JP2000062082A - Electromagnetic wave shielded film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electromagnetic wave shielded film provided with 2 Ω/square resistance or less and superior light transmission properties and suitable for the purpose of display. SOLUTION: An electromagnetic wave shielded film is formed of two or more metal film layers B containing silver as a main component and one or more conductive film layers C containing a metal oxide as a main component laminated respectively on a transparent polymer film A, and at least the B, C, B layer constitution unit is contained in the film. Preferably two or more metal layers B and three or more conductive film layers C are laminated on the transparent polymer film A, and at least the C, B, C, B, C layer constitution unit is contained in the electromagnetic shielded film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding film in which a metal thin film layer and a conductive thin film layer are laminated on a transparent polymer film, and more specifically, it is required to have both high electromagnetic wave shielding property and high light transmitting property. The present invention relates to an electromagnetic wave shield film suitable for display applications.

[0002]

2. Description of the Related Art Due to the recent demand for electromagnetic wave shield measures for large CRT televisions and plasma displays,
There is a demand for a transparent conductive film having a surface resistance of 0 Ω / □ or less and excellent in visible light transmittance. Particularly when used as an electromagnetic wave shield filter of a plasma display, a surface resistance of about 2Ω / □ or less is required.

On the other hand, as a transparent conductive film, conventionally, a film in which a thin film of metal such as indium oxide (hereinafter referred to as ITO) to which tin oxide is added, gold or silver is laminated on a polymer film is well known. Generally, a transparent conductive film in which an oxide semiconductor typified by ITO is laminated on a polymer film has film forming conditions limited due to the problem of heat resistance of a substrate film, and its surface resistance is limited to several tens Ω / □. there were. Therefore, in order to meet the demand for low surface resistance as described above, gold,
1 thin film of metal with low resistivity such as silver, copper, aluminum
Conductive films laminated around 0 nm have been studied.

Among the conductive films formed by laminating these metal thin films, a silver thin conductive film having excellent conductivity, flat absorption of visible light and gray color is preferable, but light transmittance is important in display applications. However, the film thickness cannot be increased due to the reduction of the transmittance due to the reflection from the silver thin film surface. For example, when the visible light transmittance is 60% or more, the surface resistance becomes 10 Ω / □ or more, which is an advanced electromagnetic wave shield. I can't expect an effect. Further, due to the low environmental stability of the silver thin film, measures such as alloying and protective film lamination have been investigated, but it has been pointed out that the alloying lowers the conductivity and the protective layer lowers the optical characteristics.

Japanese Patent Laid-Open No. 63-173395 proposes that a thin silver film is sandwiched between ITO films having an appropriate thickness to suppress reflection due to an interference effect and improve the light transmittance. However, even in such a configuration, 60
It was difficult to achieve both a visible light transmittance of not less than% and a surface resistance of not more than 2Ω / □.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and an object thereof is to provide a display use which has a surface resistance of 2Ω / □ or less and is excellent in translucency. It is to provide a suitable electromagnetic wave shielding film.

[0007]

Means for Solving the Problems The present inventors have achieved the present invention as a result of extensive studies to solve such problems.
That is, the present invention is as follows. (1) On the transparent polymer film (A), two or more metal thin film layers (B) containing silver as a main component and one or more conductive thin film layers (C) containing metal oxide as a main component. Each is laminated and at least (B) (C) (B)
An electromagnetic wave shielding film comprising the layer constitutional unit of. (2) On the transparent polymer film (A), two or more metal thin film layers (B) containing silver as a main component and three or more conductive thin film layers (C) containing metal oxide as a main component. Each is laminated and at least (C) (B) (C)
An electromagnetic wave shielding film comprising the layer constitutional units (B) and (C). (3) The electromagnetic wave shielding film as described in (1) or (2) above, wherein the metal thin film layer (B) has a film thickness of 5 nm to 20 nm. (4) At least one of the conductive thin film layers (C) has a thickness of 50.
When the water vapor transmission rate of a film obtained by laminating only one conductive thin film layer (C) having a thickness of 10 nm or more on a biaxially stretched polyethylene terephthalate film of μm was measured,
/ M ² · 24 hr or less, the electromagnetic wave shielding film as described in (1) or (2) above, which is a conductive thin film layer (C). (5) The surface resistance is 2Ω / □ or less (1) or
The electromagnetic wave shielding film described in (2). (6) The electromagnetic wave shielding film as described in any of (1) to (5) above, wherein the conductive thin film layer (C) contains tin oxide as a main component. (7) The electromagnetic wave shielding film as described in any of (1) to (5) above, wherein the conductive thin film layer (C) contains zinc oxide as a main component. (8) The electromagnetic wave shielding film as described in any of (1) to (5) above, wherein the conductive thin film layer (C) contains indium oxide as a main component.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. The electromagnetic wave shielding film of the present invention comprises a transparent polymer film (A), and two or more metal thin film layers (B) and one or more conductive thin film layers (C).

