JPH05323101A - Electromagnetic wave shielding film having antireflection property and its production - Google Patents

Abstract

PURPOSE:To provide an electromagnetic waves shielding film excellent in antireflection property and to provide the production method of this film. CONSTITUTION:The electromagnetic waves shielding film having antireflecting property is obtd. by forming a transparent inorg. conductive layer on the surface of a transparent synthetic resin film and further forming a layer having lower refractive index than that of the conductive layer. Moreover, the surface of the transparent inorg. conductive film formed on a transparent synthetic resin film is exposed to low temp. plasma, and then a layer having lower refractive index than that of the conductive layer is formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shield film in which a conductive layer is prevented from reflecting light rays, and a method for producing the same.

[0002]

2. Description of the Related Art Cathode ray tubes (hereinafter C) used in various OA displays such as computers and word processors and home televisions.
It has been pointed out that a large amount of harmful electromagnetic waves are generated from RT (abbreviated as RT), and that health hazards to the operator due to these devices are impaired.

Various proposals have heretofore been made to prevent the above-mentioned obstacles. For example, a conductive metal mesh itself is stuck on the entire surface of the display, or a laminated plate in which the conductive metal mesh is sandwiched between glass and a transparent plastic plate is displayed on the entire display. I was wearing it on the. However, in these methods, since the conductive mesh is used, there is a problem that it is difficult for the operator to see the characters displayed on the display. In order to solve this problem, a method of using a mixed film of indium oxide and tin oxide (hereinafter referred to as an ITO film), which is known for transmitting visible light and excellent in conductivity and effectively shielding electromagnetic waves, as a conductive layer is considered. Be done. However, when a polyethylene terephthalate film provided with an ITO film which is commercially available and widely used is used, the ITO film has a higher refractive index and a larger light reflectance than the polyethylene terephthalate film. There is a problem that it cannot be used in applications such as the front plate of various OA displays where the reflection of the background is disliked.

Therefore, an object of the present invention is to provide an electromagnetic wave shielding film excellent in antireflection property and a method for producing the film.

[0005]

According to the present invention, the above object is achieved by providing a transparent inorganic conductive layer on the surface of a transparent synthetic resin film, and further providing a layer having a refractive index lower than that of the conductive layer on the surface layer thereof. After exposing the surface of the transparent electromagnetic conductive layer provided on the electromagnetic wave shielding film and the transparent synthetic resin film having the prevention property to low temperature plasma, a layer having a lower refractive index than the conductive layer is formed on the surface of the transparent inorganic conductive layer. This is achieved by a method for producing an electromagnetic wave shielding film having antireflection property.

The transparent synthetic resin film used in the present invention may be any one as long as a transparent conductive layer can be formed on this surface layer with good adhesion, but it has a mechanical strength suitable for roll treatment. A polyethylene terephthalate (hereinafter abbreviated as PET) film, which is available at a relatively low cost, is most preferable. Although the thickness of the transparent synthetic resin film is not particularly limited, it is usually 6 μm to 35 μm.
It is 0 μm, preferably 25 μm to 150 μm, and most preferably 50 μm to 125 μm.

In the present invention, the transparent inorganic conductive layer provided on the surface of the transparent synthetic resin film may be any inorganic material that is substantially transparent to visible light and has no turbidity. In ₂ O from the viewpoint of the mechanical properties and mechanical strength
_{A layer made of 3} (indium oxide), SnO ₂ (tin oxide), or a mixture of In ₂ O ₃ and SnO ₂ (hereinafter referred to as ITO) is preferable, and a layer made of ITO is most preferable. The film thickness of the conductive layer is not particularly limited as long as it can exhibit the performance of the present invention, but is usually 500 Å to 5000 Å, 70 from the viewpoint of film adhesion and transparency.
0Å to 2000Å is preferable. The layer made of ITO can be generally formed by a sputtering method or an ion plating method in oxygen plasma.

