JP2020089979A - Indirect transfer printer - Google Patents

Abstract

Kind Code: A1 An indirect transfer printer capable of suppressing misalignment of printing position and misregistration of colors caused by the transport error by detecting the transport error of an intermediate transfer film in real time during printing operation and correcting the transport amount in real time. offer. By comparing the specified rotation angle of the rotary encoder and the actual rotation angle at the time of image formation for each constant transportation pulse, the transportation amount of the intermediate transfer film is determined as the allowable range, the correctable range, and the transportation error. If it is within the correctable range, the number of conveying pulses is corrected in real time so that the conveying amount becomes an appropriate amount. [Selection drawing] Fig. 3

Description

The present invention relates to an indirect transfer printer that transfers an image to an object to be processed such as cards, booklets, forms, molded products, and paper products.

A method of forming an image by thermal head printing using an ink ribbon is a known technique, and is used for various purposes such as printing on a card, outputting a photographic image, printing on a sticker, and the like. However, many of these printing methods have a problem that it is necessary to provide a specific image receiving layer on the surface of the medium, and the combination thereof is limited.

Therefore, an ink ribbon is used to form an image on an intermediate transfer film having a specific image-receiving layer, and then the image is retransferred to a transfer-receiving member, so that a multicolor image can be formed without selecting the base material of the final printing medium. An indirect transfer method has been proposed as a method that can be used (for example, Patent Document 1).

Such a printer expands the print data sent from the higher-level device through the external bus on the buffer memory, and outputs a current pulse corresponding to the sent print data to each heating element of the thermal head. The supply of heat causes the heating element to generate heat, and an image is transferred from the ink ribbon to the intermediate transfer film.

The indirect transfer system has a feature of the apparatus configuration that it has a mechanism in which a long intermediate transfer film in a roll shape is unwound and conveyed, and reciprocally moved for color superposition in multicolor printing. When the intermediate transfer film is conveyed, misalignment of dots or color deviation may occur due to conveyance error. The transport error is caused by various factors, for example, it is caused by a mechanism such as slip or meandering of the transport roller, or is caused by a medium such as looseness of the intermediate transfer film roll or winding misalignment.

As a method of correcting this conveyance error, for example, a sensor mark is transferred from the ink ribbon, the sensor mark is detected by the sensor while reciprocating during the initialization operation, and the timing is compared with the number of rotation pulses supplied to the conveyance motor. Therefore, a method of making a correction so that the optimum number of rotation pulses is obtained is performed. However, with this method, when an error occurs due to winding loosening or the like between the initialization operation and the actual printing operation, the correction cannot be performed, which may cause color misregistration.

Further, for example, in Japanese Patent Laid-Open No. 2004-242242, there is a system in which an encoder for detecting the rotation amount of the film in real time is mounted on the nip roller and the timing of current application for printing is controlled according to the rotation amount. It is necessary to change the timing of sending the printing pulse according to the misalignment, which requires advanced control that considers an appropriate cooling period and supplemental heating period, etc. It was difficult to correct the deviation itself.

Japanese Patent No. 3063421 JP-A-63-257660

The present invention has been made in consideration of the above circumstances, and an object thereof is to detect a transport error of an intermediate transfer film in real time during a printing operation in an indirect transfer printer and correct the transport amount in real time. An object of the present invention is to provide an indirect transfer printer capable of suppressing a print position shift and a color overlay shift due to a transport error.