Transparent polymer film (A) in the present invention
As for the mechanical strength, which is transparent and can withstand the film forming process,
It is not particularly limited as long as it has heat resistance, for example,
Films of polyester resin, polyolefin resin, polysulfone resin, etc. may be mentioned. Specifically, polyethylene terephthalate (hereinafter, also referred to as PET),
Examples of the film include polycarbonate and polyether sulfone. Among these, the PET film can be preferably used because of its balance of properties and price. In particular,
A highly transparent PET film in which a lubricant layer is laminated by an in-line coating method during film formation is preferable.

The thickness of the transparent polymer film (A) is 25-
300 μm is preferable, and more preferably 50 to 200 μm.
m. In addition, the transparent polymer film (A) is a colorant, as long as the mechanical properties and optical properties are not impaired.
Known additives such as an ultraviolet absorber, a stabilizer, a plasticizer and a dye may be contained, or a coating layer containing these additives may be laminated by a known method. further,
Various color filters, an antireflection film for improving visibility by reducing reflectance, a non-glare film, a hard coat film for preventing screen scratches, and the like may be laminated in advance by a known method. Further, these coat layers may be laminated after laminating a metal thin film layer (B) and a conductive thin film layer (C) described later. In particular, when used as an electromagnetic wave shield filter of a plasma display, the transparent polymer film (A) contains a dye that absorbs near infrared rays which causes malfunction of remote control or infrared communication, or contains this dye. It is preferable to stack a coat layer.

The metal thin film layer (B) in the present invention is a metal thin film layer containing silver as a main component. The thickness of the metal thin film layer (B) is preferably 5 to 20 nm, more preferably 10 to 15 nm. When the film thickness is less than 5 nm, the surface resistance of the obtained electromagnetic wave shielding film may be too large, and conversely, when it is thicker than 20 nm, the light transmittance of the obtained electromagnetic wave shielding film may be significantly low.

Silver is excellent in conductivity, and a silver thin film having a thickness of 20 nm or less has a near-flat absorption in the visible light region, and is therefore suitable as a conductive layer of a low resistance conductive film. However, the silver thin film is inferior in environmental stability, and causes problems such as sulfidation corrosion and migration especially under high temperature and high humidity. In order to improve the environmental stability, it is effective to block moisture that enters the silver thin film layer by laminating a gas barrier thin film on the outer surface. Further, it is preferable to use an alloy film with palladium, gold, copper or the like, but if the amount of the added metal component is large, the electrical conductivity will decrease, so the addition amount is preferably 5% by weight or less, more preferably 1% by weight or less. is there.

The metal thin film layer (B) used in the present invention is produced by a known thin film forming method such as a vacuum vapor deposition method, a sputtering method and an ion plating method. Here, the sputtering method is a DC magnetron sputtering method, an RF magnetron sputtering method, or the like,
For example, when forming a silver thin film, use a silver target,
Argon gas is used as the sputtering gas.

The conductive thin film layer (C) in the present invention means
It is a conductive thin film containing a metal oxide as a main component.
Examples of the metal oxide as the main component include tin oxide, zinc oxide,
Indium oxide or the like can be preferably used. Although ITO in which tin oxide is added to indium oxide in an amount of 5 to 10% by weight has excellent conductivity, indium is feared to have a small reserve and is relatively expensive. It is preferable to use tin oxide or zinc oxide as a main component.
Tin oxide containing antimony oxide and zinc oxide containing aluminum oxide are excellent in conductivity and can be preferably used.

The thickness of the conductive thin film layer (C) is selected so as to optimize the optical characteristics of the electromagnetic wave shielding films laminated in all layers. Specifically, by defining the refractive index of the thin film material used and the transmittance and reflectance at a specific wavelength, the optimum film thickness of each layer can be obtained by simulation calculation. More specifically, of the electromagnetic wave shielding film,
The wavelength of each layer is 400 to 750 nm, especially the light transmittance of 550 nm is high (light reflectance is low) and the light transmittance of 350 nm or less and 850 to 1100 nm is low (light reflectance is high). Designed by simulation calculation.

