JPH0437825A - Liquid crystal electro-optical device - Google Patents

Abstract

PURPOSE:To offer a highly efficient liquid crystal electro-optical device by means of an inexpensive and simple process by combining a non-linear element formed by holding a non-linear electroconductive organic layer containing at least an organic substance as a component between electrodes and a liquid crystal electro-optical element formed by holding a substance containing a liquid crystal composition between picture element electrodes. CONSTITUTION:Pyrex(R) glass whose surface is optically polished is used as a base 101, a conductive film consisting of a metal or the like is formed on the base 101 to pattern a lower electrode 102, a material solution obtained by mixing a certain material having a charge transporting function in a solution and uniformly agitating the solution by ultrasonic waves is applied to a polymer insulating substance and dried to form a non-linear electroconductive induced layer 103, a conductive layer is formed by a metal or the like and patterned as an upper electrode 104 to form a non-linear element. Then, a picture element electrode 105 and a liquid crystal oriented layer 106 are formed so as to be connected to the non-linear element to form an element base. A counter base is obtained by forming stripe-like counter electrodes 108 and a liquid crystal oriented layer 109 on an optical figured base 107. The counter base and the element base are opposed to each other through a proper interval and a liquid crystal component 110 is stored in a gap formed between both the bases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal electro-optical device comprising a combination of a non-linear element having non-linear current-voltage characteristics and a liquid crystal electro-optical element. In particular, it relates to the structure of a liquid crystal electro-optical device.

[Problems to be Solved by the Invention] However, in such liquid crystal electro-optical devices, it is essential to use highly controlled vacuum equipment such as CVD or sputtering to form nonlinear elements, and substrate preparation etc. is necessary. Moreover, expensive processes are required to create the nonlinear elements, making it difficult to create low-cost liquid crystal electro-optical devices. Also, since the controllability of nonlinear elements is not very good,
This led to the occurrence of defects and a decline in long-term reliability.

Therefore, the present invention aims to solve the above problems by providing a liquid crystal electro-optical device using a nonlinear element and a liquid crystal electro-optic element that can be formed by a simple manufacturing method.

[Prior Art] [Means for Solving the Problems] A liquid crystal electro-optical device of the present invention includes at least a nonlinear element having a nonlinear electrical conduction inducing layer containing an organic substance as a component sandwiched between electrodes, and a liquid crystal composition. A liquid crystal electro-optical element is formed by sandwiching a substance containing a substance between pixel electrodes.

[Example] Hereinafter, the details of the present invention will be shown by examples.

(Example 1) Figure 1 schematically shows a liquid crystal electro-optical device prototyped in this example. Pyrex glass with an optically polished surface is used as the base 101, and a conductive film such as metal is formed by sputtering or vapor deposition. Then, a pattern was formed by photoetching to form the lower electrode 102, and a nonlinear electrically conductive layer was formed on this.

The polymeric insulator used for the nonlinear electrical conduction inducing layer is diisopropyl polyfumarate (hereinafter abbreviated as PDiPF).When used alone, polyfumarate esters such as PDiPF have a thickness of up to several hundred angstroms. It is known as a material that can yield thin films with excellent electrical insulation properties even with extremely thin spin cord films.
(Katagata et al., Polymer Symposium Proceedings Vol. 1.39. No. 8
(1989) p. 2561) After PDiPF is purified by reprecipitation, it is dissolved in purified chloroform and PDiPF is purified by reprecipitation.
A DiPF solution was made. This solution was passed through a 0.5 μm filter to remove dust.

A material with charge transport ability such as 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole is mixed with this polymer insulator in solution, and the solution is stirred using ultrasound. It was made uniform and used as a raw material liquid. The mixing ratio is determined by the balance between the ON current value and/or OFF current value of the target nonlinear element and the film strength, but if the film thickness and element size are appropriately selected, it can be mixed in the range of 0.001 to 30 wt%. It was confirmed that both showed nonlinearity in current-voltage characteristics.

