JP4221039B2 - Pre-coated metal plate for drive case - Google Patents

Description

  The present invention relates to a precoat metal plate for a drive case used for a drive case of an electric device or an electronic device such as a liquid crystal television, a personal computer, and a DVD player.

  In order to prevent malfunctions due to static electricity and electromagnetic noise, conductivity is an important performance required for drive case materials for electrical and electronic equipment. In order to satisfy the conductive performance, it is conceivable to use a bare metal plate. When using a bare metal plate, a high-viscosity press oil required a degreasing step with an organic solvent, etc., but the degreasing step was omitted from the viewpoint of dealing with environmental problems. Volatile press oil has been used.

  However, since the low-viscosity volatile press oil has poor lubricity, cracks occur in the high-processed part during molding, and the problem of being easily damaged by abrasion with the mold remains. On the other hand, when a paint containing a lubricant is applied on the metal plate, the moldability is improved. However, since the obtained resin film is an insulator, there is a disadvantage that the conductivity is inferior. Thus, a device has been devised to satisfy the contradictory performance, and a precoated metal plate having formability and conductivity has been proposed.

Patent Document 1 contains at least one selected from the group consisting of acrylic resins, epoxy resins, and urethane resins as a resin component, and contains 1 to 50% by weight of moisture and 0.1 to 20% by weight of lubricant. And the metal plate material for electric and electronic devices by which the surface of a metal plate is coat | covered with the resin film which is 0.05-5 micrometers in thickness is disclosed.
: JP 2002-275656 A

Patent Document 2 discloses an aluminum plate in which a corrosion-resistant film and a resin film are sequentially formed from at least one side of an aluminum base plate having a center line average roughness of 0.2 to 0.6 μm from the base plate side. Here, the corrosion-resistant film contains Cr or Zr, the adhesion amount is 10 to 50 mg / m ² in terms of Cr or Zr, and the resin film has an average film thickness of 0.05 to 0.3 μm and is an all resin film 1-25 mass% lubricant is contained with respect to the quantity. On the surface of the aluminum base plate or the surface on which the corrosion-resistant film is formed, fine convex portions are exposed on the surface of the resin film. When a spherical terminal having a radius of 10 mm is pressed against the surface on which the resin film is formed with a load of 0.4 N, the surface resistance value between the spherical terminal and the aluminum base plate is set to 10Ω or less.
: JP 2003-313684 A

Patent Document 3 discloses a conductive precoated aluminum alloy plate comprising a substrate made of an aluminum alloy plate, a chemical conversion film formed on one or both sides of the substrate, and a conductive layer formed on the chemical conversion film. The conductive layer is made of a conductive synthetic resin coating film containing a Zr compound and has a film thickness of 0.5 μm or less.
: JP 2004-068042 A

  As the film thickness of the resin film is thinner, the moldability tends to be inferior. This is because the resin film and the mold come into contact with each other and rub against each other, and the thinner the film, the more easily the resin film is damaged. Recently, the development of drive cases has progressed, and the formability required for precoated metal sheets has become more severe than before. The resin film disclosed in Patent Document 1 may contain 50% by mass of water, and therefore it is easily assumed that the resin film is easily broken starting from a portion where no resin component is present. In such a case, there is a problem that scratches remain after molding and the appearance quality of the drive case is poor.

  In the resin film disclosed in Patent Document 2, the surface roughness of the material is 0.2 μm to 0.6 μm in terms of the center line average roughness, and the thickness of the resin film is 0.05 to 0.3 μm. There is no provision for the three-dimensional surface shape of the coating surface. Therefore, for example, if the surface roughness of the material has a center line average roughness of 0.6 μm and the thickness of the resin film is 0.05 μm, it is considered that the convex portions of the material are likely to be exposed from the resin film surface. Therefore, it is easily assumed that the convex portions of the material easily rub against the mold. In such a case, there is a problem that scratches remain after molding and the appearance quality of the drive case is poor.

Since the Zr compound is contained in the resin film disclosed in Patent Document 3, it is easily assumed that the resin film becomes a starting point of breakage and the resin film is easily broken.
The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to provide a pre-coated metal sheet for a drive case that has excellent scratch resistance and excellent electrical conductivity.

