JP2007296722A - Thermal recording medium, image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording sheet and the like, which facilitate maintenance, which prevent the production of waste such as a cartridge, and which facilitate the management of the recording sheet. <P>SOLUTION: When heated at a temperature T1, a low-temperature color-development capsule 31 in an inner capsule 33 develops color. When heated at a temperature Ta (>T1) for a determined long period of time, the inner capsule 33 is put into a penetrated or destroyed state, and a low-temperature color-development function in the inner capsule 33 is suppressed (fixed) by a color-development inhibitor 39 outside the inner capsule 33 and inside an outer capsule 37. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermosensitive recording medium, an image forming apparatus for forming an image on the thermosensitive recording medium, and a method thereof.

Currently available printers include an ink jet method, a thermal transfer method, and a laser method in which a copier is computerized. These all transfer ink, ink ribbon, toner, and the like to paper (sheet). Therefore, when printing is finished, ink, ink ribbon, and a dedicated cartridge containing them become waste. Also, in order to achieve photographic image quality, it is necessary to use special paper after all.
On the other hand, there are thermal printers used for facsimile and barcode printing as printers that require dedicated recording sheets but do not discard ink, ink ribbon, and dedicated cartridges. There are many technical difficulties to realize photographic image quality color printing by such a thermal method, and it has not been put into practical use.
The biggest technical barrier is that it is difficult to control each color layer of three colors and three colors by controlling them independently only by thermal control of the thermal head, and to control the density gradation by adding shades to each color to be colored. For this reason, it was not possible to achieve color image quality printing. Under such circumstances, the direct thermal recording system (TA system), which was released in 1996 based on the technical idea of Patent Document 1 of Fuji Photo Film Co., Ltd., is the only practical example.

In this TA method, a heat-sensitive coloring layer is laminated on a substrate in the order of cyan, magenta, and yellow, and a heat-resistant protective layer is disposed as the uppermost layer. The yellow and magenta color-developing layers use diazonium salt compounds and couplers as color-developing materials and can fix images with ultraviolet rays. In addition, since the cyan coloring layer does not need to be fixed, a dye precursor and an organic acid are used as coloring materials. The microcapsules in each layer have different thermal sensitivities and ultraviolet sensitivities. By giving different thermal energy and different wavelength ultraviolet rays in five steps, full color prints are made while repeating coloring and fixing.
Specifically, in the TA method, (1) a yellow image is formed with low thermal energy using yellow image information, (2) ultraviolet light having a wavelength of 419 nm is irradiated on the entire surface, (3) the yellow image is fixed, and (4 ) Form a magenta image with medium heat energy (At this time, the yellow coloring layer does not develop even when heated, so it is not affected), (4) Irradiate the entire surface with ultraviolet light having a wavelength of 365 nm, fix the magenta image, (5) A cyan image is formed with high thermal energy.

  In addition to the above TA method, Patent Document 2 proposes a system in which a color is produced by chemically reacting a diazo compound in a capsule and a coupler outside the capsule by combining three pressures and three temperatures. Yes.

JP 61-40192 A JP-A-11-170692

However, the TA method has a problem that it is difficult to store the recording sheet because the thermosensitive coloring layer is fixed with ultraviolet rays.
Further, the above-described system of Patent Document 2 has a problem that it is difficult to control the color by applying three levels of pressure to the recording sheet appropriately.
There is also a demand for a thinner recording sheet and a simplified image forming process.
Furthermore, there is a demand to form a high-quality image without blurring.

In order to solve the above-described problems of the prior art, the present invention facilitates maintenance of an image forming apparatus, can form an image on a heat-sensitive recording medium with simple control without generating waste such as cartridges, and the like. An object of the present invention is to provide a thermal recording medium, an image forming apparatus, and an image forming method capable of easily managing the recording medium.
It is another object of the present invention to provide a thermal recording medium, an image forming apparatus, and an image forming method that can form a high-quality image free from blurring.

In order to solve the above-described problems of the prior art and achieve the above-described object, a color-encapsulating capsule according to claim 1 includes a color-developing element that develops color at a first temperature, the color-developing element, and the first color-encapsulating element. The inner capsule in which the capsule wall is in a permeation state or a destruction state when the second temperature is higher than the above temperature or when a predetermined pressure is applied, and coloring suppression that suppresses the coloring of the inner capsule and the coloring element And an outer capsule containing the agent.
In the coloring capsule according to claim 1, when the coloring capsule is heated at the first temperature, the coloring element develops color. Thereafter, when heated at the second temperature or when a predetermined pressure is applied, the inner capsule enters a permeation state or a destruction state, and the coloring function of the coloring element is suppressed by the coloring inhibitor.
In the coloring capsule of the present invention, a coloring reaction and a coloring inhibition reaction are performed in the outer capsule. For this reason, it is possible to avoid the occurrence of blurring due to the reaction of the color development inhibitor with other substances outside the outer capsule, and a high-quality image can be formed. In addition, since the colored capsule is fixed by pressure, the capsule can be easily managed.

According to a second aspect of the present invention, there is provided a first coloring element that develops color at a first temperature and the first coloring element, and when a second temperature higher than the first temperature is reached, or a predetermined temperature A color developing capsule having an inner capsule whose capsule wall is in a permeation state or a destroyed state when subjected to pressure, and an outer capsule containing the inner capsule and a color development inhibitor that suppresses color development of the first color development element; And a second coloring element that develops color at a third temperature higher than the second temperature.
The invention of claim 2 is a heat-sensitive recording medium using the color capsule of claim 1 as a first color developing element, and the same effect as that of claim 1 can be obtained.

