JPH05261953A - Thermal head - Google Patents

Abstract

PURPOSE:To shorten the printing process time and prevent the thermal energy from being lost or an unevenness of a recording image from happening. CONSTITUTION:On a thermal head 1, a heating unit for gradation expression 4 and heating unit for bias heating 5 are provided. One of the heating units is tilted to a ceramic substrate 3 so that both of the two heating units 4, 5 are appropriately brought into contact with the outer peripheral surface of a platen drum. The heating unit for bias heating 5 generates a bias thermal energy right before a heat-sensitive coloring layer develops a color. The heating unit for gradation expression 4 generates a thermal energy for gradation expression in response to the density of picture elements to be recorded. These bias thermal energy and thermal energy for gradation expression are given on a color heat-sensitive recording material, and respective picture elements develop color of desired densities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal printer or a thermal transfer printer. More specifically, two types of heat generating portions are provided to separately perform auxiliary heating such as bias heating and gradation expression. It relates to the thermal head.

[0002]

2. Description of the Related Art Thermal recording includes thermal transfer recording in which ink of an ink film is transferred onto a recording paper and thermal recording in which a thermal recording paper is heated to develop a color. For example, in a color thermal printer, a thermal head is brought into contact with a color thermal recording material to record a full-color image on the color thermal recording material by three-color sequential thermal recording. As a color thermosensitive recording material, for example, as described in JP-A-61-213169, a magenta thermosensitive coloring layer, a cyan thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially formed on a support. In order to selectively develop the color of each thermosensitive coloring layer, the thermosensitive coloring layers have different thermal energies required for coloring, and the deeper thermosensitive coloring layers require higher thermal energy. Further, when recording the next thermosensitive coloring layer, in order to prevent the thermorecording thermosensitive recording layer on the next thermosensitive coloring layer from being recorded again, an electromagnetic wave peculiar to the thermorecorded thermosensitive coloring layer is irradiated. Light fixing.

In order to develop the color of each of the thermosensitive coloring layers, the thermal energy immediately before the coloring (hereinafter referred to as bias thermal energy) is changed to the thermal energy for developing the desired density (hereinafter referred to as gradation expression heat). Energy) is required to add color heat energy. As described above, the bias heat energy has a larger value in the deeper thermosensitive coloring layer. A conventional thermal head includes a row of heat generating elements in which heat generating elements are arranged in a line, and the heat generating elements are composed of a number of heat generating elements corresponding to the number of line pixels. As shown in FIG. 13, in the case of thermally recording a pixel having a density level of “I”, the heating element is first operated for a fixed time (time A).
When energized, bias thermal energy is applied to the color thermosensitive recording material. Next, within a time period B, I pulse currents are supplied to the heating elements to apply the gradation expressing heat energy to the color thermosensitive recording material. Generally, when expressing 64 gradations, 63 pulse currents are given to the heating element.

[0004]

In the above-described conventional thermal head, since the bias heating and the gradation expression are performed by one heating portion, the recording time for one line is the cooling time C.
(A + B + C) time, which is a disadvantage that the printing time becomes long. In addition, there is a variation in the resistance value of each heating element, which may cause density unevenness and gradation unevenness. In order to correct this, a method of correcting gradation data for each pixel is generally used, but this method can only perform density correction for each gradation. Further, there is a method of adding the number of gradations corresponding to the correction energy in order to improve the correction accuracy, but this method has a drawback that the recording speed becomes slow. Therefore, the present applicant has proposed a thermal head in which two heating parts are provided in one thermal head to perform bias heating and gradation expression separately (Japanese Patent Application No. 2-412414).

However, in this thermal head,
Two heat generating parts having the same shape are arranged side by side on a flat substrate, and at least one of the heat generating parts does not properly contact the arcuate outer peripheral surface of the platen drum. .. Therefore, heat energy may be lost, or the recorded image may be uneven.

It is an object of the present invention to provide a thermal head which shortens the print processing time and prevents heat energy loss and recorded image unevenness.

