JPH10197844A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable one liquid crystal display device to perform both switchings between a reflection type and a transmission type and wide/narrow controls over a field angle. SOLUTION: A PDLC(high polymer dispersion type liquid crystal) cell 4A which can be switched between a state wherein circumferential light is reflected and a sate wherein back light is transmitted by turning ON and OFF a 1st voltage applying means 6 is provided between a liquid crystal element 2 for display and the back light 3, and a guest-host type liquid crystal cell 5 which controls the extent of the filed angle of a liquid crystal element screen for display by turning ON and OFF a 2nd voltage applying means 7 is provided on the opposite side from the PDLC cell 4A when viewed from the liquid crystal element 2 for display, thereby making arbitrary choices on one liquid crystal display device according to use conditions of a case wherein the quantity of circumferential light is large, or small a case wherein plural persons view the display, or a case wherein secrecy needs to be kept.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal used in office automation (OA) equipment such as a word processor or a personal computer, portable information equipment such as an electronic organizer, or a camera-integrated video tape recorder equipped with a liquid crystal monitor. The present invention relates to a display device, and more particularly, to a liquid crystal display device which realizes control of presence / absence of backlight irradiation and width of a viewing angle.

[0002]

2. Description of the Related Art A liquid crystal display device has excellent advantages that a thin display screen can be manufactured and low power consumption, so that it is widely used as a display for the above-mentioned devices. However, unlike a cathode ray tube (CRT) or an EL (electroluminescence) cell, it does not emit light by itself, so that a light source device including a fluorescent tube called a backlight is used for a display liquid crystal element so that it can be used in a dark place. A so-called transmissive type having a structure that is installed behind and illuminated is known as a general type.

However, in the case of such a transmission type liquid crystal display device, usually, 50% or more of the total power consumption is consumed as the power of the backlight. In portable information devices and the like that are frequently used, backlights with large power consumption are difficult to use. In such a case, a reflection plate is installed in the main body of the liquid crystal display instead of the backlight,
A so-called reflection type having a structure in which a display is viewed only by ambient light has been developed. However,
In the case of this reflection type liquid crystal display device, the use condition is that the environment has a necessary amount of ambient light.

Therefore, if a single liquid crystal display device can be switched between a transmission type and a reflection type according to the conditions of use at the time, it is not necessary to see a dark image, and it is not necessary to always turn on the backlight. There is a merit that power consumption can be reduced.

As a prior art of such a liquid crystal display device capable of switching between a transmission type and a reflection type, see, for example, Japanese Patent Application Laid-Open No. Hei 3-1.
No. 19316 (hereinafter referred to as a first prior art example) discloses that an NCAP (Nematic Curvilinear Align) is provided in an apparatus main body.
ed Phase: Nematic curve type alignment phase) A liquid crystal layer is provided,
When the NCAP liquid crystal layer is in a state where no voltage is applied, the NCAP liquid crystal layer is in a light scattering state and blocks the backlight light provided behind the NCAP liquid crystal layer. It is disclosed that the liquid crystal display device can be used for both reflection and transmission because it transmits light.

In recent years, as the applications of liquid crystal display devices have expanded, the required functions have been diversified.
A particularly important function is control of the viewing angle. For example, consider the case of working with a word processor, personal computer, etc. in an aircraft, and in this case, the information displayed on the display of the liquid crystal display device is often confidential, and such confidentiality is high. When there is a display having a sign, it is necessary to pay attention so as not to be seen by others, for example, an unknown passenger in the next seat. In such a case, it is desirable that the display of the liquid crystal display device has directivity that can be visually recognized only by the worker himself, that is, the viewing angle is narrow.

On the other hand, in a place such as a conference where a plurality of people gather, it may be necessary that all the persons present at the place can visually recognize the display of one liquid crystal display device. In such a case, on the contrary, it is desirable that the viewing angle of the display of the liquid crystal display device is as wide as possible.

In order to cope with such applications having a wide viewing angle, separate liquid crystal display devices have been required before, but now a single device can cope with both applications. Liquid crystal display devices have been developed. As a prior art example, for example, Japanese Patent Laid-Open No.
(Referred to as a second prior art example) shows various methods for realizing both a narrow view and a wide view with one liquid crystal display device.

