JPH1058720A - Method and device for thermally transferring recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for thermally transferring recording capable of executing high quality intermediate gradation recording by utilizing a light emission device array wherein a plurality of light emission devices are juxtaposed in a main scanning direction. SOLUTION: A plurality of light emission devices each of which has a length in a sub-scanning direction is longer than a recording pixel are juxtaposed in a main scanning direction. The emission light generated by applying a voltage pulse to each of the light emission devices 1a is passed through an optical lens 2 capable of collecting the light in the sub-scanning direction to be made the collected light of which length in the sub-scanning direction is shorter than the recording pixel and to be emitted on an ink donor film 10. A voltage is repeatedly applied to the light emission device 1a so that the collected light is repeatedly emitted on a region to be melted on the ink donor film 10 in accordance with density data of each pixel and the ink donor film 10 is conveyed. The ink donor film 10 is intermittently conveyed by an interval shorter than the length of the recording pixel in the sub-scanning direction. An area of a dot in the recording pixel is varied to represent the intermediate gradation density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a light emitting element array in which a plurality of light emitting elements are arranged side by side in the main scanning direction, and radiates light emitted from each light emitting element onto an ink donor film to perform halftone recording. The present invention relates to a thermal transfer recording method and a thermal transfer recording device.

[0002]

2. Description of the Related Art Conventionally, as a halftone recording system using thermal transfer recording, there are a sublimation type thermal transfer recording using a thermal head and a fusion type thermal transfer recording. The sublimation type thermal transfer recording has a problem that it takes a long time to print because large energy needs to be applied to the heat generating element of the thermal head, and the cost is high because special paper is used.

[0003] On the other hand, fusion type thermal transfer recording can be printed with small energy and is inexpensive, but the transfer of ink on an ink donor film cannot reproduce gradation even if the energy applied to the heating element is changed. Key recording is difficult, matrix method such as dither method, sub-scanning division method,
A method of reproducing multiple gradations by reducing the heat generation region, such as a heat concentration method, has been proposed. For example, the sub-scanning division method uses a thermal head in which a plurality of heating elements whose length in the sub-scanning direction is shorter than the length in the main scanning direction, and controls the energization time to the corresponding heating element according to the density of each recording pixel. In addition, halftones are reproduced by intermittently conveying an ink donor film and recording paper at intervals shorter than the length of recording pixels in the sub-scanning direction (Japanese Patent Application Laid-Open Nos. 60-248074 and 3-219969). Gazette).

However, when the heating element is miniaturized in the sub-scanning direction in order to obtain good gradation characteristics in the above-described sub-scanning division method, the influence of resistance value variation increases, and a problem arises particularly in the reproducibility of a highlight portion. . In addition, there is a limit to miniaturization of the heating element from the viewpoint of manufacturing reliability.

[0005] Instead of the method of changing the area of the heat generating area by miniaturizing the thermal head, an apparatus has been proposed in which the heat generating area is miniaturized by irradiating a laser beam onto the ink donor film. , Enlargement of equipment by optical system,
There are problems such as a reduction in printing speed due to light source scanning in the main scanning direction (see JP-A-59-143657).

In the electrophotographic method, as a method of miniaturizing a heat generating area on a photoreceptor, light generated in an LED array including a plurality of light emitting diodes (hereinafter, referred to as LEDs) passes through a lens. By condensing light in the sub-scanning direction and irradiating it to the photoconductor, the length of the heating area in the sub-scanning direction is made smaller than that of the recording pixels, and the irradiation time of the LED is controlled according to the density of each recording pixel to reduce the printing area. There has been proposed an electrophotographic recording apparatus that expresses a halftone by changing the tone (see JP-A-1-217476).

[0007]

However, in the thermal transfer recording, since the solidified heat-fusible ink is melted and transferred to the recording paper, much larger energy is required as compared with the case where the photoreceptor is melted. And For this reason, the emission energy of each LED of the electrophotographic recording apparatus is about two to three orders of magnitude of the energy required for melting the hot-melt ink in thermal transfer recording (about 10 mW in the case of halftone recording). small. Therefore, there has been a problem that the method of expressing halftone by irradiating the photoconductor with light emitted from the LED array in the above electrophotographic recording apparatus cannot be immediately applied to thermal transfer recording.

