JP2782700B2 - How to add patterns to molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a concavo-convex pattern on the surface of a molded article when the molded article is molded by injection molding.

[0002]

2. Description of the Related Art Conventionally, in the case where some irregularities are to be formed on the surface of a molded product, desired irregularities are formed on a surface of a molding die for molding the surface, and the irregularities are formed. It was copied on the product, showing the uneven pattern on the molded product.

[0003]

However, according to this method, since a mold for forming the surface of a molded article has irregularities,
The uneven surface of the mold must be finished with an accuracy corresponding to the finishing accuracy of the surface of the molded product, and an extremely high degree of finishing is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to present a soft uneven pattern on a molded product without forming irregularities on a mold on the surface of the molded product. .

[0005]

According to the method of the present invention, a convex portion and a concave portion are formed on the back surface of a molded product by injection molding, and the volume of the convex portion is changed by cooling and solidification of the molten resin during molding. And a convex portion on the surface corresponding to the concave portion.

In general, when plastic is injection-molded, if the molded product has a thick portion and a thin portion,
When the molten resin is cooled and solidified in a mold at the time of molding, a difference in the solidification rate occurs due to a difference in thickness. Therefore, solidification is delayed particularly in a thick portion, volume shrinkage occurs, the surface is depressed, and sink occurs.

The present invention makes use of this phenomenon to form irregularities on the back surface of a molded product to give a change in thickness.
A sink is positively generated on the surface, and the pattern appears by the sink.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a plate-like molded product on the surface of which a Mickey Mouse pattern is shown by a concavo-convex pattern by the method of the present invention, and FIG. 2 is an II-II enlarged sectional view thereof.

Reference numeral 1 denotes a molded product, on the back surface of which a ridge 2 as a projection is formed along the contour of the pattern of Mickey Mouse, and the surface corresponding to the ridge 2 has sink marks. A concave groove 3 is formed as a concave portion, and the outline of the symbol of Mickey Mouse is drawn by the concave groove 3.

[0010] Further, a concave portion 4 as a concave portion is formed on the back surface of the molded product 1 at the position of the eye in the pattern of the Mickey Mouse, and the thickness of the molded product 1 is smaller than other portions. Therefore, the volume shrinks evenly in portions other than the recesses 4, and no shrinkage occurs in the recesses 4. As a result, a bulging portion 5 due to shrinkage is generated on the surface of the position of the recesses 4, and becomes a convex portion.

Therefore, the mold surface for molding the surface of the molded product 1 is smooth, and the back surface of the molded product 1 is formed despite no work for molding the concave groove 3 and the bulging portion 5. On the basis of the ridges 2 and the recesses 4 formed in the mold, a volume change occurs during cooling and solidification of the molten resin at the time of molding, and a concave groove 3 and a bulging portion 5 are formed on the surface of the molded article 1. Because

The width of the groove 3 is increased by increasing the width of the ridge 2 formed on the back surface of the groove 3. When the protruding height of the ridge 2 increases, the depth of the concave groove 3 becomes deeper. However, when the protruding height of the ridge 2 becomes substantially equal to or greater than the thickness of the molded product 1, the concave groove 3 becomes concave. The depth of the groove 3 hardly changes.

In general, if the width of the ridge 2 is smaller than the thickness of the molded article 1, the sink marks appearing on the surface are inconspicuous.
By forming a groove 6 on the back surface of the molded product 1 along both sides of the ridge 2 ′ like the ridge 2 ′ in the inside, a concave groove 3 ′ with a small width appears on the surface. Can be.

The bulging portion 5 can also have a high bulging height by increasing the depth of the concave portion 4. Article 1
Therefore, it is appropriate that the depth of the recess 4 is limited to about の of the thickness of the molded product 1.

[0015]

According to the present invention, by forming the ridges 2 and the recesses 4 on the back surface of the molded product, the concave grooves 3 and the bulging portions 5 appear on the surface due to the volume change due to the slow cooling and solidification of the molten resin. The pattern can be shown by the concave groove 3 and the bulging portion 5.

Generally, in plastic injection molding, sink is treated as a defect in molding, and it is said that it is better to mold so that sink does not occur and to make it less noticeable.

On the other hand, in the present invention, sink marks are positively generated on the surface of a molded product, thereby expressing a desired pattern.

[0018]

According to the present invention, the irregularities formed on the back surface of the molded article 1 show irregularities due to a volume change in the cooling and solidification of the molten resin on the surface. There is no need to form irregularities showing a pattern on the surface. Therefore, the mold surface is a simple smooth surface and can be easily finished with high precision.

Further, it is necessary to form an uneven mold for forming the ridges 2 and the recesses 4 in the mold for forming the back surface of the molded product 1. Often do not appear, and a highly precise finish is not required.

Therefore, according to the present invention, it is easy to design and manufacture a mold, and a desired uneven pattern can be formed on the surface of the molded article 1.

Further, the uneven pattern presented by the present invention is based on the volume change in the cooling and solidification of the molten resin that has appeared on the surface based on the unevenness on the back side, so that the unevenness on the surface is smooth and the pattern with an extremely soft impression is obtained. Can be expressed.

Further, the molded article 1 showing the pattern according to the present invention is heat-treated to cause thermal contraction, thereby emphasizing the concave portions 3 and the convex portions 5 appearing on the surface, and making the pattern clearer. it can.

[Brief description of the drawings]

FIG. 1 is a front view of a molded product showing a pattern according to the present invention.

FIG. 2 is an enlarged sectional view taken along the line II-II of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Ridge (convex part) 3 Depressed groove (depressed part) 4 Depressed part (depressed part) 5 Swelling part (convex part)

Claims (1)

(57) [Claims] 1. A convex part (2) and a concave part (4) are formed on the back surface of a molded article (1) by injection molding, and the convex part (2) is formed by a volume change in cooling and solidification of a molten resin during molding. ) And a projection (5) on the surface corresponding to the depression (4), respectively.