JPS6378125A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To easily prevent a switching element from breaking down caused by static electricity and to manufacture a liquid crystal display device at high yield by forming the oriented layer of 10<0>-10<10>OMEGA.cm on a substrate where a switching element is arranged and fixed opposite a liquid crystal compound. CONSTITUTION:Switching elements 40 are arranged fixedly and fixed in a matrix on a lower substrate 12, and row electrodes 21 are formed on an upper substrate 11 so as to cross column electrodes 22 at positions where switching elements 10 are fixed. One terminal of each switching element 40 is connected to a corresponding column electrode 22 and the other terminal is connected to a picture element electrode 23 arranged and fixed to the lower substrate 12. The oriented layer 32 arranged on the lower substrate 12 where the switching elements 40 are arranged and fixed opposite the liquid crystal compound 50 has 10<0>-10<10>OMEGA.cm volume resistivity and one oriented film 31 arranged on the opposite surface of the upper substrate 11 from the liquid crystal compound 50 has >=10<0>OMEGA.cm volume resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix liquid crystal display device.

[Background of the invention]

An active matrix liquid crystal display device includes -a, a pair of substrates, a switching element for driving a liquid crystal fixedly arranged in a matrix on one of the pair of substrates, and a switching element arranged on the pair of substrates. The liquid crystal composition includes a plurality of row electrodes and a plurality of column electrodes for driving and controlling the liquid crystal composition, and a liquid crystal composition disposed between a pair of substrates. As the switching element, a switching element such as a three-terminal switching element such as a MOS transistor or a thin film transistor, or a two-terminal switching element such as a thin film diode, a varistor element, or an MIM element is used.

This active matrix type liquid crystal display device forms a liquid crystal image by directly switching and driving the liquid crystal using switching elements arranged in a matrix, and is capable of displaying a highly detailed image. .

Then, in order to orient the liquid crystal composition disposed between the pair of substrates in a specific direction, an alignment layer is provided on the substrate surface facing the liquid crystal composition. Various methods are conventionally known for forming this alignment layer, but among these, the rubbing method is an extremely simple method. This rubbing method is
After a film of a polymer material such as polyimide, polyamide, polyvinyl alcohol, or phenoxy is applied to the substrate surface, the surface of the film is woven in a certain direction with a cloth such as cotton cloth, vinylon cloth, Tetron cloth, or absorbent cotton. In this method, an alignment layer is formed by rubbing the surface of the substrate to form grooves in a certain direction on the surface of the substrate.

[Problem that the invention seeks to solve]

However, since films of polymeric substances such as polyimide that have been conventionally used to form alignment layers have high insulating properties, high voltage static electricity is generated during the process of forming alignment layers using a rubbing method. The problem is that switching elements are easily destroyed due to this static electricity, and even if this destruction occurs in only one switching element, the entire board becomes unusable, resulting in lower yields and higher manufacturing costs. There is a point. This problem is particularly serious when a MOS transistor is used as a switching element.

On the other hand, in the process of forming row and column electrodes, all of the row and column electrodes are short-circuited around the substrate, and finally the row and column electrodes are separated individually to prevent static electricity. Japanese Patent Publication No. 1987 (1986) discloses a technical means to prevent the destruction of switching elements caused by
(Refer to Publication No.-12268).

However, with this technical means, it is necessary to ultimately separate the row electrodes and column electrodes individually, which requires a considerable amount of effort. Indeed, there is a problem in that the size becomes significantly large, resulting in an increase in manufacturing costs.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide an active matrix type that can easily prevent destruction of switching elements caused by static electricity and that can be manufactured at a high yield. An object of the present invention is to provide a liquid crystal display device.

[Means for solving problems]

The active matrix liquid crystal display device of the present invention includes a pair of substrates, a switching element for driving a liquid crystal fixedly arranged in a matrix on one of the pair of substrates, and a switching element arranged on the pair of substrates. In an active matrix liquid crystal display device comprising a plurality of row electrodes and a plurality of column electrodes for driving and controlling elements, and a liquid crystal composition disposed between the pair of substrates, the switching element is fixedly arranged. A substrate having a volume resistivity of 100 to 1 is placed on the same surface as the liquid crystal composition.
It is characterized by providing an orientation layer having a resistance of 0.010 Ω·cm.