The present invention is the pre-coated metal plate for a drive case according to claim 1, comprising a chemical film formed on both surfaces of the metal plate, and a resin film formed on one of the chemical films and containing a base resin and a lubricant. The average surface roughness of the metal plate is 0.13 to 0.60 μm, the thickness of the resin film is 0.03 to 1.0 μm, and the base resin is an acrylic resin or an epoxy resin It is at least one selected from the group consisting of a resin, a urethane-based resin, and a polyester-based resin. On the surface of the resin film, on a straight line that passes through the maximum height protrusion and is orthogonal to the rolling direction of the metal plate. an arithmetic average roughness Ra ([mu] m) is 0.10～0.54Myuemu, and there 19-781 per 1 mm ² is protrusions or Ra, residual moisture content of the resin film in the 0.001 .7 wt% der is, the resin coating further contains a surfactant, the lubricant comprises at least one polyethylene wax and carnauba wax, it said in the resin film surface, of any length 100μm one sum of the lengths of the particles of the lubricant has a drive case for precoated metal sheet, characterized in 10~80μm der Rukoto the straight cuts.

According to a second aspect of the present invention, the resin film is formed by spraying air at room temperature for 4 to 20 seconds and then cooling after baking.

  Since the precoated metal sheet of the present invention has a specific surface shape, it can impart good scratch resistance and good electrical conductivity. Furthermore, since the surface occupation ratio of a specific lubricant is in a specific range, it is possible to improve the balance between good scratch resistance and conductivity.

  The best mode for carrying out the present invention will be described below.

A. Metal plate The material of the metal plate used in the present invention is particularly limited as long as it has sufficient strength to form a drive case for parts of electrical equipment and electronic equipment and has sufficient formability. Is not to be done. Pure aluminum, aluminum alloys such as a 5000 series aluminum alloy, galvanized steel, and stainless steel are preferably used. Usually, a metal plate having a thickness of 0.1 to 2.0 mm is used.

B. Chemical conversion film A chemical conversion film is formed on both surfaces of the metal plate. The chemical conversion film is not particularly limited as long as it is interposed between the surface of the metal plate and a resin film to be described later to enhance the adhesion between them. For example, a conversion coating formed with a phosphate chromate treatment solution that is inexpensive and easy to manage bath solution, or a conversion coating formed with a non-chromate treatment solution in consideration of environmental problems can be used for the aluminum alloy. As the non-chromate treatment, in addition to the reactive zirconium phosphate treatment and the titanium phosphate treatment, a coating-type zirconium treatment can be used.

  Such chemical conversion treatment is performed by spraying a predetermined chemical conversion treatment liquid on the metal plate or immersing the metal plate in the treatment liquid at a predetermined temperature for a predetermined time. In the case of using galvanized steel or stainless steel as the metal plate, a chemical conversion film formed with a phosphating solution can be used in addition to the chromate treatment.

  Before the chemical conversion treatment, in order to remove dirt on the surface of the metal plate or to adjust the surface properties, the metal plate is subjected to acid treatment (washing) with sulfuric acid, nitric acid, phosphoric acid, etc., or caustic soda, It is desirable to perform alkali treatment (washing) with sodium phosphate, sodium silicate, or the like. Surface treatment by such cleaning is also performed by spraying a predetermined surface treatment liquid on the metal plate or immersing the metal plate in the treatment liquid at a predetermined temperature for a predetermined time.

C. Resin film Next, a resin film is formed on one of the chemical conversion films. The resin film is formed by baking a paint in which a base resin and a lubricant are essential components, a surfactant is contained as an optional component, and these are dissolved or dispersed in an appropriate solvent. The surface of the resin film thus obtained has a surface roughness in which a predetermined number of protrusions having a predetermined arithmetic average roughness Ra (μm) or more are present, a predetermined surface occupancy of the lubricant, and a resin The coating has a predetermined residual moisture content.

