JP3463968B2 - Transparent conductive film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transparent conductive film used for a film liquid crystal display device.

[0002]

2. Description of the Related Art A transparent conductive film obtained by laminating an oxide thin film of indium and tin on the surface of a polyether sulfone film by a method such as sputtering is known.
It is used as a material for transparent electrode substrates of film liquid crystal display devices. A film liquid crystal display element is constructed by sealing the liquid crystal with a plastic film substrate, but when the internal volume changes due to expansion and contraction or bending of the substrate, the gas that has melted into the liquid crystal becomes bubbles and hinders the display function. However, various measures have been taken to prevent gas from dissolving in liquid crystals. Providing a gas barrier property to a plastic film substrate has also been adopted as an effective means. The gas barrier property is imparted by a method of forming a substance having a gas barrier property on a plastic film by means such as coating or vapor deposition.
In the conventional technology, when the gas barrier substance is a resin such as polyvinyl alcohol or polyvinylidene chloride, a coating method with good productivity and a high degree of perfection of equipment and technology is adopted, but the gas barrier property of these resins is adopted. It has been pointed out that is not perfect because it is affected by temperature and humidity. On the other hand, using metal oxide or glass as a gas barrier substance to form an extremely thin plastic film by a technique such as vapor deposition is being considered, but it has not reached a practical level in terms of productivity and perfection of equipment and technology. . Therefore, it is desired to form a metal oxide or glass, which is excellent as a gas barrier substance, on a plastic film substrate by a coating method which is excellent as a means.

It is already well known that a metal alkoxide hydrolyzate is applied to a base material and heated to form a corresponding metal oxide layer. It is not easy to form a metal oxide layer having adhesion. In particular, when gas barrier properties are required, it is required that the hydrolyzate contains no organic groups as much as possible, and it has been considered that this is inconsistent with the technique for obtaining flexibility and adhesion. Conventionally, the glass transition temperature is 12
The invention has been developed that it is important that a transparent plastic film which is substantially amorphous at 0 ° C. or higher and has a retardation value at the film thickness of 15 nm or less is constituted as a substrate. . (Japanese Patent Application Sho 58-30
926, Japanese Patent Application No. 59-84060, Japanese Patent Application No. 5-2177
75, Japanese Patent Application No. 217776, etc.) In order to improve the adhesion between the transparent conductive film and the plastic film, it is extremely effective to provide an undercoat layer, and the undercoat layer contains a silane coupling agent. Is found. (Japanese Patent Application No. 59-59509, Japanese Patent Application No. 4-2871348, Japanese Patent Application No. 5-188416, etc.)

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent conductive film used for a plastic film liquid crystal display device with an inorganic film having a gas barrier property which is substantially independent of temperature and humidity. It is to impart the film with practically sufficient adhesion without impairing the flexibility of the film.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have studied a technique for forming an inorganic thin film by coating and drying a hydrolyzate of an alkoxysilane compound. In combination with the
A surprising synergistic effect was obtained, leading to the present invention.

That is, at least one surface of the transparent plastic film substrate (A) having a glass transition temperature of 120 ° C. or higher, being substantially amorphous, and having a retardation value at the film thickness of 15 nm or less, -OR ₁
(The boiling point of the compound represented by H-OR ₁ at atmospheric pressure is 12
A substance having a functional group represented by (an alcohol residue at 0 ° C. or lower) is a silane coupling agent, forms an organic resin layer (B) containing the silane coupling agent, and forms Si (OR ₂ ) on the B layer.
₄ (R ₂ is an alkyl group having 4 or less carbon atoms) is represented by M (OR ₃ ) n (R ₃ is an alkyl group having 4 or less carbon atoms, and n is an integer of 3 to 5) Of the phosphoric acid ester represented by the metal alkoxide or PO (OR ₄ ) ₃ (R ₄ is an alkyl group having a carbon number of 4 or less) to which at least one kind is added, and a co-hydrolysis solution is applied,
A thin film (D) having transparent conductivity is laminated on at least one surface of a laminate having an inorganic cured layer (C) formed by heating at 120 ° C. or higher and under the glass transition temperature of a plastic film substrate. It is a transparent conductive film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a substantially amorphous plastic resin having a glass transition temperature of 120 ° C. or higher,
Examples thereof include polycarbonate, polyarylate, polysulfone, polyether sulfone, cyclic polyolefin and the like. Among these, polycarbonate, polyarylate, polysulfone, and polyethersulfone are preferable in terms of adhesion to the organic resin layer (B), and the higher the glass transition temperature, the higher the temperature at which the inorganic cured layer (C) is formed. It is possible and advantageous, and polyether sulfone is most preferable. To obtain a film of these resins, a melt extrusion film forming method, a solvent casting method and the like are possible, but the solvent casting method is advantageous for filtering foreign matters and reducing the retardation, but the productivity is low, There is a problem that the solvent remains,
In particular, the thick film has a large problem of residual solvent, and melt extrusion film formation is preferable. It is said that it is difficult to reduce the retardation in the melt extrusion film forming method, but it is possible by precisely controlling the film forming conditions. Retardation is a transmission distance of two polarizations while passing through a film when light traveling in a substance having polarizability such as a polymer is divided into two polarizations orthogonal to each other. It represents the degree of deviation and has the effect of eliminating polarization. Most liquid crystal display devices use polarized light, and it is desirable that there be no retardation at all as a material, but practically 1
When the thickness is 5 nm or less, the deterioration of display quality is not detected.