FIG. 5 shows a representative example of the second prior art example. In the liquid crystal display device shown in FIG. 5, an analyzer 51 and a polarizing element are provided outside a display liquid crystal element 50 for display. In addition to the arrangement of the analyzer 52, a guest-host type element 53 serving as a viewing angle adjusting means is attached between the analyzer 51 and the display liquid crystal element 50.
The voltage applying means 55 is connected between the three transparent counter electrodes 54.

[0010] By applying a voltage to the guest-host type element 53 by the voltage applying means 55, the amount of light that can be transmitted through the element 53 is limited, and as a result, the viewing angle becomes narrower than when no voltage is applied. Is configured. In such a configuration, a mode with a wide viewing angle and a mode with a narrow viewing angle can be realized by one liquid crystal display device, and it can be said that the effect of expanding the application and improving the convenience is great.

[0011]

However, the configuration of the first prior art example is useful in that it can be switched between a transmission type and a reflection type. It is not possible to cope with both use conditions of visibility at a wide viewing angle, and the configuration of the second prior art example is excellent in that a wide or narrow viewing angle can be selected. It is not possible to cope with the use conditions of both the visibility function in a dark place and the power saving function that were possible in the prior art example. Thus, in any of the above prior art examples,
A single liquid crystal display device cannot perform both the transmission / reflection switching function and the viewing angle control function.
There was a problem that it could not naturally adapt to all use conditions.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In a liquid crystal display device having a display liquid crystal element and a back light source in an apparatus main body, the back light source is reflected. Reflection / transmission switching means capable of switching between a display state and a transmission state, and a view angle control means for controlling the width of the view angle of the display liquid crystal element screen. Although it is a liquid crystal display device, it is possible to select an optimal usage method according to usage conditions such as ambient brightness and confidentiality of information to be handled.

In the above arrangement, the reflection / transmission switching means is provided between the display liquid crystal element and the back light source, and further, the first voltage applying means generates an electric field for controlling the scattering state and the transmission state of light. With this configuration, it is possible to switch between the reflection type and the transmission type by applying or not applying a voltage. Similarly, by configuring the viewing angle control means to control the width of the viewing angle of the display liquid crystal element screen by the second voltage applying means, the width of the viewing angle can be reduced by applying or not applying a voltage. Switching between the reflection type and the transmission type can be controlled independently.

Further, by configuring at least one of the reflection / transmission switching means and the viewing angle control means so as to be detachable from the apparatus main body, it is possible to achieve more excellent convenience in use. Further, it is desirable that the reflection / transmission switching means be constituted by a polymer dispersed liquid crystal element and the viewing angle control means be constituted by a guest-host type liquid crystal element.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of the present invention. In each of FIGS. 7A and 7B, the upper side of the drawing is the front side, and the lower side is the back side. In FIG. 1A, in a liquid crystal display device provided with a display liquid crystal element 2 provided in an apparatus main body 1 and a backlight 3 as a back light source, ambient light is interposed between the display liquid crystal element 2 and the backlight 3. Reflection / transmission switching means 4 that can switch between a state of reflecting light and a state of transmitting light through the backlight 3 is provided. When viewed from the display liquid crystal element 2, the reflection / transmission switching means 4
On the opposite side, a viewing angle control means 5 for controlling the width of the viewing angle of the display liquid crystal element screen is provided.

The reflection / transmission switching means 4 includes a backlight 3
Is necessarily disposed between the display liquid crystal element 2 and the backlight 3. However, the operation and effect of the viewing angle control means 5 are equivalent. In this case, as shown in FIG. 1 (B), it may be provided on the back side of the display liquid crystal element 2.

In the present invention, the display liquid crystal element 2 is not limited to any of the well-known structures, but here, the TN, which is generally used frequently, is used.
-Type active matrix display liquid crystal element (TN-LC
D).

FIG. 2 shows a first embodiment of the present invention.

The arrangement of the display liquid crystal element 2, the backlight 3, the reflection / transmission switching means 4, and the viewing angle control means 5 in the device main body 1 of the liquid crystal display device shown in FIG. Is the same.

