JPH068489A - Image recording method and apparatus - Google Patents

Abstract

PURPOSE:To carry out printing of high tone reproducibility as a whole by overlapping the printing based on the characteristics of obtaining the largest, maximum density with the printing of superior density specialized in its tone reproducibility of low density. CONSTITUTION:An image data is divided into high-order bits and low-order bits by an image data dividing circuit 11, and a heat transfer film having different density between the high-order bits and low-order bits is selected by a selecting means 15, and a film selected by a heat transfer film driving mechanism 15 is driven. Printing based on the high-order bits and low-order bit data is overlapped by a thermal head control means 12 based on a density-pulse applying time conversion head table found and set preliminarily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method and apparatus capable of reproducing high gradation by preparing thermal transfer films having different density characteristics in image recording using a thermal transfer printer.

[0002]

2. Description of the Related Art Conventionally, as a color printer using a sublimation transfer method, 8 bits (2 bits) for each color of yellow (Y), magenta (M), cyan (C), and black (Bk).
Models that perform gradation control by transfer data of 56 gradations are commercially available. With this printer, it is possible to express 16 million colors, which is sufficiently practical for general images, and obtain a print in which rich color tones are reproduced.

However, in computer graphics (CG) images and monochrome / monotone images that frequently use smooth gradations, gradation expression is more important than the number of colors that can be expressed, so gradation reproduction is particularly important. In this case, in the present case, the gradation expression is insufficient in the current 256 gradation printer depending on the application. Also recently
Input devices capable of handling multi-gradation (about 12 bits) data have come to the market, and printers are also required to support higher gradations (multi-gradation).

[0004]

[Problems to be Solved by the Invention]
In the gradation control method based on bit transfer data, gradation (density) is controlled by the number of pulses applied to the heating resistor of the corresponding thermal head based on 8-bit multi-valued data in units of pixels. An example of this gradation control method will be outlined with reference to FIG.

For example, image data input from an external device such as a host computer via the I / F 1 is written in the buffer memory 2. The data written in the buffer memory 2 is read line by line by the thermal head control circuit 3 and sequentially compared with the values of 0 to 255 for each pixel. First, the density data of each pixel is compared with "0", and for density data equal to or larger than "0", "1" is present at that position, and for density data smaller than "0". A pulse train for each pixel for one line in which "0" is arranged at that position is output.

That is, the output from the thermal head control circuit 3 should be "1" at the position of the density data which is greater than or equal to "0" and "0" at the other positions. become. This pulse train is timing-controlled and set in the shift register 41 in the print head 4. The latch circuit 42 latches the data in the shift register by the latch signal from the thermal head control circuit 3. During the period when the enable signal is applied to the gate circuit 43, only the heating resistor 44 corresponding to the bit that latches "1" among the bits of the latch circuit 42 is selectively driven to generate heat and recording is performed. . Next, the thermal head control circuit 3 compares the transfer data with "1",
For the density data whose density data is equal to or greater than "1", "1" is placed at that position, and when the density data is less than "1", "0" is placed at that position for each pixel of one line. Output a pulse train. In this way, the pulse train output from the thermal head control circuit 3 is timing-controlled and set in the shift register 41 and latched by the latch circuit 42. As described above, "1" is set in the bit of the latch circuit 42. The heating resistor 44 corresponding to the existing bit is driven and recording is performed. Hereinafter, the same operation is repeated until the comparison value reaches the maximum density data “255”, and the transfer of one line is completed.

FIG. 10 shows how one heating resistor in FIG. 9 is driven according to the density data. The numbers from 1 to 256 at the upper part indicate the printing period of one line. In the figure, each generation time point in the case where one enable pulse is generated 256 times in order is shown, and each rectangle arranged in the lateral direction with respect to each of these generation time points has density data D = 0, 1
In the case of 5, 31, 47, 255, the heating resistor is driven, the shaded rectangle indicates that the heating resistor is driven, and the white rectangle indicates that the heating resistor is not driven. Shows. Corresponding to the 1st to 256th enable pulses, the density data and 0 to 25
Values up to 5 are compared.