Next, the plastic film substrate (A)
Of the at least one surface, a substance having a functional group -OR ₁ represented by (the boiling point at normal pressure of the compound represented by H-OR ₁ is an alcohol residue to be 120 ° C. or less) Shiranka
An organic resin layer (B) , which is a pulling agent, is formed in order to improve the adhesion between the plastic film substrate (A) and the inorganic cured layer (C). As a substance having a compound residue having a boiling point of the compound represented by H-OR ₁ at atmospheric pressure of 120 ° C. or lower, —OCH ₃ , —OC ₂
Examples thereof include alcohol residues such as H ₅ . Boiling point is 1 at normal pressure
It is important that the temperature is 20 ° C. or lower because no reaction desorption substance remains in the step of heating to 120 ° C. or higher for forming the inorganic cured layer (C). In particular, it is preferable to use a silane coupling agent that is easily available and has excellent solubility in an organic resin or a solvent for using it as a coating liquid. As the silane coupling agent, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ
-Aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane and the like can be mentioned.

Next, Si (O) is formed on the organic resin layer (B).
A tetraalkoxysilane represented by R ₂ ) ₄ (R ₂ is an alkyl group having 4 or less carbon atoms) and M (OR ₃ ) n (M is a metal element,
R ₃ is an alkyl group having 4 or less carbon atoms, n is an integer of 3 to 5) or a metal alkoxide represented by PO (OR ₄ ).
₃ (R ₄ is an alkyl group having 4 or less carbon atoms), a co-hydrolysis solution of at least one of the phosphoric acid esters added is applied, and the glass transition temperature of the plastic film substrate at 120 ° C. or higher is applied. The inorganic cured layer (C) obtained by heating under the following conditions is formed. When the organic resin layer (B) is formed on both sides, the inorganic cured layer (C) may be formed on only one side or both sides. M (O
The metal alkoxide represented by R ₃ ) n (M is a metal element, R ₃ is an alkyl group having 4 or less carbon atoms, and n is an integer of 3 to 5) is a group 3A, 4A, 5A or 4B of the periodic table. Tribe or 5B
A metal alkoxide made of any metal element of the group, for example, Ti, Al, Zr or the like. Inorganic cured layers having sufficient gas barrier properties cannot be obtained with metal elements other than the above. The method for hydrolyzing a tetraalkoxysilane represented by Si (OR ₂ ) ₄ (R ₂ is an alkyl group having 4 or less carbon atoms) is already well known. For example, Sakuhana Sakuo, "Science of Sol-Gel Method" ( Agne Seofusha) etc. can be referred to. It is also known to apply a hydrolyzate or a polycondensate thereof to form an inorganic film. However, the inorganic cured layer (C) having the desired gas barrier properties, flexibility, and adhesiveness without impairing the properties required of the transparent conductive film for plastic film liquid crystal display device is achieved for the first time by the present invention. . First, depending on the application of a simple hydrolyzate, the film may curl or the inorganic film may be cracked due to the volume contraction caused by heat mineralization. Therefore, the coating solution must have undergone polycondensation in advance. Next, R ₂ of the tetraalkoxysilane must be an alkyl group having 4 or less carbon atoms. This is important because the alcohol generated by the elimination reaction is in a gas state at a temperature of 120 ° C. or higher which is a heating condition for mineralization. If it is a liquid or a solid, a serious obstacle occurs in the gas barrier property and the adhesiveness required for the inorganic film.

