JPH01216860A - Thermosensitive recording apparatus - Google Patents

Abstract

PURPOSE:To obtain a high-quality recording image by correcting energy applied to each thermal resistor element using a correction value stored in a reference table and thereby correcting the non-uniformity of recording density due to the irregularity of a calorific value, when thermosensitive recording is performed by a thermosensitive recording head. CONSTITUTION:Image data of specified color is read from a storage device 24 by a host computer 22, and inputs image data into each first line buffer 28 by a single line of a thermosensitive recording head through an interface 26 in accordance with a command from an address controller. The image data is input to a gradation correction memory 30 to be subjected to gradation correction so that specified recording density is obtained. The image data whose gradation is corrected is input into an irregularity correction memory 32. The irregularity correction memory 32 corrects density irregularity in thermosensitive recording attributable to the irregularity of the resistance value or heat release value in a parallel direction of each thermal resistor element 8, using a correction value stored in the reference table of ROM. Thus the irregularity of the calorific value of the discrete thermal resistor 8 is eliminated, and image density is uniformized to correct the irregularity of a recording image.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a thermal recording device, and more particularly, to a thermal recording device that has a thermal recording head composed of a plurality of heating resistor elements and that obtains a recorded image by controlling the amount of heat generated by the heating resistor elements. Regarding improvements.

[Conventional technology]

Conventionally, a thermal recording head (also referred to as a thermal head) in which a plurality of heating resistor elements are arranged is provided, and the thermal recording head is brought into contact with a thermal recording medium, and the amount of heat generated by the heating resistor elements is controlled. 2. Description of the Related Art A thermosensitive recording device is used in which a recorded image is obtained on an image-receiving paper or the like by causing a physical or chemical change in a thermosensitive recording medium due to heat. The thermal recording head is constructed as shown in FIG. 5, for example. FIG. 5(A) is a plan view of the heating resistor element 8 of the heat-sensitive recording head viewed from the direction of the heat-sensitive recording medium. Further, FIG. 5(B) is a perspective view showing the heating resistor element 8 cut along the line BB in FIG. 5(A). As shown in FIG. 5(A), this thermal recording head is provided with a plurality of heating resistor elements 8 arranged in a row. As shown,
A resistor 14 that generates heat due to the current supplied from the driver circuit 10 through the strip-shaped electrodes 12, and these electrodes 12.
and a substrate 16 made of ceramic, for example, on which the resistor 14 is placed and fixed, and a glass-like substrate 16 provided between the resistor 14 and the substrate 16 to provide thermal resistance between the resistor 14 and the substrate 16. a glaze layer 18, and a protective layer 2 for covering and protecting the outer surfaces of the electrode 12 and the resistor 14.
It is mainly composed of 0 and 0. Note that FIG. 5(B) shows the heating resistor element 8 in a state where the protective layer 20 is seen through. When producing the heat generating resistor element 8 as described above, normally,
First, the outer surface of the resistor 14 is covered with the material of the electrode 12, and then the electrode material is etched to divide the electrode material so that gaps 12A are formed at predetermined intervals. Electrode 1 for passing current through
2 is formed. By the way, the resistance value of the resistor 14 is determined by the gap 1 between the electrodes 12.
2A and the material and dimensions of the resistor 14 itself (for example, the film thickness of the resistor). Therefore, due to the accuracy of the etching process and variations in the material and dimensions of the resistor 14 itself,
During manufacturing, the resistance value of the resistor 14 for each heating resistor element 8 may vary in the arrangement direction as shown in FIG. 6, for example. In addition, in the figure, each heating resistor element 8 in the arrangement direction is indicated by an address. The above-mentioned variations in resistance value cause non-uniformity in the amount of heat generated by each heating resistor element. When thermal recording is performed with a thermal recording head in which the amount of heat generated by each heating resistor element varies in this way, in a thermal recording device such as a facsimile that performs black and white binary recording, the recording density due to the variation due to binary storage is Unevenness is rarely a problem. However, in recent years, in order to obtain color recorded images, heat-sensitive recording apparatuses have been developed in which a high gradation recorded image is obtained by changing the amount of current (amount of energy) input to a heating resistor element, for example, Japanese Patent Laid-Open No. 62-209462. Sublimation transfer printers such as those described in the publication have come into use. When a thermal recording head such as the one described above is used in such a thermal recording device, the unevenness of the recording density may occur due to the above-mentioned variation in the amount of heat generated, and the desired quality of the recorded image cannot be obtained. A problem arises. To deal with such problems, conventionally, the voltage applied between the electrodes 12 is defined according to the resistance value of each resistor 14, and the voltage applied to the resistor 14 is
There is a method that eliminates variations in the amount of heat generated by each heating resistor element 8 due to variations in resistance value by flowing current through the resistor element 4, and a method that eliminates variations in the amount of heat generated by each heating resistor element 8 due to variations in resistance value, and a method that applies a voltage with a pulse width according to the resistance value of each resistor element 14. A method is known in which a current pulse is applied to the resistor 14 to eliminate the variation in the amount of heat generated.

