JP2899910B2 - Image forming method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a novel image forming method, and more particularly, to supplying an aqueous liquid developer containing at least a photochromic polymer as toner particles on a transparent substrate having a hydrophobic surface. Then, light irradiation corresponding to image information is performed from the back side of the transparent substrate to change the wettability of the toner surface to adhere and form a toner image on the transparent substrate surface, and this is transferred onto a transfer paper such as plain paper. The present invention relates to an image forming method for transferring images.

[Conventional technology]

There are several known means for easily obtaining a copied image.
Among them, (1) an offset master in which an image is formed on a master paper with a lipophilic material and desensitization treatment is performed to prepare an offset master, and an oil-based ink is supplied to the image portion and then transferred to plain paper to obtain a copy. A printing method, (2) an electrophotographic method of forming an electrostatic image on a photoreceptor, supplying charged toner to the image, developing the image, and transferring the toner image to plain paper to obtain a copy is often used. ing.

However, in the offset printing method (1), since printing is performed after the offset master is prepared, there is a disadvantage that unless a large number of sheets are printed, the cost per sheet is high and the method is not economical. In the electrophotography of the above (2),
When a dry developer is used, the inside of a copying machine is contaminated with dust, and when a wet developer is used, a gas of an organic solvent as a carrier liquid is generated, which is problematic in terms of environmental hygiene. Although it is considered to use water as a carrier liquid for a wet developer, however, in a developer using such an aqueous carrier liquid, charges on a photoreceptor easily leak and image formation is difficult.

[Problems to be solved by the invention]

A first object of the present invention is to provide a toner (including a harmless wet developer dispersed in water as a carrier liquid) containing at least a photochromic material whose surface properties (wettability) change reversibly upon irradiation with light. It is an object of the present invention to provide an image forming method which can be used to obtain a copy at low cost and safely. A second object of the present invention is to provide a photoreceptor and its peripheral parts, which are required for a conventional electrophotographic apparatus, because image formation is performed by toner particles not having electrical characteristics but by a change in wettability of the particle surface. An object of the present invention is to provide an image forming method capable of reducing costs by eliminating electric components and further simplifying an electrophotographic process. A third object of the present invention is to provide an image forming method capable of reducing the amount of carrier liquid that becomes overloaded when fixing a formed image on transfer paper such as plain paper.

[Means for solving the problem]

The image forming method according to the present invention includes the step of simultaneously or immediately after contacting a liquid developer in which toner particles containing at least a photochromic polymer are dispersed with an aqueous carrier liquid on the surface of a transparent substrate having a hydrophobic surface; Irradiate light of a specific wavelength from the back side to write image information,
After changing the surface property of the received toner particles from hydrophilic to hydrophobic and causing the toner particles to adhere to the transparent substrate surface,
It is characterized in that this toner image is transferred to plain paper or the like.

The present inventors apply reversible wetting change of photochromic material due to light irradiation to toner particles using water as a carrier liquid (wet toner), and use this characteristic change to apply hydrophobic property to the surface of a transparent substrate having hydrophobic surface. The toner image
It was confirmed that by transferring this to plain paper or the like, the above-described disadvantages of the related art can be solved. The method of the present invention has been made based on this finding.

The photochromic material utilizes reversible structural changes such as isomerization and ionic cleavage by light irradiation, and reversibly changes its physical properties (hydrophilicity / hydrophobicity). It is already known that it is possible to control the function of the photochromic material by light, and that it is possible to control the absorption and desorption of a substance by light if the photochromic material is used as an adsorbent. ("Polymer Papers" Vol.37, N
o.4, PP.287-291 (Apr, 1980)).

However, as described in this document, although a change in hydrophobicity (wetting change) due to light irradiation of a photochromic material is known, the emphasis has been placed on the coloring / decoloring function, Generally, the photochromic material itself is coated on paper or the like and used for image formation.

The toner component of the liquid developer used in the present invention has a photochromic polymer as a main component, and is obtained by mixing and dispersing a colorant and a binder resin as needed.
Water is particularly preferred as the carrier liquid. However, the photochromic polymer alone can be used as the toner component, and the color can be controlled by using the color change function unique to the polymer. Further, depending on the combination of polymer species that reacts with the wavelength of incident light, multicolor development can be performed. Depending on the composition of the polymer or the fixing method, the fixing properties can also be controlled by the polymer alone.

According to the method of the present invention, as inferred from the above description, a wet toner containing a photochromic polymer as a main component is supplied to the surface of a hydrophobic transparent substrate (transparent substrate having a hydrophobic surface), and the wet toner is passed through the transparent substrate. Change the surface property of the toner that has been irradiated and irradiated on the toner layer from hydrophilic to hydrophobic,
Attaching (development) to the transparent substrate surface to obtain an image,
Means of transferring this visible image to plain paper or the like is employed. Therefore, the hydrophobic transparent substrate used in the method of the present invention may be either a cylindrical shape or an endless belt shape.

To explain the above phenomenon in more detail, light of a specific wavelength, for example, visible light, laser light, or the like, is image-formed (positive or negative) from the back side of the transparent substrate in a state where the liquid developer is thinly applied to the surface of the hydrophobic transparent substrate. ) Is irradiated or scanned. As a result, the surface of the toner particles irradiated with light becomes hydrophobic from hydrophilic and adheres to the transparent surface of the transparent substrate, where an image is formed. The toner image is further transferred onto a transfer paper such as a plain paper to form a copy. After the transfer, if necessary, a fixing process using a heat roller or the like may be performed.