The reflection / transmission switching means 4 can be used as long as it can control scattering and transmission. In this embodiment, a polymer dispersed liquid crystal (Polymer Dispersed Liquid C) is used.
rystal (hereinafter abbreviated as PDLC)) is referred to as cell 4A. On the other hand, the viewing angle control means 5 includes a guest host (Guest host).
Host: GH type liquid crystal cell 5A is used.
These two cells 4A and 5A are provided with first and second voltage applying means 6 and 7, respectively, so that a voltage can be independently applied. Reference numeral 8 denotes a polarizer provided on the forefront of the apparatus body 1, and 9 denotes an analyzer provided between the display liquid crystal element 2 and the PDLC cell 4A.

PDLC cell 4 as reflection / transmission switching means
A description will be given of the action by the voltage applied to A. As shown in FIG. 3, the PDLC layer 10 of the PDLC cell 4A has liquid crystal molecules 12 as fine droplets in the polymer material 11, The refractive index is equal to the refractive index of the liquid crystal molecules 12 in the minor axis direction (ordinary light refractive index). 13 is PD
A transparent electrode provided opposite to both surfaces of the LC layer 9;
An AC voltage is applied between the transparent electrodes 13 from the first voltage applying means 6. 14 is a transparent substrate. FIG.
Is an ON / OFF switch of the first voltage applying means 6.

Returning to FIG. 3, as shown in FIG. 3A, in the structure of the PDLC cell 4A, if the ON / OFF switch 15 of the first voltage applying means 6 is opened to set a voltage non-application state. Since the liquid crystal molecules 12 are randomly aligned,
The light is scattered due to the difference in the refractive index, giving a milky white color, and shows a light-opaque scattering state. Further, as shown in FIG. 3B, the ON / OFF switch 15 of the first voltage applying means 6 is used.
When a predetermined voltage is applied between the transparent electrodes 12 with the liquid crystal molecules closed, the liquid crystal molecules 12 are aligned in the direction of the electric field. Occurs.

According to the properties of this PDLC cell 4A, P
The DLC layer 10 functions as a reflection plate that can switch between reflection and transmission because the incident ambient light is scattered and reflected toward the observer in the scattering state, and the backlight light is transmitted in the transparent state. Therefore, as in the present embodiment, P
When the DLC cell 4A is incorporated, the first voltage applying means 6 can be used when the apparatus main body 1 is installed in a place where ambient light is sufficiently bright.
The ON / OFF switch 15 of the first voltage application means 6 can be used as a reflection type by opening the ON / OFF switch 15 of the first type, and can be used as a transmission type in a dark place by closing the ON / OFF switch 15 of the first voltage applying means 6.

Returning to FIG. 2, GH as a viewing angle control means
In the liquid crystal cell 5A, as shown in FIG. 2A, two transparent substrates 17 are arranged to face each other, a transparent electrode 16 is formed on the side of the transparent substrate 17 facing the other side, and no voltage is applied. A rubbing process is performed on the alignment films formed on the respective transparent electrodes 16 so as to sometimes have a homogeneous alignment. In this GH type liquid crystal cell 5A, a liquid crystal material ZLI-12 is provided.
274 (manufactured by Merck, trade name) is injected to form a viewing angle control cell. Note that this liquid crystal material contains a dichroic dye, 18 is a liquid crystal molecule, and 19 is a dichroic dye molecule.

When the GH type liquid crystal cell 5A serving as a viewing angle control cell is viewed from the front surface of the display liquid crystal element 2, that is, from the display liquid crystal element 2, PDL serving as reflection / transmission switching means is provided.
It was arranged at a position opposite to the C cell 4A. At this time, T
The absorption axis of the polarizer 8 and the absorption axis of the dichroic dye 19 of the display liquid crystal element 2 composed of an N-type liquid crystal cell were aligned. Also, the second
The voltage application means 7 is connected between the opposed transparent electrodes 16, and an ON / OFF switch 20 is interposed in the circuit. Thus, the liquid crystal display device of the present embodiment is manufactured.

