JP2019177311A - Millimeter wave-permeable decorative article, silver mirror film and its formation method - Google Patents

Abstract

To provide a silver mirror film having both brilliance and millimeter wave permeability; and to provide a decorative article including the same.SOLUTION: A formation method of a millimeter wave-permeable silver mirror film includes a step B for coating tin chloride on a substrate, followed by water washing, a step D1 for coating silver mirror film formation liquid on the substrate to form a part of the silver mirror film, followed by water washing, a step β for coating acid solution on the substrate, followed by water washing, and a step D2 for coating the silver mirror film formation liquid on the substrate to form again a part of the silver mirror film, followed by water washing. The silver mirror film is completed by repeating once or more a process from the step β to the step D2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a millimeter-wave transparent silver mirror film and a decorative article including the same.

  A bright (metallic luster) film may be formed on exterior resin parts such as radiator grills, back panels, and side moldings for automobiles due to its design. As the bright film, a metal plating film, a vacuum deposited film, or a metal Sputtering films are common.

  In addition, some recent exterior resin parts have a millimeter wave radar disposed on the inside thereof, and a property of transmitting millimeter waves (millimeter wave permeability) is required. High millimeter wave transmission means that the millimeter wave transmission attenuation is small. Based on the knowledge of metal sputtering films so far, it has been found that there is a correlation that the higher the surface resistance value, the smaller the millimeter-wave transmission attenuation, and the metal sputtering film has a high surface resistance value due to the discontinuous structure. Is obtained (Patent Document 1).

  However, it is difficult to uniformly form a metal plating film, a vacuum vapor deposition film, or a metal sputtering film on a three-dimensional radiator grill or the like having a deep recess that has been increasing in recent years.

  On the other hand, a silver mirror film is known as a bright film that can be uniformly formed on a deep three-dimensional product. The silver mirror film consists of innumerable fine silver particles, and the formation method is to apply a silver mirror film-forming solution consisting of a silver mirror solution and a reducing solution immediately after mixing the two solutions, and then the silver mirror reaction (reduction ) To precipitate silver particles (Patent Document 2). Patent Document 3 repeats spraying a silver mirror reaction treatment agent (a metal salt solution containing silver nitrate and a reducing agent solution) and an activation treatment agent (mixed solution of tin chloride and palladium chloride) almost simultaneously several times. Thus, there is disclosed a method for reducing the manufacturing time by eliminating the trouble of spraying separately.

Japanese Patent No. 4732147 Japanese Patent No. 4140368 Japanese Patent No. 4405143

  However, no silver mirror film has been studied for millimeter wave transmission. According to the study of the present inventor, neither the silver mirror film formed by the ordinary method nor the silver mirror film formed by the methods of Patent Documents 1 and 2 has millimeter wave permeability.

  Therefore, even if a uniform silver mirror film is formed on a deep three-dimensional automotive exterior resin part, the glittering property is obtained, but the millimeter wave permeability is not obtained.

  Then, the subject of this invention is providing the silver mirror film which has both luster and millimeter wave transmissivity, and a decoration provided with the same.

  The present inventor initially studied a method for forming a so-called half-gloss silver mirror film by performing a normal silver mirror reaction only for a short time or by making a silver mirror film-forming solution weak in silver mirror reaction. . However, in those methods, those with sufficient glitter cannot achieve millimeter wave transmission at all, and those with sufficient millimeter wave transmission do not have sufficient glitter, resulting in difficulty in solving the problem. Met. Therefore, a new method completely different from those methods was sought and the present invention was reached.

(1) Method of forming millimeter wave transmissive silver mirror film Step B of applying a tin chloride solution to a substrate and then washing with water;
A step D1 of applying a silver mirror film-forming liquid to the substrate to form part of the silver mirror film and then washing with water;
A step β of applying an acid solution to the substrate and then washing with water;
A step D2 of applying a silver mirror film-forming liquid to the substrate to form a part of the silver mirror film and then washing with water;
A method for forming a millimeter-wave permeable silver mirror film, wherein the process is repeated at least once from step β to complete a silver mirror film.

