JPH11320938A - Color thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve print quality by stabilizing a conveying amount of a recording paper and preventing loosened winding of a roll of the recording paper due to lacking of a back tension caused by variation of a load of the roll of the recording. SOLUTION: A pair of relaying rollers 11 are provided between a paper supplying roller 4 and a pair of conveying roller 13. The speeds of the relaying rollers 11 are lower than those of the paper supplying roller 4 and the conveying rollers 13. When paper is supplied, a back tension is applied between the pair of relaying rollers 11 and the pair of conveying rollers 13, thereby stabilizing a conveying amount of the color thermal recording paper 2. When the printing is executed, a sag of the recording paper is generated between the pair of relaying rollers 11 and the pair of conveying rollers 13, thereby sucking variation of a load of the roll 3 of the recording paper. A back tension is applied between the paper supplying roller 4 and the relaying rollers 11 so that the color thermal recording paper 2 is wound back to the roll of the recording paper without generating the loosened winding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color thermal printer, and more particularly, to an improvement in a color thermal printer for recording a color image on a roll of recording paper.

[0002]

2. Description of the Related Art Some color thermal printers use a recording paper roll in which a long recording paper is wound in a roll shape in order to use recording paper without waste by reducing margins. Also, a color thermal printer using a recording paper roll heats three-color images in a plane-sequential manner with one thermal head while reciprocating the recording paper between a direction in which the recording paper is pulled out from the recording paper roll and a direction in which the recording paper is rewound. There is something to record. This type of color thermal printer has the advantage that the apparatus can be made compact and the size of the print can be set freely in the longitudinal direction of the recording paper.

In the above-described color thermal printer, a predetermined amount of recording paper is pulled out of the recording paper roll by a paper feed roller contacting the outer periphery of the recording paper roll, and the pulled out recording paper is conveyed by a capstan roller and a pinch roller. The sheet is nipped by a pair of rollers, and is reciprocated in a direction of pulling out from the recording paper roll and a direction of rewinding the recording paper roll.
Then, when the transport roller pair transports the recording paper in the rewinding direction, an image of a specific color is thermally recorded on the recording paper by the thermal head.

In the conveyance of the recording paper by the conveyance roller pair, the recording paper is wound around a part of the outer periphery of the capstan roller in order to prevent slippage and obtain a sufficient conveyance force. The improvement of the conveying force by this winding is generally called a winding effect, and the winding angle changes according to the back tension applied to the recording paper, so that the conveyance amount of the recording paper also changes.

[0005]

However, in the above-described color thermal printer, the back tension is not applied to the recording paper when the recording paper is conveyed in the pull-out direction by the pair of conveying rollers, so that the winding effect is reduced and the rewinding direction is reduced. When the paper is transported to the printer, thermal recording by the thermal head applies an appropriate back tension to the recording paper.
There has been a problem that the conveyance amount of the recording paper changes between the time of paper feeding and the time of printing. In color thermal printers, in which recording paper is reciprocated and thermal recording is performed by superimposing multiple color images, especially color thermal printers that detect the amount of transport of the recording paper from the amount of rotation of the rollers, misregistration of each color registration occurs. This causes a problem that print quality is deteriorated.

In order to solve the above problem, there is a method in which the recording paper transport speed of the paper feed roller is made slower than that of the pair of transport rollers to apply a back tension to the recording paper even during paper feeding. Since no back tension is applied to the recording paper when the recording paper is rewound, the recording paper roll is loosened and becomes susceptible to moisture, or the recording paper is skewed during paper feeding.

Another problem specific to a printer using a recording paper roll is that a load variation of the recording paper roll is transmitted to a pair of conveying rollers and a thermal head, thereby causing a color shift, a white stripe, a black stripe, and the like. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and stabilizes the amount of recording paper transported during paper feeding and printing, thereby causing adverse effects due to fluctuations in the load on the recording paper roll and winding of the recording paper roll. An object of the present invention is to improve print quality by preventing loosening.

[0009]

In order to solve the above problems, a color thermal printer according to the present invention comprises a pair of relay rollers for nipping and reciprocating the recording paper between a paper feeding roller and a conveying roller pair. Are arranged, and the recording paper conveyance speed of these rollers is such that a pair of a feeding roller and a pair of a conveyance roller> a pair of a relay roller.

