JP2818705B2 - Color thermal recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color heat-sensitive recording method, and more particularly to a color heat-sensitive recording method improved so that two types of heat-sensitive coloring layers do not simultaneously form a color.

[0002]

2. Description of the Related Art A color thermosensitive recording material capable of directly recording a multicolor image with a thermal head has been conventionally known (for example, JP-A-61-213169). Further, as shown in FIG. 9, the present applicant has proposed a color thermosensitive recording material in which a cyan thermosensitive coloring layer 3, a magenta thermosensitive coloring layer 4, a yellow thermosensitive coloring layer 5, and a protective layer 6 are sequentially provided on a support 2. 7 (Japanese Patent Application No. 2-89384). In the color thermosensitive recording material 7, as shown in FIG. 10, the yellow thermosensitive coloring layer 5, which is the uppermost layer, has the highest thermal recording sensitivity.
The lowermost layer, the cyan thermosensitive coloring layer 3, has the lowest thermal recording sensitivity.

The cyan thermosensitive coloring layer 3 contains an electron-donating dye precursor and an electron-accepting compound as main components and develops cyan when heated. The magenta thermosensitive coloring layer 4 contains a diazonium salt compound having a maximum absorption wavelength of λ1, and a coupler which reacts with the diazonium salt compound to develop magenta. When the magenta thermosensitive coloring layer 4 is irradiated with ultraviolet light of λ1 after thermal recording, the diazonium salt compound is photolyzed and loses its coloring ability. Yellow thermosensitive coloring layer 5
Contains a diazonium salt compound having a maximum absorption wavelength of λ2 and a coupler which thermally reacts with the diazonium salt compound to form yellow. When the yellow thermosensitive coloring layer 5 is irradiated with near-ultraviolet rays of λ2, the yellow thermosensitive coloring layer 5 is light-fixed and loses its coloring ability.

When a multicolor image is thermally recorded on the color thermosensitive recording material 7, a thermal head is used in which a plurality of heating elements are arranged in a line and a constant voltage is applied to each heating element. First, while the thermal head and the color thermosensitive recording material 7 are relatively moved, the first thermosensitive coloring layer 5, which is the first layer, is thermally recorded by the thermal head. After the thermal recording of the yellow image, the yellow image is optically fixed by irradiating light in a wavelength range that photodecomposes only the uncolored diazonium salt compound of the yellow thermosensitive coloring layer. Next, a higher thermal energy is applied to the magenta thermosensitive coloring layer 4 as the second layer than the yellow thermosensitive coloring layer 5 to thermally record the magenta thermosensitive coloring layer 4, and then the uncolored diazonium of the magenta thermosensitive coloring layer is recorded. The magenta image is light-fixed by irradiating light in a wavelength range that photolyzes only the salt compound. Finally, using the largest thermal energy, the cyan thermosensitive coloring layer 3, which is the third layer, is thermally recorded.

[0005]

As can be seen from the characteristic curve of FIG. 10, in the coloring heat energy region EA, the high density region of the yellow thermosensitive coloring layer 5 and the low density region of the magenta thermosensitive coloring layer 4 are different. Duplicate. For this reason, when a high-density yellow image is recorded, the magenta thermosensitive coloring layer 4 also develops color at the same time with excess thermal energy, and the original color tone cannot be reproduced. In the area EB,
Since the high density area of the magenta thermosensitive coloring layer 4 and the low density area of the cyan thermosensitive coloring layer 3 overlap, the same problem also occurs. Therefore, conventionally, a yellow thermosensitive coloring layer 5 and
The thermal recording of the magenta thermosensitive coloring layer 4 uses heat energy within a range where the thermosensitive coloring layer immediately below each thermosensitive coloring layer does not develop color.

The present invention provides a color thermosensitive recording method in which, even when an upper thermosensitive coloring layer is colored at a high density, another lower thermosensitive coloring layer is prevented from being simultaneously colored by excess heat energy. It is intended to do so.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, when thermal recording is performed on an upper thermosensitive coloring layer, which overlaps with a lower coloring heat energy, the desired thermal coloring layer is formed. At a temperature higher than the color temperature range required to obtain the density of
The color is developed in a shorter time than the heating time required for producing the color. In the invention described in claim 2, the thermosensitive coloring layer of the upper layer to overlap the lower layer of coloring heat energy is generated upon the thermal recording than the thermal recording of the underlying heat-sensitive coloring layer, the voltage applied to the thermal head It is intended to be higher. According to the third aspect of the present invention, there is provided a color thermosensitive recording material having at least three types of thermosensitive coloring layers including a yellow thermosensitive coloring layer as an uppermost layer, a magenta thermosensitive coloring layer as an intermediate layer, and a cyan thermosensitive coloring layer as a lowermost layer. At the time of recording, the relationship of the number of gradations is set to magenta ≧ cyan> yellow, and the color heat energy of the lower layer is overlapped with that of the upper layer.
When performing thermal recording on the thermosensitive coloring layer, it is necessary to obtain the desired density.
A temperature higher than the required color temperature range and the color temperature
During heating required to achieve the desired concentration in the temperature range
The color is developed in a shorter time than in the interval .

