JPH0895084A - Active matrix liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide an active matrix liquid crystal display element of excellent picture quality by providing a passivation film made of polymer having aliphatic ring system containing fluorine. CONSTITUTION: A passivation film made of polymer having aliphatic ring system containing fluorine is excellent in low dielectric constant and flatness, and small in stress, so as to be excellent in productivity. Such polymer is obtained by polymerizing monomers having ring system containing fluorine, or cyclic- polymerizing monomers containing fluorine having polymerization double bond. In particular, a polymer containing over 20mol% of polymerized units from monomers having ring system in it is desirable from viewpoints of transparency, and mechanical characteristics. The passivation film can be easily formed by coating a solution solving polymer having aliphatic ring system containing fluorine in a fluorine solvent by spin coating, spray coating, dip coating, or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display device having a passivation film made of a polymer having a fluorine-containing alicyclic structure.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as displays for watches, calculators, electronic organizers, word processors, personal computers, televisions, integrated videos, electronic OHPs and the like. Among these, as the driving method of the dot matrix liquid crystal display element,
It is well known that there are a simple matrix system and an active matrix system.

The active matrix system utilizes the switching operation of an active element composed of a transistor or a diode, and is a thin film transistor (hereinafter abbreviated as TFT) system or a metal / insulator / metal (hereinafter abbreviated as MIM) diode system. As represented by, for example, a semiconductor element.

Taking the case of a TFT as an example, a silicon nitride film is used for the passivation film. However, since the silicon nitride film has a large dielectric constant, the voltage drop of the passivation film in the liquid crystal non-operating region is small, and the liquid crystal is Since such a voltage becomes large, the disorder of the alignment of the liquid crystal becomes a problem. Further, since the parasitic capacitance between the electrodes becomes large, the display image quality of the liquid crystal display element may be adversely affected. Further, a plasma CVD apparatus for forming a silicon nitride film is expensive and inferior in productivity. Furthermore, the formed silicon nitride film has problems that the flatness is not sufficient and the stress stress is large.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of active matrix liquid crystal display devices made of conventional materials, has a very low dielectric constant, and is excellent in film-forming productivity. It is an object of the present invention to newly provide an active matrix liquid crystal display device having a passivation film of

[0006]

The present invention is an active matrix liquid crystal display device having a passivation film made of a polymer having a fluorine-containing alicyclic structure.

The polymer having a fluorinated alicyclic structure is obtained by polymerizing a monomer having a fluorinated cyclic structure, or a fluorinated monomer having at least two polymerizable double bonds is cyclopolymerized. A polymer having a ring structure in the main chain obtained as a result is suitable.

A polymer having a ring structure in its main chain obtained by polymerizing a monomer having a fluorine-containing ring structure is disclosed in Japanese Examined Patent Publication No.
No. 18964, for example. That is,
It can be obtained by homopolymerizing a polymer having a fluorine-containing ring structure such as perfluoro (2,2-dimethyl-1,3-dioxole) or by copolymerizing with a radical polymerizable monomer such as tetrafluoroethylene.

Polymers having a ring structure in the main chain obtained by cyclopolymerization of a fluorine-containing monomer having at least two polymerizable double bonds are disclosed in JP-A-63-238111 and 63-238115. It is known from the official gazette. That is, perfluoro (allyl vinyl ether)
It is obtained by cyclopolymerization of a monomer such as or perfluoro (butenyl vinyl ether), or copolymerization with a radical polymerizable monomer such as tetrafluoroethylene.

Further, perfluoro (2,2-dimethyl-
A monomer having a fluorine-containing ring structure such as 1,3-dioxole) and at least 2 such as perfluoro (allyl vinyl ether) or perfluoro (butenyl vinyl ether)
It may be a polymer obtained by copolymerizing a fluorine-containing monomer having one polymerizable double bond.

The polymer having a fluorine-containing alicyclic structure is
A polymer having a ring structure in its main chain is preferable, and a polymer containing a unit in which a monomer having a ring structure is polymerized in an amount of 20 mol% or more is preferable in terms of transparency and mechanical properties.

The polymer having a fluorine-containing alicyclic structure includes a halogen atom, a hydroxyl group, an alkoxy group, an alkoxy-substituted alkoxy group, a hydroxyalkyloxy group, an acyloxy group, in order to improve the adhesion of the polymer.
It is preferable to introduce a highly reactive group such as an aminooxy group, a ketoxime group, an amino group or an amide group.

Adhesion of a polymer is improved by blending a silane coupling agent such as alkoxysilanes, alkoxysilanes having an amino group, an aminophenyl group or an epoxy group with a polymer having a fluorine-containing alicyclic structure. You can also do it.

The semiconductor element used in the active matrix liquid crystal display element of the present invention includes an amorphous silicon TFT using a transistor or a polycrystalline silicon TF.
Examples thereof include T, and examples include MIM diodes using diodes.

The passivation film is a semiconductor layer, an electrode,
A liquid crystal alignment film is formed on the passivation film, which is a protective film formed on the wiring or the like.

In the present invention, the passivation film made of a polymer having a fluorinated alicyclic structure can be formed by a means with good productivity. Since this polymer is soluble in a fluorine-based solvent, it is possible to easily form a film by coating the solution. The film thickness is usually 0.1
It is selected from the range of 2 μm.