After coating this raw material solution, it is dried to form a nonlinear electrical conduction inducing layer 1.
03, a conductive layer made of metal or the like was formed and patterned to form an upper electrode 104 to obtain a nonlinear element. A pixel electrode 105 was formed so as to be connected to this nonlinear element, and a liquid crystal alignment layer 106 was formed to obtain an element substrate. At this time, if the bias in the electrical characteristics depending on the positive and negative voltages applied to the nonlinear element is sufficiently small, it is also possible to omit the upper electrode and form the nonlinear element by a part of the pixel electrode and the lower electrode.

In the nonlinear element substrate configured as described in this example, the lower electrode used for long wiring can be directly formed on the base.
Easy to form low resistance wiring. The element structure of the nonlinear element created in this example will be abbreviated as HIM structure in the following specification.

The counter substrate used was one in which a striped counter electrode 108 was formed on an optically polished base 107 and a liquid crystal alignment layer 109 was formed thereon.

The counter substrate and element substrate thus obtained were placed opposite to each other at an appropriate interval, and the liquid crystal composition 110 was held between the gaps formed by them, thereby producing a liquid crystal electro-optical device.

While applying a driving voltage to the liquid crystal electro-optical device created as described above, light that has passed through a polarizer is made incident, and the emitted light is detected after passing through an analyzer to determine the electro-optic characteristics. evaluated. This evaluation shows that by combining a nonlinear element and a liquid crystal electro-optic element, it is possible to achieve both a wide viewing angle and good contrast during time-division driving with a large division ratio, which is not possible with a liquid crystal electro-optic element alone. It was confirmed. In addition, for the formation of electrodes,
It was confirmed that the characteristics were not affected even if low-cost methods such as vapor deposition, EB vapor deposition, and electroless plating were used. Therefore, according to the present invention, it is possible to create a high-performance liquid crystal electro-optical device without using CVD or sputtering. Furthermore, we confirmed that it is possible to create a liquid crystal electro-optical device without a vacuum device by using an electrode that can be formed at room temperature and pressure, such as an organic conductor.

(Comparative Example) This comparative example shows an example in which a conventional liquid crystal electro-optical device was fabricated using a tantalum oxide insulating film formed by anodization as a nonlinear electrical conduction inducing layer.

FIG. 2 shows the configuration of a liquid crystal electro-optical device in this comparative example.

After forming a tantalum oxide layer 202 as an electrode base on a base 201, a metal tantalum as a lower electrode is formed by sputtering, and after patterning, dry etching with oxygen, carbon tetrafluoride, etc. is performed to form a lower electrode 203. did. Thereafter, a transparent conductor layer made of tin-doped indium oxide to serve as a pixel electrode was formed, and photopatterning and etching were performed to form a pixel electrode 204. Furthermore, a tantalum oxide layer was formed by anodizing the lower electrode 203 in an aqueous citric acid solution, and the layer was sufficiently fired to remove contained water, etc., to form a nonlinear electrical conduction inducing layer 205.

From above, metal chromium for the upper electrode is formed, photopatterned and etched to form a nonlinear element as the upper electrode 206, and after connecting with the pixel electrode, an insulating layer 207,
A liquid crystal aligned N2O3 was formed to form an element substrate.

A counter substrate was obtained by forming a counter electrode 210 and a liquid crystal alignment layer 211 on a base 209 in the same manner as in Example 1.

These element substrates and counter substrates are placed opposite to each other at an appropriate distance,
A liquid crystal composition 212 was held in between to form a liquid crystal electro-optical device.

As described above, the structure of the element substrate in this comparative example is more complicated than that in Example 1. In addition, since the tantalum of the lower electrode can only be etched by dry etching, a large dry etcher is required, and since it is oxidized to form a nonlinear electrical conduction inducing layer, uniform and dense formation is required. This requires formation at high temperatures.

(Example 2) In this example, a liquid crystal electro-optical device having a configuration as shown in FIG. 3 was prototyped. After forming a pixel electrode 302 on a base 301, a lower electrode 303, a nonlinear electrical conduction inducing layer 304,
An upper electrode 305 and a liquid crystal alignment layer 306 were formed to obtain an element substrate. In addition, it has been confirmed that if the materials of the upper electrode, pixel electrode, and nonlinear electrical conduction inducing layer are selected appropriately, it is possible to omit the lower electrode and form a nonlinear element using a part of the pixel electrode and the upper electrode. did.

The nonlinear element substrate of this example also has a HIM structure.

A counter substrate was obtained by forming a counter electrode 308 and a liquid crystal alignment layer 309 on a base 307 in the same manner as in Example 1.

These element substrates and counter substrates are placed opposite to each other at an appropriate distance,
A liquid crystal composition 310 was held in between to form a liquid crystal electro-optical device.

According to the configuration of this embodiment as described above, the nonlinear electrical conduction inducing layer is coated on the pixel electrode, but since the coating covers the entire surface of the pixel electrode and the film is very thin, it does not touch the liquid crystal part. The capacity becomes extremely large. Therefore, the nonlinear electrical conduction inducing layer in this portion behaves as an almost perfect insulator, and does not reduce the voltage applied to the liquid crystal.

In addition, this layer can block the DC component of the pixel electrode, so there is no need for an extra pixel electrode DC component blocking layer, and the liquid crystal alignment layer on the element substrate side can also be made thinner. It was confirmed that a liquid crystal electro-optical device can be constructed even if the liquid crystal alignment layer 309 is omitted by performing appropriate alignment treatment on the upper nonlinear electrical conduction inducing layer.

The liquid crystal electro-optical device prototyped in this example also exhibited good electro-optic characteristics as in Example 1.

(Example 3) In this example, a liquid crystal electro-optical device having a configuration as shown in FIG. 4 was created. After forming a pixel electrode 402 on a base 401, a first electrode 403 and a third electrode 4 of a nonlinear element are formed.
04 was formed at the same time, and a nonlinear electrical conduction inducing layer 405, a second electrode 406, and a liquid crystal alignment layer 407 were formed to obtain an element substrate. In the element substrate having this configuration, the first electrode used for long wiring can be formed with low resistance while having the advantage that the liquid crystal alignment layer can be made thin as in Example 2, which is very advantageous. Furthermore, as in Example 2, the liquid crystal alignment layer 407
It was confirmed that the nonlinear electrical conduction inducing layer on the pixel electrode can be used as a liquid crystal alignment layer by omitting the above. Furthermore, if the materials of the first electrode, second electrode, pixel electrode, and nonlinear electrical conduction inducing layer are appropriately selected, the third electrode can be omitted and a part of the pixel electrode can be used instead to form a nonlinear element. It was confirmed in the same manner as in Examples 1 and 2 that this is also possible.

The nonlinear element substrate created in this example consists of a conductor (first electrode) - nonlinear electrical conduction inducing layer - conductor (second electrode) - nonlinear electrical conduction inducing layer - conductor - third electrode or pixel electrode). It becomes a structure. In the following specification, such a structure will be referred to as M
It is abbreviated as IMIM structure. In the present invention, since a nonlinear electrical conduction inducing layer having large nonlinear electrical conductivity is used, a nonlinear element having a MIMIM structure can be used.

The counter substrate is the base 408 as in the first and second embodiments.
A counter electrode 409 and a liquid crystal alignment layer 410 were formed thereon. It is also the same as in Examples 1 and 2 that these element substrates and counter substrates are made to face each other and a liquid crystal composition 411 is held between them to form a liquid crystal electro-optical device.

The liquid crystal electro-optical device prototyped in this example also exhibited good electro-optic characteristics as in Examples 1 and 2.

(Example 4) In this example, a liquid crystal electro-optical device having a configuration as shown in FIG. 5 was created. On the base 501, a pixel electrode 502, a lower electrode 503, a nonlinear electrical conduction inducing layer 504, and an upper electrode 50.
5. A liquid crystal composition layer 506 dispersed in a polymer, a pixel electrode 507, and a protective layer 508 were sequentially formed to obtain a liquid crystal electro-optical device.

