JP2000330321A - Temperature sensitive discolorable dry toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensitive discolorable dry toner which can very effectively function in the formation of a confidential document by incorporating a thermally discolorable pigment having the form of microcapsules of a non-circular cross-sectional shape obtained by microencapsulating a specified reversibly and thermally discolorable composition. SOLUTION: The temperature sensitive discolorable dry toner contains a thermally discolorable pigment 1 having the form of microcapsules of a non- circular cross-sectional shape obtained by microencapsulating a reversibly and thermally discolorable composition 11 containing an electron donative coloring organic compound, an electron accepting compound and a reaction medium which determines the temperature at which the coloring reaction of both the compounds takes place as essential three components. The thermally discolorable pigment 1 preferably has 0.5-15.0 μm average particle diameter [((major axis size)+(minor axis size))/2]. The weight ratio between the reversibly and thermally discolorable composition 11 and a wall membrane 12 is preferably 7:1 to 1:1. The thermally discolorable pigment 1 preferably has a recess 13 in at least part of the outer surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermochromic dry toner. In detail, a color can be formed or erased by a temperature change to form a primary copy image that can be read only in a specific temperature range. Further, by specifying the erase temperature, it is possible to prevent re-copying by an electronic copying machine or the like. Also relates to a thermochromic dry toner that functions effectively.

[0002]

2. Description of the Related Art Several attempts to incorporate a thermochromic material into a toner have been disclosed. For example, as a means for preventing re-copying by an electronic copying machine or the like, a primary copy image which is decolored in the above-mentioned elevated temperature state by utilizing the temperature of a glass plate of a document table by heat at the time of exposure during use of the copying machine. (Japanese Patent Publication No. Hei 3-57472, Japanese Patent Publication No. Hei 7-57) have disclosed a proposal regarding a thermochromic dry toner for forming a toner.
No. 50335).

[0003]

When a copy is formed by applying a dry toner, there is an image fixing step by passing a heat fixing roller in a copying machine. Must endure. Furthermore, a high heat and high pressure load is inevitable in a step of melting and kneading the thermochromic material and the binder resin during the preparation of the toner, a pulverization step, and the like. Therefore, a durable thermochromic dry toner having both heat resistance and pressure resistance is required, but the above-mentioned conventional proposal does not necessarily satisfy these requirements. In view of the above situation, the present inventors have conducted intensive studies and found that a thermochromic pigment in a microcapsule form having a specific cross-sectional shape is extremely effective as a component of a thermochromic toner satisfying the above requirements. Completed the invention. As the thermochromic pigment, by applying three kinds of thermochromic pigments having different coloring and decoloring behavior according to the purpose, a visible or invisible image can be formed in a normal state, and further, the decolorization temperature is specified. Thus, it is possible to provide a primary copy which cannot be reproduced. Further, by applying a thermochromic pigment of a color storage type capable of alternately storing and retaining a color-developed state or a decolored state in a specific temperature range as a thermochromic pigment, it is extremely effective in preparing a confidential document. It is an object of the present invention to provide a thermochromic dry toner that forms a functional primary copy.

[0004]

The thermochromic dry toner of the present invention comprises (a) an electron-donating color-forming organic compound;
A microcapsule having a non-circular cross-sectional shape in which a microcapsule contains an electron-accepting compound and (c) a reversible thermochromic composition containing three essential components, which are reaction media for determining the temperature at which a color reaction of the two occurs. It is required to contain a thermochromic pigment in a form. Further, the thermochromic pigment has an average particle diameter [(major axis + minor axis) / 2] of 0.5 μm to 15 μm.
0 μm, moreover, it is a microcapsule type thermochromic pigment in which the reversible thermochromic composition / wall film = 7/1 to 1/1 (weight ratio), and further, thermochromic The coloring pigment is a pigment having a depression on at least a part of the outer surface.Furthermore, the reversible thermochromic composition is decolorized by heating from a color-developing state, and is heated and cooled by cooling from a decoloring state. The color type (A), the color storage state (B) that alternately stores and retains the color development state or the color erasure state in a specific temperature range, or the color development by heating from the color erasure state, and the temperature drop from the color development state It is required to be selected from any of the heating and coloring types (C) for decoloring.

