JP4681936B2 - Copper foil for plasma display electromagnetic wave shielding filter - Google Patents

Description

  The present invention relates to a copper foil used in an electromagnetic wave shielding filter which is one of multifunctional optical filters used in a plasma display. More specifically, the present invention relates to a plasma display electromagnetic wave having excellent characteristics for effectively shielding electromagnetic waves. It is related with the copper foil for shield filters, and its manufacturing method.

  The mainstream of image display is a cathode ray tube, but in recent years, plasma display panels having functions such as a large screen, a thin shape, a light weight, and a small screen distortion have spread.

  However, the plasma display uses the principle of light emission by gas discharge, and the radiated electromagnetic waves from the front of the display are large. It is necessary to clear regulations (VCCI) etc. In addition to generating noise that adversely affects peripheral devices, electromagnetic waves emitted from the main body have recently been reported to have an adverse effect on the human body, and electromagnetic shielding filters are used to suppress them. .

  Electromagnetic wave shielding filter is a metal fiber knitted mesh, polyester film (hereinafter referred to as PET) as a base material, such as copper or nickel electrodeposited in a mesh shape by electroless plating, etc., copper foil PET There is a method in which a mesh is formed by etching after laminating to an adhesive, but recently, a method of forming a mesh by etching after laminating a copper foil to PET / adhesive is becoming mainstream. These electromagnetic wave shielding filters are required to be as thin as possible, and it is desired to achieve both light transmittance and electromagnetic wave shielding properties that are contrary to this. In the electromagnetic wave shielding filter that requires such characteristics, the following three points are particularly important characteristics required for the copper foil as a constituent material.

1. The laminated surface of the copper foil is black
(Reason) To prevent reflection from outside light and enhance the contrast effect to obtain a clear image.
2. The copper foil must have a very low roughness
(Reason) The metal mesh of the electromagnetic wave shielding filter generally has a copper width of 10 to 20 μm and a mesh interval of 200 to 300 μm. For this reason, in the case of a high-roughness copper foil, the side etching at the time of etching becomes large, resulting in a problem that it is difficult to obtain a highly accurate mesh.
3. High smoothness of copper foil laminate surface
(Reason) Since the viewer sees the light transmitted through the part without the metal mesh of the electromagnetic shielding filter, the image becomes clearer when the transparency of the PET / adhesive after etching is higher. Since the surface shape of the PET / adhesive after etching is a shape obtained by directly transferring the copper foil laminate surface, the higher the smoothness of the copper foil laminate surface, the better the transparency.

  As a processing method for developing a black appearance by a conventional technique, a method of performing a cobalt-nickel alloy plating layer on a surface of a copper foil after a roughening process by copper-cobalt-nickel alloy plating has been proposed. (See Patent Document 1). However, when the inventors of the present invention conducted a follow-up experiment on the invention, it was possible to express a color tone close to black, but it was actually grayish black and insufficient to develop a complete black color. . Furthermore, since the roughened particles are dendritic and relatively large, they have the disadvantages of poor transparency of the PET / adhesive after etching and the degree of powder fall off.

In addition, as a surface treatment method for copper foils for plasma display electromagnetic wave shielding filters, a method of forming an alloy plating layer made of tin-nickel-molybdenum after forming a roughened layer made of copper particles on the surface of the copper foil was proposed. ing. However, when the inventors of the present invention conducted a follow-up experiment on the invention, a relatively large copper dendritic roughening treatment was performed before applying the alloy plating layer made of tin-nickel-molybdenum, and Because of the cover plating that develops the roughening treatment and the adhesion of copper foil, the roughness of the rough surface is increased, the transparency of the PET / adhesive after etching is poor, and the color tone is also brown to dark brown It is insufficient to develop a complete black color.
Japanese Patent Laid-Open No. 9-87889 Japanese Patent Laid-Open No. 2003-201597

  The problems to be solved by the present invention are the characteristics that are particularly strongly required for the copper foil for plasma display electromagnetic wave shielding filter, the laminated surface of the copper foil is black, the copper foil is ultra-low roughness, the copper foil Another object of the present invention is to provide a copper foil for an electromagnetic wave shielding filter for a plasma display having the above three characteristics and a method for producing the same.

