JP2794739B2 - Thermal printer and thermal printing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer and a thermal printing method for printing characters and the like on recording paper using a thermal head having a heating element array in which heating elements are arranged in a line. About.

2. Description of the Related Art A thermal printer is used to form an image such as a character or a still image on a recording sheet, and an image forming operation is performed while conveying the recording sheet between a thermal head and a platen roller. When the recording paper is plain paper, an ink film coated with a heat-meltable or thermal sublimation type ink is used, and this film is transported between the thermal head and the recording paper, and the ink of the ink film is removed. The image is transferred and formed on a recording sheet. On the other hand, when the recording paper is heat-sensitive paper, an image is formed directly on the recording paper without using an ink film.

This thermal printer has a heating element array in which heating elements for forming one dot on recording paper are linearly arranged. Therefore, when characters and numerals are formed using a thermal printer, it is necessary to form a large number of dots per unit size in order to obtain a high resolution comparable to that of printing using printed characters. The same applies to the case where a color image is formed on a recording sheet by transfer. The higher the dot density, that is, the higher the pixel density, the higher the resolution of a transferred image.

Problems to be Solved by the Invention The dot density in a thermal printer that has been developed so far is about 6 to 12 per 1 mm, and manufacturing a heating element having a density higher than 1 is not considered costly. Realistically difficult.

When hard-copying a color still image projected on a CRT onto recording paper, if the dot density of the heating element of the thermal head is lower than the pixel density projected on the CRT screen, an image compatible with the CRT Select (decimate) image data from the image memory where data is stored
Must be transferred to thermal head.

The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to obtain various images such as high-resolution characters and images without increasing the density of heating elements in a thermal head. And

In the thermal printer according to the first aspect of the present invention, since the energization of the heating element is controlled by the thermal head energizing means, the heating element generates heat more than the maximum pixel that can be formed on the recording paper. N (N
(Two natural numbers). Subdivided pixels of equal size are formed in accordance with the image data. As a result, a pixel smaller than this area, that is, a finely divided pixel, can be formed on the recording paper by the heating element having a large area without reducing the surface area of the heating element to the extent that it is difficult to manufacture. In addition, the thermal head positioning means shifts the relative position between the thermal head and the recording paper in the direction in which the heating elements are arranged, and repeats N times of recording to record an image. Recording can be performed at a pixel density N times the element arrangement density.

Further, in the thermal printer according to the second aspect, in addition to the operation of the thermal printer according to the first aspect, the relative position of the thermal head and the recording paper in the heating element arrangement direction is shifted by moving the thermal head. The positioning accuracy is improved as compared with the case where the recording paper is shifted by moving the recording paper.

In the thermal printer according to the third aspect, in addition to the operation of the thermal printer according to the first aspect, the pixel size in the direction intersecting with the arrangement direction of the heating elements is also reduced to 1 / N like the pixel size in the arrangement direction. Further, image recording with a high pixel density can be performed.

In the thermal printer according to the fourth aspect, since the recording is performed using the N thermal heads positioned parallel to each other and shifted in the heating element arrangement direction, the relative position between the thermal head and the recording paper is shifted. for,
A complicated mechanism is not required, and an image can be recorded with a high pixel density as in the thermal printer of the first aspect.

In the thermal printer according to the fifth aspect, in addition to the action of the thermal printer according to the fourth aspect, the pixel size in the direction intersecting the arrangement direction of the heating elements is also reduced to 1 / N like the pixel size in the arrangement direction. In addition, it is possible to record an image with a higher pixel density.

In the thermal printing method according to the sixth aspect, the energization of the heating element is divided into N (N is a natural number of 2 or more) equal to N in the heating element arrangement direction from the maximum pixel that the heating element can originally form on the recording paper. In order to control the formation of the subdivided elements having the specified dimensions, the heating element having a large area can be used to reduce the area of the pixel, that is, the subdivision, without reducing the surface area of the heating element to the extent that it is difficult to manufacture. Pixels can be formed on the recording paper. In addition, since the image is recorded by repeating the recording N times while shifting the relative position between the thermal head and the recording paper in the arrangement direction of the heating elements, the arrangement density of the heating elements in the arrangement direction of the heating elements is N in the heating element arrangement direction. Recording can be performed at twice the pixel density.