That is, when D = 0, the heating resistor is driven only during the period when the first enable pulse is generated, and thereafter is not driven at all, and when D = 15, the first resistor is driven. It is driven while the 16th enable pulse from the enable pulse is generated, and is not driven thereafter. In this way, gradation recording according to the density data D is performed.

FIG. 11 shows a sublimation transfer printer as an example of a printer to which the present invention is applied. The transfer film used has, for example, a frame sequential structure having Y, M, C, and Bk as shown in FIG. 11A, and the transfer mechanism is as shown in FIG. 11B. There is. The transfer film 21 includes a heat resistant slipping layer 21a and a transfer base material 21.
b, the sublimation transfer layer 21c is laminated with a primer interposed in order to improve the adhesion of the coating material to the base material.
A film that has been subjected to an easy-adhesion treatment may be used. As the heat resistant slipping layer 21a, a mixture of polyvinyl butyral, polyisocyanate and phosphoric acid ester, a transfer base material 2
1b is made of polyethylene terephthalate, polyimide or the like, and the sublimation transfer layer 21c is made of a sublimable dye such as indoaniline-based, pyrazolone-based or azo-based dye, polyvinyl acetal or cellulose-based binder.

The image receiving paper 22 is formed by laminating an image receiving layer 22b and an image receiving paper base material 22a with a primer interposed therebetween. The image receiving layer 22b is saturated polyester, vinyl chloride or the like, and the base material 22a is synthetic paper, foamed polyester, or the like. The back surface layer, such as foamed polypropylene, is composed of a binder, a lubricant, a coating agent and the like. Further, the vinyl chloride resin itself may be used as the receiving layer.

The image receiving paper 22 is provided around the platen roll 23.
Is wound around, and the transfer film 21 is superposed on the transfer film 21 in a state of being closely attached to the transfer film 21.
By contacting and heating the back surface of the dye, the dye moves to the image receiving layer according to the amount of heat applied, so that it is possible to perform gradation recording according to the amount of heat for each pixel dot.

In such a conventional gradation reproduction method, 25
In order to achieve gradation reproduction of 6 gradations or more, it is necessary to develop gradation control technology for the printer data processing unit, thermal head drive unit, etc. to match the new data width. There was a problem that it was technically difficult.

An object of the present invention is to solve the above problems, and an object thereof is to provide an image recording method and apparatus capable of reproducing high gradation.

[0014]

SUMMARY OF THE INVENTION The present invention comprises a thermal transfer film having a color material layer provided on one surface of a substrate and a thermal transfer sheet having a receiving layer provided on one surface of the substrate. The thermal head, which has a heating resistor, is pressed against the platen roller, and a pulse is applied to the thermal head for a period of time according to the image data to energize and generate heat, from the color material layer of the thermal transfer film to the receiving layer of the thermal transfer sheet. In the image recording method for reproducing the gradation by controlling the transfer amount of the color material to the gradation, the gradation is reproduced by using at least two kinds of thermal transfer films having color material layers having different density characteristics.

The present invention is characterized in that the density characteristics of the two types of thermal transfer films are a density characteristic in which the rising is gentle with respect to the applied energy and a density characteristic in which the rising is steep and the maximum density is large.

The present invention divides image data into two or more,
It is characterized in that the divided image data is printed on a thermal transfer film having different density characteristics.

According to the present invention, a thermal transfer film having a color material layer provided on one surface of a base material and a thermal transfer sheet having a receiving layer provided on one surface of the base material are used as a thermal transfer film having a plurality of heating resistors. Transfers the color material from the color material layer of the thermal transfer film to the receiving layer of the thermal transfer sheet by pressing the head and the platen roller and applying a pulse to the thermal head for a time according to the image data to energize and generate heat. In the image recording method of controlling the amount and reproducing the gradation, one color is divided into a plurality of times for printing, and the applied voltage to the thermal head is changed for each time of recording.

According to the present invention, by changing the voltage applied to the thermal head, one color is printed with a density characteristic with a gentle rise and a density characteristic with a steep rise and a large maximum density with respect to the applied energy. It is characterized by having done.

The present invention divides the image data into two or more,
The feature is that printing is performed by changing the voltage applied to the thermal head for each divided image data.

