JP3136391B2 - Insulating paint layer for smooth substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smooth substrate in which the surface of a pattern is flush with the surface of a surrounding insulating paint layer, and more particularly to a material of the insulating paint layer.

[0002]

2. Description of the Related Art Conventionally, among variable resistor substrates, switch substrates, and the like, there is a so-called smooth substrate in which a pattern surface on which a slider slides is in contact with an insulating substrate surface. . This kind of smooth substrate has no step between the pattern and the insulating substrate, so that the slider that slides on it has good abrasion resistance and long life, and the slider can move extremely smoothly. There is an advantage.

[0003] As a conventional smooth substrate of this kind,
For example, a portion other than a portion to be a pattern surface by performing etching on a thin metal plate is formed into a concave portion, and in a state where the pattern surface is pressed against a mold surface, an insulating synthetic resin is poured into the concave portion to form the pattern surface and the synthetic resin. Some have the same surface as the surface.

However, in this type of conventional smooth substrate, the smoothness of the smooth surface cannot be increased so much, and a mold having a smooth surface equivalent to the smooth surface of the smooth substrate is prepared. Although it is necessary, the mold is expensive, and the joint between the pattern made of a metal plate and the resin on the smooth surface necessarily has larger irregularities than the other portions.

Accordingly, the applicant of the present application has filed Japanese Patent Application No. Hei 5-17237.
In the patent application No. 2, a pattern made of a conductive paste having poor adhesion to the transfer substrate is printed on the transfer substrate,
The entire surface of the transfer substrate is coated with an insulating paint layer having poor adhesion to the transfer substrate and good adhesion to the pattern, and applying the insulating paint layer directly or on another substrate different from the transfer substrate. A flat substrate manufactured by bonding indirectly via a layer and peeling only the transfer substrate to expose the pattern and the insulating paint layer has been proposed.

In this smooth substrate, the smooth surface is constituted by a pattern made of a conductive paste and an insulating paint layer. The sliding is repeated in the contact state.

However, since the insulating paint layer is a resin applied by printing, the insulating paint layer has a certain degree of flexibility even after the printing is solidified. When a high temperature (for example, 85 ° C.) elapses for a long time (for example, 100 hours) in a state of being elastically contacted, there is a problem that a dent occurs in the elastically contacted portion of the insulating paint layer.

On the other hand, in order to increase the hardness of the insulating paint layer,
Fine powder made of a hard material such as silica may be mixed, but this causes a problem that the adhesion and printability of the insulating paint layer to other base materials are deteriorated.

The present invention has been made in view of the above points, and an object of the present invention is to provide an insulating paint layer for a smooth substrate which has improved hardness and at the same time satisfies adhesiveness and printability.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an insulating paint layer on a substrate directly or via another layer, and comprises a conductive paste so as to be embedded in the insulating paint layer. A pattern of a desired shape is provided, and the surface of the insulating paint layer and the surface of the pattern are made smooth and flush with each other .
In a smooth substrate having a smooth surface on which a slider elastically contacts and slides, the insulating paint layer on which the slider elastically contacts and slides the surface is made of an acrylic ultraviolet curing resin. In addition, among those having a glass transition temperature of 90 ° C. to 160 ° C., a powder of silica having a weight percentage of 5 to 15% and a powder of Teflon having a weight percentage of 5 to 25% are mixed. .

[0011]

By constituting the insulating paint layer as described above,
All of the hardness, adhesion and printability of the insulating paint layer could be simultaneously improved.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here, FIG. 1 is a schematic side sectional view showing an example of a smooth substrate formed using the insulating paint layer according to the present invention. As shown in the figure, the smooth substrate 1 is provided on a main substrate (substrate) 40 with three layers of thermoplastic insulating paints 35, 30, 25.
And an insulating paint layer 20 according to the present invention, a pattern 15 made of a conductive paste is provided so as to be embedded in the insulating paint layer 20, and the surface of the insulating paint layer 20 and the surface of the pattern 15 are formed as a smooth and same surface. Have been.

In the present invention, the material of the insulating paint layer 20 is improved. Before describing this, a method of manufacturing the smooth substrate 1 will be described first.

First, as shown in FIG. 5A, a transfer substrate 10 made of a synthetic resin film is prepared.

