JP2006035683A - Rewriting method of reversible thermal recording medium and equipment for executing the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rewriting method of a reversible thermal recording medium which enables rewriting in an excellent state free from the stain of a printing head or the like occurring on the occasion of rewriting and moreover wherein rewriting is performed by overwriting by only one scanning with one laser light, in thermal recording using the reversible thermal recording medium. <P>SOLUTION: In the rewriting method of the reversible thermal recording medium, an image is rewritten by changing a spot diameter of the laser light which is condensed on the surface of the reversible thermal recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rewriting method for a reversible thermosensitive recording medium and an apparatus for carrying out the method, and more particularly to rewriting an image by changing an irradiation method such as laser light.

  Conventional hard copy forms an image by attaching and fixing a colorant such as ink or toner, or a thermal recording layer is provided on a substrate such as paper, like thermal recording paper, and energy is applied to this. A visible image was formed to form a permanent image. However, recently, information output from copiers and the like has rapidly increased the consumption of recording media, causing social problems such as natural destruction. In order to solve this problem, a recording material that can erase an image and can be used repeatedly has attracted attention.

  For example, a recording medium that can reversibly form two states of transparency and white turbidity using a light scattering change of a polymer film in which organic low-molecular crystal particles are dispersed is disclosed (for example, see Patent Document 1). This recording medium has already been put into practical use as a content display section of a magnetic card. However, since the displayed image is white printed on a light-reflective background such as an aluminum vapor deposition film, it is not suitable as a normal hard copy.

  In addition, a reversible thermosensitive recording medium has been proposed which can form a color printed image reversibly on a white background using a leuco dye capable of developing and decoloring as a thermosensitive recording layer (see, for example, Patent Document 2). . This reversible thermosensitive recording medium has the same visibility as a conventional hard copy of black characters on a white background, and can rewrite an image with good contrast over and over again by applying heat. . The reversible thermosensitive recording medium can be erased by heating to a specific temperature or higher to form a printed image and heating to a second specific temperature slightly lower than this temperature.

  In erasing the reversible thermosensitive recording medium of Patent Document 2, the method using a heat roller is superior in that the reversible thermosensitive recording medium can be efficiently heated and the processing speed is faster than hot stamping. . However, since it takes time to heat up to the target erasing temperature, there is a problem that it takes a long time to start up the machine.

  Further, a method using a thermal head for printing on a reversible thermosensitive recording medium has been widely studied because it has a relatively simple structure and can be manufactured at low cost. However, it has drawbacks that it is difficult to achieve high resolution due to the processability of the heating element, and that maintenance is required for thermal head wear and contamination caused by contact with the thermal head.

  As a means to remedy such problems, laser light has been proposed as a method for rewriting a reversible thermosensitive recording medium, and laser light comprising a plurality of laser light beams that can be set at a writing temperature and an erasing temperature. Has been proposed (see, for example, Patent Document 3). However, although this method enables rewriting of recorded images (erasing and printing of images) with a single scan, it requires a plurality of laser beam irradiation units, which causes problems such as an increase in the size and cost of the apparatus. have.

As an erasing method, there has been proposed a method of performing writing with laser light after erasing a specific range by irradiating flash light. However, there are problems such as large power consumption and difficulty in partial rewriting (see, for example, Patent Document 4).
JP 55-154198 A JP-A-5-124360 Japanese Patent Laid-Open No. 7-186445 JP-A-8-267997

  The present invention has been made in consideration of the above-described circumstances, and can be rewritten in a good state without any contamination of the print head that occurs at the time of rewriting. Further, it is possible to scan only one laser beam once. An object of the present invention is to provide a rewriting method for a reversible thermosensitive recording medium which is overwritten and rewritten.

  In order to solve the above problems, the invention described in claim 1 is characterized in that the image is rewritten by changing the spot diameter of the laser beam condensed on the surface of the reversible thermosensitive recording medium.

  According to a second aspect of the present invention, in the first aspect, the laser beam on the surface of the reversible thermosensitive recording medium is condensed to form an image, and defocused to erase the image.

  According to a third aspect of the present invention, in the first or second aspect, the reversible thermosensitive recording medium is rewritten by relatively changing the positions of the lens for condensing the laser light and the laser light irradiation section. And

  According to a fourth aspect of the present invention, there is provided the reversible thermosensitive recording according to any one of the first to third aspects, wherein the positions of the lens for condensing the laser beam and the reversible thermosensitive recording medium are relatively changed. It is characterized by rewriting the medium.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a mirror is provided between the lens and the reversible thermosensitive recording medium, and the positions of the mirror and the condenser lens are relative to each other. It is characterized by rewriting the reversible thermosensitive recording medium.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a mirror is provided between the lens and the reversible thermosensitive recording medium, and the position of the mirror and the reversible thermosensitive recording medium. The reversible thermosensitive recording medium is rewritten by relatively changing the above.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a mirror is provided between the lens and the reversible thermosensitive recording medium, and the installation angle of the mirror is made variable to make the reversible feel. The thermal recording medium is rewritten.