Further, by forming the relay roller pair with a slippery material or weakening the nip force of the relay roller pair, when the recording paper is pulled, it slips between the relay roller pair and the recording paper. It was done.

Further, as the recording paper, a color thermosensitive recording paper in which at least three thermosensitive coloring layers are laminated on a support is used, and an optical fixing device for fixing the thermosensitive coloring layer is provided facing the color thermosensitive recording paper. It is a thing.

[0012]

FIG. 2 schematically shows a color thermal printer embodying the present invention. In this color thermal printer, a long color thermal recording paper 2 is used. The color thermal recording paper 2 is set in a color thermal printer as a recording paper roll 3 wound into a roll. A paper feed roller 4 is in contact with the outer peripheral surface of the recording paper roll 3, and is driven by a pulse motor 6 via a paper feed transmission mechanism 5. When the paper feed roller 5 rotates clockwise in the drawing, the recording paper roll 3 rotates counterclockwise in the drawing, and the color thermosensitive recording paper 2 is sent out from the recording paper roll 3. Conversely, when the paper feed roller 4 is rotated counterclockwise in the figure, the recording paper roll 3 is rotated clockwise in the figure, and the color thermosensitive recording paper 2 is rewound on the recording paper roll 3.

When the color thermosensitive recording paper 2 is fed from the recording paper roll 3, the diameter of the recording paper roll 3 is reduced, but the paper feed roller 4 is movable in the direction in which it comes into contact with the recording paper roll 3. In addition, since the spring is biased so as to reliably contact the recording paper roll 3, the color thermosensitive recording paper 2 can be reliably fed regardless of the diameter of the recording paper roll 3. Further, the recording paper roll 3 may be movable in a direction approaching the paper feed roller 4 without moving the paper feed roller 4.

As is well known, the color thermosensitive recording paper 2 has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer sequentially formed on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with small heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large thermal energy. The yellow thermosensitive coloring layer has a thickness of 420 nm.
When near ultraviolet rays are irradiated, the color developing ability is lost.
The magenta thermosensitive coloring layer develops magenta color with a thermal energy approximately between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and loses its coloring ability when irradiated with 365 nm ultraviolet rays. For example, the color thermosensitive recording paper 2 may be provided with a black thermosensitive coloring layer to form a four-layer structure.

A capstan roller 9 driven by a pulse motor 6 via a relay transmission mechanism 8 is provided downstream of the color thermosensitive recording paper 2 by the paper feed roller 4 in the feeding direction.
A relay roller pair 11 composed of a pinch roller 10 movable between a position where the capstan roller 9 is pressed against and a position away from the capstan roller 9 is disposed. Pinch roller 10
Is constantly pressed against the capstan roller 9 by being biased by a spring 29. When the paper is fed, the capstan roller 9 is pressed against the bias of the spring 29 by a cam or a solenoid.
Moved away from The relay roller pair 11 sandwiches the color thermosensitive recording paper 2 sent out by the paper feed roller 4, and feeds the color thermosensitive recording paper 2 from the recording paper roll 3 by rotation of the capstan roller 9, and a recording direction. The color thermosensitive recording paper 2 is reciprocated in a printing direction in which the color thermosensitive recording paper 2 is rewound on the paper roll 3.

A transport roller pair 13 is disposed downstream of the relay roller pair 11 in the sheet feeding direction. The transport roller pair 13 is disposed below the color thermal recording paper 2, and is disposed above the capstan roller 15 driven by the pulse motor 6 via the transport transmission mechanism 14, and above the color thermal recording paper 2. A pinch roller 16 pressed against the capstan roller 15 by a cam, a solenoid, or the like.
The transport roller pair 13 sandwiches the color thermal recording paper 2 by pressing the pinch roller 16, and reciprocates the thermal color recording paper 2 in the paper feeding direction and the printing direction by the rotation of the capstan roller 15. The transport amount of the color thermal recording paper 2 is measured by the pinch roller 15 of the transport roller pair 13.
This is performed by detecting the number of rotations by an encoder or the like.