[0007]

In order to achieve the above object, the thermal head of the present invention is provided with a heat generating portion for auxiliary heating in addition to a heat generating portion for gradation expression, and these heat generating portions include a platen. To ensure proper contact with the outer peripheral surface of the drum,
At least one heat generating portion is tilted along the outer peripheral surface of the platen drum. Further, two heat generating portions for gradation expression and auxiliary heating are laminated via a planar insulating layer, and the heat generating portion for auxiliary heating is formed in a flat plate shape parallel to the insulating layer.

[0008]

EXAMPLE In FIG. 2, a thermal head 1 has a ceramic substrate 3 mounted on a head substrate 2 on which a gradation expression corresponding to a color density of a pixel is generated for gradation expression for generating thermal energy. A heat generating part 4 and a bias heating heat generating part 5 for generating a constant bias heat energy are provided in parallel. Since these heat generating parts 4 and 5 are inclined by an angle θ in a direction in which they face each other,
Are brought into proper contact with the color thermosensitive recording material 14 wound around the platen drum 13, respectively.

In the gradation expressing heat generating portion 4, a plurality of heat generating elements 4a to 4n (see FIG. 8) for recording each dye are arranged along a direction perpendicular to the paper surface. The bias heating element 5 also has a plurality of heating elements 5a to 5n arranged in a direction perpendicular to the paper surface. In this embodiment, the heating element 5 for bias heating is divided into a plurality of heating elements 5a to 5n so as to correspond to the heating elements 4a to 4n for gradation expression. In addition, one heating element for bias heating may be provided, or one continuous heating element for bias heating may be provided.

In FIG. 1, the ceramic substrate 3 has a horizontal surface 3a and a surface 3b inclined by an angle θ with respect to the surface 3a.
Are formed. Cylindrical planar partial glazes 6 and 7 are formed on these surfaces 3a and 3b, respectively, and a resistor 8
Are stacked. This resistor 8 has a partial glaze 6
The A electrode 9 is joined to the side, and the B electrode 10 is joined to the partial glaze 7 side, and the common electrode 11 is joined to the intermediate portion of the partial glazes 6 and 7. The portion of the resistor 8 between the A electrode 9 and the common electrode 11 constitutes a heating element for gradation expression, and when a voltage is applied between these electrodes, the heating element 4a generates heat. The heating element for bias is constituted by the resistor 8 between the B electrode 10 and the common electrode 11, and the heating element 5a generates heat when a voltage is applied between these electrodes. In addition, the resistor 8, A
A wear-resistant layer 12 is coated on the electrodes 9, B electrode 10, and common electrode 11.

FIG. 3 shows a color thermal printer using the thermal head of the present invention. The platen drum 13 holds the color thermosensitive recording material 14 on its outer periphery,
It is rotated by a pulse motor (not shown) during thermal recording. A clamp member 15 is attached to the platen drum 13, and at least one position, for example, the tip of the color thermosensitive recording material 14 is fixed to the platen drum 13. The clamp member 15 is U-shaped, and elongated holes 15a and 15b provided at both ends are fitted to the platen drum shaft 16 and the guide pin 17, respectively. This clamp member 15
Is normally driven by the spring 18 to the platen drum 13
When the color thermosensitive recording material 14 is clamped or unclamped, it is moved in a direction away from the platen drum 13 by the solenoid 19.

A thermal head 1 and an optical fixing device 21 are provided on the outer periphery of the platen drum 13. The optical fixing device 21 has a wavelength of about 365 nm as shown by the solid line in FIG.
And a rod-shaped ultraviolet lamp 24 having an emission peak at 420 nm and a cut filter 25 having a transmission characteristic shown by a dotted line. This cut filter 2
When it is put in front of the ultraviolet lamp 24 by a solenoid or the like, the element 5 transmits near ultraviolet rays in the vicinity of 420 nm. A transport roller pair 28 is disposed in the paper supply / discharge path 27, and the color thermosensitive recording material 14 is transported through the transport roller pair 28. Further, on the platen drum side of the paper supply / discharge path 27, a separation claw 29 is provided for guiding the rear end of the color thermosensitive recording material 14 to the paper supply / discharge path 27 during paper discharge.
In this embodiment, one passage is used as both the paper feed passage and the paper discharge passage, but they may be provided separately.

