JP2000321695A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with which bright images are stably obtained for a long period of time. SOLUTION: This image forming device is provided with a photoisomerization layer 12b which is reversibly changed in wettability at an image carrying drum 12 and forms a wet latent image on the photoisomerization layer 12b of the image carrying drum 12 by selective exposure. This wet latent image is developed by adhering ink thereto and prints a recording medium S with the developed ink image by transfer. The image forming device 10 described above is characterized in that the surface of the photoisomerization layer 12b is provided with a coating applicator 26 for applying a photoisomerization material thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a photoisomerizable material which is wettable by exposure to light and selectively exposes a photoisomerizable layer of an image carrier to form a wetting latent image. The present invention relates to an image forming apparatus that prints an image by developing the wet latent image with ink and transferring the latent image to a recording medium.

[0002]

2. Description of the Related Art Hitherto, Japanese Patent Application Laid-Open No. 1-255857 discloses an image forming apparatus having an image forming body provided with a photoisomerization layer containing, for example, azobenzene. In this image forming apparatus, the photoisomerization layer on the surface of the image forming body is selectively exposed according to image information, thereby increasing the wettability of the exposed portion to form a chemically wet latent image, Thereafter, the wet latent image is developed with ink to form an ink image, and the ink image is transferred from the image forming body to a recording medium to perform image printing. After printing the image, the surface of the image forming body is cleaned, and the wet latent image is erased by uniformly irradiating the photoisomerization layer with visible light.

[0003]

However, in this image forming apparatus, the photoisomerization layer deteriorates as the formation and erasure of the wet latent image are repeatedly performed, whereby the photoisomerization reaction upon exposure is reduced. Eventually, there was a problem that a clear image could not be obtained.

[0004]

In order to solve the above-mentioned problems, the present invention provides a photoisomerizable layer having a reversible change in wettability on an image carrier, and the photoisomerizable layer on the image carrier is provided on the image carrier. An image forming apparatus that forms a wet latent image by selectively exposing the ink, attaches ink to the wet latent image, develops the image, transfers the developed ink image to a recording medium, and prints the image. The present invention is characterized in that a coating device for coating the photoisomerization material on the surface of the isomerization layer is provided.

[0005]

According to the image forming apparatus of the present invention, since the coating device for coating the photoisomerizable material on the surface of the photoisomerization layer is provided, the light of which the surface of the photoisomerization layer is not always deteriorated is provided. It is composed of isomerized materials. This makes it possible to stably obtain a clear image without fog or density unevenness over a long period of time.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an image forming apparatus 10 of the present embodiment. Image forming apparatus 10
Has an image bearing drum (image bearing member) 12. The image bearing drum 12 is rotatable in the direction of arrow 14. An exposure device 16, an ink developing device 18, a transfer roller 20, a cleaning member 22, an erase lamp 24, and a coating device 26 are arranged around the image bearing drum 12 in this order along the rotation direction.

As shown in FIG. 2, the image bearing drum 12 is
A roller-shaped or cylindrical base 12a made of metal or the like;
It comprises a photoisomerization layer 12b provided on the outer periphery of the base 12a. The photoisomerization layer 12b is formed by kneading a material 42 having a reversible change in wettability into a binder (for example, wax) 40 as shown in FIG.
As shown in (b), the binder is formed by kneading a material 42 having a reversibly changeable wettability bonded to a main chain or a side chain of a polymer material.

In each of the cases shown in FIGS. 2A and 2B, two or more kinds of materials having a reversible change in wettability may be used, or two or more kinds of binders may be mixed and used. You may. When the melting point of the reversibly wettable material itself is low, the material that reversibly changes wettability is melted and applied to the substrate 12a without using a binder, whereby the photoisomerizable layer 12b is melted. May be formed.

The photoisomerization layer 12b constructed as described above
The surface of is usually hydrophobic, so that ink does not adhere thereto, but when irradiated with a predetermined light (for example, ultraviolet light), wettability increases due to a chemical change, and ink is exposed to the exposed portion. It has the property that it can be attached. on the other hand,
When the portion of the photoisomerized layer having increased wettability as described above is irradiated with visible light, the original property, that is, the surface returns to a hydrophobic state. Such a reversible change in wettability of the photoisomerization layer is called “photoisomerization”.

