JP2001215509A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device at a low cost which is improved in the use efficiency of light, which gives high visibility regardless of whether illumination is turned on or off, and which is made thin and light-weight with low consumption of electric power. SOLUTION: Fine rugged pattern formed on at least one surface of the substrate on the observer's side of a pair of substrates, which constitute a liquid crystal panel, and a light source, is disposed on or near the side face of the substrate. The substrate on the observer's side, to which a function as a light guide plate is added by the structure has a function to emit the rays through its flat part and to transmit the rays reflected by a reflection layer formed on the lower part of the liquid crystal panel, while hardly dispersing the rays. When illumination is turned off, the substrate has the function of transmitting external light or the rays of the external light reflected by the reflection layer, while hardly dispersing the rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminated reflection type liquid crystal device which is often used indoors and outdoors and is used in portable information equipment such as a portable telephone or a pager using a battery as a main power supply. .

[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, a reflective type that places a reflective layer on the back and illuminates with external light to see the display,
There are transmission type and semi-transmission type with a backlight on the back.
Since the liquid crystal panel can be driven at a low voltage of several volts, the reflection type has a feature of extremely low power consumption, but cannot be used in a dark environment. In addition, since the color liquid crystal panel using the color filter has a low light utilization factor, there is a drawback that bright colors cannot be displayed in the reflection type. 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 measure to solve this problem, a method of attaching a flat illumination (front light) to the display in front of a reflection type liquid crystal panel to share ambient light and front light is disclosed in, for example, JP-A-9-313333. And JP
It has been proposed in Japanese Patent Application Publication No. 0-142601. In FIG.
1 shows a configuration of a conventional reflective liquid crystal device with a front light. As shown in the drawing, the liquid crystal panel 9 has a substrate 29 on which the transparent electrodes 14 are formed, a substrate 30 on which the transparent electrodes 12 and 13 are formed, and a liquid crystal layer 17 provided between these substrates. An upper polarizer 8 is provided on the viewer side of the liquid crystal panel 9, and a lower polarizer 10 and a reflection layer 11 are provided on the opposite side of the liquid crystal panel 9 from the viewer side. The light guide plate 6 is provided on the observer side of the upper polarizer 8.
The light guide plate 6 is made of a transparent plastic, and a light source 7 is disposed on an end surface thereof. The surface of the light guide plate 6 is provided with a shape and an optical member for mainly emitting light from the light source 7 from the lower surface, so that the liquid crystal panel is illuminated from the surface (observer side). The liquid crystal device configured as described above can function as a reflective liquid crystal device using ambient light in a bright environment, and can function as a liquid crystal device with illumination by lighting a front light in a dark environment, thereby achieving both power saving and legibility.

[0004]

A reflection type liquid crystal device using only ambient light has a drawback that it is difficult to color and cannot be used in a dark place. On the other hand, a transmission type or semi-transmission type liquid crystal using a backlight is used. The device has drawbacks of high power consumption and dark display.

[0005] Also, when a front light as shown in FIG. 2 is used, it has been difficult to say that light from a light source is efficiently used. This will be described with reference to FIG. Outgoing lights 15 and 16 from the front light become polarized light by passing through the upper polarizer 8. Thereafter, a voltage non-applying portion (a region sandwiched between the transparent electrode 12 and the transparent electrode 14)
And the voltage application section (the area sandwiched between the transparent electrode 13 and the transparent electrode 14) changes the optical properties in the liquid crystal layer 17, and consequently, the respective lights 18 and 19 passing through the liquid crystal layer 17
Take the directions orthogonal to each other and reach the lower 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 is changed to the lower polarizer 10. , Is reflected by the reflective layer 11, passes through the lower polarizer 10 again, passes through the liquid crystal layer 17 and the upper polarizer 8, and is emitted to the outside. Therefore, the display appearance of the voltage non-applied portion is white (specifically, gray). The above operation is common to all of the above-mentioned liquid crystal layers such as TN type, STN type, vertical alignment type, and ferroelectric type.

