JPH0257503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a printing method, and particularly to a printing method suitable for molded articles having a three-dimensional surface shape.

<Prior art and problems to be solved by the invention> Conventionally, when the printing material is a molded product with a complicated three-dimensional surface shape, a pad press method has been used as a method for printing on such printing material. There is. This method involves applying ink to a soft and highly elastic part shaped like an octopus's head, pressing it onto a molded product, and deforming the part to print on a three-dimensional surface. In this method, it is impossible to print on surfaces with complex shapes, such as concave valleys and bottom surfaces. This is because although the pads are made of soft material, there is a limit to the deformation of the pads when the pressure is increased during printing.
Therefore, the ink provided on the pad cannot be brought into sufficient contact with the printing material, resulting in missing prints, and the greater the deformation of the pad, the greater the slippage between the pad and the molded product. This is because there was a problem that the ink would fade or spread, causing the printed image to become distorted. Therefore, the shapes used have been limited to simple convex and concave surfaces.

The present invention is an improved method of the conventional method, and its feature is that it discloses a method that can perform beautiful printing even on molded products with complex three-dimensional surface shapes. The purpose is to

<Means for Solving the Problems> In other words, the present invention involves stretching a stretchable sheet in one direction or two directions in advance, forming a transfer image on the sheet, and then releasing the stretching to stretch the sheet. An impression cylinder having a surface with a reversed shape of the surface shape of the printing material (hereinafter referred to as reversed shape) and a large number of small holes on the surface is pressed against the back side, and suction is applied from inside the impression cylinder. A method for printing on a molded product having a three-dimensional surface shape, which is obtained by deforming a sheet into an inverted shape, bringing it into close contact with an impression cylinder, then pressing a transferred image of the sheet onto the surface of a printing medium, and transferring the transferred image. This could be solved by disclosing the following.

<Function> According to the printing method of the present invention, a sheet is stretched in one direction or two directions in advance, a transfer image is formed on the sheet, and then the stretching is released. Printing is performed by bringing a molded product with a certain three-dimensional shape into close contact with an impression cylinder that has an inverted shape, and then pressing the transferred image of the sheet onto the surface of the printing medium. It adapts well to molded products having three-dimensional shapes, and even if elongation occurs during the step of adapting the transfer sheet to the printing material, it can prevent the printing ink from cracking and the ink concentration from decreasing.

<Example> A more detailed explanation will be given below using the drawings. 1st
As shown in the figure, an elastic and stretchable sheet 1 made of polyurethane, silicone rubber, etc. is attached to an outer frame 2, and then printing is performed using an appropriate printing method using a roll 4 or the like while receiving printing pressure from the back side. , to form a transfer image 3. Next, as shown in FIG. 2, an impression cylinder 5 having a surface inverted from the surface shape of the printing material and having a large number of small holes on the surface is pressed against the back surface of the sheet. By suctioning from inside the cylinder 5, the sheet 1 is deformed into an inverted shape and brought into close contact with the impression cylinder 5.

Here, the impression cylinder 5 is made of an elastic body such as rubber or a rigid body such as wood or metal, and the inverted shape surface may be an inverted shape that approximates the surface shape of the printing material, but in the present invention, It is possible to implement.

Next, as shown in FIG. 3, the three sides of the transfer image of the sheet 1 are pressed onto the surface of the printing material 6 in a state in close contact with the impression cylinder 5, the transferred image 3 is transferred to the printing material 6, and the third surface of the printing material 6 is pressed. As shown in FIG. 4, the printing method of the present invention is completed.

Here, if the surface shape of the printing material is complex and has large irregularities, when the sheet is transformed into an inverted shape, the elongation is large, resulting in cracks on the ink surface, which is the transferred image, and the printing density decreases. It may cause a decrease. In such a case, before forming a transfer image on the sheet surface, as shown in FIG. 5, the sheet is stretched in one direction or two directions, and then a transfer image is formed as shown in FIG. Then, as shown in FIG. 7, after the stretching is released, the sheet is deformed into an inverted shape, thereby making it possible to prevent cracking of the ink surface, which is the transferred image, and a decrease in density due to stretching of the sheet. Note that the stretching rate and stretching direction of the sheet are appropriately selected depending on the surface shape of the printing medium and the printing density.

<Effects of the Invention> The present invention has the above configuration, and when printing on a printing material having a complicated three-dimensional shape, the sheet is pressed by an impression cylinder having a shape that is an inversion of the surface shape of the printing material. Therefore, there is no misalignment or misalignment,
Good printing is now possible, and even if the transfer sheet stretches during the process of adapting it to the molded product, it is possible to prevent the printing ink from cracking and the ink concentration from decreasing.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIGS. 1 to 3 are process explanatory diagrams of the present invention, FIG. 4 is an explanatory diagram of the printing material after printing, and FIGS. 5 to 7 2A and 2B respectively show process explanatory diagrams of the present invention when the surface shape is particularly complex. DESCRIPTION OF SYMBOLS 1... Sheet, 2... Outer frame, 3... Transfer image, 4... Roll, 5... Impression cylinder, 6... Printing material.

Claims (1)

[Claims] 1. A stretchable sheet is stretched in one or two directions in advance, a transferred image is formed on the sheet, the stretching is released, and the surface shape of the printing material is reversed from the back side of the sheet. By pressing an impression cylinder having a shaped (hereinafter referred to as inverted shape) surface and a large number of small holes on the surface and suctioning from inside the impression cylinder, the sheet is deformed into an inverted shape and brought into close contact with the impression cylinder. A method of printing on a molded article having a three-dimensional surface shape, which comprises: then pressing the transfer image surface of the sheet onto the surface of a printing medium and transferring the transfer image.