In order to solve the above problems, the invention according to claim 1 of the present invention is
Using an intermediate transfer film provided with at least a peelable transfer layer on the substrate,
A thermal head for heating the ink ribbon to form an image on the intermediate transfer film;
A re-transfer means for re-transferring the image formed on the intermediate transfer film to a transfer target, and a transfer controller for generating a transfer pulse for transferring the intermediate transfer film,
Conveying means capable of reciprocating the intermediate transfer film according to the number of the conveying pulses,
A sensor provided at least at two positions for detecting a sensor mark provided on the intermediate transfer film;
A rotary encoder that is connected to at least one roller shaft that is in constant contact with the intermediate transfer film, and that detects a rotation angle of the roller shaft;
A calculation determination unit that performs calculation and determination using the rotation angle data detected by the rotary encoder when the intermediate transfer film is transported and the transport pulse number data supplied at that time. An indirect transfer printer equipped with
During the initialization operation, the intermediate transfer film is conveyed so that the sensor mark passes between at least two sensors, and from the number of conveyance pulses required for passing and the rotation angle detected by the rotary encoder, The calculation determination unit calculates a rotation angle per a predetermined number of specified carrier pulses to obtain a specified rotation angle,
When an image is formed on the intermediate transfer film, the actual rotation angle of the rotary encoder and the specified rotation angle at that time in the calculation determination unit are supplied every time the transfer pulse is supplied to the transfer unit for the specified transfer pulse. If the difference is less than or equal to a predetermined allowable value, it is determined that there is no transport error, and if it is greater than a predetermined limit value, it is determined as a transport error, and if it is greater than the allowable value and less than or equal to the limit value. Is determined to be correctable,
In the transport control unit, based on the determination result, when it is determined that there is no transport error, without changing the number of specified transport pulses to be supplied next to the specified transport pulse,
If it is determined to be a transport error, stop the image forming operation,
When it is determined that correction is possible, the number of specified carrier pulses supplied after the specified carrier pulse is corrected so that the difference between the specified rotation angle and the actual rotation angle of the rotary encoder becomes small. It is an indirect transfer printer.

The invention of claim 2 of the present invention is
The indirect transfer printer according to claim 1, wherein the sensor is provided on each of an upstream side and a downstream side of the thermal head in a path of the intermediate transfer film.

The invention according to claim 3 of the present invention is
3. The indirect transfer printer according to claim 1, wherein, when an image is formed on the intermediate transfer film, the sensor mark used during the next image formation is transferred and recorded on the intermediate transfer film by a thermal head. is there.

According to the first aspect of the present invention, at the time of the initialization operation, the actual transport amount of the intermediate transfer film with respect to the transport pulse is calculated from the rotation angle of the rotary encoder to calculate the specified rotation angle, and the actual image is obtained. During the forming operation, the specified rotation angle is compared with the rotation angle of the rotary encoder, which indicates the actual amount of intermediate transfer film conveyed, for each fixed specified number of conveyance pulses, and the difference is evaluated and compared with the conveyance operation during initialization. Fluctuation is evaluated to determine whether the same transport is being performed, whether a transport error should occur, or if it is within the correctable range. By moving the image closer to the corner, it corrects the misregistration in real time during the actual image forming operation, suppresses the image misregistration and the color registration misalignment, and if the correction is impossible, it operates as a misfeed. By stopping the process, an image with poor quality is not printed, the intermediate transfer form and the ink ribbon are not wasted, and the working time can be reduced.

According to the second aspect of the invention, the sensor is provided at the position sandwiching the thermal head from the upstream side and the downstream side in the path through which the intermediate transfer film passes when actually forming an image. It is more preferable that the specified rotation angle can be set in a state closer to that at the time of image formation.

According to the third aspect of the present invention, the sensor mark is transferred and recorded when the image is formed on the intermediate transfer film, so that the recorded sensor mark is used when the image is formed on the next screen. Can be efficient.

It is a schematic diagram showing an example of the basic composition of the indirect transfer printer of the present invention. It is a schematic diagram of an example of arrangement of dots formed on an intermediate transfer film. 6 is a schematic flowchart of the operation of the indirect transfer printer of the present invention. It is explanatory drawing explaining the change of the conveyance length at the time of carrying out adjustment of the conveyance pulse. It is explanatory drawing of the conveyance state at the time of adjusting a conveyance pulse.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. Throughout all the drawings, the same reference numerals are given to the components that exhibit the same or similar functions, and the duplicated description will be omitted.

FIG. 1 is a schematic diagram showing a basic configuration example of an indirect transfer printer of the present invention.