Next, the action of the voltage applied to the viewing angle control means will be described.
The voltage applied to the H-type liquid crystal cell 5A is independent of the voltage applied to the PDLC cell 4A. Here, in order to clarify the effect of the voltage applied to the GH type liquid crystal cell 5A,
As shown in FIGS. 2A and 2B, it is assumed that a voltage is applied to the PDLC cell 4A as the reflection / transmission switching means, that is, the liquid crystal display device is used as a transmission type.

As shown in FIG. 2A, when the ON / OFF switch 20 is opened and no voltage is applied to the GH type liquid crystal cell 5A serving as a viewing angle control cell, the display contrast is 1%.
The range of 0: 1 was 52 ° left and right. Next, FIG.
As shown in (B), when the ON / OFF switch 20 was closed and a square wave of ± 10 V was applied by the second voltage applying means 7, the same display contrast range was narrowed to 13 ° left and right. At this time, no deterioration was observed in the display characteristics when the panel surface of the display liquid crystal element 2 was viewed from the front. The same effect was obtained in a state where no voltage was applied, that is, in a state where the liquid crystal display device was used as a reflection type.

FIG. 4 shows a second embodiment of the present invention.

The arrangement of the display liquid crystal element 2, the backlight 3, the reflection / transmission switching means 4, and the viewing angle control means 5 in the device main body 1 of the liquid crystal display device shown in FIG. Is the same. In addition, portions having the same configuration and operation as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the reflection / transmission switching means is constituted by the PDLC cell 4A as in the first embodiment, and another type of GH type liquid crystal cell 5B is used as the viewing angle control means.

GH type liquid crystal cell 5B as viewing angle control means
As shown in FIG. 4A, two transparent substrates 17a are arranged to face each other, a transparent electrode 16a is formed on the opposite surface side of these transparent substrates 17a, and the homeotropic alignment is performed when no voltage is applied. Then, SiO is obliquely vapor-deposited at 97 ° on each transparent electrode 16a, hexadecylamine (C ₁₆ H ₃₃ NH ₂ ) is applied as a vertical alignment material, and dried. A liquid crystal material ZLI-13200 (trade name, manufactured by Merck) is injected into the GH type liquid crystal cell 5B to form a viewing angle control cell. This liquid crystal material contains liquid crystal molecules 18 and dichroic dyes 19.

When the GH type liquid crystal cell 5B serving as a viewing angle control cell is viewed from the front surface of the apparatus body 1, that is, from the display liquid crystal element 2, as in the first embodiment, PDLC serving as reflection / transmission switching means is used. It was arranged at a position opposite to the cell 4A. At this time, the absorption axis of the polarizer 8 and the absorption axis of the dichroic dye 19 of the display liquid crystal element 2 composed of a TN type liquid crystal cell were aligned. Thus, the liquid crystal display device of the present embodiment is manufactured.

Next, the action of the voltage applied to the viewing angle control means will be described.
The voltage applied to the H-type liquid crystal cell 5B is independent of the voltage applied to the PDLC cell 4A. Here, in order to clarify the effect of the voltage applied to the GH type liquid crystal cell 5A,
As shown in FIGS. 4A and 4B, a state where a voltage is applied to the PDLC cell 4A as the reflection / transmission switching means, that is, a state in which the liquid crystal display device is used as a transmission type.

As shown in FIG. 4A, when the ON / OFF switch 20 is opened and no voltage is applied to the GH type liquid crystal cell 5B serving as a viewing angle control cell, the display contrast is 1%.
The range of 0: 1 was 15 ° left and right. Next, FIG.
As shown in (B), when the ON / OFF switch 20 was closed and a square wave of ± 10 V was applied by the second voltage applying means 7, the same display contrast range was widened to 49 ° left and right. At this time, no deterioration was observed in the display characteristics when the panel surface of the display liquid crystal element 2 was viewed from the front. The same effect was obtained in a state where no voltage was applied, that is, in a state where the liquid crystal display device was used as a reflection type.

