JPH0329228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a printing method using an ink film for printers that can reproduce the gradation of printed matter well.

(b) Prior Art A typical printing method for printing a color image using a thermal dot printer or a wire dot printer is as follows.

A color image is divided into minute pixels and the Y, M, and C densities of each pixel are determined. Each pixel is subdivided into m×m dot matrices, and the number of printed dots (occupancy value) is determined for each color of Y, M, and C according to its density. This made it possible to express ^three colors (m x m + 1).

A printing method of a general color printer will be explained with reference to the drawings from FIG. 1 onwards.

In FIG. 1, color image data M (i, j) in column i and row j of display screen C is converted by data conversion means 1 into M' (i, J) data consisting of Y, M, and C data. Ru. The method of conversion is to first convert R,
G, B data for all pixels as shown below (1)
Convert to Y, M, C data using the formula.

dY=n-dB (0≦dB<n, 0≦dY<n) dM=n-dG (0≦dG<n, 0≦dM<n) dC=n-dR (0≦dR<n, 0≦ dC<n) ...(1) (However, n represents the number of expressible gradations of R, G, and B of pixel data, and dB, dG, and dR represent R, G, and B, respectively.
The proportion of B, dY, dM, and dC are Y, M, and C, respectively.
represents the percentage of ) After the above data conversion is performed, the occupancy value conversion means 2 converts the Y, M, and C data into matrix occupancy values. Now, for one pixel of image data, m
When the matrix of ×m dots is made to correspond, the second
As shown in the figure, a total of seven basic colors can be produced from the three primary colors of printing, Y, M, and C.
It is possible to express up to (m ² +1) ^three colors per pixel. That is, in a matrix of m×m dots, the dot occupancy values of Y, M, and C are
Since there are m ² +1 types, the theoretical number of expressed colors of (m ² +1) ³ colors can be obtained by combining each of Y, M, and C. Occupancy value conversion means 2 is Y, M, C
Convert each value of data to dot occupancy value,
(m ² +1) Set one of ^{the three} colors. The conversion method is performed using the following equation (2).

mY=(dY-1)×( ^m2+ 1)/n mm=(dM-1)×(m2 ⁺ 1)/n mC=(dC-1)×(m2 ⁺ 1)/n...(2) (However, numbers below the decimal point are rounded down.) Of the occupancy values obtained by the occupancy value conversion means 2 as described above, the occupancy values of M and C are further corrected by the correction means 3. As mentioned above, R,
Simply convert the G, B data into Y, M, C by using the above equation (1).
If the data is converted into data and used as three primary color data for direct printing, the printed colors tend to be very dark, especially in the blue family. Correction means 3
is to correct this deviation in the blue system, and the M data and C data are each multiplied by numerical values x and y of 1 or less, and the occupied values of M and C are corrected to smaller values. The corrected occupancy values mm' and mC' are obtained by the following equations (3).

mm'=mM×x (0<x<1.0) mC'=mC×y (0<y<1.0) ...(3) Y occupancy value obtained by the occupancy value conversion means 2 and correction means M occupancy value corrected in 3,
The number of C occupancy values is set in the m×m dot matrix memory MR arranged corresponding to each color of Y, M, and C using a predetermined method. m
The number of arrays in the ×m dot matrix memory corresponds to the total number of pixels, that is, (l1+1)×(l2+1). Matrix memory MY (i, j), MM
(i, j) and MC (i, j) respectively store the Y, M, and C occupancy values of the pixel in column i and row j. The occupancy value for each matrix memory is set in such a way that the bits to be set are distributed over the entire matrix area. The distribution method may be arbitrary, but
Preferably, the pattern is such that the bits set last time and the bits set this time face each other at a constant interval.

As described above, each bit is set sequentially for all matrix memories of the memory MR so as to be distributed over the entire matrix area according to the obtained occupancy value, and when this is completed, the memory
Buffer the MR data one line each for Y, M, and C.
Transfer to BY, BM, BC, and also Batsuhua BY,
The data transferred to BM and BC are sent to the thermal head in order. Thermal head is hot
When BY data is sent, the bit pattern stored in the buffer BY is thermally transferred using a Y-color transfer carbon film, and the buffer is also transferred.
When BM data is sent, a M color film is used to thermally transfer the bit pattern stored in the buffer BY. Further, when the data in the buffer BC is transferred, a C color film is used to thermally transfer the bit pattern stored in the buffer BC. When the bit patterns of the data stored in the buffers BY, BM, and BC are thermally transferred to the same positions, printing for one line is completed.
In this way, the total (l2 +
1) Printing for one screen is completed by completing x3 thermal transfers.