In the indirect transfer printer (hereinafter, also simply referred to as a printer) 1 of FIG. 1, an ink ribbon 10 having an ink layer containing at least a pigment and an intermediate transfer film 20 having at least a transfer layer releasably provided on a substrate are provided. The intermediate transfer film 20 supplied from the respective unwinding units 11 and 21 is passed through the main transfer roller 30 which supplies a reciprocating transfer force based on a transfer pulse supplied from a transfer control unit (not shown). An image is formed on the transfer layer of the intermediate transfer film 20 by being sandwiched between the thermal head 40 and the platen roller 41 so as to face the ink ribbon 10 and based on the print data.

Here, in the ink ribbon 10, in addition to an ink layer containing cyan, magenta, yellow, and black dyes, a special ink layer such as a fluorescent dye ink layer and an adhesive layer made of a thermoplastic resin are sequentially arranged. It may be provided, and after forming an image on the intermediate transfer film 20 by using the various ink layers, the adhesive layer may be thermally transferred onto the formed image.

The intermediate transfer film 20 is provided with various layers such as a peeling layer, a protective layer, a printing layer, an OVD (Optical Variable Device) layer, and an intermediate layer, in addition to the receiving layer of the ink layer containing the dye. May be.

As described above, the image-formed portion of the intermediate transfer film 20 is conveyed to the portion of the heat roller 50, and is arranged so as to face the transferred body 70 conveyed by the conveyance table 80. The image is retransferred from the intermediate transfer film 20 to the transfer target 70 by 50. After that, the ink ribbon 10 and the intermediate transfer film 20 are wound up on the respective winding portions 12 and 22. However, the intermediate transfer film 20 is rewound to the position of the thermal head 40 when an image is formed on the next screen.

A rotary encoder 32 is connected to a roller shaft 31 that is always in contact with the intermediate transfer film 20 in the normal state on the downstream side of the thermal head 40 in the path through which the intermediate transfer film 20 passes, and rotates together with the roller shaft 31. The rotation angle can be detected.

Further, sensors s1 and s2 are provided on the upstream side and the downstream side of the thermal head 40 on the path through which the intermediate transfer film 20 passes, and the sensor marks provided on the intermediate transfer film 20 are read to perform initialization operation and image recording operation. At this time, the position of the intermediate transfer film can be aligned.

During the initialization operation, the intermediate transfer film 20 is appropriately conveyed in the rewinding direction, the unwinding direction, or both directions, the sensor mark is detected by passing through both the sensors s1 and s2, and the position of the sensor mark is used as a reference. As a result, the position of the intermediate transfer film 20 can be adjusted.

The rotary encoder 32 may be connected not only to the roller shaft 31 on the downstream side of the thermal head as shown in FIG. 1 but also to the roller shaft on the upstream side, that is, to both the upstream side and the downstream side, that is, You may provide in two places. The output of the rotary encoder 32 is used for calculation and determination of transport deviation in a calculation determination unit (not shown).

The sensor mark of the intermediate transfer film can be provided by printing a black patch that can be detected by a sensor having a constant pitch during manufacturing. In addition, the sensor mark can be provided by transferring black ink from the ink ribbon with the thermal head during the printing operation. These can also be used in combination.For example, a sensor mark provided by printing in advance is used for aligning the print with the thermal head, and another sensor mark provided with the thermal head at that time is retransferred with the heat roller. It is also possible to adopt a usage method such as using for position alignment.

FIG. 2 is a schematic diagram of an example of the arrangement of dots that are pixels of an image formed on the intermediate transfer film 20 by the indirect transfer printer having the above-described configuration. When there is no unevenness in conveyance of the intermediate transfer film 20, the dots are uniformly and two-dimensionally arranged as shown in FIG. 2A, and the pitch a in the conveying direction is constant. On the other hand, if uneven transport occurs in the middle, for example, as shown in FIG. 2B, the pitch in the transport direction changes from a to a′, so that the dot arrangement is disturbed and it appears as uneven print. I will end up. In addition, the length of the intermediate transfer film conveyed also changes accordingly. Further, when the dots of the next color overlap due to the color overlapping, the way of overlapping the dots changes, and the color unevenness is recognized.