[Function and effect of the invention]

According to the active matrix liquid crystal display device of the present invention, the volume resistivity is 10' to 1.
Since the alignment layer having a resistance of 01eΩ·1 is provided, destruction of the switching element due to static electricity can be sufficiently prevented by simple means. That is, the volume resistivity is lO°
The alignment layer, which has a resistance of ~10"Ω, has lower insulation properties than conventional alignment layers, so even if static electricity is generated due to friction when forming the alignment layer by rubbing, the voltage will be considerably low. Therefore, it is possible to sufficiently prevent the switching elements fixedly arranged on the substrate from being destroyed, and as a result, active matrix liquid crystal display devices can be manufactured with high yield, and costs can be reduced. .

Further, in the present invention, since the lower limit of the volume resistivity of the alignment layer is set to 10'Ω, it is possible to form a clear image without disturbing the liquid crystal image due to leakage between the pixel electrodes, for example.

[Specific structure of the invention]

The present invention will be explained in detail below.

In the present invention, a pair of transparent substrates are prepared, a large number of switching elements for driving liquid crystals are fixedly arranged in a matrix on one of the pair of substrates, and the switching elements are driven and controlled on the pair of substrates. A plurality of row electrodes and column electrodes are arranged to provide a volume resistivity of 100 to IQ+@Ω・value on the surface facing the liquid crystal composition of one substrate on which the switching element is fixedly arranged. An alignment layer is provided, an alignment layer is also provided on the surface of the other substrate that faces the liquid crystal composition, and a liquid crystal composition is placed between the sides of the pair of substrates on which the alignment layer is provided. Constitutes a liquid crystal cell. Then, a polarizing plate is placed on one side and the other side of this liquid crystal cell, and in the case of a reflective type configuration, a reflecting plate is placed on the outer surface of the rear polarizing plate, thereby forming an active matrix type liquid crystal display device. do. Note that in the case of a transmission type configuration, a reflection plate is not necessary.

To explain more specifically, when using, for example, a two-terminal switching element as a switching element, the two-terminal switching elements are fixedly arranged in a matrix on one substrate, and correspondingly, for example, row electrodes are arranged on one of the substrates. Column electrodes are formed on the other substrate such that they intersect with the row electrodes at the positions where the two-terminal switching elements are fixed. One terminal of each two-terminal switching element is connected to the corresponding row electrode, and the other terminal is connected to the corresponding pixel electrode fixedly arranged on the one substrate.

In addition, when using a 3-terminal switching element as a switching element, the 3-terminal switching elements are fixedly arranged in a matrix on one substrate, and the row electrodes are arranged so that these 3-terminal switching elements intersect at the fixed positions. and column electrodes are both formed on the one substrate.

The first terminal of each three-terminal switching element is connected to a corresponding row electrode, the second terminal is connected to a corresponding column electrode, and the third terminal is connected to a corresponding one fixedly arranged on one of the substrates. Connect to the pixel electrode.

In the present invention, the alignment layer provided on one substrate on which the switching element is fixedly arranged has a volume resistivity of 10.
・It is necessary to be ~10'・Ω・mouth. When the volume resistivity of the alignment layer exceeds 10'8 Ω, the electrostatic voltage generated during the rubbing process becomes excessive and cannot sufficiently prevent destruction of the switching element. - When it is less than 1, leakage tends to occur between adjacent pixel electrodes, making it impossible to form a clear liquid crystal image.

Examples of materials that can be used to form the alignment layer having a volume resistivity in a specific range include polyimide, polyamide, polyamideimide, polyphenylene, which contains conductive substances such as carbon and metal particles dispersed therein. Films of heat-resistant polymer materials such as polyvinyl alcohol and polyxylylene, or iodine, arsenic, copper,
Examples include polypillows doped with nickel, magnesium, tin, etc., and films of polymeric substances such as polyacetylene and phthalocyanine.

After depositing a film of such a modified polymer substance on one of the substrates on which the switching element is fixedly arranged,
This film is rubbed to form an alignment layer. Specifically, the alignment layer can be formed by rubbing the surface of the film in a certain direction with a cloth such as cotton cloth, vinylon cloth, Tetoron cloth, absorbent cotton, etc. to form grooves in a certain direction on the surface of the substrate.

Note that an alignment layer is also provided on the other substrate to which the switching element is not fixed, but the volume resistivity of this alignment layer is 1.
It is sufficient if it is 00Ω·1 or more.

In the present invention, the specific configuration of the switching element is not particularly limited, and all switching elements conventionally used for this type of application can be used. in particular,
3-terminal switching elements such as MOS) transistors and thin film transistors; e.g. thin film diodes (Schottky type, PN type, PIN type, etc.), varistor elements, MIM
Typical examples include two-terminal switching devices such as devices.