The reversible thermochromic composition includes (a)
It is conventionally known, including an electron-donating color-forming organic compound, (b) an electron-accepting compound for coloring the compound, and (c) a reaction medium for determining a temperature at which a color reaction between the two occurs. Are effective. Specifically, Japanese Patent Publication No. Sho 51-44706 and Japanese Patent Publication No. Sho Sho 5
JP-A-1-44707, JP-B-1-29398 and the like can be used. The color changes before and after a predetermined temperature (discoloration point) as a boundary, exhibits a decolored state in a temperature range higher than the color change point, and a decolored state in a temperature range lower than the color change point. Only one particular state can exist. That is, the other state is maintained while the heat or cold required to develop the state is applied, but returns to the state exhibited in the normal temperature range when the application of the heat or cold is stopped, hysteresis. Characteristics with relatively small width (ΔH
_(A = 1 to 7 ° C.), and particularly a system in which ΔH _A is 3 ° C. or less [Japanese Patent Publication No. 1-293].
No. 98, a fatty acid ester having a ΔT value (melting point-cloud point) of 3 ° C. or less is used as the component (c)]. It shows heat decoloring properties and can be applied effectively according to the purpose (see FIG. 5).

In addition, Japanese Patent Publication No. 4-171 proposed by the present applicant.
No. 54, JP-A-7-179777, JP-A-7-179777
-33997 discloses a large hysteresis characteristic described in JP-A 8-39936 Patent Publication (ΔH _B = 8~
50 ° C.), that is, the shape of the curve plotting the change in the coloring density due to the temperature change is different from the case where the temperature is increased from a temperature lower than the color change temperature range and conversely, the temperature is decreased from a temperature higher than the color change temperature range. The color changes along a route that is significantly different from the case where the color changes in a low-temperature range of t ₁ or less, or the decoloration state in a high-temperature range of t ₄ or more, occurs in a specific temperature range (between t _{2 and} t ₃ ). A color storage-maintaining thermochromic composition (B) capable of storing and storing in a temperature range (substantially two-phase holding temperature range) can also be applied (see FIG. 6). (For example, 15 to 35 ° C.) is generally used, but is not specified in the above temperature range.

[0007] Further, as a composition of the heat coloring type (C), the present applicant proposes (Japanese Patent Application Nos. 9-316294 and 9-121620,
Japanese Patent Application Laid-Open No. H11-5973) discloses (b) a system to which a specific alkoxyphenol compound having a linear or branched alkyl group having 3 to 18 carbon atoms is applied as the electron accepting compound. By applying the heating coloring type, an image which is in a decolored state under normal conditions is heated (for example,
T ₁ is colored state and without by any temperature) of more than 35 ° C., can be obtained primary copy of legible.

[0008] By selecting and applying the above-mentioned three (A, B, C) thermochromic compositions according to the purpose, it is possible to obtain various temperature-dependent primary copies. Here, for the purpose of preventing re-copying of the primary copy, if the image of the primary copy exhibits a decolored state at the surface temperature of the glass plate of the platen of the copying machine at the time of copying. ,
Obtaining a legible secondary copy is avoided. In an electronic copying machine, the surface temperature of the glass plate of the platen is affected by the ambient temperature and the operating time of continuous copying due to the heat during exposure or the heat of the planar heating element provided on the platen cover. However, the temperature is in a state of being raised to about 30 to 45 ° C. Therefore,
If a thermochromic composition exhibiting a decolored state at 30 to 45 ° C. is applied, a thermochromic dry toner satisfying the re-copying prevention function can be constituted.

[0009] To be more specific, a primary color toner (A) formed by a toner containing a thermochromic pigment which develops a color at a temperature lower than 30 ° C and decolorizes at a temperature higher than 30 ° C. The image of the copy is legible, for example, at room temperature of 25 ° C., but a legible secondary copy is not obtained by re-copying. Further, in a color memory holding type (B) system formed of a toner containing a thermochromic pigment that decolorizes at 40 ° C. or more, when the temperature on the glass plate is 40 ° C. or more, it is readable. The next copy is not available. Further, in the system formed by a toner containing a thermochromic pigment which forms a color by heating at 45 ° C. or more of the heating color forming type (C), when the temperature on the glass plate is 40 ° C. The next copy is not available.

