JPS60250968A - Thermal recording printer - Google Patents

Abstract

PURPOSE:To arrange so that satisfactory printing may be performed even on PPC paper by providing thermal head heating elements of such size as smaller than the minimum image dot and forming the minimum image dot consisting of printing pixels obtained by the drive of heating elements. CONSTITUTION:In a printer capable of thermal transfer to recording paper 45 such as PPC paper through an ink ribbon 46 consisting of a heat-melting ink layer 47 and a base 48, a thermal head 41 has two heating elements 42, 42 which take care of the formation of the minimum image dots. In this way, the same temperature distribution as in a low speed drive can be obtained by the mutual interference of heating elements even in a high speed drive. Accordingly, the ink image dot 49 of such size as proximate to the minimum image dot can be obtained. For this reason, even recording paper having unsatisfactory smoothness such as PPC paper can be printed without missing or flawed image dots, thus providing the same print quality as in low speed printing even when high speed printing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal transfer printer, and particularly to a printer using a heat-melting type thermal transfer recording method.

[Technical background of the invention and its problems]

Thermal transfer printers are in increasing demand mainly for office use, as they are low-noise, maintenance-free, and environmentally friendly printers that can print on plain paper. Thermal transfer recording method uses heat-melting ink, which is selectively heated by a thermal head to melt or soften the ink and attach it to recording paper for recording. There is also a sublimation thermal transfer recording method that uses sublimation ink to partially sublimate the ink and attach it to the recording paper (two layers). , the ink ribbon has excellent storage stability and has been put to practical use in word processor printers and general-purpose computer terminals.However, with the heat-melting type, the contact state between the ink on the ink ribbon and the recording paper is called ink transfer, that is, the dot Since this is the key to formation, in order to perform good printing, recording paper with few irregularities on the surface, that is, excellent smoothness, is required.On the other hand, PPC paper is commonly used in offices, etc. There is a strong desire to use these easily available papers as recording paper.However, PPC paper and other papers have poor surface smoothness, and thermal transfer printers using these papers often have missing dots due to poor ink adhesion. , chips occur, and good print quality cannot be obtained.

[Purpose of the invention]

This invention improves the drawbacks of the conventional device mentioned above.
An object of the present invention is to provide a thermal transfer printer that can use recording paper with poor smoothness such as PPC paper. Another object of the present invention is to provide a thermal transfer printer that can produce uniform image dots.

[Summary of the invention]

This invention overlaps an ink ribbon and a recording medium, drives a thermal head that contacts the back of the ink ribbon, selectively heats the ink on the ink ribbon, melts or softens the ink, and transfers the ink to the recording medium that is in contact with the ink. In a thermal transfer printer that performs recording by attaching ink, separating the ink ribbon and recording medium, and transferring the ink to the recording medium,
Using a thermal head provided with a heating element having a size smaller than a desired minimum pixel, the minimum pixel is made up of a plurality of ink pixels obtained by driving the heating element. In other words, by dividing and heating the ink area corresponding to the minimum image point, the ink is uniformly heated in the corresponding area to a temperature higher than the melting or softening temperature, thereby preventing the ink from adhering to the recording paper. By increasing the amount of dots or ink adhesion, it is possible to improve the print quality on recording paper with poor smoothness or to make the dots uniform.

〔Effect of the invention〕

According to this invention, it is possible to print neatly without missing or chipping dots even on recording paper with poor smoothness such as PPC paper.

In addition, it is possible to form uniform and sharp image dots, allowing for clear recording. Furthermore, even with high-speed printing, it is possible to obtain the same print quality as with low-speed printing.

[Embodiments of the invention]

Hereinafter, this invention will be explained in detail with reference to the drawings.

FIG. 1 shows the minimum pixel 1 /
It is a serial thermal transfer printer of 6 toxl/6vryi. ① is a thin film thermal head, in which a number of heat generating elements (not shown) are installed in a vertical line (212 Shiko/Tomo's element sound intensity). zu)Ini31/cr/
A black ink (not shown) was applied in a coating amount of 1. The thermal head 1 is provided facing the polyethylene terephthalate film of the ink ribbon 2.

