JP2000239577A - Coating film structure and electronic equipment housing using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating film structure capable of reducing the average heat conductivity of a coating film and reducing the effective temperature and useful for an electronic equipment housing, etc., by dispersing nonporous hollow beads in the coating film except the topmost layer coating film in the coating films formed in many layers. SOLUTION: This structure is obtained by dispersing nonporous hollow beads 1 formed of a nonporous material such as glass having, e.g. average 30 μm diameter in at least one coating film except the topmost layer coating film in the coating films 2 and 3 formed in many layers. The content of the hollow beads 1 is preferably <=20 wt.% and an electronic equipment housing is preferably produced by forming the coating having the coating film structure on a metal substrate 4. Furthermore, the viscosity of the coating material forming the coating films is preferably about 55×10-3 Pa.s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating film structure capable of reducing the temperature of a housing of a device including a heat-generating component, and an electronic device housing using the coating film structure.

[0002]

2. Description of the Related Art Electronic devices such as various computers, audio devices, and communication devices have been reduced in size and weight, and have improved portability. Further, these electronic devices are required to be further reduced in size and weight.

However, with further miniaturization, it has become necessary to consider measures against heat in electronic devices and the like having a built-in heat-generating component. Conventional techniques relating to heat insulation and heat-resistant structure of the housing surface include the following.

First, FIG. 3 shows a conventional example disclosed in Japanese Patent Application Laid-Open No. 9-12938. Here, a coating film (layer) 33 in which a hollow porous microcapsule 32 is added to the surface of a metal substrate 31 is shown, and is used as a coating material for the inner surface of a heating vessel of a water heater.

Next, FIG. 4 shows a conventional example disclosed in Japanese Patent Application Laid-Open No. Hei 10-151410. Here, a copper layer 42, a nickel layer 43, a hard transparent glass protective layer 44, and a silica layer 45 are sequentially formed on the surface of a housing 40 formed of a magnesium or magnesium alloy molded body 41.

[0006]

When the above prior art is applied to the surface of a housing of an electronic device or the like having a built-in heat generating component, the following problems occur.

In the configuration of Japanese Patent Application Laid-Open No. 9-12938,
The microcapsules 32 are formed of a porous material such as an alkaline earth metal salt such as calcium carbonate, calcium silicate, and magnesium silicate, and a metal oxide such as silica, alumina, and titanium oxide. These materials are polar,
Since the film-forming element easily conforms to the polar group of the film-forming element and has good wettability, the film-forming element easily permeates into the microcapsule 32, and the air portion in the microcapsule 32 decreases or disappears.

The thermal conductivity of the above material (generally 10 to 20 W /
m / K) is the thermal conductivity of a general coating film (approximately 0.2 W / m).
/ K), the average thermal conductivity of the coating film is substantially equal to or larger than the case where the microcapsules 32 are not contained due to the decrease or disappearance of the air portion. Therefore, the effect of reducing the perceived temperature when the surface of the housing exposed to the high temperature by the heat of the heat-generating component is touched is reduced.

In the structure disclosed in Japanese Patent Application Laid-Open No. H10-151410, the thermal conductivity of the copper layer 42, the nickel layer 43, the hard transparent glass protective layer 44, and the silica layer 45 formed on the surface of Since the heat conductivity is larger than the heat conductivity, heat generated inside the housing 40 is easily transmitted to the outside, and it is difficult to reduce the sensible temperature.

[0010]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and the invention according to claim 1 has at least a multi-layered coating film excluding the uppermost coating film. It is a coating film structure characterized by dispersing non-porous hollow beads in one coating film.

Further, the invention according to claim 2 is the coating film structure according to claim 1, wherein the content of the hollow beads is 20% by weight or less.

According to a third aspect of the present invention, there is provided an electronic device housing wherein a coating having the coating structure according to the first or second aspect is formed on a metal substrate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings and tables.

FIG. 1 shows a schematic configuration diagram of the coating film structure of the present invention.

As shown in FIG. 1, the coating structure of the present invention
An undercoating film 2 in which non-porous hollow beads 1 are dispersed is formed on the surface of a metal plate 4, and has a two-layer structure having an overcoating film 3 thereon. Here, the undercoating film 2 is a coating film (also referred to as a primer) for improving the adhesion to the underlying metal plate 4, and the overcoating film 3 is a coating film for appearance containing a pigment, a dye, and the like. Here, a two-layer coating structure is described, but a multi-layer structure of three or four layers may be used.

A method for producing the above-mentioned coating film structure will be described below.

First, an undercoating film 2 of origin primer: E-03 (manufactured by Origin Electric Co.) is mixed with hollow beads 1 manufactured by Sumitomo 3M Co., Ltd.
m. After that, it is baked at 70 ° C. for 30 minutes.
The top coat 3 is coated on the undercoat 2 by an automatic coater.
It is applied in a thickness of μm and baked at 150 ° C. for 20 minutes. It is produced by such a method to obtain a multilayer-formed coating film.

Hollow beads 1 mixed with undercoat 2
Has an average diameter of 30 μm, for example, and is formed of a nonporous material such as glass. Since it is non-porous, the coating film forming element in the coating material does not permeate into the hollow beads 1 and the undercoating film 2 with air intervening inside the beads.
Dispersed inside.

The thermal conductivity of an ordinary coating film containing no beads or the like is approximately 0.2 W / m / K, and the thermal conductivity of air is 2.
Since it is 6 × 10 ⁻² W / m / K, the average thermal conductivity of the coating film becomes smaller than that in the case where no beads are contained due to the presence of air inside.

Therefore, even when the temperature of the metal plate 4 becomes high, the transfer of heat to the surface of the coating film is suppressed.
The sensible temperature when the user touches the surface of the coating film can be reduced.

Next, using the above-mentioned manufacturing method, an undercoating film in which nonporous hollow beads are dispersed at a predetermined ratio on the surface of the magnesium alloy plate and an unfilled topcoating film are sequentially formed.
The sensible temperature of the coating film surface when the back surface of the alloy plate was heated to a high temperature was examined.

Here, the content of the nonporous hollow beads was set to 2, 5, 10, 20, 0, and 30% by weight, respectively (Example 1).
4 and Comparative Examples 1 and 2). In addition, as an index of the sensible temperature, a time during which the surface of the coating film can be touched with a finger (hereinafter, a contactable time) and a heat felt at the moment when the hand is touched (hereinafter, a sensation) are used. Table 1 shows the experimental results described above.

[0023]

[Table 1]

Here, the reason why the sensory temperature is used as an experimental result will be described.

An attempt was made to measure the surface temperature in the above experiment with a non-contact thermometer, but none of the experimental results in Table 1 showed a temperature difference of several degrees Celsius. However, since the sensible temperature is proportional to the amount of heat per unit time with respect to the contact surface area, the above-mentioned index was used. The sensible temperature used here is shown as an average value of 10 samples.

As is clear from the results in Table 1 above,
Example 1 to Example 4, ie, nonporous hollow beads,
A coating structure containing 5, 10, or 20% by weight has an effect of reducing the sensible temperature, and the effect is particularly great when it is contained at 10, 20% by weight.

Comparative Example 1, that is, when the hollow beads were not mixed in the undercoating film (conventional method), the sensible temperature was very hot, and the result was that the touch panel could not be touched for a long time. Further, in the case of Comparative Example 2, when the content is 30% by weight, the effect of reducing the perceived temperature is great, but since the hollow beads are not completely mixed and are exposed in powder form on the surface of the coating film, a good undercoat coating film is obtained. It was also found that the adhesiveness of the top coat was hindered.

The diameter of the non-porous hollow beads used here was 30 μm on average, and the viscosity of the paint forming the coating film was 55 ×
10 ⁻³ Pa · s (Iwata viscosity: 20 sec.).
The lower limit of the viscosity range of the paint is the viscosity at which the beads are not exposed from the coating film, and is approximately 35 × 10 ⁻³ Pa · s. The upper limit of the viscosity range is the viscosity that can be discharged from the spray gun, and is approximately 80 × 10 ^−3. Pa · s.

