JPS62238746A - Modified screen printer - Google Patents

Abstract

PURPOSE:To provide a screen printer capable of generating no angular change between a screen and a printing table by curving the surface of a printing table upward in a concave form so that the angle between the screen and the surface of the printing table may be constant or almost constant regardless of squeegee movement. CONSTITUTION:On an ink-holding part of the tip of a squeegee the surface of a printing table is curved upward in a concave form in such a way that the angle between a screen and the surface of the printing table may be constant or almost constant regardless of squeegee movement. The locus P (x, y) of this surfacial form is as shown by the following equation: where the ends of the screen are represented by (0, 0), the ends of the opposite side by (2a, 0), the position of the horizontal center by (a, S), the angle with 'x' axis of the cross section OP of the screen by theta1, the angle with 'x' axis of a tangent 6 against a locus on the upper surface of the printing table at P by theta2, theta1-theta2=alpha (constant), and G is a constant. Thus the throughput of ink can be kept constant so that a density dispersion may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field and Object of the Invention No. 1311 relates to improved performance in screen printing.

Screen printing is performed using screen 1 as shown in Figure 1.
Tightly fix the four circumferences of (woven fabric of net f'l h) to the printing frame 4,
A resist film is made on the ball manually or photochemically, and screen printing ink is put into the shallow ark-shaped inside of the eye, and the inner surface of the eye is rubbed with pressure using a squeegee 2. This is a method in which printing is performed by extruding ink from the part of the printing plate 11 through the screen surface onto the surface of the printing material placed on the bottom surface of the printing plate.

In conventional screen printing, as shown in FIG. 2(d), the upper surface of the printing table 3 is flat, and both frames of the screen are fixed, so the squeegee moves as the squeegee moves. The angle α between the ink-holding screen and the printing table at the position P of the tip of the screen will change (in fact, in Fig. 2(a), the angle α1 and the angle α2 are different in size. ).

However, in the part of the squeegee that holds ink, the length projected in the direction of the surface of the printing table of the screen mesh is 0080 times, so the change in α means that the length of the mesh of the screen projected toward the surface of the printing table is This means that the length projected in the direction of the surface changes (in order to make this point easier to understand, the second
(b) The figure shows an enlarged view of the contact between the screen and the printing table).

For this reason, on the ink-holding side of the squeegee, changes in the angle between the screen at the tip of the squeegee and the printing table cause an imbalance in the passage of ink and cause uneven ink density. Cause.

It is an object of the present invention to provide a screen printing machine that does not cause changes in the angle between the screen and the printing table that cause density unevenness.

(Structure of the Invention #t) As shown in FIG. This is achieved by forming the surface of the printing table into an upwardly concave curved shape so that the printing table remains constant or almost constant regardless of the movement of the print table.

The following will explain whether or not the upper surface of the printing table can be formed at a constant angle with the screen, and what mathematical formula can be used to express this.

Figure 4 is a graph for analyzing the surface shape of such a printing table. - The locus P (x, y) of the surface shape that satisfies the above requirements is found by solving the following differential equation. .

In Figure 4, the end of the screen on the side where the squeegee holds ink is (0, O), and the opposite end is (0, O).
2a, 0), and the position of the horizontal center of the printing table is (a, S).

If the angle of the cross section OP of the screen with respect to the X-axis (horizontal direction) is O1, and the angle of the tangent 6 to the locus of the surface of the print table of the present invention at P with respect to the X-axis is 02, then y/x= tar+01, dy/dx= tana
2 (d is the differential notation -))゛.

On the other hand, 01-02 = α (constant), °, dy / d x = tan (θ5-a
)=(tan(71-tana)/(1+tan
θ+ tana)=(y-xtanα)/(x+
If y tana)y /
na) dt/ (1+t2)=08 tanct l
ogx+ tan-' t+ (tana/2)
log(1+t2) = C (C is a constant) When x=a, y=S, so C= tan' (S/a) + (tanoc/2) log (a2-1-52
)・°・jan”1 (y/x)+ (tana/2) log (x2 + 72)
= jan' (S/a) + (tana/2) log(a2 +52) The surface shape of an ideal printing table with a constant angle with the screen can be expressed by a complex equation. However, it becomes clear that it exists.

Although it is extremely difficult to actually obtain a curved surface with a trajectory like the one described above, it is possible to design a curved surface that approximates such a trajectory and make the angle with the screen almost constant.

In order to actually obtain a trajectory based on such an equation or a shape approximating it, it is best to calculate and set it using a computer based on given initial conditions.

(Effects of the Invention) By designing the top surface shape of the printing table as in the present invention, the angle between the screen and the top surface of the printing table on the ink holding side of the tip of the squeegee is can be kept constant or almost constant regardless of the movement of the screen, so the component of the opening of the screen toward the surface of the printing table is always constant, and the ink passage 1fY is also kept constant, so the relationship between the screen and the surface of the printing table is kept constant. This is extremely effective as it can prevent uneven density from occurring due to changes in angle.

[Brief explanation of the drawings] Figure 1: Schematic diagram showing the outline of Ni-screen printing, Figure 2 (a)
Figure: Cross-sectional view showing that the angle between the screen and the upper surface of the printing table changes as the squeegee moves. Figure 2 (b). Cross-sectional view showing the part where the screen and the printing table come into contact. Figure 3. Cross-sectional view showing the configuration of the invention Figure 4: Graph for analyzing the surface shape of the printing table of the invention

Claims (1)

[Claims] On the side of the tip of the squeegee that holds ink, the surface of the printing table is curved upward in a concave shape so that the angle between the screen and the surface of the printing table remains constant or almost constant regardless of the movement of the squeegee. An improved screen printing machine characterized by