JP2001293893A - Thermal recorder and thermal recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recorder and a thermal recording method in which a high quality image can be formed on a thermal recording medium with a thermally pumped laser light. SOLUTION: The thermal recorder comprises means for forming a color developing image on a thermal recording medium 14, having a thermal recording layer developing a color continuously at a density corresponding to thermal energy being supplied, by irradiating it with a light beam modulated according to an information record thereby supplying a specified color developing thermal energy. Energy density is made uniform in the cross-section of an outgoing beam using a unit for correcting the intensity distribution of a modulated light beam 11 outgoing from an exit plane to be substantially uniform over the entire exit plane thus making the energy density uniform in the cross-section of the outgoing beam. Consequently, difference in the intensity distribution of laser light is eliminated between the central part and the peripheral part on the irradiating plane of the thermal recording medium and uniform thermal pumping is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus and a thermal recording method for recording an image or the like using the photothermal effect of a thermally excited laser beam.

[0002]

2. Description of the Related Art Conventionally, there has been known a thermal recording method for recording an image or the like by applying thermal energy to a thermal recording medium as one of image forming means. In particular, attention has been paid to a method in which a laser is used as a heat source of thermal energy and thermal recording is performed at high speed and high density without contact with a thermosensitive recording medium by the photothermal effect of a laser beam (Japanese Patent Laid-Open No. 3-86581). And JP-A-8-267920). However, in a thermal recording apparatus that records an image or the like by using the photothermal effect and imparting thermal energy generated thereby, the light intensity distribution of a laser beam generally used has a luminance near the center of the beam. Since the temperature is higher and the Gaussian distribution becomes weaker toward the periphery, the so-called non-uniform light-to-heat conversion on the thermosensitive recording medium has been performed. This has a great effect on forming beam dots in a thermal recording method for recording an image or the like by applying thermal energy to a thermosensitive recording medium with a laser beam, and in this case, within a laser spot on a sample surface. Since uniform heat generation and color development cannot be expected, there arises a problem that printing quality is deteriorated. Further, there is a problem that the dot size for coloring becomes smaller than the beam spot diameter. In addition, there is a problem that high gradation reproducibility is lost even when gradation is expressed by two-dimensional beam dots such as dither processing.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and problems and to provide a thermal recording apparatus and a thermal recording apparatus capable of forming a high-quality image or the like on a thermal recording medium by a thermally excited laser beam. Is to provide a way.

[0004]

Means for Solving the Problems The present inventor uses the light beam intensity distribution correcting device so that the energy density in the cross section of the output beam can be made uniform and compared with the case where light is condensed by a lens. To eliminate the difference in the intensity distribution of the laser beam between the center and the periphery of the beam on the sample surface, confirm that uniform thermal excitation is performed, and that a good image can be obtained.
The present invention could be reached.

A first aspect of the present invention is to irradiate a heat-sensitive recording medium having a heat-sensitive recording layer which continuously develops a color at a concentration corresponding to the supplied thermal energy with a light beam modulated according to information recording to a predetermined temperature. In a thermal recording apparatus having a means for forming a color image on the thermosensitive recording medium, the intensity distribution of the light beam emitted from the emission surface is substantially uniform over the entire emission surface. The thermal recording apparatus is characterized by using a light beam intensity distribution correcting device. By using the thermal recording device, a laser beam having a uniform intensity distribution can be obtained from the emission end face of the light beam intensity distribution correcting device. Can be thermally excited.

The light beam intensity distribution correction device includes:
For example, a device having a surface on which a thermally excited laser beam is totally reflected in a metal surface or glass, and which can make the intensity distribution uniform by passing the thermally excited laser beam through a cylindrical quartz having a predetermined size. However, a kaleidoscope is particularly preferable because the laser light intensity distribution has a characteristic of being substantially uniform in the emission pattern. That is, the second aspect of the present invention
In the first thermal recording device, the light beam intensity distribution correcting device is a kaleidoscope.