C-1. As the base resin, at least one selected from the group consisting of an acrylic resin, an epoxy resin, a urethane resin, and a polyester resin is used. As acrylic resin, acrylic ester resin, methacrylic ester resin, polyacrylamide etc. can be used, for example. As the epoxy resin, for example, bisphenol A type epoxy resin, acrylic modified epoxy resin, bisphenol F type epoxy resin, or the like can be used. As the urethane resin, for example, a polyether urethane resin, a polycarbonate urethane resin, or the like can be used. As the polyester resin, a phenol-modified polyester resin, a water-dispersed polyester resin, or the like can be used.

C-2. The lubricant lubricant is used as a component for imparting lubricity to the surface of the precoated metal plate and improving the formability. In the present invention, at least one of polyethylene wax or carnauba wax is preferably used. A polyethylene wax having a molecular weight of 600 to 12000 and a melting point of 70 to 140 ° C. is used. Carnauba wax is a plant wax mainly composed of a higher fatty acid ester and has a melting point of 78 to 86 ° C. The content of the lubricant is 1 to 15% by weight, preferably 2 to 12% by weight, based on the base resin.

  These lubricants impart lubricity to the resin film surface during molding such as press molding, improve the scratch resistance of the resin film, and also impart lubricity to the film surface after molding, It has the effect | action which reduces the frictional force generate | occur | produced between a to-be-contacted object and the resin film surface.

C-3. Surfactant Further, in the present invention, the resin film contains a surfactant. The surfactant is a component for improving the conductivity of the precoated metal plate surface. In the present invention, nonionic compounds such as alkylphenol ethylene oxide adducts and higher alcohol ethylene oxide adducts, anionic systems such as higher alcohol sulfates, alkylbenzene sulfonates and higher alcohol phosphates, higher alkylamine salts, alkyltrimethyls. Cationic systems such as ammonium salts can be used.

C-4. Additives and resin films, for example, paints, pigments, pigment dispersants, fluidity regulators, leveling agents, waxes, etc., used in ordinary paints to ensure coating performance and general performance as a precoat material. Inhibitors, preservatives, stabilizers and the like may be added as appropriate.

C-5. Surface Roughness ( A) Measuring Method In the present invention, the surface roughness of the resin film is defined as that a predetermined number of protrusions having an arithmetic average roughness Ra (μm) or more exist in a predetermined area. Here, the arithmetic average roughness Ra is an arithmetic average roughness defined in JIS B0601 on a straight line that passes through the protrusion at the maximum height and is orthogonal to the rolling direction of the metal plate in an arbitrary area of the resin film surface. Is defined as Specifically, for example, it is measured as follows. Using a laser tech Co., Ltd. confocal microscope HD100, a 3D image of the resin film surface was measured with a 50x objective lens, and the metal was passed through the highest peak in an arbitrarily selected 322 μm square area. The arithmetic average roughness Ra in one straight line in the direction perpendicular to the rolling direction of the plate is measured. Next, a three-dimensional image consisting only of protrusions with a height of Ra or higher is created for the above-mentioned surface area of 322 μm square, and the number of protrusions existing in the image is measured and converted to the number per 1 mm ^2. To do. At this time, the filter size of the median filter is set to 5 * 5. Measure five times and calculate the average value for Ra and the number of protrusions per mm ² . In addition, you may obtain | require the number of protrusion parts more than arithmetic mean roughness Ra with another measuring method.

(A) Limitation of surface roughness In the present invention, the number of protrusions having an arithmetic average roughness Ra or higher is defined as 19 to 781 per mm ^{2 on the} surface of the resin film. If the number of protrusions is less than 19, the exposure ratio of the chemical conversion film portion not covered with the resin film decreases, and the occupation ratio of the insulator (base resin, lubricant, etc.) increases. As a result, the conductivity is inferior because non-conducting portions are distributed. When the number of protrusions exceeds 781, the exposure rate of the chemical conversion film increases, so that the conductivity is good but the scratch resistance is poor. At the time of press molding, the resin film and the mold come into contact with each other and scratches are easily generated starting from the discontinuous portions of the resin film. Furthermore, since the protruding portion also contains a lubricant that segregates on the surface, the lubricant portion becomes a defect, and the film strength is lowered and a scratch is easily generated. Similar scratches are likely to occur when the resin film comes into contact with the packaging material during transportation.