<Action>
As shown in FIG. 1 which is an image diagram of Examples 1 to 4 described later,
By the process B, tin fine particles adhere to the surface of the substrate.
By the process D1, silver particles adhere mainly to the surface of the base material starting from tin fine particles, and a part of the silver mirror film is formed. Since it is a part of the silver mirror film, the silver particles are small and often separated from each other. In addition, silver particles may adhere even where there are no tin fine particles.
By the step β, silver particles having a weak adhesion (particularly, silver particles adhering to a place where there is no tin fine particle) among the silver particles adhering in the step D1 (or D2) are removed, and the density of the silver particles is lowered.
By the process D2, silver adheres so as to cover the silver particles adhered in the process D1, and the silver particles become large. Some silver particles stick to each other, but many are still separated. In addition, silver particles may adhere even where there are no tin fine particles.
By repeating step β to step D2 one or more times, a silver mirror film having glitter and millimeter wave transparency can be completed.

(2) Millimeter-wave permeable silver mirror membrane L * a * b * color system L * value is 65 or more, and surface resistance is 1 × 10 ¹¹ Ω / □ or more (preferably 3 × 10 ¹¹ Ω / □) A silver mirror film having a millimeter-wave transmission attenuation of 2 dB or less.

(3) Millimeter-wave transparent decorative product The L * value of the L * a * b * color system formed on the base material and the surface of the base material is 65 or more, and the surface resistance value is 1 × 10 ¹¹ Ω / □ or more (preferably 3 × 10 ¹¹ Ω / □ or higher), and the millimeter wave transmitting decorative article millimeter wave transmission attenuation includes silver mirror and film is 2dB less.

  ADVANTAGE OF THE INVENTION According to this invention, the silver mirror film which has both luster and millimeter wave transmissivity, and a decoration provided with the same can be provided.

FIG. 1 is an image diagram of the first to fourth embodiments. FIG. 2 is an image diagram of Comparative Example 1. 3A is a SEM photograph of the surface of Example 2, and FIG. 3B is a SEM photograph of a cross section. 4A is a SEM photograph of the surface of Example 3, and FIG. 4B is a SEM photograph of a cross section. 5A is a SEM photograph of the surface of Comparative Example 1, and FIG. 5B is a SEM photograph of the cross section. FIG. 6 is an SEM photograph of the surface of Comparative Example 2. 7A is a SEM photograph of the surface of Comparative Example 5, and FIG. 7B is a SEM photograph of the cross section. FIG. 8 is an SEM photograph of the surface of Comparative Example 6. FIG. 9 is an SEM photograph of the surface of Comparative Example 9.

1. Step Before Step B Before Step B, a step (Aa) of forming an undercoat layer for improving cushioning properties, smoothness, adhesion to the substrate, and the like may be performed.
Moreover, you may perform the plasma treatment process (Ab) for improving wettability, adhesiveness with a base material, etc. before the process B. FIG.

2. Process C between Process B and Process D1
Between the process B and the process D1, you may perform the process C which apply | coats and osmose | permeates a modified siloxane as a surface conditioner.

3. Process β
When the tin chloride solution in step B is an acid solution, the tin chloride solution in step B may be used for step β, or step B may be performed as step β. In addition, step β may be performed with an acid solution other than the stannic chloride solution.

4). Process D1 and Process D2
The process D1 and the process D2 are common in that a part of the silver mirror film is formed, but the content of each process may be the same or may be different in the silver mirror film forming liquid, the coating amount, and the like.

5. Step after the last step D2 After the last step D2, the silver mirror film is subjected to corrosion prevention treatment (step E) for the purpose of removing unreacted silver mirror film and stabilizing silver (preventing discoloration). Also good.
Furthermore, after the step E, a step F for forming a topcoat layer may be performed for the purpose of protecting the silver mirror film or the like.

6). Base material The material of the base material is not particularly limited, and examples thereof include resin, glass, ceramics, and wood.

7). Decorative products Decorative products (uses) are not particularly limited, but automotive exterior resin parts with millimeter-wave radar devices inside are suitable. Radiator grille, grill cover, side molding, back panel, bumper, emblem Etc. can be illustrated.

  Examples 1 to 4 and Comparative Examples 1 to 9 of decorative articles made of a base material, an undercoat layer, a silver mirror film, and a top coat layer were produced by the method described in the following Table 1 and the process described in the process description. As the substrate, a plate-shaped substrate made of ABS resin and having a size of 100 mm × 100 mm × thickness 3.0 mm was used.