On the downstream side of the feed roller pair 4 in the paper feeding direction,
A thermal head 18 is provided. The thermal head 18 includes a heating element array 18a in which a number of heating elements are arranged in a line, and is fixed in the printer. At a position facing the thermal head 18, a platen roller 19 is arranged so as to sandwich the color thermosensitive recording paper 2. The platen roller 19 is movable in the vertical direction, and is urged by a spring (not shown) in a direction in which the platen roller 19 comes into pressure contact with the thermal head 18. When the color thermosensitive recording paper 2 is transported in the printing direction by the transport roller pair 13, the thermal head 18
a is heated to a predetermined temperature, and the respective thermosensitive coloring layers of the color thermosensitive recording paper 2 are colored. The platen roller 19 rotates following the conveyance of the color thermosensitive recording paper 2, and is lowered by a cam, a solenoid or the like at the time of paper feeding and paper discharging to form a gap with the thermal head 18.

An optical fixing device 21 is disposed downstream of the thermal head 18 in the paper feeding direction so as to face the color thermosensitive recording paper 2. The optical fixing device 21 includes a yellow ultraviolet lamp 22, a magenta ultraviolet lamp 23, and a reflector 24. The ultraviolet lamp for yellow 22 emits near ultraviolet light having an emission peak of 420 nm, and the ultraviolet lamp for magenta emits ultraviolet light having an emission peak of 365 nm. And these ultraviolet lamps 22 and 23 are
The yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer of the color thermosensitive recording paper 2 are fixed so as not to develop a color even when heated.

At the downstream side of the optical fixing unit 21 in the paper feeding direction, there is provided a discharge port 26 for discharging the color thermosensitive recording paper 2 on which printing has been completed to the outside of the apparatus. The print completed portion of the color thermosensitive recording paper 2 is discharged from the discharge port 26 by the transport roller pair 13. Immediately thereafter, a cutter 27 arranged at the back of the discharge port 26 cuts the color thermosensitive recording paper 2 at a predetermined position. Thereby, the user can obtain the sheet-shaped color thermosensitive recording paper 2.

Although not shown to prevent the drawing from becoming complicated, a guide member for guiding the color thermosensitive recording paper 2 is appropriately provided in the printer, and the color paper fed from the recording paper roll 3 is provided. The thermal recording paper 2 is transported along the guide member between the relay roller pair 11, the transport roller pair 13, the thermal head 18 and the platen roller 19, below the optical fixing device 21, and to the discharge port 26.

The paper feed transmission mechanism 5, the relay transmission mechanism 8, and the transport transmission mechanism 14 are composed of, for example, pulleys, belts, and the like, and are set to have different reduction ratios. These transmission mechanisms 5, 8, 14
Of the feed roller 4 and the relay roller pair
In consideration of the diameter of the capstan roller 9 and the diameter of the capstan roller 15 of the transport roller pair 13, the peripheral speed of each of the rollers 4, 9, and 15, that is, the transport speed of the color thermosensitive recording paper 2 is changed to Paper roller 4 ≒ Transport roller pair 13>
The relay roller pair 11 is set.

As described above, if the transport speed of the relay roller pair 11 is set to be lower than that of the feed roller 4 and the transport roller pair 13, when the color thermosensitive recording paper 2 is fed, the relay roller pair 13 A proper back tension is applied to the color thermal recording paper 2 from the difference in the transport speed between the roller pair 11. Thereby, the transport roller pair 13
The effect of winding the color thermosensitive recording paper 2 around the capstan roller 15 is improved, and the transport amount of the color thermosensitive recording paper 2 is stabilized. Conventionally, color thermal recording paper 2 at the time of printing is used.
The misalignment that has occurred with the carry amount is eliminated, and registration deviation can be prevented to improve print quality.

As shown in FIG. 1, during printing, a slack is formed between the relay roller pair 11 and the transport roller pair 13. Thus, the load fluctuation of the recording paper roll 3 can be absorbed by the slack portion and not transmitted to the transport roller pair 13 and the thermal head 18 and the like.
The occurrence of misregistration, black streaks, white streaks, and the like can be prevented. Further, since the transport speed of the transport roller pair 13 and the transport speed of the paper feed roller 4 are substantially the same, the slack amount can be kept constant. Further, between the recording paper roll 3 and the relay roller pair 11, an appropriate back tension is applied to the color thermal recording paper 2, so that the color thermal recording paper 2 can be wound around the recording paper roll 3 without loosening, It is possible to prevent an increase in the humidity of the color thermosensitive recording paper 2 and skew during conveyance.