FIG. 5 shows an example of a color thermosensitive recording material. On the support 32, a cyan thermosensitive coloring layer 33,
A magenta thermosensitive coloring layer 34, a yellow thermosensitive coloring layer 35, and a protective layer 36 are sequentially formed. These thermosensitive coloring layers 33 to 35 are layered from the surface in the order of thermal recording. For example, in the case of thermal recording in the order of magenta, yellow, and cyan, the yellow thermosensitive coloring layer 35 and the magenta thermosensitive coloring layer 35 are used. The position of the coloring layer 34 is exchanged. An opaque coated paper or a plastic film is used as the support 32, and a transparent plastic film is used when an OHP sheet is prepared. The cyan thermosensitive coloring layer 33 contains an electron-donating dye precursor and an electron-accepting compound as main components, and develops cyan when heated. As the magenta thermosensitive coloring layer 34, a diazonium salt compound having a maximum absorption wavelength of about 365 nm,
It also contains a coupler that reacts with heat to develop a magenta color. When the magenta thermosensitive coloring layer 34 is irradiated with ultraviolet rays in the vicinity of 365 nm after thermal recording, the diazonium salt compound is photodegraded and the coloring ability is lost. The yellow thermosensitive coloring layer 35 contains a diazonium salt compound having a maximum absorption wavelength of about 420 nm, and a coupler that thermally reacts with this compound to develop yellow. When this yellow thermosensitive coloring layer 35 is irradiated with near-ultraviolet rays of 420 nm, it is photo-fixed and the coloring ability is lost.

FIG. 6 shows the coloring characteristics of the thermosensitive coloring layers 33 to 35. Color thermosensitive recording material 1 of this example
No. 4 has the lowest coloring heat energy of the yellow thermosensitive coloring layer 35 and the highest coloring heat energy of the cyan thermosensitive coloring layer 33. In the case of thermally recording the yellow Y pixel, the color thermal energy obtained by adding the gradation thermal energy GY _I to the bias thermal energy BY is applied to the color thermal recording material 14. The bias heat energy BY is heat energy immediately before the yellow heat-sensitive recording layer 35 develops color,
This is a constant value. Gradation expression heat energy GY
_I is determined according to the level I of the color density of the pixel to be recorded. Since magenta M and cyan C are the same, only reference numerals are given.

FIG. 7 shows an electric circuit of the color thermal printer. The image data input unit 40 is composed of a color scanner, a color TV camera, etc.
The image data of the three colors of blue are sent to the data processing unit 41. The data processing unit 41 performs color correction, gradation correction, etc. on the image data of each color. The image-processed image data of each color is sent to the frame memory 42 and stored in a state of being separated for each color. During thermal recording, the frame memory 42
From, the image data of the color to be printed is read line by line and written in the line memory 43. The image data for one line read from the line memory 43 is sent to the drive data generation unit 44 and converted into drive data for generating gradation expression thermal energy for each pixel. Further, the drive data generator 44 generates a bias signal determined according to the color to be thermally recorded. These drive data and bias signal are sent to the head drive unit 45. The head driving unit 45 drives the gradation expressing heat generating unit 4 and the bias heating heat generating unit 5. The controller 46 controls each part in sequence.

FIG. 8 shows an example of the head drive section. The drive data is composed of a pulse train of the number corresponding to the number of pixels and gradation steps. For example, in the case of 256 pixels and 64 gradations, the drive pulse train of one line is composed of 256 × 64 pulses. The drive data for one line is created as follows. First, the data indicating the first gradation is compared with the image data to determine whether or not to drive the pixel. If the pixel is driven, the value is set to "1", and if not driven, the value is set to "0". This comparison is performed for all pixels in one line, and the image data is converted into serial drive data. This serial drive data is sent to the shift register 50 by a clock signal and converted into a parallel signal. The drive data converted into the parallel signal by the shift register 50 is latched by the latch circuit 51 by the latch signal.
Latched on. The AND gate 52 outputs the signal of "H" when the latched signal is "1" when the strobe signal is input. Transistors 53a to 53n are connected to the respective output terminals of the AND gate 52, and the transistors are turned on when the output signal is "H". These transistors 53a to 53n
The gradation heating element 4 through the A electrodes 9a to 9n.
a to 4n are connected in series.