As the constituent material of the substrate, materials conventionally used for this type of application can be used, and are not particularly limited, such as soda glass, borosilicate glass, quartz glass, R 7059 glass (Corning manufactured by),
Glass such as "Tempax Glass" (manufactured by Jenner);
Plastics such as uniaxially oriented polyethylene terephthalate, polyether sulfone, and polyvinyl alcohol can be used.

Also row electrodes and columns! As the constituent material of the electrode, materials conventionally used for this type of application can be used, and are not particularly limited, such as TTO (tin and indium oxide), NESA (tin oxide), etc. ),chromium,
Aluminum, nickel, nickel-chromium alloy, etc. can be preferably used, and these materials can also be used in combination.

Further, as the liquid crystal composition, those conventionally used for this type of application can be used, and there is no particular limitation. Specifically, for example, nematic liquid crystal, chiral nematic ink liquid crystal, cholesteric liquid crystal, smectine ink liquid crystal, chiral smecten ink liquid crystal, and other known liquid crystals can be used, and a combination of these can also be used. An optically active substance may be added as necessary.

In addition, the display mode is twisted nematic (T
Which mode is adopted, such as N) type mode, guest-host (GH) type mode, voltage-controlled birefringence (ECB) type mode, cholesteritter nematic type phase transition mode, dynamic scattering (DS) type mode, etc. Good too.

A specific example of the structure of an active matrix liquid crystal display device according to the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are an explanatory plan view and an explanatory cross-sectional view, respectively, showing a specific configuration example when a two-terminal switching element is used as the switching element.

In these figures, 11 is an upper substrate, 12 is a lower substrate, 2
1 is a row electrode, 22 is a column electrode, 23 is a pixel electrode, 31 is an alignment layer of the upper substrate, 32 is an alignment layer of the lower substrate, 40 is a switching element, and 50 is a liquid crystal composition.

The 2@ child switching element in this example is a back-to-back diode formed by connecting two thin film diodes in series and in opposite directions, 41 is a common electrode, 42 is a semiconductor layer, 43 is a barrier electrode, 44 is an insulating layer.

The switching elements 40 are fixedly arranged in a matrix on the lower substrate 12, and column electrodes 22 are formed on the lower substrate 12 to correspond to the switching elements 40. and switching element 40
Row electrodes 21 are formed on the upper substrate 11 so as to intersect these column electrodes 22 at fixed positions. One terminal of each switching element 40 is connected to the corresponding column electrode 22, and the other terminal is connected to the corresponding pixel electrode 23 fixedly arranged on the lower substrate 12.

And the lower substrate 1 on which the switching element 40 is fixedly arranged.
In No. 2, the alignment layer 32 disposed on the surface facing the liquid crystal composition 50 has a volume resistivity of 100 to IQIIIΩ·
(2), one of the alignment layers 31 disposed on the surface of the upper substrate 11 facing the liquid crystal composition 50 has a volume resistivity of 100Ω.

FIGS. 2A and 2B are an explanatory plan view and an explanatory cross-sectional view, respectively, showing a specific example of the configuration when a three-terminal switching element is used as the switching element.

In these figures, 11 is an upper substrate, 12 is a lower substrate, 2
1 is a row electrode, 22 is a column electrode, 23 is a pixel electrode, 25 is a counter electrode, 31 is an alignment layer of the upper substrate, 32 is an alignment layer of the lower substrate, 40 is a switching element, and 50 is a liquid crystal composition.

The three-terminal switching element in this example is a thin film transistor, 42 is a semiconductor layer, 44 is an insulating layer, and 45 is a drain electrode.

The switching elements 40 are fixedly arranged in a matrix on the lower substrate 12, and row electrodes 21 and column electrodes 22 are both formed on the lower substrate 12 so that these switching elements 40 cross each other at fixed positions. . The first terminal (gate) of each switching element 40 is connected to the corresponding row 'N, pole 21, and the second
The terminals (sources) of each are connected to the corresponding column electrodes 22, and the third terminal, drain electrode 45, is connected to the corresponding pixel electrode 23 fixedly arranged on the substrate 2.

And the lower substrate 1 on which the switching element 40 is fixedly arranged.
In No. 2, the orientation j131 disposed on the surface facing the liquid crystal composition 50 has a volume resistivity of 10" to 1010 Ω.
One of the alignment layers 32 disposed on the surface of the upper substrate 11 facing the liquid crystal composition 50 has a volume resistivity of 100Ω·1 or more.