Examples of the material 42 that changes reversibly in wettability include an ion dissociable triphenylmethane dye, cis-
Trans-isomerizing azobenzene-based, indigo-based or stilbene-based compounds, keto-enol tautomeric azohydrazone-based compounds, fulgide-based, diarylethene-based, spiropyran-based, or spirooxazine-based compounds that undergo ring-opening / closing reactions are preferably used. However, the present invention is not limited to these. Alternatively, titanium oxide causing a reversible change in hydrophobicity and hydrophilicity by a photocatalytic reaction,
Iron oxide, cadmium sulfide, molybdenum sulfide, zinc oxide,
Vanadium oxide, zirconium oxide, tungsten oxide, and the like can also be used as the material 42 whose wettability changes reversibly.

The polymer material that binds the reversibly wettable material 42 to the main chain or the side chain is not particularly limited as long as the photoisomerization of the functional group of the reversibly wettable material is sufficiently performed. However, polystyrene, polyethylene, polymethacrylate, cellulose, polyvinyl butyral, polyester, phenoxy resin, polyurethane, polyacrylate, polycarbonate and the like are preferable.

The binder 40 is not particularly limited as long as it has a low melting point such as wax. For example, paraffin wax, microcrystalline wax, carnauba wax, candelilla wax, rice wax, wood wax, beeswax, spermaceti, montan wax, ozokerite, ceresin, polyethylene wax, fisher
Waxes such as tropush wax, amide wax, and hydrogenated castor oil are preferably used. Further, a water-repellent wax containing fluorine, silicone, or the like can also be used.

Referring again to FIG. 1, the exposure apparatus 16 includes:
The surface of the photoisomerization layer 12b of the image bearing drum 12 is selectively exposed according to the input image information. Thereby, the wettability of the exposed portion is increased, and a wet latent image is formed. The ink developing device 18 has a developing roller 32 that accommodates the ink 28 therein and is driven to rotate in the direction of the arrow 30. The ink 28 held in a thin layer around the developing roller 32 is an image bearing drum. 12 is supplied to a portion facing the same.

The transfer roller 20 is driven to rotate in the direction of arrow 34 while sandwiching a sheet (recording medium) S such as recording paper sent from a paper feed tray (not shown) between the transfer roller 20 and the image bearing drum 12. To convey the sheet S in the direction of the arrow 36. In addition, an ink fixing device (not shown) may be provided on the downstream side of the transfer roller 20 in the sheet conveying direction as necessary.

The cleaning member 22 is composed of a blade having a tip abutting on the surface of the image bearing drum 12 and collects ink and dust adhering to the surface of the image bearing drum 12.
The cleaning member 22 may also serve as a shaving member for removing a deteriorated portion of the photoisomerization layer 12b by scraping the surface of the photoisomerization layer 12b little by little.

The erase lamp 24 is connected to the image bearing drum 12
The upper photoisomerization layer 12b is uniformly irradiated with visible light to erase the wet latent image. As a light source of the erase lamp 26, a halogen lamp, a xenon lamp, an incandescent light source, a fluorescent lamp, a light emitting diode, a laser, or the like can be used. Further, since the erasing of the latent image is also promoted by heating, a heating device may be provided together with the erase lamp 24.

The coating device 26 includes a container 32 and the container 3
2, an application roller 3 that rotates in the direction of arrow 28 in contact with the photoisomerization layer 12b of the image bearing drum 12.
0. The container 32 contains a mixture of a reversibly wettable material and a low-melting-point binder in a solid or semi-solid state at room temperature. The container 32 is always kept at a temperature slightly higher than room temperature, so that the low-melting-point binder containing the material whose reversibility changes reversibly therein is in a molten or semi-solid state. In this state, when the application roller 30 is driven to rotate, the material and the binder, which are held in a thin layer state on the outer periphery thereof and whose reversible wettability is changed, become the image bearing drum 12.
The photoisomerization layer 12b is uniformly coated with a predetermined thickness. In addition, the application by the application member is not limited to the one using the roller, and other methods,
For example, it may be applied by a blade-like material, or may be applied by spraying.