C-6. Lubricant occupancy on the surface
(A) Observation method The cross-sectional state of the resin film is obtained by dissolving the metal of the coated metal plate and collecting only the resin film, dyeing the collected resin film with ruthenic acid, and then embedding it in an epoxy resin to form an ultramicrotome. Observe with a transmission electron microscope as ultrathin pieces.
When the cross section of the resin film is thus observed, the lubricant particles present on the surface of the resin film are observed as long lines parallel to the surface, as shown in FIG. In FIG. 1, 41 and 42 each represent one lubricant particle. Generally, since the surface energy of the lubricant is lower than that of the resin, the lubricant tends to be leached to the surface, and the leached lubricant is wet and spreads and becomes flat.

As shown in occupancy Figure 1 (b) lubricants, in the resin film surface, when depicting one straight line 5 of any length 100 [mu] m, one straight line 5 that cuts the wax particles 41. Lubricant particles 41 are cut to lengths d1, d2 and d3, and particles 42 are cut to lengths d4, d5 and d6. And the sum (d1 + d2 + d3 + d4 + d5 + d6) of the lengths of the lubricant particles 41 and 42 cut by one straight line 5 is 10 to 80 μm. In other words, the occupation ratio of the lubricant on the resin film surface is 10 to 80%. Thus, in the present invention, the ratio of the sum of the lengths of the lubricant particles cut at a predetermined length to the predetermined length is defined as the occupation ratio of the lubricant on the resin film surface. If the sum of the lengths of the lubricant particles cut by the straight line 5 is less than 10 μm (surface occupancy is less than 10%), the lubricity is insufficient and the scratch resistance is poor. On the other hand, if the sum of the lengths of the lubricant particles cut by the straight line 5 exceeds 80 μm (the surface occupancy ratio is less than 80%), the amount of lubricant as an insulator becomes large, and the conductivity is poor.

C-7. Residual moisture content in resin film
(A) Measuring method The residual moisture content of the resin film was measured by the following method. The weight (M1) of the resin film on the painted metal plate is measured. Next, the weight (M2) of the resin film is measured after heating in an oven at a temperature of 105 ° C. for 1 hour, and (M1−M2) × 100 / M1 is calculated. It is considered that all the water in the resin film escapes during the heating process in the oven, and (M1-M2) × 100 / M1 can be set as the residual moisture content of the resin film.

(A) Residual moisture content The residual moisture content of the resin film is 0.001 to 0.7 % by weight. By containing moisture in the resin film, the conductivity of the resin film is improved. When the residual moisture content is less than 0.001% by weight, the conductivity is poor. When the residual moisture content exceeds 0.7 % by weight, the scratch resistance is inferior. The residual moisture content can be adjusted by appropriately selecting the conditions for the post-coating baking process described later.

C-8. Resin Film Thickness The resin film thickness is preferably 0.03 to 1.0 μm after baking and drying.

C-9. Resin film-forming base resin and lubricant as essential components and surfactant as an optional component, the above additives are added appropriately to this, and a paint in which these are dissolved or dispersed in an appropriate solvent is directly applied onto the chemical film, It is baked and dried by treating for a predetermined time in an oven at a predetermined temperature. As the solvent, water, alcohols, ketones and the like are used, but it is preferable to use water.

(A) Adjustment of surface roughness of resin film surface Metal plate to be used so that the surface roughness is 19 to 781 per 1 mm ^{2 on the} surface of the resin film. The average surface roughness and the film thickness of the resin film are adjusted, and the cooling method after baking is further adjusted. First, the average surface roughness of the metal plate to be used is preferably 0.13 to 0.60 μm. In order to obtain such an average surface roughness, a method of rolling using a rolling roll adjusted to an appropriate surface roughness in the rolling process of the metal plate, a method of etching and polishing under appropriate conditions, A method of performing shot blasting or the like is used. Moreover, it is preferable to adjust the film thickness of the resin film after baking and drying to 0.03 to 1.0 μm or less. The arithmetic average roughness Ra of the resin film surface is preferably 0.10 to 0.54 μm. This is because if Ra is less than 0.10 μm, the conductivity tends to be inferior, and if it exceeds 0.54 μm, scratches on the resin film tend to be noticeable, so that the scratch resistance tends to be inferior.