As a result of examining various surface treatments in order to solve this problem, it was found that the copper foil can be achieved by performing the following surface treatments.
1. A copper-colored color system L ^* a ^* b ^* described in JISZ8729 with an L ^* of 30 or less and a specular gloss measured by Gs (85 °) of 80 or more according to JISZ8471 Having a roughened layer made of tin on at least one surface of the copper foil. 2. The size of the roughening particles forming the roughening layer made of copper-tin is 0.6 μm or less. 3. The ten-point average roughness Rz after forming the roughening layer made of copper-tin is 1.5 μm or less. 4. The composition of the roughened layer made of copper-tin is 0.5 to 6.0 wt% tin, and the balance is copper.

  The effect of the present invention is that it is possible to effectively shield electromagnetic waves by performing the surface treatment of the above form on at least one surface of the copper foil, and it is possible to suppress reflection from external light extremely low. Therefore, since the contrast effect is high and a clear image is obtained, and since it is ultra-low roughness, a high-accuracy mesh is obtained because the etching property is good, and the PET / adhesive after etching This is a copper foil for a plasma display electromagnetic wave shielding filter having a feature that transparency becomes high and a clear image can be obtained.

  In addition, since the copper foil subjected to the surface treatment of the present invention has features such as having fine roughened particles and ultra-low roughness, it is not only a general copper foil for printed wiring boards but also a high-frequency substrate. Suitable for copper foil for liquid crystal, copper foil for liquid crystal polymer, and copper foil for two-layer flexible substrate.

  The present invention is described in detail below.

  First, it is an untreated copper foil to be used, but there is no need to limit it to rolling or electrolytic copper foil, and any copper foil may be used, but in this application, the copper foil has a very low roughness. Therefore, it is preferable to use an untreated copper foil having a roughness Rz of 1.2 μm or less in consideration of the increase in roughness in the roughening treatment. Even when untreated copper foil with high roughness is used, black color due to copper-tin roughened particles is possible, but problems such as poor etchability and poor transparency of the PET / adhesive after etching occur. Since there are cases, it is not preferable. The foil thickness is 5 to 35 μm, more preferably 6 to 18 μm.

  The roughening treatment layer made of copper-tin of the present invention is formed by cathodic electrolysis using a pyrophosphate bath containing copper ions and tin ions. Examples of the bath composition and electrolysis conditions for forming the roughened layer made of copper-tin are given below, but the invention is not limited to these.

(Electrolytic bath composition)
Cupric pyrophosphate 10-200 g / L (particularly preferably 20-100 g / L)
Stannous pyrophosphate 0.1-10 g / L (particularly preferably 0.2-4 g / L)
Potassium pyrophosphate 100-500 g / L (particularly preferably 150-350 g / L)
pH 8-10 (particularly preferably 8.8-9.7)
pH adjusted with sodium hydroxide or ammonia

(Electrolysis conditions)
Bath temperature 20-80 ° C (particularly preferably 30-60 ° C)
Current density 3 to 30 A / dm ² (particularly preferably 5 to 20 A / dm ² )
Electricity 10 ~ 150A ・ sec / dm ² (Preferably 30 ~ 100A ・ sec / dm ² )
When viewed macroscopically, the color tone of the copper foil provided with the roughening treatment layer made of copper-tin of the present invention exhibits an extremely high black color with no processing unevenness. Its blackness is the color of a color system of L ^* a ^* b ^* L ^* according to JISZ8729 30 or less. Considering that L ^* of general black drawing paper is 25-30, it can be said that it is extremely high black.

