JPH0651501A - Microcapsule for forming image - Google Patents

Abstract

(57) [Summary] [Purpose] Photosensitivity to image-receiving paper such as plain paper, on which an image-forming substance is sufficiently fixed and a clear image can be formed without impairing the original texture of the image-receiving paper. Provide microcapsules. [Structure] Photosensitive microcapsules are those in which a core substance composed of an image forming substance such as a pigment, a dye, a dye precursor and a photosensitive substance is encapsulated by a resin, and waxes and the like are fixed in the core substance. Contains accelerators.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming microcapsule used for forming a monochrome or color image.

[0002]

2. Description of the Related Art So-called photosensitive microcapsules in which a dye precursor and a core substance such as a photosensitive substance are enclosed by a wall material such as a resin have been known. In addition, a color copying machine using a photosensitive medium carrying the photosensitive microcapsules has been developed.

In this apparatus, the photosensitive medium is exposed in accordance with image information and the microcapsules are cured to form a chemical latent image on the photosensitive medium. Next, the color developing paper and the photosensitive medium are superposed and pressed, and the microcapsules are destroyed, whereby the chemical latent image is developed and an image is formed on the color developing paper.

However, in this apparatus, a photosensitive medium in which a microcapsule is coated on this substrate is used with a plastic film such as PET (polyethylene terephthalate) as a substrate. Therefore, although the base material does not directly contribute to image formation, it is consumed and discarded together with the microcapsules each time an image is formed. Therefore, this image forming apparatus has a problem that the so-called running cost is high.

Therefore, in order to solve this problem, the present applicants have proposed an apparatus capable of forming an image without discarding the base material by using a photosensitive microcapsule in a particulate form, as disclosed in Japanese Patent Application No. 3-124919. Have applied for.

In this image forming apparatus, powdery microcapsules are dry-coated on an endless belt-shaped support inside the apparatus, and then exposed according to image information. Next, the microcapsules are destroyed by a pressurizing means or the like to release the core substance.

The core material of the microcapsules used in this apparatus is a lipophilic liquid photosensitive material in which a polymerizable monomer such as an acrylate monomer, a photopolymerization initiator and a sensitizer are mixed, and a photosensitive material. It consists of an image-forming substance which is a colorant dispersed therein.

When the core substance is transferred to the image receiving paper,
The core substance penetrates between the fibers of the image receiving paper, and an image is formed by the image forming substance in the core substance.

[0009]

However, since a large amount of liquid photosensitive material is transferred and absorbed together with the image forming substance to the image receiving paper on which the image is formed in the above image forming apparatus, There was a problem that the surface of the image receiving paper becomes transparent and the original texture of the image receiving paper is impaired, or the core substance spreads beyond the pixel size and penetrates into the image receiving paper, making the image unclear. .

In order to solve this problem, it is possible to increase the amount of the image forming substance in the core substance of the microcapsule, reduce the volume of the microcapsule required for image formation, and reduce the amount of the photosensitive substance. Conceivable. However, when such a core substance is used, since the liquid component is small and it does not penetrate into the image receiving paper, the image forming substance is simply attached to the surface of the image receiving paper. That is, the fixing property of the image forming substance on the image receiving paper is insufficient, and the image forming substance on the image receiving paper peels off or moves when the user touches the image forming device during transportation or after outputting, which disturbs the image. It was causing a serious problem.

The present invention has been made in order to solve the above-mentioned problems, and for image receiving paper such as plain paper,
An object of the present invention is to provide a microcapsule for image formation in which an image forming substance is sufficiently fixed and a clear image can be formed without impairing the original texture of the image receiving paper.

[0012]

In order to achieve this object, the microcapsules for image formation of the present invention include an image forming substance such as a pigment, a dye or a dye precursor, and a core substance made of a photosensitive substance made of a resin or the like. It is encapsulated and contains a fixing promoting substance such as wax in the core substance.

[0013]

When the image forming microcapsules of the present invention having the above-mentioned structure are pressed by a pair of pressure rollers and the like,
The microcapsules are deformed or destroyed and the core substance flows out. When this core substance is transferred to the image receiving paper, the fixing substance such as wax contained in the core substance works to fix the core substance on the surface of the image receiving paper. Therefore, the core substance does not spread beyond the pixel size and penetrate into the plane of the image receiving paper.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a photosensitive microcapsule embodying the image forming microcapsule of the present invention. In FIG. 1, a microcapsule 1 is substantially spherical and has a diameter of 3 to 20 μm, and is composed of a wall member 2 made of melamine-formaldehyde resin and having a thickness of 0.01 to 1 μm, and a core substance 3 enclosed in the wall member. There is.