A third aspect of the present invention is to irradiate a heat-sensitive recording medium having a heat-sensitive recording layer which continuously develops a color at a density corresponding to the supplied thermal energy with a light beam modulated in accordance with information recording to a predetermined temperature. In the thermal recording method of supplying a coloring heat energy to form a colored image on the thermosensitive recording medium, the intensity distribution of the modulated light beam emitted from the emission surface is substantially uniform over the entire emission surface. Using an intensity distribution correction device, the energy density in the cross section of the emitted beam is made uniform, and the difference in the intensity distribution of the laser beam between the center and the periphery of the beam on the irradiation surface of the thermal recording medium is eliminated, resulting in uniform thermal excitation. In a thermal recording method.

As described above, the present invention uses a light beam intensity distribution correcting device, for example, a kaleidoscope, to provide a recording method using a recording laser beam, for example, a thermally excited argon ion laser beam for recording. Until now, when forming a color image, the intensity distribution of the laser beam had a high brightness near the center of the beam and a weak Gaussian distribution toward the periphery, so beam dot images were formed by non-uniform photothermal conversion. However, the difference in the intensity distribution of the laser beam between the center and the periphery of the beam on the thermal recording medium can be eliminated, and color development can be achieved by uniform thermal excitation in the beam spot, resulting in higher quality. Image and the like can be formed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention. When recording an image on the light-absorbing thermosensitive recording layer inside the protective layer or on the thermosensitive recording layer that is the surface layer using the photothermal recording method using a laser, The point is to uniformly thermally excite the entire portion of the recording medium irradiated with the laser light. Laser light as thermal excitation light
When irradiating the sample surface for photothermal recording, the power intensity of the laser beam usually has a Gaussian distribution in which the center is high and the periphery is low. Therefore, when the sample surface is irradiated with the thermally excited laser light, the temperature distribution on the irradiated surface becomes higher at the center and lower toward the periphery in accordance with the power intensity of the laser light. In this case, the heat generated in the sample depends on the power intensity of the laser beam, and generally, the higher the power, the larger the amount of heat generated. As a result, the intensity distribution of the heat excitation light that affects the amount of heat generated becomes non-uniform in the laser irradiation surface, causing a problem that the coloring accuracy is greatly adversely affected. This is remarkable especially when the laser irradiation area is large.

This embodiment provides a laser photothermal recording apparatus and a recording method for solving these problems. FIG. 1 shows a configuration example of a thermal recording apparatus used in the present invention. 1 is a polygon mirror, 2 is an Ar ion laser light source, 15 is an acousto-optic device for modulation, 17 is a kaleidoscope, 3 is a spherical lens, 4 is a toroidal lens, 5 is a reflection mirror, 6 is linearly polarized light such as elliptically polarized light. Is a f-θ lens system composed of a spherical lens 3 and a toroidal lens 4. 11 is a thermally excited laser beam,
Reference numeral 12 denotes reflected light. Here, the light source is composed of one type of dye laser using the Ar ion laser 2 as a heat excitation light source, and oscillates at a wavelength in the visible region.

In this embodiment, it is necessary to use, as the thermally excited laser beam 11, light having a wavelength that can pass through the protective layer 8 shown in FIG. An Ar ion laser light source 2 having an oscillation wavelength of 514.5 nm and an output of 180 mW predicted from the spectral transmission data of the polyvinyl acetoacetal resin used in the embodiment is used. When the excitation light wavelength for recording is selected, it is preferable that the wavelength is the absorption band peak of the thermosensitive recording layer 9 inside the protective layer 8 which is the test object. Any band is acceptable.

Further, the modulated thermally excited laser light is
The polarization direction of the electric field component is linearly polarized light having the same direction as the vertically polarized light, and the angle of incidence on the surface layer of the thermosensitive recording medium is ± 5 d from the Brewster angle determined by the refractive index of the surface layer.
eg. In order to increase the efficiency of the light-to-heat conversion process in the internal light-absorbing thermosensitive recording layer due to the high internal light arrival rate, heat is continuously emitted at a concentration corresponding to the supplied heat energy. The effect of forming an image with a laser beam with limited light power is added to the recording medium. The angle に お け る in FIG. 3 indicates a Brewster angle.

