JPH1029337A - On-state resistance correcting method for thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-state resistance correcting method for thermal head in which the fabrication yield of IC in a control circuit for heat elements in the thermal head can be increased while reducing the fabrication cost. SOLUTION: In a thermal image recorder where a plurality of heat elements in a thermal head are controlled using a plurality of semiconductor integrated circuits each of which controls a predetermined number heat elements, a thermal record image is formed on a thermal recording material using an identical image data and the density at each region of the thermal record image corresponding to each semiconductor integrated circuit is measured. Subsequently, the ratio between the energy supply to the thermal head required for obtaining a density corresponding to the image data and the energy supply to the thermal head corresponding to the density at each region is calculated in order to obtain a data for correcting the image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal image recording apparatus (hereinafter, referred to as a thermal recording apparatus), which is a control circuit for controlling the on-state and off-state of each heating element of a thermal head. The present invention relates to a method for correcting density unevenness caused by variation in ON resistance of a switching element of an IC).

[0002]

2. Description of the Related Art Thermal image recording using a heat-sensitive recording material (hereinafter referred to as a heat-sensitive material) formed by forming a heat-sensitive recording layer on paper, a film or the like as a support is used for recording an ultrasonic diagnostic image. I have. In addition, thermal image recording has advantages such as elimination of wet development processing and simplicity of handling. In recent years, not only small-sized image recording such as ultrasonic diagnosis but also MRI diagnosis and X-ray For applications requiring large and high-quality images, such as diagnostics, the use of these in image recording for medical diagnosis is also being studied.

[0003] As is well known, in a thermal recording apparatus,
Using a thermal head having a glaze in which heating elements corresponding to the number of pixels in one line are arranged in one direction, with the glaze slightly pressed against the heat-sensitive recording layer of the heat-sensitive material, By heating each of the glaze heating elements according to the image data of the recorded image while relatively moving in a direction substantially orthogonal to each other, the thermosensitive recording layer of the thermosensitive material is heated to perform image recording.

FIG. 5 is a conceptual diagram of the thermal head and its control circuit. In the figure, the glaze 82 of the thermal head 66 is composed of a plurality of heating elements 84. The control circuit 86 includes a plurality of semiconductor integrated circuits (ICs) 88, and each IC 88 includes a plurality of switch elements 90. The heating element 8
4 is connected to the power supply, and the other end is connected to one end of the corresponding switch element 90, and the switch element 9
The other end of 0 is connected to the ground.

The thermal head 66 is for recording on a B4 size heat-sensitive material at a pixel density of 300 dpi. Here, the thermal head 66 has 3072 heating elements 84, and the resistance value of each heating element 84 is about 3 kΩ. And Also,
The control circuit 86 controls the ON state or the OFF state of each heating element 84, and here, each I
The C88 has 64 switching elements 90, and the heating elements 84 are individually controlled by the ICs 88 of a total of 48 control circuits 86.

A predetermined constant voltage is supplied to a power supply of the thermal head 66, and a control input terminal of the switch element 90 is
For example, a pulse-modulated signal obtained by modulating the image data of a recording image with a pulse width or a pulse number is input, and its ON state or OFF state is individually controlled. That is, the individual heating elements 84 are energized for a time during which the switch element 90 is turned on by a pulse modulation signal in accordance with the resistance value and the voltage of the supplied power supply, and the amount of generated heat is controlled with high precision. .

The switch element 90 of the IC 88 of the control circuit 86 has a so-called on-resistance when turned on. The on-resistance value of the switch elements 90 hardly varies between the switch elements 90 inside the individual ICs 88, but may vary greatly between the switch elements 90 of the respective ICs 88. Therefore, the amount of heat generated by each of the heat generating elements 84 varies depending on the on-resistance value of the switch element 90 of the IC 88, and there is a problem that density unevenness may occur.

For example, in a thermal recording device for medical diagnosis,
If the difference between the on-resistance values of the switch elements 90 of each IC 88 is 0.2% or more of the resistance value of the heating element 84, the density unevenness becomes conspicuous. Therefore, in the thermal head 66 in the illustrated example, when a so-called solid image is formed on the entire surface of the heat-sensitive material using the same image data when there is a difference of 6Ω or more, about 5.4 in the horizontal direction.
Vertical stripe-shaped density unevenness having a width of mm is generated.