There are various causes of uneven transport, for example, variations in winding tension during manufacturing of the intermediate transfer film, shocks during transportation, poor storage environment, and other causes that occurred before actual use. During use with an indirect transfer printer, when the intermediate transfer film is unwound and rewound, which is a peculiar operation of the indirect transfer printer, when reciprocating with unwinding, winding misalignment or insufficient tension at the time of rewinding may occur. It may occur as a cause. Conveyance unevenness is likely to be particularly affected when the intermediate transfer film is printed while being conveyed at a fine pitch, such as when printing with a thermal head.

A method for effectively correcting such conveyance unevenness will be described in detail with reference to the schematic flowchart of the operation of the indirect transfer printer of the present invention in FIG.

When printing with an indirect transfer printer, first, each mechanical part is initialized by an initializing operation, and the intermediate transfer film is reciprocally moved to detect a sensor mark. The sensor mark used at this time may be either a mark formed by printing as described above or a mark provided when the indirect transfer printer was previously used by thermal transfer using a thermal head.

However, while the sensor mark provided by printing in advance is provided over the entire intermediate transfer film, the sensor mark provided by the thermal head is provided only at the used portion where the image is formed by the thermal head. Therefore, if the sensor mark provided by the thermal head is used, the unused portion of the intermediate transfer film can be located at the same time with the same sensor, which is efficient.

When the sensor s1 detects the sensor mark, the intermediate transfer film is conveyed to the winding portion side and the sensor s2 detects the same sensor mark.

At that time, the number of transport pulses supplied to drive the main transport roller is counted, and the transport pulse number NPs until the sensor mark moves from the sensor s1 to the sensor s2 is obtained. At the same time, the rotation angle Nθs is detected by the rotary encoder connected to the roller shaft at that time.

Then, the calculation determination unit calculates the rotation angle of the rotary encoder per a predetermined number nPs of specified carrier pulses, that is, the specified rotation angle nθs, and also sets the allowable value θp and the limit value θr of the error of the rotation angle.

After the initialization operation is completed, the printing operation is started. The ink ribbon and the intermediate transfer film are conveyed to the print start position, and the thermal head is pressed to start printing. Every time the carrier control unit supplies the carrier pulses for the specified carrier pulse number nPs during printing, the calculation determination unit compares the rotation angle θa detected by the rotary encoder with the specified rotation angle nθs and evaluates the error. To do.

If the conveyance is performed in the same way as at the time of initialization, the rotation angle θa detected by the rotary encoder and the specified rotation angle nθs become equal, but if the conveyance unevenness occurs as in the example of FIG. 2, the conveyance length becomes longer accordingly. The rotation angle θa detected by the rotary encoder also becomes large, and becomes short in the opposite case. That is, by comparing the rotation angle θa detected by the rotary encoder with the specified rotation angle nθs, it is possible to detect the occurrence of conveyance unevenness.

When the detected error is within the allowable value θp, that is, |θa-nθs|≦θp
When the relational expression is satisfied, it is determined that the error is slight and is within the allowable range, and the printing operation for one screen is continued as it is.

When the error is larger than the allowable value θp and is equal to or less than the limit value θr, that is, θp<|θa-nθs|≦θr
When the relational expression of is satisfied, it is determined that there is an error but it is within a correctable range, and the prescribed carrier pulse number nPs is increased or decreased by a necessary number k in the direction of reducing the error
nPs → nPs±k
And fix it. After that, the printing operation is similarly continued.

When the error is larger than the limit value θr, that is, θr<|θa−nθs|
If the condition is satisfied, the error is large and it is determined that the correction is difficult, and it is determined that there is a transport error, and the printing operation is stopped.

FIG. 4 is an explanatory diagram for explaining changes in the transport length when the prescribed transport pulse is adjusted in the above-described operation flow. FIG. 4A shows a case where the transport length is extended as shown in the middle chart due to the effect of winding loosening during transport by a certain regular transport pulse. At this time, by reducing the specified transport pulse number nPs by, for example, k pulses, the transport length can be made closer to the original transport length, the dot arrangement disorder in image formation can be suppressed, and printing unevenness and color unevenness can be reduced. be able to.