Finally, a thin film (D) having transparent conductivity is laminated on at least one surface of the laminate having the inorganic cured layer (C) formed thereon. Usually, the transparent conductive thin film (D) is formed on the inorganic cured layer (C). As the thin film having transparent conductivity, oxides of indium, tin, antimony, zinc, cadmium and the like, composites thereof, metals such as gold, silver and palladium are known and are not particularly limited. For liquid crystal display elements, indium tin oxide (I
TO) is used. The method for laminating a thin film having transparent conductivity is vapor deposition, sputtering, ion plating,
Examples of the method include plasma CVD and the like. Sputtering is usually used when laminating ITO thin films.

Before forming the transparent conductive thin film (D) on the inorganic hardened layer (C), an undercoat treatment is performed on the inorganic hardened layer (C) in order to improve the adhesion with the thin film (D). That is also effective. In particular, it is preferable to apply the UV-curable acrylate resin-cured layer (E) containing a silane coupling agent, because the adhesiveness with the thin film (D) and the inorganic cured layer (C) are excellent.

[0012]

【Example】

<< Example 1 >> Epoxy acrylate 15 parts, urethane acrylate 10 parts, polyester on both surfaces of a polyether sulfone film (Sumilite FS-5300 manufactured by Sumitomo Bakelite Co., Ltd., glass transition temperature 223 ° C., thickness 100 μm, retardation 10 nm) An organic resin layer obtained by applying a coating solution obtained by mixing 10 parts of acrylate, 2 parts of γ-methacryloxypropyltrimethoxysilane, 1 part of a UV crosslinking initiator, and 65 parts of a solvent with a gravure coater to a dry thickness of 3 μm and curing the same. Was formed. On top of that, 187 g of tetraethoxysilane, 23 g of titanium tetraethoxide (the molar ratio of tetraethoxysilane and titanium tetraethoxide is 90:10) and 120 g of isopropyl alcohol were mixed and stirred at 40 ° C. for 12 hours, and isopropyl alcohol 1 Add 0.7 kg to make a coating solution, and use a reverse coater to obtain a dry coating thickness of 0.1.
It was applied so as to have a thickness of .mu.m, and it was heated into an inorganic film by heating in a hot air drying oven at 180.degree. When the oxygen gas permeation coefficient was measured by the oxytran method at the stage of forming this inorganic cured film, it was 0.6 c at a humidity of 0%.
0.7 at c / m ² · day · atm and 95% humidity
cc / m ² · day · atm and the film before coating is 200 cc / m ² · day · even at 0% humidity.
Although it was atm, it was much improved. further,
On the surface of this inorganic cured film, the same coating solution as that applied to the polyether sulfone film in the first step was applied by a reverse coater to a dry thickness of 3 μm and cured to form a UV curable acrylate resin cured layer. Formed. Next, ITO is applied on the UV-curable acrylate resin cured layer by sputtering to have a surface resistance of 100.
Ω / □, the light transmittance was 80%. Using the transparent conductive film thus obtained, a plastic film liquid crystal display device was prepared, and stored at 80 ° C. high temperature and 60 ° C. 95% RH high temperature and high humidity.
No bubbles were observed in the liquid crystal display element even after 000 hours had elapsed. This indicates that the gas barrier property of the inorganic cured film was not impaired by the treatment of heat, chemicals, bending, rubbing, etc. in the plastic film liquid crystal display element production process. Also, the surfaces from which the ITO had been removed by etching were bonded with an epoxy resin and a peel test was conducted, showing a peel strength of 500 g / cm,
The release surface was an epoxy resin adhesive surface. The oxygen gas permeability coefficient is measured according to JIS K-7126, Method B (isobaric method).

<< Examples 2 to 5 >> The molar ratios of tetraethoxysilane and titanium tetraethoxide in Example 1 were 25:75 (Example 2), 50:50 (Example 3), and 75:25, respectively. A liquid crystal display device was produced in the same manner as in Example 4 except that the ratio was 90:10 (Example 5). Table 1 shows the oxygen gas permeation coefficient at the stage of forming the inorganic cured film.

Example 6 A liquid crystal display device was prepared in the same manner as in Example 1 except that the titanium tetraethoxide mixed in the inorganic cured layer was changed to aluminum ethoxide. Table 1 shows the oxygen gas permeation coefficient at the stage of forming the inorganic cured film. Example 7 A liquid crystal display device was produced in the same manner as in Example 1, except that the titanium tetraethoxide mixed in the inorganic cured layer was changed to zirconium tetraethoxide.
Table 1 shows the oxygen gas permeation coefficient at the stage of forming the inorganic cured film.
It was shown to. Example 8 A liquid crystal display device was produced in the same manner as in Example 1 except that the titanium tetraethoxide mixed in the inorganic cured layer was changed to triethyl phosphate. Table 1 shows the oxygen gas permeation coefficient at the stage of forming the inorganic cured film.