As a material of the transfer substrate, inexpensive polyethylene terephthalate (PET) was used. However, another polyester film, Teflon film, or silicon film may be used. The surface of these synthetic resin films is usually smooth, and the surface roughness is usually 0.1 μm or less.

Next, as shown in FIG. 1A, a pattern 15 made of a conductive paste is screen-printed on the transfer substrate 10 so as to have a desired shape.

As the material of the conductive pattern 15, a silver paste obtained by mixing silver powder with a phenolic resin was used.
The material of the conductive paste has such a property that when it is printed on the transfer substrate 10, it does not easily stick to the transfer substrate 10 and is hardly repelled.

Next, as shown in FIG. 1B, the entire surface of the transfer substrate 10 is coated with the insulating paint layer 20 according to the present invention and solidified.

The insulating paint layer 20 is an acrylic UV-curable resin having a glass transition temperature of 100 ° C.
To 10% silica (Si
O ₂ ) powder and 10% by weight Teflon powder.

The acrylic UV curable resin, which is the material of the insulating paint layer 20, has good adhesion to the conductive paste forming the pattern 15, and the transfer substrate 1
The resin film, such as PET, which constitutes No. 0 has poor adhesion properties.

Next, as shown in FIG. 1C, a polyester-based thermoplastic insulating coating 25 is formed on the insulating coating layer 20.
Is applied and solidified, and a vinyl chloride-based hot melt type thermoplastic insulating paint 30 is further applied on the thermoplastic insulating paint 25. This thermoplastic insulating paint 30
It has the property of softening at a temperature of about 100 ° C.

Although the thermoplastic insulating paint 25 is provided for firmly connecting the insulating paint layer 20 and the thermoplastic insulating paint 30, it may be omitted.

Next, as shown in FIG. 2D, a main substrate 40 made of a synthetic resin film is prepared, and a vinyl chloride-based hot melt type thermoplastic insulating coating of the same quality as the thermoplastic insulating coating 30 is provided thereon. 35 is applied.

Here, the substrate 40 is made of polyethylene terephthalate, but any other material may be used as long as it has good adhesion to the thermoplastic insulating paint 35.

Then, the transfer substrate 10 and the main substrate 40 are overlapped with each other so that the surfaces of the thermoplastic insulating paints 30 and 35 are in close contact with each other, and are pressed and heated. As a result, the hot-melt type thermoplastic insulating paints 30 and 35 are fused and integrated with each other ((e) in the figure).

Then, when the transfer substrate 10 is peeled off, the smooth substrate 1 shown in FIG. 1 is completed. Here, the transfer substrate 10 has poor adhesion to the pattern 15 and the insulating paint layer 20, while the pattern 15—the insulating paint layer 20—the thermoplastic insulating paint 25—the thermoplastic insulating paint 30—the thermoplastic insulating paint 3
Since the adhesion between the 5-substrate 40 is good, other layers are not peeled off when the transfer substrate 10 is peeled off.
Only the transfer substrate 10 is peeled off.

Since the surface of the synthetic resin film forming the transfer substrate 10 is very smooth, the surfaces of the pattern 15 and the insulating paint layer 20 which are in close contact with the synthetic resin film are also very smooth and smooth. It is completely buried in the paint layer 20 and there is no gap between the pattern and the joint of the surface of the insulating paint layer 20.

The inventor of the present application has found a material that satisfies all of the hardness, adhesion and printability of the insulating paint layer 20 by repeating various experiments. This will be described below.

The performance required of the insulating paint layer 20 is such that the slider is not dented even if the slider elastically contacts the heated insulating paint layer 20 for a long time. It is required to have an adhesiveness that does not cause cohesion failure (to be described below) and a printability that has a viscosity that can be printed. Another important requirement for obtaining a smooth surface is that the film does not warp due to shrinkage of the paint when it is printed and solidified.

It has been found that these requirements can be solved by setting the glass transition temperature of the acrylic UV-curable resin to a predetermined value and mixing silica and Teflon powders by predetermined amounts. . Here, the glass transition temperature refers to a temperature at which a polymer substance is changed from a hard glassy state to a soft rubbery state when heated. This will be specifically described below.

First, as shown in FIG. 3, a 6 cm square synthetic resin film 60 made of polyethylene terephthalate is used.
A 5 cm square sample 65 of an insulating paint layer was printed thereon, and the sample 65 was examined for warpage and depression.

