KR100343592B1 - Methods of plating on insulating substrates and plating grants obtained by the methods - Google Patents

Abstract

It is an object of the present invention to provide a method capable of easily producing a thin layer of a metal having good adhesion to a substrate on an insulating substrate having a smooth surface at low cost, and a plating imparting material obtained by the method.

The present invention provides a method of plating on an insulating substrate, comprising: forming a conductive film containing an oxide on an insulating substrate, and performing a reduction treatment on the conductive film surface layer to form a reducing layer on the conductive film surface layer. And a step 3 of forming a catalyst layer on the surface of the reduced layer by applying a treatment solution containing ions of a metal having a catalytic action to the reducing layer, and plating metal on the conductive film having the catalyst layer. Characterized in that it holds.

Description

Method of plating on insulating substrate and plating additive obtained by the method

The present invention provides a method of forming a highly conductive metal layer on an insulating substrate such as glass, plastic, ceramic, and the like, and a plating additive obtained by the method, for example, a circuit having a metal wiring having a fine pattern width. It relates to a substrate and a color filter.

As a method of forming a conductive film on a non-conductive insulating substrate such as glass, plastic, ceramic, or the like, physical vapor deposition or chemical vapor deposition is generally used. Among them, a vacuum deposition method or a sputtering method is generally used as a physical vapor deposition method. Materials used for the conductive thin film include chromium, aluminum, gold, carbon, platinum, copper and palladium. Commonly used at present are chromium and aluminum. Moreover, these methods are also used as a method of forming ITO (oxide of indium and tin) widely used as a transparent conductive film, such as a display element. Chemical vapor deposition is a method of forming a film on a substrate by reacting the gas at a high temperature. This method is used for film formation, such as a nesa film | membrane. As another method of forming a conductive thin film on an insulating substrate, there is a method of metallizing the surface of an insulating substrate by electroless plating. In this case, first, a catalyst such as palladium or platinum is adsorbed on the surface of the substrate, and then the metal is plated. However, in order to obtain a firm bond with the substrate, it is common to roughen the surface to be plated in advance. .

The method of forming a metal thin film by physical vapor deposition has a high processing temperature and takes time to form a film depending on the type of metal, and therefore, the type of metal actually used is limited and its versatility is low. In the case of chromium and aluminum which are commonly used at present, there are problems in terms of productivity and manufacturing cost due to device cost, target life and maintenance thereof. Moreover, when using a metal thin film as a black matrix for color filters of LCD (liquid crystal display) (chromium is generally used as the metal). It is required to remove light leakage due to the presence of pinholes and to make a film having low reflectance. However, in order to meet these demands, heavy deposition and blackening are required to increase the manufacturing cost. It is not necessarily satisfactory as the reflectance obtained at the same time. The method for producing an ITO film widely used as a transparent conductive film by sputtering method has a fast film forming speed, a uniform film forming technology is established, and is produced in large quantities and advantageous in terms of manufacturing cost. The conductivity is low and insufficient for the purpose of requiring high conductivity as much as metal. The film formation in the chemical vapor deposition method is also limited in practical use and is insufficient for the purpose of requiring high electrical conductivity as much as metal.

As a method of obtaining a highly conductive metal film by electroless plating, plating of copper, nickel, or the like is possible, and is effective for the purpose of requiring high conductivity. In this case, however, in order to obtain adhesion between the plated metal film and the substrate surface, the substrate surface must be roughened by some method, and the roughening of the substrate surface requires transparency such as glass. It is not suitable for the purpose or for the purpose where surface smoothness is required. Moreover, even if surface roughening is performed, the obtained adhesive strength is not enough. In recent years, for the purpose of forming a fine conductive wiring pattern or the like on the substrate surface, there is a case where the roughness of the substrate surface is inappropriate depending on the required precision of the pattern. The present invention provides a method capable of easily producing a thin layer of metal with good adhesion to a substrate on an insulating substrate having a smooth surface, and a plating imparting material obtained by the method.

According to the method of the present invention, the step 1 of forming a conductive film containing an oxide, such as an ITO conductive film, on an insulating substrate (surface shape does not matter. It may be a three-dimensional shape) and the above-described conductive film surface layer is reduced. Step 2 of forming a reducing layer on the surface of the conductive film, and a process 3 of forming a catalyst layer on the surface of the reducing layer by operating a treatment liquid containing a metal ion having a catalytic action on the reducing layer. The process 4 of plating a metal on the conductive film which has a catalyst layer is characterized by holding.