The present invention relates to a microcapsule-shaped pigment in which the above-described reversible thermochromic composition is encapsulated in a microcapsule, the pigment having a non-circular cross-sectional shape, more specifically, at least a part of the outer surface. The requirement is to apply a non-circular thermochromic pigment having depressions (see FIGS. 1 to 4). Since the thermochromic pigment is a flat pigment having a non-circular shape, it is not easily destroyed by a pressure or heat load in a toner preparation process or a heat fixing process. It is easy to orient thinly and densely on the surface of the copy paper, and it can be appropriately elastically deformed and stress relieved when the pressure of the roll is applied in the heat fixing process. In the heating process, the wall film is elastically deformed in response to the thermal expansion and contraction of the capsule, and it has the effect of suppressing the destruction of the capsule wall film, and protects the reversible thermochromic composition contained therein to achieve the desired heat. It functions effectively as a tough capsule-shaped thermochromic pigment that retains the color changing function.

The thermochromic pigment has an average particle diameter [(major axis + minor axis) / 2] in the range of 0.5 μm to 20 μm, preferably 0.5 to 15 μm, more preferably 1 to 5 μm.
Is desirably within the range. The sensitivity of discoloration, endurance,
The above range is effective in terms of processing suitability and the like. If it is less than 0.5 μm, even if a thermochromic pigment microencapsulated in a state of being suspended in an aqueous medium can be obtained, isolation of the encapsulated pigment by means such as filtration or centrifugation is difficult, and strength is high. Is insufficient. On the other hand, the average particle diameter is
In a system exceeding m, the practical upper limit is that the particle size of the toner itself formed by combining with the binder resin is about 25 μm or less, so that it is difficult to satisfy practicality.

In the encapsulated thermochromic pigment of the present invention, the reversible thermochromic composition / wall film = 7/1 to 1
/ 1 (weight ratio). If the ratio of the thermochromic composition is larger than the above range, the thickness of the wall film becomes too thin, and the protective function of the contained thermochromic composition is reduced. On the other hand, if the ratio of the wall film is larger than the above range, the color density must be reduced, which is not preferable.

As a means for encapsulating the reversible thermochromic composition in a capsule, known encapsulation methods such as an interfacial polymerization method, an interfacial polycondensation method, an in situ method and a coacervate method are applied. In order to obtain a thermochromic pigment having a particle distribution satisfying the above requirements, an interfacial polymerization method or an interfacial polycondensation method in which aggregation and coalescence hardly occur are preferably used. Further, after completion of the encapsulation, the capsule suspension is diluted with water as required, and unnecessary coarse particles are removed by filtering off impurities and coarse particles using filters. Filters include stainless steel mesh,
An industrial filter medium such as a synthetic resin monofilament net, a synthetic resin multifilament net, an ultrafine fiber filter, a cotton cloth, a nonwoven fabric, a needle felt, and a filter paper is used alone or in an appropriate combination. In addition, in order to maintain a preferable particle size range of the thermochromic pigment described above, or to suppress generation of coarse particles, and to maintain an appropriate particle size distribution, a water-soluble acrylic resin, polyvinyl alcohol, ethylene-anhydrous. Water-soluble polymers such as maleic acid copolymer resin, gum arabic, hydroxypropylcellulose, sodium alginate,
It is effective to use a water-soluble cellulosic derivative such as methylcellulose, a water-soluble protein such as gelatin and albumin, a surfactant, or an emulsifier.

The thermochromic pigment dispersion from which the coarse particles have been filtered is used for centrifugation or filtration to further isolate the thermochromic pigment, whereby the water content is 30% by weight to 50% by weight.
Is obtained. The water content of the water-containing thermochromic pigment can be removed by a flushing method, a decompression method, or other means.However, the process of blending with the binder resin component or the like, or the suspension polymerization of the binder resin component, Can be removed during the formation process.

The dry toner of the present invention employs a toner component such as a general-purpose binder resin, and is formed by the same means as in the prior art. The content of the thermochromic pigment in the dry toner of the present invention is 0.5 to 50% by weight, preferably 1 to 50% by weight, and more preferably 2 to 30% by weight. If it is less than 0.5% by weight, the color density at the time of color development is insufficient, and if it exceeds 50% by weight, the ratio of the binder resin is too small, and the fixability of the toner is impaired. The particle size of the dry toner is 5 to 30 μm, preferably 15 to 25 μm. If the particle diameter is 5 μm or less, the fluidity of the toner is deteriorated, and problems such as background staining tend to occur. On the other hand, 25μ
Above m, the cutting of the image tends to be poor.

