JPH10309817A - Thermal transfer printer and ink sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate generation of a part where an image is not transferred because of a fold wrinkle even when heat energy of a thermal head is increased and an ink sheet wrinkles when it is folded. SOLUTION: The printer has a heating rate-judging means 22 and a driving control means 23. The heating rate-judging means 22 calculates a print rate from a ratio of a totally applied energy by a thermal head to a count of heating pixels to a total area of a count of pixels in a scan direction of an ink sheet at a printed image of each color and a count of pixels in a feed direction, and judges whether or not the print rate is a predetermined value or larger. The driving control means 23 transfers the ink sheet so that a next color ink of one set can be printed when the print rate of the other set of two sets of ink is not smaller than the predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal transfer printer and an ink sheet used for the thermal transfer printer.

[0002]

2. Description of the Related Art FIG.
And FIG. 10 is a perspective view of a main part of a conventional thermal transfer printer disclosed in Japanese Patent Application Laid-Open Publication No. H10-115,004. 9 and 10, reference numeral 1 denotes an ink sheet on which the yellow (Y), magenta (M), cyan (C), and black (K) inks are sequentially applied to the surface of the base film 1a. . Reference numeral 2 denotes a supply roll for supplying the ink sheet 1, and 3 denotes a take-up roll, which winds up the ink sheet 1 from which the ink has been thermally transferred and the ink has partially escaped. Reference numeral 4 denotes a thermal head, 5 denotes a heating element of the thermal head 4, 6 denotes a peeling member provided on the downstream side of the ink sheet 1, 7 denotes an ink sheet roller, 8 denotes a platen, and 9 denotes printing paper.

In the above configuration, the platen 8 is rotated while holding the ink sheet 1 and the printing paper 9 between the thermal head 4 and the platen 8, and the frictional force between the printing paper 9 and the ink sheet 1 To be transported. At the same time, the ink sheet 1 is heated by the heating element 5 by the electric signal to the thermal head 4 and the ink of the ink sheet 1 is thermally transferred to the printing paper 9 corresponding to the printing image. Further, the fed out ink sheet 1 is bent by the peeling member 6 attached to the thermal head 4 and is separated from the printing paper 9.
It is wound in the direction of arrow W onto the take-up roll 3 via the ink sheet roller 7. At this time, the heating of the thermal head 4 causes the ink sheet 1 as shown in FIG.
, A heated extension portion 10 of the heated base film 1a is generated. The heating extension portion 10 is a material in which the base film 1a material of the ink sheet 1 is partially thermally extended by heating, and is in a slack state as compared with a non-heated portion of the ink sheet 1.

FIG. 11 is an explanatory diagram showing a state in which folding wrinkles have occurred in the ink sheet. 10 and 11, an arrow E indicates a weak tension of the ink sheet 1 generated in the heated extension portion 10 of the ink sheet 1, and an arrow F indicates an ink sheet generated in the unstretched (unheated) portion of the ink sheet 1. 1 shows normal tension due to winding. G is a slack portion generated at the boundary between the heated extension portion 10 and the unheated portion. As described above, in thermal transfer printing, the ink sheet 1 usually becomes larger or smaller due to heating during thermal transfer, and the ink sheet 1 is loosened due to thermal expansion. At the boundary between the heated portion and the unheated portion, the slack portion G is in a swelling state.
At the start of the next color printing, the thermal head 4 is once separated from the platen 8 and the printing paper 9 is returned to reset. Then, when the thermal head 4 comes into contact with the platen 8 again, the slack portion G is folded between the thermal head 4 and the platen 8, and a folded wrinkle H is generated. As a result,
1 is caused by the fold wrinkles H generated on the ink sheet 1.
As shown in FIG. 2, there occurs a problem that a portion 11 where an image is not transferred occurs. In FIG. 12, after printing the ink color of the ink sheet 1 in magenta (M color), the portion 11 where the next ink color is not transferred to the head of cyan (C color)
Shows an example where appears.