  The resin film contains a lubricant, and the distribution of the lubricant that affects the surface roughness is affected by the cooling method after baking. Specifically, it is necessary to cool for 4 to 20 seconds by blowing air at room temperature. In the method of spraying water at room temperature, since the lubricant is separated from the resin film and emerges on the surface layer, the scratch resistance is poor.

(A) Adjustment of the lubricant occupancy ratio on the surface of the resin film The sum of the lengths of the lubricant particles that can be cut by any one straight line having a length of 100 μm on the surface of the resin film is 10 to 80 μm. The lubricant is added to the coating material in advance by adjusting the average particle size and amount of the lubricant so that the occupation ratio is 10 to 80%. In this case, specifically, a lubricant having an average particle size of 1.5 to 7.0 μm is used, and the lubricant is added in the range of 1 to 15% by weight with respect to the base resin, and The desired lubricant occupancy can be obtained by baking by the method described in (1).

  In baking after painting, when the paint is heated, the temperature rises while convection, but when the temperature of the paint exceeds the melting point of the lubricant, the lubricant becomes liquid and is stirred by the convection of the paint. What has leached to the surface wets and spreads on the surface because the surface energy is smaller than that of the base resin. Since the thickness of the resin film is remarkably thin as compared with the average particle diameter of the lubricant, most of the lubricant particles are likely to leach out on the surface of the resin film.

  When the temperature is further raised, the curing reaction of the base resin is started, and the lubricant particles are fixed in the resin film. In order to obtain the lubricant occupation ratio in the present invention, as shown in FIG. 2, in the process (P1) from TR (room temperature) to the temperature T1 (melting point of the lubricant + 6 ° C.) at which the lubricant is completely melted, Increase the temperature quickly. Here, the reason why T1 is set to the melting point of the lubricant + 6 ° C. is that the lubricant is sufficiently melted by being raised by 6 ° C. above the melting point. In the subsequent process (P2), the temperature is increased more slowly than in P1 until T2, which is a temperature at which the base resin is cured to some extent. In the next step (P3), the temperature is increased more slowly than in P2 until the final temperature T3 at which the base resin is sufficiently cured, and the state of the temperature T3 is maintained for a predetermined time.

  In FIG. 2, the time t1 seconds of the process P1 until reaching TR to T1 is preferably 10 seconds or less. When t1 seconds exceeds 10 seconds, the solvent that dissolves or disperses the paint components evaporates and the viscosity of the paint rises, and even if the resin is kept at a temperature at which the resin is not cured, the lubricant is sufficiently leached to the surface. This is because it may not come.

  The temperature T2 at which the resin is cured to some extent and the lubricant is fixed in the process of P2 is a temperature that is 20 ° C. lower than the final temperature. When the time from the start of baking to the time T2 which is 20 ° C. lower than the final temperature reached is t2 seconds, that is, the time (t2−t1) of the process P2 is preferably 15 seconds or less. This is because if (t2-t1) exceeds 15 seconds, the lubricant particles may associate and become too large. The final temperature at which the base resin is sufficiently cured may be determined so that the performance of the base resin is best exhibited, and is usually 170 to 300 ° C.

  In order to perform coating on a metal plate at a low cost, a method of continuously coating with a roll coater using a coil is most suitable. When painting by this method, since the paint is baked in a baking furnace divided into several zones, it is necessary to have a relationship between temperature and time as shown in FIG. Further, the total baking time t3 is preferably 10 to 60 seconds, and more preferably 20 to 45 seconds. In addition, it may replace with a roll coater and may apply | coat a coating material with an air spray, a bar coater, etc.

Hereinafter, the present invention will be described in detail with reference to examples.

Examples 3-5, 12, 14-17
As the metal plate, an aluminum alloy plate having a predetermined average surface roughness (material: JIS
A5052, grade: H34, plate thickness: 0.6 mm). Both surfaces of this aluminum alloy plate were degreased using a commercially available alkaline degreasing solution, and further subjected to a chemical conversion treatment using a commercially available phosphoric acid chromate treating solution. Various paints having the compositions shown in Table 1 were baked on one side of the aluminum alloy plate under the respective conditions to prepare samples. Baking was performed using a hot air drying furnace consisting of two zones, and the ambient temperature in each zone was defined by the times t1 and t2 shown in FIG. 2 so that the final temperature shown in Table 1 was obtained. The final temperature reached was measured with a thermocouple. Cooling after painting was performed by blowing air at room temperature.