The color thermosensitive recording paper 2 nipped by the relay roller pair 11 is supplied to the feed roller 4 and the transport roller pair 1
When the relay transmission mechanism 8 is pulled, the load is constantly applied to the relay transmission mechanism 8, and the service life of the relay transmission mechanism 8 is shortened. Therefore, in the present embodiment, the urging force of the spring 29 that presses the pinch roller 10 of the relay roller pair 11 against the capstan roller 9 is set to be weak. As a result, the color thermosensitive recording paper 2 is transported by the pair of transport rollers 1.
3 and the feed roller 4, the relay roller pair 11
Is slipped with respect to the color thermosensitive recording paper 2, the load on the relay transmission mechanism 8 is reduced. Instead of weakening the biasing force of the spring 29 of the pinch roller 10, the pinch roller 10 and the capstan roller 9 may be made of a material that is slippery, such as polyoxymethylene (POM) or plastic mixed with a sliding material. It may be formed.

Next, the operation of the above embodiment will be described. As shown in FIG. 2, when a printing start operation is performed in the color thermal printer, the pulse motor 6 starts rotating. The rotation of the pulse motor 6 is controlled by the paper feed transmission mechanism 5, the relay transmission mechanism 8, and the transport transmission mechanism 14.
Are transmitted to the paper feed roller 4, the relay roller pair 11, and the transport roller pair 13. At the start of printing,
The pinch roller 10 of the relay roller pair 11 is moved to a position away from the capstan roller 9 against the bias of the spring 29, and the pinch roller 1
6 has been moved to a position away from the capstan roller 15. The platen roller 19 is also used for the thermal head 1.
8, and the path of the color thermosensitive recording paper 2 is open.

The paper feed roller 4 rotates in the clockwise direction in the figure to feed the color thermosensitive recording paper 2 from the recording paper roll 3. The color thermosensitive recording paper 2 sent out from the recording paper roll 3 is sent between the pinch roller 10 and the capstan roller 9 of the relay roller pair 11 arranged on the downstream side in the paper feeding direction. When a sensor (not shown) detects that the color thermosensitive recording paper 2 has passed between the pinch roller 10 and the capstan roller 9 of the relay roller pair 11, the pinch roller 10 is moved to a position away from the capstan roller 9. The driving of the cam and the solenoid is stopped, and the pinch roller 10 sandwiches the color thermosensitive recording paper 2 between the pinch roller 10 and the capstan roller 9 by the bias of the spring 29.

The relay roller pair 11 transports the color thermosensitive recording paper 2 toward the transport roller pair 13 by the rotation of the capstan roller 9 driven by the pulse motor 6 via the relay transmission mechanism 8. At this time, the relay roller pair 1
1 is set lower than the conveyance speed of the paper feed roller 4, the color thermosensitive recording paper 2 between the paper feed roller 4 and the relay roller pair 11 sags.

When a sensor (not shown) detects that the color thermosensitive recording paper 2 has passed between the pinch roller 16 and the capstan roller 15 of the transport roller pair 13,
The cam or the solenoid starts driving, moves the pinch roller 16 to a position where the pinch roller 16 is pressed against the capstan roller 15, and sandwiches the color thermosensitive recording paper 2 between the pinch roller 16 and the capstan roller 15. The transport roller pair 13 is
The rotation of the capstan roller 15 driven by the pulse motor 6 via the transfer mechanism 14 transfers the color thermosensitive recording paper 2 to the thermal head 18 and the platen roller 1.
9 is conveyed. Also, the pinch roller 16
Rotates following the movement of the color thermosensitive recording paper 2,
The number of rotations of the pinch roller 16 is detected by an encoder and used for measuring the transport amount of the color thermosensitive recording paper 2.

When the color thermal recording paper 2 starts to be transported by the transport roller pair 13, the transport speed of the relay roller pair 11 is set to be lower than the transport speed of the transport roller pair 13. Back tension is applied to the color thermosensitive recording paper 2 between the relay roller pair 11 and the transport roller pair 13 by being pulled by the transport roller pair 13. As a result, the effect of winding between the color thermal recording paper 2 and the capstan roller 15 of the transport roller pair 13 is stabilized, and the transport amount of the color thermal recording paper 2 according to the rotation speed of the pinch roller 16 of the transport roller pair 13 is stabilized. Detection is also stable.

