JPS63154374A - Device for image formation - Google Patents

Abstract

PURPOSE:To eliminate the need for reciprocating a medium forward and backward, enhance printing speed and prevent color misregistering, by using three line thermal heads for Y, M and C colors in the state of facing one platen while using a single line thermal head for BL color in the state of facing the other platen. CONSTITUTION:At the time of printing, a medium is fed out from a paper- supplying part 35 by a pick roller 36, and is supplied between a platen 331 and a ribbon 31Y, where printing in Y color is conducted by a line thermal head 32Y. Subsequently, the medium is sequentially fed between the platen 331 and a ribbon 31M and between the platen 331 and a ribbon 31C by rotating the platen 311, and printing in M color and printing in C color are sequentially conducted, similarly to the above. Then, the medium is fed between a platen 332 and a ribbon 31BL, where printing in BL tone is conducted. After printing on the medium is completed, the medium is discharged to a discharging part 38 by a discharging roller 37. Thus, printing in each of the colors is conducted without reciprocating the medium, so that printing speed is enhanced, and color misregistering can be prevented.

Description

[Detailed Description of the Invention] [Summary] The present invention prevents color misregistration during overlapping printing of each color of Y (yellow), 9M (magenta), and C (cyan) in a thermal transfer image forming apparatus, and achieves high-speed printing. Y, M, C, BL (black)
This objective is achieved by arranging four line thermal heads and two platens in combination.

[Industrial application field]

The present invention relates to a thermal transfer image forming apparatus using a line thermal head.

The thermal transfer type full color image forming apparatus is Y, M.

Overlapping printing is performed using four line thermal heads corresponding to each color of C and BL, but in order to improve printing quality, it is necessary to prevent color shift during overlapping printing. is necessary.

[Conventional technology]

The structures of various thermal transfer type full-color image forming apparatuses using conventional line thermal heads are shown in FIGS. 2 to 5.

The apparatus shown in FIG. 2 uses a thermal transfer ribbon 1 whose details are shown in FIG. 3, in which 2 is a line thermal head and 3 is a platen. Line thermal head 2 is platen 3
Correspondingly, the ribbon 1 fed out from the cassette 4 passes between these. Ribbon L has Y,
M, C, and BL color ink layers are provided alternately. When printing, the medium is transferred from the paper feed section 5 to the pink roller 6.
The medium is fed out between the platen 3 and the ribbon 1, and printing on the medium is performed by positioning the desired color portion of the ribbon 1 on the platen, and pressing the line thermal head 2 against the platen 3 to generate a predetermined heat. This is done by applying electricity to the body. In this case, the ink on the ribbon facing the energized heating element is melted and transferred to the medium. The medium on which predetermined printing has been completed is discharged to a discharge section 8 by a discharge roller 7.

The device shown in Figure 4 is equipped with separate ribbons, line thermal heads, and platens for each color.
v, 1 lx, 11c are ribbons of Y, M, and C colors, 12Y, 12. ．． 12e and 13y, 1314
．． 13c is a line thermal head and platen corresponding to each color of Y, M, and C, and 14 is a paper guide.

In this case, printing on the medium 100 that is fed in the direction of the arrow is sequentially performed at different locations for each color, thereby realizing three-color overlapping printing.

The apparatus shown in FIG. 5 uses a belt 21 instead of the three platens for each color layer shown in FIG. 4, 22Y, 22. t,
22e is each line thermal printer 12v, 1
2.4. This is a facing roller facing 12c.

[Problem that the invention seeks to solve]

The drawbacks of these conventional image forming apparatuses are as follows.

In the case of the device shown in Figure 2, the printing speed is slow because it is equipped with only one head, and the colors are matched by overlapping printing using a stepped ribbon as shown in Figure 3, so it is difficult to print media by color. The media had to be moved back and forth (back and forth) on the platen, and paper misalignment (overlapping printing misalignment, ie, color misalignment) occurred due to the feeding accuracy of the medium.

In addition, in the case of the device shown in Fig. 4, Y, in one pass of the medium,
It performs overlapping printing of three colors, M and C, and there is no need to move the medium back and forth for each color, but color shift occurs due to feeding errors due to variations in the diameter of each platen. To explain this specifically, for example, if the diameter of the platen 137 is 0.05 mm larger than the diameter of the platen 13M, the platen diameter 301. Platen 13. , 134, the platen 13v rotates 0.8 times to send the medium to the platen 138, which is 0.13 mm more than the feed amount of the platen 1314. This deviation causes blurring of the printed color and the printed result becomes unclear.

To solve this, either use platens selectively or
Alternatively, it is conceivable to control the feed amount independently for each platen, but either method would be expensive and not a good idea.