Examples Hereinafter, the present invention will be described in detail based on illustrated examples of the present invention.

FIG. 1A is a view showing a basic structure of a thermal printer according to the present invention. This thermal printer is of a transfer type, and has a platen roller 1 and a thermal printer which can be pressed against and released from the platen roller 1. And a head 2.
The recording paper 3 is conveyed between the platen roller 1 and the thermal head 2. Between the recording paper 3 and the thermal head 2, the recording paper 3 is fed from the supply-side ink film roll 4 and is taken up by the winding-side ink film roll. The ink film 6 wound around 5 is conveyed. When a color image is transferred to the recording paper 3, the ink film 6 is coated with yellow, magenta, and cyan color thermofusible or thermosublimable inks.
After the color is transferred, the ink film 6 is fed and conveyed to the next color portion, while the recording paper 3 is returned and conveyed, and the next color is transferred in an overlapping manner. When using the ink film 6 coated with three color inks, three transfer operations are performed. In accordance with the color inks, the ink film coated with the intermediate color ink or the black ink is used. When used, transfer operations are performed for the number of colors of the ink.

FIG. 2 shows a heating element provided on the thermal head 2.
FIG. 3 is a diagram showing a schematic shape of a surface of the heating element, and a heating element array is formed by linearly arranging the heating elements in a direction along a central axis of the platen roller.
Since the direction in which the heating element array 11 is formed is along the central axis of the platen roller 1 as described above, the direction is substantially perpendicular to the sub-scanning direction in which the recording paper 3 is conveyed. Yes, in the main scanning direction. In FIG. 2, the main scanning direction (the direction in which the heating elements are arranged) is indicated by reference numeral A, and the sub-scanning direction (the direction intersecting with the arrangement direction of the heating elements) is indicated by reference sign B.

The surface of the heating element 10 shown in the drawing is substantially square, and the length in the longitudinal direction of the heating element array 11, that is, the dimension in the main scanning direction and the dimension in the width direction perpendicular to the main scanning direction are all indicated by the symbol D. I have. However, the surface shape of the heating element 10 is not limited to a square, but may be various shapes such as a rectangle. Further, since the heating element array 11 is used to form an image by transferring, for example, about 6 to 8 dots per 1 mm on the recording paper 3, the D dimension is 1/6 to 1/1. It is set to 8mm or less.

In the case where an image is transferred onto the recording paper 3 by using such a heating element 10, conventionally, each of the heating elements 10 is supplied to each heating element 10 so that the largest pixel is formed in the entire area of the heating element 10. The applied energy is controlled. The pixel having the maximum size is almost similar to the size D or slightly smaller. In FIG. 2, the maximum pixel area S indicated by hatching is shown.
Indicated by

FIG. 3 shows each heating element 10 in the thermal printer.
FIG. 3 is a characteristic curve showing the relationship between the applied energy applied to the element and the heat generation area of the surface of the element 10 due to the applied energy. In order to form the maximum pixel region S having the maximum image formable dimension, FIG. It is necessary to supply the applied energy Emax. This applied energy is adjusted by controlling the energization time on the order of milliseconds. By adjusting the applied energy, the temperature of the central portion of the heating element 10 becomes the highest, and an image including the maximum pixel region S having an area corresponding to the contour of the heating element 10 is formed.

This means that, as shown in FIG.
And a thermal type thermal printer that does not use the ink film 6 has commonality. In other words, if the applied energy is adjusted, the transfer area changes in a transfer type printer, and the coloration area changes in a thermal type printer.

The present invention has been made based on the understanding that the dot area of an image that can be formed on the recording paper 3, that is, the pixel area can be changed by adjusting the energy applied to the heating element 10 as described above. For example, when the applied energy En smaller than the applied energy Emax is supplied to the heating element 10, as shown in FIG.
It is possible to form a pixel region only in a portion having a quarter of the area of the maximum pixel region S having a maximum pixel formable dimension. This subdivided pixel region R is formed in a portion of the recording paper 3 corresponding to a position corresponding to the center of each of the heating elements 10.