Here, the photosensitive substance is a substance which is polymerized and hardened in response to light, is hydrophobic, is composed of at least a polymerizable substance and a photoinitiator, and optionally contains a sensitizing dye.

Examples of the polymerizable substance include N-vinyl-2-pyrrolidone, bisphenol A diacrylate and methacrylate, tripropylene glycol diacrylate and methacrylate, polyethylene glycol diacrylate and methacrylate, pentaerythritol triacrylate and methacrylate,
Examples include dipentaerythritol hexaacrylate and methacrylate, trimethylolpropane triacrylate and methacrylate, oligoester acrylate and methacrylate, and the like. Further, these polymerizable substances may be used alone or as a mixture of two or more kinds.

The photoinitiator is one which is sensitive to light and initiates the polymerization of the polymerizable substance. For example, benzophenone, benzoylalkyl ethers such as benzoylisopropyl ether, Michler's ketone, metal arene compound,
2,4-diethylthioxanthone and the like can be mentioned.

The sensitizing dye is contained in order to adjust the photosensitive wavelength of the photosensitive substance, and is xanthene-based, coumarin-based, merocyanine-based, thiazine-based, azine-based, methine-based, oxazine-based, phenylmethane-based, cyanine. Various dyes such as system dyes, azo dyes, anthraquinone dyes, pyrazoline dyes, stilbene dyes, quinoline dyes, and phthalocyanine dyes are used.

The image-forming substance is a substance that is finally transferred to an image-receiving paper to form an image, and is a dye, an inorganic or organic pigment which is itself colored, and an energy from the outside which is itself colorless. There are thermochromic compounds, photochromic compounds, and dye precursors that develop color when they react with other substances.

However, in a microcapsule for forming a full-color image, an organic or inorganic pigment is particularly preferable as the image forming substance from the viewpoint of color developability.

As the fixing accelerating substance, any substance having a preferable fixing property with respect to an image receiving body such as paper may be used. However, since the other components constituting the core substance are lipophilic, if the fixing promoting substance is also lipophilic, microencapsulation becomes easy. Further, the solid state rather than the liquid state is not compatible with the photosensitive substance, so that there is no fear of inhibiting the photocuring reaction.

Examples of such a fixing accelerating substance include:
Waxes such as carnauba wax, paraffin wax and microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid and lauric acid, higher fatty acid metal salts such as zinc stearate, lead stearate, barium stearate and magnesium stearate, methyl Higher fatty acid derivatives such as hydroxystearate and glycerol monohydroxystearate, low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polyisobutylene, polyolefin such as polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer Olefin copolymers such as polymers, ethylene-vinyl chloride copolymers, ethylene-vinyl acetate copolymers, styrene resins, epoxy resins, polyester resins, isobutyle Rubber, nitrile rubber, such as chlorinated rubber, polyvinyl pyrrolidone, polyamides, maleic acid modified phenolic resins, singly or in plural kinds among silicon resin.

The wall member of the microcapsule can be manufactured by a method already known in the art. For example, US Pat. No. 2,800,457.
No. 2,400,458 and the like, a method of phase separation from an aqueous solution as described in JP-B-38-1974 and JP-A-4
No. 2-446, No. 42-771, etc., interfacial polymerization method, JP-B-36-9168, JP-A-51.
I by polymerization of monomers shown in Japanese Patent Publication No. 9079
n-situ method, British Patent Nos. 952807 and 96
Although there is a melt dispersion cooling method and the like shown in the specification of 5074, it is not limited to this.

As the material for forming the wall member, gelatin, gum arabic, starch, sodium alginate, polyvinyl alcohol, polyethylene, polyamide, polyester, polyurethane, polyurea, polyurethane, polystyrene, nitrocellulose, ethylcellulose, methylcellulose, melamine-formaldehyde. A resin, urea-formaldehyde resin, or the like is used, but a material that allows sufficient light transmission is more preferable.

Further, the core substance 3 is a liquid photosensitive substance 6
And a pigment powder 4 which is an image forming substance finely dispersed in a photosensitive substance 6, and a paraffin wax 5 which is a fixing promoting substance.

A method for manufacturing the microcapsules will be described.

