JPH01243024A - Liquid crystal oriented film formed by using patterned high-polymer film and production thereof - Google Patents

Abstract

PURPOSE:To prevent the flawing on the surface of an oriented film and the exfoliation of the film, the failure of driving electrodes and the resultant defective orientation and the quality degradation of a display element by forming grooved patterns on the surface of the oriented film by utilizing a lithographic technique. CONSTITUTION:After a coated film consisting of a photosensitive high polymer is formed on a substrate 1 on which an electrode layer 2 is formed, the film is irradiated with UV rays and X rays through a mask having the parallel stripe patterns; thereafter, the film is irradiated with finely stopped-down electron rays. The film is then developed and is in some cases subjected further to a ring closure treatment. The liquid crystal oriented film 3 consisting of the high-polymer compd. having the fine and parallel groove-like patterns 4 is thus produced. The flawing of the surface of the oriented film 3 and the exfoliation of the film at the time of the rubbing as well as the failure of the driving electrode and the resulted defective orientation and the quantity degradation of the display element are thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal alignment film that is a component of a liquid crystal display element and a method for manufacturing the same.

[Prior art and problems to be solved by the invention] In liquid crystal display elements driven by the action of an electric field, liquid crystal molecules are arranged neatly to display beautiful images, or when electrodes on a glass substrate come into direct contact with liquid crystal molecules. In order to prevent this deterioration, a liquid crystal alignment film is provided on the substrate with electrodes.

As a method for forming a liquid crystal alignment film, there is a conventional rubbing method. This method is a simple method in which an alignment film coated on an electrode is rubbed in a fixed direction with a cloth or the like to form grooves on the surface, and is widely used because of its low cost and the physical properties obtained from it. However, with this method, it is difficult to uniformly form fine, parallel grooves over a wide area of the surface of the alignment film.

As larger areas and increased numbers of pixels are desired, display uniformity may be insufficient, and defects such as poor alignment and quality deterioration due to scratches on the surface of the alignment film during rubbing and damage to drive electrodes, and defects due to flaking may occur. This is becoming an important issue.

On the other hand, there is an oblique vapor deposition method as a method for aligning liquid crystal without rubbing, but this method has problems of increasing the area and increasing cost. Therefore, there has been a need for a method that can change the orientation favorably without rubbing.

Recently, the following new technique has been proposed as a method for forming grooves in place of the rubbing method. One method is to reverse sputter a polymer film to form fine irregularities (Japanese Unexamined Patent Publication No. I2-215925). However, this method requires precise control of the size, shape, and density of the irregularities. It is not possible.

The other method is to form molecular-order irregularities on the surface of the alignment film (JP-A-62-215926, JP-A-Sho [12-
No. 215927), but these publications do not describe any method for forming the unevenness.

[Means for Solving the Problems] Therefore, the present inventors solved the above problems by forming a groove-like pattern on the surface of the alignment film using lithography technology. That is, after forming a photosensitive polymer film on a substrate on which at least an electrode layer is formed, ultraviolet rays or X-rays are irradiated through a mask with a pattern of fine parallel stripes, or a narrow electron beam is irradiated. He discovered that it was possible to create a liquid crystal alignment film of a polymer compound with a fine, parallel groove-like pattern by irradiating it, developing it, and in some cases further ring-closing treatment, and completed a practical liquid crystal alignment film. reached.

The polymer compound used in the present invention can be exposed to light, electron beams or X-rays.
There are no particular limitations on the material as long as it has photosensitivity to be crosslinked or decomposed by radiation.

