Patent Description:
Conventionally, there are two major laser full-color recording methods, as follows. A first method is for applying energy, with a laser, to a medium including three primary color developing layers having different threshold temperatures laminated on one another, to selectively develop color from the three primary color developing layers.

For example, a known method is such that three primary colors are selectively developed by raising or lowering a focus position of laser light through a lens in accordance with an intended layer.

Another known method is such that heat is applied with a laser to a medium including three primary color developing layers having different color temperature thresholds laminated on one another, to develop a color from one of the layers with a lowest threshold temperature, and then eliminate heat sensitivity of the color developing layer with ultraviolet light to change the color developing layer so as not to develop a color by heat. Subsequently, the same process applies to the color developing layer with the second lowest threshold temperature and the color developing layer with the highest threshold temperature for color development, completing full-color recording.

A second method is such that three primary colors are developed for recording from three primary color layers having absorption characteristics at different wavelengths, using lasers having three different wavelengths from one another.

For example, a known method is to complete full-color recording by using a multilayer element that includes at least one layer containing laser sensitive material, and absorbing laser light to develop a color or remove a color for recording each color.

However, the first method requires a certain length of time for transferring heat to a low-temperature color developing layer, which may elongate a total printing time.

The second method requires lasers having three different wavelengths, which may lead to increase the size and cost of a device.

Further, <CIT> discloses a laser recording device which performs recording by irradiating a recording medium with laser light. The recording medium includes thermal recording layers including thermal materials with different color development threshold temperatures and stacked in an ascending order of the threshold temperatures of the included thermal materials from a surface irradiated with the laser light; and an intermediate layer provided between the thermal recording layers to perform thermal insulation and thermal conduction. The laser recording device includes a controller. The controller sets a power density of the laser light and an irradiation time and performs recording on the thermal recording layers by controlling irradiation with the laser light.

<CIT> discloses an information recording medium having a front surface and a back surface which has a first color developing layer, a second color developing layer and a third color developing layer. The first color developing layer develops yellow at a temperature not less than a first threshold value. The second color developing layer is arranged at the back surface side with respect to the first color developing layer. The second color developing layer develops magenta at a temperature not less than a second threshold value that is lower than the first threshold value. The third color developing layer is arranged at the front surface side with respect to the first color developing layer. The third color develops cyan at a temperature not less than a third threshold value that is higher than the first threshold value.

<CIT> discloses imaging members which comprise a substrate having first and second opposed surfaces, said surface bearing at least a first color-forming layer, a first thermally-insulating interlayer, a second color-forming layer, a second thermally-insulating layer, and a third color-forming layer, wherein said first color-forming layer has a higher activation temperature than said second color-forming layer, and said second color-forming layer has a higher activation temperature than said third color-forming layer, said thermal imaging member further comprising a radiation-absorbing material that is located either within said first color-forming layer or in a layer that is closer to said first color-forming layer than to any other color-forming layer.

<CIT> discloses a recording medium with a substrate and a first color developing layer, a heat insulating layer and a second color developing layer laminated on the substrate in this order. The first color developing layer develops a first color at a temperature not less than a first threshold value. The second color developing layer develops a second color that is different from the first color at a temperature not less than a second threshold value that is higher than the first threshold value. The heat insulating layer has a first heat insulating layer of a first heat conductivity and a second heat insulating layer of a second heat conductivity that is higher than the first heat conductivity, which are laminated in a second direction orthogonal to a first direction in which the first color developing layer, the heat insulating layer, and the second color developing layer are laminated on the substrate.

<CIT> discloses multi-layer articles that are capable of forming color images. The articles may contain at least two layers, a thermally activatable layer and a blocking layer, or at least three layers with two thermally activatable layers and a blocking layer between. The thermally activatable layers absorb light of a write wavelength and have an absorption threshold for activation. The blocking layer blocks light of the write wavelength at certain incident angles or polarization states and permits light of the write wavelength and certain incident angles or polarization states to pass through. The thermally activatable layers may be layers with a light to heat convertor composition and a color changing compound or they may be a group of layers arranged to change its reflective characteristic upon exposure to light while maintaining the structural integrity of the group of layers.

It is thus preferable to provide a recording medium and a recording device with a simple structure that can quickly record a full-color image, and achieve cost reduction. As such a recording medium, a recording medium is proposed that has the features of claim <NUM>. Moreover, a recording device is proposed that has the features of claim <NUM>.

According to one embodiment, in general, a recording medium includes the features of claim <NUM>. Moreover, according to another embodiment, a recording device has the features of claim <NUM>.

The following will describe exemplary embodiments in detail with reference to the drawings.

First, a recording medium according to a first embodiment is described.

<FIG> is a front view of exterior of a recording medium such as an anti-forgery and alteration medium according to the first embodiment while information is recorded.

A recording medium <NUM> on which information is recorded includes a full-color image region ARC on which a full-color image such as an identity photograph is recorded, and a monochrome image region ARM adjacent to the full-color image region ARC and includes specific information such as ID information, a name, and a date of issue in monochrome.

In <FIG>, the recording medium <NUM> includes a region in addition to the full-color image region ARC and the monochrome image region ARM, but the entire region excluding the full-color image region ARC may be set to the monochrome image region ARM.

In <FIG>, the full-color image region ARC and the monochrome image region ARM are adjacent to each other, but the full-color image region ARC and the monochrome image region ARM may be separated from each other. Alternatively, the number of one or both of full-color image regions ARC and monochrome image regions ARM may be plural.

<FIG> is a cross-sectional view of a configuration example of the recording medium in the first embodiment.

<FIG> is an explanatory diagram of a thermal conductivity ratio and a thickness of the recording medium in the first embodiment.

As illustrated in <FIG>, the recording medium <NUM> includes, on a base material <NUM>, a light absorption color developing layer <NUM> serving as a first color developing layer, a photothermal conversion layer <NUM>, a binder layer <NUM>, a high-temperature thermosensitive color developing layer <NUM> serving as a second color developing layer, an intermediate layer <NUM>, a medium-temperature thermosensitive color developing layer <NUM> serving as the second color developing layer, an intermediate layer <NUM>, a low-temperature thermosensitive color developing layer <NUM> serving as a second color developing layer, and a protection/function layer <NUM> in this order.

Each of the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> functions as a thermosensitive recording layer on which an image is recorded.

Each of the intermediate layer <NUM> and the intermediate layer <NUM> functions as a heat insulating layer for adjusting an amount of heat transfer and suppress heat transfer.

The base material <NUM> holds the light absorption color developing layer <NUM>, the photothermal conversion layer <NUM>, binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, and the protection/function layer <NUM>.

The thickness of the base material <NUM> is, for example, set to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K herein.

The light absorption color developing layer <NUM> contains pigment particles that absorb laser light as light and are carbonized, to irreversibly develop a color.

The thickness of the light absorption color developing layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K herein.

The photothermal conversion layer <NUM> functions to absorb light (laser light) having a given wavelength, and performs photothermal conversion to generate and transfer heat for causing at least one of the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> to develop a color.

The thickness of the photothermal conversion layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K herein.

The binder layer <NUM> functions to hold the light absorption color developing layer <NUM>, the photothermal conversion layer <NUM>, and the high-temperature thermosensitive color developing layer <NUM> at given positions while binding the light absorption color developing layer <NUM> and the high-temperature thermosensitive color developing layer <NUM>.