[0008]

In FIG. 2, a platen drum 10 holds a color thermosensitive recording material 7 on its outer periphery, and is rotated in the direction of the arrow by a pulse motor 12 during thermal recording. A clamp member 13 is attached to the platen drum 10, and at least one position, for example, the tip of the color thermosensitive recording material 7 is fixed to the platen drum 10. Clamp member 13
Are U-shaped, and have long holes 13a, 13a provided at both ends.
b is fitted to the platen drum shaft 15 and the guide pin 16, respectively. The clamp member 13 is normally pressed against the platen drum 10 by a spring 17, and when the color thermosensitive recording material 7 is attached or detached, a solenoid 18 is attached.
Is moved in a direction away from the platen drum 10.

On the outer periphery of the platen drum 10, a thermal head 20 having a large number of heating elements arranged in a line is provided.
And an optical fixing device 21. Optical fixing device 21
Is approximately 365 nm and 420 nm, as shown by the solid line in FIG.
a rod-shaped ultraviolet lamp 22 having an emission peak in nm,
Cut filter 23 having transmission characteristics as indicated by the dotted line
It is composed of This cut filter 23 transmits near-ultraviolet rays of about 420 nm when inserted in front of the ultraviolet lamp 22 by a solenoid or the like. A transport roller pair 25 is disposed in the paper supply / discharge path 24, and the color thermal recording material 7 is transported through the transport roller pair 25.
A separation claw 26 for guiding the rear end of the color thermosensitive recording material 7 to the paper supply / discharge passage 24 at the time of paper discharge is provided on the platen drum side of the paper supply / discharge passage 24. In this embodiment, one passage is used for both the paper supply passage and the paper discharge passage, but these may be provided separately.

FIG. 4 shows an electric circuit of the color thermal printer. The image data input unit 40 includes a color scanner, a color TV camera, and the like.
The image data of three blue colors is sent to the data processing unit 41. The data processing unit 41 performs color correction, gradation correction, and the like on image data of each color. The image data of each color subjected to the image processing is sent to the frame memory 42 and stored in a state of being separated for each color. At the time of thermal recording, the frame memory 42
Thus, the image data of the color to be printed is read line by line and written into the line memory 43.

The image data for one line read from the line memory 43 is sent to a drive data generator 44 and converted into drive data for each pixel. The drive data includes bias drive data for generating bias heat energy and gradation drive data for generating gradation expression heat energy. The driving data for one line is sent to the head driving unit 45 and is converted into a bias pulse for each pixel and a number of gradation pulses corresponding to the gradation level. 46n. These heating elements 46a to 46n are arranged in a line in the main scanning direction.
Relative to the sub-scanning direction. Controller 47
Controls the rotation of the pulse motor 12 via a driver 48 in addition to the sequence control of each unit.

FIG. 5 shows an example of the head driving section 45. One line of 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. When the strobe signal is input and the latched signal is “H”, the AND gate 52 outputs an “H” signal. This AND
Each output terminal of the gate 52 includes transistors 53a-5
3n are connected, and when the output terminal of the AND gate 52 is “H”, the corresponding transistor 53a
To 53n are turned ON. These transistors 53a-5
3n is connected to the voltage control circuit 54 via the heating elements 46a to 46n. This voltage control circuit 54 can change the applied voltage by a switching signal.

The driving data for one line is generated as follows. First, in order to perform bias heating, “H” drive data is given to all pixels for one line, and serial drive data is obtained. When the drive data is “H”, the corresponding heating element generates heat. Next, the data indicating the first gradation is compared with the image data, and it is determined whether or not to drive the pixel. If the pixel is driven, "H" is set, and if not, "L" is set. This comparison is performed for all pixels on one line, and the image data is converted into serial drive data. The heating elements 46a to 46n are selectively driven by the serial drive data.
Similarly, the data indicating the second gradation is compared with the image data of each pixel, and converted into drive data as described above. For example, in the case of 64 gradations, one line of drive data including bias heating is read out in 65 times, and each heating element 46a is read by 65 strobe signals.
To 46n are selectively driven to express a 64-gradation image.