Example 6
The same aluminum alloy plate as in Examples 3 to 5 was used for the metal plate. Both surfaces of the aluminum alloy plate were degreased using a commercially available alkaline degreasing solution, subjected to an acid cleaning treatment with dilute sulfuric acid, and then subjected to a chemical conversion treatment using a commercially available zirconium treating solution. Then, to create a sample in the same manner as in Example 3-5.

Examples 11-12
In Example 11, a stainless steel plate was used as the metal plate, and in Example 12, a galvanized steel plate was used as the metal plate. Both surfaces of these metal plates were subjected to a degreasing treatment using a commercially available alkaline degreasing solution, and further subjected to a chemical conversion treatment using a commercially available phosphoric acid chromate treating solution. Subsequently, the sample was created like Example 1-5.

Comparative Examples 1-8, 10, 11
The same aluminum alloy plate as in Example 1 was used for the metal plate. Both surfaces of this aluminum alloy plate were degreased using a commercially available alkaline degreasing solution, and further subjected to a chemical conversion treatment using a commercially available phosphoric acid chromate treating solution. Next, samples were prepared in the same manner as in Examples 1 and 3 to 5. In Comparative Example 10, no resin film was formed.

As a result of measuring the film amount of the chemical conversion film obtained by the above-described method using a fluorescent X-ray analyzer, the chromium content was 30 mg / m ² and the zirconium content was 10 mg / m ² .

For precoated metal sheet samples prepared in Examples 3～6,11,12,14～17 and Comparative Examples 1～8,10,11, arithmetic average roughness (Ra) of the resin film surface, or Ra of 1 mm ² per The number of protrusions, the occupation ratio of the lubricant on the resin film surface, and the residual moisture content in the resin film were measured by the following methods. Furthermore, the electrical conductivity and scratch resistance of the pre-coated metal plate sample were measured by the following methods, and ◎, ○, ○ △ were accepted and Δ, × were rejected according to the following evaluation criteria.

<Surface roughness of resin film surface>
The measurement was performed using a laser tech Co., Ltd. confocal microscope HD100. Arithmetic that exists on a straight line that passes through the protrusion at the maximum height and intersects perpendicularly to the rolling direction in an area of 322 μm square selected arbitrarily by measuring a three-dimensional image of the resin film surface with an objective lens 50 times. Average roughness Ra was measured according to JIS B0601. A three-dimensional image consisting only of protrusions with a height of Ra or higher was created in the area of 322 μm square. At this time, the filter size of the median filter was set to 5 * 5. Then, by measuring the number of projections present in the image, it was converted to the number per 1 mm ^2. Five measurement points were arbitrarily selected and measured five times, and an average value was calculated for Ra and the number of peaks per 1 mm ² .

<Occupancy ratio of lubricant on resin film surface>
A cross section perpendicular to the surface of the resin film was observed with a transmission electron microscope over a length of 100 μm, and the sum of the lengths of the lubricant particles existing on the surface of the resin film was measured. Such cross sections were arbitrarily selected and observed at five places. The arithmetic average of the sum of the lengths of the cut lubricant particles for each cross section was calculated, and the ratio with respect to the length of 100 μm was defined as the occupation ratio of the lubricant.

<Residual moisture content>
The weight (M1) of the resin film was weighed. Next, the weight (M2) of the resin film after heating for 1 hour in an oven at a temperature of 105 ° C. was measured, and (M1−M2) × 100 / M1 was calculated to calculate the residual moisture content of the resin film.

