JPS6124371A - Area gradation recording method - Google Patents

Abstract

PURPOSE:To realize the number of gradations more than the number of nXm elements prepared for one picture element by applying ink transfer at a position shifted by 1/2 of the pitch width of the arrangement of longitudinal elements so as to form an ink coloring part having nearly 1/2 of one element area. CONSTITUTION:A thermal head 1 where heat resistive elements 2 are arranged laterally is used and the head 1 is driven on the 1st row the same as a conventional system. Electricity is applied only to the 1st element 2 on the 1st row in the elements 2 for picture recording with intermediate density of the gradations 1, 2, the result is printed as (a), then the recording paper 4 and an ink sheet 5 are fed in longitudinal direction A by 1/2 of the longitudinal interval (d) of the arranged elements, power is applied only to the 1st element 2 similarly and a pattern is formed as shown in figure (b). In this case, since the ink of the 1st element is transferred already by the head before movement, the half area of one element is realized. Similarly the head 1 is driven while being fed sequentially by 1/2 pitch in longitudinal direction. Since no electicity is applied to the element further, a pattern shown in figure (c) is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an area gradation recording method that can increase the number of gradation levels and improve image quality without reducing resolution.

[Technical background of the invention and its problems] In recent years, the information-related industry has made remarkable progress, and along with this, there has been a need for printers that can record characters, figures, etc. on recording paper. As the printer in this case, a thermofusion type thermal recording type printer is widely used.

In the heat-melting type thermal recording method, an ink sheet made by applying heat-melting solid ink to the surface of paper or IJ Norasic film is layered with recording paper, and a thermal head is used to press the recording paper. By heating,
The ink sheet melts the solid ink on the sheet and transfers it to the recording paper. This recording method does not generate noise because it is a non-invacuum recording method, has a fast recording speed, combines with the development of a thermal head to obtain high resolution, and unlike the inkjet recording method, the recording head There is no need to worry about troubles caused by clogging, and almost no maintenance is required.Since pigments can be used to remove the color of recording ink, it has good light resistance and storage stability. It has many advantages over other printers, such as the ability to easily record in color by using Color Ink Sea 1, which has 300 colors of red and cyan, and overcoating each color. There is. However, on the other hand, by changing the power applied to the thermal head, the heat generation W changes, and by changing the suspension of ink transferred to the recording paper, the recording density can be adjusted from 1 to [
It has the disadvantage of not being able to do 1-ru J. (For example, the ink transfer interval is halved and the cutting transfer 1) is recorded 1.
It is almost impossible to record at half the density of 5 degrees. ) That is, the heat-melting type thermal transfer recording system is a binary recording system that can only perform either ink pre-transfer or ink all-transfer. Therefore, it is not possible to record a halftone image with 81 shades of gray as it is.

Therefore, in order to record a halftone image using the heat-fusion type thermal transfer recording method, a gradation recording method called the density pattern method, which is a type of area gradation method, is used. The density pattern method divides one pixel into matrix elements consisting of several elements, and changes the number of matrix elements to be filled by transferring ink according to the density of the pixel. In other words, the matrix corresponding to one pixel is This is a method of expressing different shading by changing the area of the transferred ink colored area.

This gradation recording method is convenient because a conventional binary recording ink sheet can be used as is and it can be applied not only to monochrome but also color gradation recording.

FIG. 6 shows a density pattern in which one pixel is divided into a 4×4 matrix and the density of each pixel is expressed by 16 levels of gradation from O. In the figure, depending on the arrangement of 71-lix elements colored by ink transfer, halftone type,
There are spiral type and Bayer type shown in the figure.

However, with this method, the upper limit of the number of gradations is limited by the number of elements in the matrix, so if you increase the number of elements in the matrix in order to obtain a high number of gradations, the pixel size will increase and the resolution will decrease. It has the disadvantage of being

By the way, as a conventional example related to the present invention, there is
-, No. 99746 discloses a print head driving system. This uses nxm recording elements vertically and horizontally to record information such as characters, and the resolution is n
Since the number of elements is limited to xm, by moving the print head by 1/2' of the bit and printing again, a resolution closer to the actual information can be achieved. WAF! It does not solve the problem of recording a certain halftone image of A.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and uses a matrix of the same size as the conventional density pattern method to significantly increase the number of gradation levels without reducing the resolution. It is an object of the present invention to provide an area gradation recording method that can more faithfully reproduce shading.

[Summary of the Invention] The present invention uses a matrix consisting of nxm elements and records by changing the number of elements to which ink is transferred and colored depending on the density of each pixel. Using the area gradation recording method J3, a colored part with an area approximately 1/2 of the area of one element is formed by recording by shifting the pitch of the matrix elements in the vertical direction by 1/2 the pitch of the matrix elements. This makes it possible to significantly increase the number of gradations without increasing the number of matrix elements.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to the drawings.