In view of the above circumstances, the present invention uses a light emitting element array in which a plurality of light emitting elements are arranged side by side in the main scanning direction, and the emitted light of each light emitting element can melt the hot-melt ink applied on the ink donor film. It is an object of the present invention to provide a thermal transfer recording method and a thermal transfer recording apparatus capable of performing high-quality halftone recording while irradiating so as to achieve the above.

[0009]

According to a first aspect of the present invention, there is provided a thermal transfer recording method, wherein a plurality of light emitting elements each having a length in the sub-scanning direction longer than a recording pixel are arranged in the main scanning direction. An ink donor coated with hot-melt ink as condensed light having a length in the sub-scanning direction shorter than a recording pixel by passing light emitted by applying a voltage pulse through an optical lens capable of condensing in the sub-scanning direction. A voltage is repeatedly applied to the light emitting element so that the condensed light is repeatedly irradiated to a region to be melted according to the density data of each pixel on the ink donor film. The ink donor film is transported together, and the transport of the ink donor film is intermittent transport in units of an interval shorter than the length of the recording pixel in the sub-scanning direction, and each pixel is transported intermittently. Dode - is characterized in that the heat-meltable ink which is melted in accordance with the data is transferred to the recording sheet, by changing the area of the dots in each recording pixel performs halftone recording.

According to a second aspect of the present invention, there is provided a thermal transfer recording apparatus including the following components. A light emitting element array in which a plurality of light emitting elements each having a length in the sub-scanning direction longer than a recording pixel are arranged in parallel in the main scanning direction. Driving means for controlling the number of times of light emission of each light emitting element by applying a voltage pulse of a number corresponding to the density data of the corresponding pixel to each light emitting element. Arranged on the light emitting surface side of each light emitting element, condenses the emitted light in the sub-scanning direction, and has a sub-scanning direction length on an ink donor film coated with a heat-meltable ink disposed on the anti-light emitting element side. An optical lens that irradiates as condensed light shorter than the recording pixels. The ink donor film is intermittently transported in units of intervals shorter than the length of the recording pixels in the sub-scanning direction, and the region to be melted according to the density data of each pixel on the ink donor film is described above. Conveying means for conveying the condensed light repeatedly. Then, the heat-meltable ink melted in accordance with the density data of each pixel is transferred to the recording paper, and halftone recording is performed by changing the area of the dot in each recording pixel.

According to a third aspect of the present invention, in the thermal transfer recording apparatus according to the second aspect, the optical lens has a semicircular cross section in the sub-scanning direction with the light emitting element side as a base. And

According to a fourth aspect of the present invention, in the thermal transfer recording apparatus according to the second or third aspect, each of the light emitting elements comprises a light emitting diode.

According to a fifth aspect of the present invention, there is provided a thermal transfer recording apparatus according to the second or third aspect, wherein each of the light emitting elements comprises a laser diode.

According to the thermal transfer recording method and the thermal transfer recording apparatus, light emitted from a light emitting element having a larger area than the recording pixel is condensed so that the length in the sub-scanning direction is shorter than that of the recording pixel, and the energy density is reduced. Since the raised condensed light is irradiated onto the ink donor film, a heat generation region having a high energy density and a small area can be formed on the ink ink donor film. Then, the number of voltage pulses and the conveyance of the ink donor film are controlled, and the area to be melted on the ink donor film is repeatedly irradiated with the condensed light, so that the energy density of the condensed light irradiation part is further increased, The hot-melt ink can be reliably melted and transferred to recording paper. Further, since the ink donor film is intermittently transported in units of intervals shorter than the length of the recording pixels in the sub-scanning direction to move the condensed light irradiation area having a small area, the recording pixels are adjusted according to the density data of each pixel. Halftone printing can be performed by changing the area of the middle dot stepwise.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal transfer recording method according to the present invention will be described below with reference to FIGS. FIG.
FIG. 4 is a sectional view in the sub-scanning direction showing a state in which light emitted from a light emitting element is irradiated onto an ink donor film. The light emitting surface of the light emitting element 1a is an ink donor film 10.
The optical lens 2 having a semicircular cross section in the sub-scanning direction with the light emitting element 1a side as the base is disposed between them.

