JPH10278332A - Thermal transfer printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer printer realizing high quality recording while sustaining high throughput by eliminating a tint streak occurring on a recording sheet at the overlap printing part or the periphery thereof due to line feed when a large line feed is set in order to enhance the printing speed of one recording sheet (throughput) at the time of recording through a thermal transfer printer. SOLUTION: Line feed is carried out such that the print region of a recording head has a partially overlapped printing part 1 and the recording density is controlled by setting the power being thrown into a heating element located at the overlapped printing part 1 lower than a reference level whereas setting the power being thrown into a heating element located adjacent 2 to the overlapped printing part 1 higher than the reference level at the time of printing each line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer, and more particularly, to a thermal transfer printer which performs recording by correcting the recording density of the upper and lower ends of each print line and the adjacent area.

[0002]

2. Description of the Related Art A conventional thermal transfer printer will be described.

First, a brief description will be given of a conventional thermal transfer printer.
Recording on recording paper using an ink ribbon coated with hot-melt ink (hot-melt ink ribbon), and recording paper using ink ribbon coated with sublimable ink (heat-sublimable ink ribbon) Some records are recorded.

Among these, a thermal transfer printer that performs recording on recording paper using a heat-fusible ink ribbon (hereinafter, referred to as a hot-melt thermal transfer printer) records on a wide variety of recording paper such as plain paper, cardboard, and postcards. It is easy to use.

On the other hand, a thermal transfer printer that performs recording on a recording medium using a thermal sublimation ink ribbon (hereinafter, referred to as a thermal sublimation thermal transfer printer) uses silver-lead as a recording medium using surface-treated special paper. A high-quality recorded image comparable to a photograph can be obtained.

[0006] In the method of performing recording using these conventional thermal transfer printers, a carriage on which a recording head having a plurality of heating elements arranged in an array is reciprocated along a platen, and between the platen and the recording head. The desired recording is performed by selectively heating the heating element while holding the recording paper and the ink ribbon. At this time, generally, it is assumed that each heating element of the recording head generates heat at the same surface temperature.
Recording control was being performed.

[0007]

However, when a recording head having 160 heating elements (also referred to as the number of dots) is taken as an example, in practice, as shown in FIG. The temperature has dropped.

The reason why the surface temperature decreases near both ends of the heating element row is as follows. In other words, other heating elements are arranged on both sides in the vicinity of the center of the heating element row, and are not easily affected by low temperatures in the peripheral part.
The surface temperature of the heating element arranged at the end of the heating element row is reduced because there is no other heating element on the end side. When the surface temperature of the heating element at the extreme end decreases, the heating element adjacent to the heating element is also affected, the surface temperature decreases, and the adjacent heating element is further affected.

When recording is performed in this state, FIG.
As shown in (1), the recording density decreases at both ends of the heating element array of the recording head and in the vicinity thereof. As a result, when line feed printing is performed using the recording head, the recording density is reduced in the line feed portion as shown in FIG. 6, and the print quality is degraded.

As described above, conventionally, line feed printing has been performed so as not to produce overlapping portions of printing and without any gaps. However, in recent years, as image printing has become higher definition, in addition to the above-described problem of reduced recording density, a slight gap generated in a line feed portion has become conspicuous. This is because such a gap was conventionally overlooked due to the coarseness of the image, but a small gap is clearly recognized as a white streak in a high-resolution printed image.

As a countermeasure, mechanical precision of a paper feed mechanism of a printer has been improved, but it is difficult due to cost. Therefore, in order to absorb variations in mechanical accuracy and stabilize print quality,
It is an indispensable condition that a line break is provided by providing an overlapping portion of printing.

Therefore, the applicant first records a new line by an amount corresponding to an effective recording area where the recording density shown in FIG. 5 is constant, and performs recording so that the density correction areas before and after the new line overlap. Then, a proposal was made to adjust the recording density in the density correction area to eliminate the recording density decrease caused by line feed (Japanese Patent Application No. 8-155467).

With the above situation as a background, the results of preliminary studies leading to the present invention will be described below.

Recently, in a thermal transfer printer, recording paper 1
There is a demand for increasing the speed of printing sheets, that is, increasing the throughput. For that purpose, it is important to minimize the overlapping portion of printing in the above-described line feed and increase the line feed amount.

Therefore, line feed printing was attempted with the amount of power applied to each heating element of the recording head being fixed and the overlapping portion of printing being reduced. As a result, as shown in FIG. 7, the recording density was high in the overprinting section 1, and the recording density was low in the adjacent section 2 adjacent to the overprinting section 1.