  The invention according to claim 8 is characterized in that, in any one of claims 1 to 7, the reversible thermosensitive recording medium comprises an electron donating color developing compound and an electron accepting compound. .

  The invention according to claim 9 is characterized in that, in claim 8, the electron-accepting compound is a phenol compound having a hydrocarbon group having 8 or more carbon atoms.

  A tenth aspect of the present invention is an apparatus for carrying out the rewriting method for a reversible thermosensitive recording medium according to any one of the first to seventh aspects.

  According to the present invention, in the reversible thermosensitive recording medium rewriting method, the reversible thermosensitive recording is characterized in that the image is rewritten by changing the spot diameter of the laser beam condensed on the surface of the reversible thermosensitive recording medium. The rewriting method of the medium allows rewriting in a good state with no contamination of the print head that occurs during rewriting, and reversible thermosensitive data that is overwritten and rewritten by scanning one laser beam once. It is possible to provide a recording medium rewriting method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of a reversible thermosensitive recording medium that can be used in the method of the present invention. Here, the reversible thermosensitive recording medium can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. The reversible thermosensitive recording medium may be provided with an intermediate layer, a back layer, an under layer, a protective layer, etc. as necessary.

  In the reversible thermosensitive recording medium 100, a photothermal conversion layer 2, a reversible thermosensitive recording layer 3, and a protective layer 4 are sequentially laminated on the upper surface of the support 1. The support 1 is made of a resin such as paper, synthetic paper, or PET (polyethylene terephthalate). The reversible thermosensitive recording layer 3 described later has a thickness of 8 to 9 μm, and the photothermal conversion layer 2 and the protective layer 4 each have a thickness of about 2 μm.

  The photothermal conversion layer 2 is a layer that develops or decolors the reversible thermosensitive recording layer 3 with heat generated by absorbing the laser beam, and a dye having a large absorption system at the laser beam wavelength generally used is used as a resin. Those dispersed or dissolved therein are used. For example, when using a semiconductor laser, a polymethine dye such as cyanine, a phthalocyanine dye such as copper phthalocyanine, a naphthalocyanine dye, a dithiol metal salt dye, a naphthoquinone dye, an anthraquinone dye, or a triphenylmethane dye The near-infrared absorbing pigment such as acrylic resin, polyester resin, polycarbonate resin, vinyl chloride / vinyl acetate resin or the like, or dispersed or dissolved in a thermosetting resin having a crosslinked structure is used.

  The reversible thermosensitive recording layer 3 is formed by dispersing a leuco dye and a developer in a resin binder. The leuco dye used for the reversible thermosensitive recording layer 3 is a known dye precursor such as a phthalide compound, an azaphthalide compound, a fluorane compound, a phenothiazine compound, a leucooramine compound, No. 124360, Japanese Patent Laid-Open No. 6-210954, Japanese Patent Laid-Open No. 10-230680, and the like.

  Examples of leuco dyes widely used are those described in the above-mentioned patent publications. For example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di ( n-butylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) ) Fluorane, 2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane, 2 -Anilino-3-methyl-6- (N-sec-butyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) ) Fluorane, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane 2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylamino) Phenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-octyl-2- Methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide or the like is used alone or in combination.

  Further, the developer used for the reversible thermosensitive recording layer 4 is a compound having a phenolic hydroxyl group or a carboxylic acid and an amino group described in JP-A-5-177931, or preferably JP-A-5-124360. Structures having the ability to develop leuco dyes in the molecules described in the publications such as phenolic hydroxyl groups, carboxylic acid groups, phosphonic acid groups, and structures that control the cohesion between molecules, such as long A compound having a structure in which chain hydrocarbon groups are linked is used. As a particularly preferred example, a compound having a hydrocarbon group having 8 or more carbon atoms is used, and the structure thereof is shown by the following general formula (1).

In the formula, X ₁ represents a divalent group containing a hetero atom or a direct bond, and X ₂ represents a divalent group containing a hetero atom. R ₁ represents a divalent hydrocarbon group, and R ₂ represents a hydrocarbon group having 1 to 22 carbon atoms. P represents an integer of 0 to 4, and R ₁ and X ₂ repeated when p is 2 to 4 may be the same or different. Q represents 1 to 3;

Specifically, R ₁ and R ₂ represent an optionally substituted hydrocarbon group, which may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and is composed of both of them. It may be a hydrocarbon group. The aliphatic hydrocarbon group may be linear or branched and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen, and an alkoxy group. R ₁ may be a direct bond.