As the binder resin, all resins conventionally used widely as electrophotographic toners are effective. For example, styrene resins (including a polymer or a copolymer containing styrene or a styrene substituent) are used. , Vinyl chloride resin, rosin-modified maleic resin, chlorinated paraffin, polychlorinated paraffin, phenolic resin, epoxy resin, polyester resin, polyamide, polyacrylic acid resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, Ketone resin, ethylene-
Ethyl acrylate copolymer, xylene resin, polyvinyl butyral, polyurea resin and the like,
These may be used alone or in combination of two or more. When the above-described binder resin is used as the base particles, the binder resin may be one obtained by granulation polymerization by a suspension polymerization method or the like.

As the monomer, any one can be used as long as it is a polymerizable monomer. Conventionally known styrene monomers, ethylenically unsaturated monoolefins, vinyl halides, vinyl esters , Α-methylene aliphatic monocarboxylic acid esters, acrylic acid or methacrylic acid derivatives, vinyl ethers, vinyl ketones, N
-Vinyl compounds, vinyl naphthalenes, and other monomers, and these monomers can be used alone or in combination of two or more. Further, as a specific example, as a monomer for obtaining a polyester resin, a general-purpose dibasic acid can be mentioned, and it can be used in combination with glycols. As a monomer for obtaining a polyamide resin, caprolactam, dibasic Combinations of acids and diamines, polyurethane resins include combinations of diisocyanates and diamines, and epoxy resins include combinations of amines and diepoxy compounds.

As the polymerization initiator, peroxides,
Azo-based conventionally known ones are applied, and examples of suspension stabilizers include water-soluble polymer substances such as gelatin, starch, and polyvinyl alcohol, and difficulties such as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, and calcium phosphate. Inorganic polymer substances such as soluble salts, talc, clay, silicic acid, diatomaceous earth and metal compounds are applied.

In the dry toner of the present invention, in a system to which a magnetic carrier is applied, as the magnetic carrier,
Metals such as iron, cobalt, and nickel, alloys thereof, and magnetic powders such as metal oxides are added to the binder resin for use. If necessary, a charge controlling agent such as a surfactant, a quaternary ammonium salt, or a gold-containing dye having an organic complex structure can be used. Also, the purpose is to improve the fluidity and preservability of the developer, or to prevent the filming of the toner on the photosensitive material,
Long-chain fatty acids such as stearic acid and esters thereof, for the purpose of improving toner cleaning properties, etc.
An amide, a metal salt, or a fine powder of molybdenum disulfide, graphite, boron nitride, silica, silicon carbide, aluminum oxide, or the like, a fine powder of a fluororesin, or conductivity may be added. Further, in combination with the toner binder resin, an anti-adhesive agent, for example, a fatty acid metal salt such as cadmium stearate, barium stearate, zinc oleate, cobalt palmitate, polyethylene or polypropylene having a relatively low molecular weight, higher fatty acid, paraffin And other waxes can be applied.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermochromic dry toner of the present invention is prepared by preparing a microencapsulated thermochromic pigment having a non-circular cross-sectional shape (exemplified in FIGS. 1 to 4), or a thermochromic pigment having such a shape. It is formed by kneading a thermochromic pigment in which a thermochromic pigment is mixed with a general-purpose toner binder resin and other components by general-purpose means, and then obtaining a predetermined particle size.

[0021]

Examples are shown below. The parts in the examples are parts by weight.

Example 1 Preparation of thermochromic pigment (a) 2- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-
Il) -4-azaphthalide 5 parts, (b) 1,1-octylidenebisphenol 10 parts, (c) butyl stearate 50 parts of a reversible thermochromic composition is uniformly dissolved,
Aromatic isocyanate prepolymer 30 as wall material
And 30 parts of ethyl acetate, and the solution uniformly dissolved at 70 ° C. was emulsified at 70 ° C. in a 15% aqueous gelatin solution. Here, the reversible thermochromic composition / wall film material = 2.2 / 1.0
(Weight ratio). At the time of emulsification, the stirring power of the homomixer is adjusted so that 90 cumulative volume% or more of all the particles are distributed in the particle diameter of 2.0 to 3.0 μm,
After the emulsification, stirring was continued for about 1 hour, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued for 5 hours to obtain a suspension containing a thermochromic pigment having an average particle diameter of 2.5 μm. Was. After the reaction, the obtained microcapsule suspension was diluted with 5 times the amount of water, and then filtered through a 400 Mesh stainless steel filter. The thermochromic pigment was isolated by centrifugation, and the water content was about 35%. By weight, a thermochromic pigment was obtained.
The thermochromic pigment is blue at 20 ° C. (t ₁ ) or less,
It has a heat-decoloring type thermochromic property which becomes colorless at a temperature of not less than ° C. (t ₄ ) (see FIG. 5). The obtained thermochromic pigment is subjected to a centrifugal sedimentation-type automatic particle size distribution analyzer (CAPA-3, manufactured by Darijo Seisakusho).
00), as a result of measuring the particle size distribution, when the particle size is D, the relationship between the particle size and the occupied volume% (shown in parentheses) is D <0.5 μm (0%), 0.5 ≦ D <2.0 (1
5%), 2.0 ≦ D <3.0 (20%), 3.0 ≦ D <
4.0 (38%), 4.0 ≦ D <5.0 (18%), D
> 5.0 (9%), and a particle size distribution with an average particle size of 3.6 μm was obtained. Further, 91% of the thermochromic pigment is 0.5 μm or more.
It was confirmed that it was in the range of 5.0 μm.