<Conductivity>
The electrical resistance value was measured when a steel probe having a tip radius of 5 mm was brought into contact with the pre-coated metal plate sample with a load of 500 gf.
◎: 2Ω or less ○: Over 2Ω to 10Ω or less ○ △: Over 10Ω to 100Ω or less △: Over 100Ω to 200Ω or less ×: Over 200Ω

<Scratch resistance>
About the precoat metal plate sample, the steel ball was slid 10 times with the load of 500 g, the Bowden type friction test was done, and the sample external appearance was observed.
◎: Slightly flaws are observed ○: Slightly flaws are observed ○ △: Scratches are observed, but the material is not reached △: Scratches are observed and the material is reached ×: Remarkable Scratches are observed

Table 2 shows the test results of Examples 3 to 6, 11, 12, 14 to 17 and Comparative Examples 1 to 8, 10, and 11.

In the pre-coated metal plate samples of Examples 3 to 6 , 11 , 12 , and 14 to 17 , the number of protrusions having an arithmetic average roughness Ra (μm) or more is in the range of 19 to 781 per mm ² , And the scratch resistance was good.

Examples 3-6 and 11 and 12, the precoated metal sheet samples 14 to 17, the occupancy rate of the lubricant is in the range of 10% to 80%, the performance of both conductive and scratch resistance Re Yu It was.

In the precoated metal plate samples of Comparative Examples 1 to 4, the number of protrusions having an arithmetic average roughness Ra (μm) or more on the resin film surface was less than 19 per 1 mm ² , so that the conductivity was inferior.
In the precoated metal plate samples of Comparative Examples 5 to 8, the number of protrusions having an arithmetic average roughness Ra (μm) or more exceeded 781 per 1 mm ^{2 on the} surface of the resin film, so that the scratch resistance was poor .
Since the metal plate of Comparative Example 10 was not formed with a resin film, the scratch resistance was poor.
The precoated metal plate of Comparative Example 11 was inferior in scratch resistance because no lubricant was added.

  Good electrical conductivity and scratch resistance can be obtained by the pre-coated metal plate for a drive case having a specific surface roughness shape in the resin film. Furthermore, the balance between good scratch resistance and electrical conductivity can be increased by the specific lubricant occupation ratio on the surface of the resin film.

FIG. 1 is a schematic diagram visually showing the presence of lubricant particles on the surface of a resin film. FIG. 2 is an explanatory diagram showing the relationship between the temperature change in the paint baking process, the process of melting the lubricant, and the temperature at which the base resin is cured in the manufacturing process of the pre-coated metal sheet for drive case of the present invention.

Explanation of symbols

1 Metal plate 2 Chemical conversion film 3 Resin film 41, 42 Lubricant particles,
5 ······ Line of 100 µm length d1, d2, d3, d4, d5, d6 ··· Length of lubricant cut M1 ··· Weight of resin film before heating M2 ··· After heating Weight of the resin film at P1 ... Process from room temperature to temperature T1 P2 ... Process from temperature T1 to temperature T2 P3 ... Process from temperature T2 to end of baking t1 ... From baking start to temperature T1 Time to reach t2 ... Time from start of baking to temperature T2 t3 ... Total baking time T1 ... Temperature at which the lubricant completely melts T2 ... Temperature at which the base resin hardens to some extent T3 ... ... Final baking temperature TR ... Room temperature

Claims (2)

A precoat metal plate for a drive case comprising a chemical film formed on both surfaces of a metal plate, and a resin film formed on one of the chemical films and containing a base resin and a lubricant,
The average surface roughness of the metal plate is 0.13 to 0.60 μm,
The resin film has a thickness of 0.03 to 1.0 μm,
The base resin is at least one selected from the group consisting of an acrylic resin, an epoxy resin, a urethane resin, and a polyester resin;
On the surface of the resin film, the arithmetic average roughness Ra (μm) on a straight line that passes through the protrusion of the maximum height and is orthogonal to the rolling direction of the metal plate is 0.10 to 0.54 μm, and Ra There are 19 to 781 protrusions per 1 mm ² ,
The residual moisture content of the resin film in the Ri 0.001 to 0.7 wt% der,
The resin film further contains a surfactant, and the lubricant comprises at least one of polyethylene wax and carnauba wax,
The resin in the film surface, the length 100μm the lubricant drive case for precoated metal sheet the sum of the length, characterized in 10~80μm der Rukoto particles of any one straight line cuts the. The precoat metal plate for a drive case according to claim 1 , wherein the resin film is formed by spraying air at room temperature for 4 to 20 seconds and then cooling after baking.

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