According to a third aspect of the present invention, in the second aspect of the invention, the first coloring element is colored on condition that the first temperature is in the first temperature for a first time, and the second coloring element is Coloring is performed on condition that the third temperature is in a second time shorter than the first time.
In this way, by setting time in addition to temperature as the color development condition of each color development element, unintended color development can be suppressed and high image quality can be achieved.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the third color development is performed on condition that the fourth temperature higher than the third temperature is in a third time shorter than the second time. The color development capsule is disposed in the first color development layer, the second color development element is disposed in the second color development layer, and the third color development element is disposed in the third color development layer. And the first coloring layer, the second coloring layer, and the third coloring layer are laminated on a substrate.
A color image can be formed by using three kinds of coloring elements. In this case, since only one type of pressure is applied to the thermal recording medium during image formation, control is simple.

  The invention according to claim 5 is the invention according to claims 2 to 4, wherein the coloring element is an element that releases the material contained in the coloring element to the outside of the coloring element and reacts with a substance outside the coloring element, Alternatively, a material outside the coloring element flows into the coloring element and reacts with a substance in the coloring element to cause coloring in the coloring element.

  According to a sixth aspect of the present invention, in the second to fifth aspects of the present invention, the color development inhibitor is an electron donating dye precursor, an electron accepting developer, a basic substance, or an acidic substance, which is a material of the coloring element. Among them, the function of changing the chemical structure of one or more materials so as not to cause a color reaction, the electron donating dye precursor, the electron accepting developer, the basic substance or the acid that is the material of the color developing element Among substances, the function of changing the chemical structure of one or more materials to prevent coloring even if a chemical reaction is generated, or the substance on the wall of the microcapsule enclosing the coloring element material It is characterized by having a function of suppressing the color development reaction by changing the permeability to reduce the permeability.

An image forming apparatus according to a seventh aspect of the present invention includes a thermal head for thermally recording an image on a thermal recording medium, and a low temperature coloring process for controlling the thermal head so as to form an image on the thermal recording medium at a low temperature coloring temperature. And after the low-temperature color development treatment, the low-temperature color development suppression processing for controlling the thermal head so as to suppress the low-temperature color development of the thermal recording medium at a color development suppression temperature higher than the low-temperature color development temperature; Control means for performing high-temperature color development processing for controlling the thermal head so as to form an image on the thermal recording medium at a high temperature color development temperature higher than the color development suppression temperature.
According to the seventh aspect of the invention, the following operation is performed according to the control of the control means.
The thermal head heats the heat-sensitive recording medium at a low-temperature coloring temperature, and forms a low-temperature coloring image on the heat-sensitive recording medium.
Next, the thermal head heats the thermal recording medium at a color development suppression temperature higher than the low temperature color development temperature, and suppresses low temperature color development of the thermal recording medium.
Next, the thermal head heats the thermosensitive recording medium at a high temperature color development temperature higher than the color development suppression temperature, and forms a high temperature color image on the thermosensitive recording medium.

An image forming apparatus according to an eighth aspect of the present invention includes a thermal head that thermally records an image on a thermal recording medium, a pressurizing unit that applies a pressure for suppressing a low temperature coloring function of the thermal recording medium, and a low temperature coloring temperature. A low-temperature color development process for controlling the thermal head so as to form an image on the thermal recording medium, and a low-temperature color development control for controlling the pressurizing unit so as to apply the pressure to the thermal recording medium after the low-temperature color development process. And a control means for performing, after the low temperature color development suppression process, a high temperature color development process for controlling the thermal head so as to form an image on the thermal recording medium at a high temperature color development temperature higher than the color development suppression temperature.
According to the seventh aspect of the invention, the following operation is performed according to the control of the control means.
The thermal head heats the heat-sensitive recording medium at a low-temperature coloring temperature, and forms a low-temperature coloring image on the heat-sensitive recording medium.
Next, the pressurizing unit applies a predetermined pressure to the heat-sensitive recording medium, and suppresses low-temperature color development of the heat-sensitive recording medium.
Next, the thermal head heats the thermosensitive recording medium at a high temperature color development temperature higher than the color development suppression temperature, and forms a high temperature color image on the thermosensitive recording medium.

  According to a ninth aspect of the present invention, in the eighth aspect of the invention, the thermal head and the pressurizing unit are integrally configured, and the pressure is applied by a heating surface of the thermal head that contacts the thermal recording medium. It is a feature.

  According to a tenth aspect of the present invention, there is provided an image forming method comprising: a first step of forming an image on a thermal recording medium by heating at a low temperature coloring temperature; and a coloring suppression temperature higher than the low temperature coloring temperature after the first step. A second step of suppressing the low-temperature color development of the thermal recording medium by heating, and an image is formed on the thermal recording medium by heating at a high color development temperature higher than the color suppression temperature after the second step. And a third step.

  An image forming method according to an eleventh aspect of the present invention includes a first step of forming an image on a thermal recording medium by heating at a low temperature coloring temperature, and applying a predetermined pressure to the thermal recording medium after the first step. A second step of suppressing low-temperature color development of the thermal recording medium, and a third step of forming an image on the thermal recording medium by heating at a high temperature color development temperature higher than the color development suppression temperature after the second step. Process.

According to the present invention, maintenance of an image forming apparatus is easy, images can be formed on a thermal recording medium with simple control without generating waste such as cartridges, and the thermal recording medium can be easily managed. And a thermal recording medium, an image forming apparatus, and an image forming method.
In addition, according to the present invention, it is possible to provide a thermal recording medium, an image forming apparatus, and an image forming method capable of forming a high-quality image without blurring.