Herein, the thickness of the binder layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K.

The high-temperature thermosensitive color developing layer <NUM> is a layer containing a temperature indicating material as a thermosensitive material that develops a color when the temperature thereof becomes equal to or higher than a first threshold temperature T1.

The thickness of the high-temperature thermosensitive color developing layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K.

The intermediate layer <NUM> functions to provide a thermal barrier at the time when the high-temperature thermosensitive color developing layer <NUM> develops a color, and suppresses heat transfer from the high-temperature thermosensitive color developing layer <NUM> to the medium-temperature thermosensitive color developing layer and the low-temperature thermosensitive color developing layer.

Herein, the thickness of the intermediate layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K.

The medium-temperature thermosensitive color developing layer <NUM> contains a temperature indicating material as a thermosensitive material that develops a color when the temperature thereof becomes equal to or higher than a second threshold temperature T2 (< T1).

Herein, the thickness of the photothermal conversion layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K.

The intermediate layer <NUM> functions to provide a thermal barrier at the time when the medium-temperature thermosensitive color developing layer <NUM> develops a color, and suppresses heat transfer from the medium-temperature thermosensitive color developing layer <NUM> to the low-temperature thermosensitive color developing layer.

The low-temperature thermosensitive color developing layer <NUM> contains a temperature indicating material as a thermosensitive material that develops a color when the temperature thereof becomes equal to or higher than a second threshold temperature T3 (< T2 < T1).

The thickness of the low-temperature thermosensitive color developing layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K.

The protection/function layer <NUM> protects the light absorption color developing layer <NUM>, the photothermal conversion layer <NUM>, the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM>.

Additionally, the protection/function layer <NUM> is for arranging a forgery prevention item such as a hologram, a lenticular lens, a microarray lens, and ultraviolet excitation-type fluorescence ink, for inserting an inner protective item such as a UV cutting layer, or for using both of the functions.

The thickness of the protection/function layer <NUM> is, for example, set to <NUM> to <NUM>, and the thermal conductivity ratio thereof is set to <NUM> to <NUM> W/m/K herein.

The following describes a light absorption characteristic of the photothermal conversion layer <NUM>, the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, and the protection/function layer <NUM> in detail.

<FIG> is an explanatory diagram of an example of the light absorption characteristic of the photothermal conversion layer.

As illustrated in <FIG>, the photothermal conversion layer <NUM> has infrared ray absorption characteristic having an absorption peak at a wavelength λ (for example, λ = <NUM>) of a near infrared ray.

On the other hand, the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, and the protection/function layer <NUM> are formed of a material that transmits light having the wavelength λ of a near infrared ray (near infrared light). Thereby, light having the wavelength λ (near infrared light) absorbable by the light absorption color developing layer <NUM> or the photothermal conversion layer <NUM> can reach the light absorption color developing layer <NUM> or the photothermal conversion layer <NUM>.

Thus, in the full-color image region ARC, infrared light having the wavelength λ (for example, λ = <NUM>), emitted from the protection/function layer <NUM>, transmits through the low-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the binder layer <NUM> in this order.

The near infrared light having the wavelength λ is then substantially absorbed by the photothermal conversion layer <NUM> to be subjected to photothermal conversion, and causes the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, or the low-temperature thermosensitive color developing layer <NUM> to develop a color.

In the monochrome image region ARM, the near infrared light having the wavelength λ transmits through the protection/function layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the binder layer <NUM> in this order, is substantially absorbed by the light absorption color developing layer <NUM> to develop a color.

Next, the following describes materials of the respective layers.

First, the following describes the base material <NUM>.

Examples of the base material <NUM> include a resin that can be processed in a film or plate form, the resin such as a polyester resin, polyethylene terephthalate (PET), glycol modified polyester (PET-G), polypropylene (PP), polycarbonate (PC), polyvinyl chloride (PVC), a styrene-butadiene copolymer (SBR), a polyacrylic resin, a polyurethane resin, and a polystyrene resin, which are typically used as a card, paper, and a film material.

Additionally, by adding silica, titanium oxide, calcium carbonate, alumina, and the like to the above resin as a filler, a resin having whiteness, a surface smoothness, and an insulating property can be used as the base material <NUM>.

For example, paper (sheet) and a resin material disclosed in <CIT>, <CIT>, <CIT>, and <CIT> can be used in addition to the resins described above.

Specifically, examples of the base material <NUM> include polyethylene terephthalate (A-PET, PETG), polycyclohexylene dimethylene terephthalate (PCT), polystyrene (PS), polymethyl methacrylate (PMMA), transparent ABS (MABS), polypropylene (PP), polyethylene (PE), polyvinyl alcohol (PVA), a styrene-butadiene copolymer (SBR), an acrylic resin, an acrylic-modified urethane resin, a styrene/acrylic resin, an ethylene/acrylic resin, an urethane resin, a rosin-modified maleic acid resin, a vinyl chloride/vinyl acetate copolymer, a polyvinyl acetal resin, a polyamide resin, a cellulose-based resin such as hydroxyethyl cellulose, hydroxypropyl cellulose, and cellulose nitrate, other resins such as a polyolefin-based resin, a polyamide resin, a biodegradable resin, and a cellulose-based resin, a paper base material, a metal material, and the like.

The resins and the filler described above are merely examples, and other materials having sufficient workability and functionality can also be used.

In the configuration described above, it is preferable to use a white resin or a transparent resin.

Herein, the term "transparent" refers to light transmittance in a visible light region equal to or higher than <NUM>% in average.

Next, the following describes the photothermal conversion layer <NUM>.

The photothermal conversion layer <NUM> contains an infrared absorption (light absorption) exothermic material that transmits visible light and absorbs infrared light, and a binder resin. The light absorption exothermic material and the binder resin are mixed, in a solvent, to be applied so that a mass ratio of solid content between the light absorption exothermic material and the binder resin becomes the infrared absorption exothermic material: binder resin = <NUM> to <NUM>:<NUM> to <NUM>.

When the photothermal conversion layer <NUM> is applied, a film thickness thereof is preferably <NUM> to <NUM>, and is more preferably <NUM> to <NUM>.

Examples of the infrared absorption exothermic material contained in the photothermal conversion layer <NUM> include polymethine-based cyanine pigment, polymethine-based pigment, squarylium-based pigment, porphyrin-based pigment, metal dithiol complex-based pigment, phthalocyanine-based pigment, diimmonium-based pigment, inorganic oxide particles and the like, azo-based pigment, quinone-based pigment such as naphthoquinone-based pigment or anthraquinone-based pigment, cerium oxide, indium-tin oxide, antimony-tin oxide, cesium-tungsten oxide, lanthanum hexaboride, and the like.

Examples of the binder resin contained in the photothermal conversion layer <NUM> include cellulose esters such as cellulose nitrate, cellulose phosphate, cellulose sulfate, cellulose propionate, cellulose acetate, cellulose propionate, cellulose palmitate, cellulose myristate, cellulose acetate butyrate, and cellulose acetate propionate, and a cellulose-based resin such as a polyester-based resin, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl cellulose, methyl cellulose, and cellulose acetate.

Example of the binder resin contained in the photothermal conversion layer <NUM> include a vinyl-based resin such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyacrylamide, acrylic resins such as polymethyl acrylate and polyacrylic acid, polyolefins such as polyethylene and polypropylene, polyacrylate resins, epoxy resins, phenolic resins, and the like.

