JPH0761010A - Thermal printing method - Google Patents

Abstract

PURPOSE:To prevent thermal recording position from shifting and consequently contrive to improve print quality by a method wherein frictional coefficients at thermal recording of respective heat-sensitive color forming layers are kept nearly constant. CONSTITUTION:The higher the heat energy applied becomes, the lower the frictional coefficient at the surface of color heat-sensitive recording paper becomes. Among the heating element array provided on a thermal head, heat lying within the range of the heat energy, by which color does not come out in respective heat-sensitive color forming layers, is generated in heating elements outside the recording area of the color heat-sensitive recording paper. By balancing the frictional coefficients in the recording area shown by lines 46 with the frictional coefficients outside the recording area shown by lines 45, the frictional coefficient over the whole color recording paper shown by a line 47 is made nearly constant at the thermal recording of the respective heat- sensitive color forming layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printing method for recording an image on color thermal recording paper,
A thermal printer that maintains a constant coefficient of friction between the thermal head and the color thermal recording paper.

[0002]

2. Description of the Related Art A thermal recording type thermal printer is known in which a full-color image is directly heat-recorded on a color thermal recording paper. This color thermosensitive recording paper has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, a yellow thermosensitive coloring layer, and a protective layer, which are layered in this order. When printing, the thermal head moves relative to the color thermosensitive recording paper. Then, a yellow image is thermally recorded line by line on the yellow thermosensitive coloring layer having the lowest coloring heat energy, and then the yellow thermosensitive coloring layer is optically fixed. Then, a magenta image is thermally recorded on the magenta thermosensitive coloring layer having a medium coloring heat energy, and then the magenta thermosensitive coloring layer is optically fixed. Finally, a cyan image is heat-recorded on the cyan thermosensitive coloring layer having the highest coloring heat energy.

Heat generating elements are arranged in a line in the main scanning direction on the thermal head. This heating element array is provided in the same number as the number of bits of image data, and the width thereof becomes a recording area in the main scanning direction of the color thermosensitive recording paper. Further, Japanese Patent Laid-Open No. 2-117860 proposes a heating element provided outside the recording area. This is because the heating element near the central portion is close to the heating elements on both sides and thus the temperature drop is small and the print density is constant, but the heating element at the edge of the recording area has no heating element next to it. A decrease in temperature occurs and the print density is lower than in the central portion. Therefore, a heating element is also provided outside the recording area to generate a larger amount of heat energy in a range where the thermosensitive coloring layer does not develop color and the coloring heat energy is higher, so that the heating element at the edge portion is kept warm.

[0004]

By the way, the color thermosensitive recording paper has a property that the coefficient of friction of the surface becomes lower as the applied thermal energy becomes higher. Therefore, the color thermosensitive recording paper has a property of being less magenta than the heat recording at the yellow thermosensitive coloring layer. The thermal recording on the thermosensitive coloring layer has lower frictional resistance with the thermal head,
In the thermal recording on the cyan thermosensitive coloring layer, the friction resistance is further lowered. As a result, the load on the platen drum formed of rubber and its drive system changes, so that the amount of bending changes. These deflection amounts cause the recording positions of the thermosensitive coloring layers to be displaced, which causes color misregistration and deteriorates print quality.

From this, the above-mentioned JP-A-2-11786
The invention described in Japanese Patent Publication No. 0 promotes the fluctuation of the friction resistance between the color thermal recording paper and the thermal head at the time of thermal recording on each thermosensitive coloring layer, and has the effect of correcting the print density, but at the thermal recording position. There is a problem that the print quality is deteriorated due to the misalignment.

The present invention has been made in view of the above-mentioned problems, and the frictional resistance between the color thermosensitive recording paper and the thermal head at the time of thermal recording of each thermosensitive coloring layer is made equal so that the thermal recording position of each thermosensitive coloring layer is displaced. The purpose is to prevent printing and improve print quality.

[0007]

In order to achieve the above object, in the invention according to claim 1, as a thermal head,
When the heating element array is longer than the recording area and the heating elements in the recording area are driven to record a color image, the heating elements outside the recording area that are not involved in thermal recording are also driven at the same time. Within the range where the thermosensitive coloring layer of does not develop color,
The upper heat-sensitive color-developing layer has higher heat energy applied to the color heat-sensitive recording paper.