The conductive thin film layer (C) used in the present invention is produced by a known thin film forming method such as vacuum vapor deposition or sputtering. In addition, by optimizing the film forming conditions of the conductive thin film, it is possible to obtain a denser thin film structure having a high film density, and it is possible to provide excellent gas barrier properties in which moisture and gas are unlikely to enter. The durability of the metal thin film layer (B) protected by the conductive thin film layer (C) having such an excellent gas barrier property is significantly improved. In the present invention, the gas barrier property of the conductive thin film layer (C) means the amount of water vapor permeation and oxygen permeation of a laminated film in which only one conductive thin film layer (C) is formed on a biaxially stretched PET having a thickness of 50 μm. The gas barrier property is good when the water vapor transmission rate is about 0.5 g / m ² · 24 hr or less and the oxygen transmission rate is about 0.5 cc / atm · m ² · 24 hr or less. It can be said that there is. The film thickness of the conductive thin film layer (C) at the time of measuring the amount of water vapor transmission and the amount of oxygen transmission needs to be 10 nm or more, preferably 15 nm or more, more preferably 20 nm.
That is all.

As a method for producing such a gas barrier conductive thin film layer (C), for example, in the sputtering method, (1) a method of lowering the film forming process pressure to prevent structural defects due to incorporation of argon gas (2) A method of lowering the power applied to the target during film formation,
(3) A method of controlling the amount of oxygen added in order to stoichiometrically match the oxidation degree of the film, and (4) cooling the substrate holder or the center roll, on which the substrate is mounted, with circulating water from the back side to obtain the substrate temperature. Is formed by appropriately combining methods such as a method of forming a non-crystalline structure so as not to rise.

The metal thin film layer (B) and the conductive thin film layer (C) in the present invention are formed by a vacuum film forming method, but all the films are formed by one process such as a vacuum vapor deposition method and a sputtering method. When it is possible to unify, it is possible to form a film by a roll-to-roll method in the same chamber using a transparent polymer film (A) wound in a roll shape from the viewpoint of uniformity of the thin film and cost. preferable.

In the electromagnetic wave shielding film of the present invention, two or more metal thin film layers (B) and a conductive thin film layer (C) are used.
Is laminated in one or more layers and contains at least the layer constitutional units (B), (C) and (B). Preferably,
As shown in FIG. 1, two or more metal thin film layers (B) and three or more conductive thin film layers (C) are laminated, and at least (C) (B) (C) (B) ( The layer constitutional unit of C) is included. In the range of the thickness of the metal thin film layer (B) that can satisfy the light transmission property, the conductivity of the electromagnetic wave shielding film is insufficient when only one layer is provided. For example, in the case of a silver thin film, it has a thickness of about 4 Ω / □ at a thickness of 12 nm, but by using a layer structure as shown in FIG. 1 and using two metal thin film layers (B), the light transmittance is not significantly lowered and the conductivity is reduced. Can be greatly improved. Furthermore, layers other than the metal thin film layer (B) and the conductive thin film layer (C) may be appropriately laminated as the underlayer and the antireflection layer, if necessary.

In the electromagnetic wave shielding film of the present invention, the light reflectance at 400 to 750 nm, particularly 550 nm, is 10% or less, particularly 5% or less, 350 nm or less and 850.
~ 1100nm light transmittance is less than 20%, especially 10%
The surface resistance value is 2Ω / □ or less, particularly 1.5Ω / □ or less. Also, frequency 1
The electromagnetic wave shielding property at 00 MHz is 40 dB or more,
In particular, it has a characteristic of 50 dB or more.

In the present invention, the surface resistance value of the film means the metal thin film layer (B) on the transparent polymer film (A).
And the resistance value of the surface on the side where the conductive thin film layer (C) is laminated.

Further, the electromagnetic wave shielding film of the present invention is excellent in environmental stability, and can retain practical practicable light-transmitting property and electromagnetic wave shielding property even when exposed to a high temperature and high humidity atmosphere for a long period of time, so that it is resistant to environmental changes. It is a stable electromagnetic wave shield film that is not affected.

[0023]

EXAMPLES The present invention will be described below based on examples, but the measuring methods of the respective characteristics in the examples are as follows.