Specifically, representative examples of the binder resin include a PET-based resin, PETG, a PVC-based resin, a PVA-based resin, a PC-based resin, a PP-based resin, a PE-based resin, an ABS-based resin, a polyamide-based resin, and vinyl acetate-based resin. Additionally, examples of the photothermal conversion layer <NUM> include a copolymer based on the above resins, and a resin obtained by adding an additive such as silica, calcium carbonate, titanium oxide, and carbon to the above resins.

The binder layer <NUM> is typically made of the same resin as the binder resin of the photothermal conversion layer <NUM>.

Next, the following describes the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM>.

Exemplary materials of the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> include, as the binder resin, resins having high transparency such as polyvinyl alcohol, polyvinyl acetate, and polyacrylamide. Examples of a color developing material that develops a color at temperature over a certain threshold temperature include a leuco dye, leuco pigment, or a temperature indicating material, and a developer.

Examples of the leuco dye, the leuco pigment, or the temperature indicating material include a color developing dye such as <NUM>,<NUM>-bis (<NUM>-n-butyl-<NUM>-methyl-indole-<NUM>-yl) phthalide, <NUM>-(<NUM>-butyl-<NUM>-methyl-lH-indole-<NUM>-yl)-<NUM>-(<NUM>-diethylamino-<NUM>-methyl-phenyl)-<NUM>-furo[<NUM>,<NUM>-b]pyridine-<NUM>-one, <NUM>-(<NUM>,<NUM>-dichloro-phenylcarbamoyl)-<NUM>,<NUM>-dimethyl-<NUM>-oxo-<NUM>-phenoxy-butyl]-(<NUM>-diethylaminophenyl)-isobutyl carbamate, <NUM>,<NUM>-bis(p-dimethylaminophenyl)phthalide, <NUM>,<NUM>-bis(p-dimethylaminophenyl)-<NUM>-dimethylaminophthalide (another name: crystal violet lactone = CVL), <NUM>,<NUM>-bis(p-dimethylaminophenyl)-<NUM>-aminophthalide, <NUM>,<NUM>-bis(p-dimethylaminophenyl)-<NUM>-nitrophthalide, <NUM>,<NUM>-bis3- dimethylamino-<NUM>-methylfluoran, <NUM>-diethylamino-<NUM>-chlorofluoran, <NUM>-diethylamino-<NUM>-chloro-<NUM>-methylfluoran, <NUM>-diethylamino-<NUM>-anilinofluoran, <NUM>-diethylamino-<NUM>-methyl-<NUM>-anilinofluoran, <NUM>-(<NUM>-fluorophenylamino)-<NUM>-diethylaminofluoran, <NUM>-(<NUM>-fluorophenylamino)-<NUM>-di-n-butylaminofluoran, <NUM>-piperidino-<NUM>-methyl-<NUM>-anilinofluoran, <NUM>-(N-ethyl-p-toluidino)-<NUM>-(N-methylanilino)fluoran, <NUM>-(N-ethyl-p-toluidino)-<NUM>-methyl-<NUM>-anilinofluoran, <NUM>-N-ethyl-N-isoamylamino-<NUM>-methyl-<NUM>-anilinofluoran, <NUM>-N-methyl-N-cyclohexylamino-<NUM>-methyl-<NUM>-anilinofluoran, <NUM>-N,N-diethylamino-<NUM>-o-chloroanilinofluoran, rhodamine B lactam, <NUM>-methylspirodinaphtopyran, <NUM>-ethyl spirodinaphtopyran, and <NUM>-benzylspironaphtopyran.

The developer can be any of acidic substances to be used as an electron acceptor of a thermosensitive recording medium.

Examples of the developer include an inorganic substance such as activated clay and acid clay, an inorganic acid, an aromatic carboxylic acid, an anhydride or metallic salt thereof, an organic sulfonic acid, other organic acids, and an organic developer such as a phenolic compound. The phenolic compound is preferable.

Examples of the developer specifically include a phenolic compound such as bis3-allyl-<NUM>-hydroxyphenylsulfone, polyhydroxystyrene, a zinc salt of <NUM>,<NUM>-di-t-butylsalicylate, a zinc salt of <NUM>-octyl-<NUM>-methylsalicylate, phenol, <NUM>-phenylphenol, <NUM>-hydroxyacetophenone, <NUM>,<NUM>'-dihydroxydiphenyl, <NUM>,<NUM>'-methylenebis (<NUM>-chlorophenol), <NUM>,<NUM>'-methylenebis(<NUM>-methyl-<NUM>-t-butylphenol), <NUM>,<NUM>'-isopropylidenediphenol (another name: bisphenol A), <NUM>,<NUM>'-isopropylidenebis(<NUM>-chlorophenol), <NUM>,<NUM>'-isopropylidenebis(<NUM>-methylphenol), <NUM>,<NUM>'-ethylenebis(<NUM>-methylphenol), <NUM>,<NUM>'-thiobis(<NUM>-t-butyl-<NUM>-methylphenol), <NUM>,<NUM>-bis(<NUM>-hydroxyphenyl)-cyclohexane, <NUM>,<NUM>'-bis(<NUM>-hydroxyphenyl)-n-heptane, <NUM>,<NUM>'-cyclohexylidenebis(<NUM>-isopropylphenol), and <NUM>,<NUM>'-sulfonyldiphenol, a salt of the phenolic compound, anilide salicylate, a novolak-type phenolic resin, and benzyl p-hydroxybenzoate.

Example of the material of the intermediate layer <NUM> and the intermediate layer <NUM> include polypropylene (PP), polyvinyl alcohol (PVA), a styrene-butadiene copolymer (SBR), polystyrene, polyacrylic, and the like.

The protection/function layer <NUM> may be provided as needed. Specific functions of the protection/function layer <NUM> may include insertion of a forgery prevention item such as a hologram, a lenticular lens, a microarray lens, and ultraviolet excitation-type fluorescence ink, insertion of an inner protective item such as a UV cutting layer, or both of the functions. In this case, the protection/function layer <NUM> is preferably transparent, and is more preferably colorless and transparent for the purpose of visually checking recording or monochrome recording under the protection/function layer <NUM> after the recording.

Next, the following describes a laser recording device in the first embodiment. <FIG> is an overview block diagram of the laser recording device in the first embodiment.

The laser recording device <NUM> in the first embodiment includes a laser oscillator <NUM> that outputs near infrared laser light LNIR with wavelength λ, a beam expander <NUM> that expands a beam diameter of the near infrared laser light LNIR, and a first direction scanning unit <NUM> including a first motor <NUM> that drives a first direction scanning mirror <NUM> for reflecting the near infrared laser light LNIR, and drives the first direction scanning mirror <NUM> for performing scanning in a first direction with the near infrared laser light LNIR.

The laser recording device <NUM> in the first embodiment also includes a second direction scanning unit <NUM> including a second motor <NUM> that drives a second direction scanning mirror <NUM> for reflecting the near infrared laser light LNIR, and drives a second direction scanning mirror <NUM> for performing scanning in a second direction orthogonal to the first direction with the near infrared laser light LNIR, a condensing lens (Fθ lens) <NUM> that concentrates, to the recording medium <NUM>, the near infrared laser light LNIR introduced via the first direction scanning unit <NUM> and the second direction scanning unit <NUM>, and a stage <NUM> that conveys the recording medium <NUM> to be held at a given position.