The layer having a refractive index lower than that of the conductive layer used in the present invention is not particularly limited.
From inorganic dielectrics such as SiO ₂ (silicon dioxide), MgF ₂ (magnesium fluoride), Al ₂ O ₃ (aluminum oxide), organic polysiloxane polycondensation films, organic coating films such as crosslinked films of methacrylic acid ester compounds It is a layer. Among these, a layer made of SiO ₂ is most preferable in terms of antireflection performance and mechanical strength such as scratch resistance. The film thickness of the low refractive index layer is not particularly limited as long as it can prevent reflection of visible light, but the optical film thickness in the visible light region (geometric film thickness × refractive index of film) is λ / A film thickness of 4 is most preferable (where λ is the wavelength of the light beam (n
m)). Examples of the method for forming the layer made of an inorganic dielectric include a sputtering method, an ion plating method, and a vacuum vapor deposition method. An inorganic dielectric layer formed by these methods has sufficient adhesion to the ITO film. However, the inorganic dielectric layer may be peeled off or scratched from the ITO film depending on the usage conditions. In terms of film strength, the inorganic dielectric layer is formed on the surface of the transparent inorganic conductive layer. It is more preferable to perform a treatment of exposing the surface of the transparent conductive layer to low-temperature plasma before the treatment. In particular, when the inorganic dielectric layer having good adhesion is formed by the vacuum vapor deposition method, which is most advantageous in terms of film forming apparatus limitation, running cost, apparatus maintenance, etc., in front of the surface of the transparent inorganic conductive layer by the low temperature plasma. Processing is required. The low-temperature plasma introduces gas into the tank under reduced pressure, and directs, AC,
It is generated by applying a high frequency voltage. The gas used here is not particularly limited, but is preferably oxygen or argon, and argon gas is most preferable from the viewpoint of eliminating the risk of deterioration of electrical characteristics of the ITO film. The pressure of the gas used is not particularly limited as long as the plasma state is stable, but is preferably 5 × 10 ⁻⁵ to 1 × 10 ⁻¹ Torr. Although the low-temperature plasma treatment time varies depending on the plasma state, a sufficient treatment effect is usually obtained when it is about 10 seconds or longer. The formation of the inorganic dielectric layer may be carried out after the surface of the transparent inorganic conductive layer is exposed to the air after low-temperature plasma treatment, but the surface of the transparent inorganic conductive layer is formed to prevent contamination by dust in the air. More preferably, it is performed immediately after the low temperature plasma treatment.

According to the present invention, it has been confirmed that the electromagnetic wave shielding effect is exhibited even if the transparent inorganic conductive layer is not grounded by a conductor or the like. However, when it is necessary to ground the transparent inorganic conductive layer or connect it to a conductive wire in order to impart antistatic property or antifogging property due to heating, etc. It is possible to devise such that the portion is not covered with the insulating layer.