A plurality of light emitting elements 1a are arranged side by side in the main scanning direction (the direction of the front and back of the paper) to form a light emitting element array 1, and the optical lens 2 has a rod-like shape extending in the main scanning direction. It is arranged so as to cover the light emitting element 1a. Each light emitting element 1a is connected to a driving unit (not shown), and emits light when a voltage pulse corresponding to the density data of the corresponding pixel is applied from the driving unit. Here, the light emitting element 1a is described as an LED.

In the lower part of the figure, an LED 1a is connected to an ink donor.
The top view seen from the film 10 side is shown. In the upper part of the figure, there is an ink donor film 10 viewed from the LED 1a side.
The upper corresponding recording pixel area is shown. The LED 1a has a length Lb in the sub-scanning direction longer than the length Ld of the recording pixel in the sub-scanning direction,
The length La in the main scanning direction is the same as the length Lc of the recording pixel in the main scanning direction. That is, the length Ld of the recording pixel in the sub-scanning direction is 16
9.3 μm (equivalent to 150 DPI), whereas L
The length Lb of the ED element 1a in the sub-scanning direction is almost quadrupled to 680 μm.
m, the energy of the emitted light is increased by making the emission area approximately four times the recording pixel area.

The optical lens 2 has an optical characteristic in the sub-scanning direction that focuses 680 μm emitted light from the LED 1 a to about 14 μm (1/12 of Ld, n in the figure) during a distance L. It was used. Since the optical lens 2 does not change in the main scanning direction, the length of the recording pixel area shown in the upper part of the drawing in the sub-scanning direction is converged to 1/12 of the recording pixel, and the area becomes 1/12 of the recording pixel. Illuminated by the collected light.

The LED surface side of the ink donor film 10 is made black so as to generate heat by light absorption (not shown). When the energy density by the irradiation of the condensed light reaches a certain level or more, an ink donor film is formed. The hot-melt ink applied on 10 is melted and transferred to recording paper 11,
A dot having an area of 1/12 of the recording pixel is recorded.

The energy density of the condensed light on the ink donor film 10 is equal to the LE of the same area as the recording pixel.
D emits light and emits light four times as much as 1/12 of the energy density (hereinafter referred to as reference energy density) when the ink is irradiated onto the ink donor film without focusing.
Since the light is condensed, the height is increased to 4 × 12 times = 48 times. Actually, there is a loss in the optical system, but the energy density can be increased by one digit or more even in consideration of the loss.

Next, a method of irradiating the light emitted from the LED 1a to the ink donor film 10 through the optical lens 2 and conveying the ink donor film 10 and the recording paper 11 to perform halftone recording will be described. FIG. 1 illustrates an example in which the light emitted from the LED 1a is condensed so that the sub-scanning direction is 1/12 of the recording pixel. The case where it is １ ／ of the above will be described. At this time, since the energy density of the condensed light is four times the amount of light emitted as compared to the reference energy density, it is condensed to ４.
4 × 4 = 16 times (actually, there is a loss of the optical system).

The energy density required to melt the hot-melt ink on the ink donor film 10 actually varies depending on the hot-melt ink and the type of the recording paper 11, but here the reference energy density is used. Is set to about 1, and about 900 times. Therefore, the condensed light generated when the light emitted from the LED 1a having an area four times as large as the recording pixel is condensed so that the sub-scanning direction is １ ／ of the recording pixel,
Assuming that the energy density can be increased to about 13 times in consideration of the loss of the optical system, the energy density is further increased by repeatedly irradiating the ink donor film 11 with about 70 times of condensed light, thereby condensing the light. The heat-meltable ink in the light-irradiated portion can be melted. At this time, if the pre-heat is given to the irradiated portion of the condensed light by light irradiation or the like to an adjacent area, the number of times of irradiation of the condensed light can be reduced according to the pre-heating.