[0005] Further, the weak tension E of the ink sheet 1 generated in the heating and extending section 10 by printing and the normal tension F of the ink sheet 1 in the unstretched (unheated) section where printing is not performed.
As shown in FIG. 13, there is also a problem that the skew force S acts at the time of printing the next color and the position of the print is shifted at the rear end of the print as shown in FIG. (In FIG. 13, M
The figure shows an example in which the color C of the next color after printing the color is shifted. )

[0006]

In the conventional thermal transfer printer as described above, the heating of the ink sheet 1 by the thermal head 4 is adjusted to be within the imbalance limit of the tension of the ink sheet 1 or the ink sheet 1 is folded. The tension of the ink sheet 1 immediately before the thermal head 4 is adjusted in order to keep the slack amount which becomes H within the limit, the tension of winding the ink sheet 1 is adjusted, the bias of the tension in the peeling member 6 and the imbalance of the tension are determined. Adjustments are made to reduce the uniform distribution, finely adjust the frictional force, and increase the slack amount of the heated and expanded ink sheet 1 by making the shape of the ink sheet roller 7 thick to make the tension uniform. I was However, in any case, if the heating energy by the thermal head 4 is increased in order to improve the printing density, the thermal expansion of the base film 1a increases, and the ink sheet 1 loosens and the folding wrinkles H increase. Was.

[0007] In addition, left and right imbalanced printing is performed,
If the heating becomes unbalanced in the right and left directions, there is a problem that the misregistration of the print of the next color easily occurs.

According to the present invention, even if the thermal energy of the thermal head is increased to improve the printing density and the wrinkles of the ink sheet are generated, it is possible to eliminate the occurrence of the portion where the image is not transferred due to the wrinkles and to improve the right and left directions. Provided is an ink sheet and a thermal transfer printer that prevent a printing paper from being displaced by a skew force at a printing rear end due to a skew force when printing a next color even when unbalanced heating energy is generated. Aim.

[0009]

According to a first aspect of the present invention, there is provided a thermal transfer printer comprising: a base film on which an ink sheet in which a plurality of color inks are grouped as a set and the printing surfaces of the respective inks are sequentially arranged in a feed direction; In a thermal transfer printer, which is selectively heated by a thermal head in the order of a predetermined ink color and thermally transferred onto a printing paper, the thermal head covers the entire area of the number of pixels in the scanning direction and the number of pixels in the feeding direction of the ink sheet in printing of each color. A printing rate is calculated based on a ratio of the total applied energy to the number of heated pixels, and a heating rate determination unit that determines whether the printing rate is equal to or more than a predetermined value, and a printing rate in one of the two inks is equal to or more than a predetermined value. At this time, there is provided a drive control means for conveying the ink sheet so that the next set of the next color ink can be printed.

According to a second aspect of the present invention, in the thermal transfer printer, the heating rate determining means determines the printing rate in the second half of the printing screen with respect to the feeding direction of the ink sheet.

According to a third aspect of the present invention, there is provided a thermal transfer printer, comprising: forming a set of inks of a plurality of colors on a base film; In a thermal transfer printer in which a thermal head is selectively heated by a thermal head in order of color and thermally transferred onto a printing paper, a printing screen is divided into right and left with respect to a feeding direction of an ink sheet, and each color is printed on the left and right printing screens. The printing rate is calculated based on the ratio of the total applied energy to the number of pixels heated by the thermal head with respect to the total area of the number of pixels in the scanning direction and the number of pixels in the feeding direction of the ink sheet, and it is determined whether the difference between the left and right printing rates is equal to or greater than a predetermined value. A heating rate determining unit that performs printing when the difference between the printing ratios in one of the two sets of inks is equal to or greater than a predetermined value. It is obtained by a drive control unit for feeding.