As the reflection / transmission switching means 4, the PDLC cell 4A has been described in each of the above embodiments. However, the present invention is not limited to this, and is an element capable of controlling the scattering state / transmission state, and has the same effect. For example, NCAP (Nematic Curvilinear Aligned Phase: Nematic Curve Aligned Phase), phase transition type liquid crystal, and the like can be used. In the above embodiments, a GH type liquid crystal cell has been described as the view angle control means 5, but the present invention is not limited to this. For example, a method of controlling a PDLC cell by an applied voltage can obtain the same effect. It is known that is possible.

The reflection / transmission switching means 4 and the viewing angle control means 5 may be configured so as to be detachable from the apparatus main body 1. The reflection / transmission switching means 4 is constituted by, for example, a reflection element sheet (not shown) detachable from the apparatus main body 1 and attached to the apparatus main body 1 only when this reflection element sheet is used in a reflection type. When used in a transmission type, the reflection element sheet may be removed. The viewing angle control means 5 is constituted by a microlens sheet (not shown) that is detachable from the apparatus main body 1 and has a wide viewing angle effect only when used for a wide viewing angle application, for example. When a lens sheet is attached, and the microlens sheet is used for a narrow viewing angle, the microlens sheet may be removed.

[0036]

As described above, according to the first aspect of the present invention, reflection / transmission switching means capable of switching between a state of reflecting ambient light and a state of transmitting through the rear light source,
Since the apparatus main body is provided with a viewing angle control means for controlling the width of the viewing angle of the display liquid crystal element screen, it is possible to switch between reflection / transmission and control the viewing angle in one liquid crystal display device. it can. Therefore, it is possible to select the most appropriate usage method, such as being able to cope with the usage conditions of both the confidentiality of the information to be handled and the visibility at a wide viewing angle, in addition to being able to cope with the amount of ambient light, and to be convenient. Significantly increase.

According to the second and third aspects, the reflection / transmission switching means and the viewing angle control means can be independently controlled by separate voltage applying means, so that they can easily cope with almost all use conditions. Can be. Claim 4
In this case, at least one of the reflection / transmission switching means and the viewing angle control means is configured to be detachable from the apparatus main body. It becomes possible to be excellent.

According to the fifth aspect, the reflection / transmission switching means is constituted by a polymer dispersed type liquid crystal element and the viewing angle control means is constituted by a guest-host type liquid crystal element. In addition, it is possible to obtain excellent characteristics of both the viewing angle control means and the viewing angle control means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIGS. 2A and 2B schematically show the configuration of the first embodiment of the present invention, in which FIG. 2A shows a state when no voltage is applied, and FIG.

FIGS. 3A and 3B schematically show the configuration of a PDLC cell, where FIG. 3A shows a state when no voltage is applied, and FIG. 3B shows a state when a voltage is applied.

FIGS. 4A and 4B schematically show a configuration of a second embodiment of the present invention, wherein FIG. 4A shows a state when no voltage is applied, and FIG.

FIG. 5 is a diagram showing a typical example of viewing angle control in a second prior art example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Device main body 2 Display liquid crystal element 3 Backlight 4 Reflection / transmission switching means 4A PDLC cell 5 Viewing angle control means 5A, 5B GH type liquid crystal cell 6 First voltage applying means 7 Second voltage applying means

Claims (5)

[Claims] In a liquid crystal display device having a display liquid crystal element and a back light source in a device main body, a reflection / reflection switchable between a state of reflecting ambient light and a state of transmitting the back light source.
A liquid crystal display device comprising: transmission switching means; and viewing angle control means for controlling a width of a viewing angle of the display liquid crystal element screen. 2. The reflection / transmission switching means is provided between a display liquid crystal element and a back light source, and is connected to a first voltage applying means for generating an electric field for controlling a light scattering state and a transmission state. The liquid crystal display device according to claim 1, wherein: 3. The liquid crystal display device according to claim 1, wherein the viewing angle control means is connected to a second voltage applying means for generating an electric field for controlling the width of the viewing angle of the display liquid crystal element screen. 4. The liquid crystal display device according to claim 1, wherein at least one of the reflection / transmission switching device and the viewing angle control device is configured to be detachable from the device main body. 5. The reflection / transmission switching means is constituted by a polymer dispersed type liquid crystal element, and the viewing angle control means is constituted by a guest-host type liquid crystal element. 3. The liquid crystal display device according to 1.