According to the second aspect of the invention, a thermal head having a heating element array longer than the recording area is used, and when the heating elements in the recording area are driven to record a color image, The heat-generating elements outside the recording area that are not involved in recording are also driven at the same time, and within the range in which the uppermost thermosensitive coloring layer does not develop color, the thermal energy that decreases as the average thermal energy of one line during recording becomes higher on the color thermal recording paper. It was something that was given.

As a result, the coefficient of friction of the color thermosensitive recording paper as a whole becomes almost the same during the thermal recording of each thermosensitive coloring layer, the feeding amount of the color thermosensitive recording paper is stabilized, and the thermal recording position of each thermosensitive coloring layer is displaced. Is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 3 showing an outline of a color thermal printer, a color thermal recording paper 2 sent out from a cassette (not shown) is transferred to a platen drum 5 by a pair of conveying rollers 4 provided in a paper feed passage 3. Will be sent to you. The platen drum 5 is rotationally driven by a stepping motor 7 via a platen shaft 6.

The platen drum 5 is provided with a clamper 8 for pressing and fixing the front end portion 2a of the color thermosensitive recording paper 2 against the outer peripheral surface 5a of the platen drum 5. The clamper 8 is slidably attached to the platen shaft 6 via a U-shaped groove 8a. The clamper 8 is pressed against the platen drum 5 by a U-shaped spring 12 hung on the platen drum 5, and the pressing force causes the clamper 8 to rotate together with the platen drum 5.

When the lever 11 is rotated clockwise by the motor 10 when the platen drum 5 is at the sheet feeding position shown in FIG. 3, the engaging portion 11a pushes down the pin 9 of the clamper 8 to cause the clamper 8 to move. To feed paper. When the platen drum 5 is at the paper discharge position shown in FIG.
When is rotated counterclockwise, the engaging portion 11b hooks the pin 9 and pushes it up, so that the clamper 8 is in a paper discharge state. In order to prevent the pin 9 from colliding with the lever 11 during the rotation of the platen drum 5, the engaging portions 11a,
11b is close to the side surface of the platen drum 5, and is bent in a crank shape so that the shaft side is separated from the platen drum 5.

On the outer periphery of the platen drum 5, a thermal head 13, a magenta optical fixing device 14 at a position downstream of the thermal head 13, and a yellow optical fixing device 15 are disposed downstream of the thermal head 13. . The magenta optical fixing device 14 includes a rod-shaped ultraviolet lamp 16 and a reflector 17 having an emission peak of about 365 nm, and the yellow optical fixing device 15 includes a rod-shaped ultraviolet lamp 18 and a reflector 19 having an emission peak of about 420 nm. Become. It is also possible to use one ultraviolet lamp that emits ultraviolet rays in the wavelength range of 365 to 420 nm and a filter that can be put in and taken out in front of this, and selectively extract two kinds of ultraviolet rays by this filter. This optical fixing device is arranged at the position of the magenta optical fixing device 14.

The thermal head 13 comprises a head body 20.
And a head holder 23. As shown in FIG. 4, the head body 20 is provided with a heating element array 21 in which a large number of heating elements are arranged in a line in the main scanning direction. A large number of heat generating elements 21a on the inner side are located in the recording area 2b (shown by hatching) of the color thermosensitive recording paper 2 and generate heat energy. The heating element 21b located outside the recording area 2b is not used for thermal recording,
It is used to keep the friction coefficient of the color thermosensitive recording paper 2 substantially constant.

The head main body 20 is arranged in a head holder 23, and the head main body 2 for the color thermosensitive recording paper 2 is arranged.
They are connected via a spring 22 that adjusts the pressing force of zero. The head body 20 and the head holder 23 are rotatably attached to the shaft 23a. Further, a roller 24 and a spring 25 are provided on the upper surface of the head holder 23, and the head body 20 is urged clockwise by the urging force of the spring 25 via the head holder 23.