FIG. 2 shows the application of a voltage pulse to the LED 1a and the ink donor film 10 and the recording paper 1 for each gradation reproduction.
This is a timing chart showing the timing of one transport,
FIG. 3 shows recording pixels at the time of reproducing each gradation in FIG. First,
In the first gradation, no voltage pulse is applied to the LED 1a, and FIG.
Is represented by no printing as shown by the recording pixel A. In the second gradation, while the conveyance of the ink donor film 10 and the recording paper 11 is stopped, a voltage pulse of 72 times is repeatedly applied to the LED 1a, and the condensed light is irradiated onto the ink donor film 10 72 times. At this time, the condensed light is applied to one-fourth the area of the recording pixel, so that the heat-fusible ink of one-fourth the area of the recording pixel is reliably melted and transferred to the recording paper 11, and the recording pixel B Dot can be recorded.

In the third gradation, after the same recording as that in the second gradation is performed, the ink donor film 10 and the recording paper 11 are conveyed 1/16 of the recording pixels in the sub-scanning direction, and 18 LEDs are supplied to the LED 1a.
The condensed light is irradiated onto the ink donor film 10 18 times by repeatedly applying the voltage pulse twice. At this time, the region s irradiated with the condensed light for the first time is irradiated with the condensed light only 18 times, but the adjacent region is heated to a temperature at which the fusion transfer can be performed at the time of recording the second gradation. Then, the heat-meltable ink is reliably melted and transferred to the recording paper 11, and the recording pixel C whose recording area is enlarged by 1/16 of the recording pixel in the sub-scanning direction from the second gradation is recorded.

After the fourth gradation, the ink donor film 1
When the recording paper 11 is conveyed 1/16 of the recording pixel in the sub-scanning direction and the voltage pulse is repeatedly applied to the LED 1a 18 times and the condensed light is irradiated on the ink donor film 10 18 times, the recording area is increased. Are sequentially recorded in the sub-scanning direction from the gray scale of the recording pixels D, E,.

The recording pixel F has a maximum density of 14 gradations.
Recording is performed by transporting the ink donor film 10 and the recording paper 11 12 times for the second gradation, and repeatedly applying 18 voltage pulses to the LED 1a for each transport.
After the recording of the recording pixels is completed, the ink donor film 10 and the recording paper 11 are moved to the next recording pixel area adjacent to the recording pixel in the sub-scanning direction.
It is conveyed four times by six.

Next, the result of actually performing halftone printing by the above method will be described with reference to FIGS. FIG. 4 is a timing chart showing the timing of applying a voltage pulse to the LED 1a and transporting the ink donor film 10 and the recording paper 11 at each tone reproduction. At this time, the emitted light generated by the LED 1a is condensed so that the sub-scanning direction becomes 1/12 of the recording pixel and is irradiated onto the ink donor film 10, and the conveyance of the ink donor film 10 and the recording paper 11 1/2 of the length of the pixel in the sub-scanning direction
Intermittent conveyance at 88 intervals.

At this time, the energy density of the LED 1a
The length of the emitted light generated in the sub-scanning direction is 1 /
4 and 3 times as much as the light collected in FIG. 2 (FIGS. 2 and 3).
By repeatedly irradiating the film 10, the energy density can be further increased, and the heat-meltable ink in the portion irradiated with the condensed light can be melted. Accordingly, as shown in FIG. 4, in the second gradation, the conveyance of the ink donor film 10 and the recording paper 11 is stopped, and 24 times of the voltage pulse is repeatedly applied to the LED 1a. The heat-meltable ink having the area of was surely melted and transferred to the recording paper 11 for recording.

In the third tone, after the same recording as that in the second tone is performed, the ink donor film 10 and the recording paper 1 are printed.
1 is conveyed 1/288 of the recording pixel in the sub-scanning direction and LED1
a by applying a voltage pulse once to a.
Irradiate twice. 1/28 following 1/12 area of recording pixel
In the area 8, the adjacent area is heated to a temperature at which the fusion transfer can be performed at the time of recording the second gradation. The image is transferred onto the paper 11 and recorded with the recording area enlarged by 1/288 of the recording pixel in the sub-scanning direction from the second gradation.