The present invention is characterized in that printing is carried out by using a method in which a thermal transfer film having different density characteristics is used and a method in which a voltage applied to a thermal head is changed.

Further, the present invention has a thermal head control means for inputting image data, and a plurality of heating resistors.
A thermal transfer film in which a thermal head in which each heating resistor is selectively driven by a thermal head control unit and a platen roller are provided, and a color material layer is provided on one surface of the base material and one surface of the base material are provided. A thermal transfer sheet provided with a receptive layer is pressed between the thermal head and the platen roller, and a pulse is applied to the thermal head for a period of time according to the image data to energize and generate heat. An image recording apparatus that reproduces a gradation by controlling the transfer amount of the color material to the image forming apparatus further includes a thermal transfer film selection unit, and the thermal head control unit drives and controls the thermal transfer film selection unit to obtain colors having different density characteristics. Select and use at least two types of thermal transfer film having a material layer,
The feature is that the gradation is reproduced.

Further, the present invention further comprises image data dividing means for dividing the image data into two or more, and the thermal head control means drives and controls the thermal transfer film selecting means for each data divided by the image data dividing means. It is characterized in that a thermal transfer film having color material layers having different density characteristics is selected and printed.

Further, the present invention is characterized in that the density characteristics of the two types of thermal transfer films are a density characteristic in which the rising is gentle with respect to the applied energy and a density characteristic in which the rising is steep and the maximum density is large.

Further, the present invention has a thermal head control means for inputting image data, and a plurality of heating resistors.
A thermal transfer film in which a thermal head in which each heating resistor is selectively driven by a thermal head control unit and a platen roller are provided, and a color material layer is provided on one surface of the base material and one surface of the base material are provided. A thermal transfer sheet provided with a receptive layer is pressed between the thermal head and the platen roller, and a pulse is applied to the thermal head for a period of time according to the image data to energize and generate heat. In an image recording apparatus that reproduces gradation by controlling the transfer amount of the color material to one, printing is performed by dividing one color into a plurality of times and changing the voltage applied to the thermal head for each printing. Characterize.

Further, the present invention further comprises an image data division circuit for dividing the image data into two or more, and the thermal head control means changes the voltage applied to the thermal head for each data divided by the image data division circuit. Characterized by printing.

Further, according to the present invention, the voltage applied to the thermal head is set to a voltage value at which a density characteristic having a gentle rising with respect to the applied energy and a density characteristic having a steep rising and a large maximum density are obtained. Is characterized by.

[0027]

According to the present invention, gradation reproducibility is improved by performing printing a plurality of times with different density characteristics with respect to applied energy, and a plurality of thermal transfer films having color material layers having different density characteristics are used. , And / or the density characteristics are made different by varying the applied voltage to the thermal head, the density characteristics rise sharply with respect to the applied energy, and the thermal transfer film prints with a characteristic that the maximum density is large and the recording density rises with the applied energy. However, the gradation reproducibility as a whole can be improved by overlapping the printing with the thermal transfer film having the characteristic of being excellent in gradation at low density.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of an image recording apparatus of the present invention, and FIGS. 2, 3 and 4 are diagrams for explaining the image recording principle of one embodiment of the present invention. In the figure, 11 is an image data dividing circuit, 12 is a thermal head control means, 13 is a density-pulse application time conversion table, 14 is a thermal head, 15 is a thermal transfer film selecting means, and 16 is a thermal transfer film driving mechanism.

First, the image recording principle of this embodiment will be described with reference to FIGS. 2, 3 and 4. For example, as shown in FIG.
A thermal transfer film having a coloring material layer whose density characteristics with respect to applied energy are as shown by D ₁ and D ₂ is prepared. The thermal transfer film having the density characteristic D ₁ has a gentle rising of the printing density with respect to the applied energy and has a low maximum density, but has excellent low-density gradation reproducibility.
The thermal transfer film having the density characteristic D ₂ has a steep rising of the printing density with respect to the applied energy and is inferior in the gradation reproducibility of low density, but can obtain a high maximum density.