[0009] The occurrence of such density unevenness leads to a decrease in the image quality of a finished recorded image, and in particular, in the medical field where high-quality image recording is required, it may lead to a diagnosis error, which is serious. It becomes a problem. For this reason, the ICs are selected so that the absolute value of the difference between the ON resistances of the switch elements 90 of the individual ICs 88 of the control circuit 86 is equal to or less than a predetermined value. There is a problem that the cost decreases and the cost increases.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the production yield of an IC of a control circuit for controlling a heating element of a thermal head in view of various problems based on the prior art. An object of the present invention is to provide a thermal head on-resistance correction method capable of reducing manufacturing costs.

[0011]

In order to achieve the above-mentioned object, the present invention provides a thermal head having a plurality of semiconductor integrated circuits for controlling a predetermined number of a plurality of heating elements. In a thermal image recording apparatus that controls a plurality of heating elements, a thermal recording image is formed on a thermal recording material using the same image data, and the density value of each region of the thermal recording image corresponding to each of the semiconductor integrated circuits is determined. Measure,
Correction by calculating the ratio between the amount of energy supplied to the thermal head required to obtain the density value corresponding to the image data and the amount of energy supplied to the thermal head corresponding to the density value of each area An object of the present invention is to provide an on-resistance correction method for a thermal head, wherein data is created and image data is corrected using the correction data.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of one embodiment of a thermal recording apparatus to which the correction method of the present invention is applied. The illustrated thermal recording apparatus 10 is for performing thermal image recording on a thermal recording material such as a thermal recording film A (hereinafter referred to as a thermal film A) of a predetermined size, and is a magazine in which the thermal film A is stored. The loading unit 14 in which the cartridge 24 is loaded, and the supply / transport unit 1
6. It has a recording section 20 for recording a thermal image on the thermal film A by the thermal head 66, a discharge section 22, and the like.

The heat-sensitive film A is formed by forming a heat-sensitive recording layer on one surface of a transparent film such as a transparent polyethylene terephthalate (PET) film as a support. Units (bundles) are stored in the magazine 24 and are taken out of the magazine 24 one by one and provided for thermal image recording.

The loading section 14 is provided in the housing 2 of the thermal recording apparatus 10.
8, guide plate 32, guide roll 3 formed in 8
4, 34 and a stop member 36. The magazine 24 is inserted into the insertion opening 3 of the loading section 14 with the lid 26 side first.
0 to the inside of the thermal recording apparatus 10 and the guide plate 32
While being guided by the guide rolls 34, 34, the thermal recording device 10 is pushed down to a position where it contacts the stop member 36.
At a predetermined position.

The supply and transport section 16 takes out the thermal film A from the magazine 24 loaded in the loading section 14 and transports the thermal film A to the recording section 20, and uses a sucker 40 that sucks the thermal film A by suction. It has a leaf mechanism, a transport means 42, a transport guide 44, and a pair of regulating rollers 52 located at the outlet of the transport guide 44.

The transport means 42 includes a transport roller 46, a pulley 47a coaxial with the transport roller 46, a pulley 47b connected to a rotary drive source, a tension pulley 47c, an endless belt 48 stretched over these three pulleys, It includes a nip roller 50 pressed by the roller 46 and the like.

In the thermal recording apparatus 10, when a recording start is instructed, the cover 26 of the magazine 24 is opened by an opening / closing mechanism (not shown), and the heat-sensitive film is transferred from the magazine 24 by a single-sheet mechanism using a suction cup 40. A is taken out, and the leading end of the thermal film A is supplied between the transport roller 46 of the transport means 42 and the nip roller 50. When the heat-sensitive film A is nipped between the transport roller 46 and the nip roller 50, suction by the suction cup 40 is released,
The supplied thermal film A is transported along the transport guide 44.

When the heat-sensitive film A to be used for recording is completely discharged from the magazine 24, the lid 26 is closed by the opening / closing means. The distance from the conveyance means 42 defined by the conveyance guide 44 to the regulating roller pair 52 is set slightly shorter than the length of the heat-sensitive film A in the conveyance direction. After reaching the regulating roller pair 52, the regulating roller pair 52 is initially stopped, and the leading end of the heat-sensitive film A stops here.