  On the other hand, when observed microscopically with SEM or the like, it can be confirmed that the size of the roughened particles is 0.6 μm or less. It is important to adjust the size of the roughened particles to 0.6 μm or less. If the particle size exceeds 0.6 μm, the adhesiveness between the copper foil and the copper-tin roughened particles may be deteriorated. There may be problems such as remaining. In addition, the composition of the roughened layer made of copper-tin is also important. When the content of tin is 0.5 to 6.0 wt%, more preferably 0.8 to 5.0 wt%, the appearance, the roughness of the rough surface, and the specular gloss It becomes a roughening process layer which satisfies these simultaneously. If the tin content is less than 0.5 wt%, the appearance of the treatment may be brown, and the adhesion of roughened particles may be messy.

  On the other hand, when the content rate of tin exceeds 6.0 wt%, there may be a problem such as powder falling off and unevenness in processing appearance. In addition, unlike the conventional roughening method, the roughening treatment of the present invention can suppress the increase of the rough surface roughness to a very low level, so that the rough surface roughness after the processing can be set to an extremely low roughness. is there. It is important to control the roughness of the rough surface to 1.5 μm or less. If it exceeds 1.5 μm, the transparency of the PET / adhesive after etching may be deteriorated, resulting in a problem that a clear image cannot be obtained. .

  Cobalt layer containing at least one of molybdenum and tungsten as disclosed in JP-A-61-13688 and tungsten as described in JP-A-2003-171781 as necessary after the roughening treatment comprising copper-tin of the present invention Alternatively, a nickel-phosphorous layer containing molybdenum, a cobalt and / or nickel layer containing germanium as described in JP-A-2003-298229, other heat-resistant / rust-proofing layers, chromate film layers, and silane coupling agent layers When applied, even better characteristics can be obtained.

  When a heat-resistant / rust-proof layer is applied, the heat discoloration resistance and oxidation resistance from the heat history received during the production of an electromagnetic wave shield filter is improved. Examples of bath composition and electrolysis conditions for forming a heat-resistant / rust-proof layer are given.

(Nickel layer)
Nickel sulfate hexahydrate 10-100g / L (particularly preferably 20-50g / L)
Trisodium citrate dihydrate 5-100 g / L (particularly preferably 20-60 g / L)
pH 3.0 to 10.0 (particularly preferably 4.0 to 7.0)

(Cobalt layer)
Cobalt sulfate heptahydrate 10-100 g / L (particularly preferably 20-50 g / L)
Trisodium citrate dihydrate 5-100 g / L (particularly preferably 20-60 g / L)
pH 3.0 to 10.0 (particularly preferably 4.0 to 7.0)

(Cobalt-molybdenum layer)
Cobalt sulfate heptahydrate 10-100 g / L (particularly preferably 20-50 g / L)
Disodium molybdate dihydrate 1-80 g / L (particularly preferably 5-50 g / L)
Trisodium citrate dihydrate 5-100 g / L (particularly preferably 20-60 g / L)
pH 4.0 to 10.0 (particularly preferably 5.0 to 7.0)

(Nickel-phosphorus-tungsten layer)
Nickel sulfate hexahydrate 10-100g / L (particularly preferably 20-50g / L)
Sodium hypophosphite monohydrate 0.1-10 g / L (particularly preferably 0.5-5 g / L)
Sodium tungstate dihydrate 0.1-20 g / L (particularly preferably 0.5-10 g / L)
Sodium acetate trihydrate 2-20g / L (particularly preferably 3-15g / L)
pH 3.0-5.5 (particularly preferably 3.5-5.0)

(Cobalt-nickel-germanium layer)
Cobalt sulfate heptahydrate 10-100 g / L (particularly preferably 20-50 g / L)
Nickel sulfate hexahydrate 10-100g / L (particularly preferably 20-50g / L)
Germanium dioxide 0.1-10 g / L (particularly preferably 0.3-3 g / L)
Trisodium citrate dihydrate 5-100 g / L (particularly preferably 20-60 g / L)
pH 3.0 to 10.0 (particularly preferably 4.0 to 7.0)
Moreover, you may add sodium sulfate as provision of electroconductivity.