[Problem to be solved by the invention]

On the other hand, in the thermal recording head, a plurality of heating resistor elements 8
Since they are arranged in a row as shown in FIG. The amount of heat dissipated is large. Therefore, in the conventional thermal recording apparatus, even if the amount of heat generated from the resistor 14 is made uniform as shown by the symbol H1 in FIG. Due to the difference in the amount of heat dissipated in different directions, the heat l emitted from the heating resistor elements 8 and contributing to thermal recording is uneven between both ends and the center of the arrangement of the heating resistor elements 8, as shown by reference symbol H2 in the figure. However, there was a problem in that the resulting profile would be uneven, resulting in density unevenness in the recorded image.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and by eliminating unevenness in the amount of heat that contributes to thermal recording in each heating resistor element of a thermal recording head, it is possible to uniformize recording density with high accuracy. It is an object of the present invention to provide a heat-sensitive recording device capable of obtaining high-quality recorded images without unevenness.

[Means to solve the problem]

The present invention provides a thermal recording apparatus which has a thermal recording head provided with a plurality of heating resistor elements and which obtains a recorded image by controlling the amount of heat generated by the heating resistor elements. A means for storing a reference table storing correction values corresponding to the actual heat generation amount of the heating resistor element, and when performing thermal recording with the thermal recording head,
means for correcting the energy applied to each heating resistor element using the correction value stored in the reference table, and correcting non-uniformity in recording density due to variation in the amount of heat generated by each heating resistor element. By doing so, the above objective has been achieved.