A head cam 27 is provided above the head holder 23 so as to be rotatable around a shaft 31, and a roller 24 is in contact with the outer peripheral surface thereof by a spring 25 urging it. A notch 27 is formed on the outer peripheral surface of the head cam 27.
a and 27b are formed. When the notch 27a and the roller 24 are in contact with each other, the thermal head 13
Is located at a retracted position away from the platen drum 5 as shown in FIG. 3, and does not contact the tip portion of the clamper 8. When the roller 24 is in contact with the notch 27b, the head main body 20 presses the color thermosensitive recording paper 2 with a comparatively weak force for discharging the paper, as shown in FIG. Further, when the roller 24 is in contact with the outer peripheral surface of the head cam 27, as shown in FIG. 5, the head main body 20 contacts the color thermosensitive recording paper 2 mounted on the outer peripheral surface 5a of the platen drum 5 with a predetermined pressure. To do.

Between the magenta optical fixing device 14 and the yellow optical fixing device 15, a discharge passage 29 for discharging the color thermosensitive recording paper 2 on which the thermal recording has been completed with the outer wall surface of the reflector 19 as a part thereof. Is provided. This paper discharge path 2
9 is provided with a pair of transport rollers 30 for transporting the color thermosensitive recording paper 2 toward a gripping and discharging tray (not shown).

FIG. 7 shows an example of color thermosensitive recording paper. On the support 35, a cyan thermosensitive coloring layer 36,
A magenta thermosensitive coloring layer 37, a yellow thermosensitive coloring layer 38, and a protective layer 39 are sequentially formed. Each of these thermosensitive coloring layers 36 to 38 is layered from the surface in the order of thermal recording. For example, in the case of thermal recording in the order of magenta, yellow and cyan, the yellow thermosensitive coloring layer 38 and the magenta thermosensitive layer 38 are formed. The position of the coloring layer 37 is exchanged. As the support 35, an opaque coated paper or a plastic film is used, and when an OHP sheet is manufactured, a transparent plastic film is used.

The cyan thermosensitive coloring layer 36 contains an electron-donating dye precursor and an electron-accepting compound as main components, and develops cyan when heated. Magenta thermosensitive coloring layer 3
No. 7 contains a diazonium salt compound having a maximum absorption wavelength of about 365 nm, and a coupler which thermally reacts with this compound to develop magenta color. When the magenta thermosensitive coloring layer 37 is irradiated with ultraviolet rays in the vicinity of 365 nm after thermal recording, the diazonium salt compound is photodecomposed and the coloring ability is lost. The yellow thermosensitive coloring layer 38 has a maximum absorption wavelength of about 42.
It contains a diazonium salt compound having a thickness of 0 nm and a coupler which thermally reacts with the compound to develop a yellow color. When this yellow thermosensitive coloring layer 38 is irradiated with ultraviolet rays in the vicinity of 420 nm, it is photo-fixed and the coloring ability is lost.

FIG. 8 shows the coloring characteristics of the thermosensitive coloring layers 36 to 38. Color thermal recording paper 2 of this embodiment
The yellow thermosensitive coloring layer 38 has the highest thermal sensitivity, and the cyan thermosensitive coloring layer 36 has the lowest thermal sensitivity. Each thermosensitive coloring layer 3
The thermal energy for bringing 6 to 38 into a state immediately before color development is the bias thermal energy, and the thermal energy for actually developing the color is the gradation expression thermal energy. When the yellow Y pixel is subjected to thermal recording, color thermal energy obtained by adding gradation thermal energy GY to bias thermal energy BY is applied to the color thermal recording paper 2. Since magenta M and cyan C are the same, only symbols are attached.

FIG. 2 shows a heating element 21b for adjusting the friction coefficient.
It is a graph which shows an example of the heating method of. As shown in FIG. 8, since the coloring heat energy is relatively low in the heat recording of the yellow image, the color thermal recording paper 2 has a high friction coefficient.
In order to correct this, the heat generating element 21b outside the recording area 2b gives a constant heat energy indicated by reference numeral 42 to the color thermosensitive recording paper 2. This heat energy is smaller than the coloring heat energy of the yellow heat-sensitive coloring layer 38 indicated by reference numeral 43 (slightly larger than the bias heat energy BY).

