JPH09166778A - Phase difference integration type transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the return of the retardation by a heat treatment and to obviate the occurrence of the float and crack of transparent conductive films by forming the specific transparent conductive films on at least one surface of a phase difference film having a specific glass transition temp. SOLUTION: The transparent conductive films having sheet resistance of >=200Ω/square are formed on at least one surface of the phase difference film having >=160 deg.C glass transition temp. Polyacrylate among high heat resistant resins is more preferable as this resin has the high glass transition temp. and the phase difference film obtd. therefrom adheres well to the transparent conductive films without subjecting the film to a special surface treatment. The high glass transition temp. of the phase difference film is >=160 deg.C and, therefore, there is no possibility that the return of the retardation increases even if the heat treatment in the production process of liquid crystal panels and the heat treatment, such as drying of a solvent and curing treatment at the time of executing the surface treatment in order to improve alkali resistance are executed for 1 to 2 hours usually at 120 to 150 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a retardation-integrated transparent conductive film. More specifically, it relates to a retardation-integrated transparent conductive film which can be suitably used as a compensation film for a liquid crystal display device incorporating a touch panel, for example.

[0002]

2. Description of the Related Art In recent years, as a display device, lightweight,
Moreover, liquid crystal displays, which are characterized by being compact, are widely used, and in particular, they are indispensable as display devices for mobile information terminals and mobile phones.

Liquid crystal displays include a simple matrix system and an active matrix system, depending on the driving system. Recently, in terms of image quality and response speed, TF
While the active matrix method based on the T method is becoming mainstream, on the other hand, for small liquid crystal displays, the STN method of the simple matrix method is often adopted from the viewpoint of cost and power consumption. In the STN method, the birefringence of the liquid crystal is used, so that there is a drawback that it is colored, but by incorporating a retardation film, it has become possible to obtain a black and white mode.

Further, a touch panel for pen input is generally incorporated in a small liquid crystal panel of a portable information terminal. Conventionally, as such a touch panel, a touch panel made of a transparent conductive polyethylene terephthalate film is generally used. A transparent conductive film used for such a touch panel generally has a sheet resistance of 200.
Ω / □ or more.

By the way, in recent years, in order to reduce the number of parts and simplify assembly, a retardation-integrated transparent conductive film in which a transparent conductive film is formed as an electrode of the touch panel on the retardation film is used in the touch panel. Discussions are underway. However, the conventional polyethylene terephthalate film cannot be used as a retardation film for such a retardation-integrated transparent conductive film because of its birefringence.

Therefore, it has been attempted to use a polycarbonate film obtained by polymerizing bisphenol A as a monomer component instead of the polyethylene terephthalate film as a retardation film. However, only by forming a transparent conductive film used as an electrode of a touch panel on such a polycarbonate film, a large retardation return occurs during heat treatment in the manufacturing process of the liquid crystal panel in which the touch panel is integrated ( It has been found that there is a problem in that the retardation value becomes extremely small) and the ability of the liquid crystal to compensate for the retardation is impaired, that is, the retardation film does not function.

Further, in the manufacturing process of the liquid crystal panel, an alkali treatment is usually performed. However, the alkali treatment easily causes film floating or cracks on the transparent conductive film. May occur and deteriorate the function of the device. In order to suppress the occurrence of such film floating and cracks, the retardation film may be preliminarily subjected to a base treatment, but since the polycarbonate film does not have a sufficiently high heat resistant temperature, the heating temperature at the time of performing the base treatment is high. However, there is a problem that the film thickness and cracks due to alkali treatment cannot be sufficiently suppressed.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and since it has excellent heat resistance, the retardation return due to heat treatment is small and the film floating of the transparent conductive film is small. An object of the present invention is to provide a retardation-integrated transparent conductive film in which cracks and cracks do not occur.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a retardation-integrated transparent film in which a transparent conductive film having a sheet resistance of 200Ω / □ or more is formed on at least one surface of a retardation film having a glass transition temperature of 160 ° C. or more. The present invention relates to a conductive film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The retardation-integrated transparent conductive film of the present invention has a glass transition temperature of 160 as described above.
A transparent conductive film having a sheet resistance of 200 Ω / □ or more is formed on at least one surface of a retardation film having a temperature of not less than ° C.