Since the urging force of the spring 29 for urging the pinch roller 10 is set to be weak in the relay roller pair 11, when the color thermosensitive recording paper 2 is pulled by the transport roller pair 13, the relay roller pair 11 Slips against the color thermosensitive recording paper 2. Thereby, the load applied to the relay transmission mechanism 8 can be reduced.

The color thermosensitive recording paper 2 includes a thermal head 1
8 and between the platen roller 19 and further conveyed in the sheet feeding direction. Pinch roller 16 of transport roller pair 13
When it is confirmed from the number of rotations that the color thermosensitive recording paper 2 has been conveyed by a predetermined amount in the paper feeding direction, the rotation of the pulse motor 6 is stopped, and the driving of the cams and solenoids, etc., which lowered the platen roller 19 Is stopped. As a result, the platen roller 19 is raised by the bias of a spring (not shown), and the color thermosensitive recording paper 2 is sandwiched between the platen roller 19 and the thermal head 18.

Next, the pulse motor 6 rotates in the reverse direction,
The transport roller pair 13, the relay roller pair 11, and the
The paper feed roller 4 is rotated in the reverse direction. As a result, as shown in FIG. 1, the color thermosensitive recording paper 2 is conveyed in the printing direction on the left side in the figure. When the leading end of the recording area of the color thermosensitive recording paper 2 reaches the thermal head 18, the heating element array 12a generates heat and heats the recording area to thermally record a yellow image line by line on the yellow thermosensitive coloring layer.

As described above, when the color thermosensitive recording paper 2 is conveyed in the printing direction, an appropriate back tension is applied to the color thermosensitive recording paper 2 by the pressure contact of the thermal head 18, so that the color thermosensitive recording paper 2 is conveyed. The winding effect between the roller pair 13 and the capstan roller 15 is stabilized. In addition, there is no large difference in the transport amount of the color thermal recording paper 2 between the transport of the color thermal recording paper 2 in the paper feeding direction and the transport of the color thermal recording paper 2 in the printing direction. Obtainable.

When the color thermosensitive recording paper 2 is transported in the printing direction, a difference in the transport speed between the paper feed roller 4 and the relay roller 11 causes a difference between the paper feed roller 4 and the relay roller pair 11.
A back tension is applied to the color thermosensitive recording paper 2 between. As a result, the color thermosensitive recording paper 2 is rewound to the recording paper roll 3 without loosening, and the influence of moisture on the color thermosensitive recording paper 2 and skew during conveyance can be prevented. Further, the color thermosensitive recording paper 2 between the relay roller pair 11 and the transport roller pair 13 sags. Due to this slack, load fluctuations of the recording paper roll 3 and the relay roller pair 11 and the like are absorbed and not transmitted to the transport roller pair 13, so that registration deviation, black stripes, and white stripes due to load fluctuations are prevented, and high quality is achieved. Prints can be created.

When the thermal recording of the yellow image is completed up to the rear end of the recording area of the color thermal recording paper 2, the pulse motor 6
Stops. The platen roller 19 is lowered to a position away from the thermal head 18 by a cam, a solenoid, or the like. Next, as shown in FIG. 2, the pulse motor 6 rotates in the forward direction again, and feeds the paper feed roller 4 via the paper feed transmission mechanism 5, the relay transmission mechanism 8, and the transport transmission mechanism 14.
Then, the color thermosensitive recording paper 2 is transported in the paper feeding direction by rotating the relay roller pair 11 and the transport roller pair 13. Simultaneously with the conveyance in the paper feeding direction, the yellow ultraviolet lamp 22 of the optical fixing device 21 is turned on to fix the yellow thermosensitive coloring layer in the recording area of the color thermosensitive recording paper 2. When the color thermosensitive recording paper 2 is conveyed when the yellow thermosensitive coloring layer is fixed, the color thermosensitive recording paper 2 between the conveying roller pair 13 and the relay roller pair 11 is also given an appropriate back tension. The transport amount of the color thermosensitive recording paper 2 by the roller pair 13 does not change.

