JP3333556B2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to color thermal printers, and more particularly to a sensor for detecting the color and position of a dye donor patch on a thermal dye transfer ribbon in a color thermal printer.

[0002]

BACKGROUND OF THE INVENTION In order to print effectively and efficiently using a color thermal transfer printing process, a dye-impregnated color donor web must be properly aligned with a dye receiver. In order to completely cover the image area with the continuous color patches, it is necessary to perform proper alignment. A typical color donor web is repeatedly arranged in a certain order of a yellow patch, a magenta patch, a cyan patch, a black patch and / or a clear fusion patch.
g patch). Each patch must be properly aligned with the receiver to ensure high quality printing. One method of properly aligning and indexing the receiver and donor, or indexing the receiver and donor, is a detector that detects yellow, magenta, cyan, black, and clear fusion colors to identify their location. Is used.

One type of sensing system is disclosed in US Pat. No. 4,551,729 issued Nov. 5, 1985 to Takeshi Kubo, Junji Kuwano, Fumio Takahashi and Tsutomu Yamaguchi. Where the donor web is coded with marks detected by the detection means after the donor has passed the thermal printhead. However, this system uses a sheet of paper with a copy sheet having edges punched or punched in advance. Indexing the donor web and paper is not a significant issue due to the large diameter of the drum, but requires general alignment. This general alignment is accomplished by installing a sensor element in the donor passage past the thermal printhead and detecting the mark after the donor has passed through the printhead. One of the difficulties with this system is that pre-punched holes that engage the drum protrusions and advance the donor and receiver are prone to stretch and misalignment, which degrades print quality. That is.

[0004]

A thermal printer having a different sensing arrangement is disclosed in US Pat. No. 4,620,199 issued Oct. 28, 1986 to Tatsumi Hisao, Kayata Haruhiko, and Fumio Watanabe. It has been disclosed. The donor web is contained in a cassette having an opening for engaging the sensor. The donor passes the sensor relatively far from the area where printing is to take place. Before printing occurs, a color sensor senses the color of the donor as the donor is unwound from the donor supply spool. Of course, various problems can occur during the passage of the donor ribbon from the location of the sensor to the location of the print.

Accordingly, it is recognized that it is highly desirable to have a color sensor that accurately senses the position and color of the donor ribbon during printing to record a precise color.

US Pat. No. 4,710,781, issued to Stanley W. Stephenson on Dec. 1, 1987, discloses an apparatus for recognizing different color frames on a donor web. ing. The sensor includes a light emitting diode (LED) that emits red or yellow light and a corresponding light detector that responds to red or yellow light. In a space-saving arrangement, two LEDs illuminating the same point on the donor web are located adjacent the edge of the web. The yellow and red light pass through the dye frame of the moving donor web and illuminate a suitable photodetector. General alignment is accomplished by installing a sensor element in the donor passage past the thermal printhead and detecting the color frame after the donor emerges from the printhead. When detecting a frame after printing, each frame is provided with a length equal to the length between the print head and the detector, and there is a problem that it is useless.

[0007] It is therefore recognized that it is highly desirable to have a sensor that accurately senses the position and color of the donor web during printing to accurately record the color and minimizes wasted donors. . The present invention aims to overcome one or more of the above problems.

[0008]

SUMMARY OF THE INVENTION Briefly summarized, in accordance with one aspect of the present invention, there is provided an edge reading donor sensor for a thermal printer. The thermal printer includes a printhead and a drum, and a donor web passes through a passage between the printhead and the drum to perform thermal printing on a receiver. The edge read donor sensor is located at a nearby location where the donor web has been sent from the print area between the drum and printhead,
It is installed along the path of this web.

An edge reading sensor is installed close to the thermal print head. If the sensor detects the entry of a new color patch during the printing cycle, it stops the donor advance and properly aligns the donor with the receiver. Not all of the donors that occupy the portion after the alignment are used for printing,
Therefore, it is wasteful, and it is desirable to install the sensor as close as possible to the thermal line of the thermal head . Print drum, the physical form of the thermal head, and peripherals, the minimum distance achievable is limited, however, in the present invention can avoid this limitation. In the present invention, the sensor can be placed along the thermal head , and the sensor can be placed as close to the end of the print drum as possible. Thus, the donor can be sent slightly beyond the print drum and past the sensor.

It is an object of the present invention to precisely sense the dye-carrying donor web and to properly align it with the receiver, ensuring that the continuous color patches completely cover the image area. It is a feature of the present invention that this object is achieved by disposing a color identification photosensor in the donor transport direction on the donor passage at the location of the thermal head. If the sensor detects a new color intrusion during the printing cycle, it stops the donor advance and properly aligns the donor with respect to the receiver.

It is another object of the present invention to minimize donor waste due to improper alignment. This object is achieved by installing the sensor as close as possible to the heater line of the thermal head. An advantage of placing the sensor close to the heater line of the thermal head is that the unused portion of the sensor is effectively eliminated because it is in the printing position.

These and other aspects, objects, and aspects of the present invention
The features and advantages will be more clearly understood and appreciated by consideration of the following detailed description of the preferred embodiments and the appended claims and by reference to the accompanying drawings.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the drawings, the same reference numerals indicate similar elements and will be described below with reference to the drawings. FIGS. 1 and 3 show a thermal printer 10 having a thermal printhead 12 and a printer platen or drum 14. FIG. Dye receiver media sheet 16 is wrapped around drum 14. The dye donor supply web 18 is wound around a donor supply spool 20 and unwinds the thermal printer 10 onto a take-up spool 22 where the donor web 18 is wound up after use.