The leading end of the heat-sensitive film A is a pair of regulating rollers 52.
Is reached, the temperature of the thermal head 66 is confirmed. If the temperature of the thermal head 66 is a predetermined temperature, the conveyance of the heat-sensitive film A by the regulating roller pair 52 is started, and the heat-sensitive film A is conveyed to the recording unit 20. Is done.

The recording section 20 has a thermal head 66, a platen roller 60, a cooling fan 76 for cooling the thermal head 66, a cleaning roller pair 56, a guide 58, a guide 62, a transport roller pair 63, and the like.

In the illustrated example, the thermal head 66
A thermal head body for performing thermal image recording with a predetermined pixel density (recording density), wherein a thermal head body in which a glaze in which heating elements for performing thermal recording for one line are arranged in one direction on a thermal film A; A heat sink fixed to the thermal head body. The thermal head 66 is supported by a support member 68 that is rotatable about a fulcrum 68a in the direction of arrow a and in the opposite direction.

The platen roller 60 rotates at a predetermined image recording speed while holding the heat-sensitive film A at a predetermined position, and conveys the heat-sensitive film A in a direction substantially perpendicular to the glaze extending direction. The cleaning roller pair 56 is a roller pair including an adhesive rubber roller and a normal roller.

In the recording unit 20, before the thermal film A is conveyed, the support member 68 is rotated upward (in the direction opposite to the direction of arrow a), and the glaze of the thermal head 66 and the platen roller 60 Not in contact. When the conveyance is started by the above-described regulating roller pair 52,
The heat-sensitive film A is nipped by the cleaning roller pair 56 and further conveyed while being guided by the guide 58.

When the leading end of the heat-sensitive film A is transported to the recording start position (the position corresponding to the glaze), the supporting member 68
Is rotated in the direction of arrow a, the thermal film A is sandwiched between the glaze of the thermal head 66 and the platen roller 60, and the glaze is pressed against the recording layer. Next, the heat-sensitive film A is transported by the platen roller 60, the pair of regulating rollers 52, the pair of transport rollers 63, and the like while being held at a predetermined position by the platen roller 60.

With this conveyance, each of the glaze heating elements is heated in accordance with the recorded image, so that the heat-sensitive film A
The thermal image recording is performed. The thermal film A on which the thermal image recording has been completed is transported by the platen roller 60 and the transport roller pair 63 while being guided by the guide 62,
The sheet is discharged to the tray 72 of the discharge section 22. The tray 72 is
Thermal recording device 1 through discharge port 74 formed in housing 28
The heat-sensitive film A, which protrudes to the outside and has an image recorded thereon, is discharged to the outside through the discharge port 74 and is taken out.

A thermal recording apparatus to which the method for correcting the on-resistance of a thermal head according to the present invention is applied is constituted, for example, as described above. Next, a method for correcting the on-resistance of the thermal head according to the present invention will be described.

The thermal head and its control circuit are referred to the conceptual diagram shown in FIG. 5, and the circuit configuration is the same. That is, the thermal head uses a B4 size heat-sensitive material of 300 mm.
The recording is performed at a pixel density of dpi, and 3072
The semiconductor integrated circuit (I
C) has 64 switching elements, and the heating elements are individually controlled by a total of 48 control circuit ICs.

First, a so-called solid image is formed on the entire surface of the heat-sensitive film A using the same image data. At this time, if the variation of the on-resistance of the switch element among the ICs of the respective control circuits is within a predetermined range, for example, within 6Ω in the case of the thermal head 66 of the present embodiment, the entire surface of the heat-sensitive film A is , An image of the same density corresponding to the image data is formed. On the other hand, if the variation is equal to or more than the predetermined range, the heat-sensitive film A has about 5.
Vertical stripe-shaped density unevenness having a width of 4 mm occurs.

FIG. 2 shows a conceptual diagram of one embodiment of a recorded image recorded using the same image data. The recorded image shown in FIG. 2 has two density irregularities in the form of vertical stripes having a width of about 5.4 mm corresponding to the horizontal width of one IC 88. For example, the density is smaller than the density corresponding to the image data. Area A where a low-density image is formed and area B where an image with a density substantially corresponding to image data is formed.
And an area C where an image having a higher density than the density corresponding to the image data is formed.