In the present specification, the retardation means the phase difference between normal light and extraordinary light emitted from the birefringent body when linearly polarized light is incident on the birefringent body, and the retardation value is the retardation value. , The value of the phase difference.

Since the retardation film used in the present invention has a specific high glass transition temperature, the obtained retardation-integrated transparent conductive film has excellent heat resistance and a small retardation return. Becomes

The glass transition temperature of the retardation film is
The heat treatment in the manufacturing process of the liquid crystal panel and the heat treatment such as the drying and curing treatment of the solvent at the time of performing the base treatment for improving the alkali resistance are usually performed at 120 to 150 ° C for about 1 to 2 hours. In consideration of the above, in order to eliminate the risk of the retardation returning becoming large, 16
The temperature is 0 ° C. or higher, and in order to more sufficiently improve the heat resistance of the obtained retardation-integrated transparent conductive film, 1
It is preferably 80 ° C. or higher. In consideration of the fact that the film can be stretched relatively easily, the glass transition temperature of the retardation film is usually preferably about 280 ° C. or lower.

Examples of the retardation film having a glass transition temperature of 160 ° C. or higher include a resin film having a glass transition temperature of 160 ° C. or higher.

Examples of the resin having a glass transition temperature of 160 ° C. or higher include polyarylate (glass transition temperature:
190 ° C or higher), polyethersulfone (glass transition temperature: 230 ° C), polysulfone (glass transition temperature: 19)
0 ° C), heat resistant polycarbonate (glass transition temperature: 1
85 ° C.) and other high heat-resistant resins called thermoplastic engineering plastics, and these can be used alone or in admixture of two or more, but the present invention is limited to these examples only. Not a thing.

Among the above high heat resistant resins, polyarylate is preferable because it has a high glass transition temperature and the retardation film obtained therefrom can be well adhered to the transparent conductive film without any special pretreatment. Especially preferred.

The polyarylate used in the present invention is not particularly limited, but it is obtained by polycondensing terephthalic acid and / or isophthalic acid and a divalent phenol from the viewpoint of easy availability of raw materials. Those are preferable.

Specific examples of the dihydric phenol include:
For example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 4,4'-
(Α-methylbenzylidene) bisphenol, bis (4
-Hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 4,4-bis (4-hydroxyphenyl) heptane, 4,4-bis (4-hydroxyphenyl) 2,5-dimethylheptane, bis (4-hydroxyphenyl) methylphenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 2,2-bis (4-hydroxyphenyl) octane, bis (4- Hydroxyphenyl) -4-fluorophenylmethane, bis (3,5-dimethyl-4-hydroxyphenyl) methane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, bis (3,5- Dimethyl-4-hydroxyphenyl) phenylethane, bis (3-methyl-4-hydroxyphene) Le) diphenylmethane, bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -3,
Examples thereof include 3,5-trimethylcyclohexane and the like, and these can be used alone or in combination of two or more, but the present invention is not limited to these examples.

The polyether sulfone is, for example, a polycondensate of 4,4'-dihydroxydiphenyl sulfone, and the polysulfone is, for example, a polycondensate of bisphenol A and 4,4'-dihydroxydiphenyl sulfone. Examples of the heat-resistant polycarbonate include cyclohexylidene-based bisphenol polycondensates.

There is no particular limitation on the method for forming a resin such as the above-mentioned high heat resistant resin into a film. For example, the resin may be extruded using an ordinary extruder, or the resin may be dissolved in a solvent. A method of casting a solution can be mentioned. Among these methods, the thickness of the obtained film is more uniform, has excellent surface properties, and when performing a stretching treatment for imparting a desired retardation to the film as described below, stretching unevenness occurs. The casting method is more preferable because it is difficult.

The thickness of the film thus obtained is not particularly limited, but in consideration of the use of the finally obtained retardation-integrated transparent conductive film, it is usually 10 to 200 μm.
m, preferably 40 to 100 μm.

Since the retardation film used in the present invention has a specific high glass transition temperature as described above, the obtained retardation integrated transparent conductive film is, for example, a liquid crystal in which a touch panel is incorporated. It is extremely practical as a compensation film for display devices.

The retardation value of the retardation film is usually about 100 to 8000 nm.

In order for the retardation film to exhibit the retardation value described above, for example, the resin film may be stretched.