After the fourth gradation, the ink donor film 1
0 and the recording paper 11 in the sub-scanning direction
By transporting and applying a voltage pulse to the LED 1a once, the recording area is sequentially reduced to 1/288 of the recording pixel in the sub-scanning direction.
Enlarge and record each time.

FIG. 5 is a graph showing a comparison between the gradation characteristics obtained by the halftone printing and the theoretical values. The straight line indicates the theoretical values, and each point indicates the actual gradation characteristics. Here, the ink donor film 1
Recording was performed on synthetic paper using a high-resolution ink donor film (PET substrate thickness 3.5 μm, ink coating amount 1.5 g / m ² ) as 0. According to the halftone recording, smooth halftone recording from low density to high density, which is particularly excellent in highlight characteristics, can be performed, and the number of reproduction gradations is 128 to 256.
The gradation could be obtained.

According to the thermal transfer recording method, the light emitted from the LED 1a having an area larger than the recording pixel is condensed by the optical lens 2 so that the length in the sub-scanning direction is shorter than that of the recording pixel, and the energy density is increased. Since the light is irradiated onto the ink donor film as light, a heat generation region having a high energy density and a small area can be formed on the ink donor film 10. Then, the number of repetitive application of the voltage pulse to the LED 1 a and the conveyance of the ink donor film 10 are controlled, and the area to be melted on the ink donor film 10 is repeatedly irradiated with the condensed light, so that the condensed light irradiation part Is further increased, so that the heat-fusible ink can be reliably melted and transferred to recording paper. Further, since the ink donor film 10 is intermittently conveyed at a minute interval and the condensed light irradiation area having a small area is moved, the recording area can be gradually increased step by step.
Halftone printing can be performed by changing the area of the dots in the printing pixels according to the density data of each pixel.

Further, the heat generation area on the ink donor film 10 is miniaturized by condensing the light emitted from the LED 1a having a larger area than the recording pixel through the optical lens 2, so that the light emission at each LED 1a is reduced. Since the influence of the variation in the amount on the recording pixels is small, it is possible to perform smooth halftone recording with particularly excellent highlight characteristics.

Next, the thermal transfer recording apparatus according to the present invention will be described with reference to the schematic configuration diagram shown in FIG. The thermal transfer recording apparatus includes a light emitting element array 1 in which a plurality of light emitting elements 1a are arranged in the main scanning direction, a driving unit 3 for applying a voltage pulse to each light emitting element 1a, and an ink donor film 10 side on the light emitting element array 1. And a transport unit 4 comprising a transport roller 4a for transporting the ink donor film 10 and the recording paper 11 and a transport control unit 4b for controlling the operation thereof. Hereinafter, an example in which an LED is used as the light emitting element 1a will be described.

The LED array 1 has a plurality of LEDs 1a arranged in a line in the main scanning direction and has a resolution of about 300 DPI, and its light emitting surface faces the ink donor film 10. Each of the LEDs 1a has a length in the sub-scanning direction longer than that of a recording pixel, has the same length in the main scanning direction as that of the recording pixel, and has a light emitting area larger than the recording pixel area. Each LED1
a is connected to the driving means 3 and emits light when a voltage pulse is applied from the driving means 3; Increases or decreases.

Since the optical lens 2 has a semicircular cross-section in the sub-scanning direction with the LED array 1 side as the base, the light emitted from each LED 1a is condensed in the sub-scanning direction and energy is reduced. The ink donor film 10 is irradiated as condensed light having a small area with increased density. At this time,
No light is collected in the main scanning direction. The light collection rate of the emitted light can be changed according to the shape of the optical lens 2.

The LED surface side of the ink donor film 10 is made black so as to generate heat by light absorption (not shown). When the energy density due to the irradiation of the condensed light reaches a certain level or more, an ink donor film is formed. The hot-melt ink applied on the sheet 10 is melted and transferred to the recording paper 11.