When the fixing of the yellow thermosensitive coloring layer in the recording area of the color thermosensitive recording paper 2 is completed, the rotation of the pulse motor 6 is stopped, and the driving of the cam, the solenoid, etc., which lowered the platen roller 19, is stopped. . The platen roller 19 is raised by the urging of a spring (not shown), and sandwiches the color thermosensitive recording paper 2 with the thermal head 18. Further, the pulse motor 6 rotates in the reverse direction to rotate the transport roller pair 13, the relay roller pair 11, and the paper feed roller 4 via the transport transmission mechanism 14, the relay transmission mechanism 8, and the paper transmission mechanism 5. Rotate in the direction. As shown in FIG. 1, the color thermosensitive recording paper 2 is conveyed in the printing direction, and when the leading end of the recording area reaches the thermal head 18, the heating element array 12a starts to generate heat and the magenta thermosensitive coloring layer forms a magenta color. The image is thermally recorded line by line.

When the color thermosensitive recording paper 2 is conveyed during the thermal recording of the magenta image, an appropriate back tension is applied to the color thermosensitive recording paper 2 by the pressing of the thermal head 18. The conveyance of the thermal recording paper 2 is stabilized. Further, due to the back tension between the paper feed roller 4 and the relay roller pair 11, the color thermosensitive recording paper 2 is rewound onto the recording paper roll 3 without loosening.
Furthermore, the color thermosensitive recording paper 2 between the relay roller pair 11 and the transport roller pair 13 sags, and a load change is not transmitted to the transport roller pair 13 due to the sag.

When the magenta image thermal recording is completed up to the rear end of the recording area of the color thermal recording paper 2, the pulse motor 6
Stops. The platen roller 19 is lowered to a position away from the thermal head 18 by a cam, a solenoid, or the like. As shown in FIG. 2, the pulse motor 6 rotates in the forward direction again, and via the transmission mechanisms 5, 8, and 14, the sheet feed roller 4, the relay roller pair 11, and the transport roller pair 13
Is rotated to convey the color thermosensitive recording paper 2 in the paper feeding direction. At the same time as the conveyance in the paper feeding direction, the optical fixing device 2
The magenta ultraviolet lamp 22 is turned on to fix the magenta thermosensitive coloring layer in the recording area of the color thermosensitive recording paper 2.

When the color thermosensitive recording paper 2 is conveyed at the time of fixing the magenta thermosensitive coloring layer, an appropriate back tension is applied to the color thermosensitive recording paper 2 between the conveying roller pair 13 and the relay roller pair 11. The transport of the color thermosensitive recording paper 2 by the transport roller pair 13 is stabilized.

When the fixing of the magenta thermosensitive coloring layer in the recording area of the color thermosensitive recording paper 2 is completed, the rotation of the pulse motor 6 is stopped, and the driving of the cam and the solenoid, etc., which lowered the platen roller 19, is stopped. . The platen roller 19 is raised by the urging of a spring (not shown), and sandwiches the color thermosensitive recording paper 2 with the thermal head 18. Further, the pulse motor 6 rotates in the reverse direction, and rotates the pair of transport rollers 13, the pair of relay rollers 11, and the paper feed roller 4 in the reverse direction via the transmission mechanisms 14, 8, and 5. As shown in FIG. 1, the color thermosensitive recording paper 2 is conveyed in the printing direction, and when the leading end of the recording area reaches the thermal head 18, the heating element array 12a starts to generate heat, and the cyan thermosensitive coloring layer forms a cyan image. Is thermally recorded line by line.

Color thermal recording paper 2 during thermal recording of cyan image
In the conveyance of the recording paper, an appropriate back tension is applied to the color thermosensitive recording paper 2 by the pressing of the thermal head 18, so that the conveyance of the color thermosensitive recording paper 2 by the conveyance roller pair 13 is stabilized. Also, the feed roller 4 and the relay roller pair 1
Due to the back tension between the recording paper roll 1 and the recording paper roll 3, the color thermosensitive recording paper 2 is rewound onto the recording paper roll 3 without loosening. Furthermore, the color thermosensitive recording paper 2 between the relay roller pair 11 and the transport roller pair 13 sags, and a load change is not transmitted to the transport roller pair 13 due to the sag.