FIG. 4 shows the subdivision formed on the recording paper 3 by supplying the above-mentioned applied energy En to one heating element 10 having the above-mentioned dimension D in the main scanning direction A and the sub-scanning direction B. FIG. 4 is a diagram showing a pixel region R, which is a pixel which is originally formed by the heating element 10, that is, a maximum pixel region S is divided into two in the main and sub scanning directions. Therefore, in principle, as shown in FIG. 2, the center O of the portion Sa corresponding to the area S to be formed on the recording paper 3 by the heating element 10 is positioned with respect to the center P of the heating element 10. By shifting the center P of the heating element 10 to the position of the subdivided pixel area R obtained by bisecting the area S, the per unit length of the original pixel formed by the heating element 10 An image having twice the pixel density, that is, four times the pixel density per unit area can be formed.

In other words, the position of the shift described above is different from each heating element.
With respect to the center P between the main scanning direction A and the sub-scanning direction B of 10,
This means that the center O of the pixel region Sa that should be formed at a time by one heat-generating element 10 at a time is shifted, and the maximum pixel region S is divided into two in the main and sub directions. This means that the shift is performed so that the center P is set at the position of R. In the case where a subdivided pixel region R having an area divided into four is formed on the recording paper 3 as shown in the figure, the pixels formed by one heating element array 11 are Every other in the main scanning direction A, and in the sub-scanning direction B, approximately one half of the dimension D of the heating element 10,
In other words, it is one half of the dimension D in which the maximum number of pixels that can be formed by the heating element 10 is formed. Therefore, in order to form an image on the entire recording paper 3 using a thermal printer having only one thermal head, it is necessary to form the image while transporting the recording paper 3 by 1/2 of the dimension D. And recording paper 3 again
On the other hand, it is necessary to shift the thermal head 2 by a distance of D / 2 in the main scanning direction to form the remaining image. In FIG. 4, the subdivided pixel regions R indicated by broken lines correspond to the recording paper 3
After forming an image for one line, this is fed and conveyed to form an image formed in the next line.

FIG. 5 is a view showing a thermal head positioning mechanism for shifting the thermal head 2 as described above.
The thermal head 2 includes a support member 11 having support shafts 10a and 10b protruding at both ends, a heat sink 12 for heat radiation attached to the support member 11, and a thermal head body 13 fixed to the heat sink 12. I have. The head body 13 is provided with a heating element array 14 in which the heating elements 10 described above are arranged in the main scanning direction B and are linear. The heat sink 12 in which the head body 13 is integrated is mounted on the support member 11 so as to be able to swing about the yaw shaft 15 as shown in FIG. 14 is configured to uniformly and uniformly press the platen roller 1. In order to smoothly perform this swinging motion, rotating rollers 16 that roll on the flat surface of the support member are provided at both ends of the heat sink 12. The pressing movement and the pressing release movement of the thermal head 2 with respect to the platen roller 1 are performed by supporting shafts at both ends.
This is achieved by connecting a rotary drive mechanism to one of 10a and 10b.

A positioning surface 17 is provided on one end surface of the support member 11.
A cam 19 driven by a head shift motor 18 is in contact with the positioning surface 17.
On the other hand, a compression coil spring 2 is attached to the support shaft 10b on the opposite side.
The spring 20 has one end in contact with the side plate 21 through which the support shaft 10b passes, the other end in contact with the end surface of the support member 11, and a direction toward the cam 19 with respect to the support member 11. Of resilience. Therefore, after the recording paper 3 is conveyed at the dimension of D / 2, a half of the entire image is formed, and then the recording paper 3 is returned and the cam 19 is driven by the head shift motor 18. Thus, the thermal head 2 is shifted and positioned in the main scanning direction by a distance of D / 2. In this state, image formation of the remaining portion is performed using the same thermal head 2 again.

FIG. 6 is a view showing a thermal printer according to another embodiment of the present invention. In this case, similarly to the above-described embodiment, the maximum pixel formable dimension D which can be formed by one heating element 10 is 2. The recording paper 3 is formed in the subdivided pixel region R set to a pixel size of 1/1, but in this case, two thermal heads are provided to constitute a thermal printer.

As shown in FIG. 6, two platen rollers 1a and 1b are provided in parallel with each other, and the thermal heads 2a and 2b can be pressed against and released from the respective platen rollers 1a and 1b. . And one thermal head
2a, the center of the heating element 10a and the other thermal head 2
As shown in FIG. 7, the center of the heating element 10b at b is shifted from each other by a distance of D / 2 in the main scanning direction A and positioned at that position.