Next, a method of performing halftone recording by the above-described thermal transfer recording apparatus will be described. Since the energy density of the condensed light is not enough to melt the hot-melt ink on the ink donor film 10, the energy density of the condensed light is determined based on the density data of each pixel on the ink donor film according to the density data. In other words, it is necessary to further increase the energy density by repeatedly irradiating the condensed light to give an energy density capable of melting the hot-melt ink. The number of times of irradiation of the condensed light is calculated by dividing the energy density necessary for melting the hot-melt ink by the energy density of one irradiation of the condensed light. At this time, if the pre-heat is given to the irradiated portion of the condensed light by light irradiation or the like to an adjacent area, the number of times of irradiation of the condensed light can be reduced according to the pre-heating.

The driving means 3 applies the same number of voltage pulses to the corresponding LED 1a so that the area to be melted corresponding to the density data of each pixel is irradiated with the above-mentioned number of condensed lights. Is repeatedly applied. In addition, the transport control unit 4b
During a period in which a voltage pulse is repeatedly applied to the LED 1a corresponding to the region to be melted, the transport roller 4a is set so that the region remains within the irradiation range of the condensed light.
Is driven to convey the ink donor film 10 and the recording paper 11. By synchronizing the operation of the driving unit 3 and the conveyance control unit 4b by a control unit (not shown), the heat-meltable ink in the area to be melted is reliably melted and transferred to the recording paper 11. Can be.

The transport controller 4b drives the transport roller 4a so that the ink donor film 10 and the recording paper 11 are transported intermittently in units of intervals shorter than the length of the recording pixels in the sub-scanning direction. By this intermittent conveyance, the area of the dots in each recording pixel can be increased stepwise.

According to the thermal transfer recording apparatus, the light emitted from the LED 1a having a larger area than the recording pixel is condensed by the optical lens 2 so that the length in the sub-scanning direction is shorter than that of the recording pixel, and the energy density is increased. Since the light is irradiated onto the ink donor film as light, a heat generation region having a high energy density and a small area can be formed on the ink donor film 10. And the ink donor film 1
Drive means 3 so that the area to be melted on 0 obtains the energy density necessary to melt the hot melt ink.
, A voltage pulse is repeatedly applied to the corresponding LED 1a, and the transport control unit 4b controls the ink donor film 1 during a period in which the voltage pulse is repeatedly applied.
Since the ink donor film 10 is conveyed so that the above-mentioned area of 0 stays within the irradiation range of the condensed light, the heat-meltable ink in the converged light irradiation part can be reliably melted and transferred to the recording paper. Further, the ink control unit 4b intermittently conveys the ink donor film 10 at a small interval and moves the condensed light irradiation region having a small area, so that the recording area can be sequentially increased step by step, and the density of each pixel can be increased. Halftone printing can be performed by changing the area of the dots in the printing pixels according to the data.

Further, the heat generating area on the ink donor film 10 is miniaturized by condensing the light emitted from the LED 1a having a larger area than the recording pixel through the optical lens 2, so that the light emitted from each LED 1a is reduced. Since the influence of the variation in the amount on the recording pixels is small, it is possible to perform smooth halftone recording with particularly excellent highlight characteristics. By changing the shape of the optical lens 2 to increase the light collection rate in the sub-scanning direction, it is possible to form a heat generation region having a higher energy density and a smaller area, and perform multi-tone halftone printing. it can.

In the above description, the LED array is used as the light emitting element array 1. However, the same effect can be obtained by using a laser diode array in which a plurality of laser diodes are arranged in the main scanning direction. Can play. Further, the optical lens 2 is not limited to a lens having a semicircular cross section in the sub-scanning direction, and may be any lens that can collect light emitted from the light emitting element in the sub-scanning direction. Also, each L
The light emission amount of the ED 1a is controlled by changing the number of voltage pulses to each LED 1a by the driving unit 3, but a method of changing the voltage application time to each LED 1a is also conceivable.

[0044]

According to the present invention, light emitted from a light emitting element having a larger area than a recording pixel is condensed by passing through an optical lens, and condensed light having an increased energy density is formed on the ink donor film. By irradiating the ink, a heat generation region having a high energy density and a small area can be formed on the ink donor film. Then, the number of repetitive application of the voltage pulse to the light emitting element and the conveyance of the ink donor film are controlled, and the area to be melted on the ink donor film is repeatedly irradiated with the condensed light to melt the hot melt ink. , The energy density of the focused light irradiation area can be further increased, and the heat-fusible ink can be reliably melted and transferred to recording paper. Furthermore, since the ink donor film is intermittently conveyed at minute intervals and the condensed light irradiation area having a small area is moved, the recording area can be gradually increased step by step, and recording is performed in accordance with the density data of each pixel. Halftone printing can be performed by changing the area of a dot in a pixel.

