JPH11237626A - Display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make contrast satisfactory, to eliminate hysteresis and further to provide high reliability by forming a reflection bored on the surface of one of a pair of substrates opposite to the side of a liquid crystal. SOLUTION: Transparent electrodes ITO 2 and 5 are formed on glass substrates 1 and 6, and between these substrates, the mixture of a liquid crystal and an organic thermoplastic polymer is held. In this case, the liquid crystal in 30 to 90% is mixed with the organic thermoplastic polymer, heated to about 180 deg.C and made uniformly compatible. Outside an element part prepared like this, a reflection board 7 is arranged while being inclined at about 3 deg. in respect to the surface of the element part. It is necessary to arrange the reflection board 7 close to the element part as much as possible. If not, the same light can not be modulated by the same pixel. To realize this modulation, it is necessary to minimize the angle of inclination of the reflection board to prevent reflected light on the surface of the element part from being made incident on a photodetecting part. In this example, the contrast of the display element is about 20:1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a display device in which a liquid crystal is fixed by a carrier.

[0002]

2. Description of the Related Art A conventional display device having a liquid crystal fixed on a carrier is disclosed in U.S. Pat. Nos. 4,728,547 and 4,688,9.
The ultraviolet-curable or thermosetting organic polymer was used for the carrier for supporting the liquid crystal. However, since the carrier monomer is cured by a chemical reaction after being mixed with the liquid crystal, the carrier monomer reacts with the liquid crystal, or the liquid crystal is decomposed, resulting in poor reliability. (Named as hysteresis characteristics). In order to solve this, a method using a thermoplastic polymer as a carrier polymer has been studied.

[0003]

However, when a thermoplastic polymer is used, there is a problem that the contrast cannot be obtained because the light quantity (OFF light quantity) when the electric field is cut off is large. In view of the above, an object of the present invention is to provide a display element having good contrast, no hysteresis characteristics, and high reliability by using a thermoplastic polymer for a carrier and using a reflection mode. .

[0004]

According to the present invention, there is provided a display element having a liquid crystal layer sandwiched between a pair of substrates, wherein the liquid crystal layer is provided on one side of the pair of substrates opposite to the liquid crystal layer side. A reflector is formed on the surface, and the surface of the reflector on the liquid crystal layer side is formed in a saw-tooth shape.

[0005]

According to the above configuration of the present invention, since light passes through the element twice, a square curve of electro-optical characteristics measured in the transmission mode can be obtained. Therefore, the threshold characteristics become steep. At this time, the reflected light from the element surface can be removed by disposing the reflector at an angle to the surface of the element portion. In addition, when a thermoplastic polymer is used, there is almost no hysteresis characteristic particularly when a cellulose derivative is used. Therefore, a display element having good electro-optical characteristics can be manufactured. In addition, since a highly polymerized polymer can be used, impurities that react with liquid crystal molecules can be reduced as much as possible.In addition, since the carrier is not formed by polymerization, the liquid crystal is irradiated without being irradiated with ultraviolet rays. Very little damage. Therefore, reliability is improved.

Hereinafter, the present invention will be described in detail with reference to examples.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

[0008]

Embodiment 1 FIG. 1 is a sectional view of a display device showing an embodiment of the present invention. FIG. 2 is an overall view of a display device including the display element of the present invention. A transparent electrode ITO2 and a transparent electrode ITO5 were formed on the substrate 1 and the substrate 6, and a mixture of a liquid crystal and an organic thermoplastic polymer was sandwiched between these substrates. The preparation of liquid crystal and polymer and the method of fabricating the element will be described. Table 1 shows the thermoplastic polymers used in this example and the liquid crystals combined therewith. First, 30 to 90% of a liquid crystal is mixed with the above-mentioned polymer, and the mixture is heated to about 180 ° C. so as to be uniformly compatible. The mixture was developed on a substrate with electrodes in a state of being dissolved, and sandwiched between opposed substrates with electrodes so as to prevent phase separation. The thickness of the liquid crystal layer was 10 μm, but is not limited to this.
If the thickness is increased, the contrast as a display element can be improved, but there is a problem that the driving voltage is increased. The reflection plate 7 was disposed outside the element portion thus formed at an angle of 3 degrees with respect to the surface of the element portion. The reflection plate 7 needs to be arranged as close as possible to the element portion, otherwise the same light cannot be modulated by the same pixel. In order to realize this, it is necessary to minimize the angle at which the reflection plate 7 is inclined so that the reflected light from the surface of the element unit does not enter the light receiving unit. FIG. 3 shows the electro-optical characteristics of the display element of this example. The contrast is about 20: 1. In this embodiment, the driving voltage is 40 V (the driving frequency is such a frequency that an electric field is sufficiently applied to the element, here, 1 KH
z). Similar display states could be obtained using any polymer. There was almost no change over time in the electro-optical properties after one month. The liquid crystal used here is selected according to the refractive index of the polymer, and other liquid crystals can be used even if the refractive index does not match a little. Further, the polymer itself is not limited to those shown here as long as it is a thermoplastic polymer. The ratio of liquid crystal to polymer is 30
%, A sufficient optical change cannot be obtained, and if it is 90% or more, sufficient light scattering cannot be obtained.

