JPH0596765A - Thermal transfer type image recording method and its apparatus - Google Patents

Abstract

PURPOSE:To improve reproducibility of a gray scale by improving the efficiency of heating of a thermal head and shortening electroconducting time thereof in thermal transfer type image recording. CONSTITUTION:Density data DR, DG, DB obtained from a luminance-density conversion circuit 12 are inputted to a UCR conversion circuit 14. The UCR conversion circuit 14 performs under color removal of the density data DR, DG, DB and decomposes them into the density K of a black component and three primary color density data DR', DG', DB' of the residual content after removing the black component. A density-electroconducting time conversion circuit 18 converts density information of each density data DY, DM, DC, K to electroconducting time data CY, CM, CC, CK expressing electroconducting time (thermal transfer time) of heating element per each pixel, and supplies each electroconducting time data CY, CM, CC, CK in the order of Y, M, C, BK by each one frame to a thermal head 20 at a specific cycle following photographic timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer type image recording method and apparatus for producing a color hard copy from a color image signal.

[0002]

2. Description of the Related Art In an image display device such as a CRT display, color reproduction is performed by an additive method using three colors of R (red), G (green), and B (blue), whereas an image recording device such as a color video printer is used. In the apparatus, color reproduction is performed by a subtractive color method using three colors of Y (yellow), M (magenta), and C (cyan). Therefore, to make a color hard copy from a color video signal, the RGB color video signal is converted into YMC image data, and images corresponding to the Y, M, and C image data are superimposed and printed. Good.

In the conventional thermal transfer type image recording apparatus,
Three ink sheets coated with sublimation dyes for three colors of Y, M, and C for each sheet, or one ink sheet coated with sublimation dyes for three colors of Y, M, and C alternately and alternately in a frame sequence. By using an ink sheet and switching the ink sheet for each color according to the image data of each color of Y, M, and C to heat the thermal head, the image of three colors of Y, M, and C is superimposed on the recording paper. It was recorded and a full color hard copy was made by mixing and subtracting these three colors. In addition, Y, M, and C color sublimation dyes generally have turbid components, and the color purity decreases when mixed, so that a RGB color image signal or Y, M, and C image data has a 3 × 3 matrix. The color reproducibility was improved by applying a color masking process such as with.

[0004]

In the conventional thermal transfer image recording apparatus as described above, the images of three colors of Y, M, and C are recorded in an overlapping manner to reduce the color of the gray or black component by subtractive mixing. , But according to this method,
The total energization time of the thermal head is long, the total amount of heat generated is large, which is inefficient in terms of power consumption, requires a large head cooling device, and further shortens the life of the thermal head. .. Further, depending on the YMC subtractive color mixing with the sublimation dye of a general ink sheet, it is difficult to accurately reproduce the gray scale even if the color masking process is applied.

The present invention has been made in view of the above problems, and a thermal transfer type image recording method and apparatus for improving efficiency and shortening heat generation / energization time of a thermal head and improving gray scale reproducibility. The purpose is to provide.

[0006]

In order to achieve the above object, the method of the present invention uses a thermal head to generate heat in response to a color image signal, and the heat energy generates recording from an ink sheet coated with a sublimable dye. In a thermal transfer type image recording method in which a dye is transferred onto a paper to record a full-color image on a recording paper, a color video signal is color-separated into density data of four colors of yellow, magenta, cyan and black, According to the density data of the four colors, the sublimation dye of the ink sheet is switched for each color to perform a four-color overlapping printing.

Further, in the apparatus of the present invention, the thermal head is caused to generate heat in response to a color image signal, and the heat energy causes the dye to be transferred onto the recording paper from the ink sheet coated with the sublimable dye, thereby forming a full-color image on the recording paper. In a thermal transfer type image recording apparatus for recording an image, a means for converting a color video signal into density data of four colors of yellow, magenta, cyan, and black, and an ink sheet of an ink sheet according to the density data of the four colors. The sublimable dye is switched for each color, and a means for performing four-color overlapping printing is provided.

[0008]

According to the present invention, when a hard copy is made from a color video signal, for example, undercolor removal (UCR) processing is performed, and the density data DY, DM, of four colors of RGB signals of yellow, magenta, cyan, and black are added. Color separation is performed into DC and K, and the sublimable dye of the ink sheet is switched for each color according to the density data of the four colors, and four-color overlapping printing is performed. As a result, all the black components of the hard copy image are recorded as an image transferred onto the recording paper from the black sublimation dye of the ink sheet according to the density data K of the black component, and the color components other than the black component are YMC.
In accordance with the density data DY, DM and DC of the ink sheet, it is recorded as an image transferred from the yellow, magenta and cyan sublimation dyes of the ink sheet onto the recording paper.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a circuit configuration of a main part of a thermal transfer image recording apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view showing a mechanism of a printing section of the thermal transfer image recording apparatus of the embodiment, FIG. Is a top view showing the ink surface of the ink sheet used in the thermal transfer image recording apparatus of the embodiment, and FIG.
FIG. 5 is a block diagram showing a configuration example of the CR circuit and FIG. 5 is a diagram showing an operation of the UCR circuit of the embodiment.