The laser recording device <NUM> in the first embodiment further includes a control unit <NUM> that calculates an irradiation position and irradiation intensity of far infrared laser light LFIR and controls the entire laser recording device <NUM> based on input image data GD that has been input, an output control unit <NUM> that controls a laser output from the laser oscillator <NUM> based on a calculation result obtained by the control unit <NUM>, and an irradiation position control unit <NUM> that controls the first motor <NUM> and the second motor <NUM> based on the calculation result obtained by the control unit <NUM> and controls an irradiation position of the near infrared laser light LNIR with respect to the recording medium <NUM>.

In the configuration described above, the laser oscillator <NUM> can be a semiconductor laser, a fiber laser, a YAG laser, and a YVO<NUM> laser serving as a laser for a near infrared region.

Next, the following describes recording processing performed by the laser recording device <NUM> for the recording medium <NUM>.

<FIG> is a flowchart of processing performed by the laser recording device.

In the following, the light absorption color developing layer <NUM> is set to a black (K) color developing layer, the high-temperature thermosensitive color developing layer <NUM> is set to a yellow (Y) color developing layer, the medium-temperature thermosensitive color developing layer <NUM> is set to a magenta (M) color developing layer, and the low-temperature thermosensitive color developing layer <NUM> is set to a cyan (C) color developing layer.

First, the control unit <NUM> of the laser recording device <NUM> carries the recording medium <NUM> into a recording position via a conveying device (not illustrated) (Step S11).

Subsequently, the control unit <NUM> of the laser recording device <NUM> detects the recording medium <NUM> that has been carried in with a sensor (not illustrated) (Step S12), and fixes the recording medium <NUM> at a given carry-in position with a fixing device (not illustrated) (Step S13).

Subsequently, when the input image data GD as RGB data is input (Step S14), the control unit <NUM> of the laser recording device <NUM> analyzes the input image data GD, and converts the input image data GD into color data (CMYK data) for each pixel (Step S15).

Subsequently, the control unit <NUM> converts the color data into a laser irradiation parameter value in accordance with a combination of layers to develop a color based on the color data for each pixel (Step S16).

Specifically, the laser irradiation parameter value includes a set power value, a set scanning-speed value, a set pulse-width value, a set irradiation-repetition-number value, or a set scanning-pitch value.

Subsequently, the control unit <NUM> controls the output control unit <NUM> and the irradiation position control unit <NUM> to record an image on the full-color image region ARC to cause the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> to develop a color, using the near infrared laser light LNIR based on the laser irradiation parameter value set at Step S13 (Step S17).

The following describes color development control in the full-color image region ARC.

In the full-color image region ARC, the laser recording device <NUM> performs color development using the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM>.

As described above, the high-temperature thermosensitive color developing layer <NUM> develops a color when the temperature thereof becomes equal to or higher than the first threshold temperature T1, the medium-temperature thermosensitive color developing layer <NUM> develops a color when the temperature thereof becomes equal to or higher than the second threshold temperature T2 (< T1), and the low-temperature thermosensitive color developing layer <NUM> develops a color when the temperature thereof becomes equal to or higher than the third threshold temperature T3 (< T2 < T1).

More specifically, for example, the first threshold temperature T1 of the high-temperature thermosensitive color developing layer <NUM> is in the range of <NUM> to <NUM>, the second threshold temperature T2 of the medium-temperature thermosensitive color developing layer <NUM> is in the range of <NUM> to <NUM>, and the third threshold temperature T3 of the low-temperature thermosensitive color developing layer <NUM> is in the range of <NUM> to <NUM>. The respective thermosensitive color developing layers are set to satisfy the above ranges.

First, the following describes color development control over the high-temperature thermosensitive color developing layer <NUM> alone.

<FIG> is a diagram for explaining a relation between energy and an irradiation time of laser light in the case of causing the high-temperature thermosensitive color developing layer to develop a color.

As illustrated in <FIG>, the high-temperature thermosensitive color developing layer <NUM> develops a color in an upper right region of a corresponding color development curve CH (a color development region of the high-temperature thermosensitive color developing layer <NUM>).

The medium-temperature thermosensitive color developing layer <NUM> develops a color in an upper right region of a corresponding color development curve CM (a color development region of the medium-temperature thermosensitive color developing layer <NUM>).

The low-temperature thermosensitive color developing layer <NUM> develops a color in an upper right region of a corresponding color development curve CL (a color development region of the low-temperature thermosensitive color developing layer <NUM>).

Thus, to cause the high-temperature thermosensitive color developing layer <NUM> to develop a color, the energy and the irradiation time of the laser light may be set to fall in the color development region of the high-temperature thermosensitive color developing layer <NUM>, a non-color development region of the medium-temperature thermosensitive color developing layer <NUM>, and a non-color development region of the low-temperature thermosensitive color developing layer <NUM>, as a region ARH indicated by hatching in <FIG>.

The following describes color development control over the high-temperature thermosensitive color developing layer <NUM> in more detail.

<FIG> is an explanatory diagram of a temperature for controlling color development of the high-temperature thermosensitive color developing layer.

To cause the high-temperature thermosensitive color developing layer <NUM> to develop a color, the photothermal conversion layer <NUM> generates and transfers heat necessary for color development to the high-temperature thermosensitive color developing layer <NUM>.

To implement that process, as illustrated in <FIG>, the near infrared laser light LNIR may be emitted after setting the laser irradiation parameter value so that a temperature TMH of the high-temperature thermosensitive color developing layer <NUM> exceeds the first threshold temperature T1, a temperature TMM of the medium-temperature thermosensitive color developing layer <NUM> does not exceed the second threshold temperature T2, and a temperature TML of the low-temperature thermosensitive color developing layer <NUM> does not exceed the third threshold temperature T3 to control a temperature TMT of the photothermal conversion layer <NUM>.

The near infrared laser light LNIR then reaches the photothermal conversion layer <NUM> via the protection/function layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the binder layer <NUM>.

In this case, as illustrated in <FIG>, the laser irradiation parameter value is set for the near infrared laser light LNIR to be emitted to the photothermal conversion layer <NUM> so that a heating amount steeply increases and a heat generation time is shortened.

Thus, the photothermal conversion layer <NUM> absorbs the near infrared laser light LNIR, performs photothermal conversion, and steeply generates heat. The temperature TMT of the photothermal conversion layer <NUM> varies as illustrated in <FIG>.

Thus, the temperature of the high-temperature thermosensitive color developing layer <NUM> closer to the photothermal conversion layer <NUM> steeply increases, and exceeds the first threshold temperature T1. The high-temperature thermosensitive color developing layer <NUM> then develops a color of yellow (Y).

On the other hand, the heat is conducted from the photothermal conversion layer <NUM> to the medium-temperature thermosensitive color developing layer <NUM> via the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the intermediate layer <NUM>, and furthermore, the heat is conducted to the low-temperature thermosensitive color developing layer <NUM> via the intermediate layer <NUM>.

However, as illustrated in <FIG>, a time during which the heat is conducted is short, and an amount of heat (thermal energy) transferred to the medium-temperature thermosensitive color developing layer <NUM> and the low-temperature thermosensitive color developing layer <NUM> is small, so that an increase in the temperature TMM of the medium-temperature thermosensitive color developing layer <NUM> and the temperature TML of the low-temperature thermosensitive color developing layer <NUM> is small.