FIG. 8 is an explanatory diagram when the recording density on the recording paper is represented by a relative numerical value in such a state. In particular, attention is paid to the density difference between the density correction areas composed of the overprinted portion 1 and the adjacent portion 2, and the larger the numerical value, the higher the recording density. Note that the heating element row 3
Although the number of heating elements (the number of dots) is actually about 50 to 300, the drawing is simplified.

Here, “f” described in the heating element row 3
Represents the amount of power applied to one heating element of the recording head, and is an example when the amount of power applied to each heating element is constant and all are “f”. In addition, 55 μJ can be cited as a specific example of the input power amount.

The density correction area in the example shown in FIG. 8 corresponds to the above-described density correction area in FIG. In this density correction area, the recording density in the overprinting section 1 is “8”, the recording density in the adjacent section 2 is “4”,
Black streaks were formed in the center, and white streaks were formed adjacent to both sides, deteriorating the printing quality.

The cause will be described with reference to FIG. That is, the end of the heating element, ie, the first and 160
The second print dot has the lowest recording density as compared with the other dots. However, since these are arranged so as to be overlapped by a line feed, the recording density in the overprinting section 1 is increased. On the other hand, the adjacent portions 2 have low recording density and do not overlap due to line feed, so that the recording density remains low. Due to such a cause, the above-described problem that a density stripe occurs in the density correction area occurs.

This state is more conspicuous when the temperature difference between the ambient temperature of the print head and the heat generation temperature of the heating element is large, for example, at the start of printing or when the ink ribbon is replaced. Further, in the thermal sublimation type thermal transfer printer, the amount of ink diffused into the recording paper is adjusted according to the temperature of the heating element, so that the decrease in the surface temperature of the heating element appears more sensitively in the recording density.

The present invention has been made in view of such a problem, and by adjusting the recording densities of the overprint portion 1 and the adjacent portion 2 in the density correction region, the density of the recording density in the density correction region is adjusted. It is an object of the present invention to provide a thermal transfer printer capable of performing high-quality recording at a high throughput by eliminating a streak.

[0022]

According to a first aspect of the present invention, there is provided a thermal transfer printer having an overprinting portion in which printing areas of a recording head partially overlap in printing of each line. In the density correction area composed of the overprinted portion and the adjacent portion, the heating elements located in the overprinted portion receive a smaller amount of power than a reference input power amount, and The point is that a power amount equal to or greater than the reference power amount is supplied to the located heating element.

By employing such recording density processing, high-quality recording can be realized by preventing the density stripes in the density correction region from being shaded.

According to a second aspect of the present invention, there is provided a thermal transfer printer according to the first aspect, wherein the input power amount corresponding to the gradation of the reference recording density is set for each of the heating elements located in the overlapping printing section and the adjacent section. The point is that it is set in advance and the set input power amount is input to each of the heating elements.

By adopting such a recording method, high-quality recording can be realized without affecting the recording speed, preventing the density stripes in the density correction area from being affected.

A feature of the thermal transfer printer according to the present invention is that a line feed is performed so that a print area of the recording head has an overlapped print portion that partially overlaps, and the thermal transfer printer includes the overlapped print portion and an adjacent portion thereof. In the density correction area, dots having higher and lower recording densities than the reference recording density are scattered.

By adopting such a recording method, finer density adjustment is possible, and a high-quality recording can be realized by preventing the density stripes in the density correction area from being shaded.

A thermal transfer printer according to a fourth aspect is characterized in that, in the first, second, or third aspect, the overlap printing portion is equivalent to one dot.

By adopting such a recording method, the amount of line feed can be maximized, and the print throughput can be increased while preventing the density streaks of the recording density in the density correction area to achieve high quality. Can be recorded.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a thermal transfer printer according to the present invention will be described below with reference to FIGS.

FIG. 1 is a view for explaining the relationship between the heating element array and the recording density according to an embodiment of the present invention. As shown in this figure, the amount of electric power supplied to the heating element of the recording head is corrected with the overlapped printing section 1 at the line feed being one dot. That is, a small amount of electric power is supplied to the endmost heating element of the heating element array 3, and a correction to increase the supplied electric power is performed in the adjacent part 2.

In other words, if there is no decrease in the surface temperature near both ends of the heating element array 3, the density correction area has a reference recording density that should be originally obtained, and is necessary to obtain this reference recording density. What is necessary is just to input a reference input electric energy. However, actually, since the surface temperature is reduced, the reference input power amount is corrected.

