JPH10278327A - Image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation in the substantial appearance of color even when the overlap of color is shifted in the main scanning direction. SOLUTION: In the image recording method for recording dots in zigzag in the direction parallel with the arranging direction of heating elements (main scanning direction) and the direction perpendicular thereto (subscanning direction) using a head arranged with a plurality of heating elements at a constant interval, a non-recording part from where the dot is removed is applied with energy weak enough not to record the dot and the energy is varied between the opposite sides of a recording dot which is shifted in the direction applied with weak energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image recording method for a printer using a head, such as a thermal head, in which a plurality of thermal elements are arranged at regular intervals.

[0002]

2. Description of the Related Art In a thermal printer, by changing the time for energizing a thermal element, one is printed on a recording paper.
An image recording method for obtaining a gradation image by changing the area of a recording dot to be recorded as a dot has been proposed.

However, in this recording method, recording is performed while moving the recording paper for each color in the sub-scanning direction (direction orthogonal to the direction in which the thermal elements are arranged), so that pixel positions for each color in the sub-scanning direction do not overlap. In some cases. When such pixel displacement (registration displacement) occurs, moire occurs, or the color tone changes, resulting in a color different from the original image.

As a technique for eliminating such a change in color tone due to moiré or misregistration, there is an image recording method described in Japanese Patent Application Laid-Open No. 7-31677. In this image recording method, an array pattern having a desired resolution is formed for each color in the sub-scanning direction by changing a dot array cycle in the sub-scanning direction at a desired magnification, and a multi-color image is formed by overlapping different array patterns for each color. As a result, there is no bias in how colors overlap, and color moiré is suppressed.

[0005]

However, in the above-described image recording method, the dot arrangement cycle in the sub-scanning direction is varied to suppress moiré and color tone change. However, since the thermal element is structurally fixed, it can be expected to suppress moiré and color tone change with respect to misregistration in the main scanning direction, which is the direction in which the thermal elements are arranged. could not. Therefore, as shown in FIG. 6, the first color (FIG.
When the second color (FIG. 6B) is superimposed on (a)), all pixels overlap in the ideal case where no registration error occurs (FIG. 6C), but in the main scanning direction. When the registration shift occurs, the positions of all the pixels shift (FIG. 6D),
For this reason, there is a problem that a substantial change in color appearance is increased, which leads to a reduction in color reproducibility. On the other hand, registration deviation in the main scanning direction can be improved by increasing the precision of the apparatus, but for that purpose, a highly accurate mechanism must be designed and manufactured, which leads to an increase in the cost of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and does not substantially change the appearance of color even when the color overlap is shifted in the main scanning direction without increasing the apparatus cost. Providing an image recording method capable of
It is intended to improve color reproducibility.

[0007]

In order to achieve the above object, an image recording method according to the present invention uses a head in which a plurality of thermal elements are arranged at regular intervals and uses a head parallel to the arrangement direction and the arrangement direction. In the image recording method of a printer for recording dots in a direction orthogonal to the above, the dot arrangement is modulated in a direction parallel to the arrangement direction of the thermal elements and recorded. Also, the image recording method
An image recording method in which a non-recording portion which alternately appears in units of a predetermined number of dots per line is arranged and recorded by alternately applying energy for every predetermined number of elements in the arrangement direction of the thermal elements, The recording dot may be moved in the direction of the position where the weak energy is applied by applying a weak energy that is not recorded on the recording dot and changing the energy on both sides of the recording dot. At this time, by alternately applying energy to even-numbered and odd-numbered elements in the arrangement direction of the thermal elements, a non-recording portion that appears alternately for each line may be arranged for recording. Further, the image recording method is characterized in that, by changing the weak energy on both sides of the recording dot, the direction of the inclination of the dot pattern of each pair adjacent to the arrangement direction of the thermal elements is changed for each color. May be used. And
The modulation is preferably in the range of 1/40 or more and less than 1/1 of the arrangement pitch of the thermal elements.