On the other hand, as shown in FIG. 3, for example, the image data has 10 bits (a ₁ a ₂ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆
b ₇ b ₈ ), this image data is divided into, for example, upper 2 bits and lower 8 bits, and the upper 2 bits (a ₁ a ₂ ) are (00) ... Density 0 (01). to correspond to the concentration OD ₁ (10) ...... concentration 2OD ₁ (11) ...... concentration _{3OD 1, 0~OD 1, OD 1} ~2OD concentration
_1, 2OD _{1 ~3OD 1,} divides 3 OD ₁ or more into four areas. Then, as shown in FIG. 4, the upper 2 bits (a ₁ a ₂ ) of the image data are printed by using the thermal transfer film having the characteristic D ₂ , and the lower 8 bits (b ₁ b ₂ b) are overlapped and printed.
_{3 b 4 b 5 b 6 b} 7 b 8) to be printed by the thermal transfer film characteristics D _1. That is, the characteristics D ₂ and O shown by the broken line in FIG.
The intersections with D ₁ , 2OD ₁ and 3OD ₁ are printed with a thermal transfer film having the characteristic D ₂ , and the density is 0 to O when superposed.
D _1, concentration _{OD 1 ~2OD 1, 2OD 1 ~3OD} 1, 3
Each density section of OD ₁ or more is printed by the thermal transfer film having the characteristic D ₁ .

For example, the density (O
D when performing printing of _P), the characteristic D concentration in the thermal transfer film ₂ is printed by applying energy, such as a 2 OD _1, thereon characteristics D ₁ of the thermal transfer film density OD _P
Printing is performed with applied energy such that At this time, the applied energy can be changed by changing the drive pulse width of the thermal head, and the relationship between the density and the drive pulse width is stored as conversion tables for the merging characteristics D ₁ and D ₂ , respectively. Print it by referring to this.

In this way, the OD for the concentration to be reproduced
₁₎ , 2OD ₁ and 3OD _{1 where} the large density change portion with respect to the applied energy is the thermal transfer film of the characteristic D ₂ , and small density change portions with respect to the applied energy are printed using the thermal transfer film of the characteristic D ₁ which is excellent in reproducibility of low density. Therefore, high gradation printing can be performed as a whole.

Such printing is performed by the device configuration shown in the functional block diagram of FIG. That is, the image data dividing circuit 11 divides the image data into upper bits and lower bits, the selecting means 15 selects a thermal transfer film having different density characteristics between the upper bits and the lower bits, and the thermal transfer film driving mechanism 15 selects the thermal transfer film. Drive the film. The thermal head control means 12 superimposes printing based on the upper bit data and the lower bit data based on the density-pulse application time conversion table obtained in advance.

In the above description, the upper bit and the lower bit are divided into two, but the lower bit (b
₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ ) is divided into (b ₁ b ₂ ) and (b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ ) and (b
The density characteristic of ₁ b ₂ ) and the density characteristic of (b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ ) may be different from each other for printing.

Next, the structure of the thermal transfer film will be described. When switching the thermal transfer film at one density level, for example, as shown in FIG. 5A, there are two density characteristics D ₁ and D ₂ . Use a thermal transfer film. When driven by a single head, Y (D ₁ ) and Y (D ₂ ) for yellow and M for magenta.
(D ₁ ), M (D ₂ ), for cyan C (D ₁ ),
C (D ₂ ) ... Density characteristic D for each color
Areas ₁ and D ₂ are formed in a frame sequential manner. When printing,
First, one page of Y is printed with the thermal transfer film having the density characteristic D ₁ , and then the thermal transfer film having the density characteristic D ₂ is printed. Similarly, for magenta and cyan, one page is printed with the thermal transfer film having the density characteristic D ₁ and then the thermal transfer film having the density characteristic D ₂ is printed.

In the case of a multi-head, FIG. 5 (b)
As shown in FIG. 5, areas of density characteristics D ₁ and D ₂ are alternately prepared for each of Y, M, and C, and each color may be printed in the same manner as in the case of FIG. 5A. .