First, the photosensitive material is prepared. 100 parts by weight of a mixture of polyethylene glycol diacrylate and dipentaerythritol hexaacrylate, which are polymerizable monomers, in a ratio of 3: 4, and 2,2-dimethyl-2-morpholino-4'-methylthioacetophenone were added to 3.5 parts by weight.
By weight, 3.5 parts by weight of 2,4-diethylthioxanthone and 0.5 parts by weight of 3-thenoyl-7-dimethylaminocoumarin are mixed and heated at 100 ° C. for 10 minutes. 1 part by weight of a disazo yellow pigment and a particle size of 1 to 5 μm
20 parts by weight of the paraffin wax in particulate form is added and ultrasonically dispersed for 5 minutes to obtain a lipophilic substance as a core substance of the microcapsules.

A 10% aqueous solution of PVA was added to this lipophilic substance and emulsified by a homogenizer to obtain a 0 / W emulsion. The emulsion is diluted with an aqueous solution of ammonium chloride, and further an aqueous solution of melamine prepolymer is added. This melamine prepolymer was prepared by dissolving melamine and formalin at a ratio of 1: 3 in an alkaline aqueous solution of PH8.
It is obtained by heating at 80 ° C. for 5 minutes. When this emulsion was stirred at a water temperature of 80 ° C. for 4 hours, melamine resin was precipitated around the droplets of the lipophilic core substance,
A capsule slurry in which photosensitive microcapsules for yellow color development were dispersed in water was obtained.

A small amount was extracted from this capsule slurry and the particle size was measured by a laser diffraction type particle size distribution analyzer, and it was found to be 8 μm on average.

Using magenta or cyan color as the sensitizing dye and pigment, the photosensitive microcapsules for magenta coloring and cyan coloring are dispersed by the same method as in the case of the yellow microcapsules. A capsule slurry was obtained.

The three-color capsule slurries were thoroughly mixed, and the mixed capsule slurries were dried by a vacuum freeze dryer to obtain particulate microcapsules used for full-color image formation.

In this method for producing microcapsules, by using urea prepolymer instead of melamine prepolymer, microcapsules having an outer wall of urea / formalin resin can be produced.

An example of an image forming apparatus using the photosensitive microcapsules of this embodiment will be described below with reference to FIG.

In FIG. 2, inside the image forming apparatus 100, a capsule holding unit 30 that holds and conveys microcapsules, a microcapsule applying unit 20 that applies microcapsules, and the microcapsules are exposed according to image information. An exposure unit 10 for transferring the core substance of the microcapsules and a transfer unit 40 for transferring the core substance of the microcapsules to the image receiving paper are provided.

The capsule holding unit 30 comprises a capsule holding roller 31, a holding roller 31, and a cleaning unit 33, and the tip of the cleaning blade 34 of the cleaning unit 33 is in contact with the holding roller 31.

The transfer section 40 is composed of a transfer roller 41 and a heat roller 45 which is opposed to the transfer roller 41 with the image receiving paper 51 interposed therebetween and includes a heating source such as a heating resistor.

Further, a region where the capsule holding roller 31 and the transfer roller 41 face each other constitutes a destruction portion 42 for pressing the microcapsule to release the core substance.

The capsule holding roller 31 and the transfer roller 41 are both columnar or cylindrical, and have a diameter of, for example, about 30 mm to 200 mm and a length (length in the direction perpendicular to the paper surface in FIG. 1) of about 300 mm. Further, since the holding roller 31 and the transfer roller 41 are required to withstand the pressing force for breaking the microcapsules, at least the core portion is made of metal such as stainless steel or aluminum.

Further, on the surface of the holding roller 31,
Appropriate irregularities are provided so that solid substances such as microcapsules can be easily held. On the other hand, the surface of the transfer roller 41 is made of a material such as a polyethylene resin that has been plasma-treated so that the liquid core substance encapsulated in the microcapsules easily adheres.

The exposure section 10 is composed of an exposure lamp 11, a document table glass 15, a document cover 13, a filter 14 for adjusting a color tone of an image, and a light shielding plate 19.

The microcapsule coating section 20 is provided to dry-coat the holding roller 31 with microcapsules, and a case 21 for storing the microcapsules 1.
It comprises a stirrer 23, a carrier 25 carrying microcapsules, a supplier 24 for supplying the microcapsules to the carrier 25, and the stored particulate microcapsules 1.

An electric field for moving the microcapsules from the carrier 25 to the holding roller 31 is formed between the holding roller 31 and the microcapsule carrier 25 by a DC or AC power supply (not shown). Has been done.

Next, the operation of this device will be described.
When a start switch (not shown) is turned on, the holding member 31
Starts rotating in the direction of the arrow in the figure.