Next, the density values of the areas A, B, and C are actually measured using, for example, a densitometer, and the density values of the areas A, B, and C are referred to with reference to the characteristic curve of the thermosensitive recording material shown in FIG. Is obtained for the amount of energy supplied to the thermal head 66. The graph shown in FIG. 3 shows the relationship between the recording density of the thermal film A and the energy supplied to the thermal head 66. The vertical axis represents the recording density (D) of the thermal film A, and the horizontal axis represents the thermal head. The energy supply (log E) to 66 is shown.

Finally, as shown conceptually in FIG.
Recording density corresponding to image data, that is, heat-sensitive film A
The amount of energy supplied to the thermal head 66 corresponding to the density to be recorded in the areas A, B, and C;
That is, the ratio (ratio) of the amount of energy supplied to the thermal head 66 corresponding to the density actually recorded on the thermal film A is calculated, and this is turned on by the switch element of the IC of the control circuit of the thermal head 66. The image data is multiplied as resistance correction data.

The conceptual diagram of the correction data shown in FIG. 4 corresponds to the output recorded image of FIG. 2, and is applied to the thermal head 66 corresponding to each area A, B, C of the thermal film A. FIG. 3 conceptually shows an increase and a decrease in the supplied energy amount. According to the correction data, the amount of energy supplied to the thermal head 66 is increased or decreased, and as a result,
The recording density of the heat-sensitive film A can be increased or decreased, and the density to be recorded and the actually recorded density can be matched.

As described above, according to the thermal head on-resistance correcting method of the present invention, an image having a density corresponding to image data can be obtained regardless of the variation in the on-resistance of the switch element of the IC of the thermal head control circuit. Since recording can be performed, it is possible to prevent the occurrence of density unevenness in the recorded image due to the variation in the ON resistance value of the switch element, and to reduce the production yield of the IC of the control circuit to almost 100%. And the manufacturing cost can be reduced.

The method of correcting the on-resistance of the thermal head according to the present invention has been described above with reference to an example of the thermal recording apparatus. However, the present invention is not limited to the above-described embodiment.
It goes without saying that the present invention can be applied to all conventionally known thermal recording apparatuses using a thermal head. Further, it goes without saying that various improvements and changes may be made without departing from the spirit of the present invention.

[0036]

As described in detail above, according to the thermal head on-resistance correction method of the present invention, the control circuit I
It is possible to prevent the occurrence of density unevenness in the output recorded image due to the variation in the ON resistance value of the C switch element, to reduce the production yield of the control circuit IC to almost 100%, and to reduce the production cost. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one embodiment of a thermal image recording apparatus using the present invention.

FIG. 2 is a conceptual diagram of an example of a recorded image.

FIG. 3 is a graph of one example of a characteristic curve of a thermosensitive recording material.

FIG. 4 is a conceptual diagram of an embodiment of correction data.

FIG. 5 is a conceptual diagram of a thermal head and a control circuit thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal image recording apparatus 14 Loading part 16 Supply / conveyance part 20 Recording part 22 Ejection part 24 Magazine 26 Cover 27 Sponge 28 Housing 30 Insertion port 32 Guide plate 34 Guide roll 36 Stop member 40 Suction cup 42 Transport means 44 Transport guide 46 Transport roller 47a, 47b pulley 47c tension pulley 48 endless belt 50 nip roller 52 regulating roller pair 56 roller pair 58, 62 guide 60 platen roller 63 transport roller pair 66 thermal head 68 support member 68a fulcrum 72 tray 74 discharge port 82 glaze 84 heating element 86 control Circuit 88 Semiconductor integrated circuit (IC) 90 Switch element A Thermal film

Claims (1)

[Claims] 1. A thermal image recording apparatus for controlling a plurality of heating elements of a thermal head by using a plurality of semiconductor integrated circuits for controlling a predetermined number of a plurality of heating elements of a thermal head. A heat-sensitive recording image is formed on the heat-sensitive recording material using the data, and the density value of each area of the heat-sensitive recording image corresponding to each of the semiconductor integrated circuits is measured to obtain a density value corresponding to the image data. Calculating the ratio between the amount of energy supplied to the thermal head and the amount of energy supplied to the thermal head corresponding to the density value of each of the regions, to create correction data, and use the correction data to generate image data. And correcting the on-resistance of the thermal head.