In FIG. 1, an inverse γ conversion circuit 10 receives a primary color red signal R, a primary color green signal G, and a primary color blue signal B as digital signals, and this circuit 10 cancels the γ correction of a television system. The digital primary color signals R, G, B output from the inverse .gamma. Conversion circuit 10 are input to the luminance-density conversion circuit 12, and the relational expression of the following equation is calculated in this circuit 12 to obtain the optical density data DR, DG. , Converted to DB. DR = -logR 'DG = -logG' ... DB = -logB 'The density data DR, D obtained from the brightness-density conversion circuit 12.
G and DB are input to the UCR conversion circuit 14.

In the UCR conversion circuit 14, the density data DR,
Under Color Removal is performed on DG and DB, and the density data K of the black component and the three primary color density data DR ', DG', and DB 'remaining after the black component is removed are decomposed.

The three primary color density data DR ', DG', DB 'and the black component density data K output from the UCR conversion circuit 14 are input to the color correction circuit 16, where the density data DB', DG ', DR 'is subjected to color correction such as color masking processing, and is output as density data DY, DM, DC of yellow (Y), magenta (M), and cyan (C). As a result, the density / energization time conversion circuit 18 causes the color correction circuit 16 to output the density data DY, DM,
The density data K of DC and the black component are given.

In the density-energization time conversion circuit 18, the density information of each density data DY, DM, DC, K represents the energization time (thermal transfer time) of the heating resistor element for each pixel, and the energization time data CY, CM, CC. , CK and Y, M,
Each energization time data CY, CM, in the order of C, BK (black)
CC and CK are supplied to the thermal head 20 at a predetermined cycle according to the printing timing.

The thermal head 20 has a large number (for example, 5).
With a line head having 12 heating element elements arranged in a line, each heating element element is energized for a time corresponding to the value of the energization time data corresponding to it, and the amount of heat energy proportional to the energization time is generated. To do.

In FIG. 2, each heating resistance element of the thermal head 20 is pressed against the recording paper 24 via the ink sheet 22 coated with the sublimation dye during the printing operation.
Therefore, the dye of the ink sheet 22 is sublimated (vaporized) by the heat energy from each heating resistance element and the recording paper 2
Pixels which have been transferred and fixed on the recording medium 4 and have a predetermined density gradation are recorded. In the figure, 26 is a platen, 28 and 30 are supply rolls and take-up rolls of the ink sheet 22, 32 is a capstan, 34 is a pinch roller, and 36 is a paper cueing sensor. Such a printing operation for one line is repeated for a large number (for example, 600 printing lines) by printing scanning, and as a result, an image for one color is recorded on the recording paper 24. By repeating such a printing operation for one frame for each color of Y, M, C, and BK, a full-color image in which these four color images are superimposed is recorded on the recording paper 24.

As shown in FIG. 3, the ink surface of the ink ribbon 22 is formed by applying sublimation dyes of four colors of Y, M, C, and BK one frame at a time in sequence. For example, when the Y image is printed, the Y ink surface comes between the thermal head 20 and the recording paper 24, and when the M image is printed next, the M ink surface is recorded with the thermal head 20. The ink sheet 22 is placed between the sheets of paper 24 so that the energization time data CY, CM, CC, C for the thermal head 20 is provided.
The paper is sent in synchronization with the input of K and the recording paper 24.

As described above, in this embodiment, undercolor removal (UC) is performed when a hard copy is made from a color image signal obtained from a television receiver, a video tape recorder or the like.
R) processing to convert RGB signals into four color density data D
Color separation is performed into Y, DM, DC, and K, and the sublimation dye of the ink sheet 22 is switched for each color according to the density data of the four colors, and four-color overlapping printing is performed. As a result, all the black components of the hard copy image are converted to the black sublimation dye BK of the ink sheet 22 according to the density data K of the black component.
The color components other than the black component are recorded as an image transferred onto the recording paper 24 by the YMC density data DY, D.
According to M, DC, the image is recorded as an image transferred onto the recording paper 24 from the yellow, magenta, cyan sublimation dyes Y, M, C of the ink sheet 22.

