JPH0466022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous conductive or memory type image forming method and an image forming material used therein.

The persistent conductive image forming method utilizes the phenomenon that when a certain type of photosensitive material is exposed to light, a persistent conductive image (that is, has a memory effect) is formed in the exposed area. The conductive image (latent image) can be visualized by various developing methods commonly used in electrostatography. Various types of photosensitive materials have been proposed for use in this method, but a typical one is to form a photosensitive memory layer containing an organic photoconductive substance and a memory effect imparting agent on a conductive substrate. are known (for example, U.S. Pat. No. 3,879,201;
No. 3997342, each specification, etc.). As the organic photoconductive substance, a polymeric photoconductor such as polyvinylcarbazole or a low molecular weight photoconductor such as oxadiazole dispersed in an electrically insulating binder is used, and as a memory effect imparting agent, ,
Various proton donors are known.

A drawback of the above-mentioned image forming materials utilizing sustained conductivity is that the amount of exposure required to obtain a desired sustained conductivity image is quite large, on the order of several tens of mJ to 100 mJ/cm ² .

The present inventors have already developed several techniques in order to eliminate the drawbacks of such persistently conductive image forming materials and to improve the exposure sensitivity. for example,
The specification of Japanese Patent Application No. 52-167010 describes a method of corona charging before exposing the photosensitive memory layer;
- Japanese Patent Application No. 17358 discloses an image forming material in which a photoconductive layer is laminated with a photosensitive memory layer to form a relatively thin photoconductive layer that does not have a memory effect; Each of these discloses a method of performing exposure while applying a voltage to. Although these techniques can improve the exposure sensitivity to a certain extent, they are still far from sufficient or have the disadvantage of being subject to operational constraints.

In view of the above-mentioned circumstances, the main object of the present invention is to provide a sustained conductive image forming material with further improved exposure sensitivity and an image forming method using the same.

As a result of research for the above-mentioned purpose, the present inventors have found that arylmethane dyes containing a carbazole ring in their structure not only function as memory effect imparting agents, but also have a 0.1 m
To provide a photosensitive memory layer that exhibits a significantly increased photosensitivity of approximately 100 times as much as J/cm ² compared to a conventional photoreceptor (image forming material) having a memory function, and to The formation of a persistent conductive image involves the hole injection effect from the conductive substrate to the photosensitive memory layer due to the interaction between the photosensitive memory layer and the conductive substrate, especially when the surface resistivity is 10 ²
It has been found that a high hole injection effect can be obtained when using a conductive substrate in the range of ~10 ⁶ Ω/cm ² .

The image forming material having a memory function of the present invention is based on the above-mentioned findings, and more specifically, an organic photoconductive material is coated on a conductive substrate having a surface resistivity of 10 ² to ^{10 6} Ω/□. and a photosensitive memory layer containing a memory effect imparting agent consisting of an arylmethane dye represented by the following formula (1).

(In the formula, at least one of the groups R ₁ , R ₂ , and R ₃ is a phenyl group substituted with N at the para position represented by the following formula (2) or (3), (In formulas (2) and (3), R ₄ to _{R 8} are an alkyl group, an aryl group, or hydrogen, respectively) Up to two groups R ₁ , R ₂ , and R ₃ are an alkyl group, an aryl group, or an aralkyl group. or can be hydrogen;
X ^- represents an anion. ) Further, the image forming method of the present invention is characterized in that the photosensitive memory layer of the image forming material is subjected to pattern exposure to form a sustained conductive image in which holes are injected into the exposed areas.

Although the reason why a sustained conductive image with photosensitivity can be obtained according to the present invention is not necessarily clear, it is presumed as follows. That is, the photosensitive memory layer containing the organic photoconductive material and the memory effect imparting agent is a p-type semiconductor with high hole mobility.