Further, when the sum of the carbon number of R ₁ and R ₂ is 7 or less, the stability of color development and the decoloring property are lowered. Therefore, the carbon number is preferably 8 or more, more preferably 11 or more. X ₁ and X ₂ each represents a divalent group containing a hetero atom, and preferably represents a divalent group having at least one group represented by the following general formula (2).

  Specific examples thereof include the following.

  Specific examples of the phenol compound in the present invention are listed below, but the present invention is not limited thereto. Moreover, a phenol compound can also be used individually or in mixture.

  Etc.

  The reversible thermosensitive recording medium used in the recording apparatus of the present invention may be formed on a support by dispersing the above leuco dye and developer together with a binder resin. For example, as described in JP-A-10-230680 A recording medium may be prepared. Further, the protective layer 4 is composed of a thermosetting polymer or an ultraviolet curable polymer.

  The reversible thermosensitive recording medium used in the recording apparatus of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. The basic coloring / decoloring phenomenon of the composition comprising the color former and developer used in the present invention will be described. FIG. 2 shows the relationship between the color density of this recording medium and the temperature. When the temperature of the recording medium initially in the decolored state (A) is raised, color development occurs at the temperature T1 at which melting starts, and the molten color state (B) is obtained. When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a solid color state (C) is obtained. Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, the color disappears during the temperature decrease, and the same color disappearance state (A) or rapid color development state (C ) A relatively low concentration state is formed.

  On the other hand, when the temperature of the rapid color development state (C) is raised again, decoloration occurs at a temperature T2 lower than the color development temperature (D to E), and when the temperature is lowered from here, the same color disappearance state (A) is restored. The actual color developing temperature and color erasing temperature vary depending on the combination of the developer and color former used, and can be selected according to the purpose. Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.

  In this recording medium, the colored state (C) obtained by rapid cooling from the molten state is a state in which the developer and the color former are mixed in a state where they can be contacted with each other, and this forms a solid state. There are many. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of this aggregated structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the color former and the developer are separated and stabilized by aggregation or crystallization. Conceivable. In many cases, in the present invention, more complete color erasure occurs due to phase separation of the two and crystallization of the developer. In both the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

  In the formation of the color image of the present invention, the light-to-heat conversion layer generates heat by the condensed laser light, and the leuco dye and the developer are heated to a temperature at which they are once melted and mixed, and then rapidly cooled. Further, decoloring is performed by defocusing the laser beam more than at the time of recording, thereby suppressing the heat generation of the amount of the photothermal conversion agent and heating the inside of the recording layer to a temperature slightly lower than the coloring temperature.

  By continuously changing the condensing size of this laser beam, the image is recorded by condensing the laser beam in accordance with the information of the recorded image, and the background is defocused than the recording unit. By setting the erase temperature to be overwritten, overwrite rewriting becomes possible.

  As the laser light of the laser light irradiation section used in the present invention, an expected laser such as an Ar ion laser or a He-Ne laser, a solid state laser such as an Nd: YAG laser, a semiconductor laser composed of GaAs, or the like may be used. it can.

  A convex lens, a conical jet lens, a rod lens, or the like is used as a lens that collects the light emitted from the laser light irradiation unit. The laser beam condensed by the lens has an arbitrary spot diameter on the surface of the reversible thermosensitive recording medium. At the time of image recording, by condensing the light to a smaller spot diameter, the recording layer is heated to a high temperature by the photothermal conversion layer to form a color image.

  At this time, the condition of the spot diameter necessary for raising the temperature to the color development start temperature varies depending on the output of the laser and the characteristics of the reversible thermosensitive recording medium. As the spot diameter is reduced, the recording layer is heated to a higher temperature, so that fine colored dots can be formed at a higher density. On the other hand, a relatively large dot can be formed by slightly increasing the aperture of the spot diameter.

  Further, by relatively increasing the spot diameter of the laser beam on the surface of the reversible thermosensitive recording medium, the temperature rise of the recording layer becomes gentle and heating under a decoloring temperature condition in a wide range is possible. Since the spot diameter of the erasing condition varies depending on the laser output and the characteristics of the reversible thermosensitive recording medium as in the case of the above printing, an optimum value may be taken.

  The ratio of the spot diameter at the time of printing and the spot diameter at the time of erasing irradiated to the reversible thermosensitive reversible thermosensitive recording medium is preferably from 1: 1.1 to 1:10, particularly from 1: 1.2 to 1: 2. Preferably used.