FIG. 8 is a diagram showing a control circuit for controlling the operation of the thermal printer of the present invention. In this case, the control circuit has only one thermal head and is a transfer type thermal printer using the ink film 5. For printers. CPU30 composed of a microcomputer etc.
Has a print switch to instruct print start
An image data memory 32 in which image information to be formed on the recording paper 3 is stored is connected. Also, this CPU3
0, a paper feed mechanism 33 for feeding out the recording paper 3 one by one from a paper feed tray (not shown) that accommodates cut sheets as the recording paper 3 in a stacked state, A recording paper transport motor 34 for supplying the paper 3 between the thermal head and the platen roller, a platen roller driving mechanism 35, an ink film winding motor 36, and press-contact and press-contact of the thermal head toward the platen roller Pressure contact mechanism 37 for performing
A thermal head energizing mechanism (thermal head energizing means) 38 for supplying applied energy En to the heating element 10 of the thermal head is connected to each other, and a control signal from the CPU 30 is sent to these. ing.
The control circuit of the thermal printer is basically the same as that of the thermal printer except that the control circuit does not include the ink film winding mechanism 36.

FIG. 9 is a diagram showing a main flow chart of the thermal printer of the present invention, and the printer is initialized as shown in step 1 when these printers are started. When the print switch 31 is turned on in step 2 in this state, a print processing subroutine shown in step 3 is executed. If the end of the print processing is determined in step 4, the state returns to the state where the initial setting is completed.

FIG. 10 shows the printing process in the case where a single color printing such as black only is performed in a thermal transfer type thermal printer in a case where double image density printing is selected by operating a selection switch (not shown). FIG. 14 is a diagram illustrating details of a subroutine 3; In the case of performing color printing by performing printing of a plurality of colors in a superimposed manner, the color of the ink film is changed, and the processing from step 5 to step 29 described below is executed a predetermined number of times. However, the details are omitted.

In step 5, the number L of all lines corresponding to the size of the recording paper 3 is set. For example, if the maximum pixel area S having the maximum pixel formable size D of the heating element 10 is to be transferred to the recording paper 3 of A3 size, the number of lines is 32.
Although the number is 00, the number of lines is twice as large because the subdivided pixel region R having half the size is formed. The number of pixel data to be formed by the heating element array 11 that is one line is twice the number of the heating elements 10 that are actually arranged in the main scanning direction A. Among the pixels formed in A, first, odd-numbered image data is transferred to all the heating elements 10 arranged in a line.
The thermal head 2 is pressed against the platen roller 1 in step 6. As a result, as shown in step 8, a predetermined portion of the portion corresponding to the portion of the subdivided pixels R in one row at intervals of the subdivided pixel region R based on the image data from the memory 32 Is printed.

Next, in step 9, the ribbon winding motor 36 is driven, and in step 10, the recording paper transport motor 34 is driven to
The heating element 10 is conveyed in the feed direction by a half distance of the width D of the heating element 10 in the sub-scanning direction. Every time one line is conveyed, 1 is subtracted from the number of lines set in step 11, and it is determined in step 12 whether the set number of lines has been printed. When printing of all the lines is completed, the pressure contact of the thermal head is released in step 13, and the ink film winding motor 36 is stopped.

Further, at step 15, the recording paper transport motor 34 is rotated in the reverse direction to return the recording paper 3, and at step 16, the number of lines is added. If it is determined in step 17 that the paper has been transported to the predetermined number of lines, the recording paper transport motor 34 is stopped in step 18, and then the cam 19 is driven by the cam drive motor 18. With thermal head 2
Shift by a distance of D / 2. Next, the even-numbered image data for each line is transferred to each heating element 10 in step 20, and steps 21 to 28 similar to steps 7-14 are executed, and all the pixels are printed on the recording paper 3. It is formed.

After an image of one sheet of the recording paper 3 is formed in this way, step 29 is executed, and the thermal head 2 is shifted to the original position. Is discharged to the outside. As a result, the recording paper 3 after the transfer is moved by one and a half reciprocations at the portion of the thermal head 2.