Preparation of Toner A mixture of 170 parts of a styrene-acrylic acid copolymer emulsion (solid content: about 50%), 12 parts of an olefinic dispersion (solid content: 40%), and 15 parts of the thermochromic pigment is conventionally known. Dehydration and drying by the flushing method of
After classification, a thermosensitive dry toner having a particle size of 10 to 25 μm was obtained.

Characteristics of Primary Copy The above thermochromic toner is loaded into an electronic copying machine, a document on which a conventional non-thermochromic image is formed is copied, and a thermochromic primary copy (room temperature below 20 ° C.) Below, read as a blue image). When the primary copy was re-copied by a copier equipped with a general-purpose toner or a thermochromic toner, no secondary copy having a legible image was obtained. At this time, the temperature of the surface of the glass plate of the platen of the copying machine was about 35 ° C.

Example 2 Preparation of thermochromic pigment 3 parts of 6- (ethylisobutylamino) benzo [a] fluorane, 8 parts of 2,2-isobutylidenebisphenol,
A reversible thermochromic composition comprising 25 parts of cetyl alcohol and 25 parts of stearyl caprate is heated and dissolved, and 10 parts of an epoxy resin and 40 parts of ethyl acetate are added as a wall film material,
The solution uniformly dissolved at 70 ° C. was emulsified with an aqueous protective colloid medium. Here, reversible thermochromic composition / wall film material = 6.
1 / 1.0 (weight ratio). During emulsification, the particle size is 2.
The stirring power of the homomixer was adjusted so as to be distributed in the range of 0 to 3.0 μm. After emulsification, 5 parts of a water-soluble aliphatic modified amine was added, and stirring was continued for another 5 hours. After the reaction, the obtained microcapsule suspension was diluted with 5 times the amount of water, and 400 Me
After filtering through a sh stainless steel filter, the thermochromic pigment was isolated by centrifugation to obtain a thermochromic pigment having a water content of 35% by weight. The thermochromic pigment is 28
It has a thermo-discoloring property of a heat-decoloring type, which is pink when the temperature is lower than ° C (t ₁ ) and colorless when the temperature is higher than 35 ° C (t ₄ ) (see FIG. 5).

Preparation of Toner 50 parts of a styrene / 2-ethylhexyl acrylate / normal butyl methacrylate copolymer, 30 parts of a polyester resin, and 10 parts of a dehydration product of the thermochromic pigment were heated and melt-mixed in a hot roll mill and cooled to room temperature. Thereafter, the obtained melt is pulverized with a pulverizer, and classified to have a particle size of 5 to 15 μm.
Was obtained.

Characteristics of Primary Copy The above thermochromic toner is loaded into an electronic copying machine, a document on which a conventional non-thermochromic image is formed is copied, and a thermochromic primary copy (room temperature below 28 ° C.) Below it is interpreted as a pink image). When the primary copy was re-copied, a secondary copy having a legible image was not obtained. At this time, the temperature of the surface of the glass plate of the platen of the copying machine was about 38 ° C.