Furthermore, in the case of the apparatus shown in FIG. 5, since the belt 21 is used to feed the paper, the amount of paper feed directly below each head is always constant, and the color misregistration in the case of FIG. 4 can be prevented. In this case, it is desirable that the belt 21 has a soft surface with little expansion and contraction.

However, like the device shown in FIG. 4, the device shown in FIG. 5 is horizontally long and requires a large installation space.

[Means for solving problems]

The present invention provides an image forming apparatus that can solve the above-mentioned problems, and as a means for that purpose, the present invention presses a line thermal head against a platen through a ribbon, a medium, and presses the line thermal head against the medium. In a thermal transfer image forming apparatus that forms an image, the ribbon is Y (yellow) 1M.
(magenta).

C (cyan) and BL (black) are provided independently for each color, four line thermal heads are provided corresponding to each color ribbon, two platens are provided, and the line thermal heads for Y, M, and C colors are provided. The ribbon and the line thermal head are made to face one of the platens, and the BL color ribbon and the line thermal head are made to face the other platen.

[Effect]

Three line thermal heads for Y, M, and C colors are used to face one platen, and one line thermal head for BL color is used to face the other platen. Since there is no need to reciprocate back and forth, printing speed can be improved and color shift can be prevented.

〔Example〕

The invention will now be described in detail with reference to FIG.

FIG. 1 is a side view showing the structure of the image forming apparatus according to the present invention, and 31v, 31M, 31C, 311L are Y, M, C,
Ribbon provided independently for each BL color, 32v, 32
M, 32C, and 321L are line thermal heads corresponding to each of these color ribbons, 33. ．． 33□ is a platen.

The ribbons 31y, 3114.31c', and 311L are stored in cassettes 34Y, 34M, 34C, and 34*t, respectively, so that they can be fed out.

Y, M: c cassettes for each color 34Y, 34. .

34C, 3411L and line thermal head 32°,
32g, 32C, and 3211L are the platen 33. BL color cassette 34B facing the outer periphery of
L and line thermal head 32at are platen 33g
facing the outer periphery of

When printing, the medium is transferred from the paper feed section 35 to the pick roller 3.
6 and the platen 33. and the ribbon 31Y, where Y color printing is performed by the line thermal head 32y. Similarly, the medium is platen 3.
1. By rotating the platen 331 and each ribbon 31,
4 and 31c, and printing in M and C colors is performed. Thereafter, the medium is sent between the platen 33□ and the ribbon 31, where BL toning printing is performed. The medium on which printing of all colors has been completed in this way is carried out by the ejection roller 37.
is discharged to the discharge section 38.

In this manner, in the present invention, each color is printed without reciprocating the medium, so the printing speed is improved. In addition, since Y, M, and C colors are overlapped on one platen, Y,
It is possible to prevent color misregistration by eliminating misalignment of the medium with respect to the platen when printing in M and C colors. This is because it is possible to eliminate the influence of variations in the diameter of each platen, which is a problem in the case of conventional apparatuses in which Y, M, and C colors are overlapped using a plurality of platens. Furthermore, since there are only two platens in total, the apparatus can be made more compact.

When performing monochrome printing (BL color printing) with this device, 1 head + 1 platen (line thermal head 32)
1L and platen 33t), and in that case, the conveyance path is switched so that the medium is fed directly from the paper feed section 35 to the platen 33□ without passing through the platen 33°.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve printing speed, prevent color shift, and make the apparatus more compact. It is also possible to perform monochrome printing.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the structure of an image forming apparatus according to an embodiment of the present invention, Figs. 2.4.5 are side views showing the structure of various conventional thermal transfer type image forming apparatuses, and Fig. 3 is Fig. 2. This is a plan view of the thermal transfer ribbon used in the device. In the figure, 31v, 31M, and 31C23111L are ribbons. 32Y, 32M, 32c, 32BL are line thermal heads, 33, . 33□ is the platen, 34v, 3414, 34C, 3411L are the cassettes, 3
5 is a paper feed section, and 38 is a discharge section.

Claims (1)

[Scope of Claims] A thermal transfer type image forming apparatus that presses a line thermal head against a platen through a ribbon and a medium to form an image on the medium, wherein the ribbon is Y (yellow), M (magenta), C (
cyan) and BL (black), and four of the thermal heads are provided corresponding to each color ribbon, and two of the platens are provided, and the ribbons of Y, M, and C colors and the An image forming apparatus characterized in that a line thermal head is opposed to one of the platens, and the BL color ribbon and the line thermal head are opposed to the other platen.