In this image recording method, a dot arrangement is modulated in a direction parallel to the arrangement direction of the thermal elements, and recording is performed. Even when a registration shift occurs in the direction, some dots overlap, and all pixels do not shift evenly, so that a substantial change in color appearance is reduced. In addition, by applying weak energy to the non-recording portion to such an extent that recording is not performed and changing this energy on both sides of the recording dot, the recording dot can be shifted in the main scanning direction. Furthermore, since the inclination directions of the dot patterns that are adjacent to each other in pairs that are inclined with respect to the arrangement direction of the thermal elements change for each color, all pixels no longer incline in the same direction, and a substantial change in color appearance Become smaller. And
The effect of suppressing the change in color appearance is remarkable by modulating dots in a range of 1/40 to less than 1/1 of the pitch.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the image recording method according to the present invention will be described below. In this embodiment, an example in which the image recording method according to the present invention is applied to a thermal transfer printer will be described. In the above-described printer, a plurality of thermal elements are arranged in a line in the main scanning direction in the thermal head, and the thermal elements heat the back of the ink ribbon and transfer the softened ink to the image receiving sheet. The image receiving sheet and the ink ribbon move in a direction (sub-scanning direction) perpendicular to the arrangement direction of the thermal elements while being in close contact with each other. The recording paper is reciprocated according to the number of colors of the ink ribbon (four times), and each color of black, cyan, magenta, and yellow is sequentially transferred.

FIG. 1 is a diagram for explaining dots modulated by applying the present invention. The heat element generates heat alternately at even-numbered and odd-numbered lines for each line according to the pulse width output from the pulse generating unit, thereby forming a so-called staggered arrangement in which one dot is alternately removed for each line. Record. To the thermal element corresponding to the recording portion, thermal energy equal to or greater than a threshold Th required for transferring ink to recording paper is supplied by controlling the pulse width. On the other hand, conventionally, no thermal energy was supplied to the thermal element corresponding to the non-recording portion, or constant thermal energy was supplied to the thermal element corresponding to all the non-recording portions. In the image recording method according to the embodiment, a different heat energy is supplied to a heat element corresponding to a non-recording portion to which no heat energy has been supplied conventionally.

That is, when printing in a staggered arrangement, for example, when printing even-numbered dots n and n + 2, a thermal element corresponding to dot n + 1 (odd-numbered dot) between the dots n and n + 2 is used. Heat energy is supplied.
The heat energy at this time is set so as to be equal to or less than the threshold Th by controlling the pulse width.
Therefore, the dot n + 1 is not recorded by the heat element to which the heat energy equal to or less than the threshold value Th (hereinafter, referred to as 0 heat) is supplied.

On the other hand, 0 heat is applied to the recording position of the dot n + 1, so that a thermal history remains. In this state, the threshold value Th is set for the dots n and n + 2.
When the above heat energy is supplied, the heat energy of the dot n + 1 and the dots n and n +
2 and exceeds the recordable heat energy threshold Th. Thereby, as a result, the even-numbered dots n and n + 2 move in the direction approaching each other (the direction of arrow a).
To be recorded.

This 0 heat can be variously changed by controlling the pulse width. Therefore, by controlling this heat energy, it is possible to modulate the dots in the main scanning direction.

As described above, according to the above-described image recording method, in the case of, for example, staggered recording using a thermal head, the heat element is structurally fixed by supplying 0 heat to the non-recorded heat element. Therefore, it is possible to modulate the dot position even in the case of registration deviation in the main scanning direction, which was impossible in the related art. By modulating the dot position in this way, as shown in FIG. 2, the first color (FIG. 2A) is compared with the second color (FIG. 2A).
When (b)) is recorded, some dots will be misaligned even if no misregistration has occurred (FIG. 2).
(C)). On the other hand, when a registration shift occurs in the main scanning direction, this causes a dot shift (see FIG. 2).
(D)). However, since the dot position is modulated in the main scanning direction, all the pixels do not shift equally, and the change in the dot shift amount is not large compared to the case where no registration shift has occurred. In addition, even when a registration error occurs, a substantial change in color appearance is reduced, and color reproducibility can be improved. In other words, in the past, it was necessary to design and manufacture a very high-precision mechanism in order to reduce the color change. Since there is no problem in the performance, the cost of the apparatus can be reduced.

