JP2000098362A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization efficiency of light notwithstanding having a thin structured, light in weight and low in power consuming and make obtainable a high visibility irrespective of turning on/off of illumination by providing at least one substrate, being transparent, of a liquid crystal panel sandwiching a liquid crystal between a pair of substrates with a function of a light guiding plate simultaneously. SOLUTION: One substrate of a liquid crystal panel 2 is transparent and is simultaneously provided with a function of a light guiding plate. For this substrate an inorganic transparent material such as glass, a polymer material such as a sheet or a combined material of them is used. The function of the light guiding plate 2 is formed by injection molding, with a thermosetting resin, with photosetting resin, by etching, with transparent resin or by joining a film to, or by providing a resin layer on, a flat glass plate. This substrate functions as a light guiding plate which efficiently guides light from a light source 3 for illumination, in addition to its basic function to hold liquid crystal. Furthermore, as it transmits external light and light reflected with a reflection layer 5 with hardly any dispersion, a display picture can be viewed without distortion or blurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminated reflective liquid crystal device which is often used indoors and outdoors and is used for portable information equipment such as a cellular phone and a pager using a battery as a main power source.

[0002]

2. Description of the Related Art Liquid crystal devices are widely used as portable information terminal displays because of their thin and light characteristics. The liquid crystal panel is a light-receiving element that does not emit light by itself, and is classified into a reflection type in which a reflective layer is provided on the back surface to illuminate the display with external light to view a display, a transmission type in which a backlight is provided on the back surface, and a transflective type. Since the liquid crystal panel can be driven with a low voltage of several volts, the reflective type has the feature of extremely low power consumption,
It cannot be used in a dark environment, and a color liquid crystal panel using a color filter has a low light utilization factor. As illumination of a reflective liquid crystal panel, a bean ball lamp is placed diagonally forward of a panel in a wristwatch or the like and used as nighttime illumination, but is limited to a small liquid crystal panel because of lack of uniformity.

As a solution to this problem, a method has been proposed in which a flat illumination (front light) is provided on the display in front of a reflection type liquid crystal panel so that ambient light and front light can be shared (for example, Japanese Patent Application Laid-Open No. 9-1997). -31333 and JP-A-10-142601). FIG. 2 shows a configuration diagram of a conventional reflection type liquid crystal device with a front light. 6 in the figure
Is a light guide plate made of a transparent plastic, and 7 is a light source provided on an end face of the light guide plate 6. On the surface of the plastic light guide plate 6, a shape and an optical member for emitting light from the light source 7 mainly from the lower surface are provided, and the liquid crystal panel is illuminated from the surface. The liquid crystal device configured as above functions as a reflective liquid crystal device using ambient light in a bright environment and functions as an illuminated liquid crystal device with a front light turned on in a dark environment, thereby achieving both power saving and legibility. .

[0004]

In the case of a reflection type liquid crystal device using only ambient light, there is a drawback that colorization is difficult and it cannot be used in a dark place, and a transmission type or semi-transmission type liquid crystal device using a backlight is disadvantageous. , Power consumption is large,
There was a drawback that the display was dark. Also, when a front light as shown in FIG. 2 was used, it was difficult to say that the light from the light source was efficiently used.

A description will be given with reference to FIG. Outgoing lights 15 and 16 from the front light become polarized light by passing through the upper polarizer 8. Thereafter, the voltage-free portion (the region sandwiched between the transparent electrode 12 and the transparent electrode 14) and the voltage application portion (the region sandwiched between the transparent electrode 13 and the transparent electrode 14) form the optical As a result, the polarization axes of the lights 18 and 19 that have passed through the liquid crystal layer 17 take the directions orthogonal to each other and reach the polarizer 10. Here, if the direction of the polarization axis of the lower polarizer 10 is optimally set, as shown in FIG. 3, the incident light 19 is absorbed by the lower polarizer 10 to give a black display appearance, and the incident light 18 becomes the lower polarized light. The lower polarizer 1 transmits through the polarizer 10 and is reflected by the reflection layer 11 again.
0, and is emitted outside through the liquid crystal layer 17 and the upper polarizer 8. Therefore, the display appearance of the voltage non-applied portion is white (specifically, gray). The above operation is performed when the liquid crystal layer is TN
, STN type, vertical alignment type, ferroelectric type, and the like.