(Electrolysis conditions)
Current density 0.1 to 10.0 A / dm ² (particularly preferably 0.5 to 5.0 A / dm ² )
Electricity 5.0 ~ 40.0A ・ sec / dm ² (Preferably 10.0 ~ 30.0A ・ sec / dm ² )
Liquid temperature 20-50 ° C (particularly preferably 25-40 ° C)

When a chromate film layer is applied, properties such as oxidation resistance and adhesive strength are improved. The bath for forming the chromate film layer may be a known bath, and may be any bath having hexavalent chromium such as chromic acid, sodium dichromate, potassium dichromate and the like. Incidentally, precipitation form of chromium after chromate film layer formed is in a state in which Cr (OH) ₃ and Cr ₂ 0 ₃ are mixed, is precipitated in the form of trivalent chromium not adversely affect hexavalent chromium on the human body . Examples of the bath composition and electrolysis conditions for forming the chromate film layer are given.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
Current density 0.5A / dm ²
Electrolysis time 5 seconds

In addition, an alkaline zinc chromate solution containing zinc ions and hexavalent chromium ions described in Japanese Examined Patent Publication No. 58-15950 may be used. By using this chromic acid solution, a chromate film layer from a single acid solution of chromium is used. Can also improve oxidation resistance.

When a silane coupling agent layer is applied, properties such as oxidation resistance, adhesive strength, and adhesive strength after severe testing are improved. There are various types of silane coupling agents such as epoxy group, amino group, mercapto group, vinyl group, methacryloxy group, styryl group, etc., but each has different characteristics, and it is compatible with the base material, so it is necessary to select it. is there.

Examples of the bath for applying the silane coupling agent layer include the following composition and conditions.
γ-Aminopropyltriethoxysilane 2mL / L
Bath temperature 30 ° C
Immersion time 15 seconds

  Examples of the present invention will be described below.

(Examples 1 to 10)
A 12 μm electrolytic copper foil prepared by the manufacturing method described in JP-A-2004-263289 was prepared. The copper foil is glossy on any surface in an untreated state, but the roughness Rz (ten-point average roughness) of each surface is different, and plating generally called rough surface, mat surface, non-drum surface, etc. Rz of the end surface is 0.84 μm, and Rz of the plating start surface called smooth surface, glossy surface, shiny surface, drum surface, etc. is 1.12 μm. Hereinafter, the plating end surface of the electrolytic copper foil is referred to as a rough surface, and the plating start surface is referred to as a smooth surface.

First, the untreated copper foil was immersed in a sulfuric acid solution having a sulfuric acid concentration of 100 g / L and a bath temperature of 30 ° C. for 60 seconds to remove the oxidized layer on the surface and washed with water. Next, a roughening layer made of copper-tin was applied by cathodic electrolysis using platinum as the anode under the bath composition and electrolysis conditions shown in Table 1. The copper foil surface that has been subjected to the roughening treatment is also shown in Table 1. After washing with water, it was immersed in a rust preventive solution having the following bath composition for 10 seconds.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
After washing with water, drying was performed.

Tin content (wt%), rough surface roughness Rz, rough particle size, color difference L ^* , mirror surface in the copper-tin roughening layer of the copper foil subjected to the surface treatment of Examples 1 to 10 The results of measuring the glossiness Gs (85 °) are shown in Table 2. In addition, the tin content (wt%) in the copper-tin roughening layer of the copper foil was measured using RIX2000 manufactured by Rigaku Corporation, and the roughness Rz was determined based on JISB0601. Measured using a coder SE1700α, color difference L ^* is measured using a spectrophotometer CM-508d manufactured by Minolta Co., Ltd. It was measured using a Gloss 268 type, and the coarse particle size was measured from a photograph taken with an electron microscope (magnification × 10000).