[0009]

[Table 1]

In the liquid crystal shown in the table, ZLI- is manufactured by Merck, and RDP- is manufactured by Roddick.

[0011]

Embodiment 2 This embodiment shows an example in which a reflector having a sawtooth cross section is used as a reflector. FIG. 4 is a cross-sectional view of the device according to the present embodiment. The difference from the first embodiment lies in the structure and arrangement of the reflector disposed outside the element section. The structure of the reflector will be described. As shown in FIG. 2, sawtooth-shaped irregularities having a pitch of 50 μm and a surface angle of 5 degrees were formed on the glass substrate 14. A polymer substrate may be used instead of a glass substrate. Aluminum was formed thereon as a reflective film 8 to a thickness of 3000 angstroms. This was placed in close contact with the surface of the element section. By using this reflection plate, a uniform 2
Double modulation can be performed.

[0012]

Embodiment 3 In this embodiment, a case is shown in which one electrode is used as a metal electrode 13 and also serves as a reflector having a saw-tooth reflection surface. FIG. 5 shows a cross-sectional view of the device of this example. The polymer and liquid crystal used were the same as in Example 1. The reflecting plate used in Example 2 was used as one substrate, and a flat substrate with a transparent electrode was used on the other side, and the polymer / liquid crystal mixture which had been made compatible therebetween was sandwiched in a state of being compatible and cooled rapidly. The electro-optical characteristics and reliability in this embodiment were the same as those in the first embodiment. According to this embodiment, since no reflector is required, a compact and inexpensive reflective display element can be manufactured.

[0013]

FIG. 6 is a sectional view of a conventional polymer-dispersed liquid crystal display device. The manufacturing method of the element excluding the reflection plate is the same as that of the first embodiment. The electro-optical characteristics of the device thus manufactured in the transmission mode were measured (see FIG. 7). It can be seen that the OFF light amount is considerably large and no contrast is obtained.

Although the embodiments and the conventional examples have been described above, the present invention can be widely applied not only to the above embodiments but also to display elements, reflection type displays, projectors and the like.

[0015]

As described above, according to the present invention, a display element having good contrast, no hysteresis characteristics and high reliability can be obtained by using a thermoplastic polymer as a carrier and using a reflection mode. It became possible to provide.

[Brief description of the drawings]

FIG. 1 is a sectional view of a display element according to a first embodiment of the present invention.

FIG. 2 is an overall view of an apparatus including a display element according to the first embodiment of the present invention.

FIG. 3 is an electro-optical characteristic diagram of the display element in Example 1 of the present invention.

FIG. 4 is a cross-sectional view of a display element according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a display element according to Example 3 of the present invention.

FIG. 6 is a cross-sectional view of a conventional polymer-dispersed liquid crystal display device.

FIG. 7 is an electro-optical characteristic diagram of a conventional polymer-dispersed liquid crystal display device.

[Explanation of symbols]

 1. ... Glass substrate ... ITO transparent electrode ... Liquid crystal 4. ... Polymer 5. ... ITO transparent electrode ... glass substrate 7. ... Reflector 8 ... reflection film ... incident light 10. ... reflected light 11. ... Condensing lens ... screen 13. ... metal electrodes 14. ... Sawtooth shaped glass substrate

Claims (1)

[Claims] 1. A display element comprising a liquid crystal layer sandwiched between a pair of substrates, wherein a reflection plate is formed on a surface of one of the pair of substrates opposite to the liquid crystal layer side, and A display element, wherein a surface of the reflection plate on the liquid crystal layer side is formed in a sawtooth shape.