The method for carrying out the stretching treatment is not particularly limited, and examples thereof include a lateral uniaxial stretching method and a longitudinal uniaxial stretching method. Considering that a stretched film having higher uniaxiality can be obtained, the longitudinal uniaxial stretching method is used. preferable.

The temperature for the stretching treatment may be determined as an optimum temperature based on the glass transition temperature of the resin used as the raw material for the retardation film, but considering that stretching unevenness does not occur. , A temperature about 20 ° C. lower than the glass transition temperature of a normal resin to 30 lower than the glass transition temperature.
It is preferable to set the temperature as high as about ° C.

By forming a transparent conductive film on at least one surface of the retardation film obtained as described above, the retardation integrated transparent conductive film of the present invention can be obtained.

The transparent conductive film formed on one side or both sides of the retardation film includes, for example, a metal such as gold or silver;
Indium oxide, tin oxide, indium tin oxide (I
Although a metal oxide such as TO) can be used,
Considering conductivity, transparency, and easiness of patterning, it is particularly preferable to use a metal oxide containing indium oxide as a main component.

The method for forming the transparent conductive film is not particularly limited and, for example, a vacuum vapor deposition method, a sputtering method, an ion plating method or the like can be adopted.
Considering the adhesion of the transparent conductive film to the retardation film, the sputtering method and the ion plating method are preferable, and the sputtering method is particularly preferable.

In the present invention, an oxide target made of indium oxide and tin oxide is used to form a transparent conductive film by DC magnetron sputtering in a mixed gas atmosphere of argon gas and oxygen gas. Is particularly preferable from the viewpoint of productivity.

The sheet resistance of the transparent conductive film thus formed is 200 Ω / □ or more, considering that it is used as an electrode of a touch panel, but it is 400 Ω / □ or more in view of the position detection accuracy of the touch panel. preferable. The sheet resistance of the transparent conductive film is usually 2000Ω / □ or less.

The thickness of the transparent conductive film is not particularly limited, but in consideration of the light transmittance, it is usually 10 to 80 n.
m, preferably 15 to 40 nm.

The light transmittance (wavelength 550 nm) of the retardation-integrated transparent conductive film in which the transparent conductive film is formed on at least one surface of the retardation film as described above is 75 when the light transmittance of the entire liquid crystal panel is taken into consideration. % Or more, preferably 80% or more.

In the manufacturing process of a liquid crystal panel, for example, it is general that an alkali treatment is performed in the process of forming a pattern of a transparent conductive film. When the retardation film on which the transparent conductive film is formed as the alkali treatment is dipped in an alkaline solution, in order to eliminate the possibility of film floating or cracks of the transparent conductive film, a base treatment is usually performed. In the invention, when a film made of polyarylate is used as the retardation film, film floating or cracking of the transparent conductive film occurs even if the transparent conductive film is directly formed on the film made of such polyarylate. There is no fear and there is an advantage that such a base treatment is unnecessary.

Further, as described above, the undercoating treatment is carried out for the purpose of further improving the adhesion between the retardation film and the transparent conductive film and suppressing the occurrence of film floating and cracks. When a film made of a resin having a low transition temperature is used as a retardation film, it is not possible to increase the temperature of heat treatment such as solvent drying or curing treatment when the base treatment is performed, and the base treatment is sufficiently performed. There are times when you cannot do it. However, in the present invention, since a retardation film having a high glass transition temperature of 160 ° C. or higher is used, it is more effective to set the temperature of the heat treatment at the time of performing the base treatment sufficiently high. The treatment can be performed, the adhesion between the retardation film and the transparent conductive film is sufficiently improved, and the floating of the transparent conductive film and the generation of cracks are advantageous.

As described above, since the retardation-integrated transparent conductive film of the present invention has excellent heat resistance, the retardation returned by the heat treatment is small, and the transparent conductive film does not crack. Therefore, it can be suitably used, for example, as a compensating film for a liquid crystal display device incorporating a touch panel.

[0037]

EXAMPLES Next, the retardation integrated transparent conductive film of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Glass transition temperature is 215 ° C. and retardation value is 40.
0 nm, thickness of 58 μm polyarylate retardation film (bisphenol A, bis (3,5-dimethyl-4-
(Hydroxyphenyl) methane, isophthalic acid and terephthalic acid polycondensation film, manufactured by Kanegafuchi Chemical Co., Ltd.
90% by weight of indium oxide (In ₂ O ₃ ) and stannic oxide (Sn) were formed on one side of Ermec F-1100.
O ₂ ) Oxide target of 10 wt% was used in a mixed gas of argon gas and oxygen gas (argon gas: oxygen gas (volume ratio) = 99: 1) in a DC magnetron sputtering device (Co., Ltd.). Shimadzu HS
M-720) was used to form a transparent conductive film having a thickness of 30 nm to produce a retardation integrated transparent conductive film.

