JP2006240037A - Erasing method, and rewriting method and apparatus for reversible thermosensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus which perform erasing only on a part where the erasing is necessary, and perform erasing and rewriting with a small amount of energy consumption, and in addition, prevent the whole head from over-heating to perform rewriting with a high density without decreasing in a printing image. <P>SOLUTION: The method for erasing and rewriting an image using a reversible thermosensitive recording medium capable of forming relatively a color-developed condition and a color-erased condition by difference in heating temperature and cooling speed, is characterized by reading image information before rewriting by a scanner and erasing it in accordance with the image information. In addition, there exists a case where regions for erasing and rewriting are determined in advance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an erasing method or a rewriting method for a reversible thermosensitive recording medium and an apparatus thereof capable of repeatedly printing and erasing by reversibly forming a colored state and a decoloring state by heating.

  Conventional hard copies are formed by image formation by externally attaching a colorant such as ink or toner to a recording medium such as paper, or a thermal recording layer on a substrate such as paper as in thermal recording paper. And forming a visible image by adding energy to the permanent image. However, with the recent spread of copying machines and facsimiles and the output of information from computers, the consumption of recording media has increased rapidly, causing social problems such as natural destruction and waste disposal. In order to solve this problem, a recording material that can erase a recorded visible image and can be used repeatedly has attracted attention.

  As such a recording medium, for example, there is a recording medium that can reversibly form two states of transparency and turbidity by utilizing the light scattering property of a polymer film in which organic low-molecular crystal particles are dispersed (for example, patents). Reference 1 etc.). This recording medium has already been put into practical use as a content display section of a magnetic card. However, the displayed image can display white printing on a black or blue colored background, or a light reflective background such as an aluminum vapor deposition film, and has the same visibility as a normal document. There wasn't.

  Furthermore, an electron-donating color-forming compound (hereinafter referred to as leuco dye) that can take two states of coloring and decoloring, and electron accepting, which can be used for ordinary hard copy, such as black coloring on a white background. A reversible thermosensitive recording medium (hereinafter abbreviated as “recording medium”) that can form a reversible color print image on a white background using a reversible thermosensitive recording layer of an organic compound (hereinafter referred to as a developer) has been proposed. (For example, refer to Patent Document 2).

  As a method for erasing and rewriting these reversible thermosensitive recording media, a thermal head, a heat roller, and the like have been proposed as a heating means for erasing in Patent Document 3 and the like. Thereafter, a belt-shaped ceramic heater is proposed in Patent Document 4 and the like. However, in these proposals, since the entire surface of the recording medium is heated, there is a problem in that the white portion which originally does not need to be erased is heated and more energy is consumed than necessary.

  In particular, when erasing or erasing / printing (overwriting) is performed with a thermal head, the heating element is heated over the entire line continuously over the entire line. Heat was supplied to the recording medium, and there were problems such as the appearance of color development (background fogging) at the erasing part and the deterioration of the surface of the printing part.

  On the other hand, a thermal head that detects the temperature of a heating element based on a change in electrical resistance and a thermal head that controls applied energy is proposed in Patent Document 5 and the like. By using this thermal head, the temperature of the heating element during erasing and printing can be controlled, and excessive heating of the recording medium can be prevented. However, although the heating element itself can be prevented from being overheated, all the dots are heated by all the lines, so that the entire head becomes hot and the recording medium is heated, so that rapid cooling after heating becomes impossible and the print density decreases. Had problems.

JP 55-154198 A JP-A-5-124360 JP-A-5-124360 JP 11-192737 A Japanese Patent Laid-Open No. 7-205469

  Accordingly, a first object of the present invention is to provide a method and apparatus for performing erasing and rewriting with a small amount of energy consumption by erasing only a portion that needs to be erased. The second problem is to prevent overheating of the entire head and to perform high-density rewriting without deterioration of the printed image.

  The above-described problem is in an image erasing or rewriting method using a reversible thermosensitive recording medium capable of forming a relatively colored state and a decolored state due to a difference in heating temperature and / or a cooling rate after heating. It has been found that the above problem can be solved by performing erasure or overwrite rewriting according to the image information before rewriting, or by making the image information area to be erased and rewritten a predetermined area.