The present invention is characterized in that steps 2 and 3 are performed before metal plating on the insulator opening.

According to the method of the present invention, first, in step 1, a conductive film containing an oxide is strongly adhered on an insulating substrate.

Next, in Step 2, the oxide of the surface layer portion of the conductive film is reduced. For example, in the case where the conductive film is ITO, tin and indium of the film surface layer are reduced to form a layer of a mixture of oxidized water between tin and tetravalent, and indium between zero and trivalent. The reduced layer (reduction layer) can control its thickness and composition by the composition, thickness, and film forming conditions of the conductive layer formed in step 1 and the reducing conditions in step 2, and the surface modification of the conductive film can be controlled. (This is related to the adhesion strength of the plated film, the color tone and reflectance when viewed from the insulating base side) can be easily performed. Even if the surface of the conductive film is subjected to a roughening treatment (for example, treatment with a chemical solution such as boron hydrofluoric acid, hydrochloric acid, or hydrobromic acid) without conducting this step 2, the conductive film surface is obtained. The adhesion between the plated film and the insulating substrate is not sufficient.

Also, in Step 3, when the treatment liquid containing the metal ions having a catalytic action is brought into contact with the reducing layer, the metal ion contains the metal or the metal by the compound or element in the reduced state included in the reducing layer. Is reduced to (for example, when a treating solution containing ions of a catalyzed metal is used as an aqueous palladium chloride solution, it becomes fine particles of metal palladium). It selectively precipitates in particulate form only on the surface on which the reducing layer is formed. It is considered that the fine particles having such a catalytic action have a strong bond with the remaining conductive film surface layer.

When the metal film is deposited on the surface of the conductive film which has passed through Steps 2 and 3 by the plating treatment of Step 4, the metal film is strongly adhered to the surface of the insulating base. According to the method of applying catalysis particles to the surface of the insulating substrate which has undergone the process 1 to process 3, a part of the conductive film formed on the surface of the substrate at the molecular level by sputtering or the like is reduced, and the reduced part and the process liquid Since the ions of the catalyzed metal react directly with the solid-liquid contact reaction, the catalyzed fine particles generated in the treatment liquid and the remaining reducing layer used for reducing them are bonded at the molecular level, and the reducing layer itself It is also considered that the bonding is performed at the molecular level continuously with the underlying conductive film layer. On the other hand, since the bonding of the palladium / tin colloidal catalyst or the palladium compound catalyst to the substrate surface which is generally used in the plating method of the insulating substrate surface by the conventional method is due to the physical adsorption force, the bonding strength is weak, and it is necessary to obtain the adhesion of the corresponding plating film. Must use the anchor effect by surface roughening (although not enough bonding).

Hereinafter, the present invention will be described in more detail with reference to FIGS. 1 to 4, which show one embodiment of the method of the present invention in the order of the process.

In the method of this invention, the electrically conductive film 2 is first formed in one surface of the insulating base material 1 with a smooth surface (FIG. 1 (a)). For the formation of the conductive film 2, sputtering, vapor deposition, or the like can be used. According to these, strong adhesion between the conductive film 2 and the insulating base 1 is obtained, and the surface of the substrate is not required as in the conventional plating method. Therefore, it can fully cope with the patterning of fine line width of 30 micrometers or less.

Here, as the board | substrate 1, glass, a plastic, a ceramic, etc. are used (when using a plating provision product as a color filter, it is further necessary that the board | substrate itself should be transparent). As the conductive film 2, the final electroconductivity is secured by forming a metal plated film later on the conductive film 2, and therefore, the conductive film 2 is selected from a material having high conductivity unlike the case of the conductive film formation by the conventional metal spatter method. There is no need to do it. In the case where the reduction is carried out by electrolytic treatment in the electrolytic solution in step 2, it is sufficient that the electroconductivity is sufficient to allow the electrolytic treatment. Therefore, what is necessary is just to select the low cost material which is good in productivity and workability in selecting a conductive film formation material. The most representative material is ITO.

In process 2, the conductive film surface layer is reduced. As this method, although the method of dry reduction in ion plasma atmosphere or high temperature atmosphere containing an element or compound which can reduce an electrically conductive film is mentioned, for example, the method by the electrolytic treatment in electrolyte solution is preferable. In the case of the electrolytic treatment, the degree of reduction can be adjusted by the electrolytic conditions. In said electrolytic treatment, electrolyte solution contains at least 1 sort (s) of arbitrary electrolytes for adjusting conductivity. Examples thereof include lactic acid, glycolic acid, methoxy acetic acid, acetic acid, chloroacetic acid, citric acid and tartaric acid.

And it is practically preferable to mix | blend the inhibitor for making electrolytic treatment uniform to this electrolyte solution. In this case, on the conductive film 2, a layer (inhibitor layer) 3 based on an electrolyte component (mainly an inhibitor component) is formed on the other of the reducing layer 4. (Fig. 1 (b)).

As the inhibitor, a polymer colloid having a polar group used for ordinary electrodeposition coating or the like can be used. In this case, electrolysis results in poly-colloids being deposited on the surface of the reducing layer 4, thereby forming a poly-polymer film 3 (a representative example of the layer based on the electrolyte solution). In this case, when an electrodeposition photoresist in which a photopolymerization initiator is added to the polymer colloid is used, the formed film can be patterned by a photo method. As a result, the inhibitor layer 3 of the desired portion (the portion to be plated) is removed, so that the removal of the inhibitor layer 3 (FIG. 1 (c)) in the following process becomes unnecessary. Examples of the inhibitor include an acrylic resin having a cationic group, an epoxy resin having a cation group, a urethane resin, a polyamide resin, and the like.

Next, if there is a layer based on the component contained in the electrolyte, such as the inhibitor layer 3, the layer is removed by a solution (solvent) that can be dissolved and removed, for example, an organic solvent, an acid / alkali solution, or the like (first (C)), the treatment liquid containing ions of the catalyzed metal is acted on the reducing layer 4. [Step 3]. By this treatment, the reducing layer 4 (for example, reduced tin) of the conductive film 2 surface layer reduces the metal ions so as to precipitate the catalyst layer 5 on the conductive film 2 (FIG. 1 (d)). ).

As the treatment liquid containing ions of the metal having the action of a catalyst, any one can be used as long as it can be reduced by the reducing layer 4 and precipitate a metal or a compound containing the same as the plating catalyst. For example, an aqueous solution of a compound containing a non-zero oxidized metal (palladium, platinum, rhodium, etc.) may be used. In the case where the metal ion is palladium, more specifically, an aqueous solution of a monomolecular compound such as a palladium chloride or a palladium coordination compound (e.g., a palladium ammine complex), a multimer thereof, or a cluster compound can be used.

The concentration of the treatment liquid and the treatment time may be appropriately selected. In the case of the palladium chloride aqueous solution, the palladium is about 30 mg / l to 80 mg / l, and the treatment time is about 30 seconds to 5 minutes.

In addition, between the necessary steps 3 and 4, an etching resist is applied on the conventional patterning method, ie, the conductive film 2 having the catalyst layer 5 to form the layer 7 (FIG. 1 (e)), and the exposure ( The etching of the conductive film (FIG. 1 (g)) by the resist imaging (FIG. 1 (f)) and the exfoliation of the remaining resist (FIG. 1 (h)) due to exposure and development are performed. As an essential procedure 4, it is possible to apply plating only to desired parts (Fig. 1 (i)).

In step 4, a metal, such as copper or nickel, is deposited on the catalyst layer 5 by plating (preferably electroless plating) to form a metal plating film 6. (Fig. 4, a circuit requiring high conductivity here) In the case of the metal wiring of a board | substrate, nickel is preferable in the case of the black matrix for color filters of LCD which requires low reflectance). Depending on the purpose, a single metal or a plurality of metals are precipitated.

In the method of the present invention, in Step 3, the catalyst layer 5 is formed on the surface of the conductive film 2, but the bonding between the catalyst layer 5 and the conductive film 2 (via a reduction layer or directly) is secured, and the catalyst layer 5 and Since the bond with the metal plating film 6 by plating is also announced, the adhesiveness of the metal plating film as a whole is remarkably high. The drawback of low adhesiveness after film formation in der electroless plating can also be eliminated by the method of the present invention.

Moreover, the light leakage by the pinhole etc. which became a problem in the case of the black matrix for color filters of the conventional LCD cannot be recognized because the precipitation state of a metal plating film is very good. In addition, in the case where an ITO film is used as the conductive film and an electroless Ni plating is used as the plating, a low-reflectance plating impartment which can not be achieved in the conventional sputtering film of Cr can be obtained. In addition, when ITO is used as the conductive film forming material, the material cost is lower than that of the conventional method, that is, the sputtering of Cr, and the sputtering is simple, so the conductive film forming cost is much lower than that of the conventional method.