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 light is absorbed by the polarizer when passing through the polarizer. That is, first, the upper polarizer 8
As a result, approximately 60% of the incident light 15 is absorbed, and only the remaining 40% of the light reaches the liquid crystal layer 17. Further, each time the light passes through the polarizer, about 5% of the light is absorbed. 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. In addition, the size of the arrow in the figure schematically represents the intensity of light,
,, Indicate the number of transmissions of the polarizer.

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 a problem. Specifically, the present invention improves the light use efficiency,
Regardless of whether the lighting is on or off, the visibility is high,
It is another object of the present invention to provide a thin and lightweight liquid crystal device with low power consumption at low cost.

[0009]

In order to solve the above-mentioned problems, in the liquid crystal device of the present invention, fine unevenness is formed on at least one surface of a substrate on the viewer side among a pair of substrates sandwiching liquid crystal. The light source is provided at or near the side of the substrate. According to such a configuration, a function as a light guide plate can be imparted to the observer side substrate, so that there is no need to separately provide a light guide plate, so that a thin and lightweight liquid crystal device can be obtained.

Furthermore, by forming the irregularities on the surface of the observer-side substrate by corrosion with hydrogen fluoride, when the glass substrate is mainly used as the observer-side substrate, the glass substrate functions as a light guide plate. It is effective as a method of giving.

Further, by forming the irregularities on the surface of the observer-side substrate in a straight groove or a curved groove, the optical path control, which is a function as a light guide plate, can be performed more precisely. According to the liquid crystal device having such a configuration, light use efficiency is improved, and a bright liquid crystal device with low power consumption can be obtained.

Further, the unevenness of the surface of the substrate on the observer side is formed into a mountain shape, the height difference between the peaks and the valleys is set to 5 to 50 μm, and the interval between the peaks of the unevenness is set to 0.05 to 1 mm, so that the optical path control is more precise. The efficiency of light utilization is improved, and a bright liquid crystal device with low power consumption can be obtained.

Further, an upper polarizer is provided on the observer side of the liquid crystal panel (ie, on the observer side with respect to the observer side substrate). According to such a configuration, the number of times light passes through the polarizer before reaching the observer is reduced, the total amount of absorbed light is reduced, and the light use efficiency is improved.

[0014] A polarizer is provided on the inner surface of the liquid crystal panel. According to such a configuration, since a polarizer provided outside the liquid crystal panel is unnecessary, the weight and thickness can be reduced correspondingly.