Hereinafter, a recording sheet according to an embodiment of the present invention and a printer that forms an image on the recording sheet will be described.
<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described.
[Correspondence with Configuration of the Present Invention]
First, the correspondence between the components of the present embodiment and the components of the present invention will be described.
A low temperature coloring capsule 31 shown in FIG. 2 is an example of the coloring element of claim 1, the inner capsule 33 is an example of the inner capsule of the present invention, and the outer capsule 37 is an example of the outer capsule of the present invention. The low-temperature color development inhibitor 39 is an example of the color development inhibitor of the present invention.
The low temperature color development / color development inhibition capsule 21 is an example of a color development capsule according to claim 2, the medium temperature color development capsule 25 is an example of a second color development element, and the high temperature color development capsule 27 is an example of a third color development element. is there.
A thermal head 45 shown in FIG. 6 is an example of a thermal head according to a seventh aspect. Moreover, the control part 51 shown in FIG. 6 is an example of the control means of Claim 7 grade | etc.,.

[Recording sheet 10]
First, the recording sheet 10 used in this embodiment will be described.
FIG. 1 is a cross-sectional configuration diagram of a recording sheet 10 used in the present embodiment.
As shown in FIG. 1, the recording sheet 10 includes, for example, a low-temperature coloring layer 9, a thermal barrier layer 11, a medium-temperature coloring layer 13, a thermal barrier layer 15, a high-temperature coloring layer 17, and a protective layer 19 that are sequentially laminated on a substrate 11. Configured.

The low temperature coloring layer 9 of the recording sheet 10 includes a low temperature coloring / coloring inhibiting capsule 21. The low temperature coloring / coloring inhibition capsule 21 includes a low temperature coloring capsule and a coloration inhibiting agent therein.
The low temperature coloring / coloring inhibiting capsule 21 has a double capsule structure constituted by an inner capsule 33 and an outer capsule 37 enclosing the inner capsule 33.
When the low-temperature color development / color development suppression capsule 21 is heated at the temperature T1, the low-temperature color development capsule 31 in the inner capsule 33 develops color.

Then, when the low temperature color development / color development suppression capsule 21 is heated at a temperature Ta (> T1) for a predetermined long time, the inner capsule 33 is in a permeation state or a destruction state. The low color development function in the inner capsule 33 is suppressed (fixed) by the color development inhibitor 39 inside. In the present embodiment, the predetermined long time required for the color development of the low temperature color development / color development suppression capsule 21 is a medium time and a time shorter than the short time which are color development conditions described later of the medium temperature color development capsule 25 and the high temperature color development capsule 27. Define.
According to the low temperature color development / color development inhibition capsule 21, since the color development reaction and the color development inhibition reaction are performed in the outer capsule 37, high quality image formation without blurring can be achieved. That is, since the low-temperature color development inhibitor 39 is maintained in the outer capsule 37, it is possible to avoid a reaction that causes image quality degradation due to the low-temperature color development inhibitor 39.

  The substrate 11 is made of, for example, polyester or polyethylene terephthalate (PET). The base material 11 is white or transparent.

The low temperature coloring layer 9 contains the low temperature coloring / coloring inhibiting capsule 21 shown in FIG. 2 dispersed in a binder.
As shown in FIG. 2, the low temperature coloring / coloring inhibiting capsule 21 has a double capsule structure including an inner capsule 33 and an outer capsule 37.
The inner capsule 33 includes a low-temperature coloring capsule 31, a coupler (developer) 35, and, if necessary, a basic substance or an acidic substance dispersed therein.
The outer capsule 37 includes the inner capsule 33 and the color development inhibitor 39.

The low temperature coloring capsule 31 encapsulates the coloring agent, and the glass transition point of the wall is a temperature T1 (for example, 100 ° C.) shown in FIG. 3, which is lower than the medium temperature coloring capsule 25 and the high temperature coloring capsule 27.
For example, when the low temperature state of the temperature T1 or more continues for a predetermined long time, the inner capsule 33 reacts with the color former contained in the low temperature coloring capsule 31 and the coupler 35 in the inner capsule 33 to develop color.

  The low temperature coloring capsule 31 is a so-called microcapsule, and its wall is made of polyurea or polyurethane having a glass transition point of 90 to 140 ° C. The low temperature coloring capsule 31 has a characteristic that the material permeability (permeability) increases before and after the glass transition point. As a result, as shown in FIG. 4A, at a temperature lower than T1 (non-low temperature), the coupler 35 does not penetrate into the low temperature coloring capsule 31, and the coloring agent in the low temperature coloring capsule 31 does not develop color. On the other hand, as shown in FIG. 4B, when the temperature T1 or higher (the low temperature state) continues for a predetermined long time, the coupler 35 in the inner capsule 33 penetrates into the low temperature coloring capsule 31, and the coupler 35 and the low temperature coloring. The coloring agent in the capsule 31 reacts to form a dye to develop color.

The wall of the microcapsule in the present embodiment such as the low-temperature coloring capsule 31 is formed of a synthetic resin such as a thermosetting resin or a thermoplastic resin, for example. Specifically, melamine-formaldehyde polymer, urea-formaldehyde polymer, or the like is used as the wall of the low temperature coloring capsule 21 or the like.
The average particle diameter of the microcapsules of the low temperature color development capsule 31, the medium temperature color development capsule 25, and the high temperature color development capsule 27 is, for example, about 3 to 4 μm, and the glass transition point is defined by the wall material. The average particle diameter of the outer capsule 37 and the inner capsule 33 of the low-temperature color development / color development inhibiting capsule 21 is, for example, 10 to 30 μm. The microcapsule not only keeps the reacting substances in a multi-layered structure, but also disperses them in micron across the wall of the microcapsule so that it can coexist in a thin coating film of several microns at room temperature. While maintaining sufficient isolation, it has the function of giving sufficient material permeability instantaneously during heating.

Note that the low temperature coloring capsule 31 may be configured such that, when the low temperature coloring capsule 31 is in the low temperature state, the wall melts and the coloring agent in the capsule flows out of the capsule and reacts with the coupler 35 outside the capsule to develop color. Good.
In the present embodiment, the combination of the color former and the coupler (developer) 35 that reacts therewith includes, for example, a combination of a diazo compound (color developer) and a coupler (developer), or an electron-donating colorless dye. There are combinations of (color former) and electron accepting compound (developer). It is known that an arbitrary hue can be colored by a combination of a chemical structure of a diazo compound and a chemical structure of a coupler, or a combination of a chemical structure of an electron-donating colorless dye and a chemical structure of an electron-accepting compound.