In addition, according to the method of the present invention, by changing the thickness of the conductive film formed in step 1, it is possible to adjust the color tone of the surface of the insulating substrate. (When the color tone is adjusted to black or black purple, contrast with good visibility is obtained. High burns). In addition, by adjusting the reducing treatment conditions in Step 2 or by adding alkali metal ions or alkaline earth metal ions to the reducing treatment liquid, the color tone and reflectance of the insulating substrate surface can be adjusted. Therefore, the plating additive obtained by the method of the present invention can be used as a black matrix for color filters of LCDs having low reflectance, that is, reflection of the screen is suppressed and high visibility.

In addition, when using the said plating additive as a black matrix for color filters of LCD, each coloring part R.G.B may be formed beforehand, and the part used as the black matrix may be formed after that. That is, the color resist of red (R), green (G), and blue (B) is patterned on the substrate (FIG. 1 (a)) on which the conductive film is formed (FIGS. 2 and 3), and then, Operations (b) to (d) and (i) shown in FIG. 1 are performed in this order. In this method, the reducing layer 4 or the inhibitor layer 3 as well as the catalyst layer 5 are not formed on each of the colored portions R, G, and B, and are formed only on the conductive film 2 exposed to the black matrix forming portion A. FIG. Therefore, the operations (e) to (h) shown in FIG. 1 become unnecessary, and the process is simplified. In this method, in order to increase the dimensional accuracy of the black matrix forming portion, it is necessary to accurately define the boundary with the black matrix forming portion A in advance at the time of forming the colored portions R, G, and B.

As another method, a method of leaving the black matrix forming portion and removing the conductive film in other portions when performing the reduction treatment on the conductive film in Step 2 is mentioned. In this method, after forming a photosensitive resin film (photosensitive resin, in this case, electrodeposition resist is mix | blended with electrolyte solution as an inhibitor) on the whole surface of an electrically conductive film part board | substrate by electrodeposition, exposure and image development are carried out. Patterning is performed to remove the resist film from portions other than the black matrix forming portion. (FIG. 4 (a)). In addition, after the reduction layer secondary conductive film in this portion is removed by etching (FIG. 4B), the resist film in the black matrix forming portion is removed (FIG. 4C). Thereafter, operation (d) shown in FIG. 1, that is, formation of the catalyst layer 5 and (i), side metal plating are performed in this order. In this method, since the conductive layer 2 as well as the reducing layer 4 is not included in the portion other than the black matrix forming portion at the time of forming the catalyst layer 5, the catalyst layer 5 is formed by forming the black matrix forming portion in which the reducing layer secondary conductive film remains. It is only. In this method, before the metal plating is carried out as in the above-described method, the etching resist is applied (FIG. 1 (e)) by patterning by photolithography (FIG. 1F) and etching ( Fig. 1 (g)) and peeling of the resist. Although there is an advantage in that it is not necessary to remove again, since etching is performed in the presence of a weak reducing layer 4 in the acid, there is erosion in the transverse direction. Therefore, it is not suitable when the formation of a fine pattern is required. Again, as another method, the treatment is performed until the step of applying the metal plating once, that is, after the operations (a) to (d) and (i) shown in Fig. 1 are performed in this order (Fig. 5). ), After forming a photosensitive resin (etching resist) film on the metal plating layer, exposure and development patterning are performed to expose a place other than the light shielding layer formation place, and then contact with the metal plating and the etching solution of the conductive film to contact the above. The metal plating and the conductive film of the exposed place may be removed, and the remaining resist film may be peeled off. Also in the conventional method (to the sputter of Cr), after the formation of the chromium film, each operation of forming the etching resist film-etching is performed, but in the conventional method, harmful chromium is contained in the waste liquid discharged as a result of etching. The inventive method has an advantage in that it is a metal that is not designated as a hazardous heavy metal, for example nickel.