[0015] Further, a configuration is adopted in which a reflective layer is provided on the inner surface of the liquid crystal panel. According to such a configuration, the weight and thickness corresponding to the reflection layer can be reduced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing a schematic configuration of a liquid crystal device according to the present invention. The liquid crystal panel 2 includes a substrate 25 on which the transparent electrode 22 is formed, and the transparent electrodes 20 and 2.
1 and a liquid crystal layer 27 provided between these substrates. An upper polarizer 1 is provided on the viewer side of the liquid crystal panel 2, and a lower polarizer 4 and a reflective layer 5 are provided on the opposite side of the liquid crystal panel 2 from the viewer side.
Then, fine irregularities 26 are formed on the surface of the observer-side substrate 25, and the light source 3 is arranged near the end of the observer-side substrate 25. As described above, by forming the fine irregularities 26 on at least a part of one surface of the observer-side substrate 25, the observer-side substrate 25 is given a function as a light guide plate. Therefore, the observer-side substrate 25 efficiently guides light from the light source 3 disposed near the end to illuminate the liquid crystal panel. Further, since the observer-side substrate 25 transmits the external light and the light reflected by the reflective layer without being substantially dispersed, the image displayed by the liquid crystal reaches the observer without being distorted or blurred. In the liquid crystal device configured as shown in FIG. 1, when the device is used with illumination in a dark environment, light efficiently guided from the light source 3 is incident on the liquid crystal panel and passes through the liquid crystal layer and the polarizer. Although the observer is made to recognize the display image, the light use efficiency is also improved in this case. This will be described with reference to FIG. The configuration of the liquid crystal device of FIG. 4 is the same as the configuration of the liquid crystal device shown in FIG. Although not shown in FIG. 4, fine irregularities are formed on the surface of the observer-side substrate 25. Light emitted from the light source 3 is guided by the observer-side substrate 25 and enters the liquid crystal layer 27. The liquid crystal layer 27 has a portion where no voltage is applied (the transparent electrode 22).
The optical properties are different between the first electrode and the region sandwiched by the transparent electrode 20) and the voltage applying portion (the second region sandwiched by the transparent electrode 22 and the transparent electrode 21). However, here, unlike the conventional configuration shown in FIG. 3, the light that first enters the liquid crystal layer is not light polarized in a specific direction. And 24 include light in all polarization directions. When these lights pass through the lower polarizer 4, only the light in the polarization axis direction of the lower polarizer 4 is
, Is reflected by the reflective layer 5, passes through the lower polarizer 4 again, and enters the liquid crystal layer 27. Here, the polarization axis of the light incident on one of the voltage non-applied portion and the voltage applied portion changes, and as a result, each of the lights 33 and 34 passing through the voltage non-applied portion and the voltage applied portion of the liquid crystal layer 27 is changed. Each polarization direction takes an azimuth orthogonal to each other and reaches the polarizer 1. Here, if the azimuth of the polarization axis of the upper polarizer 1 matches the polarization direction of the light 33, the light 33 passes through the upper polarizer 1 and is emitted to the outside as shown in FIG. Absorbed by the upper polarizer 1. Therefore, the display appearance of the part where no voltage is applied is white (more specifically, grayish color).
, And the voltage application section has a black display appearance. On the other hand, if the direction of the polarization axis of the upper polarizer 1 matches the polarization direction of the light 34, the upper polarizer 1 will transmit the light 34 and absorb the light 33, and A white display (specifically, a grayish color) is obtained in the application part, and a black display appearance is obtained in the voltage non-application part. As described above, by optimally setting the direction of the polarization axis of the upper polarizer 1, a display image is formed by the voltage non-applying unit and the voltage applying unit. Therefore, in the configuration according to the present invention, light will pass through the polarizer three times before reaching the observer. That is, the amount of light absorption is reduced as compared with the conventional four times described with reference to FIG. 3, and the light use efficiency is improved as compared with the conventional case.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. Referring to FIG. 1, the configuration of a liquid crystal device according to one embodiment of the present invention will be described. As shown in the figure, an upper polarizer 1, a liquid crystal panel 2, a light source 3, a lower polarizer 4, and a reflection layer 5 are provided in this order from the observer side. Fine irregularities 26 are formed on the surface of the observer-side substrate 25 constituting the liquid crystal panel, and the light source 3 is arranged near the end of the observer-side substrate 25. As described above, due to the fine irregularities 26 formed on the observer-side substrate 25, the observer-side substrate 25 functions as a light guide plate and efficiently guides and illuminates light from the light source 3.
Further, since the observer-side substrate 25 transmits the external light and the light reflected by the reflective layer without being dispersed, the image on the display can be seen without being distorted or blurred.

As the pair of substrates constituting the liquid crystal panel 2, 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 light source 3 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 is low in power. LEDs, organic ELs, miniature bulbs, and the like that can be driven by voltage are suitable for applications 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 is obtained. On the other hand, in a bright environment such as outdoors in a sunny day, Provided the same reflective display appearance as the conventional liquid crystal device. The dimensions and weight were reduced by an amount almost equivalent to that of the light guide plate.