In a thermal transfer printer according to a fourth aspect of the present invention, the heating rate determining means determines the difference in printing rate in the latter half with respect to the feed direction of the left and right print screens divided into two.

According to a fifth aspect of the present invention, there is provided a thermal transfer printer according to any one of the first to fourth aspects, wherein the ink sheet for a thermal transfer printer is disposed at the rearmost portion of a set forward in the feeding direction. The distance between the rear end of the imprint screen and the front end of the imprint screen arranged at the head of the rear group is set to １ ／ or more of the length of the imprint screen in the feed direction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a configuration diagram illustrating a main part of the thermal transfer printer. In FIG. 1, reference numeral 12 denotes an ink sheet. As shown in FIG. 2A, yellow (Y), magenta (M), cyan (C), and black (K) are sequentially formed on the surface of the base film 12a.
Of ink are arranged. Note that, in FIG. 2, the hatched portion is a heating extension portion in which wrinkles are generated due to high-energy printing. Reference numeral 13 denotes a supply roll for supplying the ink sheet 12, and reference numeral 14 denotes a take-up roll, which takes up the ink sheet 12 from which the ink has been transferred and the ink has been partially removed. Fifteen
Is a thermal head, 16 is a heating element of the thermal head 15, 17 is a peeling member provided on the downstream side of the ink sheet 12, 18 is an ink sheet roller, 19 is a platen,
0 is a printing paper.

Reference numeral 21 denotes a control device comprising a CPU, which comprises 22 to 24 to be described later. Reference numeral 22 denotes a heating rate determination unit, based on the printing data input from the control unit 24 described later, the heating pixels by the thermal head 15 with respect to the total area of the number of pixels in the scanning direction and the number of pixels in the feeding direction of the ink sheet 12 in printing of each color. The printing rate is calculated based on the ratio of the total applied energy to the number, and it is determined whether the printing rate is equal to or more than a predetermined value. A drive control unit 23 drives and controls the supply roll 13 and the take-up roll 14 of the ink sheet 12 by a motor (not shown). A control unit 24 controls the thermal head 15, the platen 19 and the drive control unit 23 based on the print data sent from a host computer (not shown), and outputs the print data to the heating rate determination unit 22. .

Next, the operation will be described. In FIG. 1, the control means 24 performs the following processing based on an input signal of print data from a host computer (not shown). The total number of heating elements in the scanning direction of the thermal head 15 is a, the number of printing lines in the feeding direction of the printing paper 20 is t, and the maximum number of gradations that can be applied to a single heating element is n. 100% printing rate when printing solid
%. If the number of gradations applied to each element A selectively heated by the thermal head 15 during actual image printing is N and the number of actual printing lines is T, the printing rate H ₀ is
H ₀ = ΣT (ΣA ・ n) / a ・ nt.

The limit printing rate h of energy heating printing on the thermal head 15 such that the ink sheet 12 becomes loose and folded wrinkles are expanded to the next printing area due to the thermal expansion of the base film 12a, from the material of the base film 12a. Set in advance. Then, the process shown in the flowchart of FIG. 3 is executed while determining whether or not the printing rate H ₀ of the actual printing exceeds the limit printing rate h. In the following description, the expression “large printing rate” indicates a case where the printing rate H ₀ exceeds the limit printing rate h.

The operation will be described below with reference to the flowcharts shown in FIGS. 1, 2 and 3. 2 in FIG. 2 indicate the order of printing. FIG. 2A shows the printing order when there is no printing of “large printing rate”. (B) is when the printing rate of all colors is “high printing rate”, (c) is that the printing rate of Y color is low,
The printing order for colors after "large printing rate" is shown. The ink sheet 12 is sequentially arranged as a set of four colors including three colors of Y color, M color, C color, or K color. In the description, numbers indicating pairs are used in combination with color symbols. For example,
Y ₁ colors 1 pair in the Y-color, C ₂ colors expressed as that second set of C-color.

