JPH07199548A - Image forming method - Google Patents

Abstract

PURPOSE:To provide an image forming method which stores image information in an image holding member and continuously forming copies, and regenerates the image holding member storing the images to an initial state and reuses this member. CONSTITUTION:The image holding member 1 formed by successively laminating a charge generating layer 4, a thermal softening layer 5 contg. a charge transfer material and a thermally softening resin and a conductive particle dispersion layer 7 embedded with conductive particles 6 near the surface of this thermal softening layer 5 on the surface of a conductive substrate 2 is subjected to negative electrostatic charge to accumulate charges on the conductive particles 6. After the charges of the conductive particles 6 are erased in correspondence with the image information, the thermal softening layer 5 is heated to the softening point of the thermal softening resin or above to store the image information by the transfer of the conductive particles 6. The image holding member 1 storing the image information in such a manner is subjected to an electrophotographic method to execute copying, thereafter, the image holding member 1 storing the image information is subjected to a positive charge and is then heated to the softening point of the thermal softening resin or above to transfer the conductive particles 6 again near the surface of the thermal softening layer 5 to return the image holding member 1 to the initial state to be reused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using an image holding member used for storing image information and forming a continuous copy image, and more specifically, an image used by reproducing a used image holding member. It relates to a forming method.

[0002]

2. Description of the Related Art In the conventional electrophotographic copying method, after uniformly charging the surface of an electrophotographic photosensitive member, imagewise exposure is performed to attenuate the surface potential in an imagewise manner, and then toner development is performed to form a paper. The Carlson method of transferring is widely applied as a general method. However, in this method, each time an image is copied, it must be exposed once. Therefore, in high-speed copying, there is a problem that the device becomes complicated and becomes large in size. In order to improve this point, the present inventor previously used an image holding member in which conductive particles are embedded in the vicinity of the surface of a heat softening layer in Japanese Patent Laid-Open No. 5-72749, in which image information is stored. , One that makes continuous copies of a large number of sheets with only one image exposure was proposed.

[0003]

By the way, when continuous copying is performed using such an image holding member, the used image holding member (image is stored) is discarded each time, and then a new image holding member is used. It had the drawback of having to use one. The present invention aims to remedy the above-mentioned drawbacks. That is, an object of the present invention is to store image information by using an image holding member in which conductive particles are embedded in the vicinity of the surface of a heat-softening layer, make a copy, and then use an image holding member that stores the image. An object of the present invention is to provide an image forming method in which the image is reproduced in an initial state and reused.

[0004]

The inventors of the present invention have found that when the surface of an image-holding member used is charged to the opposite polarity, the electrostatic attraction acting on the conductive particles works in the opposite direction, and when heated, the heat-softening layer is heated. It was discovered that it moved to the surface side, and the present invention was completed. That is, according to the image forming method of the present invention, a charge generation layer, a heat-softening layer containing a charge-transporting substance and a heat-softening resin, and conductive particles are embedded on the surface of the heat-softening layer on the surface of the conductive substrate. The image-holding member in which at least the conductive particle dispersion layer was laminated sequentially was negatively charged to accumulate charges in the conductive particles, and then the charges of the conductive particles were lost corresponding to the image information. After that, the heat-softening layer is heated to a temperature equal to or higher than the softening point of the heat-softening resin, and the conductive particles in which electric charge is accumulated are moved in the heat-softening layer to store the image information, and the image information is stored. The image holding member is subjected to electrophotography including the steps of charging, developing and transferring to perform copying, and then the image holding member in which the image information is stored is positively charged, and then the heat softening layer is applied to the heat softening resin. Conductive particles that have moved by heating above the softening point of It was again moved to the vicinity of the surface of the heat softened layer, and returning the image holding member to an initial state.

The present invention will be described in detail below. First, the image holding member will be described with reference to the drawings. In FIG. 1, reference numeral 1 is an image holding member having a charge generation layer. The image holding member 1 uses, as a conductive substrate, another substrate in which the conductive layer 3 is formed on the substrate 2, and a heat generating layer 4 on which a charge transport material and a thermosoftening resin that softens by heat are used. The softening layer 5 is sequentially stacked. In the vicinity of the surface of the thermal softening layer 5, the conductive particle dispersion layer 7 in which the conductive particles 6 are embedded is formed.

