JPS6179644A - Transparent laminated conductive film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polymer film/L, A top c: si0, SiO2,
TiO2, 2ro2, Al2O3, Ta2O5, Nb2
O3, Ta205, Nb2o1, SnO2, CeO2
A layer of at least one kind of metal oxide selected from the group is provided, an organic layer made of polyvinyl alcohol resin is provided on the metal oxide layer, and a metal oxide layer is provided again on the organic layer.

The present invention relates to a transparent laminated conductive film in which a film containing indium oxide as a main component is formed as a conductive layer on one or both sides of the substrate film obtained in this manner.

As transparent conductors, those formed by forming tin oxide or indium oxide films on glass substrates have been known for some time, and today they are widely used in electrodes of various displays, transparent surface heating elements, and the like.

On the other hand, transparent conductive film replaces the conventional glass substrate with a polymer film, and has various advantages that glass substrates do not have, such as being thin, lightweight, unbreakable, flexible, easy to process, and can be made into large areas. It has the following characteristics and is particularly promising as an electrode material for liquid crystals.

The production of transparent conductor films began with polyester films, but since they are usually produced by the 2-pongee stretching method, they produced birefringence and could not be used as transparent electrodes in TN (twisted nematic) type liquid crystal display devices.

For this reason, an axially stretched polyester film is being considered as a transparent electrode for liquid crystal elements, but when using this, the axis of optical anisotropy must align with the axis of the polarizing plate used in liquid crystal elements, and the work very bad sex.

In addition, because it is -axially stretched, there is anisotropy in the shrinkage rate when heated, which impairs its performance as a transparent electrode both optically and in appearance.5 Other cellulose-based films are being considered, but It is difficult to use because it has no heat resistance and warps and deforms during the manufacturing process of liquid crystal display elements.

Therefore, as electrodes for liquid crystal display elements, although not particularly limited, it is necessary to use a film that has good transparency, is amorphous, and has heat resistance.

As a result of intensive research, we found that the birefringence is within 40 degrees in terms of phase difference, and the photoelastic constant is 2. Omm/kg
It has been found that a polymer film having a heat shrinkage rate of 5% or less at 200° C. is most suitable.

However, it has been found that significant deterioration and failure of the liquid crystal occur due to the diffusion of water vapor and air accompanying film formation, which did not occur with conventional glass substrates.

Furthermore, polymer films are generally easily scratched and require some kind of protective coating from the viewpoint of transparency in appearance.

As a result of careful consideration, we found that SiC, SiO□, T +
02, ZrO2, Al□03, Taz05, Nb2O3
, 5n02, and Ce02, at least one transparent metal oxide layer formed on both sides of an organic layer made of polyvinyl alcohol is provided on the base film to prevent water vapor and air from permeating, We have found a transparent laminated conductive film that can dramatically improve the lifespan of liquid crystals and also has properties as a protective coat for polymer films, which will be described in detail below.

First of all, when using a laminated conductive film for liquid crystals, the base film should have a birefringence index of 40 degrees or more, regardless of its thickness, although it is not particularly limited. No.

A TN type liquid crystal display element is normally used in a bright field, but if the film has a large birefringence, the background part becomes colored and the contrast of the character part becomes small.

Therefore, it is preferable that the base film, metal oxide, and organic material layers have no birefringence at all, but if variations in the production process are taken into consideration, the degree of birefringence should be determined regardless of the retardation regardless of the thickness. and found that 40 degrees is the limit ν1
I put it out.

This measurement is obtained by measuring the phase difference caused by the speed difference of light waves in the main axis direction of the base film provided with the metal oxide and organic layers using a phase difference meter.

The second condition is the photoelastic constant, which is a constant that represents the ease with which birefringence occurs when a force is applied to the film and the film is deformed.

In general, in liquid crystal cells using film electrodes, tension or compressive stress may be applied to the film electrodes when setting the film electrodes or gluing the film electrodes. If birefringence occurs, as described in the first condition, the contrast of the display will be reduced.

A more important point is that when film electrodes are used, curved liquid crystal display may be performed, and in this case considerable tension and compression forces are applied to the film. However, for the same reason, this is not preferable because it reduces the display contrast.

Therefore, the base film, metal oxide, and organic layer used in the film electrode are preferably made of materials that do not cause birefringence under stress as much as possible.

As a result of examining various transparent plastics, the photoelastic constant was 2. Omm/kg is the limit, and values below this are preferable.

In general, as a material with a small photoelastic constant, it is preferable that the Young's modulus is large, that is, it is difficult to cause distortion, and the composition does not contain molecules with a large polarizability.