First, the printing order in the case of FIG. 2A will be described. 1 for the first print color, yellow
To start from the set day of the Y _1-color (S _1). If the printing rate of the printed Y ₁ color is less than the limit value (S ₂ ), M
Executing the printing of _one color ink (S _3). Printed Y ₁
The processing in the case of “large printing rate” in which the printing rate of the color exceeds the limit value will be described later. If M ₁ color printing rate is less than the limit value (S
_4), executes the printing of the inks of C ₁ color (S _5). C ₁
If it is less than the color printing rate limit (S _6), it executes the printing of the inks of K ₁ color (S _7). Here K ₁ color printing rate is less than the limit value (S _8), if the second set has been used (S _9), color printing is completed.

Next, Y color, M color, and C color shown in FIG.
The processing order when all the printing rates of the colors K and K exceed the limit values will be described. The beginning of the printing of yellow color, which is a photographic color to start from the first set of Y _1-color (S _1). Y printed
If _one color printing rate has exceeded the limit value "printing ratio large" (S _2), the drive control unit 23 conveys the ink sheet 12 to the second set of M _2-color (S _10), M to the printing of _two colors (S _11). If printing the M _2-color printing rate of not less than the limit value (S _12), the drive control unit 23 of the ink sheet 12 1
Rewind to set th C ₁ color (S _13), executes the printing of the C ₁ color (S _5). If C ₁ color printing rate of not less than the limit value (S _6), drive control means 23 conveys the ink sheet 12 to the second set of K ₂ colors (S _14), executes the printing of the K ₂ colors to (S _15).

[0021] is less than the limit value M _2-color printing rate (S
_12), continues to execute the printing of the C ₂ colors (S _16). C
If _two color printing rate of not less than the limit value (S _17), the drive control unit 23 rewinds the ink sheet 12 to the first set of K ₁ color (S _18), executes the printing of the K ₁ color (S _7). C ₂
If it is less than the limit value color printing rate of (S _17), subsequently K
Executing the printing of the _two colors (S _15). If it is less than the limit value K ₂ color printing rate of (S _19), color printing is completed. However, if K ₂ color printing rate is equal to or greater than the limit value (S _19), because the wrinkles of the ink sheet 12 extends to the top of Y _3-color portion of the next third set, further wrinkle free follows 4 the ink sheet 12 to the top Y ₄ color set eyes and transported by the drive control unit 23 (S _20), a series of printing is completed.

Next, the processing in the case where the printing rate of the Y color shown in FIG. 2C is less than the limit value and the printing rates of the other M colors, C colors and K colors are not less than the limit values will be described. 1 which is the first print color
Since the set-th Y ₁ color is less than the printing rate limit value (S _2), it executes the printing of the inks of M ₁ color (S _3). If M ₁ color printing rate of not less than the limit value (S _4), the drive control unit 23 conveys the ink sheet to the second set of C ₂ colors (S _21), the printing of the C ₂ colors ( S _16). If it is less than C ₂ color printing rate limit value (S _17), executes the subsequent printing of the K ₂ colors (S _15). K ₂
When the printing rate of the color is equal to or more than the limit value, it is the same as the case of FIG.

[0023] In the C _2-color printing rate of not less than the limit value (S _17), and rewinding the ink sheet 12 to the first set of K ₁ color to the drive control unit 23 (S _18), the printing of the K ₁ color run (S _7). Here, K ₁ color if the printing ratio is equal to or greater than the limit value (S _8), since the wrinkles of the ink sheet 12 spans the top of the Y _2-color portions of the second set, wrinkle-free following third set the head of the Y ₃ colors to the ink sheet 12 to the drive control means 23
It conveyed by (S _22). In addition, 2 times before K ₁ color printing
When any of the inks in the set has been used, the ink in the second set cannot be used, and therefore the first Y _{3 in the} next set is used.
Conveying the ink sheet 12 by the drive control means 23 until the color (S _22).

