JPH11240654A - Paper carriage mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry recording paper precisely and also prevent color drifts and color blurs for color image recording by gripping the recording paper tight without causing any existent harmful effects such as out-of-register adversely. SOLUTION: A paper carriage mechanism for use in a printer delivers recording paper with its carriage device made up of a pair of rollers, such as a capstan roller and a pinch roller, from image recording where images are recorded on the recording paper inputted at the paper feed side through paper ejection where it is ejected out. The paper carriage mechanism concretely comprises a capstan roller 1A having all over its surface arrayed projections 3 with a height of 60±40 μm, preferably 55±5 μm, as well as a pitch of 0.5±0.2 mm, a pinch roller 2A of high rubber hardness as a roller pair to the capstan roller 1A, and a backup roller 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device, and more particularly to a sheet conveying mechanism for preventing a registration deviation (hereinafter, abbreviated as "registration") of a thermal printer.

[0002]

2. Description of the Related Art Paper transport of a conventional thermal printer is as follows.
Three types of driving methods have been mainly performed: a grip roller driving method, a platen roller driving method, and a drum driving method.
Among them, a printer having a relatively large A3 paper size employs a grip roller system as shown in FIG. In FIG. 15, reference numeral 101 denotes a platen roller facing the thermal head 100, which rotates counterclockwise to convey the paper 103, and is guided by the recording paper 103 and the guide roller 104 with a predetermined pressure on the thermal head 100. The toner ribbon 102 is pressed, and the capstan roller 105 and the pinch roller 1 are further pressed.
A transport device having a strong gripping force is configured by the roll pair 06 to transport the paper 103 from recording to discharge. The backup roller 107 is for adjustment.

[0003]

However, especially in a case where a plurality of images are superimposed and recorded one by one in color recording, the registration (+) mark as shown in FIG. As a result of performing the (alignment) confirmation, if the conveyance accuracy of the paper conveyance device is not sufficient, a so-called misregistration state occurs, and the inconsistency or blurring of the color occurs.

[0004] As a measure for improving the conveyance accuracy of the recording paper conveyed by such a grip roller drive system, the surface configuration of the capstan roller 105 is devised (such as a random roller for spraying a yosha). To increase the friction with the front surface of the paper 103 by devising the surface material of the pinch roller 106, or by increasing the pressing pressure to increase the frictional force while maintaining the same friction coefficient. And other measures were taken. FIG.
FIG. 18A is a diagram showing the state of the surface of a conventional capstan roller, i.e., a roller, FIG. 18A is an enlarged view of the surface of the roller, and FIG. As can be seen from the figure, the unevenness of the surface of the roller was random, and was insufficient for reliable conveyance.

Further, as in a grip belt system shown in FIG. 17, a roller pair is changed to a belt shape, and a capstan belt 110 is wrapped around a pair of rollers 108 and 109,
The pinch belt 113 is wrapped around a pair of rollers 111 and 112 so as to increase the contact area of the sheet conveyance,
Improvement measures such as gaining friction have been taken.

[0006] However, none of the above-mentioned methods has reached a decisive method for improving registration accuracy. The reason is that in the above-mentioned conventional example, the capstan roller 105 and the pinch roller 1 of the grip roller type are used.
This is because there is a limit only to the device of the surface 06. In addition, if the pressing pressure is increased, the axis of the grip roller is bent, and it becomes impossible to apply a uniform pressure.
Therefore, the center can be pressed down by using the backup roller 107 or a split-type comb-shaped roller, but in this case, there is a problem that the adjustment is delicate and a sufficient effect cannot be exerted. Also, even if you try to gain frictional force by making the grip roller a belt shape,
Although the contact area of the belt becomes large, there is a problem that the effect is substantially the same as that obtained when the grip roller has two stages.

Accordingly, the present invention prevents color shift and bleeding in the case of a color image by gripping and accurately transporting a recording sheet without causing the adverse effects of the conventional method, thereby preventing a monochrome image from being damaged. It is an object of the present invention to provide a paper transport mechanism of a printer capable of improving the dimensional accuracy of a printer.

[0008]

According to a first aspect of the present invention, there is provided a sheet conveying mechanism for conveying a sheet by a capstan roller and a pinch roller as a roller pair of the capstan roller. The capstan roller is a capstan roller in which projections having a height of 60 ± 40 μm and a projection pitch of 0.5 ± 0.2 mm in the axial direction are arranged in an area of half or more of the surface, and the hardness of the pinch roller is determined. It is characterized by high hardness. In the ninth aspect, the hardness of the pinch roller is specifically 55 to 85 ° (the hardness is JISK-6301A).
(Measured by a hardness meter). According to this configuration, in the paper transport apparatus of the grip roller type using the capstan roller and the pinch roller, it is possible to enhance the gripping force and perform the accurate paper transport with high transport accuracy.