Next, the data indicating the second gradation and the image data of each pixel are compared and converted into drive data as described above. Each of the heating elements 4a ...
4n is selectively heated. In this way, in the case of 64 gradations, the drive data for one line is read in 64 times, and each heating element 4a is read by the strobe signal of 64 times.
4n are selectively driven, and an image of 64 gradations is expressed. The heating elements 4a to 4n are formed on one continuous resistor 8. For the transistor 55, B
Heat generating element 5 for bias heating via electrodes 10a to 10n
a to 5n are connected to each other, and the transistor 55
When is turned on, the heating elements 5a to 5n are energized to generate bias heat energy. By providing a transistor for each bias heating heating element, each bias heating heating element can be individually controlled.

FIG. 9 shows the waveform of the signal supplied to each section. Reference numeral A indicates a time during which a bias signal is supplied to the heating element for bias heating 5a to generate bias heat energy, and reference numeral B indicates that a strobe signal is supplied to the heating element for gradation expression 4a to perform gradation recording. Time, code C
Represents the cooling time of the heating element 4a for gradation expression,
Reference numeral A'denotes a warm-up time in which the strobe signal is supplied to the gradation expressing heating element 4a, but no actual recording is performed. Since the time A is performed during the time C, (1 line recording time) = (A ′ + B +
It can be seen that C) is shortened compared to the conventional (1 line recording time) = (A + B + C) shown in FIG. Further, the widths of the bias signal and the strobe signal are determined in consideration of the coloring heat energy of the color to be recorded.

Next, the operation of the above embodiment will be briefly described. At the time of thermal recording, the image data of each color input from the image data input unit 40 is subjected to image processing by the image processing unit 41 and then written in the frame memory 42 in a separated state for each color. At the time of sheet feeding, the platen drum 13 is stopped with the clamp member 15 being vertical in FIG. When the solenoid 19 is energized, the clamp member 15 is set to the clamp release position. The conveying roller pair 28 nips the color thermosensitive recording material 14 supplied from a cassette (not shown) to platen the drum 13
Transport it to. The conveying roller pair 28 is temporarily stopped when the front end of the color thermosensitive recording material 14 enters between the platen drum 13 and the clamp member 15.
Then, when the solenoid 19 is turned off, the clamp member 15 is returned by the spring 18 and clamps the front end of the color thermosensitive recording material 14. After this clamping, the platen drum 13 and the conveying roller pair 28 rotate, so that the color thermosensitive recording material 14 is wound around the platen drum 13.

Thermal recording is started when the platen drum 13 rotates intermittently at regular steps and the leading end of the recording area of the color thermosensitive recording material 14 reaches the thermal head 1.
In this thermal recording, the image data of the yellow image is read from the frame memory 42 for one line and is once written in the line memory 43. Next, the image data is read out from the line memory 43 and sent to the drive data generator 44. The drive data generator 44 generates a signal as shown in FIG. 9 and sends it to the head driver 45. The head drive unit 45 includes heating elements 5a to 5 for bias heating.
Bias heat energy BY is applied to the color thermosensitive recording material 14 by energizing n for a certain period of time. In addition, the head drive unit 4
Reference numeral 5 supplies the number of pulse currents corresponding to the image data to the gradation expressing heating elements 4a to 4n, and the color thermosensitive recording material 1 is provided.
The gradation expression thermal energy GY _I is applied to 4 to develop the color to a desired density. When the first line of the yellow image is recorded, the platen roller 10 rotates stepwise by one pixel, and at the same time, the second line of the yellow image is read from the frame memory 42.
The image data of the line is read. Thereafter, in the same manner, the second and subsequent lines of the yellow image are thermally recorded on the color thermosensitive recording material 14.

When the portion on which the yellow image is thermally recorded reaches the optical fixing device 21, the yellow thermosensitive coloring layer 35 is optically fixed here. This optical fixing device 21 is provided with a cut filter 25.
42 is set in front of the UV lamp 24,
The near-ultraviolet ray near 0 nm is applied to the color thermosensitive recording material 14. As a result, the diazonium salt compound contained in the yellow thermosensitive coloring layer 35 decomposes and the coloring ability disappears.