The processing procedures of the three representative examples have been described above.
The processing flow shown in FIG. 3 can cope with the magnitude of the limit value of the printing ratio of any color. That is, using two sets of ink sheets, it is determined whether the wrinkles of the ink sheet reach the ink portion of the next color based on the limit value of the printing rate. And Y
Printing is performed while maintaining the order of the colors M, C, C, and K, and selecting ink having no wrinkles at the head and controlling the conveyance and rewinding of the ink sheet. As a result, even if the heating energy of the thermal head is increased to improve the print density,
It is possible to eliminate printing defects due to wrinkles of the ink sheet.

In the flowchart of FIG. 3, the printing rate of the printed image is determined. However, at the stage where the printing data sent from the host computer is taken in and the output signal to the thermal head is generated, the printing is performed. The same operation can be performed even if the rate is determined.

Embodiment 2 FIG. FIG. 4 is an explanatory diagram for explaining the logic of determining the printing rate according to the second embodiment of the present invention, and shows a method of calculating the printing rate by dividing the printing screen into two in the feed direction. FIG. 5 is a flowchart showing the printing operation.
Except part determines the printing rate (S ₂₃ ~S ₂₆₎ is the same as in the first embodiment. 6 is a flowchart showing details of a portion (S ₂₃ ~S ₂₆₎ to obtain the printing ratio 5.
As shown in FIG. 4, the printing screen is divided into two in the right and left directions in the feeding direction of the ink sheet 12, and the printing ratio is obtained for each of the two divided printing screens. The method of obtaining the same is the same as in the first embodiment. 1 and 4, the thermal head 15
Since the total number a of the heating elements in the scanning direction is divided at the center and one of the heating elements is a ₁ and the other is a ₂ , a = a ₁ + a ₂ . Then, the printing rate H ₁ of one indicia _{screen, H 1 = ΣT (ΣA 1} · N) / a 1 · n ·
t. Further, the printing rate H ₂ of the other printing screen is H ₂
= ΣT (ΣA ₂ · N) / a ₂ · n · t. Hereinafter, description will be given along the flowchart of FIG.

The printing rate H ₁ of one of the two divided printing screens,
Obtaining the printing rate of H ₂ other indicia screen (S _27, S _28).
Then calculates the printing ratio H ₀ of the total (S _29). In this calculation, since the number a of the heating elements is divided at the center, there is a relationship of a ₁ = a _2. Therefore, the respective printing rates H ₁ , H ₂ to H ₀ =
It can be simply calculated by (H ₁ + H ₂ ) / 2. If the overall printing rate H ₀ is equal to or greater than the limit printing rate h, the printing of the next color is conveyed to another set of inks on the ink sheet and executed as “large printing rate” (S ₃₀ ). If the total printing rate H ₀ is less than the limit printing rate, it determines the difference of the printing ratio H ₁ and H ₂ (S _31). Then, if the absolute value U of the difference between the left and right printing rates is equal to or greater than the predetermined value u, processing is executed as "large printing rate" ( _S32 ).

As described above, the printing screen is divided into two parts in the left and right directions with respect to the feeding direction of the ink sheet, and the difference in printing ratio between the two divided printing screens causes imbalance in the heating energy of the printing screen. Then, it is determined whether or not the printing position is shifted at the printing rear end. Then, when the difference is large, the Y color, the M color,
Printing can be performed while maintaining the order of C and K colors and controlling the conveyance and rewinding of the ink sheet so that the printing position does not shift at the rear end of the printing.

Embodiment 3 FIG. 7 is an explanatory diagram showing the logic of the print ratio determination according to the third embodiment. 1 and 6, the heating rate determination means divides the latter half of the printing screen into two parts, left and right, with respect to the feeding direction of the ink sheet 12. further,
As in the first embodiment, printing is performed by the ratio of the total applied energy to the number of pixels heated by the thermal head 15 to the total area of the number of pixels in the scanning direction and the number of pixels in the feeding direction of the ink sheet 12 in each color printing on the left and right printing screens. Rate H ₁ , H ₂
Is calculated. The conveyance control of the ink sheet 12 performed using the printing ratio calculated as described above is the same as in the second embodiment.