According to a second aspect of the present invention, in the paper transport mechanism of the first aspect, the height of the projections arranged on the surface of the capstan roller is 60 ± 15 μm. According to this configuration, accurate paper conveyance can be performed while maintaining a strong gripping force by an optimal frictional force.

According to a third aspect of the present invention, in the paper transport mechanism of the first aspect, the protrusion on the surface of the capstan roller is set to be zero with respect to the axial direction of the surface of the capstan roller.
In this case, the invention described in claim 4 is characterized in that one or two rows of the projections are always in contact with a pinch roller. The invention according to claim 5 is characterized in that the projection has a substantially quarter spherical shape, and the invention according to claim 6 is directed to the orientation of the cross section of approximately half of the quarter spherical projection. Is characterized in that it is in the opposite direction to the cross-sectional direction of the remaining half of the 向 き spherical projections. According to the above configuration, a strong gripping force can be maintained during paper feeding.

[0011] The invention described in claim 7 is the first invention.
In the paper transport mechanism described above, a backup roller is provided at one location in the center of the pinch roller as a second pressing member that presses the pinch roller.
The roll edge of the backup roller is chamfered and rounded. According to this configuration, a grip force equivalent to that of the split-comb type can be obtained even with a single back-up roller, and the roll edge does not damage the pinch roller surface. The invention according to claim 10 and the following claims provide a paper transport device as described above, wherein the paper transport device is used to transport a printer paper, especially a thermal printer paper transport, a thermal adhesive image receiving sheet transport, a color thermal paper transport, a PET support. It is characterized by being used for transporting body paper. The registration accuracy of each printer can be improved by using the paper transport device of the present invention for such various printer applications.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a main part of a paper transport mechanism of a printer according to a first embodiment of the present invention. FIG. 2 is a configuration diagram of a thermal printer using the paper transport device shown in FIG. FIG. 2 is a diagram showing an arrangement of protrusions on the surface of a capstan roller shown in FIG. 1. FIG. 4 is a view showing a specific shape of the projection of FIG.
(A) is a three-view drawing, and FIG. 4 (b) is an enlarged perspective view. FIG.
In the figure, 1 is a capstan roller according to one embodiment of the present invention, and 2 is a pinch roller, which constitutes a transport device having a strong gripping force by a pair of rolls of the capstan roller 1 and the pinch roller 2 and discharges from recording. The paper is transported up to.

The thermal printer shown in FIG. 2 uses the capstan roller 1 and the pinch roller 2, and
Reference numeral denotes a platen roller facing the thermal head 100. The platen roller rotates counterclockwise to convey the sheet 103, and the recording sheet 103 and toner guided by the guide roller 104 with a predetermined pressure on the thermal head 100. The ribbon 102 is being pressed.

On the surface of the capstan roller 1 shown in FIG. 1, projections 3 for increasing a frictional force are uniformly arranged. The arrangement is shown in FIG. 3 in which a portion indicated by a square in FIG. 1 is enlarged. In FIG. 3, the protrusions 3 are parallel to the axial direction (that is, at an inclination angle of 0 ° in the left-right direction in the figure) and at a constant pitch of 0.5 ± 0.2 m in the axial and circumferential directions.
The capstan roller is formed in a so-called grid roller shape by winding and fixing the strips regularly arranged in m by welding or bonding. FIG. 3A shows a so-called grid arrangement in which the protrusions 3 are arranged at right angles in the axial direction and the circumferential direction, and FIG. 3B shows an example in which the protrusions 3 need not be on the same line in the circumferential direction. This shows a so-called staggered arrangement in which the axial arrangement of the protrusions slightly shifts left and right each time the projection moves in the circumferential direction.

FIG. 4 is a view showing one embodiment of the specific shape of the projection. FIG. 4 (a) is a three-view drawing, and the upper left is a plan view.
The lower left shows a front view, and the lower right shows a side view. As can be seen from the figure, the protrusion 3 has a convex shape in the shape of Mt. Fuji, and has a height of 60 ± 40 μm and a tip diameter of 30 to 8 mm.
It is 0 μm. It turned out that 55 ± 5 μm is particularly optimum among the projection heights of 60 ± 40 μm. FIG. 4B is an enlarged perspective view of the protrusions 3 in the grid arrangement state of FIG. In this way, by forming the protrusions 3 on the surface of the capstan roller 1 in a grid pattern or a staggered pattern in the axial direction and the circumferential direction, the transfer accuracy can be greatly improved as compared with the conventional yosha roller. A comparative example will be described later (see FIG. 14).