In the case of FIG. 1, the recording density of the print image is uniformly set to "5" for simplicity, so that the reference recording density is also "5". The input power amount required to obtain the reference recording density “5” at the center of the heating element row where the surface temperature does not decrease, that is, the reference input power amount is “f” (for example, 55 μJ).

Next, the reference recording density "5" is set in the density correction area.
In order to obtain the electric power “d” (for example, 45 μm) at the end of the heating element row 3 of the heating element row 3 located in the overprinting section 1.
Reduce the input power to J). On the other hand, in the heating elements of the heating element row 3 located in the adjacent part 2, the electric energy “g” (for example,
Increase the input power to 60 μJ). That is, the magnitude relationship of the input power amounts is d <f <g. As a result, the recording densities of the superimposed printing portion 1 and the adjacent portion 2 were uniformly "5", which coincided with the reference recording densities, and the density streaks of the recording densities generated in the density correction area were eliminated.

Next, another embodiment of the present invention will be described. That is, in the input power correction, the input power corresponding to the reference recording density is set in advance for each heating element located in the overprinting section 1 and the adjacent section 2, and the set power is set to This is to be supplied to the heating element. This enables the above-described density processing to be performed at high speed, and uses a conversion table referred to as an “input power amount conversion table” described below.

For example, when the recording density is 16 gradations, an example of the input power amount conversion table corresponding to this is shown in Table 1 below.

[0037]

[Table 1]

The meaning of this table will be described below. First, since the recording density is 16 gradations, the “reference recording density” in the density correction area also has 16 levels from 0 to 15. Next, as shown in Table 1, the input power amount required to obtain this reference concentration at the center of the heating element row 3, that is, the "reference input power amount" is determined in 16 stages of a, b, ..., p. (A <b <
... <p).

Next, in order to prevent the occurrence of light and shade stripes in the density correction area, the heating element row 3
It is necessary to determine in advance the amount of electric power to be supplied to the heat generating element at the end portion and the heat generating element located in the adjacent portion 2. This amount of power is shown in Table 1 as “input power amount for overlapping printing section” and “input power amount for adjacent portion”.

A specific example using this table will be described with reference to the case of FIG. 1 described above. In this case, printing is performed with a recording density of "5" over the entire recording paper. Therefore, the reference recording density in the density correction area is "5". , And the column “5” of the “reference recording density” in Table 1 (indicated by an asterisk at the top of the margin of Table 1). Then, it is immediately understood that the “reference input power amount” should be “f”, the “adjacent portion input power amount” should be “g”, and the “overprinting unit input power amount” should be “d”. In this manner, the amount of power input to the heating element array 3 in FIG. 1 is determined.

When the reference recording density is low (from 0 to about 2), the decrease in surface temperature near both ends of the heating element array 3 is negligibly small. It is not necessary to lower the power input to be lower than the reference power input, and the power input may be the same as the reference power input.

The "input power amount conversion table"
Are stored in the memory of the thermal transfer printer in advance. In the thermal transfer printer, the table is referred to by electric processing to determine the amount of electric power to be supplied to the heating element, and the recording density is appropriately adjusted. Although this recording density processing can be performed by sequential calculation, the method using the input power conversion table of the present invention is simpler and requires no calculation time, so that the recording density processing can be performed at high speed.

Next, a third embodiment of the present invention will be described. In other words, the recording density in the density correction area is not actually uniform, and for example, as shown in FIG. That is, the recording density of the overprinted portion 1 was "5.2" and the recording density of the adjacent portion 2 was "5.3", and a slight streak pattern was observed in the density correction area. This is considered to be caused by variations in the types and manufacturing of the recording paper, the ink ribbon, the recording head, and the like, and environmental factors such as temperature and humidity during printing.

FIG. 3 is an explanatory diagram of an embodiment of the present invention in consideration of such a situation. In the present embodiment, by changing periodically the amount of power supplied to each heating element located in the overprinting section 1 and the adjacent section 2, dots having higher and lower recording densities than the reference recording density in the density correction area are obtained. Are scattered, and when viewed in a relatively wide range, the recording density is made uniform on average, and the average recording density is made to coincide with the reference recording density, so that the density streaks in the density correction area are reduced. It will be resolved.

