JP2001232830A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer which can print high printing quality images by pressing a thermal head into contact with a platen when executing printing and, unifying a press contact pressure applied to recording papers. SOLUTION: A press contact face 2a of the platen 2 is shaped to curve so that parts where both end parts in an arrangement direction of a plurality of heating elements 9a of the thermal head 9 are positioned are higher than a part where the vicinity of a central part in the arrangement direction of the heating elements 9a is positioned. The press contact pressure applied to the recording paper 1 being printed and to an ink ribbon 11 in the arrangement direction of the heating elements 9a formed to the thermal head 9 can be unified without variations, and therefore high printing quality images without a density irregularity can be printed to the recording paper 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer capable of printing by pressing a thermal head against a platen.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional thermal printer can move toward and away from a platen 21 and can reciprocate in a longitudinal direction of the platen 21 (a direction in which the platen 21 stands upright). Thermal head 23 is disposed. The platen 21 is made of an elastic material such as rubber, and has a flat press contact surface 21a formed on the surface thereof, and is fixed to the metal plate 22 with an adhesive (not shown). Also,
The thermal head 23 has a plurality of heating elements 23a arranged in a line.

The printing operation of such a conventional thermal printer will be described with reference to a thermal transfer printer. First, the printing paper is separated from the platen 21 and a recording paper (not shown) is placed between the thermal head 23 and the platen 21 in a head-up state.
And an ink ribbon (not shown) is positioned between the recording paper and the thermal head 23. Next, the thermal head 22 is moved toward the platen 21 to press the recording paper and the ink ribbon against the platen 21. By moving the plurality of heating elements 22a along the longitudinal direction of the platen 21 while selectively generating heat according to the print information, one line or a plurality of lines of images are printed on the recording paper.

After printing one or more lines of images on the recording paper, the thermal head 23 is moved up, the recording paper is transported in the transport direction to perform a line feed operation, and the printing operation is repeated. A desired image can be printed on one recording sheet. Such a thermal printer has been attracting attention in recent years as an environmentally friendly printer that can print high-quality images even if the recording paper is recycled paper.

[0005]

However, in the conventional thermal printer as described above, when the thermal head 21 is pressed against the platen and a pressing load W is applied to the thermal head 23 as shown in FIG. Platen 2 consisting of
1 is compressed and elastically deformed, and both right and left ends of the platen 21 expand outward in the direction of arrow A and escape. For this reason, the platen 21 has a repulsive force B at a portion where both ends in the column direction of the heating element 23a formed on the thermal head 23 are located, and a repulsive force B at a portion near the center portion of the heating element 23a in the column direction. It becomes smaller than C.

That is, the pressing force applied to the recording paper pressed against the thermal head 23 and the ink ribbon is generated by the heating element 23.
a of the heating element 23a
There is a possibility that the portion where both end portions are located becomes smaller, the image printed by transferring the ink of the ink ribbon to the recording paper becomes dark and light, and the print quality deteriorates. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and can print a high-print-quality image by pressing a thermal head against a platen during printing to make the pressing pressure applied to recording paper uniform. It is an object to provide a thermal printer.

[0007]

As a first means for solving the above problems, a thermal printer according to the present invention comprises:
A thermal head in which a plurality of heating elements are arranged in a line, and a platen against which the thermal head can be pressed, the thermal head of the platen has a press-contact surface that can be pressed, and the shape of the press-contact surface is The thermal head has a configuration in which a portion where both ends in the arrangement direction are located is formed in a high curved shape with respect to a portion where a plurality of heating elements are located near the center in the arrangement direction.

As a second means for solving the above-mentioned problems, the platen may have a dimensional difference of 0.1 mm between a portion where the thermal head is located near the center and a portion where both ends are located. Configuration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal printer according to the present invention will be described below with reference to a thermal transfer printer. First, a thermal printer according to the present invention is provided with a printing means P as shown in FIG. At P, a recording sheet 1 conveyed from a sheet feeding unit (not shown) below the drawing is positioned. The printing means P has a platen 2 made of neoprene rubber or the like and having a hardness of 80 ° to 90 °.
Are arranged. The platen 2 is horizontally long in the drawing and longer than the width of the recording paper 1. The platen 2 is attached to a metal plate 3 having a predetermined thickness with an adhesive or the like to be integrated.

The platen 2 has on its surface a pressure contact surface 2a on which a thermal head 9 to be described later can be pressed. The pressure contact surface 2a has a cross-sectional shape in the vertical direction in the drawing orthogonal to the longitudinal direction of the platen 2, as shown in FIG. As shown in (1), a central portion is formed in a curved shape with a low portion at both ends. And the press contact surface 2a
Means that the dimensional difference G in the height direction between the center and both ends is 0.1 m
m.

A plurality of rotatable paper feed rollers 4 made of rubber or the like are attached to the rotating shaft 4a at predetermined intervals below the platen 2 in the drawing. A rotatable pressure roller 5 is independently pressed against the plurality of paper feed rollers 4, and when the paper feed roller 4 rotates, the pressure roller 5 follows. Then, by the feed roller 4 and the pressing roller 5,
The recording paper 1 conveyed from a paper feeding unit (not shown) below the drawing is pressed and held, and the recording paper 1 is conveyed in the direction of arrow E and can be conveyed to the platen 2 side.

On the side facing the platen 2, there is provided a carriage 6 which can reciprocate along the longitudinal direction of the horizontally long platen 2. The carriage 6 is supported by a rod-shaped guide shaft 7 and has an appropriate drive belt 8 wound around a pair of drive pulleys (not shown). The carriage 6 is reciprocated along the platen 2 by rotating the drive pulley. A flat cassette mounting surface 6a is formed on the upper surface of the carriage 6, and near the center of the cassette mounting surface 6a, a pair of rotatable bobbins 6b, 6b are spaced apart from each other by a predetermined distance. The protrusion is formed.