Figures 1 to 3 relate to the first embodiment of the present invention.
The figure shows a colored pattern formed according to one embodiment,
FIG. 2 shows the recording system used in the first embodiment, and FIG. 3 shows how the recording system of FIG. 1 is used to record.

The thermal head 1 used in the first embodiment of the present invention is
As shown in FIG. 2, heating resistor elements 2. ..., 2 are arranged. This normal head 1 has an ink sheet in which a recording paper 4 and an ink sheet 5 are stacked on top of a platen roller 3.
In this case, the heat-generating resistive elements 2, . Due to this heat generation, the ink on the ink sheet 5 in the area where the heating resistor element 2 is in close contact with is melted, and the molten ink is transferred onto the recording paper 4.

In this embodiment, elements of colored parts to which ink has been transferred and elements that have not been transferred are formed in a matrix of 4 x 4 or 4 columns x 4 rows depending on the density of each pixel. A case will be described in which recording is performed in gradations (corresponding to I1 degrees) using a colored pattern. For example, in the coloring pattern (It degree pattern) shown in FIG. First, in the first row, the thermal head 1 is driven as in the conventional case. Here, in the heating resistive elements 2', 2.2.2 for recording pixels with a density intermediate between gradations 1 and 2, only the first heating resistive element 2 out of the four horizontal ones in the first row is used. When electricity is applied to the area, the ink in that area is transferred and printed as shown in FIG. 3('a). Next, for example, a line feed mechanism (not shown) is activated, and the recording paper 4 and ink sheet 5 side are moved in the line feed direction by the rotation of the platen roller 3 in the vertical direction in the array elements forming the matrix with respect to the thermal head 1. is sent by 1/2 pitch of the interval d. (The above 1/2 pitch is approximately equal to the vertical width (length) of the matrix element or heating resistor element.) This state is shown by broken lines in FIG. 2(a), assuming that the thermal head 1 side is moved for convenience. . Similarly, only the first heating resistor element 2.2.2.2 for recording the 1a degree pixel is energized and the ink is transferred, resulting in the result shown in FIG. 3(b). An ink transfer pattern is formed in this manner. In this case, the ink of the first element part has already been transferred by the thermal head 1 before the movement and remains on the ink sheet 5 part (there is no ink, so after the thermal head 1 moves by 1/2 pitch, the same heating resistor element 2 generates heat). Even if the ink is transferred, the upper half of that part overlaps the previous ink sheet 5, and the ink in this overlapped part is not transferred, but only the lower half is transferred, forming the image shown in FIG. 3(b). In other words, by this 1/2 pitch movement, when the areas of the colored parts of the ink to be transferred are transferred so as not to overlap, it is possible to achieve an area of 1/2 of the area of one element.

In the same way, operate the line feed mechanism to move the line 1/2 in the vertical direction.
The recording paper 4 and the ink sheets 1 to 5 are sequentially fed by two pitches, and the thermal head 1 is driven respectively. The heating resistor elements 2, 2, and 2.2, which represent pixels whose density corresponds to the intermediate level between gradations 1 and 2, are not energized from now on, and the third
A uniformly colored J (turn) as shown in Fig. 3(C) is formed.The area of the colored part of the colored pattern shown in Fig. 3(C) is the area of the colored part of 1 dot (1 element). S is written as 1.58, and according to the conventional method of expressing gradation levels, it is possible to express 1.5 gradations.In other words, what was conventionally expressed roughly as gradation level 1 or 2, With a finer level width, the density of each pixel can be more faithfully reproduced.

In this way, it is possible to achieve half the area of the conventional coloring section, so the number of gradation levels can be significantly increased (approximately doubled). FIG. 1 shows an example of a coloring pattern that expresses gray and shade using 4×4 matrix elements according to the first embodiment. In this colored pattern, the gradation levels are 1.3°, 5.7°, and 5.7°. ...29. ．． If the IPig level is an odd number such as 31, the number of recording dots (colored dots) is an integral multiple of one element, while if the IPig level is an even number, one half of the number of recording dots is included.

This area gradation recording method uses the same pixel size as the conventional colored Bakun expression method and can nearly double the number of gradations without lowering the resolution.

When feeding the platen roller 3 as the line feeding mechanism in this embodiment (), high precision 1u(' can be achieved by controlling the rotational speed of the roller and the rotation angle of the pulse t).
゛Saru. Although it is possible to move the thermal head 1 side instead of the recording paper 4 side, it is practical to move it on the recording paper 4 side.

In addition, in the book (above), it is assumed that the pixels are sequentially shifted by 1/2 pitch from the first row, and that the first to seventh rows are scanned alternately to form one pixel. In some cases, the colored pattern shown in FIG. 1 can be scanned in an interlaced manner, instead of every τ1/2 pitch. That is,
From the first row to the third row, 1/2 pitch is required, and then scanning may be performed by 1 pitch at a time, and then shifted by 1/2 pitch again.