The sample 65 is an acrylic UV-curable resin having a glass transition temperature of 50.degree. C., 100.degree. C., and 150.degree. C., each containing 10% by weight of silica. A mixture of Teflon powder was used. The synthetic resin film 60 has a thickness of 75 μm, a thickness of 188 μm, and a thickness of 2 μm.
The thing of 50 μm was used.

In the warp test, the size of the warp of the synthetic resin film 60 after drying the sample 65 is obtained as a dimension f shown in FIG. 3B. When 5 <f ≦ 1.0 (mm), Δ was determined when 1.0 <f (mm).

In the test for depressability, after transferring this sample 65 onto another main substrate by the method shown in FIG. 5, the synthetic resin film 60 was peeled off, and the surface of the transferred sample 65 (synthetic resin film 60) was removed. The slider with a brush pressure of 5 g was elastically contacted with the surface (the surface on the side that was in close contact with the roller) and left at 85 ° C. for 100 hours, and it was examined whether or not the elastic contact portion collapsed. And, when not depressed, it was evaluated as O, and when depressed, it was evaluated as X.

FIG. 2 is a diagram showing these results. As shown in the figure, it was found that the sliders with glass transition temperatures of 100 ° C. and 150 ° C. did not collapse even when left at 85 ° C. for a long time. It was also found that the warpage increases as the glass transition temperature increases, whereas it can be reduced as the thickness of the synthetic resin film 60 increases.

The glass transition temperature is 9 from the point of depression.
Since a substrate having a temperature of 0 to 160 ° C. is preferable, it is preferable to use a substrate having a thickness of about 188 μm or more as shown in FIG.

As described above, the glass transition temperature is 90 to 1
Although it was found that a temperature of 60 ° C. was preferable, an experiment was conducted to determine the optimum amount of silica and Teflon particles to be mixed therewith.

The reason for mixing silica here is to increase the hardness of the insulating coating layer 20 (since the silica is hard), while mixing Teflon is used to reduce the frictional resistance of the surface of the insulating coating layer 20. At the same time, it is for improving the releasability from the transfer substrate 10 (because the surface of Teflon has low frictional resistance).

The sample used in this experiment was an acrylic UV-curable resin having a glass transition temperature of 1
0%, 10%
%, 20%, and 30% of silica and Teflon powder were used.

These samples were printed on a synthetic resin film made of polyethylene terephthalate, and the samples of the respective insulating paint layers were printed, and the pencil hardness, printability, and adhesion of each of the samples were examined.

Here, a pencil hardness test was conducted by rubbing pencils of hardness H, 2H, and 5H a predetermined number of times on the surface of the sample (before transfer) applied on the synthetic resin film, and forming a recess on the surface of the rubbed portion. This is a test for inspecting whether or not pits are formed. When a depression is formed at a hardness of not more than H, x is given. . A predetermined hardness is required because the slider slides on the insulating paint layer.

The printability test is a test for examining whether or not the viscosity is such that it is easy to print when a sample is printed on a synthetic resin film. And

In the adhesion test, a sample printed on a synthetic resin film was transferred onto another main substrate by the method shown in FIG. 5 and then the synthetic resin film was peeled off. After making a base-shaped scratch at the pitch angle, an adhesive tape (Nitto 31B) was adhered in close contact, and when the adhesive tape was vigorously peeled vertically upward, it was examined whether or not the coating film was peeled. . And when it peeled, it was evaluated as x, and when it did not peel, it was evaluated as o. If the adhesion is poor, when the transfer substrate 10 shown in FIG. 5 is peeled off, the insulating paint layer 20 also comes off.

FIG. 4 shows the results of the experiment. As shown in the figure, it was found that the pencil hardness increased as the weight percent of silica and the weight percent of Teflon increased simultaneously. This is probably because the addition of silica increases the hardness and the addition of Teflon smoothes the surface.

The printability deteriorates as the weight percentage of silica increases. This is considered to be due to the fact that the viscosity increases as the hardness increases with silica.

Also, the adhesion becomes worse as the weight percentage of silica and / or Teflon is increased. This is considered to be because cohesive failure occurs inside the printed paint. Here, cohesive failure will be described with reference to FIG. FIG. 6 is an enlarged schematic sectional view around the insulating paint layer 20 and the transfer substrate 10 in the state shown in FIG.