The diazo compound is, for example, tricresyl phosphate. The diazo compound is an electron donating dye precursor (dye precursor), and reacts with a coupler in a basic atmosphere to develop a color. The coupler is, for example, resorcil or phloroglucin, and forms a dye by coupling with a diazo compound in a basic atmosphere. The basic atmosphere is made of a hardly water-soluble or water-insoluble basic substance or a substance that generates alkali by heating (for example, an organic ammonium salt).
The electron-donating colorless dye is, for example, a leuco dye, and the electron-accepting compound is, for example, a phenolic acidic substance. In this combination, the leuco dye is adsorbed by the developer, which is an acidic substance, and oxidized to develop a color.

As the coupler 35, for example, 2-hydroxy-3naphthoic acid anilide or the like is used.
Moreover, as said electron-accepting compound, acidic substances, such as a phenol compound, an organic acid or its metal salt, and oxybenzoic acid ester, are used, for example.

  Further, in this embodiment, the case where the color former is encapsulated in the microcapsule is exemplified, but for example, the color former and the developer are dispersed and arranged in the binder, and the binder is melted by heating to cause the color former. The developer may react with the developer.

The inner capsule 33 has a glass transition point of its wall at a temperature Ta (for example, 130 ° C.) shown in FIG. 3, which is higher than the low temperature coloring capsule 31 and lower than the medium temperature coloring capsule 25 and the high temperature coloring capsule 27.
When the state of the inner capsule 33 is maintained at a temperature Ta or higher for a certain period of time, the capsule wall is in a permeation state or a destruction state, and the low temperature color development inhibitor 39 outside the inner capsule 33 and inside the outer capsule 37, and the inner capsule The low-temperature coloring capsule 31 and the coupler 35 in 33 are mixed. Thereby, the color development suppressing function of the low temperature color development inhibitor 39 is exhibited, and the low temperature color development function in the inner capsule 33 is suppressed. Here, the certain time is defined as a time shorter than the long time and longer than the medium time, for example.
As the material of the wall of the inner capsule 33, a material having sufficient resistance to the acidic substance or basic substance in the inner capsule 33 and the coupler 35 is used. As a material of the inner capsule 33, for example, a commercially available phase change acrylic polymer material can be used.

The low-temperature color development inhibitor encapsulated in the outer capsule 37 changes the chemical structure of one or more of the color former, the coupler 35, the basic substance, and the acidic substance of the low-temperature color development capsule 31 in the inner capsule 33, for example. Thus, it has a function of preventing a chemical reaction from occurring or a function of preventing a dye from being generated even when a chemical reaction occurs.
Further, the low-temperature color development inhibitor 39 may have a function of suppressing the color development reaction by changing the material permeability of the capsule wall of the low-temperature color development capsule 31 to reduce the permeability.
In the present embodiment, the temperature condition of the temperature Ta or higher is exemplified as the condition for exhibiting the color development suppressing function of the low temperature color development inhibitor 39, but it may be a condition that a predetermined pressure is applied.

The wall of the outer capsule 37 has, for example, sufficient resistance to the low-temperature color development inhibitor 39, and the outer capsule 37 when the inner capsule 33 is in a permeation state or a broken state and exhibits a low-temperature color development suppression function. It is made of a material that has sufficient resistance to the substances inside. Furthermore, the material of the wall of the outer capsule 37 needs to be a material that does not melt even at the temperature T3 that is the color development temperature of the high temperature color development capsule 27. Specifically, polymer materials such as polyurethane, polyurea, epoxy resin, urea / formalin resin, melanin / formalin resin and the like are used.
The outer capsule 37 appropriately separates the inside and the outside of the capsule without penetrating and destroying during the image forming process of the recording sheet 10 and the interpolation of the recording sheet 10.

When the inner capsule 33 is colored by a combination of an electron donating colorless dye (color developing agent: for example, leuco dye) and an electron accepting compound (developer: for example, acidic substance), the low temperature coloring capsule 31
For example, phosphoric acid esters, tetrahydrophthalic acid, fatty acid esters, dihydric alcohol esters, epoxy plasticizers or trimetic acid plasticizers are used.

For example, when the intermediate temperature coloring layer 13 and the high temperature coloring layer 17 are heated from the protective layer 19 side to develop color, the heat barrier layer 11 transmits the heat to the low temperature coloring layer 9 and the low temperature coloring layer 9 develops color. It has a function to suppress.
The thermal barrier layer 11 is made of any material including an inert material that undergoes a phase change during heating, for example, when the layer includes a thermal solvent. A typical material for the thermal barrier layer 11 is a polymer material such as poly (vinyl alcohol).

  The intermediate temperature coloring layer 13 is configured by dispersing a medium temperature coloring capsule 25, a developer, and, if necessary, a basic substance or an acidic substance in a binder material. The medium temperature coloring capsule 25 encloses the color developing agent, and the glass transition point of the wall is, for example, a medium temperature of 150 to 280 ° C. For example, when the intermediate temperature coloring layer 13 has a medium temperature state equal to or higher than the temperature T2 (> Ta, Ta is, for example, 160 ° C.) shown in FIG. The developed color reacts to develop color. Except for the glass transition point of the wall of the intermediate temperature coloring capsule 25, the principle of coloring is the same as that of the low temperature coloring capsule 31 shown in FIG. The medium time, which is the coloring condition of the medium temperature coloring capsule 25, is defined as a time shorter than the long time, which is the coloring condition of the low temperature coloring capsule 31, and shorter than the short time, which is the coloring condition of the high temperature coloring capsule 27.