Comparative Example 1 A comparative experiment was carried out without forming the inorganic cured layer of Example 1 and the UV-curable acrylate resin cured layer on the inorganic cured layer. 24 for storage test
Generation of bubbles was confirmed at 0 hours.

Comparative Example 2 A liquid crystal display device was prepared in the same manner as in Example 1 except that the organic resin layer on the polyether sulfone film was formed by a compounding recipe in which the silane coupling agent was removed from the UV curable acrylate resin. It was created.
As a result of a comparative test, it was confirmed that bubbles were generated at 480 hours in a high temperature and high humidity storage test of a plastic film liquid crystal display device. When this display element was examined, it was confirmed that peeling occurred at the seal resin portion. IT
When the peeling test was performed by bonding the surfaces from which O was removed by etching with an epoxy resin, there was only a peel strength of about 50 g / cm, and when the peeled surface was examined, it was UV cured on the inorganic cured layer and the polyether sulfone film. It was peeled off between the resin layers.

Comparative Example 3 When a polyvinyl alcohol layer was formed in place of the inorganic hardened layer in Example 1 and the oxygen gas permeation coefficient was measured, it was 0.3 cc / m ² · day · atm at 0% humidity. Showed good gas barrier properties, but 50 cc / m ² · at 95% humidity
It was confirmed that the gas barrier property was remarkably deteriorated under high humidity.

[0018]

[Table 1]

[0019]

According to the present invention, a transparent conductive film suitable for a plastic film liquid crystal display device and having a gas barrier property without temperature / humidity dependency was obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of an example of the present invention, which is an example in which an inorganic cured layer is provided on both surfaces of a plastic film substrate.

FIG. 3 is a sectional view of an embodiment of the present invention, in which U is formed on the inorganic cured layer.
This is an example in which a V-curable acrylate resin cured layer is provided.

FIG. 4 is a cross-sectional view of an embodiment of the present invention, showing U on the inorganic cured layer.
This is an example in which a V-curable acrylate resin cured layer is provided.

[Explanation of symbols]

1 ... Transparent conductive thin film (D) 2 ... Inorganic cured layer (C) 3 ... Organic resin layer (B) 4 ... Plastic film substrate (A) 5 ... UV curable acrylate resin cured layer (E)

Claims (4)

(57) [Claims] 1. A transparent plastic film substrate (A) which has a glass transition temperature of 120 ° C. or higher, is substantially amorphous, and has a retardation value at the film thickness of 15 nm or less. -OR ₁ (H-OR ₁
Boiling point at atmospheric pressure of a compound represented by the substance having a functional group represented by the alcohol residue) to be 120 ° C. or less
A tetraalkoxysilane which is a silane coupling agent, forms an organic resin layer (B) containing it, and is represented by Si (OR ₂ ) ₄ (R ₂ is an alkyl group having 4 or less carbon atoms) on the B layer. Is a metal alkoxide represented by M (OR ₃ ) n (M is a metal element, R ₃ is an alkyl group having 4 or less carbon atoms, n is an integer of 3 to 5) or PO (OR ₄ ) ₃ (R ₄ is Of the phosphoric acid ester represented by an alkyl group having 4 or less carbon atoms), at least one or more of them is applied with a co-hydrolysis solution,
A thin film (D) having transparent conductivity is laminated on at least one surface of a laminate having an inorganic cured layer (C) formed by heating at 120 ° C. or higher and under the glass transition temperature of a plastic film substrate. A transparent conductive film characterized by the above. 2. A transparent plastic film substrate (A)
Is polycarbonate, polyarylate, polysulfone,
The transparent conductive film according to claim 1, which is a melt-extruded film of a polyethersulfone resin. 3. A metal alkoxide represented by M (OR ₃ ) n (M is a metal element, R ₃ is an alkyl group having 4 or less carbon atoms, and n is an integer of 3 to 5) is a group 3A group of the periodic table, 4A family, 5A
Family, claim, characterized in that a metal alkoxide composed of any of metal elements 4B group or 5B group 1 or 2
The transparent conductive film described. 4. A laminate having an inorganic cured layer (C) formed,
UV containing a silane coupling agent on the inorganic cured layer (C)
The transparent conductive film according to claim 1, 2 or 3 , wherein a thin film (D) having transparent conductivity is laminated via a curable acrylate resin cured layer (E).