As shown in the figure, when the amount of silica and / or Teflon particles in the insulating paint layer 20 becomes too dense, the resin constituting the insulating paint layer 20 is transferred to the upper and lower transfer substrates 10 and the thermoplastic insulating paint 25. The resin is enriched on the transfer substrate 10 and the surface of the thermoplastic insulating coating 25 while the silica and / or Teflon particles are enriched in the center of the insulating coating layer 20. Therefore, the insulating paint layer 20
In the central part of the resin, the amount of resin binding the particles decreases, and the bonding strength of the part decreases. Therefore, when the transfer substrate 10 is peeled off, the insulating paint layer 20 is torn at its center. This is called cohesive failure.

From the results of FIG. 4, the range satisfying the pencil hardness, adhesion and printability at the same time is the portion surrounded by the thick frame in FIG. That is, the silica is 10% by weight, the Teflon is 10% or 20% by weight, more particularly, the silica has a weight percentage of 5-15% and the Teflon has a weight percentage of 5-25%. Was something.

The smooth substrate 1 shown in FIG. 1 is an example in which the insulating paint layer according to the present invention is used, and the smooth paint substrate having another structure may use the insulating paint layer according to the present invention. Needless to say.

That is, for example, as shown in FIG. 7A, a pattern 15 and an insulating paint layer 20 are applied on a transfer substrate 10 (this is the same as the process of FIGS. 5A and 5B in the above embodiment). Are the same), and these are sandwiched between upper and lower molds A and B.

Then, as shown in FIG.
By filling the heated and melted resin (for example, PBT resin, PET resin, ABS resin) in the gap D of the concave portion B1,
The insulating paint layer 20 is welded to the molten resin by the heat of the filled molten resin, and when the molten resin is cooled, both are firmly fixed. Then, by removing the upper and lower molds A and B and peeling off the transfer substrate 10, a smooth substrate 1 'as shown in FIG. Reference numeral 50 denotes a substrate on which the molten resin is solidified.

Further, as shown in FIG.
A pattern substrate, an insulating coating layer 20, a thermoplastic insulating coating 25, and a hot-melt type thermoplastic insulating coating 30 applied on a transfer substrate 10 (this is the same as the process shown in FIGS. 5A to 5C). Is prepared, and is sandwiched between upper and lower molds A and B. After filling and solidifying the resin which has been heated and melted in the space D, the upper and lower molds A and B are removed and the transfer substrate 10 is peeled off. This can also produce a smooth substrate. In this case, the adhesive force of the insulating paint layer 20 and the like to the resin (substrate) becomes stronger.

[0053]

As described in detail above, according to the present invention, an acrylic UV-curable resin is mixed with silica and Teflon powder, and at the same time, the glass transition temperature of the resin and the silica and Teflon are compared. Since the mixing ratio is set to a predetermined value, there is an excellent effect that all of the hardness, adhesion and printability of the insulating paint layer for a smooth substrate can be simultaneously improved.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing an example of a smooth substrate formed using an insulating paint layer according to the present invention.

FIG. 2 is a view showing experimental results of depression and warpage.

FIG. 3 is a view showing an experimental method of depression and warpage.

FIG. 4 is a view showing experimental results of pencil hardness, adhesion and printability.

FIG. 5 is a diagram illustrating a method of manufacturing the smooth substrate 1.

FIG. 6 is a diagram for explaining cohesive failure.

FIG. 7 is a diagram showing another example of a smooth substrate formed using the insulating paint layer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Smooth board 15 Pattern 20 Insulating paint layer 40 Main board (base) 50 Base

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 1/03 630 B05D 5/12 C09D 5/25 H05K 1/02 H05K 3/22

Claims (1)

(57) [Claims] An insulating paint layer is provided on a substrate directly or via another layer, a pattern of a desired shape made of a conductive paste is provided so as to be embedded in the insulating paint layer, and a surface of the insulating paint layer is provided. the surface of the pattern as a smooth coplanar, this
In a smooth substrate having a smooth surface on which a slider elastically contacts and slides, the insulating paint layer on which the slider elastically contacts and slides on the surface is made of an acrylic ultraviolet curable resin. And having a glass transition temperature of 90 ° C. to 160 ° C., a mixture of silica powder having a weight percentage of 5 to 15% and Teflon powder having a weight percentage of 5 to 25%. An insulating paint layer for a smooth substrate, characterized by the following.