In particular, when a glass substrate is used as the observer-side substrate, a method of forming irregularities by making the surface rotten with a hydrogen fluoride solution is simple, efficient, and suitable for cost reduction. In addition, hydrogen fluoride itself may be used as a method for rotting a glass substrate, and a mixture of a fluoride such as calcium fluoride, aluminum fluoride soda, and ammonium fluoride, sulfuric acid, and hydrochloric acid is generated. Hydrogen fluoride may be used. Alternatively, as a method of forming irregularities on the substrate on the observer side, a process of forming a linear groove or a curved groove on the substrate surface may be performed. According to such processing, it is possible to precisely form a groove for forming fine irregularities in a desired shape, and compared to a rotting process using a hydrogen fluoride solution that can only obtain a random irregular surface, Light use efficiency can be increased. Specifically, processing for forming a straight groove or a curved groove on the surface of the substrate can be performed by the following method. In the case where the substrate on the observer side was a glass substrate, a masking agent such as paraffin was applied to a portion not to be rotten, and the surface was rotten with a hydrogen fluoride solution to form a groove having a desired shape. . Also, when the substrate on the observer side is a sheet-like or film-like polymer substrate,
A metal plate in which grooves of a desired shape were previously cut was formed by a hot press method in which a polymer substrate was pressed while being heated.

According to these methods, since the irregularities can be formed in an arbitrary optimum shape, the optical path of the light emitted from the light source can be precisely controlled, compared with the case where random irregularities are formed on the surface. As a result, luminance unevenness can be reduced, light use efficiency can be improved, and a bright liquid crystal device with low power consumption can be obtained.

Further, the formed irregularities (difference in height between peaks and valleys)
Is set to 5 μm to 50 μm, and the pitch (interval between the peaks) is set to a range of 0.05 mm to 1 mm, thereby further improving the light use efficiency. In particular, as shown in FIG. 5, P = 0.2 to 0.4 mm, H = 10 to 2
When formed as 0 μm, α = 40 to 45 degrees, and β = 1 to 5 degrees, a more remarkable effect was obtained.

Also, when a liquid crystal panel of an operation mode that does not require a polarizer (for example, a guest-host type, a light scattering type, etc.) is used, the light use efficiency is greatly improved, and a bright screen is obtained. . Weight, thickness,
It goes without saying that the member costs could be reduced.

Further, when a liquid crystal panel having a polarizer provided on the inner surface is used, the thickness and weight can be reduced because the polarizer is omitted. As a side effect, the readability was improved because the double reflection of the image was eliminated and the efficiency of using light was improved.

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. 6 schematically shows a configuration example of a liquid crystal device according to an embodiment of the present invention. Each configuration will be described in order. First, FIGS. 6A to 6E are configuration examples of a liquid crystal device of a type using two upper and lower polarizers, in which the positions of the upper and lower polarizers and the reflective layer are different. That is, (a) is an example in which the upper polarizer 1 is provided on the inner surface of the liquid crystal panel 2, and the lower polarizer 4 and the reflection layer 5 are provided on the outer surface of the liquid crystal panel 2, and (b) is an example in which the lower polarizer 4 is provided. An example in which the upper polarizer 1 and the reflective layer 5 are provided on the inner surface of the liquid crystal panel 2 on the outer surface of the liquid crystal panel. (D) is an example in which the lower polarizer 4 and the reflective layer 5 are provided on the inner surface of the liquid crystal panel 2, and (d) is an example in which the upper polarizer 1 is provided outside the liquid crystal panel. This is an example in which all of the reflection layers are provided on the inner surface of the liquid crystal panel 2. In each case, a liquid crystal device that is thinner and lighter than the conventional liquid crystal device can be obtained. In particular, in the configurations (b) and (d), in addition to the above-described effects, the number of times light passes through the polarizer is obtained. Has the effect of improving the light use efficiency.