As a desirable general example, an at least divalent first radical R1 having at least two carbon atoms and an at least divalent second radical R2 having at least two carbon atoms form a divalent bond. R3 is a hydrocarbon-containing group or a hydrogen atom having from 1 to 42 carbon atoms, which has linear repeating units alternately connected by groups and may contain substituents bonded to the same repeating unit by covalent bonds; It is a polymer compound containing at least one, preferably two. Further, the hydrocarbon-containing group may be attached through an ionic bond. The polymer compound imparted with a hydrocarbon-containing group by ionic bonding comprises at least a trivalent first radical R1 having at least two carbon atoms and an at least divalent second radical R1 having at least two carbon atoms. having linear repeating units in which the free radicals R2 of R2 are alternately connected by divalent bonding groups, and bonded to the same repeating unit by ionic bonding, and having a carbon number of 1 to 42 and may contain substituents.
It is a polymer compound containing at least one hydrocarbon-containing group or hydrogen atom R3.

In the above polymer compounds, the first and second free radicals R1
When one or both of R2 and R2 is a benzenoid structure group having at least 6 carbons, not only the resulting thin film has excellent heat resistance, but also the ultraviolet absorption band of the benzenoid structure It is believed to help light be absorbed efficiently into the thin film.

Furthermore, if the polymer compound has a precursor structure that produces a 5-membered ring or 6-membered ring, it can be reacted to produce a 5-membered ring or a 6-membered ring.
This is desirable because it can be converted into a heat-resistant structure with a membered ring.

Preferred specific examples of the polymer compound used in the present invention are as follows.

[Margins below] In formula (6), R6 is -0+, -co -, -s +, -5Oz
+.

R7: Alkyl or aryl group.

In (1) to ■, R3 is a hydrogen atom or a hydrocarbon-containing group having 1 to 42 carbon atoms, and preferable examples include aliphatic, cycloaliphatic and aliphatic, aromatic and aliphatic bonded groups, and groups thereof. Examples include monovalent groups selected from the substituents, and specific examples thereof include, for example, CH when R3 contains an unsaturated bond that can be dimerized or polymerized.
z,=CHCCHzbu.

CH3(CHz)IC=C-C=C(CHzr".

(l+m+1-p) CH3 CHz=C-C-0(CHz)p-.

CHz"CHCFIzOC(GHz)p-(p is 10 to 30).

As shown in many specific examples of R3 containing a polymerizable unsaturated bond, the monovalent group having a polymerizable unsaturated bond is -0-,
-COO-, -NIICO-1-CO-1-S-1-C
-(C)12) with 3S-, -NHO2-5-C8-, etc.
A derivative group substituted with n- is also a preferred embodiment of the present invention.

Substituents for these include a halogen atom, nitro group, amino group, cyano group, methoxy group, acetoxy group, etc., but are not essential.

There is no particular limitation on the molecular weight of the polymer compound of the present invention. However, even if the molecular weight is low, it is possible to form a film by the film forming method of the present invention, but it has good heat resistance, mechanical strength,
Chemical resistance cannot be underestimated. On the other hand, if the molecular weight is too large, the viscosity will be too high and film formation will not be successful. Therefore, the number average molecular weight is about 2,000 to 300,000, preferably about 10,000 to 150,000.

Practical specific examples of polymer compounds into which hydrocarbon-containing groups are introduced through ionic bonding are as follows.

[Left below] (In formula (23), R6 is the same as the definition in formula (6))] (3)
~(34) In the formula, - represents isomerism.

For example, if explained using the formula (3) below, and represents.

The present invention includes cases in which (3-1) or (3-2) is used alone, and cases in which (3-1) and (3-2) coexist. (At least one of R3, R4, and R5 in 2υ~(34) is the same as the definition and example of R3 in (1)~■, and the others are carbon atoms with 1 to 42 carbon atoms that may have substituents. A hydrogen-containing group or a hydrogen atom, preferably having 1 carbon atom
~4 hydrocarbon-containing groups or hydrogen atoms.

Although the aforementioned polymer compounds can be used, it is easier to use a commercially available photosensitive polymer solution. For example, in the case of photosensitive polyimide, Bilarin (manufactured by DuPont Japan Limited), Photonice (manufactured by Toshi), Selectilux (manufactured by Merck & Co., Ltd.), etc. can be used.

Next, a method of patterning will be explained.

First, a coating film of a polymer compound is prepared on a substrate. The film thickness is usually preferably 0.1 to 5 times.

As the application method, spin cord, cast, dip method, etc. are adopted. Next, this coating film is irradiated with ultraviolet rays, X-rays, etc. through a mask, or is irradiated with an electron beam for drawing. In particular, ultraviolet light is desirable, and it is further desirable to use excimer laser light such as KrF because it allows a high-resolution pattern to be scanned and the exposure time can be shortened.

For example, a pattern can be obtained by exposing to ultraviolet light through a positive mask and then dissolving and removing the exposed areas with a developer.

In this case SJ, Kosar rLight Sen
sltlveSystems J (John Wi
ley & 5ons, Inc., New York,
In some cases, it is preferable to use the sensitizers described in 1985), 9.143-148.180-188. For example, mihiraketone, benzoyl ether, 2
Examples include -1-butyl-9,10-anthraquinone, 1,2-benzo-9,10-anthraquinone, and 4,4'-bis(diethylamino)benzophenone.

The developer is preferably a mixed solvent system of dimethylacetamide, dimethylformamide, dimethylsulfoxide, hexamethylphosphoramide, N-methylpyrrolidone, etc., and methanol, ethanol, etc. In some cases, ammonia water and alkaline solutions can also be used.

The thus obtained liquid crystal alignment film (3) of the present invention is formed so as to have a groove-like pattern on a transparent electrode (2) formed on a glass substrate (1), as shown in FIGS. 1 and 2, for example. has been done. In the embodiment shown in Fig. 1, the groove (4) is formed up to the electrode (2) surface, but as shown in Fig. 2, a portion of the polymer film is left at the bottom of the alignment film (3). It may be designed as such.

The depth of the groove (ω, Fukuyama of the groove) and the interval between the grooves, that is, the line width (C) are both preferably in the range of 10 to 3000 nm, preferably in the range of 50 to 1000 nffl from the viewpoint of productivity. Note that these relationships do not necessarily have to be equal, and may be appropriately selected depending on the application, liquid crystal type, liquid crystal material, etc.

The depth of the groove (ω can be adjusted by the energy during irradiation, the width of the groove (b>) and the line width (C), the so-called line and space size, can be adjusted by the line of the mask in the case of ultraviolet and X-ray exposure. In the case of electron beam exposure, the size of the space can be adjusted by adjusting the line width of the electron beam and the drawing interval.

Furthermore, the pattern of the polymer compound of the present invention obtained by these methods shows that the polymer compound has a 5-membered ring or a 6-membered ring.
When a precursor structure that generates a membered ring is provided, a pattern is obtained and then reacted to convert it into a 5- or 6-membered ring structure to form a pattern of a heat-resistant polymer thin film. By selecting the molecular structure, heat resistance of 300°C or higher, preferably 500°C or higher can be achieved. Among the examples (1) to (34), (3) to 4, and (
2Il~(30) or a 5-membered ring containing a heteroatom or 6H
This is an example in which the ring can be partially or completely closed, and the structure after complete ring closure is as follows.

The ring closing method is not particularly limited, but for example, in the case of imidization, which is a specific example of the above formula (5), 30
By heating to a temperature around 0-400℃ (5)
The reaction of the polymer compound (5)" + 2 R3011 of the formula occurs and ring closure is achieved. At this time, the group introduced for esterification is eliminated as an alcohol,
This desorbed alcohol can be dispersed by placing it under a gas flow or under a vacuum at a temperature of around 200' to 400°C, so it cannot pass through the extremely heat-resistant polyimide thin film. can.

Of course, a chemical curing agent such as acetic anhydride, pyridine, or isoquinoline used in general imidization, or heat may be used in combination with the curing agent.

The liquid crystal element is produced by holding the polymer film surfaces of two glass substrates on which the liquid crystal alignment films prepared in this way are facing each other and bonding them with a portion left, and then attaching them to the cell bonded in this way. , is obtained by injecting ferroelectric liquid crystal through this opening and then sealing the opening.

Next, the liquid crystal alignment film of the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

EXAMPLE Coat Fetnis 3100 (photosensitive resin manufactured by Toshi Co., Ltd.) using a spin coater on a glass substrate on which a Nesa pattern has been formed (3000 rpm for 30 seconds), and the film thickness is 1.
Take three prisoners. Next, prebaking is performed at 80° C. for 60 minutes using a clean oven. This thin film of the precursor was exposed to light for 3 seconds using an ultra-high pressure mercury lamp (10Ilv/C112) through a photomask with lines and spaces.

Next, ultrasonic development is performed using a special developer DV-140 (manufactured by Toshi Co., Ltd.) for 35 seconds at 25°C), and ultrasonic rinsing is performed using an inproper tool (for 15 seconds at 25°C).

Finally, imidization is carried out by heat curing in a nitrogen atmosphere (18
0℃ 30 minutes + 300℃ 30 minutes + 400'030
minutes).

The groove depth of the groove-like pattern of the obtained alignment film is 550 na.
+, the groove width is 11000n, and the line width is 11000n.

The polyimide film surfaces of the two glass substrates on which the liquid crystal alignment films produced in this way were formed are held in a state where they are opposed to each other, and are bonded to each other, leaving only a portion.

A ferroelectric liquid crystal (manufactured by Merck & Co., Ltd., ZL13489) is injected into the thus bonded cell through the opening, and then the opening is sealed to produce a liquid crystal element.

When this cell was used to evaluate the alignment of the liquid crystal, it showed good alignment with no alignment unevenness.

Although ferroelectric liquid crystal is used as the liquid crystal, it is not necessarily limited to this, and twisted nematic type and super twisted nematic type may also be used.

[Effects of the Invention] As explained above, this invention is made by exposing a coated film of a photosensitive polymer compound to ultraviolet rays, electron beams, or X-rays, developing it, and subjecting it to ring closure in some cases. By applying a patterned polymer film to a liquid crystal alignment film,
It is possible to prevent scratches on the surface of the alignment film, peeling of the film, damage to the drive electrodes, and resulting poor alignment and deterioration in the quality of display elements that occur with conventional rubbing methods, and provides good alignment and high heat resistance. It is possible to produce a liquid crystal alignment film having the following properties.

[Brief explanation of the drawing]

1 and 2 are schematic perspective views of the liquid crystal aligning film of the present invention provided on a substrate. (Main symbols in the drawings) (1) Ni glass substrate (21 = transparent electrode (3): alignment film (4): groove (a): groove depth peak): groove width (C) Ni line width Patent applicant Kane Fuchi Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A liquid crystal alignment film which is a polymer film having a pattern of parallel grooves formed on a substrate on which at least an electrode layer is formed. 2 The vertical depth of the grooves in the groove-like pattern is 10 nm ~
The liquid crystal aligning film according to claim 1, characterized in that the thickness is 3000 nm, preferably 50 nm to 1000 nm. 3 The horizontal width of the grooves in the groove-like pattern is 10 nm to 3
2. The liquid crystal aligning film according to claim 1, wherein the liquid crystal alignment film has a thickness of 000 nm, preferably 50 nm to 1000 nm. 4 The interval between the grooves of the groove-like pattern is 10nm to 3000n
2. The liquid crystal alignment film according to claim 1, wherein the liquid crystal alignment film has a thickness of 50 nm to 1000 nm. 5. Claim 1, Claim 2, Claim 3, or Claim obtained by irradiating a coating film of a photosensitive polymer compound with ultraviolet rays, electron beams, or X-rays, and then subjecting it to development or ring-closing treatment. Item 4. The method for producing a liquid crystal alignment film according to item 4.