That is, according to the present invention,
(1) Using an electron-donating color-forming compound and an electron-accepting compound on the support, a relatively colored state and a decolored state are formed depending on the heating temperature and / or the cooling rate after heating. An image erasing method using a reversible thermosensitive recording medium, wherein the image information before rewriting is read by a scanner and erased according to the image information,
(2) Using an electron-donating color-forming compound and an electron-accepting compound on the support, a relatively colored state and a decolored state are formed depending on the heating temperature and / or the cooling rate after heating. In an image rewriting method using a reversible thermosensitive recording medium, the image information before rewriting is read by a scanner, erased according to the image information, and at the same time, a new image is printed and overwrite rewriting is performed. Rewriting method of reversible thermosensitive recording medium,

(3) The method for erasing or rewriting a reversible thermosensitive recording medium according to (1) or (2), wherein a wider range than the image information read by the scanner is erased,
(4) The reversible thermosensitive recording medium erasing method according to (3), wherein the erasing range in (3) is a range from 1 to 5 dots before the image information read by the scanner. Or rewrite method,
(5) The erasing method for a reversible thermosensitive recording medium according to (3), wherein the erasing range in (3) is a range wider by 1 to 5 dots around the image information read by the scanner. Or rewrite method,
(6) The reversible thermosensitive recording medium erasing method according to claim 1, wherein the image information area to be erased is a predetermined area.
(7) The rewriting method of the reversible thermosensitive recording medium according to claim 2, wherein the image information area to be erased and rewritten is a predetermined area.
(8) In the erasing or rewriting according to any one of (1) to (7), the erasing or rewriting of the reversible thermosensitive recording medium, wherein a thermal head is used for erasing and / or printing. Rewriting device,
(9) The reversible thermosensitive recording medium according to (8), wherein the heat generating element of the thermal head used for erasing or printing is made of a material having a large temperature dependence of electrical resistance. Replacement device (10) A circuit in which a thermal head used for erasing or printing detects the temperature of a heating element based on a change in electrical resistance, and a circuit for controlling energy applied to the heating element based on the detected temperature A reversible thermosensitive recording medium erasing or rewriting device according to (8) or (9),

(11) In the thermal head according to (8), the circuit for controlling the applied energy presets the temperature reached by the heating element, and stops supplying energy at the same time that the temperature of the heating element reaches the temperature reached. A reversible thermosensitive recording medium erasing or rewriting device characterized by controlling the temperature of the heating element to be constant,
(12) The method for erasing or rewriting a reversible thermosensitive recording medium according to any one of claims 1 to 12, wherein the electron accepting compound used in the reversible thermosensitive recording medium is a phenol compound having 8 or more carbon atoms. And / or an apparatus thereof.

Next, the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a reversible thermosensitive recording medium 1 (hereinafter referred to as a recording medium) used in the present invention. As shown in the figure, the recording medium 1 has a reversible thermosensitive recording layer 3, a first protective layer 4, and a second protective layer 5 sequentially laminated on the upper surface of the support 2, and under the support 2. The back coat layer 6 is formed on the side surface. Here, the upper side refers to the surface facing the image reading scanner 21 described later, and the lower side refers to the opposite surface.

  The support 2 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 12 μm, and the first protective layer 4, the second transparent protective layer 5 and the backcoat layer 6 have a thickness of about 2 to 4 μm. is there.

  On the other hand, 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 fluoran compound, a phenothiazine compound, or a leucooramine compound.

  Further, the developer used for the reversible thermosensitive recording layer 3 has a structure having a color luster that develops a leuco dye in the molecule, such as a phenolic hydroxyl group, a carboxylic acid group, a phosphonic acid group, and a cohesive force between molecules. It is a compound having a structure that controls the structure, for example, a structure in which long chain hydrocarbon groups are linked. The connecting part may be through a divalent group containing a hetero atom, and the long chain hydrocarbon group may contain a divalent group or an aromatic group containing a hetero atom.

  Specifically, a known developer described in Patent Document 3 and the like can be preferably used. Among them, a phenol compound having a hydrocarbon group having 8 or more carbon atoms is particularly preferably used from the viewpoint of color developability / decolorability, and examples thereof include a compound having a structure represented by the following formula (1).

