JPH09309267A - Marking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a contrast of a ground color/black color mark in laser marking on a surface of a plastic molded product. SOLUTION: A surface of a plastic molded product 1 is preliminarily coated with grease (i.e., a film 2 of oils is formed), the surface is irradiated in a shape of a required character or the like with laser beams 4, and an irradiated part 3 is discolored. Thereafter, the grease remaining on the surface is cleanly wiped off. Since diffused reflection of light on the irradiated part 3 is comparatively little, a clear-sharp black mark is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of marking a surface of a plastic molded product with a laser beam, and more particularly to a method of marking black characters or figures.

[0002]

2. Description of the Related Art There are various methods such as a screen printing method for marking black characters and figures on the surface of a plastic molded product. In recent years, a laser has been used for reasons such as low marking cost and convenient material recycling. The marking method has attracted attention and its field of use is expanding. This is shown in Figure 3.
As shown in (A) and (B), the surface of the plastic molded product 1 is irradiated with a laser beam in the shape of a desired character or the like to discolor the irradiated portion 3.

[0003]

This laser marking is generally disadvantageous in that it is difficult to obtain a sufficient contrast. Therefore, when making black markings, the mark will be unclear if the ground color of the plastic molded product is a dark color or a dark color, so it is necessary to limit the ground color to a relatively light color or a light color. There was a problem.

It is an object of the present invention to solve the above problems and provide a marking method capable of marking clear characters and figures on the surface of a plastic molded product.

[0005]

In order to achieve this object, according to the present invention, in claim 1, at least a part of the surface of a plastic molded article is preliminarily coated with oil, and the portion coated with the oil is The marking method is to selectively irradiate the surface with a laser beam to change the color of the irradiated portion.

According to a second aspect of the present invention, there is provided a marking method in which the surface of the plastic molded product is selectively irradiated with a laser beam to discolor the irradiated portion, and then the pores generated in the irradiated portion are filled with oils. .

That is, when marking is performed by these methods, oil (grease etc.) is generated in the pores formed in the laser beam irradiation portion.
As a result, the diffused reflection of light from the irradiated portion (that is, the mark portion) is reduced, and as a result, the mark becomes sharp. This operation will be described with reference to FIG. FIG. 3A schematically shows a cross section of a mark which is simply irradiated with a laser beam. When the surface of the plastic molded product 1 is irradiated with a laser beam, the irradiated portion 3 is discolored by heat, and a large number of pores are generated as if the surface portion melted and foamed. As a result, the light is diffusely reflected and appears lighter than the level at which it is originally discolored, and the mark becomes unclear.

On the other hand, in the mark formed by the method of the present invention, as shown in the schematic cross section of FIG. 2B, the pores of the irradiation portion 3 are filled with oils.
Diffuse reflection is reduced, and the mark looks sharp with a color close to the original level of discoloration.

[0009]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing an embodiment of the present invention. In the figure, 1 is a plastic molded product, 2 is an oil film, 3 is an irradiated portion, and 4 is a laser beam. The plastic molded product 1 is a body to be marked, for example, A
Made of BS resin.

First, a low volatility oil (eg, grease) is applied to the surface (at least the marking area) of the plastic molded product 1 to form the oil film 2.
Next, the surface is irradiated with the laser beam 4 in the shape of a desired character or the like. The irradiated portion 3 is discolored to black from the ground color by heat, and the pores generated by heat are filled with oils applied in advance. Next, the oil film 2 remaining on the surface is wiped off. At that time, a solvent such as alcohol may be used.

Another embodiment of the present invention will be described. First,
Similar to the prior art, first irradiate the surface of a plastic molded product similar to the above with a laser beam in the shape of a desired character,
Discolors the irradiated area blacker than the ground color. Next, oil having low volatility (for example, grease) is applied to the region including the irradiated portion, and the oil is filled in the pores generated in the irradiated portion.
Then, the oil remaining on the surface is wiped off.

[0012]

As described above, according to the present invention,
In laser marking on the surface of plastic molded products, diffuse reflection of light at the laser beam irradiation part is reduced,
It is possible to obtain clearer letters and figures than before, to perform laser marking on the surface of a plastic molded product having a darker color than before, and to shorten the marking time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a diagram for explaining a laser marking method.

[Explanation of symbols]

 1 Plastic molded product 2 Oil film 3 Irradiated part 4 Laser beam

Claims (2)

[Claims] 1. A method comprising the steps of applying oils to at least a part of the surface of a plastic molded article in advance, and selectively irradiating the surface of the oil-applied part with a laser beam to discolor the irradiated part. Characteristic marking method. 2. A marking method, which comprises selectively irradiating the surface of a plastic molded product with a laser beam to change the color of the irradiated portion, and then filling the pores formed in the irradiated portion with oil.