  The thermal barrier layer 15 has a function of preventing the intermediate temperature coloring layer 13 from being colored by transferring the heat to the intermediate temperature coloring layer 13 when the high temperature coloring layer 17 is heated from the protective layer 19 side and develops color. Have The material of the thermal barrier layer 15 is the same as that of the thermal barrier layer 11 described above, for example.

  The high-temperature coloring layer 17 is configured by dispersing a high-temperature coloring capsule 27, a developer, and, if necessary, a basic substance or an acidic substance in a binder material. The high-temperature coloring capsule 27 encloses the coloring agent, and the glass transition point of the wall is, for example, a high temperature of 300 to 350 ° C. For example, when the high-temperature coloring layer 17 is kept at a high temperature equal to or higher than the temperature T3 (eg, 330 ° C.) shown in FIG. 3 for a predetermined short time, the color former contained in the high-temperature coloring capsule 27 and the developed color in the high-temperature coloring layer 17 are used. Color develops when the agent reacts. Except for the glass transition point of the wall of the high temperature coloring capsule 27, the coloring principle is the same as that of the low temperature coloring capsule 31 shown in FIG.

  The protective layer 19 is a layer for protecting the low temperature coloring layer 9. The protective layer 19 has, for example, a heat resistance function.

In the present embodiment, the thickness of each of the low-temperature coloring layer 7, the low-temperature coloring layer 9, the medium-temperature coloring layer 13, and the high-temperature coloring layer 17 is, for example, 1 to 4 μm.
The thickness of the thermal barrier layer 11 is, for example, 5 to 25 μm, and the thickness of the thermal barrier layer 15 is, for example, 3 to 10 μm.
As shown in FIG. 5, for example, yellow is assigned to the low-temperature coloring layer 9, magenta is assigned to the medium-temperature coloring layer 13, and cyan is assigned to the high-temperature coloring layer 17, as shown in FIG. However, this is an example, and the allocation pattern is arbitrary.
In this embodiment, in the printer 40, heating is performed from the protective layer 19 side when each layer of the recording sheet 10 is colored.

[Printer 40]
Next, a printer that forms an image on the recording sheet 10 shown in FIG. 1 will be described.
Note that the printer described below in this embodiment is an example, and an image may be formed on the recording sheet 10 by using a printer described in a modified example described later.
FIG. 6 is a configuration diagram of the printer 40 that records (prints) an image on the recording sheet 10 shown in FIG. 1.
As illustrated in FIG. 6, the printer 40 includes, for example, a sheet storage case 41, a sheet feeding roller 43, a thermal head 45, a platen roller 47, and a control unit 51.
The sheet storage case 41 stores a plurality of recording sheets 10. The recording sheet 10 stored in the sheet storage case 41 is pressed toward the sheet feeding roller 43 by an urging means such as a spring 53.

  The sheet feeding roller 43 is positioned in contact with the uppermost recording sheet 10 of the sheet storage case 41. The sheet feeding roller 43 is rotationally driven by a motor (not shown) based on a control signal from the control unit 51. When the sheet feeding roller 43 rotates, the frictional force generated between the recording sheet 10 and the sheet feeding roller 43 by the urging force of the spring 53 interlocks with the rotation of the sheet feeding roller 43 and the uppermost stage of the sheet storage case 41. The recording sheet 10 is conveyed toward the thermal head 45. The controller 51 controls the position and feed amount of the recording sheet 10 by controlling the rotation amount of the motor (sheet feed roller 43) based on the control signal.

A thermal head 45 is provided on the downstream side of the sheet feeding roller 43 in the conveyance path of the recording sheet 10.
The thermal head 45 includes a heating element array in which a plurality of heating elements are arranged in a line in the main scanning direction. The thermal head 45 causes each heating element to generate heat in a pattern corresponding to the image to be formed, with the heating element array in contact with the recording sheet 10. In the present embodiment, each heat generating element has at least five states of a non-heat generation state, a low temperature heat generation state, a fixing heat generation state, an intermediate temperature heat generation state, and a high temperature heat generation state, and one of these five states is selected by the control unit 51. Is done.
The heat generation temperature of each heat generating element is controlled by the time during which a current flows through a resistor connected to the heat generating element. The control unit 51 controls the pulse width of the strobe signal that defines the time during which a current flows to each heating element of the thermal head 45 according to the heating time.

As another temperature control method, for example, the control unit 51 may control a voltage generated between the heating elements according to the heat generation temperature (control so that the voltage increases as the heat generation temperature increases). .
Further, when each heating element generates heat by a voltage corresponding to the level of the control signal, the control unit 51 can control the density of each color by controlling the pulse potential, the pulse width, and the number of pulses of the control signal.
The thermal head 45 may be capable of adjusting a plurality of heat generation temperatures in accordance with the gradation of the image data in each of the low temperature coloring state, the fixing heat generation state, the medium temperature coloring state, and the high temperature coloring state.

  The platen roller 47 is provided with a thermal head 45 on the opposite side across the conveyance path of the recording sheet 10. The platen roller 47 rotates according to the conveyance of the recording sheet 10, and stabilizes the contact state between the recording sheet 10 and the heating element of the thermal head 45.

  The control unit 51 is an electronic circuit such as a microcomputer, for example, and comprehensively controls the operation of the printer 40. The processing of the control unit 51 is described in, for example, a program.

Hereinafter, an operation example of the printer 40 will be described with reference to FIGS. 6 and 7.
FIG. 8 is a flowchart for explaining an operation example of the printer that forms an image on the recording sheet 10 shown in FIG.

Step ST0:
A plurality of recording sheets 10 are stored in a sheet storage case 41 of the printer shown in FIG. The recording sheet 10 stored in the sheet storage case 41 is pushed toward the paper feed roller 43 by the urging force of the spring 53, and a frictional force is generated between the uppermost recording sheet 10 and the paper feed roller 43. .