The application by the application roller 30 may be performed each time an image is formed, or may be performed each time a predetermined number of images are formed. The application roller 3
Although the application surface with 0 is formed on a uniform smooth surface, the application surface may be applied so as to have a constant roughness, or may be applied in a predetermined pattern (for example, dot shape or grid shape). You may do so. Furthermore, in the present embodiment, a mixture of a material that reversibly changes in wettability and a binder is applied, but in the case of a material that has a low melting point and reversibly changes in wettability, it is used alone without using a binder. You may make it apply.

Although not shown, the application roller 30
A cooling device may be provided on the downstream side of the coating device 26 in the rotation direction of the image bearing drum in order to accelerate the solidification of the binder applied by the coating.

Next, the image forming apparatus 10 having the above configuration will be described.
Will be described. For example, ultraviolet light is selectively exposed from the exposure device 16 to the surface of the image bearing drum 12 that is driven to rotate in the direction of the arrow 14 in accordance with image information. At this time, the exposed portion of the photoisomerization layer 12b is chemically changed to increase the wettability of the surface, thereby forming a wet latent image.

The wet latent image moves to the opposite portion of the ink developing device 18 according to the rotation of the image bearing drum 12, where it contacts the ink held on the outer periphery of the developing roller 32. At this time, the ink does not adhere to the surface of the non-exposed portion of the photoisomerization layer 12b due to its hydrophobicity, and the ink adheres only to the wetted image portion having high wettability. As a result, the wet latent image is developed with ink and becomes an ink image. The ink image is transferred to the transfer roller 34 according to the rotation of the image bearing drum 12.
Is transferred to the sheet S where the image is printed. The sheet S on which the image is printed is discharged onto a discharge tray (not shown).

The ink and dust remaining on the image carrier drum 12 after the transfer of the ink image are removed by the cleaning member 22. After that, the wet latent image moves to the opposite portion of the erase lamp 24 according to the rotation of the image bearing drum 12, where it is erased by being uniformly irradiated with visible light. After the wetting latent image is erased, the coating device 26 uniformly applies a mixture of a material and a binder having a reversible wettability to the surface of the photoisomerization layer 12b of the image bearing drum 12 to a predetermined thickness. Thus, preparation for the next printing step is completed.

As described above, the image forming apparatus 10 of the present embodiment
Since a coating device is provided for applying a material that reversibly changes wettability together with a binder on the surface of the photoisomerization layer 12b, the surface of the photoisomerization layer changes reversibly without deterioration. It is made of material. This allows
A clear image without fog or density unevenness can be stably obtained over a long period of time. In addition, an environmentally safe device can be provided by using a wax that is harmless to the environment as a binder for the photoisomerization layer 12b.

In the above-described embodiment, a material obtained by kneading a reversibly changeable wettability into a binder or a material obtained by binding a reversibly changeable wettability to a main chain or a side chain of a polymer material is used. Image bearing drum 1
As shown in FIG. 3, at least one kind of material having a reversible change in wettability is dispersed in the polymer material, or the main chain of the polymer material is dispersed. The photoisomerization layer 12b may be formed by forming small particles 44 by bonding to the side chains or by kneading the particles 44 into a binder 40. FIG. 4A shows particles 44 formed by dispersing a reversibly wettable material 42 in a polymer material 46, and FIG. 4B shows a particle 44 formed by reversibly changing the wettability. The particle 44 formed of the molecular material 46 bonded to the main chain or side chain is shown. In the case of such a configuration, two surfaces having different surface energies exist on the surface of the photoisomerization layer 12b, that is, the exposed surface of the particles 44 containing the material whose reversibility changes with the surface of the binder 40. Will be. In this case, the coating device 26 accommodates and applies the same components as those constituting the photoisomerization layer 12b.