Here, an important problem for a liquid crystal device using a battery as a main power source is how to efficiently operate the liquid crystal device.
This is how to achieve a bright and easy-to-see display appearance. In the conventional liquid crystal device, the black display portion expresses substantially sufficient black, but the white display portion is dark and the display is difficult to see. The main reason why such favorable brightness cannot be obtained is that almost 60% of the incident light 15 is generated by the upper polarizer 8.
% Of light is absorbed and only the remaining 40% of the light reaches the liquid crystal layer 17, and about 5% of the light is absorbed each time the light passes through the polarizer. That is, in the liquid crystal device having such a configuration, the light passes through the polarizer a total of four times, greatly reducing the light use efficiency. The size of the arrow in the figure is
This is a schematic representation of the light intensity.
The number of times of transmission of the polarizer is shown.

In a liquid crystal device used for a portable device, characteristics such as light weight, thinness, and compactness are also very important. However, the liquid crystal device having the above-described backlight or front light illumination has a configuration in which the light guide plate and the light emitting element itself are stacked on the liquid crystal panel, and therefore has to be heavy, thick, and large. The present invention has been made in order to solve such problems. Specifically, the present invention has improved light use efficiency, has high visibility regardless of lighting / non-lighting, and is thin and lightweight. It is intended to provide a low-power liquid crystal device at low cost.

[0008]

According to a first aspect of the present invention, there is provided a liquid crystal device in which at least one substrate of a liquid crystal panel in which liquid crystal is sandwiched between a pair of substrates is transparent, and has a function of a light guide plate. It was made. According to the liquid crystal device of the first aspect, since a light guide plate is unnecessary, a thin and lightweight liquid crystal device can be obtained, and the number of times of emitted light passing through the polarizer is reduced, so that the light use efficiency is increased. . FIG. 4 is a schematic diagram showing this state. Further, since the substrate serving as the light guide plate is transparent, the image on the display can be seen without distortion or blurring.

According to a second aspect of the present invention, in the first aspect, the substrate has a function of mainly emitting light from a light source from one of the surfaces of the substrate. According to the liquid crystal device according to the second aspect, light contributing to illumination increases, and a liquid crystal device with a bright display screen can be obtained. Claim 3
In the liquid crystal device described in claim 1 or claim 2,
The liquid crystal panel uses an operation mode that does not require a polarizer. According to the liquid crystal device of the third aspect, in addition to the function of the first or second aspect, the absorption of light by the polarizer is eliminated, so that the light use efficiency is further improved.
In addition, since a polarizer is unnecessary, the weight, thickness, and cost can be reduced.

A liquid crystal device according to a fourth aspect is the liquid crystal device according to the first or second aspect, wherein a polarizer is provided on an inner surface of the liquid crystal panel. According to the liquid crystal device of the fourth aspect, in addition to the operation of the first or second aspect, since a polarizer provided outside the liquid crystal panel is unnecessary, a corresponding weight and thickness can be reduced. The liquid crystal device according to claim 5 is
Claim 1 or Claim 2 or Claim 3 or Claim 4
, A reflective layer is provided on the inner surface of the liquid crystal panel. According to the liquid crystal device of the fifth aspect, in addition to the effect of the first, second, third, or fourth aspect, the weight and thickness corresponding to the reflection layer can be reduced.

According to a sixth aspect of the present invention, there is provided the liquid crystal device according to the first, second, third, fourth, or fifth aspect, wherein a light source for liquid crystal illumination is directly mounted on the substrate. According to the liquid crystal device of the sixth aspect, in addition to the effects of the first, second, third, fourth, or fifth aspects, the weight and size can be reduced by simplifying the members for holding the light source and the wiring. Can be reduced.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a schematic vertical sectional view of a liquid crystal device according to an embodiment of the present invention. In order from the top, an upper polarizer 1, a liquid crystal panel 2, a light source 3, a lower polarizer 4, and a reflective layer 5 are provided. As the substrate, an inorganic transparent material such as glass, a polymer material in the form of a sheet or film, or a composite thereof is used. The function as the light guide plate is formed by a method such as injection molding, thermosetting resin, photocurable resin, etching, bonding a film on a transparent resin or a glass plate, or providing a resin layer. The substrate thus formed functions as a light guide plate for efficiently guiding and illuminating light from a light source, in addition to the basic function of holding liquid crystal. Further, since the external light and the light reflected by the reflective layer are transmitted with almost no dispersion, the image on the display can be seen without being distorted or blurred. Note that the material and the formation method of the substrate are not limited to the above-described methods as long as they have a function related to the present invention.