Step ST1:
Based on the control from the control unit 51, the sheet feeding roller 43 rotates and the recording sheet 10 accommodated in the uppermost stage of the sheet accommodation case 41 is conveyed toward the thermal head 45.

Step ST2:
Based on the control from the control unit 51, the thermal head 45 causes each heating element to generate heat at the low temperature for the predetermined long time with a pixel pattern corresponding to the low-temperature coloring component of the image formed on the recording sheet 10. As a result, the low-temperature coloring layer 9 of the recording sheet 10 has a pixel pattern of a low-temperature coloring component corresponding to image information, and is heated for a long time at a low temperature T1 shown in FIG. The color former in the low temperature coloring capsule 31 of the suppression capsule 21 reacts with the coupler 35 in the inner capsule 33 to develop color.
At this time, the inner capsule 33 fulfills the isolation function because its wall is not melted and broken.
Further, the medium temperature coloring capsule 25 and the high temperature coloring capsule 27 do not satisfy the coloring condition, and thus do not develop color.

Step ST3:
Subsequent to step ST2, based on the control from the control unit 51, the thermal head 45 causes each heating element in the entire head contact surface of the recording sheet 10 to be at a temperature higher than the temperature Ta and lower than the temperature T2 shown in FIG. Heat is generated (for example, shorter than the long time and longer than the medium time). As a result, the inner capsule 33 of the low temperature coloring / coloring inhibiting capsule 21 shown in FIG. As a result, the low temperature coloring capsule 31 and the coupler 35 in the inner capsule 33 react with the low temperature coloring inhibitor 39 outside the inner capsule 33, and the coloring function of the low temperature coloring capsule 31 is suppressed. That is, low temperature color development is fixed. At this time, since the low-temperature color development inhibitor 39 is maintained in the outer capsule 37, it is possible to avoid a reaction that causes image quality degradation due to the low-temperature color development inhibitor 39.

Step ST4:
Subsequent to step ST3, based on the control from the control unit 51, the thermal head 45 causes each heating element to generate heat at a high temperature in a short time with a pixel pattern corresponding to the high-temperature coloring component of the image formed on the recording sheet 10. As a result, the high-temperature coloring layer 17 of the recording sheet 10 is heated for a short time at a high temperature T3 shown in FIG. The color former in the inside reacts with the surrounding coupler to develop color (high temperature color development).
At this time, since the low temperature coloring layer 9 has already been fixed, low temperature coloring does not occur. Further, a thermal barrier layer 15 is interposed between the high temperature coloring layer 17 and the intermediate temperature coloring layer 13. The high temperature heating time is short. Therefore, the high temperature coloring layer 17 can be colored without causing the medium temperature coloring layer 13 to develop color due to the heat transfer time (delay time) by the thermal barrier layer 15.

Step ST5:
Subsequent to step ST4, based on the control from the control unit 51, the thermal head 45 causes each heating element to generate heat at an intermediate temperature and an intermediate time with a pixel pattern corresponding to the intermediate temperature coloring component of the image formed on the recording sheet 10. As a result, the medium temperature coloring layer 13 of the recording sheet 10 is heated at a medium temperature of the temperature T2 shown in FIG. The color former and the surrounding coupler react to develop color (medium temperature color development).
At this time, the high temperature coloring layer 17 does not satisfy the coloring condition, and thus does not develop color. Further, the low temperature coloring layer 9 has already been fixed and the presence of the thermal barrier layer 11 does not cause color development.

  In the present embodiment, the coloring process and the fixing process in steps ST <b> 2 to ST <b> 5 are sequentially performed on the area on the recording sheet 10 where the thermal head 45 is in contact. When the process of steps ST2 to ST4 is completed for the contact area, the platen roller 47 rotates and the processes of steps ST2 to ST5 are performed for the next contact area.

Step ST6:
Based on the control from the control unit 51, the platen roller 47 rotates, and as shown in FIG. 6, the recording sheet 10 is conveyed toward the right exit in FIG.

As described above, according to the recording sheet 10, as shown in FIG. 2, the color development reaction and the color development suppression (fixing) reaction are performed in the low temperature color development / color development inhibition capsule 21, It is possible to prevent the color development inhibitor from reacting with other substances outside the capsule and generating unintended blemishes, and high-quality image formation can be achieved. That is, since the low-temperature color development inhibitor 39 is maintained in the outer capsule 37, it is possible to avoid a reaction that causes image quality degradation due to the low-temperature color development inhibitor 39.
Further, according to the recording sheet 10, since the color development of the low-temperature color development layer 9 is suppressed (fixed), discoloration after image formation can be suppressed, and weather resistance can be improved. Further, since it is not ultraviolet fixing, management of the recording sheet 10 becomes easy.
Further, according to the recording sheet 10 and the printer 40 of the present embodiment, consumables such as an ink cartridge and an ink ribbon are not necessary. Therefore, compared with a printer that requires a conventional ink cartridge or the like, it is not necessary to replace the ink cartridge, maintenance becomes easy, and running costs can be reduced. Further, according to the present embodiment, waste such as used ink ribbons and cassettes can be eliminated. Note that according to the recording sheet 10 and the printer 40 of the present embodiment, the print content does not remain on the sheet side unlike the method using the ink ribbon, and thus the confidentiality is excellent.

Also, according to the printer 40 of the present embodiment, as shown in FIG. 7, low-temperature color development, low-temperature fixing, high-temperature color development, and medium-temperature color development are performed in order, so these processes are performed by the thermal head 45 of the printer shown in FIG. It can be realized continuously by controlling the temperature and time with the head. Accordingly, the configuration and control of the printer 40 can be simplified, and image formation can be performed in a short time. This is useful for reducing the manufacturing cost because the thermal head is expensive, and can meet the demand for miniaturization.
That is, when a single line-type thermal head is realized, in the conventional TA system, the recording sheet is passed through the thermal head two and a half times, so that the image forming time is long. In addition, the TA method also requires a UV lamp and two types of filter switching means, which increases the size of the printer. The printer of this embodiment can solve such problems.