FIG. 1 shows the signal waveform of each part. T1 is a time required for thermal recording of one pixel, and is set shorter as thermal recording sensitivity is higher. T2 is the width of the bias pulse for performing the bias heating, and is set narrower as the thermal recording sensitivity increases. T3 is the ON period of the gradation pulse, and is set narrower as the thermal recording sensitivity becomes higher. These pulse widths T2 and T3 are determined by the strobe signal. T4 is the OFF period of the gradation pulse, which is the same for each thermosensitive coloring layer. T5 is a cooling time, which depends on the gradation level, and may be shorter for a thermosensitive coloring layer having a higher thermal recording sensitivity.

Next, the operation of the above-described color thermal printer will be briefly described. The image data of each color input from the image data input unit 40 is image-processed by the image processing unit 41 and then written into the frame memory 42 in a state where the image data is separated for each color. When feeding paper, the platen drum 10
Is stopped in a state where the clamp member 13 is vertical in FIG. When the solenoid 18 is energized, the clamp member 13 is set to the clamp release position. The transport roller pair 25 nips the color thermosensitive recording material 7 supplied from a cassette (not shown) and
Conveyed toward. The transport roller pair 25 stops once when the leading end of the color thermosensitive recording material 7 enters between the platen drum 10 and the clamp member 13. Thereafter, when the solenoid 18 is turned off, the clamp member 1 is turned off.
3 is returned by the spring 17 and clamps the front end of the color thermal recording material 7. After this clamping, the platen drum 10 and the transport roller pair 25 rotate, so that the color thermosensitive recording material 7 is wound around the outer periphery of the platen drum 10.

When the platen drum 10 rotates intermittently at regular steps and the leading end of the recording area of the color thermosensitive recording material 7 reaches the thermal head 20, thermal recording of a yellow image is started. The image data of the yellow image for one line is read out from the frame memory 42 and written into the line memory 43 once. Next, image data is read 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. The head drive unit 45 drives each of the heat generating elements 46a to 46n to give a bias pulse and a number of gradation pulses corresponding to image data to the heat generating elements 46a to 46a to generate heat. These heating elements 46a to 46a heat the color thermosensitive recording material 7 to cause each pixel to develop a desired density. When the first line of the yellow image is recorded, the platen roller 10 is stepwise rotated by one pixel by the pulse motor 12, and at the same time, the image data of the second line of the yellow image is read from the frame memory 42. Hereinafter, similarly, the second and subsequent lines of the yellow image are thermally recorded on the color thermosensitive recording material 7.

When the portion where the yellow image is thermally recorded reaches the optical fixing device 21, the yellow thermosensitive coloring layer 5 is optically fixed here. Since the cut filter 23 is set in front of the ultraviolet lamp 22,
The near-ultraviolet ray near m is irradiated on the color thermosensitive recording material 7. As a result, the azonium salt compound remaining in the yellow thermosensitive coloring layer 5 undergoes photolysis and loses its coloring ability.

When the platen drum 10 makes one rotation and the recording area comes to the position of the thermal head 20 again, the thermal head 20 applies heat energy corresponding to the color density to the color thermosensitive recording material 7 to print a magenta image line by line. Record heat. The coloring heat energy of the magenta image is larger than the coloring heat energy of the yellow image. However, since the yellow heat-sensitive coloring layer 5 has already been optically fixed, the yellow heat-sensitive coloring layer 5 does not emit any color. The color thermosensitive recording material 7 on which the magenta image has been recorded is optically fixed by the fixing device 21 as described above. In this case, since the cut filter 23 is retracted from the front of the ultraviolet lamp 22, all the electromagnetic radiation emitted from the ultraviolet lamp 22 is irradiated to the color thermosensitive recording material 7. Of this electromagnetic radiation, 365
The magenta heat-sensitive coloring layer 4 is optically fixed by ultraviolet light having a wavelength of about nm.

When the platen drum 10 makes one more rotation and the recording area reaches the position of the thermal head 20 again, thermal recording of the cyan image is started. The thermal head 20
The thermal energy according to the color density is transferred to the color thermosensitive recording material 7
, And the cyan image is formed one line at a time.
Heat recording. In the thermal recording of the cyan thermosensitive coloring layer 3,
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 10 and the conveying roller pair 25 rotate in reverse. Due to the reverse rotation of the platen drum 10, the rear end of the color thermosensitive recording material 7 is guided to the paper supply / discharge passage 24 by the separation claw 26, and is nipped by the transport roller pair 25. Thereafter, when the platen drum 10 reaches the sheet feeding position, the solenoid 18 is energized and the platen drum 10 stops. The energization of the solenoid 18 causes the clamp member 13 to move against the spring 17, so that the clamp at the tip of the color thermosensitive recording material 7 is released. As a result, the heat-recorded color thermosensitive recording material 7 is discharged to the tray via the paper supply / discharge path 24.