Further, the heat generating area formed on the ink donor film is miniaturized by condensing the light emitted from the light emitting element having a larger area than the recording pixel through the optical lens. Since the influence of the variation in the amount on the recording pixels is small, it is possible to perform smooth halftone recording with particularly excellent highlight characteristics. By changing the shape of the optical lens to increase the light collection rate in the sub-scanning direction, it is possible to form a heat generation region having a higher energy density and a smaller area, and perform multi-tone halftone printing. it can

[Brief description of the drawings]

FIG. 1 is an enlarged sectional explanatory view in the sub-scanning direction showing a method of condensing light emitted from a light emitting element by a thermal transfer recording method of the present invention.

FIG. 2 is a timing chart at the time of halftone recording by the thermal transfer recording method of the present invention.

FIG. 3 is an explanatory diagram showing a print result of halftone recording by the thermal transfer recording method of the present invention.

FIG. 4 is a timing chart at the time of halftone recording by the thermal transfer recording method of the present invention.

FIG. 5 is an explanatory diagram of gradation characteristics of halftone recording by the thermal transfer recording method of the present invention.

FIG. 6 is a schematic diagram illustrating the configuration of a thermal transfer recording apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light emitting element array, 1a ... Light emitting element, 2 ... Optical lens, 3 ... Driving means, 4 ... Conveying means, 4a ... Conveying roller, 4b ... Conveying control part, 10 ... Ink donor film, 11 ... Recording paper

Claims (5)

[Claims] 1. A light-emitting element having a length in the sub-scanning direction longer than a recording pixel is arranged in a row in the main scanning direction, and light emitted by applying a voltage pulse to each of the light-emitting elements can be condensed in the sub-scanning direction. As a condensed light having a length in the sub-scanning direction shorter than the recording pixel by passing through a simple optical lens, onto the ink donor film coated with the heat-meltable ink, and the density data of each pixel on the ink donor film. In order to repeatedly irradiate the condensed light to the region to be melted in accordance with the above, while repeatedly applying a voltage to the light emitting element and transporting the ink donor film, further transporting the ink donor film, The intermittent conveyance is performed in units of intervals shorter than the length of the recording pixels in the sub-scanning direction, and the hot-melt ink melted according to the density data of each pixel is transferred to recording paper. And performing halftone printing by changing the area of the dots in each printing pixel. 2. A light-emitting element array in which a plurality of light-emitting elements whose length in the sub-scanning direction is longer than a recording pixel are arranged in the main scanning direction, and a voltage pulse of a number of times corresponding to the density data of a pixel corresponding to each light-emitting element. Driving means for controlling the number of times of light emission generated by each light emitting element by applying the light, and arranged on the light emitting surface side of each light emitting element, condensing the emitted light in the sub-scanning direction, and arranged on the side opposite to the light emitting element An optical lens for irradiating condensed light whose length in the sub-scanning direction is shorter than a recording pixel on the ink donor film coated with the heat-meltable ink, and an interval shorter than the length of the recording pixel in the sub-scanning direction of the ink donor film. Transport means for transporting the condensed light repeatedly so as to repeatedly irradiate the area to be melted according to the density data of each pixel on the ink donor film, A thermal transfer printing apparatus, characterized in that the heat-fusible ink melted in accordance with the density data of each pixel is transferred to a recording sheet, and halftone printing is performed by changing the area of the dots in each recording pixel. 3. The thermal transfer recording apparatus according to claim 2, wherein the optical lens has a semicircular cross section in the sub-scanning direction with the light emitting element side as a base. 4. A thermal transfer recording apparatus according to claim 2, wherein each of said light emitting elements comprises a light emitting diode. 5. A thermal transfer recording apparatus according to claim 2, wherein each of said light-emitting elements comprises a laser diode.