  The steps are performed in order from the left to the right (except for the blank) in which the number of times (mostly 1) is entered in the column of Table 1, but in Examples 1 to 4, a part of the silver mirror film is formed. After Step D1, Step D, Step C, and Step D2 for forming a part of the silver mirror film are repeated a plurality of times as β → C → D2 → β → C → D2 → ... to complete the silver mirror film. . FIG. 1 shows an image diagram of the first to fourth embodiments.

  On the other hand, in Comparative Example 1, a metallic gloss (full gloss) silver mirror film is formed in one step Da. In Comparative Examples 2 to 5, a semi-glossy (half gloss) silver mirror film is formed in one step Db. In Comparative Examples 6 to 9, a semi-glossy (half gloss) silver mirror film is formed in one step Dc. FIG. 2 shows an image diagram of the comparative example.

  Hereinafter, details of each process will be described. In addition, materials, blending amounts, conditions, and the like in each step are examples and can be changed as appropriate.

(Process Aa) Undercoat (all examples other than Example 4)
An undercoat solution was applied to the substrate to form an undercoat layer.
The following main ingredients, curing agents, diluents and leveling agents were used as materials for the undercoat liquid.
・ Main agent: Product name “MFS undercoat main agent”, product number “MFS-51” of Surface Chemical Research Laboratory (acrylic resin 40%, toluene 21.5%, xylene (mixed) 16.5%, isobutyl acetate 22% blend)
・ Curing agent: Product name “MFS undercoat curing agent 21”, product number “MFS-52AK21” (mixture of 60% isocyanate prepolymer and 40% ethyl acetate)
・ Diluent: Product name “MFS undercoat diluent”, product number “MFS-53” (3.0% toluene, 23.4% xylene, 12.6% ethylbenzene, 25-30 butyl acetate) %, Ethyl acetate 5-10%, methyl isobutyl ketone 1-5%, diacetone alcohol 10-15%, ethylene glycol monoethyl ether acetate 14.0%)
Leveling agent: Product name “MFS undercoat leveling agent”, product number “MFS-58” (2% polysiloxane and anti-waxing agent, 12% 1,3,5-trimethylbenzene, 1, 2) , 4-trimethylbenzene 28%, 1,2,3-trimethylbenzene 5%, ethylbenzene 24%, xylene 4%, diisobutyl ketone 15%, butyl glycolate 3%).

These main agents: curing agent: diluent: leveling agent were mixed at a mass ratio of 100: 20: 60 to 100: 3 to 5, and spray-coated on the surface of the substrate with a spray gun.
After application, the film was held at 65 ° C. for 30 minutes in a thermostatic bath, cured and dried to form an undercoat layer having a film thickness of 15 to 25 μm.
Then, it washed with ion-exchange water.

(Process Ab) Plasma treatment (only Example 4)
The substrate was subjected to plasma treatment under the conditions of RF 100 W · O ₂ process gas 50 sccm · 60 seconds using a sputtering apparatus i-miller II manufactured by Shibaura Mechatronics.

(Process B) Surface adjustment 1 (all examples)
For the purpose of promoting silver precipitation and improving adhesion, the surface conditioning liquid 1 was sprayed to adjust the surface of the substrate or the undercoat layer.
As materials for the surface conditioning liquid, the following surface conditioning agents a and b were used.
-Surface modifier a: Product name "MFS surface modifier A" product number "MFS-40A" (aqueous solution of stannous chloride to 10%, hydrochloric acid to 5%) of surface chemical research institute with ion-exchanged water It was diluted 15 times (example: surface conditioning agent A 10 mL, ion exchange water 140 mL).
-Surface modifier b: Product name "MFS surface modifier B" product number "MFS-40B" (sodium salt to 1% aqueous solution) of Surface Chemical Laboratory Ltd. was diluted 15 times with ion-exchanged water (example; (Surface conditioner B10mL, ion-exchanged water 140mL)

These surface conditioner a: surface conditioner b were mixed at a mass ratio of 1: 1 to prepare surface conditioner No. 1 and sprayed on the surface of the undercoat layer with a spray gun for 5 seconds.
Thereafter, the mixture was allowed to stand for 10 seconds for permeation, washed with ion exchange water, air dried, and washed again with ion exchange water.