Holes are generally injected into this photosensitive memory layer from a conductive substrate. Only those that are larger than the film thickness of the photosensitive memory layer (given by the negative corona charge)) appear on the surface and are used to impart conductivity, that is, to offset the negative corona charge, contributing to a reduction in the acceptance potential. . When irradiated with light in the absorption wavelength range of the memory effect imparting agent, the hole injection efficiency from the conductive substrate increases due to physical and chemical changes in the interaction between the memory effect imparting agent and the conductive substrate. In the exposed area, the acceptance potential of the photosensitive memory layer due to corona charging appears to decrease as the hole injection efficiency increases. This state of increased hole injection efficiency due to light irradiation is
In the dark, it lasts for a relatively long time and exhibits a so-called memory effect, but this state is reversible, and the hole injection efficiency before light irradiation is restored by thermal energy or the like, and the memory is erased. In the case of the present invention,
The use of a memory effect imparting agent consisting of an arylmethane dye significantly increases the rate of change in hole injection efficiency during exposure, which is considered to be one reason for the high photosensitivity. In addition, if the surface resistivity of the conductive substrate is too high, efficient hole injection will not take place.
If it is too small, the acceptance potential of the photosensitive memory layer will decrease even in areas other than the exposed areas, making it impossible to obtain the desired contrast. This is considered to be the reason why a conductive substrate having a specific surface resistivity gives excellent results in combination with a memory effect imparting agent consisting of an arylmethane dye.

The present invention will be explained in more detail below. In the following description, "parts" representing compositions are based on weight unless otherwise specified.

An example of the image forming material of the present invention is formed by forming a photosensitive memory layer 2 on a conductive substrate 1, as shown in FIG.

As mentioned above, the conductive substrate 1 does not act simply as an electrode, but also plays an important role as one of the functional elements constituting the image forming material, and is capable of injecting holes into the photosensitive memory layer and with a moderate amount of heat. 10 ² ~ to give charging ability to the photosensitive memory layer
It is necessary to have a surface resistivity of 10 ⁶ Ω/□.

In this sense, highly conductive materials such as Au and Ag are unsuitable. Furthermore, Al, which is the conductive substrate material most commonly used in electrostatic photographic materials, is disadvantageous because a passive film is formed on the surface by oxidation and acts as a barrier layer against hole injection.
As the conductive substrate 1, as shown in FIG. 2, it is preferable to use a sheet or substrate 1a of glass or transparent plastic such as polyester or polycarbonate, on which a film 2a of a conductive material is formed. As conductive materials, Zn,
Metal or semiconductor elements such as Ti, Fe, Sn, Cu, In, or SnO ₂ , In ₂ O ₃ , ZnO, TiO, WO,
Materials such as oxide semiconductors such as V ₂ O ₅ that stably provide a surface resistivity of 10 ² to 10 ⁶ Ω/□ are preferably used alone or as a composite material of two or more kinds. Among these, oxide semiconductors are preferably used, and in particular, an In ₂ O ₃ -SnO ₂ composite thin film with a resistivity of about 10 ⁴ Ω/□ is a preferred conductive film material.

The photosensitive memory layer 2 contains an organic photoconductive substance and a memory effect imparting agent. Organic photoconductive materials include, as mentioned above, polymeric photoconductors themselves or dispersions of low molecular photoconductors in insulating binders. In addition to the above-mentioned polyvinylcarbazole, in place of the vinyl group, polymer photoconductors include
Poly N-ethylenically unsaturated group-substituted carbazoles, which are polymers of N-substituted carbazole containing ethylenically unsaturated groups such as allyl groups and acryloxyalkyl groups, poly N-acrylphenothiazines,
PolyN-ethylenically unsaturated group-substituted phenothiazines such as polyN-(β-acryloxy)phenothiazine, polyvinylpyrene, and the like are used. Among these, poly N-ethylenically unsaturated group-substituted carbazoles, particularly polyvinyl carbazole, are preferably used.

Further, as the low molecular weight photoconductor, oxadiazoles, triphenylmethane derivatives, etc. substituted with an alkylaminophenyl group or the like are used. These low molecular weight photoconductors contain, for example, about 1 to 10 parts of silicone resin, styrene-butadiene copolymer resin,
When combined with an electrically insulating binder resin such as saturated or unsaturated polyester resin or polyvinyl acetal resin, it can be used as a film-forming organic photoconductive substance.

On the other hand, as the memory effect imparting agent, an arylmethane dye having the following structural formula (1) is used.

As mentioned above, in the above formula, at least one of the groups R ₁ , R ₂ , and R ₃ is a phenyl group substituted with N at the para position represented by the following formula (2) or (3), (In formulas (2) and (3), R ₄ to _{R 8} are an alkyl group, an aryl group, or hydrogen, respectively.) Up to two groups R ₁ , R ₂ , and R ₃ are an alkyl group, an aryl group, or an aralkyl group. or hydrogen.

Also, X ^- generally indicates an anion, e.g.
Halogen ions such as Cl ^- , Br ^- , I ^- ; BF ₄ ^- ,
Covalent bonds such as PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^-, etc. are complex anions; examples include MnXm ^- (M is a metal, X is a halogen, m and n are integers). Among them, BF ₄ ^- ,
Covalent complex anions such as PF ₆ ^- and SbF ₆ ^- are preferred because they provide a photosensitive memory layer with high photomemory responsiveness. For the same reason, arylmethane dyes in which R ₁ and R ₂ are N-ethyl-substituted carbazole groups and R ₃ is a phenyl group, or
Arylmethane dyes in which R ₁ and R ₂ are p-dimethylaminophenyl groups and R ₃ is a phenyl group are particularly preferably used.

These memory effect imparting agents are used in an amount of 0.0001 to 1 mole of photoconductor (or 1 mole of polymerized units when the photoconductor is a polymer) in the organic photoconductive material.
The image forming material of the present invention is obtained by mixing 0.01 mol of the mixture, diluting the mixture with a solvent if necessary, and applying the mixture to a conductive substrate using a wire bar, doctor blade, etc. to form a photosensitive memory layer. The thickness of the photosensitive memory layer is preferably about 1 to 20 microns.

Note that the photosensitive memory layer 2 itself can be divided into a plurality of layers. In this case, as shown in FIG. 3, it is preferable to have a layer structure in which a photoconductive layer 2b having a relatively thin thickness and having no memory effect is provided on a layer 2a having a composition similar to that of the photosensitive memory layer. used.

Next, the image forming method of the present invention using the image forming material thus obtained will be described.

In order to obtain a sustained conductive image according to the method of the invention, a light source 3 is applied to the photosensitive memory layer 2 of the imaging material, as shown in FIG. 3 corresponding to FIG.
Pattern exposure may be performed by irradiating light through the transparent original 4. If the conductive substrate 1 is transparent, the exposure of the photosensitive memory layer 2 can also be performed through the conductive substrate 1 (not shown). As the light source 3, a continuous spectrum light source such as a white lamp, a xenon lamp, or a halogen lamp can be used.In addition, an arylmethane dye containing a carbazole ring, which is a memory effect imparting agent, in its structure absorbs light in the visible range (sensitivity ), monochromatic light in the visible range can also be used. Representative examples of such monochromatic light include Ar laser (514nm),
Ruby laser (488nm), dye laser, He-
Ne laser (633 nm) is an example of laser light. In this case, direct pattern exposure can be performed by beam scanning by utilizing the laser's characteristic of high energy density per unit area.

As mentioned above, the image forming material of the present invention can obtain a good memory effect at an exposure dose of about 0.05 to 0.1 mJ/cm ² even without the addition of a sensitizer, and the resulting conductive image remains stable for 1 to 3 hours. last. Further, in order to further increase the sensitivity, reverse charging (positive charging) may be performed in advance before pattern exposure. This further improves the sensitivity by about 20%. in this case,
After performing reverse charging, the potential may be returned to zero, or exposure may be performed with the reversely charged state. Furthermore, as described in Japanese Patent Application No. 57-5233, exposure may be carried out by bringing a negative electrode into contact with the photosensitive memory layer and applying a voltage.

The sustained conductive image obtained as described above is generally a latent image, but a visible image can be obtained by utilizing it as an electrostatic photograph or an electrostatic printing master. In other words, a negative corona discharge is applied to the photosensitive memory on which the persistently conductive image has been formed to form a reversed electrostatic latent image in the non-exposed area, which is then developed by adhering toner powder and transferred to paper, etc. Various xerographic development methods can be applied as they are. Furthermore, once a sustained conductive image is obtained by the method of the present invention, a large number of copies can be obtained by repeating charging development and transfer.