When the platen drum 13 makes one rotation and the recording area again reaches the position of the thermal head 1, magenta images are recorded on the magenta thermosensitive coloring layer 34 line by line. At the time of thermal printing of the magenta image, the bias heat energy BM is applied to the color thermosensitive recording material 14 by the bias heating heating elements 5a to 5n, and the gradation expression heating elements 4a to 4n cause gradations corresponding to the image data. Expressive heat energy GM _I is color thermal recording material 1
Given to 4. The coloring heat energy of this magenta image is larger than that of the yellow image,
Since the yellow thermosensitive coloring layer 35 has already been optically fixed,
The yellow thermosensitive coloring layer 35 does not develop color. The color thermosensitive recording material 14 on which the magenta image is recorded is optically fixed by the fixing device 21 as described above. In this case,
Since the cut filter 25 is retracted from the front of the ultraviolet lamp 24, all the electromagnetic waves emitted from the ultraviolet lamp 24 are applied to the color thermosensitive recording material 14. Of the electromagnetic waves, the magenta thermosensitive coloring layer 34 is optically fixed by the ultraviolet rays around 365 nm.

When the platen drum 13 makes one further rotation and the recording area again reaches the position of the thermal head 1, a cyan image is recorded on the cyan thermosensitive coloring layer 33 line by line. In this case, the bias heat energy BC is changed by the heat generating elements 5a to 5n for bias heating so that the color thermosensitive recording material 1 can be obtained.
Given 4 and gradation thermal energy GC _I is applied to the thermosensitive color recording paper 14 by the heating element 4a~4n gradation representation. The cyan thermosensitive coloring layer 33 has such a value that the coloring heat energy does not develop a color in a normal storage state, so that the cyan thermosensitive coloring layer 33 is not provided with optical fixing property. Therefore, in the thermal recording of the cyan thermosensitive coloring layer 33, the optical fixing device 21 is turned off.

After the thermal recording of the yellow image, the magenta image, and the cyan image is completed, the platen drum 13 and the conveying roller pair 28 are reversed. By the reverse rotation of the platen drum 13, the rear end of the color thermosensitive recording material 14 is separated by the separating claw 29.
The sheet is guided to the sheet feeding / discharging path 27 and nipped by the pair of conveying rollers 28. After that, when the platen drum 13 reaches the sheet feeding position, the solenoid 19 is energized and the platen drum 13 stops. Solenoid 19
The energization of # 2 causes the clamp member 15 to move against the spring 18, so that the clamping of the tip of the color thermosensitive recording material 14 is released. As a result, the thermally recorded color thermosensitive recording material 14 is discharged to the tray via the paper supply / discharge path 27.

In the embodiment shown in FIGS. 10 and 11, the ceramic substrate 62 of the thermal head 61 is made flat, and the gradation expressing heat generating portion 64 and the bias heating heat generating portion 65 are used.
The height of is changed. Then, the heat generating center portion 65a of the heat generating portion 65 for bias heating is brought close to the heat generating portion 64 for gradation expression, and the heat generating portions 64, 65 are properly brought into contact with the outer peripheral surface of the platen drum 13, as shown in FIG. It was done so. Each heating element 64a shown in FIG.
The structure of 65a is the same as that of the above embodiment.

In the embodiment shown in FIG. 12, a bias heating resistance element 70 and a gradation expression resistance element 71 are laminated in order to effectively perform the bias heating and improve the manufacturability. A bias heating resistance element 70 is provided in a flat plate shape, and a gradation expression resistance element 71 is provided on the bias heating resistance element 70 via a ceramic substrate 72. Reference numeral 73 is an adhesive layer, reference numerals 74 and 75 are bias heating electrodes, reference numeral 76,
Reference numeral 77 is a gradation expression electrode, reference numeral 78 is an insulating protective layer, and reference numeral 79 is a substrate.

In the embodiment described above, the bias heating is performed for a fixed time before the pixel recording, but the bias heating may be performed for a time corresponding to the maximum color density of one line. Further, the bias heating may be continuously performed during thermal recording.