In the thermal recording of the magenta image, since the coloring heat energy larger than that of the yellow image is applied, the friction coefficient of the color thermosensitive recording paper 2 becomes low. Therefore, the heating element 21b outside the recording area 2b generates heat energy that is slightly lower than that for the yellow image. Further, in the thermal recording of the cyan image, the applied thermal energy is the highest and the friction coefficient is the lowest, so the thermal energy generated by the heating element 21b outside the recording area 2b is set lower than that of the magenta image.

FIG. 1 shows changes in the friction coefficient of the surface of the color thermosensitive recording paper 2 when the thermosensitive coloring layers are thermally recorded. Reference numeral 45 indicates a friction coefficient in the recording area 2b,
The cyan thermosensitive coloring layer 36 having the highest coloring heat energy has the lowest friction coefficient. Reference numeral 46 denotes a friction coefficient outside the recording area 2b. As shown in FIG. 2, when the yellow image is thermally recorded, the heating element 21b outside the recording area 2b is heated to such an extent that the yellow thermosensitive coloring layer 38 does not develop color. The friction coefficient between the inside and the outside of the area 2a becomes close to each other, and the friction coefficient as a whole is as shown by reference numeral 47. The thermal recording of the magenta image and the thermal recording of the cyan image have almost the same friction coefficient as the thermal recording of the yellow image.

Next, the operation of the above embodiment will be described. When the print start switch is operated, the motor 10
Thus, the lever 11 rotates clockwise and slides the clamper 8 to form a gap between the claw 8b and the platen drum 5 into which the front end portion 2a of the color thermosensitive recording paper 2 can enter. Next, color thermal recording paper 2 at the top of the cassette
Is inserted into the conveyance roller 4 and is conveyed toward the platen drum 5 via the paper feed passage 3 as shown in FIG.
At the same time that the front end portion 2a of the color thermosensitive recording paper 2 comes into contact with the claw 8b of the clamper 8, the conveying roller 4 is temporarily stopped. Next, since the lever 11 is rotated counterclockwise by the motor 10, the clamper 8 is pulled back by the urging force of the spring 12, and the tip 2a is clamped between the clamper 8 and the outer peripheral surface 5a of the platen drum 5.

When the front end portion 2a of the color thermosensitive recording paper 2 is mounted on the platen drum 5, the stepping motor 7 is driven to rotate the platen drum 5. While the platen drum 5 rotates to wind the color thermosensitive recording paper 2 around the outer peripheral surface 5a, the clamper 8 moves to a position where the thermal head 13 passes. At this time, the thermal head 13 is kept at the position where the roller 24 contacts the notch 27a of the head cam 27 by the biasing force of the spring 25, so that the clamper 8 and the head body 20 do not come into contact with each other.

When the clamper 8 passes the position facing the thermal head 13, the head cam 27 rotates clockwise, and as shown in FIG. 5, the roller 24 is pushed on the outer periphery of the head cam 27 to move the thermal head 13 to the thermal recording position. . Since the spring 22 is provided between the head body 20 and the head holder 23, the head body 20 contacts the color thermosensitive recording paper 2 with an appropriate pressing force. Color thermal recording paper 2
When the leading end of the recording area reaches the position of the thermal head 13, the yellow image is thermally recorded line by line by the thermal head 13.

The thermal head 13 heats the heat generating element 21a in the recording area to the bias heat energy BY for bringing the heat generating element 21a into a state immediately before color development and the gradation expression heat energy GY corresponding to the color development temperature. On the other hand, the heating element 21b outside the recording area 2a generates heat energy lower than the coloring heat energy 43 of the yellow thermosensitive coloring layer 38 as shown by reference numeral 42 in FIG. Depending on the balance between the inside of the recording area and the outside of the recording area, the friction coefficient of the surface of the entire color thermosensitive recording paper 2 is as indicated by reference numeral 47 in FIG.