The shape of the particles 44 may be spherical, porous, polygonal, cylindrical, columnar with a high aspect ratio, or the like, but is not limited thereto. The various materials described above can be suitably used as the material, the polymer material, and the binder that change reversibly in wettability. When a compound that causes a photocatalytic reaction, such as titanium oxide, is used as the material that changes reversibly in wettability, the above-mentioned particles 44 are formed alone using, for example, titanium alkoxide without mixing with other polymer materials. Or a fluororesin such as polytetrafluoroethylene (PTFE) that does not deteriorate or decompose even when mixed with a photocatalytic compound;
The particles 44 may be prepared by mixing with a silicon-based resin having a siloxane bond or an inorganic compound such as silica or water glass.

The material 4 whose wettability changes reversibly in this way
The image forming operation and its effect when the photoisomerization layer 12b is formed by dispersing the particles 44 containing 2 in the binder 40 are also the same as those of the image forming apparatus 10, and therefore the description is omitted.

Here, a printing experiment was performed using the image forming apparatus 10 described above. The image bearing drum 12 used was a photo isomerization layer 12b formed by dip coating on the outer periphery of an aluminum base 12a. The photoisomerization layer 12b is made of spiropyran, a material that changes reversibly in wettability.
(1 ', 3'-Dihydro-3', 3'-dimetyl-6-nitro-1'-octadecyls
A mixture in which piro [2H-1-benzopyran-2 ′, 2 ′-[2H] indoline]) and candelilla wax as a binder were kneaded at a weight ratio of 1: 1 was used.

The coating device 26 accommodates a material having the same composition as the photoisomerization layer 12b, and heats and maintains the wax at a temperature equal to or higher than the melting point of the wax to apply the molten material.

An ultraviolet lamp is used as a light source of the exposure device 16, and the ultraviolet light emitted from the lamp is passed through a filter (03F IU012) manufactured by Kino Melles Griot Co., Ltd. to form a wet latent image with ultraviolet light having a wavelength of 360 nm. Was.
After developing this wet latent image with ink, it was transferred to a recording paper and printed. After the transfer, the visible latent image was erased by uniformly irradiating the photoisomerization layer 12b with visible light using the erase lamp 24.

Each time the printing step, ie, the reversible photoisomerization reaction is performed 1000 times, a candelilla wax containing spiropyran is applied to the surface of the photoisomerization layer 12b to a thickness of 1 μm by the coating device 26, and this is repeated 10 times. After that, printing was performed (that is, after the reversible photoisomerization reaction in the photoisomerization layer 12b was performed 10,000 times and the photoisomerization layer 12b was applied in a total of 10 μm). As a result, a clear image free from fog and density unevenness was obtained as compared with an image printed after reversible photoisomerization reaction was repeated 10,000 times without coating the photoisomerization layer 12b. As a result, the effect of the image forming apparatus 10 of the present exemplary embodiment could be confirmed.

In the above-described image forming apparatus 10, the image carrier 12 is formed in a drum shape. However, the present invention is not limited to this.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a partially enlarged view of an end of an image bearing drum.

FIG. 3 is a partially enlarged view of an end of an image bearing drum showing a modification of the photoisomerization layer.

FIG. 4 is an enlarged view of a particle containing a material that reversibly changes in wettability.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 12 ... Image carrying drum (image carrying body), 12a ... Substrate, 12b ... Photoisomerization layer, 16 ... Exposure apparatus, 18 ... Ink developing apparatus, 20 ... Transfer roller, 22
... cleaning member, 24 ... erase lamp, 26 ... coating device.

Claims (1)

[Claims] An image bearing member is provided with a photoisomerizable layer whose wettability changes reversibly, and a photoisomerizable layer on the image carrier is selectively exposed to form a wetting latent image. An image forming apparatus for printing an image by attaching an ink to a latent image and developing the image, transferring the developed ink image to a recording medium, and a coating apparatus for applying a photoisomerizable material to a surface of the photoisomerizable layer. An image forming apparatus, comprising: