JPH05142549A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To improve thickness accuracy and position accuracy and to prevent the degradation in quality by constituting spacers of patterns consisting of a photosetting resin compsn. and particles size. CONSTITUTION:A photosetting resin compsn. layer 2 is formed on a substrate 1 formed with picture element electrodes and is irradiated with active rays 4, such as UV rays, via a photomask 3 having the prescribed patterns. The uncured parts are removed by development processing. The particles 6a having the uniform grain size are then sprayed onto the substrate 1 formed with the patterns 2a, by which the particles 6a are captured on the surfaces of the patterns 2a. The particles 6a are pushed into the patterns 2a and the patterns 2a are deformed when a substrate 7 is heated and press contacted onto the particles 6a after the particles 6a are left only in the parts of the patterns 2a. The substrates 1, 7 face to each other apart by as much as the grain size of the particles 6. Then, the spacers consisting of the 6a having the excellent thickness accuracy can be disposed in the prescribed parts between the substrates 1 and 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel having a spacer having excellent thickness accuracy and positional accuracy.

[0002]

2. Description of the Related Art Conventionally, the display characteristics of a liquid crystal display panel are closely related to the thickness accuracy between substrates sandwiching a liquid crystal,
It is known that a decrease in thickness accuracy causes defects such as color unevenness.

Therefore, in order to accurately maintain the thickness between the substrates at a constant interval, particles having a uniform particle size are provided as spacers between the substrates. Since it is carried out by the method of spraying upward, only the average spraying amount per unit area can be controlled, and it was difficult to spray the required amount to a specific site.

Therefore, there is a problem that the quality of the liquid crystal display panel is deteriorated due to the mixing of particles in a portion where the particles are not required to be dispersed, for example, in display pixels. In order to solve the above problems, a method of using a photocurable resin capable of forming a pattern by exposure and development as a spacer,
JP-A-48-71596 and JP-A-1-257.
No. 824 is disclosed.

In the above method, the spacer can be arranged at an arbitrary position on the substrate. However, the thickness of the spacer changes due to exposure and development of the photocurable resin, and the spacer has a weak strength and is deformed by compression. Because it is easy to cause damage,
There is a problem in that the thickness accuracy is inferior to that of particles that have been conventionally used as spacers.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to use a spacer excellent in thickness accuracy and position accuracy to eliminate color unevenness due to a decrease in thickness accuracy. An object of the present invention is to provide a liquid crystal display panel that prevents deterioration of quality due to mixing of particles into display pixels.

[0007]

In a liquid crystal display panel according to the present invention, a pair of substrates provided with display pixel electrodes are opposed to each other with a spacer therebetween at a constant interval, and liquid crystal is sealed between the substrates. In the liquid crystal display panel fixed by adhesion, the spacer is composed of a pattern made of a cured product of a photocurable resin composition and particles embedded in the pattern having a uniform particle size. Therefore, the above object is achieved.

The present invention will be described below. The substrate used in the present invention is required to have transparency, heat resistance, rigidity, etc., and, for example, a plate glass used in a normal liquid crystal display panel is suitable.

The display pixel electrode is not particularly limited as long as it is transparent and can apply an effective applied voltage to the liquid crystal. For example, commonly used ITO (indium tin oxide) is suitable. .. As a method of forming the electrodes,
Any method may be adopted, for example, an ITO thin film may be formed on the substrate by vapor deposition, sputtering, or the like, and an arbitrary image pattern may be etched using a resist material.

The liquid crystal is not particularly limited, and generally used TN and STN types are preferably used. The photocurable resin composition used in the present invention,
Although not particularly limited, for example, a resin composition including a binder polymer, a photopolymerizable oligomer, and a photopolymerization initiator is used.

The binder polymer is preferably an acrylic polymer from the viewpoint of film property and sticking property, and examples thereof include methyl (meth) acrylate, propyl (meth) acrylate, -n-butyl (meth) acrylate, and ( Meta)
Isobutyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, α-chloro (meth) acrylic acid methyl ester ,
A copolymer of (meth) acrylic acid with a (meth) acrylic acid ester such as phenyl (meth) acrylate or dimethylaminoethyl (meth) acrylate is preferable.

When the amount of (meth) acrylic acid in the binder polymer is small, it becomes insoluble in an alkaline aqueous solution and development cannot be carried out. On the contrary, when it is large, the compatibility with the solvent or other components is lowered, Since the resolution is also lowered, it is preferable to add 15 to 35% by weight of (meth) acrylic acid to 65 to 85% by weight of (meth) acrylic acid ester.

When the weight average molecular weight of the binder polymer is small, the film-forming property is poor, and when it is large, on the other hand, the solubility in an alkaline aqueous solution is low, development is difficult, and the resolution is low. The range of 50,000 to 300,000 is suitable.

As the photopolymerizable oligomer, known photopolymerizable compounds such as urethane acrylate, epoxy acrylate and polyol acrylate can be used. In the present invention, the urethane represented by the following general formula (I) is used. It is preferable to use an acrylate alone or to use a urethane acrylate represented by the general formula (I) in combination with a known photopolymerizable compound.

[0015]

[Chemical 1]

In the formula (I), R ¹ and R ² are hydrogen or a methyl group, Y is a divalent hydrocarbon group having 2 to 20 carbon atoms,
q is an integer of 1 to 15, R ³ is a hydrocarbon group having 1 to 10 carbon atoms, and p is an integer of 1 to 100.

Here, 2 having 2 to 20 carbon atoms represented by Y
As the valent hydrocarbon group, a hydrocarbon group composed of a linear, branched, alicyclic or aromatic moiety, for example,
Hexamethylene group, tolylene group, isophorone group, tetramethylxylylene group, naphthylene group and the like can be mentioned.

When the weight average molecular weight of the urethane acrylate represented by the formula (I) is small, the flexibility of the resin is lowered, and conversely, when it is large, the developing time is prolonged, so that 1,50
The range of 0 to 10,000 is preferable.

As the method for producing the above-mentioned urethane oligomer, any method may be adopted. For example, diisocyanate and diol are mixed and reacted at a ratio matching the composition ratio of the desired compound, and a urethane oligomer having an isocyanate group at the terminal is obtained. After the formation, a (meth) acrylate having a hydroxyl group may be added and reacted with an isocyanate group at the end. At this time, if necessary, the reaction may be carried out by dissolving it in an organic solvent such as ethyl acetate, methyl ethyl ketone, or toluene, and a catalyst such as dibutyltin dilaurate may be added.

When the amount of the photopolymerizable oligomer is small, the flexibility of the photocurable resin layer after exposure and development is lowered, and conversely, when it is large, cold flow is likely to occur and the resolution is lowered. The amount is preferably 5 to 150 parts by weight, more preferably 10 to 100 parts by weight, based on 100 parts by weight of the binder polymer.

The photopolymerization initiator used in the present invention may be any one having a property of activating the above-mentioned photopolymerizable polymer by actinic rays such as ultraviolet rays and visible rays to initiate polymerization.

As those which are activated by ultraviolet rays, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzyl dimethyl ketal, benzophenone, dimethylaminobenzophenone, Michler's ketone, benzyl anthraquinone, t-butyl anthraquinone, 2-methyl anthraquinone, 2 -Aromatic carbonyl compounds such as ethylanthraquinone, 2-aminoanthraquinone and 2-chloroanthraquinone; thioxanthones such as thioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone and 2,4-diethylthioxanthone; benzoyl peroxide, di- Peroxides such as t-butyl peroxide, dicumyl peroxide and cumene hydroperoxide; such as benzenediazonium ( ) It can be used known ones such as azo compounds.

The amount of the photopolymerization initiator is determined in consideration of the thickness of the photocurable resin composition layer and the irradiation light amount. For example, when it is necessary to shorten the exposure time in the process, it is necessary to increase the amount of the photopolymerization initiator. Therefore, the amount of the photopolymerization initiator added is 100 parts by weight of the binder polymer.
0.1 to 10 parts by weight is preferable.

In addition, the photocurable resin composition used in the present invention contains a photopolymerizable monomer such as tetraethylene glycol diacrylate; dioctyl phthalate, triethylene glycol diacetate, p-toluene sulfonamide, N-ethyltoluene. Plasticizers such as sulfonamides;
A thermal polymerization inhibitor such as hydroquinone or p-methoxyphenol; a stabilizer; an ultraviolet absorber; an antioxidant; a solvent such as methyl ethyl ketone or toluene may be added.

As the particles having a uniform particle size used in the present invention, for example, a material commercially available as a gap material for a liquid crystal display panel can be used. Next, a method for manufacturing the liquid crystal display panel of the present invention will be described.

First, as shown in FIG. 1, a photocurable resin layer 2 is formed on a substrate 1 on which pixel electrodes are formed. The photocurable resin layer 2 may be formed by directly applying a solution obtained by adding a solvent to the photocurable resin composition onto the substrate 1, or by forming a film into a photocurable resin composition (photocurable resin film) in advance.
May be laminated on the substrate 1 by a thermal laminating method or the like.

The photocurable resin layer 2 is irradiated with an actinic ray 4 such as an ultraviolet ray through a photomask 3 having a predetermined pattern to cure a predetermined portion. Then, the uncured portion of the photo-curable resin layer 2 is developed and removed by an alkaline aqueous solution to remove it, thereby forming a predetermined pattern of the photo-curable resin on the substrate 1.

Here, instead of using the photomask 3, the photocurable resin layer 2 may be cured by scanning with a beam of a light source such as a laser. Also, FIG.
As shown in, the pattern 2b may be previously formed on the substrate 5 having releasability by the same method as described above, and the pattern 2b may be transferred onto the substrate 1.

In the method of forming a pattern on the substrate 1 by such transfer, for example, since the pattern can be formed without exposing the substrate 1 to the developing process, there is a concern that the development may adversely affect the substrate 1. Can be used in some cases.

Next, as shown in FIG. 3, particles 6 having a uniform particle size are dispersed on the substrate 1 on which the pattern 2a is formed. The particles 6a scattered on the pattern 2a are captured on the surface of the pattern 2a.

Further, the particles 6b which have fallen on the portion on the substrate 1 where the pattern 2a is not present can be removed by shaking off the substrate 1 or blowing it off with air.

Here, in order to effectively capture the particles 6 by the pattern 2a, the pattern 2a is heated to give tackiness to the surface, the particles 6 are sprayed with a solvent, or a photocurable resin layer is formed. A method of adding a plasticizer or a tackifier in advance and placing it may be adopted.

After performing the operation for leaving the particles 6 only in the pattern 2a as described above, as shown in FIG.
When the substrate 7 is heated and pressure-bonded onto the particles 6, the particles 6 are pushed into the pattern 2a, and the pattern 2a is deformed.
And the substrate 7 are opposed to each other with a distance corresponding to the particle size of the particles 6 therebetween.

By the above operation, it is possible to dispose a spacer made of particles 6 having an excellent thickness accuracy at a predetermined portion between the substrate 1 and the substrate 7, and to keep the distance between the substrate 1 and the substrate 7 constant. Can be kept.

In the arrangement of the spacers, if the thickness of the photo-curable resin layer formed on the substrate becomes thin, particles cannot be sufficiently fixed, and there is a risk of misalignment. If so, the photocurable resin interposed between the particles and the substrate is not sufficiently deformed by pressure bonding and the thickness accuracy is reduced. Therefore, it is preferably in the range of 20 to 100% of the particle diameter of the particles.

In the present invention, separately from the above operation, particles having a uniform particle size are mixed in advance in the photocurable resin,
It is also possible to form a pattern by laminating this on a substrate to form a photocurable resin layer, and exposing and developing through a photomask.

In this case, the volume of the photocurable resin is preferably in the range of 50 to 300% with respect to the volume of the particles, and the thickness of the photocurable resin is 120% or less of the particle diameter of the particles. Preferably.

In this method, since the photocurable resin is exposed and developed in a state where the particles are mixed, the actinic ray does not reach the photocurable resin below the particles, and this part is uncured. There is a possibility that the unreacted photocurable resin may adversely affect the liquid crystal.

In order to prevent such an adverse effect, it is sufficient to irradiate an actinic ray from the substrate side after development to sufficiently cure the uncured portion. In the present invention, the pattern is formed by exposing and developing a photocurable resin, but the light source for exposing is not particularly limited, and conventionally known ones can be used. A high pressure mercury lamp, a metal halide lamp and the like are preferably used. The developing solution used for development is not particularly limited, but for example, an aqueous solution of sodium carbonate having a concentration of 0.5 to 5% by weight is preferably used. The developing device is not particularly limited, and a known device can be used.

[0040]

EXAMPLES The present invention will be described below based on examples.