Comparative example

(Comparative Examples 1-4)
Except that stannous pyrophosphate was not added to the electrolytic bath for forming the roughening layer made of copper-tin, electrolytic treatment and rust prevention treatment were performed in the same manner as in Examples 1 to 10, and the same characteristics were the same. Measured by the method. Table 1 shows the bath composition and electrolysis conditions. The copper foil used was the same as in Examples 1 to 10, and as shown in Table 1, Comparative Examples 1 and 2 were rough surfaces, and Comparative Examples 3 and 4 were surface treatments on smooth surfaces. went. Tin content (wt%), rough surface roughness Rz, rough particle size, color difference L ^* , mirror surface in the copper-tin roughening layer of the copper foil subjected to the surface treatment of Comparative Examples 1 to 4 The results of measuring the glossiness Gs (85 °) are shown in Table 2.

(Comparative Examples 5 and 6)
The roughening process layer which consists of copper-tin was not performed, but only the antirust process was performed using the same antirust liquid as Examples 1-10. In addition, although the used copper foil used the same thing as Examples 1-10, and also shown in Table 1, the comparative example 5 performed the antirust process on the rough surface and the comparative example 6 performed the smooth surface. Table 2 shows the results of measuring the roughness Rz, roughening particle size, color difference L ^* , and specular glossiness Gs (85 °) of the copper foils subjected to the surface treatment of Comparative Examples 5 and 6.

(Comparative Example 7)
Using the same untreated copper foil used in Examples 1 to 10, the copper foil was immersed in a sulfuric acid solution having a sulfuric acid concentration of 100 g / L and a bath temperature of 30 ° C. for 60 seconds to remove the oxide layer on the surface, Washed with water. Next, cathodic electrolysis was performed using platinum as the anode under the following bath composition and electrolysis conditions, and a roughened layer was formed on the rough side of the untreated copper foil.

(Bath composition)
Copper sulfate pentahydrate 50g / L
Zinc sulfate heptahydrate 58g / L
Sodium molybdate dihydrate 2g / L
Anhydrous sodium sulfate 14g / L
pH 1.9
Bath temperature 30 ℃

(Electrolysis conditions)
Current density 6.0A / dm ²
Electrolysis time 2 seconds After the roughened layer was formed, it was immediately washed with water. Then, cover plating was performed by cathodic electrolysis using platinum as the anode under the following bath composition and electrolysis conditions.

(Bath composition)
Copper sulfate pentahydrate 135g / L
Sulfuric acid 100g / L
Bath temperature 40 ℃

(Electrolysis conditions)
Current density 3.0A / dm ²
Electrolysis time 8 seconds After the cover plating was formed, it was immediately washed with water. Subsequently, cathode plating was performed using platinum as an anode under the following bath composition and electrolysis conditions to form an alloy plating layer.

(Bath composition)
Nickel sulfate hexahydrate 13g / L
Tin pyrophosphate 3g / L
Sodium molybdate dihydrate 12g / L
Potassium pyrophosphate 33g / L
Glycine 4g / L
pH 8.0
Bath temperature 30 ℃

(Electrolysis conditions)
Current density 3.0A / dm ²
Electrolysis time 8 seconds Immediately after the alloy plating layer was formed, it was washed with water. Subsequently, it was immersed for 10 seconds in the antirust liquid of the following bath compositions.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
After washing with water, drying was performed.

Table 2 shows the results of measurement of the roughness Rz, roughening particle size, color difference L ^* , and specular glossiness Gs (85 °) of the copper foil subjected to the surface treatment of Comparative Example 7.

As shown in Table 2, the copper foil having the roughened layer made of copper-tin of Examples 1 to 10 of the present invention has a color system L ^* a ^* b ^* of L ^* a ^* b ^* described in JISZ8729 of 30 or less. It is found that the color is extremely close to black, and the roughness Rz is ultra-low roughness of 1.5 μm or less, and the specular gloss Gs (85 °) is 80 or more, roughening. It can be seen that the particles are very fine. When a plasma display electromagnetic wave shielding filter is produced using the copper foil of this example, reflection from outside light can be suppressed, a sufficient contrast effect can be obtained, and furthermore, a highly accurate mesh can be formed by etching. It can be seen that a clear image with high transparency after etching is obtained (a rough surface electron micrograph of Example 6 is shown in FIG. 1).