FIGS. 6F and 6G show examples of the structure of a liquid crystal device having a single polarizer, in which the positions of the reflective layers are different. FIG. This is an example in which the reflection layer 5 is provided on the inner surface of the liquid crystal panel 2. (G) is an example in which only the upper polarizer 1 is provided on the inner surface of the liquid crystal panel 2 and the reflective layer 5 is provided on the outer surface of the liquid crystal panel. In a liquid crystal device having such a configuration,
Light use efficiency can be further improved.

(H) to (i) show operation modes that do not require a polarizer (for example, light scattering type, guest host type, etc.).
In the configuration example in the case of using the liquid crystal panel, the installation position of the reflection layer is different. According to the liquid crystal device using the liquid crystal panel in an operation mode that does not require a polarizer, in addition to the same operation and effect as in the above-described embodiment, light absorption 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.
(H) is an example in which the reflection layer 5 is provided on the inner surface of the liquid crystal panel 2, and (i) is an example in which the reflection layer 5 is provided outside the liquid crystal panel. In the figures, hatched portions represent polarizers, and vertical stripe portions represent reflective layers.

In the above-described embodiment of the present invention, a positive type monochrome display liquid crystal device which basically performs black display on a white background has been described. However, a negative type monochrome display liquid crystal device which performs white display on a black background. A similar effect can be obtained with a liquid crystal device for color display, for example, a device using a color filter or birefringence.

[0031]

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, low-cost, low-power-consumption liquid crystal device with high visibility regardless of non-lighting can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a configuration of a liquid crystal device according to 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 illustrating an optical path and a light amount of the liquid crystal device according to the present invention.

FIG. 5 is a schematic diagram showing an uneven shape formed on a viewer-side substrate constituting the liquid crystal device according to the present invention.

FIG. 6 is a cross-sectional view schematically illustrating another configuration example of the liquid crystal device according to the present invention.

[Explanation of symbols]

1, 8 Upper polarizer 2, 9 Liquid crystal panel 3, 7 Light source 4, 10 Lower polarizer 5, 11 Reflective layer 6 Light guide plate 12, 13, 14 Transparent electrode 15, 16 Light emitted from front light 17, 27 Liquid crystal layer 18, 19 Outgoing light from liquid crystal layer 20, 21, 22 Transparent electrode 23, 24 Outgoing light from observer side substrate having light guide plate function 25, 29 Observer side transparent substrate 26 Unevenness 28, 30 Back side substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/30 310 G02F 1/1335 530 F-term (Reference) 2H090 JA02 JA04 JB02 JC03 JC04 JD06 KA05 KA08 KA14 LA09 LA17 LA18 LA20 2H091 FA08X FA08Y FA16Y FA23X FA31X FA42X FA44X FA45X FC14 FD08 GA01 HA07 HA10 HA12 LA03 LA17 LA18 5C094 AA03 AA15 AA22 AA44 AA55 BA03 BA43 CA19 ED11 ED13 ED14 HA08 JA08 5G435 BB07 KK12 BB12 KK

Claims (7)

[Claims] 1. A liquid crystal device having a liquid crystal panel having a liquid crystal sandwiched between a pair of substrates, wherein:
A liquid crystal device, wherein fine irregularities are formed on at least one surface of a viewer-side substrate, and a light source is provided at or near a side of the substrate. 2. The liquid crystal device according to claim 1, wherein the irregularities on the surface of the observer-side substrate are formed by hydrogen fluoride. 3. The liquid crystal device according to claim 1, wherein the unevenness on the surface of the observer-side substrate has a shape of a straight groove or a curved groove. 4. The height difference between the peaks and valleys of the unevenness is 5 to 50.
μm, the distance between the tops of the irregularities is 0.05 to 1 mm
The liquid crystal device according to claim 3, wherein: 5. The liquid crystal device according to claim 1, wherein a polarizer is provided on a viewer side of the liquid crystal panel. 6. The liquid crystal device according to claim 1, wherein a polarizer is provided on an inner surface of the liquid crystal panel. 7. The liquid crystal device according to claim 1, wherein a reflection layer is provided on an inner surface of the liquid crystal panel.