JPS6132750A - 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 provides a method for depositing SiO, 5iOz, TiO on a polymer film.
2, ZrO2, Al2O3, Ta2O5, Nb2O3,
A layer of at least one metal oxide selected from the group of SnO2 and CeO2 is provided, an organic layer is provided as a second layer on the metal oxide layer, and a conductive layer is further provided on the organic layer as a third layer. The present invention relates to a laminated conductive film in which a film containing indium oxide as a main component is formed as a layer.

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 films replace conventional glass substrates with polymer films, and are thin, lightweight, unbreakable, flexible, easy to process, and can be made into large areas, which glass substrates do not have. It has various 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 using a biaxial stretching method, birefringence occurs, so they could only 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 match the pongee of the polarizing plate used in liquid crystal elements, and the work very bad sex.

Furthermore, since it is -axially stretched, there is anisotropy in the shrinkage rate when heated, which impairs the performance as a transparent electrode both optically and in appearance.

Other cellulose-based films are being considered, but they are difficult to use because they are not heat resistant and deform considerably 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 2.0 mm/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 occurs due to the diffusion of water vapor and air accompanying film formation, which did not occur with conventional glass substrates.

As a result of intensive study, we found that SiO, SiO2, TiO2
, ZrO2, A1.03, Ta2O5, Nb2O1, S
By providing a transparent metal oxide layer of at least one of n○2 and CeO2 on the base film, a laminated layer that prevents the transmission of water vapor and air and dramatically improves the lifespan of the liquid crystal. A conductive film has been found and will be described in detail below.

First of all, when using a laminated conductive film for a liquid crystal, the base film should not have a birefringence index of 40 degrees or more, regardless of thickness (although not particularly limited).

Normally, a TN type liquid crystal display element is used in a bright field, but if the birefringence of the film is extraordinary, the background part will be colored and the contrast of the character part will be reduced, resulting in the drawback of ν1.

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. We found that 40 degrees is the limit.

This measurement is obtained by measuring the phase difference caused by the speed difference of light waves in the main axis direction of a single film provided with 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 electrode when setting the film electrode or gluing the film electrode. If refraction occurs, the contrast of the display will be reduced, as described in the first condition.

An even more important point is that when film electrodes are used, liquid crystal displays may be displayed on a curved surface, and at this time considerable tension and compression forces are applied to the film, resulting in large complexities under stress. Materials that cause refraction are not preferred because they reduce display contrast for the same reason.

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 in this case, the photoelastic constant was found to have a limit of 2.0 mm/kg, and values below this value are preferred.

Generally, 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 an unusual polarizability.

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

The third condition is the thermal properties of the base film, metal oxide, and organic layer. First, when producing the transparent laminated conductive film, heating from 100°C to 2O to stabilize the metal oxide.
Heat treatment is performed in the range of 0°C, but if the shrinkage rate of the film is large, stress concentration occurs in the metal oxide film, causing wrinkles and cracks.

In addition, in the process of processing into electrode patterns, steps such as washing and drying are performed several times, but if the base film with an oxide layer has a large heat shrinkage rate, pattern accuracy will be impaired and subsequent processing will be delayed. cause trouble.

Other devices incorporating liquid crystal displays may reach relatively high temperatures, and in such environments the electrode film may shrink or deform, potentially impairing its functionality.

For these reasons, films and metal oxides used for liquid crystal electrodes1. The organic layer needs to have heat resistance, and preferably has a shrinkage rate of at least 5% at 200°C.

Fourth, when used for liquid crystals, etc., it is necessary to prevent water vapor and air from permeating from the film side.

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, bubbles will form inside 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.