Experiments were performed on the thermal printer under different printing conditions. As the thermal head, a thermal head having a dot density in the main scanning direction of 9.45 dots / mm, an element density of 45.55 / mm ² , and a resistance value of 2710Ω was used. The thermal energy E (mJ / mm
² ) was obtained from the following equation. ^{E = V 2 × (G +} K × N) × S / R wherein each symbol is as follows. V: applied voltage (V) G: bias pulse (second) K: gradation pulse (second) N: gradation level S: number of heating elements per 1 mm ² R: resistance value (Ω)

Table 1 below shows the printing conditions A (64 gradations), Table 2 shows the printing conditions B (128 gradations), and Table 3 shows the printing conditions C (256 gradations).

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

Under the printing conditions A to C, only the yellow thermosensitive coloring layer 5 was thermally recorded and then fixed by light to produce a test print. When the yellow density of this test print and the magenta density that simultaneously develops color with excess thermal energy during thermal recording of yellow were measured, the characteristic curve shown in FIG. 6 was obtained. In addition, the coloring heat energy (mJ /
When the relationship between mm ² ) and the yellow density was examined, FIG.
Was obtained. FIG. 8 shows the energization time (G + K
× N) and the yellow density.

It can be seen from FIG. 6 that the printing condition A has a lower density of the magenta simultaneous coloring (color mixture) than the printing conditions B and C. This printing condition A is
The ON time T3 while the OFF time T4 of the gradation pulse is constant.
Is made longer (the duty ratio is larger),
By increasing the ON time T3, simultaneous magenta coloring can be suppressed. When the ON time T3 is lengthened, as shown in FIG. 7, the cooling of the thermal head (exactly, the heating element) is small, and the head temperature can be maintained at a high temperature. Therefore, the yellow thermosensitive coloring layer 5 is heated at a temperature sufficiently higher than the yellow coloring starting temperature,
The required concentration will be reached in a short time. FIG. 8 shows that thermal recording is performed in this short time.

As described above, if thermal recording is performed in a short time, thermal recording of a yellow image is completed before excessive thermal energy is applied to the lower magenta thermosensitive coloring layer 4, so that simultaneous magenta coloring is performed. Can be suppressed. This simultaneous coloring also occurs between the second magenta thermosensitive coloring layer 4 and the third cyan thermosensitive coloring layer 3. Therefore, also in the thermal recording of the magenta thermosensitive coloring layer 4, it is preferable to perform the thermal recording at a high temperature for a short time as in the thermal recording of the yellow thermosensitive coloring layer 5.

However, since the OFF time T4 of the gradation pulse requires a certain amount of time, the number of gradations is sacrificed when performing thermal recording for a short time, and 64 gradations are practically used as in the experimental example. Is the limit. Therefore, although the short-time recording can solve the problem of simultaneous color development, another problem occurs in that a high-tone multicolor image such as a photograph cannot be printed.

By the way, the human eye has an equivalent number of gradations depending on the color. For example, if magenta has 64 gradations, the equivalent number of gradations is 36 gradations for yellow and 54 gradations for cyan. Therefore, when magenta and cyan have 128 tones, yellow has 64 tones or a slightly higher number of tones, so that simultaneous magenta color development can be achieved while maintaining high tonal expression of the entire image. And color reproducibility can be improved. In this case, the printing condition A, which is a short-time thermal recording, is used for the thermal recording of the yellow image, and the printing condition B is used for the thermal recording of the magenta image and the cyan image. Of course, cyan may be slightly smaller than 128 gradations.

In order to prevent simultaneous color development, thermal recording at a high temperature for a short time is effective. In addition to changing the duty ratio of the gradation pulse, changing the output voltage of the voltage control circuit 54 in FIG. It can be carried out. In this case, the voltage is set to 22 V at the time of recording a yellow image, and to 20 V at the time of thermal recording of a magenta image and a cyan image. Of course, simultaneous coloring occurs between magenta and cyan, so the voltage may be changed between these. Further, the duty ratio of the gradation pulse may be changed together with the change of the applied voltage.

In the above-described color thermosensitive recording material, a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially formed on a support, but the order can be arbitrarily changed. Also in this case, the printing conditions are changed between the first layer and the second layer, and further between the second layer and the third layer. Further, since the coloring of the cyan thermosensitive coloring layer, which is the lowermost layer, requires heat energy that cannot occur in a normal storage state, light fixing property is not given to this. Light fixing properties may be imparted to the heat-sensitive coloring layer.