When the transfer residual toner is present on the surface of the hydrophobic transparent substrate after transferring the image (toner image), light having a wavelength different from that of the image formation (the toner particles are changed from hydrophobic to hydrophilic). The surface of the transparent substrate may be irradiated with an appropriate light (e.g., ultraviolet light) from the back side of the transparent substrate to make the properties of the toner different from that of the surface of the transparent substrate.

The following compounds can be exemplified as typical photochromic materials that can be used in the method of the present invention. No.1, No.2 and No.3 are azobenzene type, No.4
No. 5, No. 6, No. 6 and No. 7 are spiropyran type, No. 8 is dithizone type, No. 9 is thionine type, No. 1
0 is a piologen-based polymer.

Most of these polymers have high hydrophilicity by irradiation with ultraviolet light and have high lipophilicity by irradiation with visible light, but polymers having the opposite effect may be used.

The contact angle between the polymer (photochromic material) and the water used in the method of the present invention before and after the change by light irradiation is 10 ° or more, preferably 50 ° or more.

To actually carry out the method of the present invention, the liquid developer as described above is brought into contact with a transparent substrate having a hydrophobic surface by using a moving tool such as a gravure roll at the same time or immediately after the contact with the liquid developer. Image information is written from the side by laser light or the like. The portion of the wet toner which has been irradiated with the light changes from hydrophilic to hydrophobic, and adheres to the transparent substrate which is a hydrophobic surface to form an image. The (hydrophilic toner) repels the toner from the hydrophobic surface of the transparent substrate, and thus remains on the gravure roll and is collected. In addition, since the toner particles irradiated with light are hydrophobic, they repel water as a carrier liquid, and the amount of water contained in the particles becomes very small.

The toner having an image formed on the transparent substrate may be transferred onto transfer paper by means such as pressing, and then may be fixed onto the transfer paper by means such as natural drying or heat fixing.

〔Example〕

P-Phenylazoacrylanilide (PAAn), which is a vinyl monomer of azo dye, is composed of acrylic acid chloride and p-phenylazoacrylanilide.
It was synthesized by a condensation reaction with aminoazobenzene and recrystallized from a mixed solvent of water and ethanol (1: 1).

AIBN is collected in a polymerization tube, a predetermined amount of PAAn and HEMA are charged, degassed by a conventional method, and sealed under a vacuum, and the polymerization tube is heated to 60 ° C.
To carry out a copolymerization reaction while shaking for a predetermined time. Next, the reaction was stopped by cooling, and the obtained reaction mixture was diluted with DMF, precipitated in a mixed solvent of ether and ethyl acetate, filtered and dried in vacuo.

1,3,3-trimethylindolino-6'-nitro-8 '
-Acryloyloxymethyl spirobenzopyran (AS
P) was synthesized according to the method of Kikuchi et al. Described in Journal of the Chemical Society of Japan, 1323, 1972.

A predetermined amount of ASP is charged into a polymerization tube together with AIBN, degassed by a conventional method, sealed under vacuum, and shaken at 60 ° C. in a polymerization tank.
A polymer was obtained. Next, the reaction was stopped by cooling, and the resulting reaction mixture was precipitated in methanol, filtered and dried in vacuo.

The spiropyran polymer, carbon black, carboxymethylcellulose and carnauba wax are melt-kneaded, cooled, pulverized, irradiated with ultraviolet light, dispersed in water (carrier liquid), and dispersed in an attritor for 20 hours. 40
The mixture was dispersed at ℃ to obtain a liquid developer.

A photoreceptor drum of a commercially available electrophotographic copying machine (CT-5085, manufactured by Ricoh Co., Ltd.) was extracted, and a writing device using an LED light emitting element was set inside the drum so as to illuminate the surface of the cylinder. Further, the charger for charging the photoreceptor was removed, and the transfer charger was taken out. Instead, a sponge roller was pressed against the cylinder. The liquid developer was charged into the developing tank of this apparatus, and the machine was operated as when a normal copy was obtained. However, the image information is LED
In order to form a clearer image written by the element, the speed of paper passing and the like was reduced to half of the normal speed.

As a result, a clear copied image could be obtained, and no unpleasant odor was felt even after multi-copying.

〔The invention's effect〕

According to the method of the present invention, the following effects are obtained.

(1) Since no electrostatic force is used, a copying process using water as a carrier liquid can be realized, and a developer that does not cause unpleasant odor or environmental pollution can be provided.

(2) Since a master paper such as offset printing is not required, a low-cost copy can be obtained.

Continuation of front page (72) Inventor Hidemi Uematsu 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-1-140882 (JP, A) JP-A-63-101844 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03C 1/73

Claims (1)

(57) [Claims] An aqueous carrier liquid is contacted with a liquid developer in which at least a toner particle containing at least a photochromic polymer is brought into contact with a surface of a transparent substrate having a hydrophobic surface. After the image information is written by irradiating light of a specific wavelength, the surface property of the received toner particles is changed from hydrophilic to hydrophobic, and the toner particles are attached to the surface of the transparent substrate. An image forming method, wherein the image is transferred onto paper or the like.