown in FIG. The backlight unit 103 is composed of a fluorescent tube, a reflector, a diffuser, a drive circuit, etc., a direct reflection type in which a rear reflector is arranged behind the fluorescent tube and a diffuser is arranged in the front, and the fluorescent tube is arranged at the edge of the display panel. A light guide method of illuminating using a light plate is often used. There are also products that use electroluminescence instead of fluorescent tubes.

The backlight unit 103 has a control signal φmod from the mode changeover switch unit 104.
Control of extinction is performed by e. The mode switching switch unit 104 may be provided with a hardware switch on the exterior of the display panel or the exterior of the information device, or may be a software switch that is switched by software setting in the information device.

The user can turn on / off the backlight unit 103 by operating the mode changeover switch unit 104, and freely select whether the liquid crystal display panel is used as a reflection type or a transmission type. .

In the present liquid crystal display panel, an optical shutter 102 is provided between the liquid crystal display cell 101 and the backlight unit 103, instead of the semi-transmissive plate used in the conventional reflective / transmissive liquid crystal display panel.

The optical shutter 102 has a structure capable of reversibly switching between a state of high reflectance and low transmittance and a state of high transmittance and low reflectance. Further, in order to prevent the area of the entire liquid crystal display panel from being increased by incorporating the optical shutter 102, the optical shutter 10 is not provided in any state.
The occupied area of 2 needs to be almost the same as the area of the liquid crystal display cell 101. Various types of optical shutters having such a structure are conceivable. Specific examples will be described in the second and subsequent embodiments.

The switching of the state of the optical shutter 102 is performed in conjunction with the turning-off control of the backlight unit 103 by the mode switching signal φmode.

When the backlight unit is turned off, that is, when it is used as a reflection type liquid crystal display panel, the optical shutter 102 shifts to a state where the reflectance is high and the transmittance is low and is used as a reflection plate in the reflection type liquid crystal display panel. .

When the backlight unit is turned on, that is, when it is used as a transmissive liquid crystal display panel, the optical shutter 102 shifts to a state where the transmittance is high and the reflectance is low, and the light from the backlight unit 103 is efficiently used. It often emits to the liquid crystal display cell 101 side.

As described above, by changing the state of the optical shutter 102 in association with the turning-on / off control of the backlight unit 103, when a semi-transmissive plate is used both in the reflective type and in the transmissive type. Compared with, it is possible to obtain a clear display with higher screen brightness. In addition, the user can switch between modes with one touch without any troublesome operation.

(Embodiment 2) A liquid crystal cell in which an n-type liquid crystal material having a low resistance value is oriented in a certain direction is transparent in the state where no voltage is applied, but by applying a low frequency drive voltage, a liquid crystal is obtained. It is known that a turbulent flow occurs in the material and the incident light is scattered. A liquid crystal cell having such a mechanism is used for dynamic scattering (Dynamic Sc).
liquid crystal cell.

This dynamic scattering liquid crystal cell can be used as the optical shutter described in the first embodiment. The basic structure of this embodiment is shown in FIG. Normally, when a dynamic scattering liquid crystal cell is used as a display panel, a matrix-like electrode is required, but in the present invention, since it is used as an optical shutter, the flat transparent electrodes 202 and 203 are provided on both sides of the liquid crystal cell 201. .

When the backlight unit 103 is turned on, that is, when it is used as a transmissive liquid crystal display panel, the flat transparent electrodes 202 and 203 are not applied with the drive voltage φdrive and used in a high transmittance state. When the backlight unit 103 is turned off, that is, when it is used as a reflection type liquid crystal display panel, the flat transparent electrodes 202 and 20 are used.
A drive voltage φdrive is applied to 3 and the liquid crystal is used in a dynamic scattering state with a high reflectance.

It is considered that the main purpose of the user to use the reflective / transmissive liquid crystal display panel as the reflective type is to extend the battery life. Therefore, when the reflective type is used, the power consumed by the panel must be small. . In this case, when the reflective type is used, the dynamic scattering liquid crystal cell 201 is used in a driven state, but since it is driven by a plane electrode, it can be driven at a lower frequency than a general display cell and consumes power. Can be kept low.

(Example 3) It is known that when a driving voltage is applied or not applied to a cell in which a liquid crystal layer is dispersed and held in a polymer matrix such as a polymer, a state transition of transmission-scattering occurs. ing. A cell having such a mechanism is called a dispersion type liquid crystal cell. The operation principle of the dispersion type liquid crystal cell will be described with reference to FIGS. 3 (a) and 3 (b).

The cells shown in FIGS. 3 (a) and 3 (b) are set so that the refractive index of the polymer matrix 301 and the ordinary refractive index of the liquid crystal layer 302 are substantially the same. FIG.
In the state in which the drive voltage is not applied as shown in (a), the liquid crystal layer 3
Since the liquid crystal in 02 is in a random state, a difference in refractive index occurs between the liquid crystal and the polymer matrix 301, and the light incident on the cell is scattered. On the other hand, in the driving voltage applied state shown in FIG. 3B, since the liquid crystal in the liquid crystal layer 302 is aligned in the electrolysis direction, the refractive index with the polymer matrix 301 is reduced, and the cell becomes almost transparent.

The dispersion type liquid crystal cell having such a structure is used as the optical shutter described in the first embodiment. The structure of the liquid crystal display panel of the present embodiment is almost the same as the structure of the panel using the dynamic scattering liquid crystal cell described in the second embodiment, except that the states when the driving voltage is applied and not applied are reversed. Therefore, detailed description is omitted.

Example 4 FIG. 4 shows an optical shutter.
A transparent film 401 as shown in is used. The film 401 remains transparent on one side 402 and the other half 40
3 is processed so that it can be used as a reflective film by evaporating a reflective material. The transparent portion 402 and the reflecting portion 403 each have an area equal to or larger than that of the liquid crystal display cell.
The winding margins 404 and 405 are for attaching the film 401 to a shaft described later.

When the liquid crystal display panel is used as a reflection type, the film 401 is moved so that the reflection portion 402 of the film is on the backlight unit and the transparent portion 403 is on the backlight unit. It can act as a shutter. At this time, a place for accommodating the film on the unused side is required, but as described in the first embodiment, it must be avoided that this increases the area of the entire liquid crystal display panel.

The basic structure of the optical shutter in this embodiment is shown in FIG. Guides 50 on both edges of the display panel
1 and 502 and shafts 504 and 5 for film winding that are rotated by motors 506 and 507.
05 is arranged one by one, one of the shafts 503 or 504 is rotated, and the film 505 is wound up, so that the film 505 can be moved in either left or right direction.

The motor drive circuit 508 is driven by the mode switching signal, and control is performed so that the side of the film 505 that is required in each mode of the reflective portion or the transmissive portion is on the backlight unit, and the side that is not required is controlled. The film 505 is the shaft 502 or 503.
Wind up. Thus shafts 503 and 504
Serves both as a drive device for the film 505 and as a storage place for the film 505 on the side not required.

Regarding the winding amount of the film 505 at the time of mode switching, the shafts 503 and
There is also a method of storing the number of revolutions of 04, but more reliable operation becomes possible by providing a mechanical or optical sensor and performing feedback control.

It has been described above that only the shaft 503 or 504 on one side needs to be moved when the film 505 is moved. However, when the slack of the film 505 becomes a problem, the shaft 503 or 504 on the other side is also moved in the opposite direction. The problem can be solved by applying a weak driving force and moving the film 505 while applying tension. It should be noted that the power consumption increases as the reverse driving force increases.

(Embodiment 5) FIG. 6 shows an optical shutter.
Two reflectors 601 and 602 having the same shape as shown in FIGS. 6A and 6B are used. These reflection plates 601 and 602 have an area equal to or larger than that of the liquid crystal display cell, and a plurality of slits are uniformly provided.

The two reflectors 601 and 602 are arranged so as to overlap each other between the backlight unit and the liquid crystal display cell, and the reflector 601 or 602 on either side can be displaced by half the distance between the slits. It has a structure, and this movement is performed by a mode switching signal.

When the backlight unit is turned on, that is, when it is used as a transmissive liquid crystal display panel, FIG.
As shown in FIG.
1 or 602 is moved so that the light from the backlight unit is transmitted to the liquid crystal display cell side.

When the backlight unit is turned off, that is, when it is used as a reflection type liquid crystal display panel, FIG.
As shown in, the reflection plate 601 or 602 is moved to a position where the upper and lower slits alternate so that the incident light does not leak to the backlight unit side, thereby improving the reflection efficiency.

The optical shutter of this system has a maximum aperture ratio of 50% when used in transmission as shown in FIG. 6 (a), so that the display brightness is lower than that of the systems described in the second and third embodiments. There is a risk that As a countermeasure against this, a reflection film is also formed on the back surface of the reflection plate 602 on the backlight unit side, the light of the backlight unit kicked by the reflection plate 602 is returned to the backlight unit side, and is reflected there again to finally form the liquid crystal. It is effective to have a structure that emits light to the display cell side.

[0038]

According to the liquid crystal display panel of the present invention, a clear display screen with high brightness can be obtained both in the reflective type and in the transmissive type, and the mode can be easily switched by the user. It is possible.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a liquid crystal display panel of the present invention.

FIG. 2 is a basic configuration diagram of a liquid crystal display panel according to a second embodiment.

FIG. 3 is a basic configuration diagram of a dispersion type liquid crystal cell, (a) is a configuration diagram in a scattering state, and (b) is a configuration diagram in a transparent state.

FIG. 4 is a diagram of a film used for an optical shutter in Example 4.

FIG. 5 is a basic configuration diagram of an optical shutter according to a fourth embodiment.

6A and 6B are configuration diagrams of an optical shutter according to a fifth embodiment, in which FIG. 6A is a case of using transmission and FIG. 6B is a case of using reflection.

[Explanation of symbols]

 101 liquid crystal display cell 102 optical shutter 103 backlight unit 104 mode changeover switch unit φmode mode changeover signal

Claims (5)

[Claims] 1. A liquid crystal display cell comprising an optical shutter reversibly switchable between a first state having high reflectance and low transmittance and a second state having high transmittance and low reflectance. It is provided between the backlight units, and when the backlight unit is off, the optical shutter is in the first state, and when the backlight unit is on, the optical shutter is in the second state. Liquid crystal display panel. 2. The optical shutter is constituted by a dynamic scattering liquid crystal cell, and the first state and the second state are switched depending on whether a driving voltage is applied or not applied to the liquid crystal cell. The liquid crystal display panel according to claim 1. 3. The optical shutter is constituted by a dispersion type liquid crystal cell, and the second state and the first state are switched depending on whether a driving voltage is applied or not applied to the liquid crystal cell. Item 3. A liquid crystal display panel according to item 1. 4. An optical shutter having an area at least twice as large as that of a liquid crystal display cell, a transparent film having a reflective material vapor-deposited on one half side, and the film wound on both edges of the liquid crystal display panel. A shaft for picking up and a guide, wherein by rotating the shaft to wind up the film, the reflective portion and the transmissive portion of the film are switched to switch between the first state and the second state. Item 3. A liquid crystal display panel according to item 1. 5. The optical shutter comprises two reflecting plates of the same shape in which a plurality of slits are evenly provided, and a means for shifting one of the reflecting plates. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is switched between the second state.