According to such a thermal transfer system, in order to reproduce a gray or black color, the thermal head 20 is set to 1 by using the black sublimable dye BK of the ink sheet 22.
Since it is only necessary to generate heat twice, Y, M, C
It is possible to reduce the total ink (dye) consumption amount as compared with the method of reproducing the gray or black color by superimposing the three colors described above, and thus to reduce the total heat generation amount and the total energization time of the thermal head 20. it can. Further, since a gray color or a black color is reproduced by the black sublimation dye BK of a single color, the gray scale can be accurately reproduced.

FIG. 4 is a UCR conversion circuit 1 in this embodiment.
4 shows the configuration of No. 4. FIG. 5 shows a ratio (one example) of the values of the respective density data handled by the UCR conversion circuit 14. In FIG. 4, the UCR conversion circuit 14 is composed of a K _MAX calculation circuit 40, a K calculation circuit 42, and a K subtraction circuit 44. The K _MAX calculation circuit 40 calculates the following equation to extract the maximum black component K that can be extracted from the input density data DR, DG, DB of the three primary colors.
_{Find MAX} . K _MAX = MAX (DB × DG × DR) ... The K operation circuit 42 calculates the following equation for the maximum black component K _MAX obtained by the K _MAX operation circuit 40, and obtains the black component K to be actually removed. Ask. K = ω (K _MAX −Kth) ... Here, ω is a black coefficient (0 to 1), and Kth is a black threshold level (K _MAX > Kth). The K subtraction circuit 44 subtracts the black component K from the K operation circuit 42 from the input density data DR, DG, DB of the three primary colors according to the following equation to remove the undercolor removed three primary color density data DR ', Find DG 'and DB'. DR '= DR-.alpha.RK DG' = DG-.alpha.GK ... DB '= DB-.alpha.BK where .alpha.R, .alpha.G, .alpha.B are subtraction coefficients for balancing the undercolor removal effect for the three primary colors RGB or YMC. Is. These three primary color density data DR ', DG', and DB 'are YMC of Y, M, and C sublimable dyes of the ink sheet 22 are pure YMC.
If it is a color, Y, M, and C density data may be used as in the following equation. DR '= DC DG' = DM ... DB '= DY

However, the actual Y of the ink sheet 22,
Since the M and C sublimable dyes contain a turbid component, printing with the density data DR ', DG', and DB 'still results in a recorded image with low color reproducibility. Therefore, in this image recording apparatus, the colors corrected by the color correction circuit 16 such as color masking are designated as DY, DM, and DC.

[0021]

As described above, according to the present invention,
Since the color of gray or black can be reproduced only by heating the thermal head once against the black sublimable dye of the ink sheet, it is possible to reduce the total consumption of the sublimable dye and reduce the total amount of the thermal head. The amount of heat generation and the total energization time can be reduced. Therefore,
The cooling device for the thermal head can be downsized, and the life of the thermal head can be extended. Further, since a gray color or a black color is reproduced with a single color black sublimation dye, a gray scale can be accurately reproduced and a clear recorded image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a main part of a thermal transfer image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mechanism of a printing unit of the thermal transfer image recording apparatus of the embodiment.

FIG. 3 is a top view showing an ink surface of an ink sheet used in the thermal transfer image recording apparatus of the embodiment.

FIG. 4 is a block diagram showing a configuration example of a UCR circuit according to an embodiment.

FIG. 5 is a diagram showing an operation of the UCR circuit of the embodiment.

[Explanation of symbols]

 10 Inverse γ Conversion Circuit 12 Luminance-Density Conversion Circuit 14 UCR Conversion Circuit 16 Color Correction Circuit 18 Density-Duration Time Conversion Circuit 20 Thermal Head 22 Ink Sheet 24 Recording Paper

Claims (2)

[Claims] 1. A thermal head is caused to generate heat in response to a color image signal, and the heat energy causes the dye to be transferred onto a recording paper from an ink sheet coated with a sublimable dye so that a full-color image is recorded on the recording paper. In the thermal transfer type image recording method described above, the color video signal is color-separated into four color density data of yellow, magenta, cyan and black, and the sublimation dye of the ink sheet is separated for each color according to the density data of the four colors. An image recording method, which is characterized in that printing is performed by switching four colors. 2. A thermal head is caused to generate heat in accordance with a color image signal, and the heat energy causes the dye to be transferred onto a recording paper from an ink sheet coated with a sublimable dye, thereby recording a full-color image on the recording paper. In the thermal transfer type image recording device, a means for converting a color video signal into density data of four colors of yellow, magenta, cyan and black, and a sublimation dye of the ink sheet for each color according to the density data of the four colors. An image recording apparatus comprising: a unit for switching over for each four-color printing.