式中、X₁はヘテロ原子を含む２価の基または直接結合手を示し、X₂はヘテロ原子を含む２価の基を示す。R₁は２価の炭化水素基を表し、R₂は炭素数８から２２の炭化水素基を表す。また、pは０から４の整数を表しpが２から４の時繰り返されるR₁およびX₂は同一でも、異なっていても良い。また、qは１から３を表す。
X₁,X₂で示されるヘテロ原子を含む２価の基は−ＮＨ₂−、−ＣＯ−、−Ｏ−またはこれらの組み合わせによってできる基を表す。

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 8 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;
The divalent group containing a hetero atom represented by X ₁ or X _{2 represents} a group formed by —NH ₂ —, —CO—, —O— or a combination thereof.

  The reversible thermosensitive recording medium used in 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 a temperature T1 at which melting starts, and the leuco dye and the developer become a molten color state (B). 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 reversible thermosensitive recording medium, the colored state (C) obtained by quenching 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 is a solid state. Often formed. 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 developer are separated and stabilized by aggregation or crystallization. It is done.

  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. 2, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

  The color image of the present invention may be formed by heating to a temperature at which it is once melt-mixed by a thermal head or the like and then rapidly cooling. Further, decolorization is two methods, a method of slowly cooling from a heated state and a method of heating to a temperature slightly lower than the coloring temperature. However, they are the same in the sense that they are phase-separated or at least temporarily held at a temperature at which one crystallizes. The reason for the rapid cooling in the formation of the colored state is to prevent the temperature from being maintained at this phase separation temperature or crystallization temperature. The rapid cooling and slow cooling here are relative to one composition, and the boundary thereof changes depending on the combination of the color former and the developer.

  As described above, the recording layer can be erased by controlling the heating temperature and / or the cooling rate after heating. Printing with this heat-sensitive recording layer provides high contrast and excellent image quality.

  As the image reading scanner used in the present invention, for example, a line image sensor using a CCD (Charge Coupled Device) is used, and a document can be read and output as image information for each line.

  Further, laser light or a thermal head is used for erasing or printing an image, and the thermal head is particularly preferably used because the apparatus is small and easy to handle. In the present invention, the image information obtained by the scanner is used for erasing only the necessary portion, so that energy is not applied to the unnecessary portion and energy saving is possible. In addition, when overwriting with a normal thermal head, all the dots generate heat in all lines, the entire thermal head becomes hot, and printing and erasing defects and recording media due to excessive heat applied to the erasing section and printing section However, there is a problem that the print density is lowered without being subjected to the rapid cooling condition after printing, but the temperature rise of the entire head can be suppressed, and overwriting without these problems is possible. Become.

  In the present invention, by making the range of erasure wider than the image information read by the scanner, it is possible to perform good erasure and overwrite rewriting without afterimages due to defective erasure. This is because it takes time for the heating element to raise the temperature to the erasing temperature in the first erasing line, and it is difficult to obtain the temperature and time necessary for erasing. Stable erasure becomes possible. Preferably, the erasing energy is applied from 1 to 5 dots before the image information read by the scanner.

  Further, due to an error such as slippage during conveyance, the recording medium may be misaligned between the reading portion of the scanner and the erasing / printing portion having the thermal head. Therefore, it is possible to prevent unerased by applying erasing energy to a wider range than the image information read by the scanner. At this time, it is preferable that the range for setting erasure is wider by about 5 mm around the image information read by the scanner.

  In addition, as the thermal head used for erasing or printing in the present invention, a thermal head in which the electric resistance of the heating element greatly changes with respect to temperature is particularly preferably used. Here, the temperature dependency of electricity of the material used for the heat generating element may be positive or negative, but the one having a large negative temperature dependency is preferably used in terms of temperature control of the heat generating element. The circuit for detecting the temperature of the heating element detects the current flowing through the heating element during erasing or printing, and detects the temperature of the heating element from the resistance value of the heating element determined by the current value.

In addition, the circuit for controlling the energy applied to the heating element suppresses the energy application to the heating element when the detected temperature is equal to or higher than a predetermined temperature, and becomes lower than the specified temperature. It has a function of controlling the temperature of the heating element to be constant at the time of erasing or printing by increasing the applied energy at the time of erase.
By these controls, erasing can be performed more uniformly and stably, and the occurrence of defective erasure can be prevented. Further, when printing is performed, excessive heating of the recording medium can be prevented, and the recording medium is not damaged.