As the substrate of the image holding member, for example, a plastic film, paper or metal foil is used.
The surface of the substrate must have at least conductivity, and conductivity can be imparted by forming a conductive layer. The conductive layer may be of any type as long as the charge flows freely, for example, a metal film is deposited by a vapor deposition method,
It may be formed by a method such as a sputtering method, a plasma CVD method, or a plating method, or may be formed by applying a conductive coating material in which conductive particles such as metal or low resistance metal oxide are dispersed in resin. When the substrate itself has conductivity,
It is not necessary to form a conductive layer. An undercoat layer may be formed on the conductive surface of the substrate in order to improve adhesiveness, chargeability and image quality.

The charge generation layer laminated on the surface of the conductive substrate is composed of the same material as the charge generation layer in a commonly used organic photoconductive (OPC) photoreceptor. That is, as the charge generating substance, for example, phthalocyanine pigments such as metal or metal-free phthalocyanine, squarium compounds, azurenium compounds, perylene pigments, indigo pigments, quinacridone pigments, anthanthrone, brominated anthanthrone, pyranthrone, flavanthrone, and the like. Ring quinones are used. The charge generation layer can be formed by dispersing these charge generation substances, if necessary, together with the charge transport substance in the binder resin, and applying them. The film thickness of the charge generation layer is usually in the range of 0.1 to 2 μm.

The heat softening layer is composed of a charge transport material and a heat softening resin. As the charge transport substance, any substance can be used as long as it is used in the charge transport layer of a general electrophotographic photoreceptor. For example, polycyclic aromatic compounds such as anthracene-based, pyrene-based, phenanthrene-based, indole-based, carbazole-based, imidazole-based,
Examples thereof include pyrazoline-based nitrogen-containing heterocyclic compounds, hydrazone compounds, triphenylmethane compounds, triphenylamine compounds, stilbene compounds, benzidine compounds and the like.

As the thermosoftening resin, a glass transition point (T
A thermoplastic resin having a g) of 30 to 90 ° C. and a viscosity at a temperature of Tg or higher of 10 to 10 ⁵ Pascal seconds is preferably used. For example, polyethylene, polypropylene,
Vinyl chloride resin, styrene resin, ABS resin, polyvinyl alcohol, acrylic resin, acrylonitrile-styrene resin, vinylidene chloride resin, AAS (ASA) resin, AES resin, fibrin derivative resin, thermoplastic polyurethane, polyvinyl butyral, poly-4 -Methylpentene-1, polybutene-1, rosin ester resin and the like. Among them, a styrene-acrylic acid ester copolymer and a styrene-acrylic acid ester-acrylic acid terpolymer are particularly preferable. The film thickness of the heat softening layer is usually set in the range of 3 to 15 μm.

In the vicinity of the surface of the heat softening layer, that is, within a few times the diameter of the conductive particles from the surface, a conductive particle dispersed layer composed of a single layer or a plurality of conductive particles is formed. The particle size of the conductive particles is preferably in the range of 0.05 to 1 μm. As the conductive particles, in addition to carbon black, copper iodide, silver iodide, zinc sulfide, silicon carbide, etc., a conductive substance such as a metal oxide is preferably used. In particular, a metal oxide containing oxygen vacancies and a metal oxide containing a small amount of different atoms forming a donor are preferable because they have high conductivity and a large number of electron-hole pairs. Examples of metal oxides include ZnO, TiO ₂ , SnO ₂ , In ₂ O ₃ and MoO.
_{3 and the} like, or composite oxides of these. As an example including a heteroatom, for ZnO, Al, In, etc.,
Examples include TiO ₂ containing Nb, Ta and the like, and SnO ₂ containing Sb, Nb, In, halogen atoms and other heteroatoms. When these heteroatoms are contained, the addition amount is preferably in the range of 0.01 to 30 mol%,
The range of 10 mol% is particularly preferable. As a method of forming a conductive particle dispersion layer by embedding these conductive particles in the vicinity of the surface of the heat-softening layer, the conductive particles are dispersed in a solution of a heat-softening resin containing a charge transport substance, and the dispersion is The method of applying on the heat softening layer is mentioned.

Next, the process of storing image information in the image holding member of the present invention will be described with reference to FIGS. As shown in FIG. 2, the negative charging device 8 is moved relative to the image holding member 1 to negatively charge the surface. As a result, the conductive particles 6 embedded in the vicinity of the surface of the thermal softening layer 5 have electron-hole pairs at room temperature, so holes are immediately released to the negative charges on the surface, and the charge-transporting substance is discharged. To neutralize the surface charge. Then, negative charges remain on the conductive particles 6. Then, as shown in FIG. 3, the image holding member 1 is irradiated with light 10 corresponding to an image to expose the charge generation layer 4 to imagewise exposure. The light passes through the sufficiently thin conductive particle dispersion layer 7 and most of the light reaches the charge generation layer 4. In the case of laser diode light, the light is modulated by an electronic means in an image-wise manner to be exposed, and in that case, the light may be applied to the portion to which the developer is attached. As a result, positive charges are injected from the charge generation layer 4 into the thermal softening layer 5 and are transported in the thermal softening layer 5, and negative charges remain in the conductive particles 6.
Then, as shown in FIG. 4, the image holding member 1 is heated by applying heat 11. As a heating method, any method such as a method of passing it through a heating roller, a method of putting it in a heating container, a method of heating with a heating wire, or the like can be adopted, and it may be heated to a temperature of Tg or higher for several seconds. As a result, the conductive particles 6 in which the negative charges have remained move to the side of the base body 2 serving as an electrode in the heat-softened layer 5 which has been softened and whose viscosity has decreased due to electrostatic attraction. In this way, a portion containing the conductive particles that have moved (moving particles 6a) and the conductive particles that have not moved (non-moving particles 6b) is formed. Then, the image holding member 1 is returned to room temperature to obtain an image holding member 1'in which image information is stored.

Next, a copy is produced using the image holding member in which the image information is stored as described above. The copy is produced by an electrophotographic method. That is, as shown in FIG. 5, the negative charging device 8 is moved with respect to the image holding member 1'in which the image information is stored, and the entire surface thereof is negatively charged. As a result, in the portion where the non-moving particles 6b are present, as in the case shown in FIG. 2, negative charges remain in the conductive particles,
The surface potential is as low as 0 to 20% when the conductive particles are not present. Therefore, a latent image having an electrostatic contrast corresponding to the image is formed only by uniform negative charging on the entire surface. Next, the formed latent image is developed using a positively chargeable developer. As a result, the latent image is visualized, and a copy can be obtained by transferring the latent image on a transfer sheet by a conventional method. After that, by charging again, a latent image can be formed again. Therefore, copying can be continuously performed without performing image exposure. After copying, cleaning may be performed if necessary.

After the completion of copying, in the present invention, the image holding member in which the image information is stored is reproduced without being discarded and returned to the initial state for reuse. That is, first, as shown in FIG. 6, the surface of the image holding member 1 ′ on which the image is stored is positively charged by the positive charger 9. As a result, holes are emitted from the conductive particles and injected into the thermal softening layer, but since the conductive layer is negatively charged in the thermal softening layer, holes are transported to the conductive layer side as indicated by the arrow. As a result, negative charges remain on the conductive particles. Next, as shown in FIG. 7, the image holding member is heated by applying heat 12. In that case, contrary to FIG. 4, the conductive particles in the thermal softening layer 5 move toward the surface on the positive side by the electrostatic force. As a result, the conductive particles 6 return to their original positions, and a regenerated image holding member 1 ″ is obtained by cooling. The regenerated image holding member is similar to the new image holding member 1. It can be subjected to the image forming step shown in Fig. 2. When the regenerated image holding member is insufficient in charging property, it is considered that the returning condition of the conductive particles is insufficient, and therefore, Fig. 6 to Fig. It is effective to repeat the steps of positive charging to heating shown in Fig. 7. In the image forming method of the present invention, copying and reproduction can be repeatedly performed until the surface of the image holding member is worn.
When the number of copies increases during continuous copying, the surface of the image holding member wears, but the image holding member whose surface has worn out has reached the end of its life and can be discarded.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, "part" in an Example means a "weight part." Example 1 A 50 μm-thick polyester film having a conductive layer on which aluminum was vapor-deposited was used as a substrate. 5 parts of copolymer nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) was dissolved in 40 parts of methanol and 60 parts of butanol. To the obtained solution, 15 parts of anatase type titanium oxide (trade name: Taipaque W-10, manufactured by Ishihara Sangyo Co., Ltd.) was added and dispersed by a ball mill. The obtained dispersion liquid was applied onto the above-mentioned substrate with a wire bar, and the dispersion liquid was applied at 100 ° C for 10
After drying for a minute, an undercoat layer having a film thickness of 2 μm was formed. This undercoat layer has a function of preventing interference of laser light. Next, in 8 parts of a solution prepared by previously dissolving 1 part of polyvinyl butyral resin (trade name: S-REC BM-1, manufactured by Sekisui Chemical Co., Ltd.) in 19 parts of cyclohexanone, 1.6 parts of X-type phthalocyanine and 12. parts of cyclohexanone. 8 parts were mixed and subjected to a dispersion treatment for about 1 hour by a paint shaker using glass beads having a diameter of about 2 mm as a dispersion medium. The obtained dispersion is applied onto the undercoat layer with a wire bar, and 10
After drying at 0 ° C. for 10 minutes, a charge generation layer having a film thickness of 0.3 μm was formed. On the other hand, a terpolymer having a weight average molecular weight of about 8000 was prepared by using 62 parts of styrene, 36 parts of ethyl acrylate and 2 parts of acrylic acid as raw materials and using toluene as a solvent. 78 parts of this terpolymer and charge transport material:
22 parts of N, N'-diphenyl-N, N'-bis- (m-tolyl) benzidine were dissolved in 500 parts of toluene. The resulting solution was applied onto the charge generation layer with a wire bar and dried at 110 ° C. for 15 minutes to give a film thickness of 8 μm.
A heat-softened layer was formed. Then, a mixture of 1 part of indium oxide-tin oxide (ITO) powder, 6 parts of the terpolymer, 2 parts of the charge transport material, 50 parts of toluene and 50 parts of butanol was treated with a ball mill to obtain a dispersion liquid. . The average particle size of the ITO particles in the dispersion was 0.35 μm. This dispersion was applied on the heat-softened layer by a wire bar so that the film thickness after drying would be 0.6 μm.