In this example, as shown in the n-th row, a power amount pattern (for example, dfgf
ffggc) are three types, i, b, and c.
In the printing of the A-th column, the input power amount pattern is A, the B-th column is B, and the C-th column is C. This three-column printing is one unit, and then the D-column is printed periodically and repeatedly, such as a, E-row, and F-column C. The other rows were printed in the same manner, and the recording density of the density correction area as shown in “Recording density on recording paper” was obtained. That is,
The overprinting section 1 repeats the recording density “4.6, 5.2, 5.2”, and the adjacent section 2 has the recording density “5.3, 4.4, 5,.
3 "etc. Therefore, in this case, when the density correction area is viewed in a relatively wide range of three or more rows on the recording paper, the average density is "5", which matches the reference recording density, and the streak pattern in the density correction area is eliminated. Was.

In the above example, the periodic repetition interval is set to three rows, but by further increasing the interval, finer density adjustment becomes possible.

Further, in this embodiment, the recording density is periodically changed. However, the recording density is changed randomly so that the high density part and the low density part are scattered so that the average density becomes the reference recording density. You can do it.

Further, in the embodiment described above, the overlap printing section 1 is set for one dot, but this may be set to an appropriate amount of two dots or more.

[0049]

As described above, in the thermal transfer printer according to the present invention, the amount of power applied to the heating elements when printing each line is changed by the reference amount of power applied to the heating elements located in the overprinting section 1. The recording element is subjected to recording density processing by supplying less heating power than the reference power supply amount to the heating elements located in the adjacent portion 2, thereby lowering the surface temperature near both ends of the heating element array 3 of the print head. As a result, it is possible to improve the adverse effect such as a decrease in the recording density that occurs as a result, eliminate the density streaks that have occurred in the density correction area of each recording row, and achieve higher quality recording.

Further, in the density processing, the input power amount corresponding to the reference recording density is set in advance for each heating element and stored in a table, so that the density processing is simpler and faster than the case where the density processing is performed by calculation. It has the effect that it can be done.

Further, by setting the overlap printing section 1 for one dot, a large amount of line feed at the time of recording can be adopted, so that the speed of printing one recording sheet, that is, the printing throughput is improved. There is also.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a heating element array and a recording density according to an embodiment of a thermal transfer printer of the present invention.

FIG. 2 is an explanatory diagram showing another state of the recording density in the embodiment.

FIG. 3 is a diagram illustrating a relationship between a heating element array and a recording density according to another embodiment of the thermal transfer printer of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between each heating element of a recording head and its surface temperature in a conventional thermal transfer printer.

FIG. 5 is an explanatory diagram showing a relationship between each heating element of a recording head and a recording density in a conventional thermal transfer printer.

FIG. 6 is an explanatory diagram showing a recording density of a recording head in a line feed state in a conventional thermal transfer printer.

FIG. 7 is an explanatory diagram showing a recording density in a line feed state of a recording head in a thermal transfer printer for comparison with the present invention.

FIG. 8 is a view for explaining a relationship between a heating element array and a recording density in a thermal transfer printer for comparison of the present invention.

FIG. 9 is an explanatory diagram showing a relationship between each heating element of a recording head and a recording density in a thermal transfer printer for comparison of the present invention.

[Explanation of symbols]

 1 Overprinted part 2 Adjacent part 3 Heating element row

Claims (4)

[Claims] 1. A thermal transfer printer that performs dot recording by pressing a recording head having a plurality of heating elements arranged in an array on a recording sheet via an ink ribbon to selectively heat the heating elements. In the printing of each line, a line feed is performed so that the printing area of the recording head partially overlaps with an overlapping printing section, and a position in the density correction area including the overlapping printing section and the adjacent section is located at the overlapping printing section. A thermal transfer printer, wherein a power amount smaller than a reference input power amount is supplied to the heat generating element, and a power amount equal to or more than the reference power supply amount is supplied to the heat generating element located in the adjacent portion. 2. An input power amount corresponding to a gradation of a reference recording density is set in advance for each heating element located in the overprinting portion and the adjacent portion, and the set input power amount is set to each of the heating elements. 2. The thermal transfer printer according to claim 1, wherein the thermal transfer printer is put into an element. 3. A thermal transfer printer that performs dot recording by pressing a recording head, in which a plurality of heating elements are arranged and arranged, against recording paper via an ink ribbon to selectively heat the heating elements. Line feeds are performed so that the print area of the recording head has an overprint portion that partially overlaps, and a dot having a print density higher than a reference print density in a density correction area including the overprint portion and an adjacent portion. A thermal transfer printer characterized by scattered low dots. 4. The thermal transfer printer according to claim 1, wherein the overlap printing section is for one dot.