  In the recording sheet 10, the high temperature coloring layer 17 is disposed on the protective layer 19 side, and the low temperature coloring layer 9 is disposed on the substrate 5 side. Therefore, energy during heating by the printer 40 can be reduced and the heating time can be shortened.

Second Embodiment
In the first embodiment described above, as shown in FIG. 3, the condition for exhibiting the low-temperature color development suppressing function (condition in which the wall of the inner capsule 33 is in a permeation state or a destruction state) is defined by a temperature condition of a temperature Ta or higher. .
The recording sheet 110 of the present embodiment has the configuration shown in FIG. 1, and only the inner capsule 133 of the low-temperature color development / color development suppressing capsule 121 shown in FIG. 2 is different from the inner capsule 33 of the first embodiment.
As shown in FIG. 8A, the inner capsule 133 is in a broken state (or infiltrated state), for example, on the condition that a pressure equal to or higher than a predetermined pressure P1 is applied instead of the temperature condition, and the low temperature coloring is performed. The color suppressing function by the inhibitor 39 is exhibited.
In the recording sheet 110, the coloring conditions of the low temperature coloring capsule 31, the medium temperature coloring capsule 25, and the high temperature coloring capsule 27 are shown in FIG. 8B and are the same as those in the first embodiment.

The printer that forms an image on the recording sheet 110 described above has, for example, a configuration using the thermal head 45 shown in FIG. 6 and the thermal head 445 shown in FIG.
The thermal head 445 shown in FIG. 9 presses the recording sheet 10 or the like with the heating surface of the head unit 545.
In the configuration shown in FIG. 9, the head 545 is fixed to one end of the joint 520. The joint 520 rotates around the central axis 520a. The other end of the joint 520 is biased by a spring 541 in a direction in which the joint 520 is rotated counterclockwise about the rotation shaft 520a. The urging force of the spring 541 acts as a force that pushes the recording sheet 110 with the normal pressure P0 shown in FIG.

The joint 521 is installed so as to be rotatable about the rotation shaft 520 a, and the tip 521 a at one end is in contact with one side of the joint 520.
Further, the other end 521 b of the joint 521 is in contact with the outer periphery of the cam 530. Further, one end of the spring 540 is fixed to the joint 521. When the cam 530 rotates, the joint 521 rotates alternately around the rotation shaft 520a in the clockwise direction and the counterclockwise direction with a predetermined rotation angle width corresponding to the step on the outer periphery of the cam 530.
At this time, the tip 521a does not press the joint 520 at the position where the joint 521 is most rotated in the clockwise direction. That is, the biasing force of the spring 540 does not act on the thermal head 545.

On the other hand, at the position where the joint 521 is most rotated counterclockwise, the tip 521a presses the joint 520, and the urging force of the spring 540 acts in a direction to press the thermal head 545 against the recording sheet 10. As a result, a force that pushes the recording sheet 110 with the breaking pressure P1 shown in FIG.
In the printer using the configuration of FIG. 9, the control unit 51 can control the pressure applied to the recording sheet 110 via the heating surface of the head unit 545 by controlling the rotation of the cam 530.

The operation of the printer is that, in step ST3 shown in FIG. 7, the thermal head 445 applies a breaking pressure P1 to the recording sheet 110 to break the inner capsule 33 shown in FIG. The operation is the same as that of the printer 40 of the first embodiment.
Also in the printer of this embodiment, as with the printer 40 of the first embodiment, a plurality of heating temperatures and pressurization can be realized with one head, so that an image can be formed on the recording sheet 110 in one pass. That is, an image can be formed by passing the recording sheet 110 once in contact with the head.

The present invention is not limited to the embodiment described above.
That is, those skilled in the art may make various modifications, combinations, subcombinations, and alternatives regarding the components of the above-described embodiments within the technical scope of the present invention or an equivalent scope thereof.
For example, in the above-described embodiment, an example in which the low temperature coloring layer 9 is disposed on the substrate 5 side as illustrated in FIG. 1 is illustrated. However, the low temperature coloring layer 9 includes the medium temperature coloring layer 13 and the high temperature coloring layer as illustrated in FIG. You may arrange | position between the layers 17. Further, the low temperature coloring layer 9 may be disposed on the protective layer 19 side as shown in FIG.

  Further, in the above-described embodiment, only the low temperature color development / color development suppression capsule 21 of the low temperature color development layer 9 has a double capsule structure, but the medium temperature color development capsule 25 of the medium temperature color development layer 13 has a double capsule structure shown in FIG. May be.

  In the above-described embodiment, the case where recording is performed by coloring the recording sheet in three colors has been exemplified. However, recording may be performed by coloring the recording sheet in four colors or more. For example, black may be added to three colors of yellow, cyan, and magenta to develop a recording sheet with four colors, or light cyan and light magenta may be added to develop a recording sheet with five colors.

  In the above-described embodiment, the recording sheet is exemplified as the heat-sensitive recording medium of the present invention, but the shape of the heat-sensitive recording medium of the present invention may be other than the sheet shape.

  The present invention is applicable to a system for recording on a thermal recording medium.