In addition, since the conductive image and development can be separated as a method that takes advantage of the memory function, it is also expected to be applied as a printing plate that allows partial printing.
As other developing methods, methods such as electrodeposition development, electrolytic development, and electrophoretic development can also be used by utilizing the difference in conductivity between exposed areas and non-exposed areas.

Furthermore, the image forming material of the present invention has the following characteristics:
One of the advantages is that the memory can be easily erased. Methods for erasing the memory include a method of reversely charging (positively charging) the photosensitive memory layer after the formation of a sustained conductive image, or a method of heating the photosensitive memory layer using a hot plate, heated roller, etc. at 100 to 150°C. etc.

In particular, when erasing the memory by heating, if a temperature of 120 to 150° C. is used, complete memory erasure can be achieved in just 1 to 5 seconds.

The present invention will be explained in more detail with reference to the following examples.

Example 1 9,9'-diethyl-3,3'-dicarbasyl phenylmethyltetrafluoroborate (memory imparting agent) 2 mg Polyvinylcarbazole (photoconductive substance; Tubicol manufactured by Takasago Dye Co., Ltd.) 1 g CHCl ₃ 25 g Above Create a mixed solution with the composition in the dark,
In ₂ O ₃ −SnO ₂ was applied to a polyester film (surface resistivity 10 ⁴ Ω/□, manufactured by Teijin Ltd., transparent conductive film) using a wire bar, and dried with ventilation at 50°C for about 1 hour. An image forming material (photosensitive material) having a photosensitive memory layer with a film thickness of about 10 μm was formed.

This image forming material was allowed to stand for another day in order to dry completely, and then the following measurements were carried out according to the image forming method of the present invention.

That is, the exposure was performed by irradiating light of 633 nm and 0.1 mw/cm ² using an interference filter and a halogen lamp to make the entire surface of the photosensitive memory layer conductive.

The surface potential before and after exposure was measured with a corona charger (rotary paper analyzer, manufactured by Kawaguchi Electric Co., Ltd.).

As a result, before exposure, after a photoreceptor with 700V (-) charge acceptability was given an exposure dose of 0.1mJ/ ^cm2 ,
The charge acceptance was 140 V (-), and when considered as an image, a contrast potential of 560 V was obtained between the unexposed area and the exposed area. The state of reduced charge acceptance obtained in this way is stable in the dark state,
Even after 3 hours, the voltage recovered to only 200V (-), and a contrast potential of 500V was obtained even on this staircase.

Separately, the photosensitive memory layer of the above-mentioned image forming material is subjected to contact exposure through a pattern film, and then corona charged and developed with (-6kv) positive polarity electrophotographic wet toner to cover the unexposed areas on the surface of the photosensitive material. A toner image was obtained. In that case, the resolution is 15 lines/
It was warm in mm.

Example 2 In a photosensitive material similar to that used in Example 1, if the material is positively charged before exposure and then exposed, or once the surface charge is canceled by negative charging and then exposed, the exposed area The charge acceptance is 70V(-) (unexposed area = 700V(-)),
A sensitizing effect was obtained.

Example 3 A photosensitive material similar to that used in Example 1 whose charge acceptance decreased to 70 V (-) due to exposure was positively charged (+6 kv) for 5 minutes, and when exposed to light at 140°C. When passed through a heated roller for 3 seconds,
The charge acceptor was rotated to 700V before exposure and memory erase was performed.

Comparative Example In the photosensitive material used in Example 1, the conductive substrate was replaced with an Al-deposited Mylar film instead of the In ₂ O ₃ -SnO _2- deposited polyester film. As a result, the charge reception after exposure was improved. No decrease in sexual performance was observed, and no memory effects occurred.

Example 4 In the photosensitive material used in Example 1, the light source was a He-Ne laser of 633 nm instead of a halogen lamp.
Direct optical recording was performed using beam manipulation. As a result, it was possible to form an image with an exposure amount of 500 erg/cm ² .