This also applies when the transport length is shortened as shown in FIG. 4B. In that case, the transport length is increased by adding, for example, k′ pulse to the specified transport pulse nPs to increase the original transport length. It is possible to bring them closer to each other, it is possible to suppress the disorder of the dot arrangement in the image formation, and it is possible to reduce printing unevenness and color unevenness.

As a result, in the indirect transfer printer of the present invention, as shown in FIG. 5, the conveyance length becomes longer than the conveyance length when the intermediate transfer film is normally conveyed, for example, due to the looseness of the winding. When the error occurs, if the correction is not performed in real time, as shown in the chart in the middle, the misalignment accumulates, resulting in large misalignment, resulting in positional misalignment and color unevenness. By detecting each time with a rotary encoder and making corrections in real time, dot misregistration is minimized and accumulated color misregistration is greatly suppressed without the accumulation of transport misalignment, as shown in the lower chart. It becomes possible. Further, at this time, not only the number of carrier pulses can be reduced, but also the number of carrier pulses can be reduced so as to absorb the stretched amount due to the unevenness of the carrier.

As described above, in the indirect transfer printer of the present invention, during the actual image forming operation, the fluctuation of the actual transport length of the intermediate transfer film is reflected in the pulse number of the defined transport pulse for each predetermined defined transport pulse. As a result, it is possible to suppress the occurrence of conveyance unevenness in real time, and it is possible to effectively suppress the occurrence of image positional deviation and color registration deviation due to conveyance unevenness.

1... Indirect transfer printer 10... Ink ribbon 20... Intermediate transfer film 11, 21... Unwinding section 12, 22... Winding section 30... Main transport roller 31... Roller Shaft 32... Rotary encoder 40... Thermal head 41... Platen roller 50... Heat roller 70... Transfer target 80... Transport table

Claims (3)

Using an intermediate transfer film provided with at least a peelable transfer layer on the substrate,
A thermal head for heating the ink ribbon to form an image on the intermediate transfer film;
A re-transfer means for re-transferring the image formed on the intermediate transfer film to a transfer target, and a transfer controller for generating a transfer pulse for transferring the intermediate transfer film,
Conveying means capable of reciprocating the intermediate transfer film according to the number of the conveying pulses,
A sensor provided at least at two positions for detecting a sensor mark provided on the intermediate transfer film;
A rotary encoder that is connected to at least one roller shaft that is in constant contact with the intermediate transfer film, and that detects a rotation angle of the roller shaft;
A calculation determination unit that performs calculation and determination using the rotation angle data detected by the rotary encoder when the intermediate transfer film is transported and the transport pulse number data supplied at that time. An indirect transfer printer equipped with
During the initialization operation, the intermediate transfer film is conveyed so that the sensor mark passes between at least two sensors, and from the number of conveyance pulses required for passing and the rotation angle detected by the rotary encoder, The calculation determination unit calculates a rotation angle per a predetermined number of specified carrier pulses to obtain a specified rotation angle,
When an image is formed on the intermediate transfer film, the actual rotation angle of the rotary encoder and the specified rotation angle at that time in the calculation determination unit are supplied every time the transfer pulse is supplied to the transfer unit for the specified transfer pulse. If the difference is less than or equal to a predetermined allowable value, it is determined that there is no transport error, and if it is greater than a predetermined limit value, it is determined as a transport error, and if it is greater than the allowable value and less than or equal to the limit value. Is determined to be correctable,
In the transport control unit, based on the determination result, when it is determined that there is no transport error, without changing the number of specified transport pulses to be supplied next to the specified transport pulse,
If it is determined to be a transport error, stop the image forming operation,
When it is determined that correction is possible, the number of specified carrier pulses supplied after the specified carrier pulse is corrected so that the difference between the specified rotation angle and the actual rotation angle of the rotary encoder becomes small. And an indirect transfer printer. The indirect transfer printer according to claim 1, wherein the sensors are provided on an upstream side and a downstream side of the thermal head in a path of the intermediate transfer film, respectively. 3. The indirect transfer printer according to claim 1, wherein, when an image is formed on the intermediate transfer film, the sensor mark used in the next image formation is transferred and recorded on the intermediate transfer film by a thermal head.