Example 3 Preparation of thermochromic pigment (A) 1.0 part of 1,2-benz-6- (N-ethyl-N-isobutylamino) fluoran, (B) 1,1-bis- (4 -Hydroxyphenyl) -n-ethane 6.0 parts,
(C) A reversible thermochromic composition obtained by heating and dissolving 5.0 parts of stearyl alcohol, 20.0 parts of cetyl alcohol, and 25.0 parts of stearyl caprate at 120 ° C. to form a homogeneous compatibilized solution is obtained by adding epoxy After mixing with a mixed solution of 10 parts of the resin, the mixture is dropped into 100 parts of a 10% gelatin solution, and the mixture is stirred so as to become fine droplets. A solution prepared by dissolving 5.0 parts of a separately prepared curing agent (Epicure U, an amine adduct of an epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.) in 45.0 parts of water was blended with the above mixed solution. The solution was kept at 80 ° C. and stirred for about 5 hours to obtain a stock solution of microcapsules. Next, a microencapsulated thermochromic pigment was obtained by centrifugation. The thermochromic pigment,
Below 28 ° C. (t ₁ ), it develops pink color and 32 ° C.
Above (t ₄ ), it has a heat-decoloring type thermochromic property which becomes colorless (see FIG. 5).

Preparation of Toner 20 parts of the thermochromic pigment dehydrated product and toluene 1000
Of a polyester resin, and 8 parts of a charge control agent, were spray-dried with a spray drier to obtain a positively-charged thermochromic dry toner having a particle diameter of 5 to 20 μm. Further, the thermochromic dry toner was mixed with an iron powder carrier to prepare a developer.

Characteristics of Primary Copy The above thermochromic toner is loaded into an electronic copying machine, a document on which a conventional non-thermochromic image is formed is copied, and a thermochromic primary copy (room temperature below 28 ° C.) Below it is interpreted as a pink image). When the primary copy was re-copied, a secondary copy having a legible image was not obtained. At this time, the temperature of the surface of the glass plate of the platen of the copying machine was about 38 ° C.

Example 4 Preparation of thermochromic pigment (a) 3- [2-ethoxy-4- (N-ethylanilino) phenyl] -3- (1-ethyl-2-methylindol-3-yl) -4 -1.5 parts of azaphthalide, (b)
6.0 parts of pn-nonyloxyphenol, 4.0 parts of pn-octyloxyphenol, and (c) 30.0 parts of n-docosane were used in Examples 1 (a), (b) and (c). ) Was applied in place of each component, and a thermochromic pigment was obtained in the same manner as in Example 1. The thermochromic pigment is in a decolored state (colorless) at a room temperature of 25 ° C., and starts heating to 33 ° C. (T ₁ ).
Color development starts at around 43 ° C. (T ₂ ), changes to a blue color at 43 ° C. (T ₂ ), and then maintains the color developing state up to 32 ° C. (T ₃ ) in the course of cooling.
It has a heat-coloring-type thermochromic property in which the color is completely erased at a temperature of ₄ ° C. (T ₄ ) (see FIG. 7).

Preparation of Toner A positively chargeable thermosensitive discolorable dry toner having a particle size of 5 to 15 μm was obtained in the same manner as in Example 1 by using the dehydrated thermochromic pigment, and then dried with an iron powder carrier. This was mixed to form a developer.

Characteristics of the primary copy The image of the primary copy formed by applying the thermochromic dry toner is not legible at room temperature of 25 ° C, but at 43 ° C.
It was legible when heated to the above temperature. When the surface temperature of the glass plate of the platen of the copying machine is around 30 ° C., the image of the primary copy is in an erased state, and a readable secondary copy cannot be obtained.

Example 5 Preparation of thermochromic pigment (a) 3.0 parts of 3-dibutylamino-6-methyl-7-anilinofluoran, (b) 2,2-bis (4-hydroxyphenyl) propane 8.0 parts and (c) 50.0 parts of n-laurophenone were added to (a), (b),
By substituting each component of (c), and by means similar to Example 1, a color-memorizing thermochromic pigment having an average particle diameter of 5 μm and having a water content of about 40% by weight and changing from black to colorless was obtained. The color-memorizing thermochromic pigment begins to develop its color at 4 ° C. or lower (t ₂ ), becomes completely colored at -6 ° C. or lower (t ₁ ), and starts erasing at 35 ° C. or higher (t ₁ ). t
₃ ) When the temperature exceeds 43 ° C., the color is completely erased (t)
₄ ), discoloration behavior as shown in FIG. The temperature range of the t ₂ ~t _3, even after removal of the cold required for the color development described above colored state is stored and held, whereas, even after removal of the application of heat required for decoloring vanishing The color state is stored and stored, and the color development state or the decolored state has a color storage and maintenance type thermochromic characteristic that is stored and maintained alternately in the temperature range (see FIG. 6).

Preparation of Toner A positively chargeable thermochromic dry toner having a particle size of 5 to 20 μm was obtained in the same manner as in Example 3, and then mixed with an iron powder carrier to obtain a developer.