FIG. 5 is a view showing the arrangement of the projections 3 when the diameter of the capstan roller is twice the diameter of the capstan roller of FIG. 3 in another embodiment. FIG.
(A) shows a state in which the protrusions 3 are arranged in a grid, and FIG.
(B) shows a state in which the protrusions 3 are arranged in a staggered manner.
In the same figure, all the protrusions 3 are parallel to the axial direction in the same manner as in FIG. 3 (that is, at an inclination angle of 0 ° in the horizontal direction in the figure) and at a constant pitch of 0.5 mm in the axial direction. While they are arranged (the same as in FIG. 3), capstan rollers are regularly arranged in the circumferential direction at a constant pitch of 1.0 mm, twice that of FIG. . Thus, this embodiment shows that it is advantageous to change the circumferential pitch every time the diameter of the capstan roller changes. The same applies to the pinch roller.

FIG. 6 shows another example of the embodiment of the present invention. The protrusion 3 in FIG. 2 is a Mt. Fuji-type protrusion as shown in FIG. The difference is that it is a quarter spherical projection. In FIG. 6, FIG. 6A is a three-view drawing, where the upper left is a plan view, the lower left is a front view, and the lower right is a side view. As an example, in FIG. 6, the height of the quarter spherical projection is 60 ± 40 μm. FIG. 6B shows FIG.
FIG. 4 is an enlarged perspective view of a projection 3 ′ in the arrangement state of FIG. In the figure, 3 'are all quarter-spherical projections. The 1/4 spherical projection 3 'can be made by the same manufacturing method as that of a file or a grater projection. That is, a metal mold having fine and sharp irregularities is strongly pressed against the capstan roller 1 so that the metal surface of the
Make a spherical projection 3 '. Thereafter, plating is applied to further increase the strength. By rotating the capstan roller 1 having the １ ／ spherical projection formed in this way, the cross section of the 球 spherical projection pierces the recording paper and is transported with a large resistance. Accurate conveyance force can be obtained. Moreover, when the direction of the cross-section of the quarter spherical projection is alternately changed with respect to the circumferential direction,
The capstan roller 1 can be transported with a large and highly accurate transport force in both forward and reverse directions. Further, if the size of the 1/4 spherical projection is set to some size, reliable conveyance can be performed regardless of the type of recording paper. That is, in FIG. 6B, 3′A is a large projection having a downward direction,
3'a represents a downward small projection, 3'B represents an upward large projection, and 3'b represents an upward small projection. Therefore, when the capstan roller rotates in the X direction in the figure, the large protrusion 3′A and the small protrusion 3′a contribute to the conveyance of the sheet, and conversely, when the capstan roller rotates in the Y direction in the figure, The projections 3′B and the small projections 3′b contribute to the conveyance of the sheet. These 1/4 spherical projections are parallel to the axial direction (ie,
(At an inclination angle of 0 °) and at regular intervals of 0.5 ± 0.2 mm in the circumferential and axial directions.

FIGS. 7 to 9 show each embodiment of the arrangement of the quarter spherical projections. FIGS. 7 and 8 show the quarter spherical projections 3 'having the same height. FIG. 7A shows an example using A and 3′B, and shows a grid pattern. That is, the same pitch of 0.5 mm at the same pitch in the axial direction and the circumferential direction is arranged in a grid pattern, but the same direction of protrusions (for example, 3'A) are arranged in the circumferential direction line, and the protrusion directions are alternately changed in the axial direction. (3'B). FIG.
(B) shows a staggered arrangement. That is, in the axial direction and the circumferential direction, the same pitch of 0.5 mm is staggered, but the circumferential line has the same directional protrusion (for example, 3′A).
Are arranged, and the projection direction is alternately changed in the axial direction (3′B
) Is shown. Therefore, the pitch between a certain protrusion and the nearest protrusion on a line axially adjacent to the certain protrusion is 0.25 mm.

FIG. 8 is different from FIG. 7 in that projections of the same direction (for example, 3'A) are arranged in the axial direction line, and the projection directions are alternately changed (3'B) in the circumferential direction line. The state is shown. FIG. 8 shows the grid pattern arrangement.
The pitch between the same-directional protrusions in the axial direction and the circumferential direction is 0.5 mm, respectively.