The procedure is as follows. First, the light flux emitted from the Ar ion laser light source 2 as the heat excitation light is passed through the acousto-optic device 15 and then from the incident lens 16 shown in FIG. The light is guided to a certain kaleidoscope 17. When the light enters the kaleidoscope 17 from the entrance lens 16, the intensity distribution is made uniform and exits, and the polygon mirror 1 is irradiated by the imaging lens 18.

In order to perform ON-OFF modulation of thermal excitation recording by thermal excitation laser beam irradiation, in the case of a semiconductor laser, an electrical ON-OF by a control device via a driver is used.
Although F modulation can be performed, in the case of an Ar ion laser, ON-OFF modulation using an acousto-optic element is mainly used.
The modulation bandwidth of the acousto-optic element is determined by the high frequency ultrasonic frequency of the transducer, and is practically a modulation frequency of about 1/10 or less of the ultrasonic frequency.

The kaleidoscope 17 which is a light beam intensity distribution correction device has, for example, an inner diameter of 0.5 mm and a total length of 50 mm.
A quartz kaleidoscope having a size of mm and a total reflection surface formed on an inner surface or the like is used. At this time, the laser light, which is the thermal excitation light entering from the incident end face of the kaleidoscope, travels while repeating reflection on the total reflection surface, and the intensity distribution is made uniform within a pattern with an inner diameter of 0.5 mm. Are emitted from the emission end face. Therefore, the pattern of the thermally excited laser light from the exit end face of the kaleidoscope, which is a light beam intensity distribution correction device, becomes a circular shape according to the shape of the exit end face of the kaleidoscope, and the intensity distribution in the pattern is almost uniform. Come. In this case, the light beam intensity distribution correction device is not limited to the kaleidoscope, and when the laser light is totally reflected on the inner surface and exits from the emission end face, the laser light intensity distribution becomes substantially uniform in the emission pattern. If it is a device with characteristics, it can be applied.

The cross-sectional shape of the exit end of the thermal excitation laser beam intensity distribution correction device is not limited to a circle, but an arbitrary shape device such as a square shape such as a square or a rectangle can be used. For example, even with a kaleidoscope with a rectangular cross section composed of four strip-shaped reflectors using copper with good thermal conductivity as the material, the laser beam multiple-reflects the space surrounded by these reflectors. The laser beam propagates while making the power distribution of the laser beam uniform, so that there is no sag in the intensity distribution in the beam.

Generally, the longer the length of the kaleidoscope, that is, the greater the number of times of reflection of the laser beam on the inner wall of the kaleidoscope, the more uniform the output beam becomes. And the overall size of the optical system becomes large. After being reflected by the polygon mirror 1 disposed near the incident light of the f-θ lens system 7 and transmitted through the f-θ lens system 7, the light is deflected by the reflection mirror 5, and further, the scanning parallel light is changed to linearly polarized light. The surface of the protective layer 8 of the thermal recording medium 14 is sequentially scanned through the element 6. The polygon mirror 1 has been put to practical use as an optical deflector for realizing high-speed writing. Its features are that its deflection characteristics are basically invariant with respect to the wavelength used, and that it can deflect with a wide angle and a high resolution. There are things that can be done, and that a laser beam can be emitted at a relatively high speed.

In the present embodiment, after the Ar ion laser is added from the light source 2 to the polarization characteristics at high speed, the surface of the thermosensitive recording medium to be conveyed in the sub-scanning direction is perpendicular to the conveying direction, that is, the thermosensitive recording medium 14. A two-dimensional image is recorded by supplying a predetermined coloring energy to the thermosensitive recording medium 14 by performing main scanning with a laser beam linearly modulated in accordance with recording information in the width direction. As described above, the light-absorbing thermosensitive recording layer 9 inside the protective layer 8
Thus, since a uniform optical absorption-heat conversion coloring process occurs, there is no problem that the coloring dot size becomes smaller than the beam spot diameter, and two-dimensional processing such as dither processing is performed. Even when gradation is expressed by an aggregate of various beam dots, photothermal conversion and color printing corresponding to the beam diameter can be obtained.