(Process C) Surface adjustment 2 (all examples)
Furthermore, for the purpose of improving adhesion, the surface adjustment liquid 2 was sprayed to adjust the surface of the substrate or the undercoat layer.
The following surface conditioning agent c was used as the material for the surface conditioning liquid.
-Surface modifier c: The product name "MFS surface modifier C" product number "MFS-40C" (modified siloxane) of Surface Chemical Laboratory Ltd. was diluted 50 times with ion-exchanged water (example: surface modifier C5mL, Ion-exchanged water (245 mL).

The surface conditioning solution 2 prepared in this way was sprayed on the surface of the undercoat layer for 2 seconds with a spray gun.
Thereafter, it was allowed to stand for 10 seconds to allow penetration.

(Process D1) Silver mirror film (Examples 1 to 4 only)
A silver mirror film-forming solution was applied to the base material (after undercoating or plasma treatment) (silver mirror coating) to form a part of the silver mirror film.
The following silver main liquid, silver secondary liquid, and reducing liquid were used as materials for the silver mirror film forming liquid.
・ Silver main liquid: Product name “MFS silver main liquid”, product number “MFS-10” (Aqueous solution of silver nitrate 8.4%, ammonium hydroxide -5%)
・ Silver secondary liquid: Product name “MFS silver secondary liquid” of Surface Chemical Laboratory, product number “MFS-20” (aqueous solution of caustic soda to 10%, ammonium hydroxide to 5%)
・ Reducing liquid: Product name “MFS reducing agent” of Surface Chemical Laboratory, product number “MFS-30” (polysaccharide 5-15%, hydrochloric acid-5% aqueous solution)

The silver main solution is diluted 15 times with ion-exchanged water (eg; silver main solution 5 mL, water 70 mL), and the silver sub-solution is diluted 15 times with ion-exchanged water (eg; silver auxiliary solution 5 mL, water 70 mL). The diluted solution was mixed to prepare a silver mirror solution.
The reducing solution was diluted 30 times with ion-exchanged water (eg, reducing solution 5 mL, water 145 mL) to prepare a reducing solution (diluted solution) containing 0.085 to 0.258 mol / L of aldehyde.

These silver mirror solution and reducing solution were sprayed simultaneously with a two-head spray gun, mixed in the air, and applied to the surface of the undercoat. The spray application time was 3 seconds in Examples 1 and 4, 4 seconds in Example 2, and 5 seconds in Example 3.
On the undercoat, silver particles were precipitated by the following silver mirror reaction formula to form a silver mirror film.
R—CHO + 2 [Ag (NH ₃ ) ₂ ] ⁺ + 2OH ⁻
→ R-COOH + 2Ag ↓ + 4NH ₃ + H ₂ O
Here, R-CHO is an aldehyde contained in a reducing solution (polysaccharide is hydrolyzed with hydrochloric acid to form a monosaccharide).
[Ag (NH ₃ ) ₂ ] ⁺ is ammoniacal silver nitrate contained in the silver mirror solution.
Then, it washed with ion-exchange water.

(Step β) Removal of silver particles having weak adhesion (only Examples 1 to 4)
Step β is a step of applying an acid solution to the substrate and then washing with water in order to remove silver particles having weak adhesion.
In this example, since the surface conditioner a in Step B was an acid solution, Step B was directly performed as Step β.

(Process D2) Silver mirror film (Examples 1 to 4 only)
Step D2 having the same contents as step D1 was performed to form a part of the silver mirror film.

(Process Da) Full gloss silver mirror film (Comparative Example 1 only)
The same silver mirror solution and reducing solution as in Step D1 were simultaneously sprayed with a two-head spray gun, mixed in the air, and applied to the surface of the undercoat for 30 seconds.
On the undercoat, silver particles were precipitated by the silver mirror reaction formula described in the above step D1, and a full-gloss silver mirror film (a general bright silver mirror film) was formed.
Then, it washed with ion-exchange water.

(Process Db) Half gloss silver mirror film (only Comparative Examples 2-5)
The following silver main liquid, silver secondary liquid, and reducing liquid were used as materials for the silver mirror film forming liquid.
・ Silver main liquid: Product name “MFS silver main liquid L”, product number “MFS-10L” of Surface Chemical Laboratory, Inc.
・ Silver secondary liquid: Product name “MFS Silver secondary liquid L” of Surface Chemical Laboratory, product number “MFS-20L”
・ Reducing solution: Product name “MFS reducing agent L”, product number “MFS-30L” of Surface Chemical Engineering Laboratory Co., Ltd.