FIGS. 7 and 8 show examples in which 1/4 spherical projections (3'A, 3'B) having the same projection height are used, while FIG. / 4 spherical projection 3 '
This is an example using (3′A, 3′B and 3′a, 3′b). FIG. 9A shows a state in which protrusions having the same size in the axial direction are alternately arranged in a staggered arrangement, and the protrusions having the same size are arranged in the opposite direction in the circumferential direction. The pitch between the axially and circumferentially directional protrusions is 0.5 m each.
m. FIG. 9B shows a state in which protrusions of different sizes in the same direction in the circumferential direction are alternately arranged in a grid pattern, and protrusions of different sizes in the opposite direction in the axial direction are alternately arranged. The pitch between adjacent protrusions in the axial direction and the circumferential direction is 0.5 mm, respectively. According to this embodiment, since the 1/4 spherical projection has directionality, it can be reliably transported similarly to the above-mentioned Mt. Fuji projection. A comparative example will be described later (see FIG. 14).

Further, in FIG. 1, reference numeral 2 denotes a pinch roller constituting a roller pair with the capstan roller 1. In the present embodiment, the pinch roller is divided into four parts (2a, 2b, 2c, 2c).
d), and each of the comb-shaped rubbers 2a, 2b, 2c, 2
d is approximately equal in length and approximately a, and is formed to have a hardness of 65 ± 10 degrees, in particular, a high hardness. With such a roll pair configuration, the frictional force is increased and the gripping force is increased. Here, the diameter of the pinch roller 2 is 22φ, and the core metal is 16 mm.
φ, the total length is 310 mm, and the capstan 1 has an example of 20φ.

Next, the recording operation of the thermal printer shown in FIG. 2 will be described. Recording is performed by a known thin-film thermal transfer method using a thermal printer as shown in FIG. 2 (The 79th Annual Meeting of the Society of Electrophotography, JAPAN HARD)
COPY '97 Transactions, pp. 255-258 (1997)
reference). The toner ribbon 102 is made of PET (polyethylene terephthalate) having a thickness of 5 μm and a colorant layer having a colorant content of 45% and a thickness of 0.3 μm of four colors of KCMY (black, cyan, magenta, and yellow) at predetermined intervals. ) Coated on film. The image receiving sheet (receiver sheet) 103
A 10 μm resin layer was coated as a cushion layer on a 120 μm white PET film, and a 1 μm resin layer was coated thereon as a heat-adhesive image receiving layer. First, with the thermal head 100 raised about 5 mm from the state shown in FIG. 2 (head-up state), the toner ribbon 102 is moved from the sending side toward the winding side, that is, toward the left in FIG. The recording head is wound by a winding motor connected via a gear, and stops when the head of the first K color exceeds the recording heater position of the thermal head 100.
Next, the receiver sheet 103 is conveyed by a roller (not shown) toward the left of the figure, and when the leading end reaches between the capstan roller and the pinch roller, the capstan roller 1 starts rotating in the direction of the arrow in the figure. The capstan roller 1 is temporarily stopped at a position where the leading end is securely nipped between the capstan roller 1 and the pinch roller.
The thermal head 100 is brought down to the position shown in the figure (head down state), the winding of the toner ribbon 102 is started, and the conveyance of the receiver sheet 103 is started almost simultaneously. After 100 msec, the thermal head 10
Transmission of a strobe signal corresponding to image data to 0 starts, the heater section is energized and heated, and an image is recorded. At this time, the conveyance of the toner ribbon 102 is controlled by the winding motor, and the receiver sheet 103 is moved to the capstan roller 1.
The conveyance is controlled by a motor (not shown) connected to the motor through a gear. Toner ribbon 102 and receiver sheet 10
The respective motors are controlled such that the transport speeds at the recording position between the thermal head 100 and the platen roller 101 are substantially equal. This transfer speed is 5
It is generally about 40 mm / sec. When the transfer of the length corresponding to the image area is completed, the thermal head 10
0 completes the transmission of the strobe signal, and the toner ribbon 10
2 and the conveyance of the receiver sheet 103 are completed. The thermal head 100 is set to the head-up state, the winding of the toner ribbon 102 is started, and the toner ribbon 102 stops when the head of the next color C exceeds the recording heater position of the thermal head 100. Next, the receiver sheet 103 is conveyed in the reverse direction to the recording direction to the recording start position of the first color by the reverse rotation of the capstan roller 1 and stopped. Hereinafter, image recording is performed in the same manner as in the first color.

Similarly, after the recording of the four colors of M and Y is completed, the receiver sheet 103 is moved to the capstan roller 1.
And between the pinch roller 2 and the capstan roller 1 to be discharged. This discharge may be to the left or right in the figure. Through the above steps, one color image is completed. When the registration accuracy is measured using the registration mark for the image data of each color, it can be confirmed that the color misregistration is suppressed to a very small value.