When the platen drum 5 further rotates and the portion on which the yellow image is thermally recorded reaches the yellow optical fixing device 15, the ultraviolet lamp 18 performs optical fixing.
The near-ultraviolet light having a wavelength of about 420 nm is irradiated onto the color thermosensitive recording paper 2 by the optical fixing device 15 for yellow, and the magenta thermosensitive coloring layer 37 is fixed so as not to develop yellow during thermal recording.

When the rotation of the platen drum 5 progresses and the leading end portion 2a of the color thermosensitive recording paper 2 sandwiched by the clamper 8 moves again to the position facing the thermal head 13,
The head cam 27 rotates counterclockwise, and the thermal head 13 is once moved to the retracted position shown in FIG. When the clamper 8 passes, the thermal head 13 returns to the thermal recording position shown in FIG. 5 by the head cam 27. The leading end of the color thermosensitive recording paper 2 which has reached the next thermal recording position is located below the thermal head 13, and thermal recording on the magenta thermosensitive coloring layer 37 is started.

The thermal head 13 applies thermal energy corresponding to the magenta image to the recording area 2a and thermal energy 42 shown in FIG. 2 to the outside of the recording area 2a for thermal recording. As a result, the coefficient of friction of the entire color thermosensitive recording paper becomes substantially the same as that at the time of thermal recording of the yellow image, so that the load on the platen drum 5 becomes substantially equal and the thermal recording position does not shift. During thermal recording of a magenta image, the yellow optical fixing device 15 is turned off, and the magenta optical fixing device 14 is turned on instead. As a result, the color thermosensitive recording paper 2 is irradiated with ultraviolet rays in the vicinity of 365 nm, and the cyan thermosensitive coloring layer 36 is optically fixed so that magenta will not be colored during the next thermal recording.

Next, the thermal head 13 passes through the clamper 8 in the same manner as described above, and then thermally records a cyan image on the cyan thermosensitive coloring layer 36 of the color thermosensitive recording paper 2. Thermal energy corresponding to cyan image data is applied to the inside of the recording area of the cyan thermosensitive coloring layer 36, and thermal energy indicated by reference numeral 42 in FIG. 2 is applied to the outside of the recording area. The yellow image and magenta image are almost the same as those used during thermal recording. Therefore, the thermal recording position of the cyan image does not shift. The cyan thermosensitive coloring layer 36 is not provided with optical fixing property because the coloring heat energy has a value that does not generate color in a normal storage state, but the color thermosensitive recording paper 2 on which a cyan image is thermally recorded is The ultraviolet light emitted from the magenta optical fixing device 14 is irradiated again to bleach.

When the platen drum 5 rotates and the clamper 8 faces the thermal head 13, the head cam 27
Rotates counterclockwise to release the thermal head 13 to the retracted position. Then, after the clamper 8 passes through the thermal head 13, the rotation of the platen drum 5 is stopped.

After the platen drum 5 is stopped, the paper discharging process is started. First, the motor 10 rotates to rotate the lever 11 in the clockwise direction, and the engaging portion 11b pushes the clamper 8 up to the paper discharge position shown in FIG. 6 to release the fixation of the front end portion 2a of the color thermosensitive recording paper 2. . At this time, since the pin 9 of the clamper 8 is engaged with the engaging portion 11b of the lever 11, the rotation is blocked at that position. On the other hand, head cam 2
7 rotates in the counterclockwise direction, and the notch 27b becomes the roller 24.
Since it abuts on the head main body 2 with a weaker force than during thermal recording
0 presses the color thermosensitive recording paper 2.

The color thermosensitive recording paper 2 pressed against the platen drum 5 by the head main body 20 rotates together with the platen drum 5, and its tip 2a moves away from the platen drum 5 by rigidity and enters the paper discharge passage 29. . The color thermosensitive recording paper 2 that has entered the paper discharge path 29 is conveyed by the transport roller 3
It is set to 0 and discharged to the paper output tray. Since the front end portion 2a of the color thermosensitive recording paper 2 is bleached even during this paper discharge,
The magenta optical fixing device 14 is turned on.