Examples of the fluorinated solvent include fluorinated aromatic hydrocarbons, fluorinated alicyclic hydrocarbons, fluorinated alkylamines, fluorinated cyclic ethers, fluorinated polyethers, fluorinated ketones and fluorinated ketones. Aprotic fluorine-containing solvents such as fluoroaliphatic hydrocarbons can be used alone or as a mixture of two or more kinds. Further, protic fluorine-containing solvents such as fluorine-containing alcohols, fluorine-containing carboxylic acids, amides of fluorine-containing carboxylic acids, and fluorine-containing sulfonic acids can be used alone or as a mixture of two or more kinds. In order to reduce the viscosity of the polymer solution and prevent gelation, it is effective to use a mixture of an aprotic fluorine-containing solvent and a protic fluorine-containing solvent.

The coating method is not particularly limited, and spin coating method, spray coating method, die coating method, curtain flow coating method, dip coating method and the like can be exemplified. These coating apparatuses are extremely inexpensive and excellent in productivity as compared with a plasma CVD apparatus for forming a silicon nitride film or the like.

In the present invention, the polymer having a fluorinated alicyclic structure is soluble in a fluorinated solvent having a small surface tension, so that a uniform and flat thin film can be easily obtained by coating with a solution.

Since this polymer is a fluorine-containing polymer, it has an extremely low dielectric constant, high electric insulation and heat resistance. Further, since it is a polymer, it has smaller elastic modulus and stress as compared with the inorganic film. Therefore, the reliability and life of the liquid crystal display element can be improved.

[0021]

EXAMPLES Examples of the present invention will be specifically described, but the present invention is not limited thereto.

"Synthesis Example 1" 35 g of perfluoro (butenyl vinyl ether), 1,1,2-trichloro-1,
5 g of 2,2-trifluroethane, 15 of ion-exchanged water
0 g, and ((CH ₃ ) ₂ CHOC as a polymerization initiator)
90 mg of OO) ₂ was placed in a pressure-resistant glass autoclave having an internal volume of 200 ml. After purging the system with nitrogen three times, suspension polymerization was carried out at 40 ° C. for 22 hours to give 28 g of polymer A.
g was obtained. The intrinsic viscosity [η] of this polymer was 0.50 at 30 ° C. in perfluoro (2-butyltetrahydrofuran).
Met. The glass transition point of the polymer is 108 ° C., and it is a tough and transparent glassy polymer at room temperature. Again 10
The% thermal decomposition temperature was 465 ° C., the light transmittance was as high as 95% or more, and the dielectric constant was as low as 2.1. Subsequently, a solution A was prepared by dissolving the polymer A in perfluorotributylamine at 7% by weight.

"Synthesis Example 2" Radical copolymerization of perfluoro (2,2-dimethyl-1,3dioxole) and perfluoro (butenyl vinyl ether) was carried out to give a glass transition point 1
A copolymer B having a temperature of 60 ° C. was obtained. This copolymer was colorless and transparent, and had a high light transmittance of 95% or more and a low dielectric constant of 2. Subsequently, a solution B was prepared by dissolving the copolymer B in perfluorotributylamine at 7% by weight.

Example 1 Solution A obtained in Synthesis Example 1 was applied to an amorphous silicon TFT before forming a passivation film by spin coating, followed by curing at 200 ° C. to form a passivation film. . The film thickness of the passivation film made of this polymer A was 0.6 μm, and was excellent in flatness as compared with a normal silicon nitride film. The operation characteristics of this TFT were almost unchanged as compared with the TFT having a passivation film made of silicon nitride. In addition, this TFT is 60 ° C, 90% R
There was no change in the operating characteristics of the transistor even after being left in the H environment for 64 hours.

[Example 2] The solution B obtained in Synthesis Example 2 was applied to an amorphous silicon TFT before forming a passivation film by spin coating, followed by curing at 200 ° C to form a passivation film. . The film thickness of the passivation film made of this copolymer B is 0.3 μm.
Therefore, the flatness was superior to that of a normal silicon nitride film. The operation characteristics of this TFT were almost unchanged as compared with the TFT having a passivation film made of silicon nitride. In addition, this TFT is 60%, 90%
After left in the RH environment for 64 hours, the operating characteristics of the transistor did not change.

[Example 3] The solution A obtained in Synthesis Example 1 was used as a polycrystalline silicon TFT before forming a passivation film.
Was applied by a spin coating method, followed by curing at 200 ° C. to form a passivation film. The film thickness of the passivation film made of this polymer A was 0.6 μm. The pixel electrode portion of the passivation film was removed by plasma etching using a normal photolithography means, and after forming an alignment film, a panel into which liquid crystal was injected was prepared. The obtained panel had excellent image quality.

[0027]

INDUSTRIAL APPLICABILITY The present invention uses a polymer having a fluorinated alicyclic structure as a passivation film to obtain a passivation film having a low dielectric constant, excellent flatness, and small stress stress with high productivity. It has an excellent effect of obtaining a panel composed of an active matrix liquid crystal display element having excellent image quality. Further, since the film can be formed efficiently with an inexpensive device, there is an effect that the manufacturing cost of the active matrix liquid crystal display element can be reduced.

Claims (2)

[Claims] 1. An active matrix liquid crystal display device comprising a passivation film made of a polymer having a fluorine-containing alicyclic structure. 2. The liquid crystal display element according to claim 1, wherein the semiconductor element of the active matrix liquid crystal display element is an amorphous silicon thin film transistor, a polycrystalline silicon thin film transistor or a metal / insulator / metal diode.