On the other hand, in the case of thermal recording, as already known,
Light fixing (not shown) using heat-sensitive recording paper (thermoauto chrome paper manufactured by Fuji Photo Film Co., Ltd.) in which Y, M, and C color developing layers are sequentially formed on a support film such as PET. ) And the like, while heating with a thermal head, and thermally recording each color layer with different thermal energy to obtain a color image. For example,
Now, the recording paper is conveyed while rotating the capstan roller 1 in the normal direction in the direction of the arrow to perform thermal recording and optical fixing of the yellow thermosensitive coloring layer, head up after completion of the yellow recording, and reversely feed the recording paper to the recording start position. . In the next magenta image recording, thermal recording and light fixing of the magenta thermosensitive coloring layer are performed while the recording paper is being conveyed, the head is raised, and the paper is fed back. In the subsequent cyan image recording, a recording operation is performed for each color, such as carrying the recording paper in the normal rotation direction and performing thermal recording on the cyan thermosensitive coloring layer, and similarly, a frame-sequential color image recording is performed. Also in this case, when the registration accuracy is measured using the registration marks or the like, it can be confirmed that no color shift has occurred.

As described above, especially in the case of color image recording by the thermal printer in a frame sequential manner, a high registration accuracy is required for an accurate superimposing operation. However, in this embodiment, regular projections are formed. Combination of the arranged capstan roller 1 and a pair of rollers made of a high-hardness four-piece comb-tooth rubber / pinch roller 2 makes it possible to construct a conveying device with a strong gripping force and high registration accuracy, so that high-quality color printing is achieved. Becomes possible.

Next, a second embodiment of the present invention will be described. FIG. 10 is a main part configuration diagram of a paper transport mechanism of a printer according to the second embodiment of the present invention. FIG. 11 is a configuration diagram of a thermal printer using the paper transport mechanism shown in FIG. In FIG. 10, reference numeral 1A denotes a projection roller (capstan roller with projection), and a projection 3
Are uniformly arranged. The projection arrangement is regularly arranged in a grid pattern as shown in FIG. 3A when the circle T on FIG. 10 is enlarged. This projection is the Mt. Fuji type projection shown in FIG. 4, and the height of the projection is adjusted to 55 μm or more, preferably 55 ± 5 μm as the optimum altitude. The protrusion pitch p is the same as in the first embodiment, and is selected to be p = 0.5 ± 0.2 mm from p = ar (where r = the radius of the capstan roller). Instead of the Mt. Fuji-shaped projection, it may of course be constituted by a 1/4 spherical-shaped projection shown in FIG. As for the formation of the capstan roller 1A, similarly to the first embodiment, a projection 3 having a projection height of 55 ± 5 μm and having a projection height of 55 ± 5 μm is formed on the core metal of the capstan roller 1A at a constant pitch p =
The strips are regularly arranged and formed to be 0.5 ± 0.2 mm parallel to the axial direction, and are formed into a grid roller shape by winding and fixing the strips by welding or bonding.

Reference numeral 2A denotes a pinch roller. The roller pair of the capstan roller 1A is not the pinch roller of the quadruple comb tooth rubber in the first embodiment, but is a straight type and has a rubber hardness of 65 ± 10 degrees (preferably Backup roller 4 for holding down the central part.
Is used to obtain the same pressing force and gripping force as when using a comb pinch roller. Further, the back-up roller 4 is chamfered at the end 4B and rounded.
This prevents the rubber substrate of the pinch roller 2A from being damaged.

FIG. 11 shows a capstan roller 1 A having a projection 3 formed thereon, a pinch roller 2 A, and a backup roller 4.
FIG. 1 is a configuration diagram of a thermal printer using a paper transport mechanism having the following. The recording operation is the same as that of the first embodiment. For example, in the case of thermal transfer recording, first, the thermal ribbon 100 is raised about 5 mm from the state shown in FIG. Is wound by a winding motor connected to a shaft on the winding side via a gear from the sending side to the winding side, that is, to the left in the drawing. Stops when the recording heater position is exceeded.
Next, the receiver sheet 103 is conveyed toward the left of the figure by a roller (not shown), and when the leading end reaches between the capstan roller and the pinch roller, the capstan roller 1A starts rotating in the direction of the arrow in the figure. The capstan roller 1A is temporarily stopped at a position where the leading end is securely nipped between the capstan roller 1A and the pinch roller 2A. With the thermal head 100 lowered to the position shown in the figure (head down state), the toner ribbon 10
2 and the receiver sheet 103 almost at the same time.
Is also started. After 100 msec, transmission of a strobe signal according to the image data to the thermal head 100 starts, the heater section is energized and heated, and an image is recorded. At this time, conveyance of the toner ribbon 102 is controlled by a winding motor, and conveyance of the receiver sheet 103 is controlled by a motor (not shown) connected to the capstan roller 1A via a gear. The respective motors are controlled such that the transport speeds of the toner ribbon 102 and the receiver sheet 103 at the recording position between the thermal head 100 and the platen roller 101 become substantially equal. This transport speed is generally about 5 to 40 mm / sec. At the time when the transport corresponding to the length corresponding to the image area is completed, the thermal head 100 completes the transmission of the strobe signal and completes the transport of the toner ribbon 102 and the receiver sheet 103. The thermal head 100 is set to the head-up state, the toner ribbon 102 starts winding, and stops when the head of the next color C, which is the recording heater position of the thermal head 100, exceeds the position. Next, the receiver sheet 103 is conveyed in the direction opposite to the recording direction to the recording start position of the first color by the reverse rotation of the capstan roller 1A and stopped. Thereafter, image recording is performed in the same manner as in the first color, and four-color thermal transfer recording is performed. The operation of the thermal recording is the same as that of the first embodiment. According to such a second embodiment, the protrusion pitch is set to 0.5 ± 0.
A capstan roller 1A having a projection row of 2 mm and a projection height of 55 ± 5 μm;
Paper feed mechanism constituted by a combination of a pinch roller 2A of a degree and a back-up roller 4 chamfered,
Due to the effect of the formation of the projections having the optimum height, the gripping force of the transport mechanism and the registration accuracy can be increased more than in the first embodiment, and high-quality color printing can be performed.

Next, a third embodiment of the present invention will be described. FIG. 12 is a front view of a capstan roller according to the third embodiment of the present invention. The third shown in FIG.
Is the first embodiment shown in FIG. 1 and FIG.
The difference from the surface view in the second embodiment shown in FIG. 7 is that the projections 3 arranged on the surface of the capstan roller 1B are not arranged on the entire surface, but are arranged only partially. For example, the comb pinch rollers 2a, 2a shown in FIG.
The projections 3 are arranged only at the portions corresponding to the lengths b, 2c and 2d, and are not arranged at the intermediate portion which does not contact the pinch roller 2. With such an arrangement of the projections 3, the same effect as in the previous embodiment can be obtained.

The practical effect of using the above-described printer transport apparatus of the present invention is described below. The printing image (LAT4) shown in FIG. 13 is recorded and the registration accuracy (registration accuracy) at that time is recorded. ), And specific evaluation results are shown in the table of FIG. As an evaluation procedure in this case, a print image (LAT4) as shown in FIG.
In the sub-scanning direction (printing direction), a halftone four-color image in a grid pattern was recorded on only one image of the printed image with the registration marks at the four corners superimposed. Since the image of FIG. 13 is a single image, if there is a defect in the conveyance force, the overlap (registration) of the four colors is disturbed. In this evaluation test, in addition to this, three sheets were printed with the set value of the toner winding shaft torque changed, and the amount of misregistration of the four registration mark marks was measured with a loupe to obtain a value of 100 μm.
m is determined as OK, and the number exceeding 100 μm is regarded as the number of defects. In this case, 0 is good, and other numerical values are impossible.

FIG. 14 is a table showing the evaluation of the above-described registration (register) accuracy by combining various types of capstan rollers and pinch rollers in the form of a table. In the following description, (1) the type column of the capstan roller, this column shows the conventional yosha roll and the grid (projection) roll of the present invention having a height of 60 μm and a pitch of 0.5 mm according to the first embodiment. ,
A case of a comparative example having a height of 80 μm and a pitch of 0.3 mm, and finally, a case of a second example having a projection height of 55 μm and a pitch of 0.5 mm are shown. (2), pinch roller type column, this column is the rubber hardness,
It shows the type of a comb tooth or a straight pinch roller with a backup roller. (3) Image type column, four-color print images LAT4 and LA
T2 and the number of sheets are shown as n = 3. (4), toner take-up shaft torque value column, 2.00 each
１．０11.00 kgf / cm.