Therefore, as a prevention method, it is possible 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 in terms of phase difference, and the photoelastic constant is 2. In order to satisfy the optical constant of Om+n/kg or less, it can only be achieved using 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 found that in the visible range, the transmittance is 85% or more, the water vapor permeability is 2 x 10"g/cm2・24Hr or less, and the air permeability is 4 x 1. (CC/c) By providing a metal oxide layer of 62.24 hours or less, a reliability test for liquid crystals of 1,300 hours in an environment of 80°C and 90% RH, which far exceeds the conventional standard. It has been found that it can withstand the use of

These metal oxide layers include SiO, SiO2, T
iO2, ZrO2, AI, 03, Ta=05, Nb2O
, , 51102, and by using at least one selected from the group of CeO2, the purpose can be achieved.

The thickness of these metal oxide layers is not particularly limited, but is 10
A range of 0 to 5000 A is preferred.

If the thickness is less than xooX, a continuous film will not be formed and it will be difficult to achieve the desired prevention of permeation of water vapor and air.

Moreover, if the thickness exceeds 5000 Å, cracks may occur in the oxide layer, which is not preferable.

If a conductive film containing indium oxide as a main component is formed directly on a metal oxide layer as a water vapor or air barrier, the adhesion between the two metal oxide layers will be insufficient, resulting in poor scratch resistance and It turned out that it lacked flexibility.

Therefore, when forming a film containing indium oxide, which is a conductive film, as a main component, providing a thin layer of organic material serves as a cushioning material between the metal oxide layers and also protects the metal oxide layer, which is a barrier layer. It has been found that the above-mentioned drawbacks can be compensated for.

The organic layer is not particularly limited as long as it satisfies the above-mentioned conditions, but from a performance standpoint, if it is too thin, the stress relaxation of the metal oxide layer cannot be measured, so a thickness of 0.5 μm or more is required.

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, but the laminated conductive film, which has a specific metal oxide layer on a polymer film, an organic layer, and a coating mainly made of indium oxide on top of that, is a In other applications, it can prevent the diffusion of water vapor and air from the film surface, and can prevent deterioration of various electrical properties, reliability, etc., and is extremely useful as an electrode material for liquid crystals.

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

As the base film of the example, a polyether sulfone film with a thickness of 100 μm was used, and a 5in2 film was formed by sputtering to a thickness of 50X as the first barrier layer of metal oxide, and an acrylic layer was further formed as the second organic layer. The resin was coated with a thickness of 5 μm.

Next, as a third conductive layer, indium oxide was deposited on the acrylic resin layer to a thickness of 250 Å by the same sputtering method to create a laminated conductive film.

In this case, the birefringence of the base film provided with the metal oxide and organic layers was 20 degrees, and the photoelastic constant was 1.75n+
m/kg, and the shrinkage rate at 200°C was 1.0%.

Furthermore, the water vapor permeability of the film provided with metal oxide and organic layers is 2 x 10g7cm2・24Hr, the air permeability is 4×10@cc/am2・24)1r, and the transmission rate in the visible light region is The rate was 87%.

As a comparative example, a laminated conductive film was prepared by directly applying indium oxide to a thickness of 25 OA on the same base film using the same method.

In addition, the water vapor permeability of the base film at this time is 1 × 10
-2g/crn2・2411r, and air permeability is 2×1
O-2cc/c "112.241Ir.

For liquid crystal displays using the above two types of laminated conductive films
A cell was prepared and a reliability test was conducted in an environment of 80° C. and 90% RH.

As a result, in a cell equipped with SiO2, which is a metal oxide,
It was possible to use it for 1,300 hours, far exceeding the conventional standard.

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, it can be seen that the laminated conductive film can dramatically improve the life of the liquid crystal by providing a metal oxide layer that prevents water vapor and air from passing through.

Claims (1)

[Claims] Metal oxides SiO, SiO_2, TiO_2, Zr as the first layer on one or both sides of the polymer film.
O_2, Al_2O_3, Ta_2O_5, Nb_2O
_3, SnO_2, and CeO_2, providing at least one metal oxide layer selected from the group, and further providing an organic layer as a second layer on at least one side of the metal oxide layer,
Further, as a third layer, a laminated conductive film is provided, in which a film containing indium oxide as a main component is formed as a conductive layer on the organic layer.