As described above, the first half portion where the slackness of the ink sheet does not affect the printing of the next color due to the large printing rate or the uneven distribution of the printing rate is excluded from the printing rate determination target, and the printing screen greatly affects the next color printing. Since the printing rate is determined in the latter half of the printing process, even when the printing rate is large or the uneven distribution of the printing rate is concentrated in the first half of the printing screen, the ink sheets can be effectively used without using two sets of ink sheets. it can.

In the third embodiment, the ink sheet 12
Divides the second half of the printing screen into two parts,
A description has been given of the case where the difference between the printing ratios of the left and right printing screens is determined. However, the same effect can be expected by determining whether or not the printing ratio is equal to or greater than a predetermined value in the second half of the printing screen in the first embodiment.

Embodiment 4 FIG. In FIG. 8, reference numeral 25 denotes an ink sheet, and a plurality of colors (yellow: Y, magenta: M, cyan: C, black:
(K color) ink printing screens are sequentially arranged. In addition,
The hatched part in FIG. 8 is a heating extension part in which wrinkles are generated due to high energy printing. P is the application length of the ink to be the printing screen. D is the last color of a set of inks,
This is a blank portion indicating the distance from the Y color arranged at the head of the next set, where D> P / 4. This depends on the heat resistance of the material of the base film 25a of the ink sheet 25, but the size of the printing paper on which the thermal transfer printing is performed is A3.
According to the data obtained by various experiments for the plate and A4 size, 塗布 of the ink application length P of the printing screen of each color is used.
Above, preferably 1/3 or more.

In general, the ink application length P may be longer than the maximum length actually printed on paper, and if the actual print length L is 2/3 or less of the ink application length P, the application interval between the colors is increased. No need. However, in this case, one third of the applied ink is not used and is uneconomical. Therefore, after the ink application length P, which is the maximum length of the actual printing length, the application of the ink is stopped and a blank is formed, and the length of the blank portion D is set to be 1/4 or more of the ink application length P. Good. However, if the blank portion D is carelessly lengthened, the length of one set of ink sheets becomes longer, and the number of prints per ink sheet roll is reduced. Therefore, blank portion D = P / 4 to P / 2
Is appropriate.

As described above, between the last black color (K color) of one set of prints and the leading color yellow (Y color) of the next print, 1/1 of the ink application length P of each color is set. By providing a blank portion having a distance of 4 or more, even if the printing ratio of the K color is large, it is possible to eliminate waste of a next series of ink. This corresponds to S _{20 in} the flowchart of FIG.
And it can be omitted S _22.

[0035]

According to the first aspect of the present invention, when the printing ratio of one of the two sets of ink is equal to or greater than a predetermined value, the ink sheet is conveyed so that the next color ink of the other set can be printed. Thus, even if the heating energy of the thermal head is increased, it is possible to prevent a printing failure due to a folding wrinkle of the ink sheet and improve a printing density.

According to the second aspect of the present invention, the first half which does not affect the next color printing is excluded from the printing rate determination target, and the printing rate is determined in the second half of the printing screen. Even when large areas are concentrated, they can be used effectively without using two sets of ink sheets.

According to the third aspect of the present invention, when the difference between the printing ratios of one set on the left and right printing screens is equal to or greater than a predetermined value, the other is divided into two in the left and right directions with respect to the feeding direction of the ink sheet. By transporting the ink sheet so that the next color ink of the set can be printed, it is possible to prevent a shift at a printing rear end portion due to imbalance of heating energy to a printing screen, and to perform proper printing.