[Effect] When obtaining a recorded image by thermal recording using a thermal recording head provided with a plurality of heating resistor elements, the recording density by each heating resistor element is determined by the amount of heat generated from the resistor in the heating resistor element alone. It is determined by the amount of heat that actually contributes to thermal recording, taking into account the amount of heat released. The inventor has devised the present invention as a result of various studies taking this point into consideration. In the present invention, a reference table storing correction values corresponding to the actual heat generation amount of each heating resistor element detected in advance is stored, and when performing thermal recording with the thermal recording head, the reference table is stored. The energy applied to each heat-generating resistor element is corrected using the correction value stored in the heat-generating resistor element, thereby correcting non-uniformity in recording density due to variations in the heat-generating layer of each heat-generating resistor element. Therefore, it is possible to eliminate non-uniformity in the amount of heat that contributes to actual thermosensitive recording, which is caused by non-uniformity in the resistance values of the individual heating resistor elements and differences in the amount of heat radiated by each of them. Therefore, it is possible to uniformize the recording density with high accuracy and obtain a high-quality recorded image without unevenness. 【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. This embodiment is based on a thermal recording device that obtains color recorded images by thermally transferring the sublimable dye from a transfer film coated with the sublimable dye to a predetermined image receiving paper (thermal sublimation transfer). This is an application of the invention. FIG. 1 shows a block diagram showing a signal processing system of a thermal recording apparatus according to this embodiment. As shown in the figure, this thermal recording device includes a host computer 22 that outputs a thermal recording command, a signal processing section 23A that processes image data based on the output command, and a signal processing unit 23A that processes image data on a receiving paper using a signal of the processed image data. It is provided with a recording control section 23B for controlling thermal recording, and a thermal head (corresponding to a thermal recording head) 39 having a heating resistor element 8 configured as shown in FIG. 15 mentioned above. That is, the host computer 22 includes a storage device 24 for storing image data to be thermally recorded, and an interface (1/F) 26 for inputting and outputting signals between the host computer 22 and the recording control section 23B. are connected. Image data output from the host computer 22 via this interface 26 is input to the first line buffer 28 in the signal processing section 23A. Two first line buffers 28 are provided, and they are switched alternately to temporarily store the input image data until it is processed in a later process, and also to transfer the stored data to one of the heating resistor elements 8. Each line of image data is output to the gradation correction memory 30. The gradation correction memory 30 performs gradation correction on image data as necessary, and stores data used for the gradation correction (hereinafter referred to as gradation correction data) in a random access memory (
(hereinafter referred to as RAM). Since this gradation correction data is stored in the RAM, the gradation of the image data can be freely set and corrected by commands from the host computer 22. The image data output from the tone correction memory 30 is
The data is input to the unevenness correction memory 32 according to the present invention. The unevenness correction memory 32 is a read-only memory (hereinafter referred to as ROM) that stores uneven recording density caused by variations in the resistance value and heat dissipation amount of each heating resistor element 8 during thermal recording.
The correction is performed using the correction values stored in the reference table inside. The Ryōkai data corrected by the unevenness correction memory 32 is stored in the second
The signal is temporarily stored in the line buffer 34 and input to the parallel-to-serial converter 36. This second line buffer 34 has two
At the same time, the input image data is stored at one time until it is processed in a later process by switching alternately, and the stored data is parallel-serial converted for each line of image data of the heating resistor element 8. The information is input to the section 36. Note that in order to correct unevenness in thermal recording in the direction in which the heating resistor elements 8 of the thermal head 39 are lined up for each line of the heating resistor elements 8, each of the first and second line buffers 2
8.34 and the unevenness correction memory 32 are configured to process the image data inputted line by line in parallel by the address controller 38. This image data that is processed in parallel is called parallel data. The parallel-to-serial converter 36 converts the parallel data into serial data for controlling the amount of heat generated by the heating resistor element 8 of the thermal head 39. The serial data for a predetermined number of pixels converted by this parallel-to-serial converter 36 is
The signal is input to a shift register 40 in the recording control unit 23B as shown in FIG. This shift register 40 shifts the serial data when a clock signal is input, and the shift register 4o is connected to a latch circuit 42. This latch circuit 42 latches the data in the shift register 40 by inputting a latch signal, and is connected to the signal input side of the Nant gate 44. A strobe control memory 48 is also connected to the signal input side of the Nant gate 44. This Nant gate 44 is an element that digitally controls the current flowing through the resistor 14 of each heating resistor element 8 by turning it on and off via the driver circuit 10 shown in FIG. 5 above based on an input signal. The strobe control memory 48 controls the electric energy flowing from the power supply 50 into the heat generating resistor element 8 along with the serial data input from the latch circuit 42 to the Nant gate 44 according to the strobe signal input to the Nant gate 44. The amount of heat generated by the heating resistor element 8 is controlled. The strobe control memory 48 also has memory for controlling the energization time of each heating resistor element 8 so as to correct the basic density characteristics of the thermally recorded image so that it has a linear relationship with the input image data. An energization time control table is provided. Here, FIG. 3(A) shows a mechanism for sublimation transfer onto the image receiving paper 54 using the thermal head 39 and the transfer drum 52. In addition, the same figure (B) shows three thermal heads and image receiving paper 5.