FIG. 11 is a flowchart showing details of the print processing subroutine 3 shown in FIG. 9 when the present invention is applied to a thermal type thermal printer. Step 36 is executed to form an image in a half area of the entire printing area on the recording paper 3.

Since the case shown in this flowchart is for one thermal head, the thermal head 2 is shifted by a distance of D / 2 in step 37. At this time, the cam 19 shown in FIG. 5 rotates. Step again
Transfer is performed from 38 to the remaining portion in step 43. However, in the case of a thermal type thermal printer, an image can be formed by coloring the recording paper 3 while returning the recording paper 3, so that recording is performed in step 41. The remaining image can be formed while returning and transporting the paper 3.

If the end of printing is detected in step 44, the recording paper 3 is discharged to the outside in step 46 after shifting to the original position of the thermal head 2 in step 45.

In the above-described embodiment, a case is shown in which the subdivided pixel of half the maximum pixel formable size D in both the main and sub directions of each heating element 10 is formed by transferring or coloring the recording paper 3. However, if it is possible to form a subdivided pixel region R having a size obtained by dividing the size D by N, the present invention is not limited to two.
More than this is fine. That is, if the value of N is a natural number (positive integer) of 2 or more, the present invention can be embodied in principle. If it is divided into three, the recording paper 3
It may be transported twice or use three thermal heads.

As described above, in the thermal printer according to the first aspect of the present invention, since the energization of the heating element is controlled by the thermal head energizing means, the heating element is originally formed on the recording paper. Subdivided pixels having dimensions equal to N (N is a natural number of 2 or more) are formed in accordance with the image data in the heating element arrangement direction more than the obtained maximum pixel. As a result, a pixel smaller than this area, that is, a finely divided pixel, can be formed on the recording paper by the heating element having a large area without reducing the surface area of the heating element to the extent that it is difficult to manufacture. In addition, the thermal head positioning means shifts the relative position between the thermal head and the recording paper in the direction in which the heating elements are arranged, and repeats N times of recording to record an image. Recording can be performed at a pixel density N times the element arrangement density.

Further, in the thermal printer according to the second aspect, in addition to the effect of the thermal printer according to the first aspect, the relative position of the thermal head and the recording paper in the heating element arrangement direction is shifted by moving the thermal head. The positioning accuracy is improved as compared with the case where the recording paper is shifted by moving the recording paper.

Further, in the thermal printer according to the third aspect, in addition to the effect of the thermal printer according to the first aspect, the pixel size in the direction intersecting with the arrangement direction of the heating elements is also reduced to 1 / N like the pixel size in the arrangement direction. Further, image recording with a high pixel density can be performed.

In the thermal printer according to the fourth aspect, since the recording is performed using the N thermal heads positioned parallel to each other and shifted in the heating element arrangement direction, the relative position between the thermal head and the recording paper is shifted. for,
A complicated mechanism is not required, and an image can be recorded with a high pixel density as in the thermal printer of the first aspect.

In the thermal printer according to the fifth aspect, in addition to the effect of the thermal printer according to the fourth aspect, the pixel size in the direction intersecting with the arrangement direction of the heating elements is also reduced to 1 / N like the pixel size in the arrangement direction. Further, image recording with a high pixel density can be performed.

In the thermal printing method according to the sixth aspect, the energization of the heating element is divided into N (N is a natural number of 2 or more) equal to N in the heating element arrangement direction from the maximum pixel that the heating element can originally form on the recording paper. In order to control the formation of the subdivided elements having the specified dimensions, the heating element having a large area can be used to reduce the area of the pixel, that is, the subdivision, without reducing the surface area of the heating element to the extent that it is difficult to manufacture. Pixels can be formed on the recording paper. In addition, since the image is recorded by repeating the recording N times while shifting the relative position between the thermal head and the recording paper in the arrangement direction of the heating elements, the arrangement density of the heating elements in the arrangement direction of the heating elements is N in the heating element arrangement direction. Recording can be performed at twice the pixel density.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic structure of a thermal printer when the present invention is applied to a transfer type thermal printer, and FIG. 2 is a maximum pixel area and a subdivided pixel area formed on recording paper by one heating element. Plan view showing the relationship with
FIG. 3 is a characteristic diagram showing a relationship between applied energy supplied to each heating element and a heating area, and FIG. 4 is a diagram showing a plurality of heating elements forming a heating element array at a predetermined distance from a recording sheet. FIG. 5 is a plan view showing the formed subdivided pixel area, FIG. 5 is a perspective view showing a mechanism for shifting the thermal head, FIG. 6 is a front view showing a thermal printer having two thermal heads, and FIG. A plan view showing a state in which pixels are formed in two columns at the same time by this thermal printer;
FIG. 8 is a circuit diagram showing a control circuit for controlling the operation of the transfer type printer when the present invention is embodied,
9 is a main flowchart showing an operation procedure by the control circuit shown in FIG. 8, FIG. 10 is a flowchart showing a print processing subroutine of FIG. 9 in a transfer type thermal printer, and FIG. 11 is a thermal type thermal printer. 4 is a flowchart illustrating a print processing subroutine in the printer.