[0010]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1, Comparative Example 1 Commercial PET film ("Lumirror" T manufactured by Toray Industries, Inc.
An ITO film was formed on one surface of a (type) 50 μm product by an ion plating method. For ITO, a sintered pellet product containing 5% by weight of SnO ₂ was used.
It was heated with an electron beam and evaporated. The deposition rate on the PET film was about 1.5Å / sec and the film thickness was about 800Å. Once taken out into the atmosphere, the PET film with ITO film was then vacuum-deposited (Showa Vacuum SGC-16).
WA) attached to a planetary in a vacuum chamber, the vacuum chamber was evacuated by a vacuum pump, and when reaching 3 × 10 ⁻⁵ Torr, while introducing argon gas into the chamber up to 1 × 10 ⁻⁴ Torr, 13.56 on the coiled electrode placed inside
When high-frequency power of MHz was applied at an output of 600 W, reddish purple plasma was generated in the entire vacuum chamber. After the ITO film surface was exposed to the above plasma atmosphere for 1 minute, the application of high frequency power to the electrodes and the introduction of argon gas were stopped to complete the plasma treatment. The pressure in the vacuum chamber was 5 × 10 ⁻⁵ Torr. Subsequently, SiO ₂ was heated and evaporated by an electron beam to be deposited on the ITO film. The deposition rate was about 18Å / sec and the film thickness was about 940Å. The surface-treated film thus obtained was evaluated with respect to each item of 5 degree normal light reflectance, film adhesion, surface scratch resistance, and electromagnetic wave shielding property. 5 degree specular reflectance is Hitachi's own recording spectrophotometer U
It was measured with -3400 type. Spectral light reflectance spectrum (I in the visible light region of the film before forming the SiO ₂ film)
FIG. 1 shows the TO film side (measured from the TO film side), and FIG. 2 shows the spectral reflectance spectrum (measured from the SiO ₂ film side) in the visible light region of the film in which the SiO ₂ film is formed on the ITO film. 55
The light reflectance at the wavelength of 0 nm was about 20% (including the back surface reflection) before the SiO ₂ film was formed (Comparative Example 1), whereas the film having the SiO ₂ film formed on the ITO film was compared. It was reduced to about 6% (including back reflection), and no glare due to light reflection was felt. The adhesiveness of the film was determined by cutting 100 cross-cuts in an area of about 1 cm ² from the ITO film and SiO ₂ film side with a cutter knife, and applying 9 pieces of cellophane tape evenly on it.
When evaluated by a method of quickly peeling off at an angle of 0 degree, neither film peeled off, and the adhesion was good. The scratch resistance of the surface was evaluated by a method of observing the occurrence of scratches when rubbing with a flannel cloth under a load of 400 g / cm ² for 100 reciprocations. The electromagnetic wave shielding property was evaluated by a near electric field shield effect measurement using a cell of the Kansai Electronics Industry Promotion Center method. As a result, the electromagnetic wave attenuation rate at a frequency of 300 MHz was 17 decibels. Furthermore, 50 ℃
-The same evaluation was performed after leaving it in an environment of 90% RH for 96 hours, and it was found that all the items did not change and the durability was good. The above results are shown in Table 1.

Example 2 Instead of forming an ITO film on a PET film, a commercially available PET film with a transparent conductive film (ITO) (“METASTAR” T-R60 manufactured by Toyo Metalizing Co., Ltd., PET thickness 50 μm) is used. Except for the above, in the same manner as in Example 1,
The ITO film surface is subjected to low temperature plasma treatment with argon gas,
_Two films were deposited. When the performance of the obtained surface-treated film was evaluated by the same method as in Example 1, the light reflectance at a wavelength of 600 nm was about 6% (including backside reflection),
No glare due to light reflection was felt. S
The adhesion and scratch resistance of the iO ₂ film are good, and the frequency 3
The attenuation rate of electromagnetic waves at 00 MHz was 19 decibels. Furthermore, the same evaluation was performed after leaving it in an environment of 50 ° C. and 90% RH for 96 hours, and it was found that all the items did not change and the durability was good. The results are shown in Table 1.

Example 3 Argon gas low temperature plasma treatment conditions on the ITO film surface were as follows: ultimate pressure in the vacuum chamber was 3 × 10 ⁻⁵ Torr, pressure after introducing argon gas was 1 × 10 ⁻⁴ Torr, frequency 13.56 MH.
A PET / ITO / SiO ₂ film was obtained in the same manner as in Example 2 except that the z and the output were 200 W and the processing time was 15 seconds. When the performance of the obtained surface-treated film was evaluated in the same manner as in Example 1, the light reflectance at a wavelength of 600 nm was about 6% (including back surface reflection), and no glare due to light reflection was observed. I couldn't feel it. The SiO ₂ film had good adhesion and scratch resistance, and the attenuation factor of electromagnetic waves at a frequency of 300 MHz was 19 decibels. Furthermore, the same evaluation was performed after leaving it in an environment of 50 ° C. and 90% RH for 96 hours, and it was found that all the items did not change and the durability was good. The above results are shown in Table 1.

Example 4 The conditions of low temperature argon gas plasma treatment of the ITO film surface were as follows: ultimate pressure in the vacuum chamber was 3 × 10 ⁻⁵ Torr, pressure after introducing argon gas was 1 × 10 ⁻⁴ Torr, frequency 13.56 MH.
Example 2 except that the processing time was 5 minutes at z and an output of 800 W
A PET / ITO / SiO ₂ film was obtained in the same manner as in. When the performance of the obtained surface-treated film was evaluated in the same manner as in Example 1, the light reflectance at a wavelength of 600 nm was about 6% (including back surface reflection), and no glare due to light reflection was observed. I couldn't feel it. The SiO ₂ film had good adhesion and scratch resistance, and the attenuation factor of electromagnetic waves at a frequency of 300 MHz was 19 decibels. Furthermore, the same evaluation was performed after leaving it in an environment of 50 ° C. and 90% RH for 96 hours, and it was found that all the items did not change and the durability was good. The above results are shown in Table 1.