Example 5 9,9'-diethyl-3,3'-dicarbasylphenylmethylhexafluorophosphide 4 mg Polyvinylcarbazole 1 g CHCl ₃ 25 g A mixed solution having the above composition had the same conductivity as that used in Example 1. On the board, gap width 4mil
The film was applied using a doctor blade and completely dried to form a photosensitive memory layer with a thickness of 15 μm. 500 nm, 0.1 on the photosensitive memory layer of the obtained photosensitive material
After irradiating light with an intensity of mw/cm ² at 0.1 mJ/cm ² ,
As a result of applying a DC voltage of 100V between the electrophotographic wet toner of negative polarity and the photosensitive substrate (conductive substrate) using an aluminum plate as an anticathode, the toner adheres to the exposed area and electrodeposition occurs. It has been confirmed that this will be done.

Example 6 1,2-P-dimethylamino-3-phenylmethane, tetrafluoroborate (malachite green-4-fluoroborate) 3 mg Polyvinylcarbazole 1 g CHCl ₃ 25 g A mixed solution having the above composition was tested for surface resistivity.
It was coated on a NiO substrate of approximately 10 ⁴ Ω/□ using a doctor blade with a gap width of 4 mil, and was completely dried to form a photosensitive memory layer with a thickness of 10 μm. 640nm, 0.1 to the photosensitive memory layer of the obtained photosensitive material
A 0.5 mJ/cm ² pattern exposure was performed using mw/cm ² light.

After storage for 3 hours, it was charged (-) and developed with toner. As a result, an image formation rate of 15 lines/mm was obtained.

[Brief explanation of drawings]

1 to 3 are cross-sectional views in the thickness direction of image forming materials according to embodiments of the present invention, and FIG. 4 is a cross-sectional view of the image forming material for explaining the pattern exposure step in the image forming method of the present invention. It is a sectional view in the thickness direction. 1... Conductive substrate (1a... Transparent substrate, 1b...
... conductive film), 2 ... photosensitive memory layer, 3 ... light source, 4 ... transparent original.

Claims (1)

[Claims] 1. Surface resistivity that allows hole injection is 10 ² ~
A photosensitive memory layer containing a memory effect imparting agent consisting of an organic photoconductive substance and an arylmethane dye represented by the following formula (1) is provided on a conductive substrate having a resistance of 10 ⁶ Ω/□. An image forming material that has a memory function. (In the formula, at least one of the groups R ₁ , R ₂ , and R ₃ is a phenyl group substituted with N at the para position represented by the following formula (2) or (3), (In formulas (2) and (3), R ₄ to _{R 8} are an alkyl group, an aryl group, or hydrogen, respectively) Up to two groups R ₁ , R ₂ , and R ₃ are an alkyl group, an aryl group, or an aralkyl group. or can be hydrogen;
X ^- represents an anion. 2. The image forming material according to item 1 above, wherein the conductive substrate has a conductive metal oxide film. 3. The image forming material according to item 1 or 2 above, wherein the photosensitive memory layer is composed of a plurality of layers, and one of the layers contains a memory effect imparting agent. 4 A photosensitive memory layer containing a memory effect imparting agent consisting of an organic photoconductive substance and an arylmethane dye represented by the following formula (1) on a conductive substrate having a surface resistivity of 10 ² to 10 ⁶ Ω/□. 1. A memory-type image forming method, which comprises performing pattern exposure on a photosensitive memory layer of an image forming material provided with the above to form a sustained conductive image in which holes are injected into exposed areas. (In the formula, at least one of the groups R ₁ , R ₂ , and R ₃ is a phenyl group substituted with N at the para position represented by the following formula (2) or (3), (In formulas (2) and (3), R ₄ to _{R 8} are an alkyl group, an aryl group, or hydrogen, respectively) Up to two groups R ₁ , R ₂ , and R ₃ are an alkyl group, an aryl group, or an aralkyl group. or can be hydrogen;
X ^- represents an anion. ) 5 The fourth step of negatively charging the photosensitive memory layer after pattern exposure and forming a negatively charged image in the non-exposed area.
Section method. 6. The method of item 5 above, in which toner development is performed after negative charging. 7. The method according to any one of items 4 to 6 above, wherein after pattern exposure, the persistent conductive image is erased by positively charging or heating the photosensitive memory layer. 8. The method according to any one of items 4 to 7 above, wherein the photosensitive memory layer is positively charged before pattern exposure.