With the configuration of this example, compared to the liquid crystal electro-optical devices created in Examples 1 to 3, there is no need to manage the gap in the liquid crystal electro-optic element section, and there is no need for a polarizer or analyzer. Be able to use light effectively. Since gap management becomes less important, the substrate used can be a plastic substrate such as polycarbonate, in addition to a non-flexible substrate such as a glass substrate.

Further, in addition to the above-mentioned elements, the structure is simplified because the base body is only required on one side, and a liquid crystal electro-optical device can be manufactured easily and at low cost.

The liquid crystal electro-optical device created in this example also has Examples 1 to 3.
It also showed good electro-optical properties.

In the liquid crystal electro-optical device with this configuration, the electro-optical characteristics can be evaluated without using a polarizer or analyzer, and in this case, the display is brighter than in the conventional device.

Although the embodiments have been described above, the present invention is not limited to the embodiments described above. As the electrode, it is possible to use a conductor other than metal, and as for the formation method, methods such as electroplating, electroless plating, coating, and baking after coating can be used.

As the structure of the nonlinear element, MIM taken up in the example
In addition to the structure and MIMIM Suzukuri, everything except the second conductor was created in the same manner as in Example 3, and a semiconductor film was used as the second conductor.
A junction is formed at the interface to form a conductor - a nonlinear electrical conduction inducing layer - a semiconductor - a nonlinear electrical conduction inducing layer - a conductor (MISIM)
It is also possible to create structures.

Further, the liquid crystal electro-optical element of the present invention can be widely applied to light control such as display devices and optical shutters.

As described above, according to the present invention, it is possible to create a high-performance liquid crystal electro-optical device using an inexpensive and simple process. Especially when creating large-area liquid crystal electro-optical devices, vacuum equipment is used to a minimum.
The present invention is very effective.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the concept of a liquid crystal electro-optical device created in Example 1 of the present invention. FIG. 2 is a cross-sectional view showing the concept of a conventional liquid crystal electro-optical device created as a comparative example. FIG. 3 is a cross-sectional view showing the concept of a liquid crystal electro-optical device created in Example 2 of the present invention. FIG. 4 is a cross-sectional view showing the concept of a liquid crystal electro-optical device created in Example 3 of the present invention. FIG. 5 is a cross-sectional view showing the concept of a liquid crystal electro-optical device created in Example 4 of the present invention. [Effect of the invention] 101... Base for element substrate 107...-
108 108 109 110 Lower electrode Nonlinear electrical conduction inducing layer Upper electrode Pixel electrode Liquid crystal alignment layer Substrate for counter substrate Counter electrode Liquid crystal alignment layer Liquid crystal composition Substrate for element substrate Tantalum oxide layer Lower electrode Pixel electrode Nonlinear electrical conduction inducing layer Upper electrode Insulating layer Liquid crystal alignment layer Substrate for counter substrate Counter electrode Liquid crystal alignment layer Substrate for counter substrate Counter electrode Liquid crystal alignment layer Liquid crystal Composition 501 ... ... ... 502 ... ... 503 ... ... 504 ... ... 505 ... ... ... 506 ... ..... 507 .. .. .. .. 508 .. . Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki (1 person 210...
...Liquid crystal alignment layer 211...Base for liquid crystal composition element substrate Pixel electrode Lower electrode Nonlinear electrical conduction inducing layer Upper electrode Liquid crystal alignment layer Substrate for counter substrate Counter electrode Liquid crystal alignment layer Liquid crystal composition element Substrate base pixel electrode 1st electrode 3rd electrode Nonlinear electrical conduction inducing layer 2nd electrode Fig. 3

Claims (1)

[Claims] At least, a nonlinear element formed by sandwiching a nonlinear electrical conduction inducing layer containing an organic substance as a component between electrodes, and a liquid crystal electro-optical element formed by sandwiching a substance containing a liquid crystal composition between pixel electrodes are combined. Characteristic liquid crystal electro-optical device.