4 shows an enlarged view of the abutting portion. As shown in the figure, the image receiving paper 54 is wound around the circumferential surface of a cylindrical transfer drum 52, and the thermal head 39 comes into contact with a predetermined position of the image receiving paper 54 via the transfer film 56. This transfer film 56 contains a sublimable dye, and the dye is sublimated by heating with the thermal head 39 and is attached and transferred onto the image receiving paper 54 . The transfer film 56 is a well-known one comprising a thermal transfer layer 56A1 containing a sublimable dye in a binder resin, a substrate 56B for supporting the thermal transfer layer 56A, and the like. Furthermore, the transfer film 56 is coated with cyan (C).
), magenta (M), yellow (Y), and black (K). I try to get meetings. The effects of the embodiment will be explained below. Before starting the thermal recording device according to the embodiment, a correction value to be stored in the reference table is obtained, and R of the unevenness correction memory 32 is
Store it in OM. This stored correction value is determined as follows. That is, before correction and with image data of uniform density input, the amount of heat generated from each heating resistor element 8 of one line provided in the thermal head 39 is determined by thermal recording (in the case of the embodiment, thermal transfer). ) is detected, and the density characteristics of the heat-sensitive recording with respect to the detected heat amount of each heating resistor element 8 are measured. Specifically, first, in a state where no correction value is stored in the reference table and a uniform density signal with bare characteristics is input, thermal recording is performed on the image receiving paper 54 by the thermal head 39. A recording surface @ (indicated by the symbol ■ in the figure) as shown in Figure (A) is created. As shown in Figure (B), which is an enlarged view of the part indicated by the symbol ■1 in Figure (A), a minute opening (aperture) corresponding to the size of each dot 57 of the created recorded image is formed.
Densitometer (e.g. microdensitometer) with 58
At step 60, the density of the recorded image is detected. An example of this detection signal is shown in FIG. Next, as shown in FIG. 3C, the maximum value of the detection signal is sampled, the magnitude of the sampled maximum value is reversed, and each line of one line provided on the thermal head 39 is A correction value corresponding to the heating resistor element 8 is created. Here, when the thermal recording apparatus is started, the host computer 22 first reads image data of a desired color among cyan, magenta, yellow, and black from the storage device 24, and sends the image data to the address controller 38 via the interface 26. The image data is input to each first line buffer 28 for each line of the thermal recording head according to a command. The image data once stored in the first line buffer 28 is input to a gradation correction memory 30, and gradation correction is performed to obtain a recording density as required. The gradation correction data used to correct the gradation of this image data is stored in RAM.
The gradation of image data can be freely set and corrected according to instructions from the host computer 22. Thereby, the tone of the recorded image, such as highlights, shadows, and halftones, for each color, ie, cyan, magenta, yellow, and black, is adjusted as necessary. The image data subjected to tone correction as described above is input to the unevenness correction memory 32. The unevenness correction memory 32 refers to a reference table in the ROM and uses the correction values stored in the reference table to detect variations in the resistance value of each heating resistor element 8 or the amount of heat dissipated in the arrangement direction. Correct density unevenness in thermal recordings. This eliminates variations in the amount of heat generated by the individual heating resistors 8 during thermal recording, makes the image m degree uniform, and corrects unevenness of the recorded image. One line of image data subjected to unevenness correction in this manner is input to the parallel-to-serial converter 36 via the second line buffer 34. This input image data is created with parallel data in which each pixel has a predetermined bit, for example, 8 bits, and the parallel-to-serial converter 36 converts the input parallel data into each pixel data for driving the thermal head 39. It is converted into signal data represented by 1 and O, that is, serial data, according to the density (gradation) of the signal. If the pixel data to be converted is, for example, a density of 128 gradations among 256 gradations, this serial data is obtained as 128 consecutive "1's" followed by 128 consecutive rOJs. The image data of a predetermined number of pixels converted to serial data is
The signal is input to the shift register 40. The shift register 4
0 causes input data to be shifted to a predetermined position by a clock signal. Thereafter, when a latch signal is input to the latch circuit 42, the serial data is set in the latch circuit 42. At this time, when a strobe signal is applied from the strobe control memory 48, the Nant gate 44 is turned on, so current flows from the power supply 50 to the heating resistor element 8 via the driver circuit 10, and the heating resistor element 8 Generates heat due to the energy of the current. Due to this heat generation, the sublimable dye of the transfer film 56 is sublimated, and thermal recording is performed on the image receiving paper 54 based on the serial data. During thermal recording as described above, the strobe control memory 48 uses the energization time control table stored in the strobe control memory 48 to
By controlling the energization time of the Nant gate 44 using a strobe signal, the recording material to be thermally recorded by the thermal recording head 39 (in the case of the embodiment, the transfer film 56 and the image receiving paper 54
) is corrected so that the basic density characteristic for the input image data becomes linear. In this way, storage device 2
A recorded image having a density characteristic linearly related to the image data stored in 4 can be obtained on the receiving paper 54. Note that since the recording density is determined by the length of time during which the heating resistor element 8 is energized, the recording density is corrected by controlling the length of the energization time using the strobe signal. Thermal recording by thermal transfer as described above is performed for each color of cyan, magenta, yellow, and black to create a color recorded image on the image receiving paper 54. In the above embodiments, a thermal recording apparatus employing a thermal sublimation transfer system as a thermal recording system was exemplified, but the thermal recording system of the apparatus to which the present invention is applied is not limited to this. That is, other heat-sensitive recording methods, such as a heat-sensitive melt transfer recording method in which a colored wax layer coated on a film is transferred onto a paper surface using heat, may also be used.