Characteristics of the primary copy The thermochromic dry toner is loaded into an electronic copying machine, and the original on which a non-thermochromic image is formed as described in the above embodiment is copied to obtain a thermochromic primary copy. Obtained. When the copy was cooled to -6 ° C or less by cold spraying, the image was colored and became legible, and was kept legible at room temperature below 35 ° C, while the image disappeared when heated above 43 ° C. The color became unreadable and the image did not develop color unless cooled to 4 ° C. or less. When the primary copy in the colored state was placed on a glass plate of a copying machine and subjected to re-copying, a readable re-copy was obtained when the temperature of the glass plate was lower than 35 ° C. When the surface temperature of the plate was raised to 43 ° C. or higher, the image was erased and no legible secondary copy was obtained.

Example 6 Preparation of Thermochromic Pigment The procedure of Example 5 was repeated, except that the component (c) was replaced with n-decanophenone.
A color-memorizing thermochromic pigment having an average particle size of 5 μm and changing from black to colorless was obtained. The color memory thermochromic pigment is-
When the temperature falls below 12 ° C., the color begins to develop (t ₂ ). When the temperature falls below −23 ° C., the color develops completely (t ₁ ).
At this point, the color starts to be erased (t ₃ ), and when the temperature exceeds 36 ° C., the color is completely erased (t ₄ ). The temperature range of the t ₂ ~t _3, even after removal of the cold required for the color development described above colored state is stored and held, whereas, even after removal of the application of heat required for decoloring vanishing The color state is stored and held, and the color-developed state or the decolored state alternately has a color storage-maintaining thermochromic characteristic that is stored and held in the temperature range (see FIG. 6).

Preparation of Toner A positively chargeable thermochromic dry toner having a particle size of 5 to 20 μm was obtained in the same manner as in Example 3, and then mixed with an iron powder carrier to prepare a developer.

Characteristics of Primary Copy The above thermosensitive color-changing dry toner was loaded into an electronic copying machine and a confidential document was copied to obtain a thermochromic primary copy. When the copy was cooled to -23 ° C or less by cold spraying, the image was colored and became legible, and was kept legible at room temperature below 26 ° C, while heating above 36 ° C erased the image. The color became unreadable, and a clearly legible image did not appear unless cooled below -23 ° C. The primary copy in the color-developed state was placed on a glass plate of a copying machine and subjected to re-copying. As a result, a legible secondary copy was not obtained. At this time, the surface temperature of the glass plate was about 36 ° C.

Example 7 Preparation of thermochromic pigment (a) 3-dibutylamino-6-methyl-7-anilinofluoran (3 parts), (b) 1,1-bis (4-hydroxyphenyl) -3- Example 1 was replaced by the three components of methyl butane 8 parts and (c) cyclohexylmethyl stearate 50 parts with the components (a), (b) and (c) of Example 1.
In the same manner as in the above, a color memory thermochromic pigment having an average particle diameter of 5 μm and changing from black to colorless with a water content of about 40% by weight was obtained. The color memory pigment has a discoloration behavior as shown in FIG. 6 (t ₁ : 13 ° C., t ₂ : 15 ° C., t ₃ : 35 ° C., t ₄ :
38 ° C.), and in the temperature range of t ₂ and t ₃ , the color development state is stored and retained even after the cooling (13 ° C. or less) required for the color development is removed, while the color development is required. The decolored state is retained even after removing the application of heat (above 38 ° C.). The color-developed state or the decolored state has a color storage-maintaining thermochromic characteristic that is stored and maintained alternately (see FIG. 6).

Preparation of Toner A positively chargeable thermosensitive dry toner having a particle size of 5 to 20 μm was obtained in the same manner as in Example 3, and then mixed with an iron powder carrier to obtain a developer.

Characteristics of Primary Copy The above developer is loaded into an electronic copying machine to copy a confidential document.
A thermochromic primary copy was obtained. When the primary copy was cooled to 13 ° C. or less, the image was colored and became legible,
At room temperature below 5 ° C., it remains legible, while
When heated above 38 ° C., the image was erased and became unreadable, and the image did not develop color unless cooled below 15 ° C. When the primary copy in the colored state was placed on a glass plate of a copying machine and subjected to re-copying, a readable re-copy was obtained when the temperature of the glass plate was lower than 35 ° C. When the surface temperature of the plate was raised to 40 ° C. or higher, the image was erased and no legible secondary copy was obtained.