According to the fourth aspect of the present invention, the first half which does not affect the next color printing is excluded from the printing rate determination target, and the printing rate is determined in the second half of the printing screen. Even when large areas are concentrated, they can be used effectively without using two sets of ink sheets.

According to the fifth aspect of the present invention, the distance between the rear end of the printing screen arranged at the end of the front set and the front end of the printing screen arranged at the head of the rear set is determined by the feed of the printing screen. By setting the length in the direction to 1/4 or more, even if the printing ratio of the ink disposed at the end of the front group is large, each ink of the rear group can be effectively used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a thermal transfer printer according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an ink sheet printing order in the thermal transfer printer according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a printing process according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the print ratio of the divided left and right print screens in Embodiment 1 of the present invention.

FIG. 5 is a flowchart showing a printing process according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing the printing process of the main part of FIG.

FIG. 7 is an explanatory diagram showing a printing rate according to the third embodiment of the present invention.

FIG. 8 is a plan view of an ink sheet according to Embodiment 4 of the present invention.

FIG. 9 is a configuration diagram showing a main part of a conventional thermal transfer printer.

FIG. 10 is a perspective view showing a main part of a conventional thermal transfer printer.

FIG. 11 is an explanatory diagram illustrating a state in which folding wrinkles have occurred in the ink sheet.

FIG. 12 is an explanatory diagram showing a state in which color missing has occurred in a print due to a folding wrinkle of an ink sheet.

FIG. 13 is an explanatory diagram showing a state in which a print misalignment has occurred on a print sheet.

[Explanation of symbols]

12, 25 ink sheet, 12a, 25a base film, 15 thermal head, 20 printing paper, 22
Heating rate determination means, 23 drive control means;

Claims (5)

[Claims] An ink sheet in which a plurality of color inks are arranged as a set on a base film and a printing screen of each ink is sequentially arranged in a feed direction is selectively formed by a thermal head in a predetermined color order of the ink. In the thermal transfer printer which heats and heat-transfers onto printing paper, the ratio of the total energy applied to the number of pixels heated by the thermal head to the total area of the number of pixels in the scanning direction and the number of pixels in the feeding direction of the ink sheet in the printing of each color. And a heating rate determining means for determining whether or not the printing rate is equal to or greater than a predetermined value. When the printing rate in one of the two inks is equal to or greater than a predetermined value, the next color of the other set is used. And a drive control means for conveying the ink sheet so that ink can be printed. 2. The thermal transfer printer according to claim 1, wherein the heating rate determination means determines the printing rate in the latter half of the printing screen with respect to the feeding direction of the ink sheet. 3. An ink sheet in which a plurality of color inks are grouped as a set on a base film and the printing surfaces of the respective inks are sequentially arranged in a feed direction is selectively selected by a thermal head in a predetermined color order of the inks. In a thermal transfer printer that heats and transfers heat onto printing paper, the printing screen is divided into two parts in the left and right directions with respect to the feeding direction of the ink sheet. The printing rate is calculated from the ratio of the total applied energy to the number of pixels heated by the thermal head to the total area of the number of pixels in the scanning direction and the number of pixels in the feeding direction, and it is determined whether the difference between the right and left printing rates is equal to or greater than a predetermined value. Heating rate determination means,
Drive control means for transporting the ink sheet so that the next color ink of the other set can be printed when the difference between the printing ratios in one of the two sets of inks is equal to or greater than a predetermined value. And thermal transfer printer. 4. The thermal transfer printer according to claim 3, wherein the heating rate determining means determines a difference in a printing rate in a second half with respect to a feed direction of the left and right print screens divided into two. 5. The ink sheet for a thermal transfer printer according to claim 1, wherein a rear end of a printing screen arranged at a rearmost portion of a set in the front in the feed direction;
The distance from the top of the imprint screen located at the beginning of the
An ink sheet wherein the length of the printing screen in the feed direction is 1/4 or more.