Now, in the configuration shown in Figure 1, n=256 (gradation),
If m = 4, dB = 255, dG = 0, and dR = 128, then according to the above equation (1), dY = 256 - 255 = 1 dM = 256 - 0 = 256 dC = 256 - 128 = 128. Also, according to the above formula (2), mY = (1-1) x (4 ² + 1) / 256 = 0 mM = (256-1) x (4 ² + 1) / 256 = 16 mC = (128-1) ×(4 ² +1)/256=8. Furthermore, in the above equation (3), x=0.7, y=
If it is 0.5, mM' = 16 x 0.7≒11 mC' = 8 x 0.5 = 4. Therefore, the respective occupancy values of Y, M, and C at a certain position are mY=0 mM'=11 mC'=4.

If the order in which bits are set in the matrix memory is as shown in FIG. 3, the respective occupancy patterns when the matrix occupancy values are 0 to 16 are as shown in FIG. As is clear from this figure, the change in the occupancy pattern as the matrix occupancy value increases is not a change in which the bits are concentrated in one place, but a change in which the bits are dispersed over the entire area of the matrix. For example, when the matrix occupancy value increases from 1 to 2, the bits that are newly set at the time of the increase are located away from the surroundings when the occupancy value is 1. Similarly, the bits that are newly set when the occupancy value changes from 3 to 4 are located away from the bits that were set when the occupancy value increases from 2 to 3. By sequentially setting each bit in the matrix memory according to the occupancy value so that it is distributed over the entire matrix area, the constituent colors when printing for each of Y, M, and C are finished are determined as follows. It can be made more natural. Figure 5 shows m=4
In the case, the occupancy value of Y is 0 and the occupancy value of M is
16 shows the composite state of the matrix when the occupancy value of C is 8 (the occupancy values of M and C are corrected values).

Note that when m=2, the order in which bits are set in the matrix memory can be defined as shown in FIG. 6, for example. In this case, the occupancy pattern for each of the matrix occupancy values 0 to 4 is as shown in FIG. In addition, in the case of m=2, for example, when the occupation value of Y is 0, the occupation value of M is 4, and the occupation value of C is 2 (the M and C occupation values are the values after correction), the composite state of the matrix is The result is as shown in FIG.

(c) Problems to be solved by the invention By the way, in the method of determining the number of dots based on shading, when expressing pale colors or intermediate colors, the distance between dots becomes wide, and one dot falls on the other. There was a flaw that stood out and made it impossible to produce beautiful prints.

In addition, the above-mentioned method can only express m×m shading for each color (Y, M, C), which is insufficient for expressing subtle intermediate tones.

An object of the present invention is to provide a printing method using an ink film for printers that can solve the above problems by adjusting the ink density.

(d) Means for Solving the Problems The printing method using the ink film for printers of the present invention includes a full-tone area coated with or impregnated with high-concentration ink of a specific color and a full-tone area coated with or impregnated with low-concentration ink of the specific color. Using an ink film for a printer characterized by having a halftone part, one pixel is composed of a dot matrix, and the density of one pixel is set to a maximum value equal to or more than the number of dots in one pixel. The number of dots of the low density ink is set, and when this number of dots is less than the number of dots of one pixel, printing is performed using the halftone part with that number of dots, and the number of dots of the low density ink is set as the number of dots of one pixel. When the number exceeds the number, printing is performed using the full tone portion at least for the number exceeding the number.

(e) Effect The ink film for a printer used in this invention has a part coated/impregnated with high-concentration ink (full tone part) and a part coated/impregnated with low-concentration ink for the color to be printed (specific color). (halftone part). Ink film (ink ribbon or ink sheet) for thermal printing is a plastic film coated with ink, and ink film used for wire dot printers is a fiber film impregnated with ink. The one given is used. As mentioned above, the ink film may be a ribbon (tape) or a sheet.

In the present invention, using the ink film for printers described above, the density of a pixel is first set by the number of dots of low-density ink, and when a pixel cannot be filled with dots of low-density ink, printing is performed in a halftone area, and the density of a pixel is set using the number of dots of low-density ink. When the density is insufficient even after filling with dots, the missing dots are replaced with high density ink. This makes it possible to reproduce multiple levels of gradation even with a small number of dots, and even in intermediate tones, pixels can be filled with halftone dots, creating a fine-grained image without unevenness. can be formed.