(Examples 1 and 2, Comparative Example 1) [Preparation of Photopolymerizable Oligomer] Reflux condenser, dropping funnel,
Hexamethylene diisocyanate 50 in a 5 liter 4-neck flask equipped with a thermometer and mechanical stirrer.
4 g (3 mol), 826 g of dry methyl ethyl ketone (MEK) as a solvent, and 1 g of dibutyltin dilaurate (catalyst) were added and stirred, and 916 g of polyethylene glycol (2 mol, average molecular weight: 458) was further added and refluxed for 5 hours.

Then, 232 g (2 mol) of 2-hydroxyethyl acrylate was added dropwise, the mixture was refluxed for another 5 hours for reaction, and MEK was evaporated to prepare a photopolymerizable oligomer.

[Preparation of Photocurable Resin Composition] 100 parts by weight of binder polymer (methyl methacrylate / butyl methacrylate / methacrylic acid = weight ratio 50/25/25, weight average molecular weight Mw: 150,000) Photopolymerizable oligomer 75 parts by weight Photopolymerizable monomer (component: tetraethylene glycol 75 parts by weight diacrylate) Photopolymerization initiator (component: benzyl dimethyl ketal) (“Irgacure 651” manufactured by Ciba-Geigy) 2.5 parts by weight A solution of the curable resin composition was prepared.

[Preparation of Photocurable Resin Film] The photocurable resin composition solution prepared above was treated with PE having a thickness of 75 μm.
Cast on T-film and dry to obtain thicknesses of 5, 10 and 1
Three types of 5 μm photocurable resin films were prepared.

[Production of Liquid Crystal Panel] Striped ITO is formed on three flat glass substrates by sputtering.
After forming the electrodes, a polyimide film was formed and subjected to rubbing treatment.

Further, the photocurable resin films having the thicknesses of 5, 10 and 15 μm produced above were laminated on another three plate glass substrates to form a photocurable resin layer, and a transparent portion was displayed. Through a photomask designed so that it does not overlap with the pixels, 100
After irradiating with ultraviolet rays having an intensity of mJ / cm ² , development treatment is performed with a 1% sodium carbonate aqueous solution to remove uncured portions,
Each pattern was formed.

Next, the three patterned substrates were thoroughly washed, and spacer particles (“Micropearl SP-210” manufactured by Sekisui Fine Chemical Co., Ltd., particle size: 10 μm) while heating each substrate to 120 ° C. ) Was sprayed, and then dry air was blown to remove unnecessary particles on the substrate.

The substrate on which the pattern was formed and the substrate on which the ITO electrode was formed and subjected to the rubbing treatment were pressure-bonded while being heated to 120 ° C., the peripheral portion was sealed, and liquid crystal was injected under vacuum. , 3 types of liquid crystal display panels corresponding to 3 types of photocurable resin films having different thicknesses were produced.

The obtained liquid crystal display panel was evaluated, and the evaluation results are shown in Table 1.

[0050]

[Table 1]

[0051]

The liquid crystal display panel of the present invention uses particles having a uniform particle size as spacers, and the position of the spacers is determined by the pattern of the photocurable resin exposed and developed. The accuracy is excellent, and it is possible to prevent color unevenness due to thickness variation and quality deterioration due to mixing of particles into display pixels.

[Brief description of drawings]

FIG. 1 is a schematic view showing a situation in which a photocurable resin layer formed on a substrate is exposed and cured through a photomask in the present invention.

FIG. 2 is a schematic diagram showing a situation in which a photo-curable resin having a pattern formed in advance is transferred to a substrate in the present invention.

FIG. 3 is a schematic view showing a situation in which particles having a uniform particle diameter are dispersed on a substrate on which a pattern is formed in the present invention.

FIG. 4 is a schematic view showing a situation in which particles scattered on a pattern are pressure bonded by a substrate in the present invention.

[Explanation of symbols]

 1 substrate 2 photocurable resin layer 2a pattern 2b pattern 3 photomask 4 actinic ray 5 base material 6 particles 7 substrate

Claims (1)

[Claims] 1. A liquid crystal display panel in which a pair of substrates provided with display pixel electrodes are opposed to each other with a spacer interposed therebetween at a constant interval, and liquid crystal is sealed between the substrates by adhesive bonding. A liquid crystal display panel, wherein the spacer comprises a pattern made of a cured product of a photocurable resin composition and particles embedded in the pattern and having a uniform particle size.