  With these methods and apparatuses, it is possible to apply erasing energy only to a portion where erasing is necessary, and energy consumption during erasing or rewriting is reduced. Further, overwriting rewriting with a thermal head can prevent the entire head from overheating, and can prevent a decrease in print density of the recording medium after rewriting.

The present invention will be described below based on examples.
FIG. 3 is a diagram showing an example of the erasing or rewriting apparatus of the present invention.
The recording medium is conveyed from the paper feed table 35 by the conveyance roller 33, and the image before rewriting is read by the scanner 31. Erasing is performed by the thermal head 32 in accordance with the image information. Alternatively, the rewritten image is printed at the same time as erasing, and overwrite rewriting is performed. Thereafter, the paper is discharged onto the paper discharge tray 36 by the transport roller 33. Reference numeral 38 denotes a control unit.

  FIG. 4 is a diagram showing an example of erasing according to the present invention. Erasing energy is applied from the thermal head in accordance with image information read by the scanner to erase the image information. A shows the image “1” before erasure. B is a view after erasing the image “1” halfway, and C is a view after erasing the image “1”. In either case, erasing is performed by applying erasing energy according to the image information read by the scanner. Since the erasing energy can be applied only to the necessary portion, the power consumption is small.

  FIG. 5 is a diagram showing an example of overwrite rewriting according to the present invention. A new image is printed at the same time as erasing energy is applied from the thermal head in accordance with image information read by the scanner. A shows the image “1” before erasure. B is a diagram in which the image “1” is rewritten to a new image “2” halfway, and C is a diagram in which the image “1” is rewritten to a new image “2”. Since the erasing energy can be applied only to the necessary portion, the energy consumption is reduced, and overheating of the thermal head during rewriting can be prevented, and a high print density can be obtained.

  FIG. 6 is a diagram showing an example of erasing according to the present invention. FIG. 5 is a diagram in which an image “1” similar to B in FIG. 4 is erased halfway. By starting erasing from one dot before the image before erasing, it is possible to perform good erasing without erasing defects due to insufficient temperature rise at the start of the thermal head, and consumption as in the example of FIG. Less power.

  FIG. 7 is a diagram showing an example of overwrite rewriting according to the present invention. FIG. 6 is a diagram in which “1” is rewritten to a new image “2” halfway, as in B of FIG. 5. By starting erasing from one dot before the image before erasing, it is possible to perform good erasing without erasing defects due to insufficient temperature rise at the start of the thermal head, and consumption as in the example of FIG. Rewriting high print density with low power.

  FIG. 8 is a diagram showing an example of erasing according to the present invention. FIG. 5 is a diagram in which an image “1” similar to B in FIG. 4 is erased halfway. By erasing a wider area than the image before erasure, it is possible to perform good erasure without erasure failure due to misalignment due to conveyance failure or the like, and further, power consumption is reduced as in the example of FIG. .

  FIG. 9 is a diagram showing an example of overwrite rewriting according to the present invention. FIG. 6 is a diagram in which “1” is rewritten to a new image “2” halfway, as in B of FIG. 5. By erasing a wider area than the image before erasure, it is possible to perform good erasure without erasure failure due to misalignment due to conveyance failure or the like, and furthermore, as in the example of FIG. Can be rewritten.

  FIG. 10 is an explanatory diagram of an example in which erasure and rewriting areas are determined in advance according to the present invention. Of the image information read by the scanner, the non-rewritable area 41 is not erased or rewritten, but the contents of the rewritten area 42 are rewritten to apply erasure or printing energy only to the area that needs to be rewritten. Energy saving.

  In FIG. 11, as in FIG. 10, the contents of the rewrite area 53 are rewritten without erasing or rewriting the non-rewrite area 51 of the image information read by the scanner. Further, the rewriting area 52 where the non-rewriting area and the rewriting area change each time performs rewriting of a necessary part.

  FIG. 12 shows an example of conventional erasure. FIG. 5 is a diagram in which an image “1” similar to B in FIG. 4 is erased halfway. This is the heating of all the lines on the entire surface, and the power consumption is large. Furthermore, there are problems such as background fogging due to heat storage of the head.