[0015]

Next, the results of comparing the color misregistration between the image recording method according to the present invention and the conventional image recording method will be described. Below, various conditions for implementation are shown. a. Thermal head • Resolution in the main scanning direction: 600 dpi • Thermal element size: 35 μ in the main scanning direction, 40 μ in the sub-scanning direction • Head resistance value: 3142 Ω • Voltage: 9 V • Dot array in the main scanning direction: K (black) = 1 C (cyan) ) = 2 M (magenta) = 1 Y (yellow) = 2 b. Sub-scanning speed: 4.23 mm / s c. Ribbon: Proof ribbon J for FirstProof manufactured by Fuji Photo Film Co., Ltd. d. Image receiving sheet: Receiver sheet A3WL manufactured by Fuji Photo Film Co., Ltd. e. Dot pitch in the sub-scanning direction: K = 600 dpi C = 500 dpi M = 400 dpi Y = 300 dpi f. Strobe of each color: K = 1.4 μsec (pulse width) C = 1.2 μsec M = 1.7 μsec Y = 2.0 μsec

FIG. 3 is an explanatory diagram of a dot pattern recorded without using 0 heat in the image recording method according to the present invention.
Is an explanatory diagram showing the application position of 0 heat, and FIG. 5 is an explanatory diagram of a dot pattern including dots moved by applying 0 heat. 3 to 5 show dots for each color for convenience of description, but in actual printing, dots of each color are printed on the same surface. When no heat is applied, dots of each color are recorded in the dot pattern shown in FIG. That is, this is the same as the recording result by the conventional image recording method (Comparative Example 1 described later).

In the thermal element for recording the dot pattern shown in FIG. 3, 0 heat was supplied to the thermal element in the non-recording portion at the position shown in FIG. 4 (the position marked + in the figure). As a result, the dots were modulated in the main scanning direction, and the dot pattern shown in FIG. 5 was recorded. In FIG. 5, for black (K), for example, dots n and n + 4 on the first line have moved in the direction of the 0 heat application position (to the right in the drawing). In cyan (C), for example, dots n and n + 1 on the first line have moved in the direction of the 0 heat application position. In magenta (M), for example, dots n and n + 4 on the first line moved in the direction of the 0 heat application position. In the yellow (Y), for example, the dots of n + 4 and n + 5 are 0 in the first line.
It moved in the direction of the heat application position.

In black (K), the heat element is applied by applying 0 heat to n + 1 and n + 5 on the first line, n + 3 and n + 6 on the second line, and n + 3 and n + 7 on the third line. Dot patterns KD, which are adjacent to each other and are inclined one by one in the downward direction with respect to the arrangement direction of
(See FIG. 5), and in magenta (M), 0 heat is applied to positions n + 1 and n + 5 in the first line, n and n + 4 in the second line, and n + 3 and n + 7 in the third line. As a result, a pair of dot patterns M which are adjacent to each other and inclined in a downwardly descending manner with respect to the arrangement direction of the thermal elements.
D (see FIG. 5) was recorded. Further, the value of 0 heat at this time was changed between Example 1, Example 2, and Comparative Example 2, and
Table 1 shows the results of comparison of substantial color appearance, with Comparative Example 1 being the case where no heat was applied.

[0019]

[Table 1]

As can be seen from Table 1, in Comparative Example 1 where no heat was applied, there was no dot modulation in the main scanning direction.
The change in color appearance due to misregistration became large.
On the other hand, in Example 1 in which 0 heat was applied by weak heat energy, the dots were modulated at a moving distance of 5 μm, and the change in color appearance was suppressed. In Example 2 in which 0 heat was applied by strong heat energy, the dots were modulated at a moving distance of 8 μm, the change in color appearance was improved, and the color reproducibility was improved. In Comparative Example 2 in which the thermal energy applied to the thermal element at the non-recording position exceeded the threshold value Th, the thermal energy was also recorded in the zero heat portion, making it impossible to determine the color appearance.