The bias heating element can also correct unevenness in the resistance value of the heating element and uneven density and uneven gradation due to the common resistance. For example, if there are variations in the resistance values of the gradation expressing heating element and the bias heating heating element,
Due to this, density unevenness and gradation unevenness occur in the recorded image. Therefore, by calculating the correction amount for each pixel or for each gradation that is divided into a plurality, and applying this correction energy to the bias heating heat generating unit that is individually controlled for each heat generating element, It is possible to correct density unevenness and gradation unevenness without changing the driving conditions of the heat generating portion. Furthermore, by using this method, it is possible to improve the correction accuracy without reducing the printing speed.

Further, since the bias heating is performed by another heat generating portion, heat is less likely to be accumulated in the gradation expressing heat generating portion, so-called shading having different densities at the beginning and end of the recording pixel, and the adjacent heating element. It is possible to prevent deterioration of image quality due to so-called thermal history, which causes the density of the specific heat-generating element portion to be different even with the same gradation depending on the heat generation state and the heat generation history of the specific element.

The embodiment described above is applied to a thermal printer in which thermal recording is performed on a thermosensitive coloring layer of a thermosensitive recording material, and then the image is fixed by light.
For example, the present invention can of course be applied to a thermal transfer printer that records an image on a recording paper via an ink film. In this case, the thermal response speed is improved, the ink transfer efficiency of the ink film is improved, and the unevenness correction accuracy is improved, so that the image quality is improved. Further, the above embodiment is an example in which the thermal head or the recording paper is applied to the line printer for relative movement in the sub-scanning direction for recording, but the present invention is applied to the serial printer for two-dimensional relative movement for recording. Can also be applied.

[0031]

As described above in detail, in the invention described in claim 1, the gradation expression heating portion and the auxiliary heating portion are provided, and the gradation expression heating and the bias heating are performed separately. Since these heat generating parts are properly contacted with the outer peripheral surface of the platen drum, thermal recording can be performed efficiently in a short time as compared with the case of using a conventional thermal head, and the thermal energy can be increased. Can be prevented and unevenness of recorded images can be prevented. According to the second aspect of the invention, since the gradation expression and the auxiliary heating are laminated, the heating can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a thermal head of the present invention.

FIG. 2 is an explanatory diagram showing a contact state between a thermal head shown in FIG. 1 and an outer peripheral surface of a platen drum.

FIG. 3 is a schematic view of a color thermal printer using a thermal head.

FIG. 4 is a graph showing characteristics of an ultraviolet lamp and a cut filter of the optical fixing device.

FIG. 5 is an explanatory diagram showing a layer structure of a color thermosensitive recording material.

FIG. 6 is a graph showing coloring characteristics of each thermosensitive coloring layer.

FIG. 7 is a block diagram showing an electrical configuration of a color thermal printer.

FIG. 8 is a circuit diagram showing a head driving unit and a heat generating unit.

FIG. 9 is a waveform diagram of each signal supplied to the head drive unit.

FIG. 10 is a sectional view showing another embodiment of the thermal head.

FIG. 11 is an explanatory diagram showing a contact state between the thermal head shown in FIG. 10 and the outer peripheral surface of the platen drum.

FIG. 12 is a cross-sectional view showing a thermal head in which resistive elements for gradation expression and bias heating are laminated.

FIG. 13 is an explanatory diagram showing a heat generation state of a conventional thermal head.

[Explanation of symbols]

 1,61 Thermal head 3,62,72,79 Ceramic substrate 4,64 Heat generating part for gradation expression 5,65 Bias heating heat generating part 8 Resistor 9 A electrode 10 B electrode 11 Common electrode 13 Platen drum 14 Color thermal recording Material 21 Optical fixing device 70 Heating element for bias heating 71 Heating element for gradation expression

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/38 B41J 3/20 115 D 116

Claims (2)

[Claims] 1. A heat generating section for gradation expression and two heat generating sections for auxiliary heating are provided, and at least one heat generating section is tilted so that these heat generating sections properly contact the outer peripheral surface of the platen drum. The thermal head. 2. A heat generating part for gradation expression and an auxiliary heating are laminated with a planar insulating layer interposed therebetween, and the heating part for auxiliary heating is formed into a flat plate shape parallel to the insulating layer. Thermal head.