JPS59155075A - Thermal printer - Google Patents

Abstract

PURPOSE:To enable to securely transfer an ink at a boundary part, by a method wherein an elastic member for a platen corresponding to a group of heating resistor elements is provided with a projected part so slanted as to have a smaller height on the lower side. CONSTITUTION:An end edge of the projected part 9a of the elastic member 9 fixed to a supporting frame 10 for a flat platen is made to be a slanted surface having a smaller height on the lower side, and the width of the slanted surface is set to be not smaller than a recording width L1. When a thermal head 1 is pressed to the platen side at a fixed pressure, the reaction force from the elastic member 9 is smaller on the lower side, and is larger on the upper side, so that the efficiency of transfer onto a recording paper 4 by the heating resistor element group 2 arranged in the recording width L1 and a transfer ink ribbon 3 is made to be substantially uniform, including a part overlapping with an ink layer 2 formed in the preceding cycle. Accordingly, it is enabled to avoid the problems that density is lowered at an upper end part in the direction of the recording width L1 and the boundary part becomes conspicuous.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a thermal printer, and more particularly to a thermal printer with an improved structure of a platen that is pressed against a heating element or printing paper via a thermal transfer ink ribbon. .

Prior Art A platen used in a conventional thermal printer has a structure as shown in FIGS. 1 and 2.

The example shown in FIG. 1 uses a platen with a circular cross section. In the figure, reference numeral 1 indicates a thermal transfer ink ribbon 3 running between a thermal head and a circular platen 5 covered with a member. Printing is performed on the printing paper 4 that is guided along.

On the other hand, Figure 2 shows an example using a flat platen.

The reference numeral 6 indicates an elastic body portion of the flat platen.

As shown in Figure 3, the distribution becomes crescent-shaped, with the center being strong and the upper and lower ends being weaker.

As a result, the central portion in the 1,000-direction direction is collapsed, and the upper and lower ends become thinner, as shown in FIG. 4(A), for example.

As a result, in a serial printer that sequentially performs printing with a constant width in the direction in which the elements are arranged, the boundaries of the printing width Ll become thinner, making those parts more noticeable, and the printing quality deteriorates.

On the other hand, a flat platen as shown in FIG. 2 can eliminate the drawbacks of a round platen, but is not necessarily effective in a thermal printer using a transfer ink ribbon.

That is, in the case of serial recording as shown in FIG. 5, the thermal head 1 must be pressed through the transfer ink phone 3 for the current recording while the previously recorded ink layer 7 is overlappingly heated.

For example, the ink layer is formed by applying ink to a thickness of about 49/m2, and the actual thickness is about 4μ.

Even with such a small thickness, if printing is actually performed with overlap, the thermal head section is sufficiently flat, so the ink layer 7 that was printed previously will swell up, as shown in Figure 5. As shown in the enlarged view, the thermal head hits one side, creating an elongated triangular gap 8.

This gap 8 may be absorbed to some extent by the elastic body portion of the flat platen, or theoretically it may not be absorbed, and as shown in Figure 6, the upper edge of the black area in the recording width L1 direction becomes thinner, and as a result, the boundary The result is a record where some parts stand out.

Although such a drawback is tolerated in printers such as character printers that have a recording blank area of a constant width at recording boundaries, it is extremely inconvenient in image printers where the recording width is continuous.

This tendency is caused by the fact that when color recording is performed using a thermal transfer method, the ink layer is not as thick as one color, but for example, when color recording is performed using three colors, yellow, magenta, and cyan, the ink layer is thick enough for three colors at most. and further increases.

Purpose The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional printer, and an object of the present invention is to provide a thermal printer that is capable of reliably transferring ink at boundary portions. .

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

First Embodiment FIGS. 7 and 8 illustrate the first embodiment of the present invention, and are shown as an example applied to a flat platen.

That is, the reference numeral 9 is an elastic member having a substantially convex cross section, and is fixed to the support frame 10 of the flat platen.

The end surface of the protruding portion of the elastic member 9 is a protruding portion 9a, and the edge thereof is an inclined surface. This inclined surface is formed so that the lower side is lower.