In the above embodiment, the heat-generating element outside the recording area is made to generate a certain amount of heat for each heat-sensitive coloring layer to balance with the friction coefficient in the recording area. Since the gradation expression heat energy applied to the range has a width of about 30 mJ / mm ² , the friction coefficient varies even within the same thermosensitive coloring layer. Therefore, the average value of the heat energy is obtained from the image data of each line that is heat-recorded at the same time, and the heating element outside the recording area is heated within the range lower than the coloring heat energy of the yellow image based on this average value. You may do it. As a result, the coefficient of friction is made uniform for each line, so that fluctuations in the coefficient of friction are further suppressed and the print quality can be further improved.

Further, in the above description, a platen drum type thermal printer using a large diameter platen drum was described as an example, but in the printing method of the present invention, the color thermosensitive recording paper is reciprocally moved with respect to a small diameter platen roller. It can also be used in a reciprocating thermal printer.

[0037]

As described above, in the thermal printing method of the present invention, the amount of deflection of the platen drum and the drive system for rotating the platen drum is changed by making the friction coefficients uniform for each thermosensitive coloring layer or for each row. Therefore, the thermal recording position shift is reduced, and the printing quality can be improved. Further, since the heating elements outside the recording area are constantly heated, it is possible to prevent the temperature of the heating elements at the edge of the recording area from lowering, and to eliminate the uneven print density.

[Brief description of drawings]

FIG. 1 is a graph showing the coefficient of friction on the surface of a color thermosensitive recording paper.

FIG. 2 is a graph showing an example of heat generation of a heat generating element outside a recording area.

FIG. 3 is a schematic diagram of a thermal printer showing a paper feeding state.

FIG. 4 is an explanatory diagram showing a positional relationship between a head body and a color thermosensitive recording paper.

FIG. 5 is a schematic diagram of a thermal printer showing a thermal recording state.

FIG. 6 is a schematic diagram of a thermal printer showing a discharged state.

FIG. 7 is an explanatory diagram showing a layer structure of color thermosensitive recording paper.

FIG. 8 is a graph showing the color development characteristics of each thermosensitive color development layer.

[Explanation of symbols]

 2 color thermal recording paper 2b recording area 5 platen drum 8 clamper 13 thermal head 20 head body 21 heating element array 21a heating element for recording 21b heating element for friction coefficient correction

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B41J 3/20 116

Claims (2)

[Claims] 1. A plurality of thermosensitive coloring layers are sequentially layered on a support, and the lower thermosensitive coloring layer has higher coloring heat energy,
In addition, the color thermal recording paper in which the frictional resistance of the surface becomes lower as the applied thermal energy is higher and the thermal head having the heating element array extending in the main scanning direction is used, and the color thermal recording paper and the thermal head are connected in the sub-scanning direction. Relative to
Thermal recording in order from the thermosensitive coloring layer of the upper layer, in the thermal printing method of thermally recording a color image in the recording area of the color thermosensitive recording paper, using a thermal head having a heating element row longer than the recording area, When a heating element in the recording area is driven to record a color image, the heating elements outside the recording area that are not involved in thermal recording are also driven at the same time, so that the uppermost thermosensitive coloring layer does not develop color. A thermal printing method characterized in that the thermal energy of which the higher the color forming layer is, is applied to the color thermal recording paper. 2. A plurality of thermosensitive coloring layers are sequentially layered on a support, and the lower thermosensitive coloring layer has higher coloring heat energy,
In addition, the color thermal recording paper in which the frictional resistance of the surface becomes lower as the applied thermal energy is higher and the thermal head having the heating element array extending in the main scanning direction is used, and the color thermal recording paper and the thermal head are connected in the sub-scanning direction. Relative to
Thermal recording in order from the thermosensitive coloring layer of the upper layer, in the thermal printing method of thermally recording a color image in the recording area of the color thermosensitive recording paper, using a thermal head having a heating element row longer than the recording area, When a color image is recorded by driving the heating elements in the recording area, the heating elements outside the recording area that are not involved in thermal recording are also driven at the same time, and the uppermost thermosensitive coloring layer does not develop a color while recording. A thermal printing method, characterized in that the higher the average thermal energy of one line, the smaller thermal energy is applied to the color thermal recording paper.