[0043]

The thermochromic dry toner according to the present invention is a thermochromic element in which the thermochromic composition is a pigment having a non-circular cross-sectional shape in which the thermochromic composition is encapsulated in microcapsules. It functions as a toner that withstands the load of heat and pressure during the toner preparation process or the image fixing process by blending and that effectively exhibits the intended thermochromic function. The primary copy formed by using the thermochromic dry toner can be used as a temperature-dependent print which is readable or decolorable in a specific temperature range due to a change in environmental temperature or application of heat or cold. In systems using thermochromic pigments that are decolorized at the surface temperature of the glass platen of the platen of the copier at the time of copying, it is not possible to obtain readable re-copied products, so reprinting confidential documents It can function as a copy prevention toner.
In a system to which a thermochromic pigment of a color memory retention type is applied, particularly in a system to which a thermochromic pigment which develops a color at 0 ° C or less is applied, the image of the primary copy may be developed and read in a normal state. None, it is extremely effective as a printed matter preventing leakage of important information.

[Brief description of the drawings]

FIG. 1 is an enlarged explanatory view of (a) an external appearance and (b) a cross section showing an example of a thermochromic pigment applied to a thermochromic dry toner of the present invention.

FIG. 2 is an enlarged explanatory view of (a) an appearance and (b) a cross section showing another example of a thermochromic pigment applied to the thermochromic dry toner of the present invention.

FIG. 3 is an enlarged explanatory view of (a) the appearance and (b) a cross section showing another example of the thermochromic pigment applied to the thermochromic dry toner of the present invention.

FIG. 4 is an enlarged explanatory view of (a) an appearance and (b) a cross section showing another example of a thermochromic pigment applied to the thermochromic dry toner of the present invention.

FIG. 5 is a graph showing the discoloration behavior of a heat-decolorable thermochromic composition.

FIG. 6 is a graph showing the color change behavior of a color memory retaining type thermochromic composition.

FIG. 7 is a graph showing the discoloration behavior of a thermochromic composition of a heat coloring type.

[Explanation of symbols]

1 coloring start temperature t ₃ of the thermochromic pigment 11 thermochromic composition 12 wall membrane 13 indentation t ₁ heating decolorizable complete coloring temperature t ₂ heated decolorizable reversible thermochromic composition reversibly thermochromic composition coloring starting temperature T ₂ heating complete decoloring temperature T ₁ of the heating-color forming reversible thermochromic composition of the decoloring starting temperature t ₄ heated decolorizable reversible thermochromic composition of the heat-decolorizable thermochromic composition Complete color development temperature of the color-forming reversible thermochromic composition T ₃ Decolorization starting temperature of the heating color-forming reversible thermochromic composition T ₄ Complete decoloring temperature of the heating color-forming reversible thermochromic composition ΔH _A Heat decoloring type Hysteresis width of reversible thermochromic composition ΔH _B Hysteresis width of color memory-retaining reversible thermochromic composition ΔH _C Hysteresis width of heat-colorable reversible thermochromic composition

Claims (5)

[Claims] (1) an electron-donating color-forming organic compound,
(B) a non-circular cross-sectional shape in which a reversible thermochromic composition containing essential three components comprising an electron accepting compound and (c) a reaction medium for determining the temperature at which a color reaction between the two occurs is contained in a microcapsule; A thermosensitive color-changing dry toner comprising a thermochromic pigment in the form of microcapsules. 2. The thermochromic pigment has an average particle diameter [(long diameter +
2. The thermosensitive dry toner according to claim 1, wherein (short diameter) / 2] is in the range of 0.5 μm to 15.0 μm. 3. Reversible thermochromic composition / wall film = 7/1 to 1
The thermosensitive color-changing dry toner according to claim 1, wherein the thermosensitive pigment is a microcapsule-type thermochromic pigment having a weight ratio of / 1. 4. The thermochromic dry toner according to claim 1, wherein the thermochromic pigment is a pigment having a depression on at least a part of its outer surface. 5. A reversible thermochromic composition, which is decolorized by heating from a color-developing state and changes color by heating from a decolorized state to a specific temperature by changing the color-developed state or decolored state to a specific temperature. 2. The temperature sensing device according to claim 1, wherein the temperature sensing device is selected from any of a color memory holding type that stores and holds in a region, and a heating color developing type that forms a color by heating from a decolored state and returns to a decolored state by lowering the temperature from the colored state. Discolorable dry toner.