On the side of the carriage 6 which faces the platen 2, a thermal head 9 which can be pressed against the platen is mounted. The thermal head 9 has a plurality of heating elements 9a arranged in a line in the vertical direction in the figure near the right end shown in FIG. The plurality of heating elements 9a can selectively generate heat based on print information from a control unit (not shown).

The thermal head 9 can be moved toward and away from the platen 2 in conjunction with rotation of a rotatable cam member (not shown). When the thermal head 9 comes into contact with and separates from the platen 2, the thermal head 9 can be pressed against the platen 2. A ribbon cassette 10 can be mounted on a cassette mounting surface 6a of the carriage 6. The ribbon cassette 10 has a pair of hole-shaped reels 10a with which a pair of bobbins 6b, 6b of the carriage 6 can be engaged. An ink ribbon 11 having a predetermined color of heat-meltable ink applied thereon is wound around the pair of reels 10a and 10a.

In such a printing means P, the left and right ends of the platen 2, the paper feed roller 4, the pressing roller 5, the guide shaft 7, and the like are attached to a pair of frames (not shown), respectively. A thermal printer is configured. Then, the printing operation by the thermal printer of the present invention will be described. First, the uppermost recording sheet 1 stored in the sheet feeding unit (not shown) is sent to the printing unit P by a sheet feeding roller (not shown). Transport. Then, the recording paper 1 is conveyed between the thermal head 9 and the platen 2 in the head-up state by rotating the paper feed roller 4 by pressing the front end of the recording paper 1 between the paper feed roller 4 and the pressure roller 5. Is done.

Next, the thermal head 9 is lowered, and a pressure load W is applied to the thermal head 9 as shown in FIG.
To press the ink ribbon 11 and the recording paper 1 against the platen 2. The pressure contact load W is set to approximately 2 kg. For this reason, the elastic platen 2 made of neoprene rubber or the like compresses and elastically deforms a portion pressed against the thermal head 9, and as shown in FIG. .

However, the platen 2 has a thermal head 9
The portion where both ends in the arrangement direction of the heating elements 9a are formed in a high curved shape with respect to the portion where the vicinity of the central portion in the arrangement direction of the plurality of heating elements 9a is formed. Even if the both ends of the platen 2 in the cut-off portion escape in the outward direction of the arrow H, the repulsive force J of the platen 2 applied to the thermal head 9 is reduced by the central portion of the heating element 9a
And both ends can be equalized.

Next, while the thermal head 9 is pressed against the platen 2, the heating element 9 a is selectively heated based on the print information, and the carriage 6 is moved along the longitudinal direction of the platen 2. The ink of the ink ribbon 11 is thermally transferred to the recording paper 1 and, for example, one line,
Alternatively, a plurality of lines of images are printed. After the printing of one or more lines, the thermal head 9 is moved up to return the carriage 6 to the initial position, and the paper feed roller 4 is rotated to perform a line feed operation.
The desired image can be printed on the printer.

The thermal printer according to the present invention has the following features.
During printing, the repulsive force J of the platen 2 applied to the thermal head 9 pressed against the platen 2 can be made uniform at both the center and both ends of the heating element 9a. Therefore, it is possible to make the pressure applied to the heating element 9a formed on the thermal head 9 in the row direction applied to the recording paper 1 and the ink ribbon 11 during printing uniform without variation.
In the description of the embodiment of the present invention, a thermal transfer printer has been described. However, the present invention may be applied to a thermal printer that uses thermal paper without using an ink ribbon.

[0020]

As described above, in the thermal printer according to the present invention, the shape of the press contact surface of the platen is adjusted with respect to the portion of the thermal head near the center in the arrangement direction of the plurality of heating elements. Since the portions where both ends in the direction are formed in a high curved shape, the pressure contact pressure applied to the recording paper during printing and the ink ribbon in the row direction of the heating elements can be made uniform without variation. It is possible to print an image of high print quality without shading on recording paper. Also, by making the pressure contact surface curved, the pressure contact load of the thermal head can be further increased, and a high-quality image can be printed on recycled paper having a low surface smoothness. Can provide a more environmentally friendly printer.

Further, the platen has a dimensional difference of less than 0.1 mm between the portion where the center portion is located near the center portion and the portions where both ends are located, so that the repulsive force of the platen applied to the thermal head is reduced. , Both the center and both ends of the heating element can be made uniform.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a printing unit according to the present invention.

FIG. 2 is a diagram of a platen and a thermal head according to the present invention.

FIG. 3 is a view in which a thermal head is pressed against a platen according to the present invention.

FIG. 4 is a diagram of a platen and a thermal head of a conventional thermal printer.

FIG. 5 is a diagram in which a thermal head is pressed against a platen of a conventional thermal printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording paper 2 Platen 2a Printing surface 3 Metal plate 4 Paper feed roller 4a Rotating shaft 5 Pressure contact roller 6 Carriage 6a Cassette mounting surface 6b Bobbin 7 Guide shaft 8 Drive belt 9 Thermal head 10 Ribbon cassette 10a Reel 11 Ink ribbon

Claims (2)

[Claims] 1. A thermal head in which a plurality of heating elements are arranged in a line, and a platen to which the thermal head can be pressed. The thermal head of the platen has a press-contact surface which can be pressed. The thermal head is characterized in that a portion where both ends in the arranging direction are located is formed in a high curved shape with respect to a portion near a central portion in the arranging direction of the plurality of heating elements of the thermal head. Printer. 2. The thermal head according to claim 1, wherein the platen has a dimensional difference between a portion where the central portion is located near the center and a portion where the both ends are located within 0.1 mm. Printer.