(f) Example FIG. 9 shows an ink film (ink sheet) which is an example of the present invention. The ink film 4 is coated with transfer ink of each color in a periodic pattern, and one period (one set) is designated as Y (Yellow).
Halftone section, fulltone section, M (Magenta)
It consists of a halftone section, a fulltone section, a C (Cyan) halftone section, and a fulltone section. Multiple transfer can be performed up to six times by sequentially facing each ink portion to the same line of the recording paper 5.

Printing equipment that uses this ink film
A multiplication means for doubling the occupied value is arranged before the memory MR shown in FIG. 1, and the matrix memory corresponding to each pixel of the memory MR has a two-frame structure. Then, Y obtained by the occupancy value conversion means 2
The occupancy value of , and the occupancy value of M and C finally obtained by the correction means 3 are each doubled by the multiplication means, and a two-frame structure matrix corresponding to that pixel is calculated according to the doubled values. The bits are set to be distributed sequentially in the block memory.
In this case, the first frame's matrix memory is set, and if there is still a surplus of occupied values even after all bits of that frame have been set, the remaining number is set in the second frame's matrix memory. The bits are set. By performing such processing, each bit of the matrix memory becomes (0, 0), (0, 1), (1,
1) (the first value represents the storage state of the first frame, and the next value represents the storage state of the second frame). That is, three states are stored for each bit. Therefore, a control unit (not shown) judges this storage state, and when it is (0, 0), no transfer is performed, when (0, 1), the halftone film is positioned at the multiple transfer position and transferred, and (1, 1), the halftone film is positioned at the multiple transfer position and transferred. ), the full tone film is positioned at the multiple transfer position and transferred. By doing this, when the occupancy value of the matrix memory is small, halftone film is used to print, so it is possible to reduce the tendency for each dot to stand out.
It has the advantage of not looking dirty.

Further, if the matrix memory MR is made into a larger multiple frame structure and the occupied value is tripled or more by the multiplication means, it is possible to have four or more types of storage states corresponding to each bit. In this case, by changing the combination of halftone film and fulltone film used depending on each storage state, it is possible to prevent dots from becoming noticeable and to increase the variety of color tones. For example, if the matrix occupancy value is tripled and the frame structure of the matrix memory is set to 3 frames (0, 0,
0), do not print, and (0, 0, 1), print using halftone film,
(0, 1, 1), print using full tone film, (1, 1, 1), print using halftone film, and then print using full tone film (including colorless). ) It becomes possible to print in four levels of color tones.

(g) Effects of the Invention According to the printing method using the ink film for printers of this invention, the pixel density is set by the number of dots of low-density ink, and the dot pixels of the low-density ink are initially filled with the number of dots. If the result is within 1 pixel, print in the halftone area, and print 1 pixel.
If the number of pixels exceeds the number of pixels, the excess number of dots is used to print in a full tone section, so even with a small number of dots, it is possible to reproduce multiple levels of gradation, and even in intermediate tones, halftones can be printed. Pixels can be filled with dots. Furthermore, when the number of dots exceeds a certain level, a full tone portion is used, so high density printing can be performed. For this reason, the gradation ranges from low density to high density in many stages, making it possible to form a fine-grained image with less unevenness. In addition, when printing pixels with low density (the number of dots indicating density is less than the number of dots constituting the pixel), printing can be done using only the halftone part and there is no need to use the fulltone part.
Printing speed can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a general color printer. FIG. 2 is a diagram showing seven basic colors that can be expressed using the three printing primary colors Y, M, and C. FIG. 3 is a diagram showing the order in which bits are set in a matrix when m=4, and FIG. 4 is an occupancy pattern diagram for dot occupancy values in accordance with that order. FIG. 5 is a diagram showing an example of a composite state of matrices when n=4. Also the 6th
The figure shows the order in which bits are set in the matrix memory when m=2. FIG. FIG. 3 is a diagram showing an example of a matrix synthesis state in the case of FIG. FIG. 9 is a diagram showing a transfer ink film according to an embodiment of the present invention. 4...Ink film.

Claims (1)

[Scope of Claims] 1. Using an ink film for a printer having a full-tone area coated with or impregnated with a high-density ink of a specific color and a half-tone area coated with or impregnated with a low-density ink of the specific color, one pixel is obtained. is composed of a dot matrix, and the density of one pixel is set to the number of dots of the low-density ink with the maximum value being greater than or equal to the number of dots in one pixel, and when this number of dots is less than or equal to the number of dots in one pixel. The method is characterized in that printing is performed using the halftone section using the number of dots, and when the number of dots of the low density ink exceeds the number of dots of one pixel, printing is performed using the fulltone section using at least the exceeding number of dots. A printing method using an ink film for a printer.