Thus, as illustrated in <FIG>, the temperature TMM of the medium-temperature thermosensitive color developing layer <NUM> does not exceed the second threshold temperature T2, and the medium-temperature thermosensitive color developing layer <NUM> does not develop a color.

Similarly, as illustrated in <FIG>, the temperature TML of the low-temperature thermosensitive color developing layer <NUM> does not exceed the third threshold temperature T3, and the low-temperature thermosensitive color developing layer <NUM> does not develop a color.

The near infrared laser light LNIR is absorbed by the photothermal conversion layer <NUM>, and does not reach the light absorption color developing layer <NUM>, so that the light absorption color developing layer <NUM> also does not develop a color.

Next, the following describes color development control over the medium-temperature thermosensitive color developing layer <NUM> alone.

<FIG> is a diagram for explaining a relation between the energy and the irradiation time of the laser light in the case of causing the medium-temperature thermosensitive color developing layer to develop a color.

As with the high-temperature thermosensitive color developing layer <NUM>, to cause the medium-temperature thermosensitive color developing layer <NUM> to develop a color, the energy and the irradiation time of the laser light may be set to fall in a color development region of the medium-temperature thermosensitive color developing layer <NUM>, a non-color development region of the high-temperature thermosensitive color developing layer <NUM>, and a non-color development region of the low-temperature thermosensitive color developing layer <NUM>, as a region ARM indicated by hatching in <FIG>.

The following describes color development control over the medium-temperature thermosensitive color developing layer <NUM> in more detail.

<FIG> is an explanatory diagram of a temperature for controlling color development of the medium-temperature thermosensitive color developing layer.

To cause the medium-temperature thermosensitive color developing layer <NUM> to develop a color, the photothermal conversion layer <NUM> generates and transfers heat required for color development to the medium-temperature thermosensitive color developing layer <NUM> via the high-temperature thermosensitive color developing layer <NUM> and the intermediate layer <NUM> without color development of the high-temperature thermosensitive color developing layer <NUM>.

To implement this process, as illustrated in <FIG>, the near infrared laser light LNIR may be emitted after setting the laser irradiation parameter value so that the temperature of the medium-temperature thermosensitive color developing layer <NUM> exceeds the second threshold temperature T2, the temperature of the high-temperature thermosensitive color developing layer <NUM> does not exceed the first threshold temperature T1, and the temperature of the low-temperature thermosensitive color developing layer <NUM> does not exceed the third threshold temperature T3 to control the temperature TMT of the photothermal conversion layer <NUM>.

In this case, the laser irradiation parameter value of the near infrared laser light LNIR to be emitted to the photothermal conversion layer <NUM> is set such that the heating amount increases more gradually and the heat generation time is prolonged, as compared with the high-temperature thermosensitive color developing layer <NUM> developing a color.

Thus, the photothermal conversion layer <NUM> absorbs the near infrared laser light LNIR, performs photothermal conversion, and gradually generates heat. The temperature TMT of the photothermal conversion layer <NUM> varies as illustrated in <FIG>.

Thus, the temperature of the high-temperature thermosensitive color developing layer <NUM> closer to the photothermal conversion layer <NUM> increases, but does not exceed the first threshold temperature T1, so that the high-temperature thermosensitive color developing layer <NUM> does not develop the color of yellow (Y).

In this case, as illustrated in <FIG>, the time during which the heat is conducted is longer and the temperature is lower than those in the case of causing the high-temperature thermosensitive color developing layer <NUM> to develop a color. However, the second threshold temperature T2 at which the medium-temperature thermosensitive color developing layer <NUM> develops a color is lower than the first threshold temperature T1, so that required energy sufficient for color development is transferred to the medium-temperature thermosensitive color developing layer <NUM>.

Thus, the temperature of the medium-temperature thermosensitive color developing layer <NUM> exceeds the second threshold temperature T2, and the medium-temperature thermosensitive color developing layer <NUM> develops a color of magenta (M).

In this case, the amount of heat (thermal energy) to be transferred is small because the low-temperature thermosensitive color developing layer <NUM> is at a position distant from the photothermal conversion layer <NUM>, so that an increase in the temperature of the low-temperature thermosensitive color developing layer <NUM> is small.

Thus, the temperature of the low-temperature thermosensitive color developing layer <NUM> does not exceed the third threshold temperature T3, and the low-temperature thermosensitive color developing layer <NUM> does not develop a color.

Next, the following describes color development control over the low-temperature thermosensitive color developing layer <NUM>.

<FIG> is a diagram for explaining a relation between the energy and the irradiation time of the laser light in the case of causing the low-temperature thermosensitive color developing layer to develop a color.

Similarly to the high-temperature thermosensitive color developing layer <NUM>, in the case of causing the low-temperature thermosensitive color developing layer <NUM> to develop a color, the energy and the irradiation time of the laser light may be set to fall in a color development region of the low-temperature thermosensitive color developing layer <NUM>, the non-color development region of the high-temperature thermosensitive color developing layer <NUM>, and the non-color development region of the medium-temperature thermosensitive color developing layer <NUM>, like a region ARL indicated by hatching in <FIG>.

The following describes color development control for the low-temperature thermosensitive color developing layer <NUM> in more detail.

<FIG> is an explanatory diagram of a temperature for controlling color development of the low-temperature thermosensitive color developing layer.

In this case, the laser irradiation parameter value is set for the near infrared laser light LNIR to be emitted to the photothermal conversion layer <NUM> so that the heating amount increases more gradually and the heat generation time is further prolonged, as compared with causing the medium-temperature thermosensitive color developing layer <NUM> to develop a color.

Thus, the photothermal conversion layer <NUM> absorbs the near infrared laser light LNIR, performs photothermal conversion, and generates heat more gradually. Thus, the temperature of the high-temperature thermosensitive color developing layer <NUM> closer to the photothermal conversion layer <NUM> does not exceed the first threshold temperature T1, and the high-temperature thermosensitive color developing layer <NUM> does not develop the color of yellow (Y).

The heat is conducted from the photothermal conversion layer <NUM> to the medium-temperature thermosensitive color developing layer <NUM> via the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the intermediate layer <NUM>.

In this case, as illustrated in <FIG>, the time during which the heat is conducted is longer than that when the medium-temperature thermosensitive color developing layer <NUM> develops a color, but the temperature is further lower than that case. Thus, the temperature of the medium-temperature thermosensitive color developing layer <NUM> does not exceed the second threshold temperature T2, and the high-temperature thermosensitive color developing layer <NUM> does not develop the color of magenta (M).

The heat is further conducted from the photothermal conversion layer <NUM> to the low-temperature thermosensitive color developing layer <NUM> via the binder layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the intermediate layer <NUM>.

In this case, the low-temperature thermosensitive color developing layer <NUM> is at a position distant from the photothermal conversion layer <NUM>. However, as illustrated in <FIG>, the time during which the heat is conducted is longer and the temperature is lower than those in the case of causing the medium-temperature thermosensitive color developing layer <NUM> to develop a color, but the third threshold temperature T3 at which the low-temperature thermosensitive color developing layer <NUM> develops a color is further lower, so that required energy sufficient for color development is transferred to the low-temperature thermosensitive color developing layer <NUM>.

Thus, the temperature of the low-temperature thermosensitive color developing layer <NUM> exceeds the third threshold temperature T3, and the low-temperature thermosensitive color developing layer <NUM> develops a color of cyan (C) in the full-color image region ARC.