On the other hand, in the case of Comparative Examples 1 to 4 in which stannous pyrophosphate was not added to the bath for forming the roughened layer made of copper-tin, L ^* was 30 because it was a roughened layer of copper alone. Exceeds the appearance of brown and does not reach black. In addition, the adhesion state of the roughened particles is messy, especially in the case of smooth surface side treatment, the specular gloss Gs (85 °) becomes a remarkably low value, and the transparency of the PET / adhesive after etching deteriorates (Fig. 2 shows a rough surface electron micrograph of Comparative Example 4). In the case of Comparative Examples 5 and 6 where the roughening layer made of copper-tin was not applied, a high value of specular gloss Gs (85 °) was obtained, but the color tone was copper and the reflection of light was suppressed. It is not possible to obtain a clear image.

In addition, Comparative Example 7 in which a roughening layer made of copper particles was formed on the surface of the copper foil and then an alloy plating layer made of tin-nickel-molybdenum was used, and L ^* was too high to obtain a sufficient black color. In addition, it can be seen that the rough surface roughness is increased by the roughening treatment, so that the specular gloss Gs (85 °) is low and the transparency of the PET / adhesive after etching is deteriorated.

In the present invention, a roughened particle layer made of roughened particles made of copper-tin having a roughened particle size of 0.6 μm or less is applied to at least one surface of the copper foil, and the rough surface roughness Rz is 1.5 μm or less. in the by adjusting, JISZ8729 the color of a color system L ^* a ^* b ^* according L ^* is 30 or less, and, specular gloss measured at Gs (85 °) based on JISZ8471 over 80 A copper foil for a plasma display electromagnetic wave shielding filter and a method for producing the same. When an electromagnetic wave shielding filter is produced using the copper foil, electromagnetic waves can be effectively shielded, and reflection from external light can be prevented. Since it can be suppressed to a very low level, the contrast effect is high and a clear image can be obtained, and since the etching property is good, a high-accuracy mesh is obtained, and the transparency of the PET / adhesive after etching is obtained. Features such as high image quality and clear images It becomes an electromagnetic wave shield filter having.

  Furthermore, the surface-treated copper foil of the present invention has features such as having fine roughened particles and ultra-low roughness, so it is not only for general copper foils for printed wiring boards but also for high-frequency substrates. Suitable for copper foil, copper foil for liquid crystal polymer, and copper foil for 2-layer flexible substrate.

Example 6 Surface treatment copper foil treated surface side electron micrograph of the present invention Comparative Example 4 Surface-treated copper foil treated surface side electron micrograph

Claims (3)

From copper-tin, the L * of the color system L * a * b * of the color described in JISZ8729 is 30 or less, and the specular gloss measured by Gs (85 °) is 80 or more based on JISZ8471 A roughening treatment layer is formed on at least one surface of the copper foil, the content of tin in the roughening treatment layer is 0.5 to 6.0 wt%, the balance is a composition made of copper, and roughening particles The copper foil is characterized by having a size of 0.6 μm or less and a ten-point average roughness Rz after forming the roughening treatment layer is 1.5 μm or less. The coating layer containing at least one or more of nickel, molybdenum, tungsten, cobalt, phosphorus, copper, germanium, chromium, and zinc is provided on the roughened layer made of copper-tin. Copper foil. A coating layer containing at least one of nickel, molybdenum, tungsten, cobalt, phosphorus, germanium, chromium, and zinc is provided on the copper-tin roughening layer, and a silane coupling agent layer is provided on the coating layer. The copper foil according to claim 1 or 2, characterized by the above-mentioned.

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