[0015] except for forming by vacuum deposition MgF ₂ (magnesium fluoride) in place of Example 5 SiO ₂ in the same manner as in Example 2 PE
A T / ITO / MgF ₂ film was obtained. The film forming conditions were a vacuum chamber pressure of 5 × 10 ⁻⁵ Torr, electron beam heating, a deposition rate of about 25Å / sec, and a film thickness of about 1000Å. When the performance of this film was evaluated by the same method as in Example 1, the light reflectance at a wavelength of 600 nm was about 6% (including back surface reflection), and no glare due to light reflection was felt. The adhesion and scratch resistance of the MgF ₂ film were good, and the attenuation factor of electromagnetic waves at a frequency of 300 MHz was 19 decibels. When the same evaluation was performed after leaving it in the environment of 50 ° C. and 90% RH for 96 hours, some scratches were found in the scratch resistance test.
However, other than that, the durability was good without any change.
The above results are shown in Table 1.

Comparative Example 2 PET / ITO / SiO was prepared in the same manner as in Example 1 except that the low temperature argon gas plasma treatment of the ITO film surface was not carried out.
₂ films were obtained. When the adhesion of the SiO ₂ film was evaluated in the same manner as in Example 1, the SiO ₂ film was peeled off in the entire area of adhesion to the cellophane tape. The results are shown in Table 1.

Comparative Example 3 PET / ITO / Mg was prepared in the same manner as in Example 5 except that the argon gas low temperature plasma treatment was not performed on the ITO film surface.
An F ₂ film was obtained. When the adhesiveness of the MgF ₂ film was evaluated in the same manner as in Example 1, the MgF ₂ film was peeled off in the entire area in which it was adhered to the cellophane tape. The results are shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, the present invention provides an electromagnetic wave shielding film having a structure in which a transparent inorganic conductive layer is provided on the surface of a transparent synthetic resin film and a layer having a refractive index lower than that of the conductive layer is provided on the surface layer thereof. Therefore, it is possible to provide an electromagnetic wave shielding film having an electromagnetic wave shielding property, excellent visibility, and preventing the conductive layer from reflecting light rays. Furthermore, by exposing the surface of the transparent inorganic conductive layer to low temperature plasma such as argon gas, and then forming a layer having a refractive index lower than that of the conductive layer on the surface of the transparent inorganic conductive layer, film adhesion, scratch resistance, etc. It is possible to provide an electromagnetic wave shielding film having excellent film strength durability, electromagnetic wave shielding property, excellent visibility, and preventing light reflection of the conductive layer.

[Brief description of drawings]

FIG. 1 is a diagram showing a spectral reflectance spectrum in a visible light region of a film before forming a SiO ₂ film.

FIG. 2 is a diagram showing a spectral reflectance spectrum in a visible light region of a film having a SiO ₂ film formed on an ITO film.

Claims (3)

[Claims] 1. An electromagnetic wave shielding film having antireflection properties, comprising a transparent inorganic conductive layer provided on the surface of a transparent synthetic resin film, and a layer having a refractive index lower than that of the conductive layer provided on the surface thereof. 2. The transparent synthetic resin film is a polyethylene terephthalate resin film, and the transparent inorganic conductive layer is I.
The electromagnetic wave shielding film according to claim 1, wherein the layer made of a mixture of n ₂ O ₃ and SnO ₂ and having a lower refractive index than the conductive layer is a layer made of SiO ₂ . 3. A surface of a transparent inorganic conductive layer provided on a transparent synthetic resin film is exposed to low temperature plasma, and then a layer having a refractive index lower than that of the conductive layer is formed on the surface of the conductive layer. And a method for producing an electromagnetic wave shielding film having antireflection property.