The above has described the examples of causing each of the high-temperature thermosensitive color developing layer <NUM>, medium-temperature thermosensitive color developing layer <NUM>, and low-temperature thermosensitive color developing layer <NUM> to develop a color. Alternatively, two or three colors can be developed at the same time.

The following describes an example of developing a plurality of colors.

<FIG> is a diagram for explaining a relation between the energy and the irradiation time of the laser light in the case of causing the high-temperature thermosensitive color developing layer and the medium-temperature thermosensitive color developing layer to develop a color in parallel.

To cause the high-temperature thermosensitive color developing layer <NUM> and the medium-temperature thermosensitive color developing layer <NUM> to develop a color in parallel, the energy and the irradiation time of the laser light may be set in a region of the color development region of the high-temperature thermosensitive color developing layer <NUM>, the color development region of the medium-temperature thermosensitive color developing layer <NUM>, and the non-color development region of the low-temperature thermosensitive color developing layer <NUM>, like a region ARHM indicated by hatching in <FIG>.

By performing such control, the color of yellow (Y) corresponding to the high-temperature thermosensitive color developing layer <NUM> is developed, and the color of magenta (M) corresponding to the medium-temperature thermosensitive color developing layer <NUM> is developed. As a result, a color of red is developed in the full-color image region ARC.

<FIG> is a diagram for explaining a relation between the energy and the irradiation time of the laser light in the case of causing the medium-temperature thermosensitive color developing layer and the low-temperature thermosensitive color developing layer to develop a color in parallel.

In the case of causing the medium-temperature thermosensitive color developing layer <NUM> and the low-temperature thermosensitive color developing layer <NUM> to develop a color in parallel, the energy and the irradiation time of the laser light may be set to fall in the color development region of the medium-temperature thermosensitive color developing layer <NUM>, the color development region of the low-temperature thermosensitive color developing layer <NUM>, and the non-color development region of the high-temperature thermosensitive color developing layer <NUM>, like a region ARML indicated by hatching in <FIG>.

By controlling the energy and the irradiation time of the laser light in this way, the color of magenta (M) corresponding to the medium-temperature thermosensitive color developing layer <NUM> is developed, and the color of cyan (C) corresponding to the low-temperature thermosensitive color developing layer <NUM> is developed. As a result, a color of blue is developed in the full-color image region ARC.

<FIG> is a diagram for explaining a relation between the energy and the irradiation time of the laser light in the case of causing the high-temperature thermosensitive color developing layer, the medium-temperature thermosensitive color developing layer, and the low-temperature thermosensitive color developing layer to develop a color in parallel.

To cause the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> to develop a color in parallel, the energy and the irradiation time of the laser light may be set to fall in the color development region of the high-temperature thermosensitive color developing layer <NUM>, the color development region of the medium-temperature thermosensitive color developing layer <NUM>, and the color development region of the low-temperature thermosensitive color developing layer <NUM>, as a region ARHML indicated by hatching in <FIG>.

By performing such control, the color of yellow (Y) corresponding to the high-temperature thermosensitive color developing layer <NUM>, the color of magenta (M) corresponding to the medium-temperature thermosensitive color developing layer <NUM>, and the color of cyan (C) corresponding to the low-temperature thermosensitive color developing layer <NUM> are developed. As a result, a color of black (dark gray) is developed in the full-color image region ARC.

Next, the following describes color development control in the monochrome image region ARM.

When recording in the full-color image region ARC ends, the control unit <NUM> controls the output control unit <NUM> and the irradiation position control unit <NUM>, and performs image recording for the monochrome image region ARM to cause the light absorption color developing layer <NUM> to develop a color using the near infrared laser light LNIR based on the laser irradiation parameter value set at Step S13 (Step S18).

In this case, the near infrared laser light LNIR reaches the light absorption color developing layer <NUM> via the protection/function layer <NUM>, the low-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, the intermediate layer <NUM>, the high-temperature thermosensitive color developing layer <NUM>, and the binder layer <NUM>, not via the photothermal conversion layer <NUM>, that is, without being absorbed by the photothermal conversion layer <NUM>.

As a result, the pigment particles contained in the light absorption color developing layer <NUM> absorb the near infrared laser light LNIR as light and are carbonized to irreversibly develop a color of black.

The color of black developed by the light absorption color developing layer <NUM> has a higher contrast than that of the color of black (dark gray) developed in the full-color image region ARC, and can display an image such as a character more clearly.

Subsequently, the control unit <NUM> of the laser recording device <NUM> releases fixation of the recording medium <NUM> by the fixing device (not illustrated) (Step S19), carries out the recording medium <NUM> to a given carry-out position via the conveying device (not illustrated), and ends the processing (Step S20).

As described above, according to the first embodiment, full-color/monochrome image recording can be performed by using a laser light source of a single wavelength. Additionally, according to the first embodiment, a postscript cannot be added using a thermal head, for example, so that the recording medium can be prevented from being altered, and security can be improved.

Next, the following describes the recording medium according to a second embodiment.

<FIG> is a cross-sectional view of a configuration example of the recording medium according to the second embodiment.

A recording medium 10A in the second embodiment is different from the recording medium <NUM> in the first embodiment in that the photothermal conversion layer <NUM> is located closer to the high-temperature thermosensitive color developing layer <NUM>, not to the light absorption color developing layer <NUM>.

With this configuration, in addition to the effect of the first embodiment, a heat transfer loss due to the binder layer <NUM> can be reduced in transferring the heat generated in the photothermal conversion layer <NUM> to the high-temperature thermosensitive color developing layer <NUM>, and energy can be further saved.

Next, the following describes the recording medium according to a third embodiment.

<FIG> is a cross-sectional view of a configuration example of the recording medium according to the third embodiment.

A recording medium 10B in the third embodiment is different from the recording medium <NUM> in the first embodiment in that the photothermal conversion layer 13A is closer to the intermediate layer <NUM> of the high-temperature thermosensitive color developing layer <NUM>.

With this configuration, in addition to the effect of the first embodiment, in transferring the heat generated in the photothermal conversion layer 13A to the high-temperature thermosensitive color developing layer <NUM>, the heat transfer loss due to the binder layer <NUM> can be reduced, and a transmission loss of the near infrared laser light LNIR for the photothermal conversion layer 13A can also be reduced. Thus, further energy saving can be achieved.

Next, the following describes the recording medium according to a modification of the third embodiment.

<FIG> is a cross-sectional view of a configuration example of the recording medium according to the modification of the third embodiment.

A recording medium 10C according to the modification of the third embodiment is different from the recording medium 10B in the third embodiment in that the photothermal conversion layer <NUM> is separated from the high-temperature thermosensitive color developing layer <NUM> by a given distance in the intermediate layer <NUM>.

With this configuration, the same effect as that of the third embodiment can be obtained.

Next, the following describes the recording medium according to a fourth embodiment.

<FIG> is a cross-sectional view of a configuration example of the recording medium according to the fourth embodiment.

In <FIG>, the same or like elements as those in the first embodiment in <FIG> are denoted by the same reference numerals.

A recording medium 10D according to the fourth embodiment, as illustrated in <FIG>, includes the light absorption color developing layer <NUM> serving as the first color developing layer, the binder layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM> serving as the second color developing layer, the intermediate layer <NUM>, the high-temperature thermosensitive color developing layer <NUM> serving as the second color developing layer, the photothermal conversion layer <NUM> closer to the high-temperature thermosensitive color developing layer <NUM> in the intermediate layer <NUM>, the intermediate layer <NUM>, the low-temperature thermosensitive color developing layer <NUM> serving as the second color developing layer, and the protection/function layer <NUM>, laminated on the base material <NUM> in this order.