A guide sheet 11 is made of a material with a low coefficient of friction such as Tefcon, covers the elastic member 9, and is fixed to the upper and lower ends of the back surface of the support frame 10. Therefore, the kite sea 1-11 forms part of a polyhedron on the side facing the thermal head, as shown in FIG.

Further, the width of the slope 9a of the elastic member 9 is at least as wide as the recording width.

Next, the functions of the platen configured as described above will be explained.

When the thermal head is not in contact with the platen, the elastic member 9 maintains an inclined surface as shown in FIG. 8(A).

On the other hand, in a printing state where the thermal spatula 1- is pressed against the platen side with a constant pressure as shown in FIG. 8(B), the reaction force received from the elastic member 9 is downward as shown in FIG. 8(C). It gets smaller and bigger upwards.

In other words, areas that overlap with the previous ink layer and have a large gap forming an elongated triangle receive a strong repulsive force.
This offsets the conventional reduction in transfer efficiency caused by gaps.

Therefore, it is possible to provide uniform transfer efficiency in the recording width direction, without causing recording unevenness in the recording width direction, and without making the boundary part stand out.

Second Embodiment FIG. 9 explains another embodiment of the present invention. In this embodiment, the case is applied to an apparatus such as a color printer that performs transfer recording of three colors simultaneously in one scan. It shows.

In other words, the elastic members l and 2 used in this embodiment are formed with three protrusions 12a to 12C in a stripe shape separated by a predetermined distance in the recording width direction, and the end surface of each protrusion is The bottom side is a slope that gets lower.

On the other hand, the one indicated by the reference numeral 13 is a thermal transfer ink ribbon.
In the image, yellow stripes start from the bottom.

Thermal transfer inks of macenta and cyan colors are applied.

Then, heating resistor element groups 1' are arranged corresponding to each of these colors.
Thermal heads 14 are arranged such that 4a to 1.4C are arranged.

By adopting such a structure, as described above, it is possible to prevent a decrease in transfer efficiency due to a gap caused by an overlap with the previously transferred ink layer, and to prevent uneven recording at the boundary portion.

Effects As is clear from the above explanation, according to the present invention, a protrusion is provided on the elastic member side of the platen corresponding to the heating resistor element group of the thermal blink using a sheep platen, and the end face of the protrusion is Since it adopts a structure that is tilted downward, it is possible to record without transfer unevenness at the C1 boundary without reducing the transfer efficiency caused by the overlap between the previously printed ink layer and the ink ribbon. can.

[Brief explanation of the drawing]

Figures 1 and 2 are side views showing examples of conventional crosspieces with different Q, Figure 3 is an explanatory diagram showing the reaction force distribution from the platen side when a round platen is used, and Figure 4 (A). is an explanatory diagram showing an example of a pattern to be transferred, FIG. 4 (°B) is an explanatory diagram showing a state of transfer using a round platen, and FIG. 5 is an explanatory diagram of a state of recording using a flat platen. FIG. 6 is an explanatory diagram showing boundary unevenness, FIGS. 7 and 8 are explanatory diagrams of an embodiment of the present invention, FIG. 7 is a perspective view of the platen, and FIG. 8 (A) is a side view. Side view showing the state before transfer, No. 8
Figure (B) is a 1111j plane view showing the state during transfer, Figure 8 (C) is an explanatory diagram showing the reaction force distribution from the platen side, Figure 9
The figure is a top view illustrating another embodiment of the present invention. 1...Thermal head 2...° heating resistor element group 3...Thermal transfer ink ribbon 4...Recording paper 9...Elastic member 9a...
・Protrusions Fig. 1 Fig. 2 Fig. 3 (A) Fig. 4 (B) Fig. 6 Fig. 7 0

Claims (1)

[Claims] In a thermal printer that performs recording via a thermal transfer ink ribbon using a group of heating resistor elements arranged in the recording width direction, the platen side is a flat platen, and an elastic member provided on the platen is attached to the platen so as to face the thermal head side. A thermal printer characterized in that a protruding portion is provided, and the end face of the protruding portion is a slope in which a reaction force from the protruding portion side changes continuously from one end to the other end with respect to the arrangement direction of the heating resistor elements. .