Although the above description has been made with reference to a thermosensitive recording medium in which the surface layer is a protective layer, the protective layer is optional. That is, as shown in FIG. 3, the heat-sensitive recording medium of the present invention has a heat-sensitive recording layer 9 provided on a support 10, and a protective layer 8 is further provided on the heat-sensitive recording layer 9 if necessary. It is a thing. Paper, synthetic paper,
Examples include resin sheets.

Specific examples of the heat-sensitive recording medium in the present invention include (1) a heat-sensitive recording medium (such as a thermal paper, which includes a reversible heat-sensitive recording medium and an irreversible recording medium); (2) thermal transfer recording media (thermal transfer ribbon etc.),
There are (3) a sublimation type recording transfer recording medium, and (4) a thermal diazo recording medium, and the like. However, the medium is not limited to these, and may be any medium that can generally record characters, figures, and the like by heat. Further, the layer structure of these thermosensitive recording media can take various structures.

The thermosensitive recording medium of the present invention may or may not have a support. Further, an under layer (primer layer, release layer), a recording layer (there may be a plurality of layers), an intermediate layer, a protective layer, a print layer, a magnetic recording layer, a print layer and a protective layer (for example, OP varnish) on the support. Layers) are formed as necessary, apart from the essential recording layer.

[0022]

According to the present invention, in the optical system of the thermal recording method, when a thermal excitation laser beam intensity distribution correction device, for example, a kaleidoscope is used, excitation is performed in a state where the intensity distribution is uniform on the sample irradiation surface. Since the light can be irradiated, the entire irradiated portion can be thermally excited uniformly, and a color dot size equal to the beam spot diameter can be obtained. Therefore, a high-quality laser light thermal recording method having high gradation reproducibility can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one configuration example of a thermal recording apparatus used in the present invention.

FIG. 2 is an incident lens 1 of a thermal recording apparatus used in the present invention.
6 is a diagram showing a kaleidoscope 17 which is a light beam intensity distribution correction device, an imaging lens 18, and the polygon mirror 1. FIG.

FIG. 3 is a diagram illustrating one configuration example of a thermosensitive recording medium and the behavior of a laser beam applied to the thermosensitive recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon mirror 2 Ar ion laser light source 3 Spherical lens 4 Toroidal lens 5 Reflection mirror 6 Polarizer 7 f-theta lens system 8 Protective layer 9 Thermal recording layer 10 Support 11 Thermal excitation laser light 12 Reflected light 13 Refracted transmitted light 14 Heat sensitive Recording medium 15 Acousto-optical element 16 Incident lens 17 Kaleidoscope 18 Imaging lens

Claims (3)

[Claims] 1. A thermosensitive recording medium having a thermosensitive recording layer that continuously develops a color at a concentration corresponding to the supplied thermal energy,
In a thermal recording apparatus having a means for irradiating a light beam modulated in accordance with information recording to supply a predetermined coloring heat energy and forming a color image on the thermosensitive recording medium, the modulated light beam is emitted from an emission surface. A thermal recording apparatus using a light beam intensity distribution correction device that makes the intensity distribution of the emitted light beam substantially uniform over the entire exit surface. 2. The thermal recording apparatus according to claim 1, wherein the light beam intensity distribution correcting device is a kaleidoscope. 3. A heat-sensitive recording medium having a heat-sensitive recording layer that continuously develops a color at a concentration corresponding to the supplied thermal energy,
In a thermal recording method of irradiating a light beam modulated in accordance with information recording and supplying a predetermined coloring heat energy to form a coloring image on the thermosensitive recording medium, the modulated light beam is emitted from an emission surface. Using a light beam intensity distribution correction device that makes the beam intensity distribution almost uniform over the entire exit surface, the energy density within the cross section of the exit beam is made uniform, and the center and periphery of the beam on the irradiation surface of the thermal recording medium A thermal recording method characterized by eliminating a difference in intensity distribution of laser light in a portion and performing uniform thermal excitation.