Embodiment of the invention

As an insulating substrate, a glass substrate (400 mm × 320 mm) having a smooth surface was used. On one surface of this glass substrate 1, an ITO conductive film 2 (specific resistance 2 × 10 ⁻⁴ Ωcm) was formed by sputtering (FIG. 1 (a)). The film thickness of the ITO conductive film 2 was 1,500 kPa. Next, the electrolytic treatment was carried out in the electrolytic solution using the ITO conductive film 2 as a cathode, thereby reducing the conductive film surface layer. As the electrolyte and lactic acid, an electrolyte obtained by dispersing an acrylic resin having an amino group neutralized with lactic acid in the form of a colloid was used. As the acrylic resin, an electrodeposition photoresist (trade name: EAGLE ED-2100 manufactured by Schippfar East Co., Ltd.) was used in consideration of the peeling and removal of the inhibitor layer 3 in the next step. In other words, as an acrylic resin having an amino group, a composition containing a copolymer of methyl methacrylate, ethyl acrylate and dimethylamino ethyl methacrylate and dipentaerythritol pentaacrylate (in terms of weight, methyl methacrylate: Ethyl acrylate: dimethyl amino ethyl methacrylate = 75: 17: 8, copolymer: dipentaerythritol penta acrylate = 2: 1). The electrical conductivity of this electrolyte solution was 400 kV / cm, and electrolytic conditions were 40 degreeC, 100 volts, and 60 second.

By performing the electrolytic treatment, the surface layer of the ITO conductive film 2 is electrolytically reduced (the result formed is a "reduction layer" indicated by the sign 4) and at the same time by the precipitate 3 of the polymer which is an inhibitor component contained in the electrolyte solution. Sheathed. (FIG. 1 (b)). Thereafter, the polymer precipitate (inhibitor layer 3) was removed by using a developer (trade name: EAGLE RESIST DEVELOPER DE-2005 manufactured by Seaplay White Co., Ltd. (first (c)). The surface of the ITO conductive film 2 was It was recognized that the above electrolytic treatment colored brown and a part of the tin component and a part of the indium component of the ITO conductive film surface layer were reduced in. The ITO conductive film 2 having the reduced layer 4 in the surface layer was palladium chloride. It was immersed for 3 minutes in aqueous solution (The brand name: OMNISHIELD-1572 by Seaplay Pist Inc. is used by concentration 1.0 volume%), and the palladium catalyst layer 5 was formed in the surface of an ITO electrically conductive film (FIG. 1 (d)). In order to remove the tin component remaining in the palladium catalyst layer 5, the electrically conductive film which has the palladium catalyst layer in the surface layer was immersed in lactic acidic aqueous solution (The brand name: ACCELRATOR-240 by the company C. Pyfete.). After that, nothing To 7 minutes immersed in a Ni plating solution (30 ℃) and allowed to precipitate the Ni thin film of 2,000Å. (FIG. 5).

The plating additive mainly containing the plating film obtained as mentioned above had high electroconductivity and was also excellent in adhesiveness with a base material. As a result of the base wood peeling rest (JIS K 5400) of this plating provision, peeling was not seen at all and it was confirmed that it had high adhesive strength.

In addition, the thing which did not perform the reduction process of the electrically conductive film (other process is the same as this Example) did not form metal plating well by the process 4. In addition, the surface roughening of the ITO conductive film instead of the reduction treatment of the conductive film (other treatments are the same as in this example) is performed in step 4, but a thin film of metal plating is formed, but in the base wood peeling test (JIS K 5400), The thin film simply peeled off from the ITO film.

As for the low reflectance required for the black matrix for color filters, the sputtering of Cr is a reflectance of about 60% as it is, and the required performance cannot be sufficiently satisfied. Sputtering of CrO / Cr or Cro / Cr / Cr two-layer or three-layer Cr is necessary to obtain a light-shielding layer having a low reflectance only by sputtering of Cr, resulting in a high cost (high). Moreover, although the thing of the reflectance about 10% is obtained by this, the reflection color is red or bluish black. On the other hand, according to the method of the present invention, it is possible to obtain a low reflectance black membrane of 30% or less by setting the film thickness of the ITO film after the process in Step 3 from 500 kPa to 1500 kPa (the film thickness is 800-1,000 If it is set to Å, a reflectance of 20% or less is obtained. In addition, in step 2 (reduction treatment of the conductive film), if the amount of indium reduction in the ITO film is adjusted, that is, alkali metal ions or alkaline earth metal ions are added to the reduction treatment solution to increase the extreme current value in the reduction treatment, the reflectance is 5% or less. You can get

In addition, between steps 3 and 4, an etching resist 7 is applied on the catalyst layer 5 (FIG. 1 (e)), and the catalyst layer 5 and the reduced layer part ITO conductive film 2 are applied to the fine pattern by photolithography. After etching and processing (FIG. 1 (f)-(u)), it was put into a plating liquid, and a plating film was deposited only in a predetermined pattern, and plating provisions of various line widths were made (FIG. 1 (i)). The fine pattern of the line width of 5 micrometers was obtained.