Next, the surface roughness, the pencil hardness and the hardness of the case where the non-porous hollow beads were dispersed in the undercoat film (Example 5) and the case where they were dispersed in the overcoat film (Comparative Example 3) were as follows. The characteristics of cracking and peeling when rubbing with a nail and the possible contact time were examined. Here, the production method was the same as that described above, and the content of nonporous hollow beads was 10% by weight.
Table 2 shows the results.

[0030]

[Table 2]

As is clear from the results, the contactable time is the same in Example 5 and Comparative Example 3;
Has smaller surface roughness, higher pencil hardness, and no cracking or peeling when rubbed with a nail.

Therefore, it is considered that the coating structure dispersed in the undercoat coating film is suitable for use in the case of painting on the surface of a housing.

Next, a case having a coating film structure as shown in FIG. 1 will be described.

FIG. 2A shows a case 11 in an example of a notebook personal computer 10 on which a heat-generating component such as a CPU 16 is mounted.
FIG. 2B is a schematic sectional view of a portion, and FIG. 2B is an enlarged view of a coating film structure.

As shown in FIG. 2A, the casing 11 is formed of a magnesium alloy, and the outer
The two-layer coating structure shown in FIG.
, Non-porous hollow beads 21 are dispersed therein, and then a top coat 23 is applied. The method for producing these coating films is the same as the method described above. A board 13 is provided inside the housing 11.
CPU 16 is attached to the heat conductive rubber 14,
Heat is dissipated to the inner surface 15 of the housing. Other electronic components on the substrate are omitted.

When the notebook personal computer 10 is operating, the CPU 1
Due to the heat generated in 6, the temperature of the inner surface 15 may rise to 50 to 60 ° C. Even in such a case, the amount of heat transmitted to the outer surface 12 is suppressed by the coating structure shown in FIG. 2B, and the sensible temperature when touching the housing is reduced. Here, FIG.
The coating structure shown in (b) may be applied to the inner surface 15 of the housing.

The non-porous hollow beads are made of a solid material having polarity (for example, calcium carbonate, calcium silicate,
Alkaline earth metal salts such as magnesium silicate, and metal oxides such as silica, alumina, and titanium oxide). It is easy to disperse in the inside.

[0038]

As described above, according to the first aspect of the present invention, non-porous hollow beads are dispersed in at least one coating film other than the uppermost coating film among multilayer coating films. The coating film forming element in the coating material does not permeate into the hollow beads, and can be dispersed in the undercoating film with air interposed in the beads. Therefore, the average thermal conductivity of the coating film is smaller than that in the case where the beads are not dispersed, and there is an effect that the sensible temperature can be reduced.

According to the second aspect of the present invention, the effect of reducing the perceived temperature can be obtained by setting the content of the hollow beads to 20% by weight or less.

Further, according to the third aspect of the present invention, the first aspect is provided.
Or the electronic device housing in which the coating having the coating structure according to 2 is formed on a metal substrate, the amount of heat transmitted to the housing surface by the coating structure is suppressed, and the sensible temperature when touched is reduced. There is an effect that can be reduced.

Particularly, a portable electronic device such as a notebook personal computer may be used by placing it on the knee. In such a case, there is an effect of reducing the heat felt by the knee.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a coating film structure of the present invention.

FIG. 2 is a schematic sectional view of a housing of the present invention.

FIG. 3 is a schematic sectional view of a prior art coating structure.

FIG. 4 is a schematic cross-sectional view of another conventional coating film structure.

[Explanation of symbols]

 1,21 Non-porous hollow beads 2,22 Undercoat 3,23 Top coat 4 Metal plate 10 Laptop computer 11 Housing 12 Outer surface 13 Substrate 14 Thermal rubber 15 Inner surface 16 CPU 20 Coating structure

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D075 CA17 DA06 DB01 DC21 EC24 EC54 4J038 EA011 HA216 HA286 HA446 HA456 HA486 KA21 PA07 PB09 PC02

Claims (3)

[Claims] 1. A coating structure wherein non-porous hollow beads are dispersed in at least one coating film excluding the uppermost coating film among multilayer coating films. 2. The coating structure according to claim 1, wherein the content of the hollow beads is 20% by weight or less. 3. An electronic device housing, wherein a coating having the coating structure according to claim 1 or 2 is formed on a metal substrate.