In the microcapsule coating section 20, the microcapsules are charged and carried on the carrier 25 by the rotation of the agitator 23 and the feeder 24. The carried microcapsules receive an electrostatic attractive force in the direction of the holding roller 31 due to the electric field formed between the holding roller 31 and the carrier 25. As a result, the microcapsules 1 move toward the holding roller 31 and adhere to the holding roller 31 by electrostatic force. That is, the particulate microcapsules 1 are applied to the holding roller 31.

The outer wall of the microcapsule 1 has sufficient strength so that the microcapsule 1 is not destroyed during the above-described operation.

The holding roller 31 rotates in the direction of the arrow in the figure,
Along with this, the coated microcapsules 1 are conveyed to the lower part of the exposure unit 10. At this point, the halogen lamp 11 of the exposure unit 10 is turned on, and the original platen glass 15 supporting the original 12 is moved. As a result, the exposure operation is performed according to the original 12. The light reflected from the original 12 passes through the filter 14 for adjusting the color tone of the image,
An image is formed on the surface of the image microcapsule 1 applied to the holding member 44.

The image microcapsules 1a thus exposed according to the image information are cured because the core substance undergoes a polymerization reaction. In the unexposed microcapsules 1b, there is no change in intensity.

Further, microcapsules 1a and 1b
Is conveyed toward the destruction portion 42, is sandwiched between the holding roller 31 and the transfer roller 41, and is pressurized.

Of the pressurized microcapsules,
In the uncured microcapsules 1b, the wall material is broken and the core substance 3 flows out.

As described above, the core substance 3 is a liquid photosensitive substance 6, a pigment powder 4 which is an image forming substance finely dispersed in the photosensitive substance, and a paraffin wax 5 which is a fixing promoting substance. It consists of

Since the microcapsule 1 and the transfer roller 41 are in contact with each other and the surface of the transfer roller 41 is made of a material which is easily wetted by the core material, the core material 3 is transferred to the transfer roller 41.

Since the microcapsules 1a cured by the imagewise exposure and the remaining wall member 2 from which the core substance 3 has been released are solids, they remain on the holding roller 31 due to the unevenness of the surface of the holding roller 31. Thereafter, the blade 34 of the cleaning unit 33 strips the holding roller 31 to collect and discard it.

The image receiving paper 52, which is plain paper, is the paper feed cassette 5.
1, the transfer roller 41 and the heat roller 45.
Sent during.

When the image receiving paper 52 and the transfer roller 41 are heated by the heat roller 45, the core substance 3 attached to the transfer roller 41 is also heated, so that the fixing accelerating substance such as wax is softened or melted. Therefore, the core substance 3 is transferred to the image receiving paper 52.

When the image receiving paper 52 is separated from the heat roller 45, the core substance 3 is cooled, so that the core substance 3 is fixed on the image receiving paper. Therefore, the core substance 3 does not penetrate between the fibers of the image receiving paper. Since the core substance 3 contains the image forming substance 4, an image is formed on the image receiving paper 52, and the image receiving paper is discharged to the outside of the apparatus.

In the image forming apparatus described above, the core substance is fixed on the image receiving paper by heat fixing using a heat roller, but it is also possible to use so-called pressure fixing using a pressure roller instead of a heater. In this case, since the fixing promoting component of the core substance is rubbed against the surface of the image receiving paper by the pressure, the diffusion of the liquid photosensitive material of the core substance in the image receiving paper surface is hindered by the fixing promoting component.

[0058]

As is apparent from the above description, when an image is formed on an image receiving paper using the image microcapsules of the present invention, the core substance is fixed on the image receiving paper by the action of the fixing accelerating component. The core substance does not spread beyond the pixel size and penetrate into the surface of the image receiving paper. Therefore, it is possible to form a clear image on plain paper or the like while maintaining the original texture of the image receiving paper.

[Brief description of drawings]

FIG. 1 is a diagram showing the inside of an image forming microcapsule of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus using the image forming microcapsules of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microcapsule 2 Wall member 3 Core substance 4 Image forming substance 5 Fixing promoting substance 6 Photosensitive substance 10 Exposure part 20 Microcapsule coating part 30 Microcapsule holding part 40 Microcapsule transfer part 42 Destruction part 52 Image receiving paper 100 Image forming apparatus

Claims (1)

[Claims] 1. A microcapsule for image formation in which a core substance comprising at least an image forming substance such as a pigment, a dye, a dye precursor and a photosensitive substance is encapsulated by a resin or the like, wherein the core substance contains waxes or the like. An image forming microcapsule comprising a fixing accelerating substance.