The photoelastic constant is determined from the relationship between the stress applied to the base film provided with the film, metal oxide, and organic layer using a photoelastic device, and the resulting photoelastic tooth.

The third condition is the thermal properties of the base film.
First, when producing a transparent laminated conductive film, heat treatment is performed in the range of 100'C to 200'C to stabilize the metal oxide that is the conductive layer. Stress concentration occurs on the surface, causing wrinkles and cracks.

In addition, in the process of forming an electrode pattern, washing and drying processes are performed several times, but if the base film with the conductive metal oxide layer has a large thermal shrinkage rate, pattern accuracy may be impaired. This will interfere with subsequent processing.

Other equipment that incorporates a liquid crystal display may reach relatively high temperatures, and in such environments the electrode film may shrink or shrink.
It may become deformed and its function may be impaired.

For this reason, the film used for the liquid crystal electrode needs to be heat resistant, and preferably has a shrinkage rate of 5% or less at a minimum temperature of 200'C.

Fourthly, when used in liquid crystals or the like, it is necessary to prevent water vapor and air from permeating through the film.

Since commonly used Schiff base, azo, azoxy, biphenyl, and phenylcyclohexyl liquid crystals are susceptible to hydrolysis, water vapor permeation has a direct effect on their service life.

Particular attention should be paid to Schiff-based systems.

Furthermore, if air passes through the liquid crystal, air bubbles will be generated within the liquid crystal, causing a major problem.

Therefore, in order to turn a glass substrate into a polymer film, it is necessary to prevent the permeation of water vapor and air before it can be used for liquid crystal applications.

The best way to prevent this is to use a base film that can trap water vapor and air, but the most preferable conditions for use in liquid crystals, etc., are that the birefringence is within 40 degrees as a phase difference, and the photoelastic constant is 2. In order to satisfy the optical constant of .0 mJkg or less, it is necessary to use an amorphous polymer.

However, the permeability of water vapor and air through these amorphous polymer films is generally high, making it difficult to prevent liquid crystal deterioration.

Therefore, we conducted extensive studies on various metal oxide films and organic layers, and found that in the visible range, the transmittance was 85% or more, and the water vapor transmittance was 3 x 10'! ? /cm2・24Hr
-Atm or less, the air permeability is s x i o'"sc
By providing a metal oxide layer on both sides of the initial layer of organic material with a thickness of c/cm2・24Hr-atm or less, a standard that can be put to practical use in an environment of 80°C and 90% RH, which is a reliability test for liquid crystals. It has been found that the material can withstand use for 1,700 hours, greatly improving the performance.

These metal oxide layers include Si○, SiO2, T
lO2, ZrO2, Al□○1, Ta205, Nb2O
3. Using at least one member selected from the group of Ta2O5, Nb2O3, SnO2, and CeO2, the organic layer as a barrier is most preferably a polyvinyl alcohol resin with strong intermolecular force and high concentration of functional groups; We have found that this objective can be achieved by sandwiching an organic layer with an oxide layer.

The reason for combining a metal oxide and an organic material as a barrier layer is that metal oxides are ideal materials as they do not allow gas to pass through other than by diffusion, but metal oxides are generally used in combination with polymers. The film is formed by sputtering, vapor deposition, etc., which are vapor phase methods, but it is impossible to completely eliminate pinholes caused by fine particles in the equipment, dirt on the base film, stress during manufacturing, etc. It is impossible,
A single layer of metal oxide alone may not provide a sufficient barrier layer.

Next is the case where an organic material is provided as a single layer as an air barrier layer. Examples of organic materials suitable for this purpose include cellulose, polyacrylonitrile, polyvinylidene chloride, and polyamide resins. Most preferred is a polyvinyl alcohol resin that has a strong functional group concentration and a high functional group concentration.

However, since polyvinyl alcohol resin is hydrophilic, it cannot be firmly attached directly to polymer films, and under high humidity it adsorbs water and breaks hydrogen bonds, impairing the liquid-tightness of the structure. The air barrier properties deteriorate rapidly.

Furthermore, polyvinyl alcohol resin cannot be used alone because it is exposed to hydrochloric acid, which is an etching solution for conductive films.

Therefore, as a result of intensive studies to improve the above-mentioned drawbacks, we first firmly adhered polyvinyl alcohol resin, which has the best air barrier properties, to the polymer film that is the substrate. We believe that all of the above drawbacks can be solved by using a metal oxide that is excellent as a polyvinyl alcohol resin, which prevents deterioration under high humidity, and which is also resistant to hydrochloric acid by forming a metal oxide on the polyvinyl alcohol resin. This is what I discovered.