FIGS. 3A, 3B and 3C show an embodiment of the rewriting method of the present invention.
The laser light emitted from the laser light irradiation unit 11 is condensed on the reversible thermosensitive recording medium 100 by the lens 12. The recording of the image portion is performed by condensing the laser beam on the surface of the reversible thermosensitive recording medium 100 as shown in FIG. Next, as shown in FIG. 3B or FIG. 3C, the distance L1 between the laser beam irradiation unit 11 and the lens 12 or the distance L2 between the lens and the reversible thermosensitive recording medium 100 is changed on the background portion. By making the laser beam focused on the thermal recording medium 100 relatively larger than that during image recording, the reversible thermosensitive recording medium 100 is heated to the erasing temperature.

  FIG. 4 also shows an embodiment of the rewriting method of the present invention. Laser light emitted from the laser light irradiation unit 11 is collected by the lens 12, reflected by the mirror 13, and collected on the reversible thermosensitive recording medium 100. The recording of the image portion is performed by condensing the laser beam on the surface of the reversible thermosensitive recording medium 100 as shown in FIG. Next, the laser beam focused on the reversible thermosensitive recording medium 100 is made relatively larger than that at the time of image recording by changing the mirror angle θ as shown in FIG. Thus, the reversible thermosensitive recording medium 100 is heated to the erasing temperature.

  FIG. 5 shows a reversible thermosensitive recording medium at the time of rewriting according to the present invention. Black circles in the figure indicate the image recording portion, and white circles indicated by broken lines indicate the background portion after rewriting heated to the erasing temperature.

It is sectional drawing which shows the structure of the reversible thermosensitive recording medium used by this invention. It is explanatory drawing of the color development / decoloring characteristic of the reversible thermosensitive recording medium for this invention. FIG. 4 is an explanatory diagram of a state of focusing on the recording medium surface of the present invention, a state of defocusing (dispersion of light) from the medium surface of the present invention, and another state of defocusing from the medium surface of the present invention. It is explanatory drawing of the state condensed with the mirror to the medium surface of this invention, and the state defocused with the mirror from the medium surface of this invention. It is explanatory drawing which shows the recording medium at the time of rewriting of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Photothermal conversion layer 3 Reversible thermosensitive recording layer 4 Protective layer 11 Laser light irradiation part 12 Lens 13 Mirror 100 Reversible thermosensitive recording medium

Claims (10)

  A rewriting method for a reversible thermosensitive recording medium, wherein the image is rewritten by changing a spot diameter of a laser beam condensed on the surface of the reversible thermosensitive recording medium.   2. The method for rewriting a reversible thermosensitive recording medium according to claim 1, wherein the laser beam on the surface of the reversible thermosensitive recording medium is condensed to form an image, and the image is erased by defocusing.   The rewriting of the reversible thermosensitive recording medium according to claim 1 or 2, wherein the reversible thermosensitive recording medium is rewritten by relatively changing the positions of the lens for condensing the laser beam and the laser beam irradiation section. Method.   The reversible feeling according to any one of claims 1 to 3, wherein the reversible thermosensitive recording medium is rewritten by relatively changing the positions of the lens for condensing the laser beam and the reversible thermosensitive recording medium. A method for rewriting a thermal recording medium.   5. The reversible thermosensitive recording medium according to claim 1, wherein a mirror is provided between the lens and the reversible thermosensitive recording medium, and the reversible thermosensitive recording medium is rewritten by relatively changing the positions of the mirror and the condenser lens. A method for rewriting a reversible thermosensitive recording medium according to claim 1.   2. A reversible thermosensitive recording medium comprising a mirror between a lens and a reversible thermosensitive recording medium, wherein the position of the mirror and the reversible thermosensitive recording medium is relatively changed to rewrite the reversible thermosensitive recording medium. 6. The rewriting method for a reversible thermosensitive recording medium according to any one of 5 above.   The reversible thermosensitive recording medium according to any one of claims 1 to 6, wherein a mirror is provided between the lens and the reversible thermosensitive recording medium, and the reversible thermosensitive recording medium is rewritten by changing an installation angle of the mirror. A method for rewriting a reversible thermosensitive recording medium.   The rewriting method according to any one of claims 1 to 7, wherein the reversible thermosensitive recording medium comprises an electron donating color developing compound and an electron accepting compound.   The rewriting method according to claim 8, wherein the electron-accepting compound is a phenol compound having a hydrocarbon group having 8 or more carbon atoms.   An apparatus for carrying out the rewriting method for a reversible thermosensitive recording medium according to any one of claims 1 to 7.

Images