When the thermal recording of the cyan image is completed to the rear end of the recording area of the color thermosensitive recording paper 2, the pulse motor 6 is stopped, and the platen roller 19 is lowered to a position away from the thermal head 18 by a cam or a solenoid. .
Next, as shown in FIG. 2, the pulse motor 6 rotates in the forward direction again to convey the color thermosensitive recording paper 2 in the paper feeding direction.
Since the cyan thermosensitive coloring layer has a coloring property that does not develop a color in a normal storage state, the cyan thermosensitive coloring layer is not fixed by light and the color thermosensitive recording paper 2 is discharged from the outlet 26 as it is.

When the printed portion of the color thermosensitive recording paper 2 is discharged out of the apparatus, the pulse motor 6 is stopped. Then, the cutter 27 is operated to cut the color thermosensitive recording paper 2 to form a sheet-shaped color print. The color print obtained by the color thermal printer of the present embodiment is of high quality without color shift, white streaks, and black streaks.

When printing is not to be continued, the color thermosensitive recording paper 2 is rewound to the recording paper roll 3 for moisture proofing. Since the back tension is applied to the recording paper roll 2, the color thermosensitive recording paper 2 is rewound onto the recording paper roll 3 without loosening. As a result, the color development characteristics of the color thermosensitive recording paper 2 do not change due to moisture, and a color print having an appropriate color tone can be obtained.

Although the above embodiment has been described with respect to a color thermal printer, the present invention can also be applied to a sublimation type or a thermal fusion type thermal transfer printer using yellow, magenta and cyan color ink sheets. In the case of these thermal transfer printers, no optical fixing device is required.

The recording paper roll is set directly in the printer. However, a recording paper magazine loaded with the recording paper roll or a recording paper magazine loaded with the recording paper roll incorporating a paper feed roller is used. The present invention can be applied to a printer in which is set.

[0047]

As described above, according to the color thermal printer of the present invention, the conveyance amount of the recording paper at the time of paper feeding and printing is made constant, and the load fluctuation of the recording paper roll is controlled by the conveying roller pair. Since it is possible to prevent transmission to the thermal head or the like, it is possible to create a high-quality print without color shift or the like. In addition, when the recording paper is rewound, the recording paper can be rewound onto the recording paper roll without loosening, so that the adverse effect of moisture on the recording paper and skew during recording paper conveyance can be prevented.

[Brief description of the drawings]

FIG. 1 is an outline view showing a state of a color thermal printer embodying the present invention at the time of printing.

FIG. 2 is a schematic diagram showing a state of a color thermal printer when paper is fed.

[Explanation of symbols]

 2 color thermal recording paper 3 recording paper roll 4 paper feed roller 5 paper feed transmission mechanism 8 relay transmission mechanism 11 relay roller pair 13 transport roller pair 14 transport transmission mechanism 18 thermal head 21 optical fixing device

Claims (4)

[Claims] 1. A recording paper roll in which a long recording paper is wound in a roll form, a paper feed roller for sending and rewinding the recording paper from the recording paper roll, and a recording paper supplied between the recording paper roll. A transport roller pair for performing a plurality of reciprocal transports in the direction of pulling out and rewinding from the recording paper roll, and a transport roller pair disposed downstream of the transport roller pair in the recording paper withdrawal direction and rewinding the recording paper by the transport roller pair In a color thermal printer including a thermal head that thermally records a specific color on recording paper when the paper is transported in the direction, the recording paper is reciprocated by sandwiching the recording paper between the paper feed roller and the transport roller pair. A relay roller pair is arranged, and the recording paper transport speed of these rollers is set to a value between a feed roller and a transport roller pair.
A color thermal printer comprising a pair of relay rollers. 2. The color thermal printer according to claim 1, wherein the relay roller pair is formed of a slippery material, and slips between the recording paper and the recording paper when the recording paper is pulled. 3. The color thermal printer according to claim 1, wherein the nip force of the relay roller pair is such that when the recording paper is pulled, the nip force slips between the relay roller pair and the recording paper. 4. The recording paper according to claim 1, wherein the recording paper has at least three
It is a color thermosensitive recording paper on which a thermosensitive coloring layer of color is laminated,
4. The color thermal printer according to claim 1, further comprising an optical fixing device for fixing the thermosensitive coloring layer facing the color thermosensitive recording paper.