JP2740617B2 - Epoxy resin composition suitable for laser printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition suitable for laser printing, which is used for insulating coating of electric / electronic parts and which can apply clear laser irradiation to the surface of the insulating coating. It is.

[0002]

2. Description of the Related Art Conventionally, thermosetting and ultraviolet curable inks have been used for printing on electric / electronic parts insulated with an epoxy resin composition to specify characteristics and model numbers. For the purpose of streamlining the process, a method for printing in a shorter time has been demanded. As one of the methods to cope with this, a printing system using laser irradiation has attracted attention. In this laser printing system, the parts irradiated with laser in the form of letters or patterns are discolored by heat energy, or the irradiated parts are sublimated and the surface is roughened, and letters and patterns can be identified by scattering of light. is there. The printing time of this method is 0.01 second or less, which is much shorter than the conventional heat or ultraviolet curable ink requiring several minutes to several tens of minutes for curing. However, when a conventional insulating coating of an epoxy resin composition is irradiated with a laser, discoloration does not occur simply by roughening the coating surface, and clear characters and patterns cannot be printed.

[0003] Recently, it has been found that when a conventional epoxy resin composition contains yellow ferric hydroxide, the color changes from yellow to brown by laser irradiation (Japanese Patent Application Laid-Open No. Sho 62-62).
No. 50360). However, since ferric hydroxide is yellow, it can be used only for a hue such as yellow or orange, and black laser printing on a blue or green base, especially a light-colored base, or conversely brown or black It has been an issue to perform white laser printing on the underlayer.

[0004]

SUMMARY OF THE INVENTION The present invention has been intensively studied to obtain a resin composition which develops from a dark color such as brown or black to a white color with a laser, which was impossible in the prior art. Have been found to develop a white color when irradiated, and based on this finding, they have conducted various studies and completed them. It is an object of the present invention to provide an epoxy resin composition which gives a cured product capable of giving a clear print on a resin surface by irradiating a laser without deteriorating electric characteristics and other various characteristics. is there.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an epoxy resin composition suitable for laser printing, characterized by containing magnesium oxalate. The reason for using magnesium oxalate in the epoxy resin composition of the present invention will be described below. Magnesium oxalate is a white powder, but when heated, decarboxylates at 150-250 ° C to change to magnesium oxide. Magnesium oxide is white, like magnesium oxalate, but has greater hiding power than magnesium oxalate. Therefore, when the laser is irradiated in a letter or pattern on the epoxy resin composition containing magnesium oxalate, the resin surface is heated by the thermal energy of the laser, and the magnesium oxalate contained in the resin causes the above chemical reaction. . At this time, if this resin composition is toned in a dark color with an appropriate pigment, only the portion irradiated with the laser has a large hiding power and the non-irradiated portion remains the dark color of the base, so that the base is dark. White characters and patterns can be printed clearly.

The average particle size of the magnesium oxalate used in the present invention is preferably 100 μm or less. The reason is that when magnesium oxalate is mixed and dispersed in the epoxy resin composition, if the average particle diameter is 100 μm or more, the surface becomes spot-like when coated on electronic / electric parts, which not only reduces the commercial value of the parts but also disperses them. In some cases, when laser irradiation is performed, in a portion where magnesium oxalate does not exist, color or color may not be generated, and characters and patterns may be cut off to make clear printing impossible. The average particle size is suitably determined by weight-averaging the particle size distribution obtained by a Coulter counter (manufactured by Nikkaki), but may be determined by a measuring method other than the Coulter counter. The content of magnesium oxalate is preferably 0.5 to 20% by weight. The reason for this is that if the content is 0.5% by weight or less, the degree of color development is small even when irradiated with a laser, so that clear printing is not achieved.
Conversely, if the content exceeds 20% by weight, the electrical insulation of the resin composition is reduced, and it becomes difficult to satisfy the original performance as an insulating material for electronic components.