Also in this case, each of the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> functions as a thermosensitive recording layer on which an image is recorded.

In the fourth embodiment, the thickness of the intermediate layer <NUM> is set based on an optimum transfer amount of thermal energy to the medium-temperature thermosensitive color developing layer <NUM>, and the thickness of the intermediate layer <NUM> is set based on an optimum transfer amount of thermal energy to the low-temperature thermosensitive color developing layer <NUM> via the high-temperature thermosensitive color developing layer <NUM>.

According to the fourth embodiment, in addition to the effect of the first embodiment, transfer efficiency of thermal energy can be further improved, and energy can be saved.

<FIG> illustrate a recording medium according to a fifth embodiment. <FIG> is a plan view, and <FIG> is an A-A cross-sectional view of <FIG>.

In the embodiments described above, the photothermal conversion layer <NUM> for forming the full-color image region ARC has a quadrangular shape (in <FIG>, a rectangular shape) in a plan view as a full-color image region ARC1, but the embodiment is not limited thereto. The photothermal conversion layer <NUM> can have an optional shape as a full-color image region ARC2 in a recording medium 10E according to the fifth embodiment illustrated in <FIG>.

The optional shape can be a desired shape such as a circular shape, an elliptic shape, a polygonal shape, a star shape, an animal shape, a map shape, and a human figure shape.

In this case, in the recording medium 10E, the photothermal conversion layer <NUM> is preferably formed by a printing system. As the printing system, a general printing system can be used such as ink-jet printing, offset printing, relief printing, screen printing, and intaglio printing.

According to the fifth embodiment, authenticity determination can be facilitated by varying the shape of the full-color image region ARC2 for each publication date of the recording medium.

<FIG> is an explanatory diagram of the recording medium according to a sixth embodiment.

A recording medium 10F in the sixth embodiment is different from the embodiments described above in additionally including a lenticular lens <NUM> on the protection/function layer <NUM> or integrally with the protection/function layer <NUM>.

With this configuration, by performing image formation while varying an irradiation direction of the near infrared laser light LNIR at the time of forming an image on the recording medium 10F, an image to be displayed can be switched depending on a visual recognition angle.

In the example of <FIG>, the lenticular lens <NUM> is placed in a region corresponding to the monochrome image region ARM including no photothermal conversion layer <NUM>, so that a recordable image is a monochrome image.

<FIG> is an explanatory diagram of a modification of the recording medium in the sixth embodiment.

As illustrated in <FIG>, the recording medium can be configured to form a full-color image by arranging the photothermal conversion layer <NUM> in a recordable region of the lenticular lens <NUM>.

According to the sixth embodiment, functionality of the recording medium can be improved.

Additionally, image formation is required to be performed while varying the irradiation direction of the near infrared laser light LNIR depending on an image to be visually recognized, so that the recording medium is difficult to be forged, and authenticity determination for the recording medium can be facilitated.

<FIG> is a cross-sectional view of the recording medium according to a seventh embodiment.

A recording medium <NUM> in the seventh embodiment is different from the embodiments described above in additionally including a transparent base material <NUM>. The transparent base material <NUM> is part of the base material <NUM> and formed of a transparent material.

With this configuration, it is possible to facilitate authenticity determination by determining whether an image formed on the recording medium <NUM> is the same as that on a proper recording medium from the base material <NUM>.

<FIG> is an explanatory diagram of a modification of the recording medium in the seventh embodiment.

The recording medium <NUM> according to the modification of the seventh embodiment is different from that in the seventh embodiment illustrated in <FIG> in including the lenticular lens <NUM> on the protection/function layer <NUM> or integrally with the protection/function layer <NUM>.

With this configuration, by performing image formation while varying the irradiation direction of the near infrared laser light LNIR at the time of forming an image on the recording medium 10F, an image to be displayed can be switched depending on the visual recognition angle.

In the example of <FIG>, the photothermal conversion layer <NUM> is located in the recordable region of the lenticular lens <NUM>.

Thus, a dot pattern of a full-color image that is formed via the lenticular lens <NUM> is a dot pattern specific to a formed image, so that authenticity determination can be easily performed, and a forgery or an imitation can be detected to be excluded.

<FIG> is a cross-sectional view of the recording medium according to an eighth embodiment.

A recording medium <NUM> in the eighth embodiment is different from the embodiments described above in including the high-temperature thermosensitive color developing layer <NUM> and the medium-temperature thermosensitive color developing layer <NUM> as thermosensitive color developing layers and excluding the low-temperature thermosensitive color developing layer <NUM>.

Because of this, a recording medium that cannot display in full color but can display a multicolored image can be provided at low cost.

<FIG> illustrates the example of no low-temperature thermosensitive color developing layer <NUM>. Alternatively, the recording medium can be configured to include the low-temperature thermosensitive color developing layer <NUM> and any one of the high-temperature thermosensitive color developing layer <NUM> and the medium-temperature thermosensitive color developing layer <NUM>.

<FIG> is a cross-sectional view of the recording medium according to a ninth embodiment.

A recording medium <NUM> in the ninth embodiment is different from the above embodiments except the eighth embodiment in including only the high-temperature thermosensitive color developing layer <NUM> as the thermosensitive color developing layer, and excluding the medium-temperature thermosensitive color developing layer <NUM> and the low-temperature thermosensitive color developing layer <NUM>.

Due to this, a recording medium that can display a two-color image can be provided at low cost although it cannot display in full color.

<FIG> illustrates the example of the recording medium without the medium-temperature thermosensitive color developing layer <NUM> and the low-temperature thermosensitive color developing layer <NUM>. Alternatively, the recording medium can be configured to include only one of the high-temperature thermosensitive color developing layer <NUM>, the medium-temperature thermosensitive color developing layer <NUM>, and the low-temperature thermosensitive color developing layer <NUM> without the other two.

A recording medium 10J in the ninth embodiment is different from the embodiments described above in that a low-temperature thermosensitive color developing layer 19A is formed only in the area of the full-color image region ARC, while the thermosensitive color developing layer is formed on the entire surface of the recording medium in a plan view in the embodiments described above.

According to the tenth embodiment, only a desired region of the recording medium can be set to the full-color image region, so that forgery using another recording medium can be prevented by causing a proper full-color image region to be different for each type of the recording medium.

In the laser recording device <NUM> according to the first embodiment described above, the light absorption color developing layer <NUM> cannot develop a color in the region of the photothermal conversion layer <NUM>, that is, in the full-color image region ARC. However, a laser recording device 30A according to an eleventh embodiment causes the light absorption color developing layer <NUM> to develop a color in at least part of the full-color image region ARC of the photothermal conversion layer <NUM>.

<FIG> is an overview block diagram of the laser recording device according to the eleventh embodiment.

The laser recording device 30A in the eleventh embodiment is different from the laser recording device in the first embodiment in additionally including an incident-angle changing device <NUM>. The incident-angle changing device <NUM> can effectively change an incident angle at the time when the near infrared laser light LNIR enter the light absorption color developing layer <NUM> located on the back surface of the photothermal conversion layer <NUM> by inclining, in an optional direction, the stage <NUM> that conveys and holds the recording medium <NUM> at a given position under control of the irradiation position control unit <NUM>.