As described above, it was confirmed that the dot moving distance can be arbitrarily controlled by controlling the pulse width of 0 heat. Then, in order to suppress a change in color appearance, 1/40 to less than 1/1 (1/4) of the dot pitch p
It has been found that the effect is exhibited by modulating at a moving distance of 0 ≦ p <1/1). Further, by applying 0 heat, by changing the inclination direction of a pair of adjacent dot patterns inclined with respect to the arrangement direction of the thermal elements for each color, all the pixels do not incline in the same direction. Also, the change in the substantial color appearance was reduced, and the color reproducibility was improved. Note that, in the embodiment, an example is given in which 0 heat is set on the left and right sides of the recording dot, but the same effect can be obtained by applying 0 heat to all and changing the energy of 0 heat on the left and right. . Further, in this embodiment, the case where the present invention is applied to all four colors has been described, but the present invention may be applied to only three colors.
In particular, the effect of the overlapping change between black and other colors is most noticeable, so apply it only to black and use other cyan,
Even if it is not applied to magenta and yellow, it is possible to reduce the change in color appearance.

In the above description, the case where the image recording method of the present invention is applied to a thermal transfer type printer is described as an example. However, the image recording method of the present invention is applied to other types of printers using a thermal head. However, the same effect can be obtained. Further, by the same action, even in a method such as electrophotography or ink jet which is not in the thermal mode, weak energy (electric field, ink) that is not recorded.
, The same effect can be expected. Furthermore, even in the case of digital recording on an optical tape or the like, by performing the same processing as described above, the bit string of data can be modulated right and left, so that data having different low frequencies can be superimposed on data.

[0023]

As described in detail above, according to the image recording method of the present invention, the dot array is modulated in the direction parallel to the arrangement direction of the thermal elements and recorded, so that the color in the main scanning direction is recorded. Even if the overlap occurs, a substantial change in color appearance is reduced, and color reproducibility can be improved. In addition, by applying weak energy to the non-recording portion to such an extent that recording is not performed and changing this energy on both sides of the recording dot, the recording dot can be easily shifted in the main scanning direction. Furthermore, by changing the inclination direction of a pair of adjacent dot patterns inclined with respect to the arrangement direction of the thermal elements for each color, it is possible to prevent all the pixels from being inclined in the same direction. The change in the appearance of the color becomes small, and the color reproducibility can be improved. The effect of suppressing the change in color appearance can be enhanced by modulating the dots in a range of 1/40 to less than 1/1 of the pitch.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining dots modulated by applying the present invention.

FIG. 2 is an explanatory diagram showing how colors overlap when 0 heat is used.

FIG. 3 is an explanatory diagram of a dot pattern recorded without using 0 heat in the image recording method according to the present invention.

FIG. 4 is an explanatory diagram showing the application position of 0 heat.

FIG. 5 is an explanatory diagram of a dot pattern including dots moved by applying 0 heat.

FIG. 6 is an explanatory diagram showing a conventional color overlapping state.

[Explanation of symbols]

 KD, MD Inclined adjacent dot pattern p Dot array pitch

Claims (5)

[Claims] 1. An image recording method for a printer which uses a head in which a plurality of thermal elements are arranged at regular intervals and records dots in a direction parallel to the arrangement direction and in a direction perpendicular to the arrangement direction. An image recording method characterized by modulating and recording a dot array in a direction parallel to an array direction. 2. An image recording method in which non-recording portions appearing alternately in units of a predetermined number of dots for each line are arranged and recorded by alternately applying energy for each predetermined number of elements in the direction in which the thermal elements are arranged. 11. A method according to claim 9, wherein the recording dot is displaced in the direction of the position to which the weak energy is applied by applying a weak energy that is not recorded on the non-recording portion and changing the energy on both sides of the recording dot. 2. The image recording method according to 1. 3. An energy is alternately applied to even-numbered and odd-numbered elements in the arrangement direction of the thermal elements, thereby achieving 1
3. The image recording method according to claim 2, wherein non-recording portions appearing alternately for each line are recorded. 4. The image recording method according to claim 1, wherein the modulation is performed in a range of 1/40 or more and less than 1/1 of an arrangement pitch of the thermal elements. 5. The printing method according to claim 1, wherein the weak energy is changed on both sides of the recording dot to change the direction of the inclination of a pair of adjacent dot patterns inclined with respect to the arrangement direction of the thermal elements for each color. Item 4. The image recording method according to item 2 or 3.