The silver main solution is diluted 15 times with ion-exchanged water (eg; silver main solution 5 mL, water 70 mL), and the silver sub-solution is diluted 15 times with ion-exchanged water (eg; silver auxiliary solution 5 mL, water 70 mL). The diluted solution was mixed to prepare a silver mirror solution.
The reducing solution was diluted 30 times with ion-exchanged water (eg, reducing solution 5 mL, water 145 mL) to prepare a reducing solution (diluted solution) containing 0.085 to 0.258 mol / L of aldehyde.

These silver mirror solution and reducing solution were sprayed simultaneously with a two-head spray gun, mixed in the air, and applied to the surface of the undercoat. The spray application time was 10 seconds in Comparative Example 2, 8 seconds in Comparative Example 3, 6 seconds in Comparative Example 4, and 4 seconds in Comparative Example 5.
On the undercoat, silver particles were precipitated by the silver mirror reaction formula described in the above step D1, and a half gloss silver mirror film was formed.
Then, it washed with ion-exchange water.

(Process Dc) Half gloss silver mirror film (only Comparative Examples 6-9)
The following silver main liquid, silver secondary liquid, and reducing liquid were used as materials for the silver mirror film forming liquid.
・ Silver main liquid: Product name “MFS silver main liquid # 50” of Surface Chemical Laboratory, product number “MFS-10 # 50”
・ Silver secondary liquid: Product name “MFS silver secondary liquid # 50” of Surface Chemical Laboratory, product number “MFS-20 # 50”
・ Reducing liquid: Product name “MFS reducing agent # 50” of Surface Chemical Laboratory, product number “MFS-30 # 50”

The silver main solution is diluted 15 times with ion-exchanged water (eg; silver main solution 5 mL, water 70 mL), and the silver sub-solution is diluted 15 times with ion-exchanged water (eg; silver auxiliary solution 5 mL, water 70 mL). The diluted solution was mixed to prepare a silver mirror solution.
The reducing solution was diluted 30 times with ion-exchanged water (eg, reducing solution 5 mL, water 145 mL) to prepare a reducing solution (diluted solution) containing 0.085 to 0.258 mol / L of aldehyde.

These silver mirror solution and reducing solution were sprayed simultaneously with a two-head spray gun, mixed in the air, and applied to the surface of the undercoat. The spray application time was 30 seconds for Comparative Example 6, 15 seconds for Comparative Example 7, 10 seconds for Comparative Example 8, and 6 seconds for Comparative Example 9.
On the undercoat, silver particles were precipitated by the silver mirror reaction formula described in the above step D1, and a half gloss silver mirror film was formed.
Then, it washed with ion-exchange water.

(Process E) Corrosion prevention treatment (all examples)
For the purpose of removing unreacted substances from the silver mirror film and stabilizing silver (preventing discoloration), the anticorrosion solution was sprayed to carry out corrosion prevention treatment of the silver mirror film.
The following corrosion inhibitors were used as materials for the corrosion prevention liquid.
Corrosion inhibitor: Product name “Ag corrosion inhibitor # 50” of Surface Chemical Laboratory, product number “MFS-50” (mixture of sodium thiosulfate 1-7%, acetic acid <1%, aluminum sulfate <1% Aqueous solution).

This corrosion inhibitor was diluted 50 times with ion-exchanged water (eg; 10 mL of corrosion inhibitor, 490 mL of water) to prepare a corrosion inhibitor, and sprayed onto the surface of the silver mirror film with a spray gun.
While wet with the corrosion prevention liquid, it was washed with ion-exchanged water to wash away the excess of the corrosion prevention liquid.
It was kept at 70 ° C. for 60 minutes in a constant temperature bath and dried.