The image holding member thus produced is
In the process shown in FIG. 2, after being charged under the condition of −600 V, the image was exposed by modulating with a diode laser beam so that the black part of the document emits light and the white part of the document disappears. Then, it was passed over a heat roll kept at 115 ° C. for 5 seconds in a dark place to perform heat treatment. As a result, the unexposed areas of the ITO
The particles moved to the substrate side. In this way, the storage by writing the image is completed. Using the image-holding member in which the obtained image information was stored, negative charge was applied as shown in FIG. 5 and the surface potential was measured.
It was 0V, and the non-moving part was -600V. This image holding member was subjected to continuous copying by steps such as charging, toner development, and transfer to paper.

Next, when the information stored in the image holding member became unnecessary, the image holding member in which the image information was stored was reproduced. First, positive charging was performed as shown in FIG. The charging conditions were set so that the particle moving portion was +400 V, and the particles were charged. This was heated at 130 ° C. for 10 seconds. Then, when negatively charged as shown in FIG.
Could be charged to. However, the charging current was slightly higher than when a new image holding member was used. When the image was rewritten using the image holding member reproduced as described above, continuous copying could be performed until the total number of sheets reached 6000.

[0017]

According to the image forming method of the present invention, the image holding member can be regenerated and used. Therefore, as in the conventional image forming method using the image holding member, an image is formed for each use. The holding member can be used repeatedly without being discarded. Therefore, the present invention is useful not only for effective use of resources but also for cost reduction in copying.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an image holding member of the present invention.

FIG. 2 is an explanatory diagram of a process of charging an image holding member.

FIG. 3 is an explanatory diagram of a process of writing an image on an image holding member.

FIG. 4 is an explanatory diagram of a process of heating an image holding member to store an image.

FIG. 5 is an explanatory diagram of a process of charging an image holding member on which an image is written.

FIG. 6 is an explanatory diagram of a process of performing positive charging to reproduce an image holding member on which an image is written.

FIG. 7 is an explanatory diagram of a process of heating after positive charging to regenerate the image holding member.

[Description of Reference Signs] 1 ... Image holding member, 1 '... Image holding member in which image information is stored, 1 "... Reproduced image holding member, 2 ... Substrate, 3 ... Conductive layer, 4 ... Charge generating layer, 5 … Thermal softening layer, 6… Conductive particles,
6a ... moving particles, 6b ... non-moving particles, 7 ... conductive particle dispersion layer, 8 ... negative charger, 9 ... positive charger.

Claims (1)

[Claims] 1. A charge generation layer, a heat-softening layer containing a charge-transporting substance and a heat-softening resin, on a surface of a conductive substrate.
The image holding member, in which conductive particles are dispersed at least sequentially and in which conductive particles are embedded in the vicinity of the surface of the heat-softening layer, is negatively charged to accumulate charges in the conductive particles, and then the image information is handled. After eliminating the charge of the conductive particles,
Heating the heat softening layer to a temperature above the softening point of the heat softening resin,
Conductive particles that have accumulated electric charges are moved in the thermal softening layer to store image information, and the image holding member storing the image information is subjected to electrophotography including a charging, development and transfer process to make a copy. After that, the image holding member in which the image information is stored is positively charged, and then the heat softening layer is heated to a temperature equal to or higher than the softening point of the heat softening resin to heat soften the moved conductive particles again. An image forming method comprising moving the image holding member to an initial state by moving the image holding member to the vicinity of the surface.