The thickness of these metal oxide layers is not particularly limited, but is 10
A range of 0 to 5OOOA is preferred.

If the thickness is less than 100λ, a continuous film is formed and it is difficult to achieve the desired prevention of permeation of water vapor and air.

Moreover, if the thickness exceeds 500^, cracks may occur in the oxide layer, which is not preferable.

The thickness of the organic material layer as a barrier layer is not particularly limited, but from a performance standpoint, if it is too thin, the expected performance as a barrier coat will not be achieved.
The above thickness is necessary. .

Moreover, if the thickness exceeds 20 μm, stress will be strong and problems such as curling will occur.

Furthermore, before forming a film containing indium oxide or the like as a main component as a conductive layer, an undercoat suitable for the polymer film may be provided on the polymer film for the purpose of improving scratch resistance.

As mentioned above, by using a transparent conductive film based on a polymer film instead of a conventional glass substrate, it is possible to create a new type of thin and flexible liquid crystal element, and it is also possible to create a new type of liquid crystal element that is thin and flexible. It is easy to handle, can be punched, and can dramatically improve productivity.

Furthermore, in terms of performance, since water vapor and air permeation from the film side is prevented, the service life is greatly improved, and the drawback of polymer films, which are easily scratched, is also improved.

The above description has mainly been about electrode materials for liquid crystals.
The transparent laminated conductive film, which has a coating mainly composed of indium oxide on the other side of the polymer film, can also be used in other applications by preventing the diffusion of water vapor and air from the film surface, and improving various electrical properties and reliability. It is possible to prevent deterioration in properties, etc., and is extremely useful like electrode materials for liquid crystals.

Hereinafter, it will be explained in more detail with reference to Examples.

A polyether sulfone film with a thickness of 100 μm was used as the base film of the example, and SiO□ was used as the metal oxide layer.
was formed to a thickness of 500A by sputtering, and then 5 μml of polyvinyl alcohol resin was added as an organic barrier layer.
Then, SiO□ was again formed to a thickness of 500λ by sputtering.

The birefringence of this film is 20 degrees, the photoelastic constant is 1.75 mm/kg, the water vapor permeability of this film is 3X10'g/cI112.24Hr-atm, and the air permeability is 5X10' 5cc/cI112・24H
r-atm, and the transmittance in the visible light region is 87%.
Met.

Also, the water vapor permeability of the base film as a comparative example is IX
10'g/am2・24Hr-atm1 and air permeability is 2 x 10'! cc/'Cl112・24Hr-a
It was tll.

Further, on the polyether sulfone film of the base film, S r 02 was coated to a thickness of 50 OA and polyvinyl alcohol resin was coated to a thickness of 5 μm by a sputtering method, and a thin film of S r 02 of 50 OA thick was further provided on top of this. A transparent laminated conductive film with a thickness of 250A provided with indium oxide by sputtering as a conductive layer on the base film side, and a conductive layer on the base film side of the film in which a Sio2 thin film, a polyvinyl alcohol resin, and a SiO2 thin film were provided on the base film. A transparent laminated conductive film having a thickness of 250 A was prepared by sputtering indium oxide.

On the other hand, as a comparative example, a transparent laminated conductive film was prepared in which a conductive layer was directly attached to a base film and indium oxide was applied to a thickness of 250λ by sputtering.

A cell for a liquid crystal display was prepared using the above three types of laminated conductive films, and a reliability test was conducted under an environment of 80° C. and 90% RH.

As a result, the cell made of the Sio2 thin film of the present invention, the polyvinyl alcohol resin, and the former two transparent laminated conductive films provided with the Sio2 thin film can be used for 1700 hours, which far exceeds the standard for practical use. Ta. On the other hand, a cell prepared in a comparative example in which the indium oxide thin film was directly attached to the base film became unusable after about 500 hours.

As shown in the examples above, the transparent laminated conductive film of the present invention is formed by providing a metal oxide layer and an organic layer that prevent water vapor and air from passing through, and is a transparent laminated conductive film that can dramatically improve the lifespan of liquid crystals. I understand that it is.

Claims (1)

[Claims] SiO, SiO_2, T on one side of a transparent polymer film
iC_2, ZrO_2, Al_2O_3, Ta_2O_
5. On top of a layer of at least one oxide selected from the group of Nb_2O_3, SnO_2, and CeO_2, an organic layer made of polyvinyl alcohol-based resin is provided, and the above metal oxide is further placed on the organic layer again. Provide layers. A transparent laminated conductive film in which a film containing indium oxide as a main component is formed as a conductive layer on one or both sides of the substrate film thus obtained.