(Process F) Topcoat layer (all examples)
A top coat solution was applied to the silver mirror film after the corrosion prevention treatment for the purpose of protecting the silver mirror film and the like, and a top coat was applied.
The following main agent, curing agent and diluent were used as the material for the topcoat solution.
・ Main agent: Product name of “MFS Topcoat Special Main Agent (Clear)”, product number “MFS-61-2” (33% acrylic resin, xylene (mixed) 25.1%, ethylbenzene 25.1% , N-butyl alcohol 10-15%, isobutyl alcohol 5-10% mixture).
・ Curing agent: Product name “MFS Topcoat Special Curing Agent” product number “MFS-62-2” (10.7% xylene, 10.7% ethylbenzene, 25-30% isopropyl alcohol, n -A mixture of 1 to 5% of butyl alcohol).
-Diluent: Product name "MFS Topcoat Special Diluent" product number "MFS-63-2" (Surface 30%, Xylene 25%, Ethylbenzene 25%, Methoxybutyl acetate 5-10% A mixture of 10-15% propylene glycol monomethyl ether acetate).

These main agents: curing agents: diluents were mixed at a mass ratio of 100: 20: 60 to 80 and spray-coated on the surface of the silver mirror film with a spray gun.
After the application, it was held at 65 ° C. for 30 minutes in a thermostatic bath, cured and dried to form a topcoat layer having a film thickness of 15 to 25 μm.

  Examples 1 to 4 and Comparative Examples 1 to 9 were prepared as described above, and the following measurements and observations were performed after the corrosion prevention treatment in (Step E) (before the top coat layer was formed).

<1> L * a * b * chromaticity L * a * b * chromaticity was measured by a SCI method using a colorimeter CM-700d manufactured by Konica Minolta. The measurement results are shown in Table 1.

<2> surface of the surface resistance value of the silver mirror film, by 1.0 × 10 ⁴ Ω / □ or less 4 terminal 4 depth probe method conforming to JIS-K7194 in the case of, 1.0 × 10 ⁴ Ω / □ In the above cases, each was measured by the double ring probe method in accordance with JIS-K6911. The measurement results are shown in Table 1.

<3> Millimeter-wave transmission attenuation The millimeter-wave transmission attenuation was measured using an electromagnetic wave absorption measuring device (free space method, owned by Fine Ceramics Center).
Specifically, at room temperature, W-band (76.575 GHz) electromagnetic waves are incident on the sample at an incident angle of 0 ° from the transmitter, and the electromagnetic waves are transmitted through the sample by a receiver facing the transmitter across the sample. The millimeter wave transmission attenuation in the round trip path was measured. The millimeter wave transmission attenuation by the silver mirror film was calculated by subtracting the millimeter wave transmission attenuation by the base material as the reference value. The calculation result is shown in 1.

<4> SEM Observation With the SEM (scanning electron microscope), the surface observation and the cross-sectional observation of the silver mirror film were performed on those described in Table 1. The SEM photographs are shown in FIGS.

As shown in the above measurement results, in Examples 1 to 4, the L * value of the L * a * b * color system is 65 or more, the surface resistance value is 1 × 10 ¹¹ Ω / □ or more, and millimeter waves The transmission attenuation is 2 dB or less, and it has both glitter and millimeter wave transparency. This is considered to be due to the action described with reference to FIG. FIG. 1 shows the repetition of the process β and the process D2 only twice for the convenience of space.

  On the other hand, Comparative Example 1 (full gloss) has glitter, but has a low surface resistance and does not have millimeter wave permeability. As shown in FIG. 2, it is considered that the silver particles adhere to each other and are stacked when the process Da is performed once for a long time. Further, none of Comparative Examples 2 to 9 (half gloss) has both glitter and millimeter wave transparency.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

Claims (3)

Step B in which a tin chloride solution is applied to a substrate and then washed with water;
A step D1 of applying a silver mirror film-forming liquid to the substrate to form part of the silver mirror film and then washing with water;
A step β of applying an acid solution to the substrate and then washing with water;
A step D2 of applying a silver mirror film-forming liquid to the substrate to form a part of the silver mirror film and then washing with water;
A method of forming a millimeter-wave permeable silver mirror film, wherein the process is repeated at least once from step β to complete a silver mirror film. L * a * b * color system L * value is 65 or more, surface resistance value is 1 × 10 ¹¹ Ω / □ or more, and millimeter wave transmission silver mirror film whose millimeter wave transmission attenuation is 2 dB or less . A substrate, formed on the surface of the substrate, L * a * b * L * value of color system is not less 65 or more, the surface resistance of 1 × 10 ¹¹ Ω / □ or more, the millimeter wave transmission A millimeter-wave transparent decorative article including a silver mirror film having an attenuation of 2 dB or less.