Further, a line printer in which a large number of heating elements are arranged in the main scanning direction and the color thermosensitive recording material is moved in the sub-scanning direction to perform thermal recording has been described. It can also be used for serial printers that perform thermal recording by moving relative to two dimensions.

[0034]

As described above in detail, according to the present invention, in the thermal recording of the underlying thermosensitive coloring layer and the thermosensitive coloring layer having overlapping coloring thermal energy, the applied voltage and the gradation pulse by changing the printing conditions such as the duty ratio, 且 at a temperature higher than the color gamut required to produce the desired concentration
It is necessary to obtain a desired density in the color temperature range.
Color was developed in less time than the heating time
In the past, it was not possible to develop color by mixing colors.
The high density part of the layer can be recorded. did
Therefore, the suppressing color mixture by the simultaneous coloration even when increasing the coloring density, color reproducibility can be improved. Further, by decreasing the number of gradations for yellow and increasing the number of gradations for magenta and cyan, a multicolor image with less simultaneous coloring and high gradation can be thermally recorded.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing each signal of a head drive unit and a heating state of a heating element.

FIG. 2 is a schematic diagram of a color thermal printer embodying the present invention.

FIG. 3 is a graph showing characteristics of an ultraviolet lamp and a cut filter of the optical fixing device.

FIG. 4 is a block diagram illustrating an electrical configuration of the color thermal printer.

FIG. 5 is a circuit diagram showing a head driving unit and a heating unit.

FIG. 6 is a graph showing the relationship between the yellow density developed in thermal recording of yellow and the magenta density developed simultaneously.

FIG. 7 is a graph showing a relationship between heat energy and yellow density.

FIG. 8 is a graph showing a relationship between an energizing time and a yellow density.

FIG. 9 is an explanatory diagram illustrating an example of a layer structure of a color thermosensitive recording material.

FIG. 10 is a graph showing the coloring characteristics of each thermosensitive coloring layer.

[Explanation of symbols]

 7 Color Thermosensitive Recording Material 20 Thermal Head 21 Optical Fixer 46 Heating Section 46a-46n Heating Element

Claims (3)

(57) [Claims] 1. A thermosensitive coloring layer comprising at least first to third thermosensitive coloring layers having different colors to be formed, wherein the lower layer has a lower thermal recording sensitivity, a higher density region of the upper thermosensitive coloring layer and a lower density of the lower thermosensitive coloring layer. Using a color thermosensitive recording material in which the coloring thermal energy partially overlaps with the density region, the top layer is moved while the thermal head in which a plurality of heating elements are arranged in a line and the color thermosensitive recording material are relatively moved. In the color thermal recording method of recording a multi-color image on a color thermal recording material by performing thermal recording and optical fixing in order from the first, the thermal recording layer of the upper layer where the thermal energy of the lower layer overlaps with the thermal energy of the lower layer is thermally recorded. In this case, the temperature is higher than the color temperature range required to obtain a desired density and the color temperature range
The heating time required to achieve the desired concentration at
Color thermal recording method is characterized in that so as to develop color in a short time remote. 2. The method according to claim 1, wherein when applying heat recording to the upper thermosensitive coloring layer overlapping with the lower coloring heat energy, the applied voltage of the thermal head is set higher than that of the lower thermosensitive coloring layer. 2. A color thermosensitive recording method according to claim 1, wherein: 3. A thermosensitive recording layer comprising at least a yellow thermosensitive coloring layer, a magenta thermosensitive coloring layer and a cyan thermosensitive coloring layer , wherein the yellow thermosensitive coloring layer as the uppermost layer has the highest thermal recording sensitivity and the cyan thermosensitive coloring layer as the lowermost layer. Using a color thermosensitive recording material that has the lowest sensitivity, and the color heat energy of the high density area of the yellow thermosensitive coloring layer and the low density area of the magenta thermosensitive coloring layer partially overlaps, multiple heating elements are lined Color thermal recording, in which a thermal head and a color thermosensitive recording material are arranged relatively to each other, and thermal recording and optical fixing are performed in order from the yellow thermosensitive coloring layer to record a multicolor image on the color thermosensitive recording material. In the method, the relationship between the number of gradations is set such that magenta ≧ cyan> yellow, and the heat sensitivity of the upper layer in which the coloring heat energy of the lower layer overlaps
It is necessary to obtain the desired density when thermally recording the coloring layer.
A temperature higher than the color temperature range to be performed and the color temperature range
The heating time required to achieve the desired concentration at
A color thermosensitive recording method characterized in that the color is developed in a short time .