The following is clear from the evaluation results shown in FIG. (1) In the example of the conventional yosha roll, the hardness is 40
° comb teeth (Comparative Example 1), 50 ° comb teeth (Comparative Example 2), 7
It can be seen that in all of the 0 ° comb teeth (Comparative Example 3), the registration failure number in which the misregistration amount of the register mark exceeds 100 μm occurs in all three cases. (2) However, in the case of a grid roll of so-called Mt. Fuji-shaped protrusion (hereinafter referred to as a-shaped protrusion) shown in FIG. 4 according to the present invention, the pinch roll according to the first embodiment having a height of 60 μm and a pitch of 0.5 mm is used. In the case of using a 60 ° comb tooth (Example 1) and a 70 ° comb tooth (Example 2) with high hardness, the number of occurrences of the misregistration is 0 and the registration accuracy is clearly improved. (3) However, even in the case of a grid roll having a height of 60 μm and a pitch of 0.5 mm, the pinch roll hardness is as low as 40 ° comb teeth (Comparative Examples 4 and 5) and 50 ° comb teeth (Comparative Example 6). In this case, it can be seen that the amount of misregistration of the register mark is large (3 out of 3). (4) Even when the pinch roll hardness is constituted by a high hardness 70 ° comb tooth (Comparative Example 7), the protrusion height is set to the optimum value (55 ± 5).
It can be seen that, when the pitch is higher than 5 μm (80 μm), the amount of registration mark deviation is large (3 out of 3) even with a grid roll having a pitch of 0.3 mm. Further, when the projections are too high, unevenness in density occurs in an image at a position corresponding to the projections. (5) Therefore, the height of the a-type projection is adjusted to an optimum value (55 ± 5 μm).
In the case of a grid roll having 60 μm and a pitch of 0.5 mm in the case of m), in the case of the second embodiment having a backup roll with a straight pinch roll, when the hardness is selected to be a low hardness of 50 °, the misregistration occurs. The number of occurrences was one (Comparative Example 8), but when the hardness was selected to be high hardness (70 °), the number of occurrences of misregistration was 0 (Example 3). (6) Similarly, adjust the height of the a-type projection to an optimum value (55 ± 5 μm).
In the case of the second embodiment having a backup roll with a straight pinch roll in the case of a grid roll having 55 μm and a pitch of 0.5 mm in m), the hardness is selected to be 80 °, which is even harder than 70 °. if you do,
Regardless of the type of the image LAT (LAT4 = Example 4, LAT2 = Example 5), the number of occurrences of misregistration was 0 in all cases. (7) Although the protrusions of Examples 1 to 5 are all a-type protrusions, the protrusions of Examples 6 to 8 are all so-called 球 spherical protrusions (hereinafter referred to as b-type protrusions) shown in FIG. ). Example 6 is a grid roll in which the height of the b-type protrusion is 50 μm, Example 7 is 60 μm, Example 8 is 70 μm, and the pitch is all 0.5 mm, and a straight pinch roll having a hardness of 70 °. With backup roll. What we can see from this is 1/4
Regardless of whether the height of the spherical projection is 50 to 70 μm or not, the number of occurrences of misregistration is 0 in any case. That is, it can be seen that the magnitude and accuracy of the conveyance force of the quarter spherical projection are excellent.

[0033]

As described above, according to the present invention,
A capstan roller in which a projection having a height of 60 ± 40 μm, preferably 60 ± 15 μm and a projection pitch of 0.5 ± 0.2 mm is arranged on the entire surface of a paper transport mechanism of a printer such as a thermal printer. And a pinch roller of high hardness as a roller pair of the capstan roller, so that the recording paper can be strongly gripped without causing any adverse effects such as the conventional misregistration. This makes it possible to prevent color misregistration and bleeding in the case of color image recording, and to enhance image dimensional accuracy even in monochrome image recording. In the above, the case where an image is recorded has been described. However, the recording position accuracy can be improved even with a data recording tape other than an image. Similar effects can be expected in the case of recording heads other than thermal heads, such as LED heads, laser heads, inkjet heads, DMD heads, EL heads, liquid crystal heads, and the like.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a sheet transport mechanism according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a thermal printer using the paper transport mechanism shown in FIG.

FIG. 3 is a diagram showing an arrangement of protrusions on the surface of a capstan roller shown in FIG. 1;

4A and 4B are views showing a Mt. Fuji-shaped projection, which is a specific shape of the projection of FIG. 3; FIG. 4A is a three-sided view, and FIG. 4B is an enlarged perspective view.

FIG. 5 is a diagram showing an arrangement of protrusions 3 when the diameter of the capstan roller is twice the diameter of the capstan roller of FIG. 3; FIG. 5A shows a state where the protrusions are arranged in a grid pattern, and FIG. 3B shows a state where the protrusions are arranged in a staggered manner.

FIGS. 6A and 6B are views showing a quarter spherical projection as a specific shape of the projection of FIG. 3, wherein FIG. 6A is a three-sided view and FIG. 6B is an enlarged perspective view.