【Effect of the invention】

As explained above, according to the present invention, by eliminating nonuniformity in the amount of heat that contributes to thermal recording of each heating resistor element, it is possible to uniformize the recording density with high accuracy and obtain a high-quality recorded image without unevenness. The excellent effect of being able to do this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a signal processing system of a thermal recording device according to an embodiment of the present invention, FIG. 2 is a main circuit diagram showing the configuration of a thermal recording head provided in the thermal recording device, and FIG. Figures 3 (A) and (B) are sectional views of main parts showing the state in which the thermal head is in contact with the image receiving paper, and Figure 4 (A) is a cross-sectional view for explaining the procedure for calculating correction values to be stored in the reference table. , a plan view showing an example of a recorded image, FIG. FIG. 6 is a plan view showing the heat-sensitive recording head; FIG. A diagram showing an example of the resistance value profile for each address. FIG. 7 is a diagram showing an example of the heat generation profile when the resistance value profile of each heating resistor element is made uniform. 8... Heating resistor element, 10... Driver circuit, 12... Electrode, 14... Resistance layer, 18... Glaze layer, 20... Protective layer, 22... Host computer, 24... Storage device, 26... Interface (1/F), 28... First line buffer, 30... Gradation correction memory, 32... Unevenness correction memory. 34... Second line buffer, 36... Parallel-serial converter, 38... Address controller, 39... Thermal head, 40... Shift register, 42... Latch circuit, 44...・Nant Gate, 48... Strobe control memory, 50...
Power supply, 54... Image receiving paper, 56... Transfer film.

Claims (1)

[Claims] (1) In a thermal recording device that has a thermal recording head provided with a plurality of heating resistor elements and obtains a recorded image by controlling the amount of heat generated by the heating resistor elements, individual heat generation detected in advance means for storing a reference table storing correction values corresponding to the actual heat generation amount of the resistor element; and means for storing the correction values stored in the reference table when performing thermal recording with the thermal recording head. A thermal recording device comprising: means for correcting the energy applied to each heat generating resistor element using the above, and correcting non-uniformity in recording density due to variation in the amount of heat generated by each heat generating resistor element.