6 to 9 are views showing another embodiment of the present invention. In the figure, 17 is an applied voltage varying means. In the present embodiment, the print density characteristic with respect to the applied energy is made different by changing the driving voltage of the thermal head. That is, as shown in FIG. 7, when the driving voltages are V ₁ and V ₂ (V ₁ <V ₂ ), the print density rises gently with respect to the applied energy and the maximum density is low, but low density gradation reproducibility is obtained. Excellent concentration characteristics D ₁ ,
The print density rises sharply against the applied energy,
Although the gradation reproducibility of low density is inferior, the density characteristic D ₂ that achieves high maximum density is realized. By thus changing the applied voltage, the density characteristics are changed, and the same printing as described above is performed.

That is, similarly to the case shown in FIG. 3, the image data is divided into upper bits and lower bits, and, for example, the image data has 10 bits (a ₁ a ₂ b ₁ b ₂ b ₃ b ₄ b ₅ b
₆ b ₇ b ₈ ), this image data is divided into upper 2 bits and lower 8 bits, and the upper 2 bits (a ₁ a ₂ ) are (00) ... Density 0 (01) ... Density OD ₁ (10) ... concentration 2 OD ₁ (11) is associated as ...... concentration 3OD _1, 0~OD ₁ concentration, OD ₁ ~2OD
_1, 2OD _{1 ~3OD 1,} divides 3 OD ₁ or more into four areas. Then, as shown in FIG. 8, the upper 2 bits (a ₁ a ₂ ) of the image data are printed by the characteristic D ₂ with the driving voltage of the thermal head as V ₂ , and the lower 8 bits (b ₁ b) are superimposed on this. the _{2 b 3 b 4 b 5 b} 6 b 7 b 8), is printed by characteristics D ₁ a driving voltage as V _1. That is, the characteristics D ₂ and OD ₁ , 2OD ₁ , 3OD ₁ shown by the broken line in FIG.
Intersections between the printing is performed with characteristic D ₂ (drive voltage V _2), superimposed on this, concentration 0～OD _1, concentration OD ₁ ~2OD _1,
Characteristic D ₁ (driving voltage V ₁ ) is printed in each density section of 2OD _{1 to} 3OD ₁ and 3OD ₁ or more.

As described above, by changing the voltage applied to the thermal head and selecting the print density characteristics D ₁ and D ₂ , it is possible to perform high gradation printing as a whole.

In the present embodiment, as shown in FIG. 6, the image data division circuit 11 divides the image data into upper bits and lower bits, and the thermal head control means 12 divides the upper bit data and the lower bit data. Thermal head 1
By changing the voltage applied to No. 4 and performing overprinting on the same pixel, high gradation reproduction can be performed.

In the above embodiment, printing with different recording characteristics is shown by using a thermal transfer film having color material layers with different density characteristics and by applying different voltages to the thermal head. It goes without saying that the density characteristics may be made different by using the above method, and overlapping printing may be performed.

[0042]

As described above, according to the present invention, the printing based on the density characteristics that gives a large maximum density and the printing based on the density characteristics excellent in the low density gradation reproducibility are overlapped, and as a result, the total print quality is high. It is possible to perform printing with excellent tonality reproducibility.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an apparatus for recording an image according to the present invention.

FIG. 2 is a diagram showing different density characteristics.

FIG. 3 is a diagram illustrating division of image data.

FIG. 4 is a diagram illustrating the principle of image recording according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a thermal transfer film.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing different density characteristics.

FIG. 8 is a diagram illustrating an image recording principle of another embodiment of the present invention.

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

FIG. 10 is a diagram illustrating a gradation control method.

FIG. 11 is a diagram illustrating a sublimation transfer mechanism.

[Explanation of symbols]

11 ... Image data division circuit, 12 ... Thermal head control means, 13 ... Density-pulse application time conversion table, 14
... thermal head, 15 ... thermal transfer film selection means, 1
6 ... Thermal transfer film driving mechanism, 17 ... Applied voltage varying means.