3 is a recording paper (plain paper, also called PPC paper) whose ink-receiving surface has a Bekk smoothness of 100 seconds. 4 is a rotatable platen roller, and driving means (not shown) consisting of a step motor etc.
It is rotated accordingly. Further, the thermal head 1 and the cooperative sheet, the thermal head 11, the ink ribbons 2, 8, and the recording paper 3 are brought into pressure contact. 5 is an ink ribbon supply reel, 6 is an ink ribbon take-up reel, 7 is an ink ribbon guide bin,
8 is the thermal head 1. Ink ribbon 2. Ink ribbon supply reel5. Ink ribbon take-up series 6. This is a carriage on which an ink ribbon guide bin 7 is placed and can be moved in the axial direction of the platen roller 4. The carriage 8 is driven by a carriage driving means (not shown) and the thermal head 1
The movement is controlled in conjunction with the printing timing f2. FIG. 2 is an enlarged view of the heating element array portion of the thermal head 1. As shown in FIG.

2] is a heating element with a size of 65μ x 140μ and Ta
-8iO, made of cermet, and 24 elements are arranged in a row in a direction perpendicular to the direction of movement of the carriage 8 in FIG.
The other end is a thermal head drive circuit (two heating elements 21; two connected) that independently drives and controls 12 sets of heating elements.
It is connected to a power source (not shown) via a power source (not shown). The path is a return electrode, one end of which is connected to all of the shellfish 2J, and the other end is grounded. The signal type 1L return path electrode is composed of a gold thin film with a thickness of 3 μm. The casting is a glaze layer made of high-temperature glass, which improves the efficiency of supplying thermal energy generated by the heating element 21 to the ink ribbon (not shown). 5 is an alumina ceramic substrate.

As is clear from FIG. 2, the serial thermal transfer printer shown in FIG.
The test was carried out using two 140μ heating elements each weighing 1g.

Next, the operation of this printer will be explained. The thermal spatula ρ1 in the home position is separated from the di-ink lip 2 by thermal head pressure control means (not shown). In response to the start signal, the carriage 8 is moved in the direction of the arrow by a carriage drive means (not shown) controlled by a mechanism operation control circuit (not shown) to the printing start point. At the printing start point, the thermal head 1 is urged in the direction of the platen roller 4 by a thermal head pressure control means (not shown), and the thermal head 1 is pressed in the direction of the platen roller 4.

Ink ribbon 2. Recording paper 3. The platen rows 24 are overlapped and abutted one after another. Based on the print signal, the heating element (21 in FIG. 2) of the thermal head 1 is selectively energized by the action of a thermal head drive circuit (not shown). At this time, since two heating elements (21 in FIG. 2) are connected to one signal electrode (22 in FIG. 2), the two heating elements generate heat at the same time. The ink on the ink ribbon 2 in the heat generating portion is sufficiently softened or melted and adheres to the recording paper 3. The time for energizing the heating element at this time is Q, 8 ms. After energization, the carriage 8 moves 1/6 m, or about 1
65μ, moves in the direction of the arrow C2, stops, and energizes the heating element in the same manner as before. This operation is repeated until the end of the recording paper 3. At this time, as the carriage 8 moves, the ink ribbon 2 is fed out from the ink ribbon supply reel 5, printed, separated from the recording paper 3, and wound onto the ink ribbon take-up reel 6. When printing is completed at the end violet of the recording paper 3, the thermal head 1 is separated from the ink ribbon 2 by a thermal head pressure control means (not shown). Thereafter, the carriage 8 is moved by a carriage driving means (not shown) in the direction opposite to the arrow direction and returns to the home position or the printing start point. During this time,
The recording paper 3 is advanced by one line by the rotation of the platen roller 3, and a new printing surface faces the thermal head 1.

By repeating these operations, printing for one page is completed. The images printed by this printer were of good quality, with no missing or missing pixels, compared to the conventional apparatus.

For recording paper with poor smoothness of the ink-receiving surface such as PPC paper, or for high-speed printing, a printer that generates heat from multiple heating elements smaller in size than the smallest pixel to form the smallest pixel is effective. This is thought to be due to the following reasons.

FIG. 3 shows the temperature distribution on the surface of the heating element in one dimension when the heating element of the thermal head is driven. 31 is the substrate of the thermal head, 32 is the heating element of the conventional device corresponding one-to-one to the minimum image point (length L), 3
Reference numeral 3 designates heating elements of the printer according to the present invention, which correspond one-to-one in sets of two to the minimum pixel (length). Figure 3 (
Generally, when the heating element is driven at low speed (when the energization pulse width is long) as shown in Figure al., the temperature distribution on the surface of the heating element is approximately uniform over the entire surface (2
00-300°C) is obtained. However, when driven at high speed (current pulse width 1 ms or less), the central part of the heating element becomes high temperature (over 300°C) in order to generate enough thermal energy to melt or soften the ink.
This results in a temperature distribution with a sharp temperature gradient around the area. At this time, if the lower limit of the temperature on the heating element that can soften or melt the ink is the temperature indicated by the dashed line, the size and length l,) of the ink dots transferred to the recording paper will be the desired value. pixel (smaller than the minimum pixel).