Continuation of the front page (56) References JP-A-61-140267 (JP, A) JP-A-57-41975 (JP, A) JP-A-63-62747 (JP, A) JP-A-58-5279 (JP) JP-A-63-202473 (JP, A) JP-A-63-77745 (JP, U) JP-A-62-80643 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB Name) B41J 2/315-2/38 B41J 2/30 B41J 2/515

Claims (6)

(57) [Claims] 1. A thermal printer which performs recording by a thermal head including a plurality of heating elements arranged in a straight line at a predetermined interval D according to a predetermined pixel density, wherein a pixel formed on recording paper by the heating element is provided. A thermal head energizing means for controlling energization to each heating element in accordance with image data so that 1 / N (N is a natural number of 2 or more) of the largest pixel in the arrangement direction of the heating elements; Thermal head positioning means for shifting the relative position of the head with respect to the recording paper by D / N units in the arrangement direction of the heating elements, at each shift position of the thermal head positioning means, Is performed by performing energization control on the pixel, and the N times of the printing operation causes an image having a pixel density of N times the predetermined pixel density. Thermal printer characterized in that for recording. 2. The thermal printer according to claim 1, wherein said thermal head positioning means holds the thermal head movably with respect to the recording paper by a D / N unit in a direction in which the heating elements are arranged. A thermal printer having a holding mechanism. 3. The thermal printer according to claim 1, wherein the heating elements have a length equal to an arrangement direction and a direction intersecting the arrangement direction, and the thermal head energizing means includes:
A thermal printer characterized in that the width of a pixel formed on a recording sheet in an arrangement direction and a direction intersecting the arrangement direction is set to 1 / N of a maximum pixel by controlling the amount of electricity to each heating element. 4. A heating apparatus comprising a plurality of heating elements arranged on a straight line at a predetermined interval D according to a predetermined pixel density, wherein D / N (N is a natural number of 2 or more) in parallel with each other and in the heating element arrangement direction. )
And the number of pixels formed on the recording paper by the heating elements are 1 / N (N is a natural number of 2 or more) of the largest pixel in the arrangement direction of the heating elements. A thermal head energizing means for controlling energization of the heating elements of each thermal head in accordance with image data, and by executing energization control of the heating elements by the energizing means, N thermal heads are controlled. A thermal printer for performing recording by using an image having a pixel density of N times the predetermined pixel density. 5. A thermal printer according to claim 4, wherein said heating elements have a length equal to an arrangement direction and a direction intersecting the arrangement direction, and said thermal head energizing means comprises:
A thermal printer characterized in that the width of a pixel formed on a recording sheet in an arrangement direction and a direction intersecting the arrangement direction is set to 1 / N of a maximum pixel by controlling the amount of electricity to each heating element. 6. A thermal printing method in which recording is performed by a thermal head including a plurality of heating elements arranged in a straight line at a predetermined interval D according to a predetermined pixel density. A recording process in which energization of each heating element is controlled in accordance with image data to perform recording so that the number of pixels to be formed is 1 / N (N is a natural number of 2 or more) of a maximum pixel in the heating element arrangement direction. The relative position between the thermal head and the recording paper in the arrangement direction of the heating elements.
A thermal printing method characterized in that an image having a pixel density of N times the predetermined pixel density is recorded by shifting by D / N units and repeating N times.