FIG. 1 is a configuration diagram of a recording sheet according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining the configuration of the low-temperature color development / color development inhibiting capsule shown in FIG. FIG. 3 is a diagram for explaining the characteristics of the low-temperature coloring capsule, the inner capsule, the medium-temperature coloring capsule, and the high-temperature coloring capsule according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining the characteristics of the high-temperature coloring capsule, the low-temperature coloring capsule, and the low-temperature coloring suppression capsule in the recording sheet shown in FIG. FIG. 4 is a diagram for explaining the coloring and fixing principles of the low temperature coloring / coloring inhibiting capsule shown in FIGS. 1 and 2. FIG. 6 is a diagram for explaining the printer according to the first embodiment of the invention. FIG. 7 is a flowchart for explaining the image forming operation of the printer according to the first embodiment of the present invention. FIG. 8 is a view for explaining the characteristics of the inner capsule of the low temperature coloring / coloring inhibiting capsule of the second embodiment of the present invention. FIG. 9 is a diagram for explaining a thermal head of a printer that generates an image on a recording sheet according to the second embodiment of the present invention. FIG. 10 is a diagram for explaining a first modification of the recording sheet shown in FIG. FIG. 11 is a diagram for explaining a second modification of the recording sheet shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,110 ... Recording sheet, 5 ... Base material, 9 ... Low temperature coloring layer, 11 ... Thermal barrier layer, 13 ... Medium temperature coloring layer, 15 ... Thermal barrier layer, 17 ... High temperature coloring layer, 19 ... Protection layer, 21, 121 ··· Low temperature coloration / coloration inhibition capsule, 25 · Medium temperature coloration capsule, 27 · High temperature coloration capsule · 31 · Low temperature coloration capsule · 33 and 133 · Inner capsule · 37 · Outer capsule · 39 · Low temperature coloration inhibitor · 40 · Printer, 41 ... sheet storage case, 43 ... sheet feed roller, 45,445 ... thermal head, 47 ... platen roller, 51 ... control section

Claims (11)

A coloring element that develops color at a first temperature;
An inner capsule that encapsulates the color-developing element and has a capsule wall in a permeation state or a destruction state when the second temperature is higher than the first temperature or when a predetermined pressure is applied;
A color-forming capsule having the inner capsule and an outer capsule containing a color-depressing agent that suppresses color development of the color-developing element. When the first coloring element that develops color at the first temperature and the first coloring element are included and the second temperature is higher than the first temperature, or when a predetermined pressure is applied, A color developing capsule having an inner capsule in which the capsule wall is in a permeation state or a broken state, and an outer capsule containing the inner capsule and a color development inhibitor that suppresses the color development of the first color development element;
A thermosensitive recording medium comprising: a second coloring element that develops color at a third temperature higher than the second temperature. The first coloring element develops color on condition that the first temperature state is in a first time,
The thermal recording medium according to claim 2, wherein the second coloring element develops a color on condition that the third temperature is in a second time shorter than the first time. A third color forming element that develops a color on condition that a fourth time higher than the third temperature is in a third time shorter than the second time;
Placing the coloring capsule in the first coloring layer;
Disposing the second coloring element in the second coloring layer;
Placing the third coloring element in a third coloring layer;
The heat-sensitive recording medium according to claim 3, wherein the first coloring layer, the second coloring layer, and the third coloring layer are laminated on a substrate. The coloring element is an element that emits a material contained in the coloring element outside the coloring element and reacts with a substance outside the coloring element, or a material outside the coloring element in the coloring element. The thermal recording medium according to any one of claims 2 to 4, wherein the thermal recording medium is an element that flows into the coloring element and reacts with a substance in the coloring element to develop a color. The color development inhibitor is
Change the chemical structure of one or more of the electron-donating dye precursor, electron-accepting developer, basic substance, or acidic substance that is the material of the coloring element so as not to cause a coloring reaction. function,
The dye can be formed by changing the chemical structure of one or more of the electron-donating dye precursor, electron-accepting developer, basic substance, or acidic substance that is the material of the color-developing element. 3. A function of preventing color formation without being generated, or a function of suppressing a color reaction by reducing the permeability by changing the material permeability of the wall of the microcapsule encapsulating the material of the color developing element. 6. The thermal recording medium according to any one of 5 above. A thermal head for thermally recording an image on a thermal recording medium;
A low-temperature coloring process for controlling the thermal head to form an image on the thermal recording medium at a low-temperature coloring temperature; and a low-temperature coloring of the thermal recording medium at a coloring suppression temperature higher than the low-temperature coloring temperature after the low-temperature coloring process. Controlling the thermal head to control the thermal head so as to suppress, and controlling the thermal head so that an image is formed on the thermal recording medium at a high temperature coloring temperature higher than the coloring inhibition temperature after the low temperature coloring inhibition processing. An image forming apparatus comprising: a control unit that performs high-temperature color development processing. A thermal head for thermally recording an image on a thermal recording medium;
A pressurizing means for applying a pressure for suppressing the low-temperature coloring function of the thermal recording medium;
Controlling the thermal head so as to form an image on the thermal recording medium at a low temperature coloring temperature, and controlling the pressurizing means so as to apply the pressure to the thermal recording medium after the low temperature coloring process. Control means for performing low-temperature color development suppression processing and high-temperature color development processing for controlling the thermal head so as to form an image on the thermal recording medium at a high temperature color development temperature higher than the color development suppression temperature after the low-temperature color development suppression processing. An image forming apparatus. The image forming apparatus according to claim 8, wherein the thermal head and the pressure unit are integrally configured, and the pressure is applied by a heating surface of the thermal head that is in contact with the thermal recording medium. A first step of forming an image on a thermal recording medium by heating at a low color developing temperature;
A second step of suppressing low temperature color development of the thermal recording medium by heating at a color development suppression temperature higher than the low temperature color development temperature after the first step;
And a third step of forming an image on the thermal recording medium by heating at a high color development temperature higher than the color development suppression temperature after the second step. A first step of forming an image on a thermal recording medium by heating at a low color developing temperature;
A second step of applying a predetermined pressure to the thermal recording medium after the first step to suppress low-temperature color development of the thermal recording medium;
And a third step of forming an image on the thermal recording medium by heating at a high color development temperature higher than the color development suppression temperature after the second step.

Images