However, if the minimum pixel formation is divided into two heating elements as shown in Fig. 3 (bl), f2 during high-speed driving will also change as shown by the solid line in Fig. 3 (b) due to mutual thermal interference of the heating elements. As shown in C21. Temperature distribution during low speed driving (dashed line),
A temperature distribution is obtained, and an ink dot size (length 4') which approximates the minimum dot (length L) is obtained. When considering this in addition to the unevenness of the surface of the recording paper that comes into contact with the ink, the superiority of thermal transfer printers becomes even clearer. FIG. 4 schematically shows the state in which the ink in the thermal transfer printer f2 is heated and melted or softened, and the state in which the ink is transferred to the recording paper after the ink ribbon and the recording paper are separated. Fourth
In the case of the printer according to the present invention, FIG.
1 is for the conventional device. Reference numeral 41 denotes a thermal head of a thermal transfer printer according to the present invention, which includes two heating elements 42.
to form the minimum pixel. Reference numeral 43 denotes a thermal head of a conventional device, which is equipped with heating element materials corresponding to the minimum pixel on a ratio of 1 to 1. 45 is a recording paper such as PPC paper, and 46 is an ink ribbon, which is placed between the heat-melting ink layer 47 and the substrate. 49 is ink transferred to the recording paper 45. As shown in FIG. 4(al), in the thermal transfer printer according to the present invention, the heating area (minimum image area) by the two heating elements 42 is the heating area of the heating element shown in FIG. The temperature is raised uniformly and to a temperature sufficient to soften or melt the ink, so that the ink becomes sufficiently softened or molten to adhere to the recording paper over the entire heated area (
(indicated by a tongue). On the other hand, in the case of the conventional apparatus as shown in FIG. 4 (bl), in the ink layer corresponding to the heating area of the heating element material, the temperature distribution in the heating area of the heating element is as shown in FIG. 3(a). Corresponding to this, there are areas that have softened or melted enough to adhere to the recording paper (indicated by the slit) and areas that have not yet softened or melted (indicated by the mouth).P
In thermal transfer printers that use recording paper with uneven ink-receiving surfaces, such as PC paper, the more points per unit area of contact between the softened or melted part of the ink and the convex parts of the recording paper, the larger the heating area (printing area). The ink is adhered to the recording paper faithfully to the area).

Therefore, as is clear from comparing the ink transferred to the recording paper in FIGS. 4(a) and 4(b), the thermal transfer printer according to the present invention prints better than the conventional device. The higher the reproducibility of the transfer ink in the target area, the better printing can be performed.

In addition, the shape of the thermal head is not limited to the serial moving head mentioned in the example, but may also be a line head with two lines of heating elements arranged, or a thermal head with heating elements arranged in a strix arrangement. Of course, similar effects can be obtained if the relationship between the image dots and the heating elements of the thermal head is within the scope of the claims of the present invention. The printers to which this invention is applied are not limited to the serial printers of the embodiments, but are also applicable to line printers using line heads.

In addition to monotone printers, color thermal transfer printers using color ink ribbons, such as JP-A-58
It is also applicable to the printer shown in No.-82768.

In color thermal transfer printers, colors are expressed by mixing or overlapping predetermined amounts of two or three different color inks, so securing a predetermined amount of ink is more important than monotone recording. Therefore, the color thermal transfer printer to which the present invention is applied can produce much better color images than conventional devices.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a serial thermal transfer printer which is an embodiment of the present invention, Figure 2 is an explanatory diagram of the shape of a heating element of a thermal head of a serial thermal transfer printer which is an embodiment of the present invention, and Figure 3M is a conventional diagram. FIG. 4 is a diagram illustrating the effect of the thermal head of the apparatus of the present invention in comparison with the thermal head of the apparatus, and FIG. 4 shows the effect of ink transfer on uneven recording paper in comparison with the conventional apparatus. It is a figure for explaining. 1... Thermal head 2... Ink ribbon 3...
・Recording paper 4...Platen roller 21...Heating element 22...Signal electrode...Return electrode Patent attorney Kensuke Norichika (and one other person)

Claims (1)

[Claims] (1) In a thermal recording printer that selects and heats a heat-sensitive recording medium to record by driving a thermal head in contact with an ink ribbon, the size of the heating element of the thermal head is adjusted to the desired minimum dot. A thermal recording printer characterized in that the minimum image point is formed by a plurality of printing pixels obtained by driving a heating element.