<FIG> is an explanatory diagram of an irradiation state with no inclination of the recording medium.

To form an image in a region corresponding to the monochrome image region ARM including no photothermal conversion layer <NUM> as illustrated in the center of <FIG>, and in a region corresponding to the full-color image region ARC including the photothermal conversion layer <NUM> as illustrated in the right side of <FIG>, the near infrared laser light LNIR can vertically enter the recording surface of the recording medium 10C for normal recording while maintaining a horizontal state of the recording medium (in <FIG>, the recording medium 10C) not inclined by the incident-angle changing device <NUM>.

<FIG> is an explanatory diagram of an irradiation state while the recording medium is inclined.

In <FIG>, the recording medium 10C is inclined by the incident-angle changing device <NUM> in practice, but the recording medium 10C is illustrated in a horizontal state to be easily understood.

That is, with the recording medium 10C inclined by the incident-angle changing device <NUM>, the near infrared laser light LNIR effectively and obliquely enters to record information on the light absorption color developing layer <NUM> located on the back side of the region corresponding to the full-color image region ARC including the photothermal conversion layer <NUM>.

In this manner, with the laser recording device 30A in the eleventh embodiment, images can be formed by causing the light absorption color developing layer <NUM> to develop a color in at least part of the full-color image region ARC including the photothermal conversion layer <NUM>, which makes it difficult to alter and forge the recording.

In the embodiments described above, the recording medium is a single item. A twelfth embodiment describes a card-like recording medium including the recording medium and a carrier that carries the recording medium, i.e., a member having a card shape such as paper, plastic, metal, and ceramics.

In the following, for better understanding, the recording medium <NUM> is exemplified as the recording medium held by the carrier.

<FIG> is an explanatory diagram of the card-like recording medium according to the twelfth embodiment.

(a) in <FIG> is a cross-sectional view, and (b) in <FIG> is a plan view.

(a) in <FIG> is a cross-sectional view of a dashed line area of <FIG>.

As illustrated in (a) in <FIG>, the recording medium <NUM> is carried by a carrier <NUM> to form a card-like recording medium <NUM>.

In this way, according to the twelfth embodiment, the recording medium <NUM> is carried by the carrier <NUM>, so that ruggedness is improved, and the recording medium <NUM> can be kept having high reliability for a long period.

<FIG> is an explanatory diagram of the card-like recording medium according to a first modification of the twelfth embodiment.

(a) in <FIG> is a cross-sectional view of a dashed line area of (b) in <FIG>.

A card-like recording medium 71A according to the first modification of the twelfth embodiment is different from the twelfth embodiment in that two recording mediums <NUM> are carried by both surfaces of the carrier <NUM>, respectively.

With this configuration, in addition to the effect of the twelfth embodiment, recording can be performed on both surfaces of the card-like recording medium 71A. Furthermore, strength of the card-like recording medium 71A can be improved, and the card-like recording medium 71A can be prevented from being deformed.

<FIG> is an explanatory diagram of the card-like recording medium according to a second modification of the twelfth embodiment.

(a) in <FIG> is a first cross-sectional view, (b) in <FIG> is a plan view, and <FIG> is a second cross-sectional view.

(a) in <FIG> is a cross-sectional view of a dashed line x of (b) in <FIG>, and FIG. 33C is a cross-sectional view of a dashed line area y of (b) in <FIG>.

A card-like recording medium 71B according to the second modification of the twelfth embodiment is different from the twelfth embodiment in that the recording medium <NUM> is carried by two carriers 70A and 70B holding a hinge <NUM> therebetween.

In this case, in addition to the effect of the twelfth embodiment, by filing one or a plurality of card-like recording mediums 71B to a booklet at the hinge <NUM>, the card-like recording mediums 71B are difficult to be removed from the booklet. Thus, alteration and the like can be further prevented, and security can be improved.

<FIG> is an explanatory diagram of the card-like recording medium according to a third modification of the twelfth embodiment.

A card-like recording medium 71C according to a third modification of the twelfth embodiment is different from the twelfth embodiment in that the recording medium <NUM> is held by the two carriers 70A and 70B placing the hinge <NUM> and a card core <NUM> as an IC card in-between.

In this case, in addition to the effect of the twelfth embodiment, a high-functionality card-like recording medium can be obtained by integrating various functions into the card core <NUM>, and security can be further improved by digitizing and encoding recording data.

<FIG> is an explanatory diagram of the card-like recording medium according to a fourth modification of the twelfth embodiment.

A card-like recording medium 71D according to the fourth modification of the twelfth embodiment is different from the third modification of the twelfth embodiment in <FIG> in including a short hinge 73A in place of the hinge <NUM>.

According to the fourth modification of the twelfth embodiment, in addition to the effect of the third modification of the twelfth embodiment, an increase in the thickness of the card-like recording medium can be suppressed, and the number of mediums to be filed can be increased.

The above embodiments have described the example of two to four color developing layers. However, the embodiments can also be applied to five or more color developing layers.

The above embodiments have described four-color (CMYK) recording as an example. However, the embodiments can also be applied to seven-color recording on seven-color developing layers including cyan (C), magenta (M), yellow (Y), red (R), green (G), blue (B), and black (K), for example.

The above embodiments have described the example of the near infrared laser light as the laser light. However, the laser light can be near UV laser light and far UV laser light depending on an absorption wavelength of the photothermal conversion layer.

The above embodiments have described the example of the control unit <NUM>, the output control unit <NUM>, and the irradiation position control unit <NUM> as independent elements. However, the control unit <NUM>, the output control unit <NUM>, and the irradiation position control unit <NUM> may be configured as a computer including a MPU, a ROM, and a RAM to execute their functions by a computer program via various interfaces.

In this case, the computer program executed by the computer may be recorded and provided in an installable or executable file format on a computer-readable recording medium such as a semiconductor recording device such as a CD-ROM, a digital versatile disc (DVD), and a USB memory.

The computer program executed by the computer may be stored in the computer connected to a network such as the Internet and provided by being downloaded via the network. Furthermore, the computer program executed by the control unit <NUM> may be provided or distributed via a network such as the Internet.

Claim 1:
A recording medium (<NUM>, 10A, 10B, 10C, 10D, 10E, 10F, <NUM>, <NUM>, 10I, 10J) comprising:
a base material (<NUM>);
a first color developing layer (<NUM>) that is laminated on the base material (<NUM>), and absorbs near infrared laser light (LNIR) having a given wavelength to develop a color;
one or more photothermal conversion layers (<NUM>) that are laminated closer to an incident side of the near infrared laser light (LNIR) than the first color developing layer (<NUM>), transmit visible light, and absorb the near infrared laser light (LNIR) for photothermal conversion;
a second color developing layer (<NUM>, <NUM>, <NUM>) that is laminated closer to the incident side of the near infrared laser light (LNIR) than the first color developing layer (<NUM>), transmits visible light and the near infrared laser light (LNIR), and develops a color by heat converted by the one or more photothermal conversion layers (<NUM>), and
a binder layer (<NUM>) for holding the first color developing layer (<NUM>), the photothermal conversion layers (<NUM>) and the second color developing layer (<NUM>, <NUM>, <NUM>) at given positions while binding the first color developing layer (<NUM>) and the second color developing layer (<NUM>, <NUM>, <NUM>).