The light source to be used may be any light source such as a fluorescent tube, a light emitting diode (LED), an electroluminescence (EL), a miniature light bulb, etc., but does not require a special mechanism such as an inverter circuit and has a low voltage. An LED, an organic EL, a miniature bulb, and the like, which can be driven by a microcomputer, are suitable for use with low power consumption. In the liquid crystal device configured as described above, the illumination light of the light source can be efficiently used in a dark environment, so that a brighter and easier-to-see display appearance can be obtained. Almost the same reflective display appearance as that of the liquid crystal device was obtained. The dimensions and weight were reduced by an amount almost equivalent to that of the light guide plate.

Further, in the liquid crystal device configured as shown in FIG. 1, when a substrate for mainly emitting light of the light source prepared by the above-described method from the lower surface of the substrate is used, light contributing to illumination is clearly The screen brightness was improved by about 10% as compared with the conventional liquid crystal device with a front light, which increased and became a brighter and more legible liquid crystal device. If the screen luminance is almost the same, the light source luminance can be reduced, so that power consumption can be reduced.

When an operation mode (for example, guest-host type, light scattering type, etc.) liquid crystal panel which does not require a polarizer is used, light use efficiency is greatly improved, and a bright screen is obtained. It goes without saying that the weight, thickness, and member cost can be reduced by eliminating the polarizer. When a liquid crystal panel provided with a polarizer on the inner surface was used, the thickness and weight could be reduced because the polarizer was omitted. As a side effect,
Since the double reflection of the image was eliminated, the readability was improved in combination with the improvement of the light use efficiency.

When a liquid crystal panel provided with a reflective layer on the inner surface was used, the thickness and weight could be reduced because the reflective layer was omitted. In the case of the liquid crystal panel of the mode using the polarizer,
Since at least the lower polarizer needs to be provided on the inner surface, the thickness and weight are reduced accordingly. FIG. 5 schematically shows a configuration example of the liquid crystal device according to the embodiment of the present invention.

When the light source of the liquid crystal lighting is directly mounted,
The weight and size can be reduced by simplifying the members for holding the light source, the wiring, and the like. Although the present embodiment describes a monochrome liquid crystal device, a similar effect can be obtained with a color display liquid crystal device, for example, a device using a color filter or birefringence.

[0018]

As described above, according to the present invention, since the light use efficiency can be improved, the lighting of the lighting can be improved.
A low-cost, thin, light-weight, low-power-consumption liquid crystal device can be obtained with high visibility irrespective of non-lighting, reduction of members, and installation of the inner surface.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a liquid crystal device according to an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a conventional liquid crystal device with a front light.

FIG. 3 is a schematic diagram of an optical path and a light amount in a conventional liquid crystal device with a front light.

FIG. 4 is a schematic diagram of an optical path and a light amount of a liquid crystal device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a configuration example of a liquid crystal device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper polarizer 2 Liquid crystal panel 3 Light source 4 Lower polarizer 5 Reflective layer 6 Light guide plate 7 Light source 8 Upper polarizer 9 Liquid crystal panel 10 Lower polarizer 11 Reflective layer 12 Transparent electrode 13 Transparent electrode 14 Transparent electrode 15 Output from front light Emitting light 16 Outgoing light from front light 17 Liquid crystal layer 18 Outgoing light from liquid crystal layer 19 Outgoing light from liquid crystal layer 20 Transparent electrode 21 Transparent electrode 22 Transparent electrode 23 Outgoing light from substrate having light guide plate function 24 Light guide plate function Outgoing light from the substrate

Claims (6)

[Claims] 1. A liquid crystal device comprising a liquid crystal illumination and a liquid crystal panel having a liquid crystal sandwiched between a pair of substrates, wherein at least one of the substrates is transparent and has a function of a light guide plate. A liquid crystal device characterized by the above-mentioned. 2. The liquid crystal device according to claim 1, wherein the substrate has a function of mainly emitting light from a light source from one of the surfaces of the substrate. 3. The liquid crystal device according to claim 1, wherein the liquid crystal panel uses an operation mode that does not require a polarizer. 4. The liquid crystal device according to claim 1, wherein a polarizer is provided on an inner surface of the liquid crystal panel. 5. The liquid crystal device according to claim 1, wherein a reflection layer is provided on an inner surface of the liquid crystal panel. 6. The liquid crystal device according to claim 1, wherein a light source for illumination is directly mounted on an end portion of the substrate.