  FIG. 13 is a diagram showing an example of conventional overwrite rewriting. FIG. 6 is a diagram in which “1” is rewritten to a new image “2” halfway, as in B of FIG. 5. This is the heating of all the lines on the entire surface, and the power consumption is large. Furthermore, there are problems such as background fogging and a decrease in print density due to heat storage of the head.

1 is a cross-sectional view of a reversible thermosensitive recording medium used in the present invention. The figure which shows the color development / decoloring characteristic (color development / decoloration phenomenon) of the reversible thermosensitive recording medium used in the present invention. Example of erasing or rewriting device An example of erasure according to the present invention will be described. An example of overwrite rewriting of the present invention will be shown. An example of erasure according to the present invention will be described. An example of overwrite rewriting of the present invention will be shown. An example of erasure according to the present invention will be described. An example of overwrite rewriting of the present invention will be shown. It is explanatory drawing of the example which determined the area | region of erasing and rewriting beforehand by this invention. It is explanatory drawing of another example which determined the area | region of erasure rewriting by this invention previously. An example of conventional erasure is shown. An example of conventional overwrite rewriting is shown.

Explanation of symbols

31: Scanner
32: Thermal head
33: Transport roller
34: Platen roller
35: Paper feeder
36: Output tray
37: Transport guide
38: Control unit
41: Non-rewrite area
42: Rewrite area
51: Non-rewritable area
52: Rewrite area
53: Rewrite area

Claims (12)

A reversible sensation that can form a relatively colored state and a decolored state on the support using an electron-donating color-forming compound and an electron-accepting compound, depending on the heating temperature and / or the cooling rate after heating. An image erasing method using a thermal recording medium, wherein the image information before rewriting is read by a scanner and erased in accordance with the image information. A reversible sensation that can form a relatively colored state and a decolored state on the support using an electron-donating color-forming compound and an electron-accepting compound, depending on the heating temperature and / or the cooling rate after heating. In an image rewriting method using a thermal recording medium, overwriting rewriting is performed, in which image information before rewriting is read by a scanner and erased according to the image information, and at the same time, a new image is printed. A method for rewriting a reversible thermosensitive recording medium. 3. The method for erasing or rewriting a reversible thermosensitive recording medium according to claim 1, wherein a wider range than image information read by a scanner is erased. The erasing method or rewriting method for a reversible thermosensitive recording medium according to claim 3, wherein the erasing range in claim 3 is a range from 1 to 5 dots before the image information read by the scanner. 4. The method for erasing or rewriting a reversible thermosensitive recording medium according to claim 3, wherein the erasing range in claim 3 is a range that is wide by 1 to 5 dots around the image information read by the scanner. 2. The method for erasing a reversible thermosensitive recording medium according to claim 1, wherein the image information area to be erased is a predetermined area. 3. The reversible thermosensitive recording medium rewriting method according to claim 2, wherein the image information area to be erased and rewritten is a predetermined area. 8. An erasing or rewriting device using a reversible thermosensitive recording medium, wherein a thermal head is used for erasing and / or printing in erasing or rewriting according to any one of claims 1 to 7. 9. A reversible thermosensitive recording medium erasing or rewriting apparatus according to claim 8, wherein the heating element of the thermal head used for erasing or printing is made of a material having a large temperature dependence of electrical resistance. A thermal head used for erasing or printing includes a circuit for detecting a temperature of a heating element based on a change in electric resistance, and a circuit for controlling energy applied to the heating element based on the detected temperature. 10. An erasing or rewriting device for a reversible thermosensitive recording medium according to claim 8 or 9. 9. The thermal head according to claim 8, wherein the circuit for controlling the applied energy presets the reached temperature of the heating element, stops supplying energy at the same time as the temperature of the heating element reaches the reached temperature, and the heating element. A device for erasing or rewriting a reversible thermosensitive recording medium, wherein the temperature of the recording medium is controlled to be constant. The method for erasing or rewriting a reversible thermosensitive recording medium according to claim 1, wherein the electron accepting compound used in the reversible thermosensitive recording medium is a phenol compound having 8 or more carbon atoms. That device.

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