The epoxy resin used in the present invention includes, for example, diglycidyl ether type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, phenol novolak type epoxy resin and cresol novolak type epoxy resin. Examples include resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, chain aliphatic type epoxy resins, heterocyclic type epoxy resins, halogenated epoxy resins, and the like, but are not limited thereto. As the curing agent and curing accelerator used in the present invention, acid anhydride, polyamine, novolak type phenol resin,
There are a secondary amine, an imidazole compound and the like, and any of them may be used. If necessary, known inorganic fillers such as zircon powder, talc powder, crystalline silica powder, fused silica powder, calcium carbonate powder, magnesia powder, calcium silicate powder, hydrated alumina powder, alumina powder and the like may be blended. . Since the resin composition obtained by the present invention has a small concealing power of magnesium oxalate and is usually colorless and transparent, various color tones can be obtained by using pigments such as red, blue, green, black, and white. The resin composition of the present invention may be in any state such as a liquid state such as a casting material, a powder state such as a powder coating, a granular state such as a molding material, and a lump.

As a method for producing the resin composition of the present invention, for example, in the case of a powder coating, a raw material component weighed at a predetermined ratio is sufficiently mixed by a mixer and then melted by an extruder, a co-kneader or a roll. There is a method of kneading and then pulverizing with a pulverizer. Examples of the method of performing insulating coating of electronic and electric parts with the powder coating obtained by the above method include general powders such as a fluid immersion method, an electrostatic fluid immersion method, a rolling method, a sprinkling method, a hot spray method, and an electrostatic spray method. There is a body painting method. Also, casting materials and molding materials can be manufactured by known techniques and used as insulating materials.

[0009]

Next, the present invention will be described in more detail with reference to examples. << Example 1 >> bisphenol A type epoxy resin (epoxy equivalent 950) 50 parts by weight Magnesium oxalate (average particle diameter 10 μm) 5 parts by weight Crystalline silica powder 50 parts by weight 2-methylimidazole 1 part by weight The above composition was blended. After blending with a Henschel mixer and melt-kneading with a co-kneader, the mixture was pulverized with a pulverizer to obtain a powder coating of an epoxy resin composition having an average particle size of 60 to 70 μm.

Example 2 A powder coating of an epoxy resin composition having an average particle size of 60 to 70 μm was obtained in the same manner as in Example 1, except that the amount of magnesium oxalate was changed to 20 parts by weight. << Comparative Example 1 >> A powder coating of an epoxy resin composition having an average particle size of 60 to 70 µm was obtained in the same manner as in Example 1, except that the addition amount of magnesium oxalate was changed to 0.1 part by weight. << Comparative Example 2 >> A powder coating of an epoxy resin composition having an average particle size of 60 to 70 µm was obtained in the same manner as in Example 1, except that the amount of magnesium oxalate was changed to 50 parts by weight.

Cured products were prepared from the resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2. The sample was irradiated with laser using a carbon dioxide laser (Ushio 400 model laser mark, energy 6 Joule) through a predetermined mask for 1 / 100,000 seconds to mark the cured product surface. In addition, the dielectric breakdown voltage of the cured product is determined in accordance with JIS K
6911. Table 1 shows the results.

[0012]

[Table 1]

[0013]

According to the present invention, when the epoxy resin composition suitable for laser printing according to the present invention is used as an insulating coating material, clear printing can be performed on the resin surface by laser irradiation without deteriorating the electrical characteristics and other characteristics. Can be provided. Therefore, since printing can be performed in a much shorter time than in the past, the production process of electric / electronic parts can be rationalized.

Claims (3)

(57) [Claims] 1. An epoxy resin composition comprising an epoxy resin, a curing agent, a filler and the like, wherein the epoxy resin composition contains magnesium oxalate. 2. The magnesium oxalate having an average particle size of 10
The epoxy resin composition according to claim 1, wherein the thickness is 0 µm or less. 3. The composition according to claim 1, wherein the composition contains 0.5 to 20 parts by weight of magnesium oxalate.
Or the epoxy resin composition of 2.