1. Electromagnetic shielding property Electromagnetic shielding property tester (MA8 manufactured by Anritsu Corporation)
602B) and a spectrum analyzer (MS2661C manufactured by Anritsu Co., Ltd.) according to the Kansai Electronics Industry Promotion Center (KEC) method.

2. Film thickness ellipsometer (Mizojiri Optical Co., Ltd., DV-
36S type), a silicon substrate was used instead of the transparent polymer film (A), and a thin film formed on this substrate by the same process as in the example was measured.

3. According to JIS K7194, the surface resistance value was measured by a 4-probe method using a resistivity meter (Loresta AP manufactured by Mitsubishi Petrochemical Co., Ltd.).

4. Total light transmittance, haze haze meter (NDH-1 manufactured by Nippon Denshoku Industries Co., Ltd.)
001 DP).

5. Light transmittance, light reflectance According to JIS K7105, it was measured using a spectrophotometer with integrating sphere (U-3500 type, manufactured by Hitachi, Ltd.).

6. Water vapor transmission rate According to JIS K7129, a water vapor transmission rate measuring device (PERMTRAN-W3 / 31 manufactured by Mokon Co., Ltd.) was used, and measurement was performed at a measurement temperature of 40 ° C. and a relative humidity of 0% RH / 90% RH.

7. It was left for 500 hours in an environment of heat resistance of 80 ° C., and the change in its appearance was visually observed.

8. It was left for 500 hours in an environment of humidity resistance of 60 ° C. and 95% RH, and the change in its appearance was visually observed.

Example 1 As a transparent polymer film substrate, a thickness of 100 μm, 15
A cm × 15 cm biaxially stretched polyethylene terephthalate film (Cosmoshine A4100, manufactured by Toyobo Co., Ltd.) having a total light transmittance of 90.9% was set in a multi-target sputtering apparatus, and the pressure was reduced to about 1 × 10 ⁻⁴ Pa. . Argon 20scc as sputter gas
m, oxygen 0.1 sccm was introduced, and the pressure in the chamber was 0.2 Pa. As the first layer, a conductive thin film layer of tin oxide having a thickness of 38 nm was deposited by a high frequency magnetron sputtering method at an input power of 1 W / cm ² at a very slow film formation rate while cooling the substrate. As the second layer, a 12 nm silver thin film layer was laminated by DC magnetron sputtering. Next, a conductive thin film layer of tin oxide having a thickness of 94 nm was laminated as the third layer by the same method as the first layer. Further, as the fourth layer, a 12 nm silver thin film layer was laminated by the same method as the second layer. As the fifth layer, 43 nm tin oxide was laminated in the same manner as the first layer. The surface resistance value of this conductive film is 1.8Ω / □, and the total light transmittance is 70.
%, Light transmittance at 900 nm is 15%, 1000
The light transmittance at 10 nm was 10%, the light reflectance at 550 nm was 1.5%, and the haze was 1.0%. The electric field shield effect at a frequency of 100 MHz is 50 dB.
Met. Even after the moisture resistance test and the heat resistance test, there was no change in the appearance, the light transmittance, the light reflectance, and the surface resistance value. In addition, the tin oxide used in this laminate was
The water vapor transmission rate of a laminated film formed with a thickness of 20 nm on a PET film of 0 μm is 0.2 g / m ² · 24 hr.
The water barrier property was also good.

Example 2 A conductive film was prepared in the same manner as in Example 1 except that ITO was used instead of tin oxide. The thickness of the ITO thin film layer is 41 nm for the first layer, 88 nm for the third layer, and 38 for the fifth layer.
was nm. The film thickness of each of the second and fourth silver thin film layers was 12 nm. The surface resistance value of this conductive film is 1.5Ω / □, the total light transmittance is 70%, 900
The light transmittance at 15 nm was 15%, the light transmittance at 1000 nm was 10%, the light reflectance at 550 nm was 1.5%, and the haze was 1.0%. Frequency 100
The electric field shield effect at MHz was 50 dB.
Even after the moisture resistance test and the heat resistance test, there was no change in the appearance, the light transmittance, the light reflectance, and the surface resistance value. Also,
The ITO used for this laminated body was made to have a P
The water vapor transmission rate of the laminated film formed on the ET film with a thickness of 20 nm was 0.3 g / m ² · 24 hr, and the moisture barrier property was also good.