Claims (13)

[Claims] 1. A thermal transfer film having a coloring material layer provided on one surface of a base material, and a thermal transfer sheet having a plurality of heating resistors and a thermal transfer sheet having a receiving layer provided on one surface of the base material. It is pressed against between the platen rollers and a pulse is applied to the thermal head for a time corresponding to the image data to energize
In an image recording method for reproducing gradation by controlling the amount of transfer of the color material from the color material layer of the heat transfer film to the receiving layer of the heat transfer sheet, at least two kinds of color material layers having different density characteristics are used. An image recording method characterized by reproducing gradation using a thermal transfer film. 2. The method according to claim 1, wherein the density characteristics of the two types of thermal transfer films are as follows with respect to applied energy.
An image recording method characterized by a density characteristic with a gentle rising and a density characteristic with a sharp rising and a large maximum density. 3. The image recording method according to claim 1, wherein the image data is divided into two or more, and the divided image data is printed with a thermal transfer film having different density characteristics. 4. A thermal transfer film having a coloring material layer provided on one surface of a base material, a thermal transfer sheet having a receiving layer provided on one surface of the base material, and a thermal head having a plurality of heating resistors. It is pressed against between the platen rollers and a pulse is applied to the thermal head for a time corresponding to the image data to energize
In an image recording method in which heat is generated and the amount of color material transferred from the color material layer of the heat transfer film to the receiving layer of the heat transfer sheet is controlled to reproduce gradation, one color is divided into a plurality of times and printing is performed each time. An image recording method characterized in that recording is performed by changing the applied voltage to the thermal head for each. 5. The method according to claim 4, wherein the voltage applied to the thermal head is changed so that the concentration characteristic with a gentle rise and the concentration characteristic with a steep rise and a large maximum concentration with respect to the applied energy An image recording method characterized in that colors are printed. 6. The image recording method according to claim 4, wherein the image data is divided into two or more, and the voltage applied to the thermal head is changed for each divided image data for printing. 7. An image recording method, wherein the method according to claim 1 or 4 is used in combination for printing. 8. A thermal head control means for inputting image data, a thermal head having a plurality of heating resistors, each heating resistor being selectively driven by the thermal head control means, and a platen roller. A thermal transfer film having a color material layer provided on one surface of the base material and a thermal transfer sheet having a receiving layer provided on one surface of the base material are pressed against each other between the thermal head and the platen roller, and In an image recording device that reproduces gradation by controlling the amount of color material transfer from the color material layer of the thermal transfer film to the receiving layer by applying a pulse for a time corresponding to the image data,
Further, a thermal transfer film selection means is provided, and the thermal head control means drives and controls the thermal transfer film selection means to select and use at least two types of thermal transfer films having color material layers having different density characteristics to reproduce gradation. An image recording apparatus characterized in that. 9. The apparatus according to claim 8, further comprising image data dividing means for dividing the image data into two or more, and the thermal head control means includes a thermal transfer film selecting means for each data divided by the image data dividing means. An image recording apparatus characterized in that a thermal transfer film having color material layers having different density characteristics is selected by driving control and printing is performed. 10. The apparatus according to claim 8, wherein the density characteristics of the two types of thermal transfer films are a density characteristic in which the rising is gentle with respect to the applied energy and a density characteristic in which the rising is steep and the maximum density is large. Characteristic image recording device. 11. A platen roller and a thermal head control means for inputting image data, a thermal head having a plurality of heating resistors, each heating resistor being selectively driven by the thermal head control means, and a platen roller. A thermal transfer film having a color material layer provided on one surface of the base material and a thermal transfer sheet having a receiving layer provided on one surface of the base material are pressed against each other between the thermal head and the platen roller, and In the image recording device that reproduces gradation by controlling the amount of color material transfer from the color material layer of the thermal transfer film to the receiving layer by applying a pulse for a time corresponding to the image data, An image recording apparatus characterized in that printing is performed a plurality of times and recording is performed by changing the voltage applied to the thermal head each time. 12. The apparatus according to claim 11, further comprising an image data division circuit for dividing the image data into two or more, and the thermal head control means applies the data divided by the image data division circuit to the thermal head. An image recording device characterized by printing by changing the voltage. 13. The apparatus according to claim 12, wherein the voltage applied to the thermal head has a voltage value that provides a concentration characteristic with a gentle rise to the applied energy and a concentration characteristic with a steep rise and a large maximum concentration. An image recording device characterized by being set.