FIG. 7 shows a first embodiment of the arrangement of the quarter spherical projections in FIG. 6;

FIG. 8 shows a second embodiment of the arrangement of the quarter spherical projections of FIG. 6;

FIG. 9 shows a third embodiment of the arrangement state of the quarter spherical projections in FIG. 6;

FIG. 10 is a main part configuration diagram of a paper transport mechanism according to a second embodiment of the present invention.

11 is a configuration diagram of a thermal printer using the paper transport mechanism shown in FIG.

FIG. 12 is a front view of a capstan roller according to a third embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of a print image for evaluation of the paper transport mechanism of the printer of the present invention.

FIG. 14 is a diagram showing the evaluation contents of a paper transport device using the print image shown in FIG.

FIG. 15 is a configuration diagram of a conventional paper transport device of a grip roller type.

FIG. 16 is a diagram showing an example of a conventional register mark.

FIG. 17 is a configuration diagram of a conventional grip belt type paper transport device.

FIG. 18 is an enlarged view of the surface of a conventional capstan roller (Yosha).

[Explanation of symbols]

 1, 1A, 1B Capstan roller 2, 2A Pinch roller 3, 3 'Projection 4 Backup roller 4B Backup roller end

Claims (14)

[Claims] 1. A sheet transport mechanism for transporting a sheet by a capstan roller and a pinch roller as a roller pair of the capstan roller, wherein the capstan roller has a height of 60 ± 40 μm and an axial pitch of 0.1 mm. A paper transport mechanism comprising a capstan roller in which protrusions having a convex shape of 5 ± 0.2 mm are arranged in an area of at least half of the surface, and wherein the pinch roller has a high hardness. 2. The paper transport mechanism according to claim 1, wherein
The height of the projections arranged on the surface of the capstan roller is 60 ± 15 μm. 3. The paper transport mechanism according to claim 1, wherein the angle of formation of the projections arranged on the entire surface of the capstan roller is 0 degrees with respect to the axial direction. 4. The paper transport mechanism according to claim 3, wherein the arrangement of the projections is such that one or two rows of the projections are simultaneously in contact with a pinch roller. 5. The paper transport mechanism according to claim 1, wherein said projection has a substantially quarter spherical shape. 6. A plurality of the projections according to claim 5, wherein:
A paper transport mechanism characterized in that the cross section of substantially half of the quarter spherical projections has a direction opposite to that of the remaining half of the quarter spherical projections. 7. The paper transport mechanism according to claim 1, wherein a backup roller is provided at a central portion of the pinch roller as a second pressing member for pressing the pinch roller. 8. The paper transport mechanism according to claim 7, wherein a roll end of the backup roller is chamfered and rounded. 9. The paper transport mechanism according to claim 1, wherein the pinch roller has a high hardness of 55 to 85 °. 10. A printer which records an image on a recording sheet while conveying the recording sheet by a conveying mechanism including a pair of rollers of a capstan roller and a pinch roller, wherein the conveying mechanism is any one of claims 1 to 9. A printer comprising the paper transport mechanism according to any one of the preceding claims. 11. A thermal printer for performing thermal recording on a recording sheet while transporting the recording sheet by a transport mechanism using a pair of a capstan roller and a pinch roller, wherein the transport mechanism is any one of claims 1 to 9. Thermal printer characterized by comprising a paper transport mechanism of 12. 30 to 70 parts by weight of pigment and 25 to 60 parts by weight
A toner sheet containing a colorant having a weight of 0.2 to 1.0 μm and containing a colorant having an amorphous organic high molecular weight polymer having a softening point of 40 to 150 ° C. and an image receiving layer having a heat adhesive image receiving layer 10. A thin-film thermal transfer printer which transports the image receiving sheet by a transport mechanism using a roller pair of a capstan roller and a pinch roller when thermal transfer recording is performed by closely contacting the sheet, wherein the transport mechanism is any one of claims 1 to 9. A thin-film thermal transfer printer characterized by comprising a paper transport mechanism. 13. A color thermal paper printer which transports the color thermal paper by a transport mechanism using a pair of a capstan roller and a pinch roller when performing color thermal recording on color thermal paper in a sequential manner. A color thermal paper printer comprising the paper transport mechanism according to any one of claims 1 to 9. 14. A paper transport mechanism for transporting the PET support recording paper by a pair of a capstan roller and a pinch roller when performing image recording using a recording paper whose support is made of PET, A transport mechanism for a PET support recording paper, wherein the transport device is constituted by the paper transport mechanism according to any one of claims 1 to 9.