Drum 14 is positioned away from printhead 12 so that donor web 18 can pass between drum 14 and thermal printhead 12. Donor 18
Passes between the drum 14 and the thermal printhead 12 and the dye is wrapped around the print drum 14 from the donor web 18 by sublimation or the like.
6 is transferred. After the donor web 18 passes between the drum 14 and the print head 12, the donor web 18 is wound on a take-up spool 22.

The thermal printer 10 also includes two sets of donor sensors 24a, 24b and 26a, 26b. The sensors 24 and 26 are connected to the donor web 18
Any type of sensor can be used as long as it can detect the change in the color of the donor web 18 and the color frame of the donor web 18.
However, the donor sensors 24 and 26 are preferably infrared light sources and their detectors. Suitable sensors and detectors are disclosed in U.S. Pat.
No. 0,781.

More important than the type of sensor and detector used is the location of the sensor. Sensors 24, 26
As close as possible to the print drum 14 and the head 12
Must be installed along. Preferably, FIG.
The donor 18 slightly protrudes from the drum 14 as shown in FIG.
b, and the donor 18 can be routed between the two portions of 26a, 26b. Two LEDs on the sensor
A diagonal arrangement with reduced space is preferred, such that focuses on the same point on donor web 18.
With this configuration, each color patch on the donor web can be accurately detected.

We believe that the operation of the present invention will be apparent from the foregoing description and drawings, but will be supplemented for emphasis. In the color thermal printing process, continuous color patches and clear fusion patches (clear fusion) are used.
To ensure complete coverage of the image area by patching, the donor web 18 carrying the dye must be properly aligned with respect to the receiver 16. The present invention satisfies this need by placing the color identification optical sensors 24, 26 directly in the donor passage in the direction in which the donor 18 is transported. Sensor 24, 2
6 detects the presence of different color patches of donor 18 as donor 18 is advanced. If the sensors 24, 26 detect a new color intrusion during the printing cycle, the advance of the donor is stopped and the donor 18 is properly aligned with respect to the receiver 16. Not all of the donor occupying the portion after the alignment is used for printing and is therefore wasted, so that the sensor 2
4 and 26 are installed as close to the heater line of the thermal head 12 as possible.

Here, it can be recognized that the arrangement of the sensor for the thermal printer for performing high quality printing by properly aligning the donor with respect to the receiver has been shown. Thermal printers include a thermal printhead having a plurality of heating elements forming thermal lines. The print drum is located near the print head and spaced from the thermal line, and the receiver is mounted on the print drum. The dye-carrying donor web passes through the passage between the printhead and the drum and contacts the receiver for printing. A color identification light sensor is installed directly in the donor passage near the thermal heater line to detect different color patches as the donor is advanced.

Although the present invention has been described with particular reference to certain preferred embodiments, various modifications are possible, and within the scope of the invention, equivalent elements are replaced with elements of the preferred embodiment herein. The possibilities will be understood by those skilled in the art. For example, while the sensors have been shown and described as being arranged as diagonal pairs, other diagonal arrangements would be possible as long as the sensors can accurately detect different color patches. In addition, situations and materials with various modifications may be applied to the present disclosure without departing from the central disclosure of the present invention.

Here also, a sensor for a thermal printer is provided in which the donor is properly aligned with respect to the receiver to improve the recording of the color and to completely cover the image area with continuous color patches and, if necessary, clear color patches. It is recognized that the above arrangement is shown. This is accomplished by placing the sensor along the thermal head and as close to the edge of the print drum as possible, and sending the donor slightly over the print drum and passing between the sensors.

As will be apparent from the foregoing description, certain aspects of the present invention are not limited to the specific details of the illustrated example, and therefore, other modifications and adaptations may be made by those skilled in the art. It was done. It is therefore intended that the appended claims cover all such modifications and applications as do not depart from the true spirit and scope of the present invention.

[0022]

As described above, according to the present invention, the edge position of each color patch can be detected at the same position as the actual printing position by disposing the color identification optical sensor at the position of the thermal line. it can. This can eliminate waste caused by the separation between the color identification sensor and the thermal line.

[Brief description of the drawings]

FIG. 1 is a line side view of a thermal printer incorporating a donor sensor installed in accordance with the present invention.

FIG. 2 is a sectional view taken along line III-III in FIG. 1;

FIG. 3 is a schematic side view of a conventional thermal printer, illustrating the arrangement of a donor sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal printer 12 Thermal print head 14 Drum 16 Receiver 18 Dye donor supply web 20 Donor supply spool 22 Take-up spool 24a, 24b, 26a, 26b Donor sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-156089 (JP, A) JP-A-64-500416 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 17/02 B41J 2/325 B41J 17/36

Claims (1)

(57) [Claims] 1. A thermal print head having a plurality of heat generating elements forming a thermal line, a print drum mounted near the thermal print head, and a receiver held on the print drum. A print drum is mounted at a distance from the thermal line such that the receiver and the moving dye-bearing donor web can be located between the print drum and the printhead, wherein the dye-bearing donor web is It has color dyes as color patches of different colors arranged in a moving direction, moves on a path passing between the print head and the print drum, and moves between the print head and the print drum. On the side of the route The printing element is in contact with the receiver during printing, engages with the heating element along the thermal line, and selectively transfers dye from the dye-carrying donor web to the receiver. Detecting a color difference of a color patch on the dye-carrying donor web sent to the position of the line, and a color identification sensor arranged corresponding to the portion of the dye-carrying donor web protruding from the print drum; Having a thermal printer.