FIG. 4 shows a second embodiment in which a colored pattern different from that in FIG. 1 is formed. In this case, the position where the 1/2S colored portion is formed is always below the gradation level 1. By doing this, the first to third rows can be scanned at 1/2 pitch, and thereafter all can be scanned every 1 pixel, so the number of scans per pixel can be considerably reduced, and the recording speed can be increased. can.

Next, a color gradation recording method will be described as a third embodiment based on the present invention.

When performing color gradation recording, as shown in Figure 5,
For example, an ink sheet 7 on which inks of three colors are applied in series in the order of yellow, magenta, and cyan is used. Using this ink sheet 1-7, a desired color can be reproduced by applying two or three colors of ink overlappingly and subtracting color mixing.

For example, when printing in red at an arbitrary gradation level P (a natural number of 1≦P≦31) among the 31 gradations shown in FIG. Then, by moving the ink sheet 7, a density pattern of gradation level P is similarly recorded with magenta ink on top of the colored pattern. In this way, recording at red gradation level P can be performed. Even when performing gradation recording of other colors, by transferring two or three colors of ink, it is possible to perform gradation recording in the desired color. Incidentally, the order of the colors of the ink sheet 1- is not limited to that shown in FIG. 5.

If we use a matrix in which the above-mentioned vertical and horizontal elements are arranged in a 4 x 4 arrangement, it is possible to achieve 31 gradations with a single color, so we can record gradations with 31 cubed, or 29,791 types of colors, which is better than before. It also has the advantage of being able to record colors that reflect colors and shading much closer to the real thing.

In addition, in the above explanation, -( means the heating resistor cable 2°...
. The same can be applied to the multihead. One normal head formed by roughly arranging NXM heating resistive elements may also be used. In this case, if horizontal scanning is required, for example, 1) the multi-head may be scanned in the horizontal direction in the same way as in normal scanning. In the vertical direction, according to the recording method of the present invention, ink is transferred at a position relatively shifted by approximately 1/2 pitch of the vertical interval of the constraining elements in the matrix corresponding to one pixel. Color recording by ink transfer at the boundary between the six color areas and the blank area can be performed at least once for a matrix corresponding to one pixel.

For example, as shown in FIG. 2(a), second thermal heads are arranged parallel to the thermal head 1 at predetermined intervals in the line feeding direction A, and these intervals are defined as longitudinal elements. of the array pitch d (that is, L = (1/2 +
7) d: where: natural number) is 1-. However, the second
By closing the thermal head of
A colored portion having an area of 1/2S may be formed by transferring ink at a position shifted in pitch.

It should be noted that the present invention is not limited to a heat-melting type thermal transfer recording type, but can be similarly applied to an impact dot type or the like.

"Effects of the Invention" - As described, according to the present invention, ink in U n X m matrix elements is transferred according to the 14 degrees of each pixel, and the area of the colored portion to be formed is changed and transferred. In the area gradation recording method for recording, the pitch width of the 7 matrix elements in the vertical direction is 1/2 [Because the transfer recording is performed with a shift, the minimum area of the colored part is 1/2 of the conventional one. The number of gradation levels can be approximately doubled and colors and shading can be reproduced more faithfully without reducing the M image resolution.

1゜Simple explanation of the drawings Fig. 1 to Fig. 3 relate to the first embodiment of the present invention, and in the case of Fig. 1 (, 1 according to the present invention:), it is realized by a 4 × 4 matrix. Figure 2 shows the outline of the recording system used in the first embodiment. An explanatory diagram showing how the thermal head performs transfer recording, FIG. 3B is a side view thereof, and FIG. FIG. 4 is a diagram showing a 31-gradation coloring pattern formed by reducing the number of times the legal head is driven, according to the second embodiment of the present invention, and FIG. 5 is used in the third embodiment of the present invention. FIG. 6 is a diagram illustrating an example of the ink sheet 1 for color recording, and FIG. 6 is a diagram showing a coloring pattern for area gradation recording when a conventional method is followed.

1...Thermal head 2...Heating resistor element 3.
...Platen roller 4...Recording paper 5.7...Ink sheet Fig. 1 Fig. 2 (b) Fig. 3 (0) (C) Fig. 5 1J4 [

Claims (1)

[Claims] In order to record the gradation of each pixel, each pixel is
A matrix consisting of ×m elements is prepared, and the number of elements to which ink is transferred in the matrix, that is, the area of the ink colored part in the matrix, is recorded in gradation according to the density of each pixel. In the adjustment recording method, by transferring ink at a position shifted by 1/2 of the pitch width of the arrangement of the elements in the vertical direction, it is possible to form an ink-colored portion approximately 1/2 of the area of one element. An area gradation recording method characterized in that by doing so, it is possible to realize a number of gradations greater than the number of n×m elements.