Using the thus obtained retardation-integrated transparent conductive film, the sheet resistance, light transmittance, retardation value after heat treatment and alkali resistance were examined according to the following methods. Table 1 shows the results.

(A) Sheet resistance The sheet resistance (Ω / □) of the transparent conductive film formed on one side of the retardation film was measured using a resistivity meter (Loresta AP manufactured by Mitsubishi Petrochemical Co., Ltd.). .

(B) Light transmittance Self-recording spectrophotometer (UV-310, manufactured by Shimadzu Corporation)
0) was used to measure the transmittance (%) of light having a wavelength of 550 m.

(C) Retardation value after heat treatment After the heat treatment was applied to the phase-integrated transparent conductive film at 150 ° C. for 1 hour, an automatic birefringence meter (KOBRA-21C manufactured by KS Systems Co., Ltd.) was used. ) Was used to measure the retardation value (nm).

(D) Alkali resistance The retardation-integrated transparent conductive film was immersed in a 2.5% sodium hydroxide aqueous solution heated to 40 ° C. for 5 minutes, washed with running water, and then the transparent conductive film was formed by an optical microscope. It was observed whether the film floated and cracked. Table 1
In the table, ◯ means that neither film floating nor cracking was observed, and x means that film floating or cracking was slightly observed.

Example 2 Example 1 was repeated except that a transparent conductive film having a thickness of 15 nm was formed on one side of the polyarylate retardation film instead of forming a transparent conductive film having a thickness of 30 nm. In the same manner, a retardation integrated transparent conductive film was manufactured.

The characteristics of the obtained retardation-integrated transparent conductive film were examined in the same manner as in Example 1. Table 1 shows the results.
Shown in

Comparative Example 1 In Example 1, instead of the polyarylate retardation film, a polycarbonate retardation film having a glass transition temperature of 150 ° C., a retardation value of 380 nm and a thickness of 55 μm (polymerized with bisphenol A as a monomer component). Except that the polymer film obtained by
A retardation-integrated transparent conductive film was produced in the same manner as in Example 1.

The characteristics of the obtained retardation-integrated transparent conductive film were examined in the same manner as in Example 1. Table 1 shows the results.
Shown in

In Table 1, the retardation value of the retardation film (measured by the same device as used for measuring the retardation value after the heat treatment (c)) and the formed transparent conductive film are shown. The thickness is also shown.

[0049]

[Table 1]

From the results shown in Table 1, the positions of Examples 1 and 2 in which a transparent conductive film having a sheet resistance of 200 Ω / □ or more was formed on a polyarylate retardation film having a glass transition temperature of 160 ° C. or more. Unlike the retardation-integrated transparent conductive film in which the transparent conductive film is formed on the polycarbonate retardation film having a low glass transition temperature of 150 ° C., the retardation-integrated transparent conductive film is heat-treated at 150 ° C. for 1 hour. It can be seen that even if it is applied, the retardation value hardly changes, and the floating and cracking of the transparent conductive film does not occur at all, which is excellent in alkali resistance.

[0051]

EFFECT OF THE INVENTION Since the retardation-integrated transparent conductive film of the present invention is excellent in heat resistance, retardation return due to heat treatment is small, and film floating or cracking of the transparent conductive film does not occur. is there. Therefore, the retardation-integrated transparent conductive film of the present invention can be suitably used as, for example, a compensating film for a liquid crystal display device incorporating a touch panel.

Further, the retardation-integrated transparent conductive film, in which the film made of polyarylate is used as the retardation film, has an effect of excellent alkali resistance.

Claims (2)

[Claims] 1. A sheet resistance of 200 on at least one surface of a retardation film having a glass transition temperature of 160 ° C. or higher.
A retardation integrated transparent conductive film having a transparent conductive film of Ω / □ or more. 2. The retardation integrated transparent conductive film according to claim 1, wherein the retardation film is a film made of polyarylate.