[Specific examples]

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

<Examples 1 to 6 and Comparative Examples 1 to 4> In each of the Examples and Comparative Examples, as the constituent material of the alignment layer in the substrate on which the switching element is fixedly arranged,
An active matrix liquid crystal display device having 150 x 150 pixels was actually fabricated using the materials shown in Table 1 below and based on the configuration shown in FIGS. 1(a) and 1(b).

Next, we conducted a test in which each pixel was actually driven, and investigated the proportion of failures due to electrostatic breakdown of switching elements, and the disturbances in liquid crystal images that were thought to be caused by leakage between pixel electrodes. The results are also shown in Table 1.

<Examples 7 to 12 and Comparative Examples 5 to 8> In each of the Examples and Comparative Examples, the materials shown in Table 2 below were used as constituent materials of the alignment layer in the substrate on which the switching element was fixedly arranged, and the second An active matrix liquid crystal display device having 150 x 150 pixels was actually manufactured based on the configuration shown in Figures (a) and (b).

Next, we conducted a test in which each pixel was actually driven, and investigated the proportion of failures due to electrostatic breakdown of switching elements, and the disturbances in liquid crystal images that were thought to be caused by leakage between pixel electrodes. The results are also shown in Table 2.

In addition, in Tables 1 and 2, in the column for liquid crystal image disturbance, "○" indicates that a clear image is obtained with almost no disturbance of the liquid crystal image, and "x" indicates that the liquid crystal image is disturbed. This indicates that there is a problem in practical use.

As can be understood from the results in Tables 1 and 2, in the active matrix liquid crystal display device according to the present invention, the volume resistivity of the constituent material of the alignment layer in the substrate on which the switching elements are fixedly arranged is 100 to 100. Since it is within the range of 10'6 Ω, damage to the switching elements due to static electricity is sufficiently prevented during the rubbing process, and as a result, active matrix type liquid crystal display devices can be manufactured with a small proportion of defective pixels and a low yield. Furthermore, it is possible to form a clear image without causing any disturbance in the liquid crystal image that is thought to be caused by leakage between the pixel electrodes.

On the other hand, according to Comparative Examples 1 and 5, since the volume resistivity of the constituent material of the alignment layer in the substrate on which the switching element is fixedly arranged is less than 100 Ω, no damage due to static electricity is observed, but the pixel Disturbances occur in the liquid crystal image, which is thought to be caused by leakage between the electric bridges, and as a result, a clear image cannot be formed.

Furthermore, according to Comparative Examples 2 to 4 and 6 to 8, the volume resistivity of the constituent material of the alignment layer in the substrate on which the switching elements are fixedly arranged exceeds 10I0Ω, so that the switching elements are destroyed by static electricity during the rubbing process. As a result, the proportion of defective pixels is large, and it is ultimately difficult to manufacture active matrix liquid crystal display devices with a high yield.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are an explanatory plan view and an explanatory cross-sectional view showing an example of a specific configuration of an active matrix liquid crystal display device according to the present invention, respectively, and FIGS. 2(a) and (b) are 2A and 2B are an explanatory plan view and an explanatory cross-sectional view, respectively, showing other examples of the specific configuration of an active matrix liquid crystal display device according to the present invention. 11... Upper board 12... Lower board 21.
... Row electrode 22 ... Column electrode 23 ... Pixel electrode 25 ... Opposing whole surface snow scraper 31 ... Alignment layer of upper substrate 32 ... Alignment layer 40 of lower substrate ...
Switching element 50...Liquid crystal composition 41...Common electrode 42...Semiconductor layer 43...Barrier electrode 44...Insulating layer 45...Drain electrode) Diagram 2 (A) 9μ Diagram 2 ( B)

Claims (1)

[Claims] 1) A pair of substrates, a switching element for driving a liquid crystal fixedly arranged in a matrix on one of the pair of substrates, and a switching element arranged on the pair of substrates for driving the switching element. In an active matrix liquid crystal display device comprising a plurality of row electrodes and a plurality of column electrodes for control, and a liquid crystal composition disposed between the pair of substrates, the switching element is fixedly disposed on one side; The surface of the substrate facing the liquid crystal composition has a volume resistivity of 10.
An active matrix liquid crystal display device characterized in that an alignment layer having a resistance of ^0 to 10^10 Ω·cm is provided.