Example 3 Instead of tin oxide, zinc oxide (containing 2% by weight of alumina)
A conductive film was prepared by using the same method as in Example 1. The film thickness of zinc oxide was 38 nm for the first layer, 94 nm for the third layer, and 43 nm for the fifth layer. The film thickness of each of the second and fourth silver thin film layers was 12 nm.
The surface resistance value of this conductive film is 1.6Ω / □, the total light transmittance is 70%, and the light transmittance at 900 nm is 1
5%, light transmittance at 1000 nm is 10%, 55
The light reflectance at 0 nm is 1.5% and the haze is 1.0.
%Met. The electric field shield effect at a frequency of 100 MHz was 50 dB. Even after the moisture resistance test and the heat resistance test, there was no change in the appearance, the light transmittance, the light reflectance, and the surface resistance value. Further, the zinc oxide used in this laminate was formed on a PET film having a thickness of 50 μm under the same conditions to give a film thickness of 20 n.
The water vapor transmission rate of the laminated film formed with m is 0.3 g /
It was m ² · 24 hr, and the moisture barrier property was also good.

Comparative Example 1 A biaxially stretched polyethylene terephthalate film (Cosmoshine A4100, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm and a total light transmittance of 90.9% was used as a first layer of 41 nm of I.
A conductive thin film layer of TO was laminated by high frequency sputtering. As the second layer, a 12 nm silver thin film layer was laminated by DC magnetron sputtering. Next, 38 nm ITO was laminated as a third layer in the same manner as the first layer. The surface resistance value of this conductive film is 6Ω / □, the total light transmittance is 75%, and the light transmittance at 900 nm is 3
0%, light transmittance at 1000 nm is 25%, 55
Light reflectance at 0 nm is 10%, haze is 1.0%
Met. The electric field shield effect at a frequency of 100 MHz was 30 dB. Compared with the conductive films obtained in Examples 1 to 3, the total light transmittance was slightly improved, but the surface resistance value was considerably high and the electromagnetic wave shielding effect was low. Moreover, the light transmittance in the near infrared wavelength region was also considerably high.

[0036]

As is apparent from the above description, according to the present invention, it is possible to provide an electromagnetic wave shielding film having both high electromagnetic wave shielding property and high light transmitting property. Further, the electromagnetic wave shielding film of the present invention has good near-infrared ray cutting characteristics, antireflection characteristics, environmental stability and the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of an electromagnetic wave shielding film of the present invention.

[Explanation of symbols]

(A) Transparent polymer film (B) Metal thin film layer (C) Conductive thin film layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuo Shimomura             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Yozo Yamada             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. F-term (reference) 4F100 AA17C AA17E AA25C AA25E                       AA28C AA28E AB01B AB01D                       AB24B AB24D AK01A AK42A                       BA04 BA05 BA07 BA08 BA10A                       BA26 EJ37A GB48 JD04                       JD08 JG01C JG01E JG04                       JM02B JM02C JM02D JM02E                       JN01 JN01A YY00

Claims (8)

[Claims] 1. A transparent polymer film (A) having two or more metal thin film layers (B) containing silver as a main component and one conductive thin film layer (C) containing a metal oxide as a main component. Each layer is laminated by at least (B)
An electromagnetic wave shielding film comprising the layer constitutional units (C) and (B). 2. A transparent polymer film (A) having two or more metal thin film layers (B) containing silver as a main component and three conductive thin film layers (C) containing a metal oxide as a main component. Each layer is laminated by at least (C)
An electromagnetic wave shielding film comprising (B), (C), (B) and (C) as a layer constitutional unit. 3. The film thickness of the metal thin film layer (B) is 5 nm to 20.
It is nm, The electromagnetic wave shield film of Claim 1 or 2 characterized by the above-mentioned. 4. At least one of the conductive thin film layers (C) has a thickness of at least 10 nm on a biaxially stretched polyethylene terephthalate film having a thickness of 50 μm.
The electromagnetic wave according to claim 1 or 2, which is a conductive thin film layer (C) having a water vapor transmission rate of 0.5 g / m ² · 24 hr or less when a film in which only one layer is laminated is measured. Shield film. 5. The electromagnetic wave shielding film according to claim 1, which has a surface resistance value of 2Ω / □ or less. 6. The electromagnetic wave shield film according to claim 1, wherein the conductive thin film layer (C) contains tin oxide as a main component. 7. The electromagnetic wave shielding film according to claim 1, wherein the conductive thin film layer (C) contains zinc oxide as a main component. 8. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein the conductive thin film layer (C) contains indium oxide as a main component.