As described above, according to the present invention, it is possible to form a metal thin film having high adhesion strength and high electrical conductivity at the same time without performing surface roughening of the substrate on a smooth insulating substrate. Moreover, it is possible to provide an inexpensive plating additive without involving the pollution treatment of chromium which is a problem in the sputtering method of Cr which is widely used at present. In addition, the plating additive obtained by the method of the present invention is free from pin holes, has a high light blocking rate and a low reflectance, and thus can be sufficiently used as a black matrix for color filters in LCDs.

1 is a cross-sectional view showing one state of the manufacturing method of the present invention in the order of process.

2 is a planar pattern diagram of a color filter.

3 is a cross-sectional view showing one step of another example of the manufacturing method of the present invention.

4 is a cross-sectional view showing one step of still another example of the manufacturing method of the present invention.

5 is a cross-sectional view showing one step of still another example in the manufacturing method of the present invention.

Explanation of symbols on the main parts of the drawings

1. Insulation substrate 2. Transparent conductive film (ITO film)

3. Inhibitor layer 4. Reduction layer

5. Catalyst layer 6. Metal plated film

7. Etching resist film

8. Electrodeposition Film

R. Red tinted layer G. Green tinted layer

B. Blue Colored Layer

Claims (15)

A process 1 of forming an oxide-containing conductive film on an insulating substrate, a process of reducing the conductive film surface layer to form a reducing layer on the conductive film surface layer, and a metal having a catalytic action in the reduction layer. A method of plating on an insulating substrate, which comprises a step 3 of forming a catalyst layer on the surface of the reducing layer by applying a treatment solution containing ions and a step 4 of plating a metal on the conductive film having the catalyst layer. The method according to claim 1, wherein a pattern by an etching resist film is formed on the catalyst layer formed in step 3 above, the catalyst layer secondary conductive film in an unnecessary portion is removed by etching, and then the remaining etching resist film is peeled off and remaining. The process of process 4 is carried out on the patterned catalyst layer secondary conductive film. The process according to claim 1, wherein in the above-described process 2, the formation of the reducing layer is performed by electrolytic treatment in an electrolytic solution containing an electrodeposition resist, and the exposure and development of the resist photosensitive resin film formed on the reducing layer. A method of patterning to expose a reduced layer of an unnecessary portion, and then removing the remaining conductive layer sub conductive film by etching to remove the remaining electrodeposition resist film. 2. The method according to claim 1, wherein a pattern by an etching resist film is formed on the metal plating layer formed in step 4, and the remaining metal plating and conductive film are removed by etching to remove the remaining etching resist film. 2. A method according to claim 1, wherein prior to the process of step 2, a colored film is formed at a place to be colored on a substrate in advance. The method according to any one of claims 1 to 5, wherein as the conductive film, an oxide of indium, an oxide of tin or a film of ITO is used. The method according to any one of claims 1 to 2 and 4 to 5, wherein the formation of the reducing layer is performed by an electrolytic treatment in an electrolyte solution. The method according to any one of claims 1 to 2 and 4 to 5, wherein the reduction layer is formed by dry reduction in an ion plasma atmosphere containing an element or compound capable of reducing the surface of the conductive film, or in a high temperature atmosphere. The method according to any one of claims 1 to 5, wherein the metal plating is performed by electroless plating. 10. The method of claim 9, wherein the electroless plating is an electroless plating of Ni. A plated additive of an insulating substrate made of a transparent insulating substrate, an ITO film having at least a reduced metal or metal compound on the surface thereof as a film deposited on the insulating substrate, and a metal plated film deposited on the surface of the ITO film. The plating additive according to claim 11, wherein the ITO film has a film thickness of 800-1,000 Pa. 12. The plating additive according to claim 11, wherein said metal plating film is Ni. The plating additive according to claim 11, wherein the metal plating film has a reflectance of 20% or less. The plating additive according to claim 11, wherein the metal plating film has a reflectance of 5% or less.