JPH0748118B2 - Permanently electrically insulating electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous electro-insulating electrophotographic method which uses a persistent electro-insulating electrophotographic photosensitive member and is capable of making a large number of copies in one latent image formation. .

[Prior art]

There are many known electrophotographic methods using a continuous electrically insulating electrophotographic photosensitive member for making multiple copies. In these methods, when a photoreceptor having a photosensitive layer pre-insulated by heating is exposed, the exposed portion becomes electrically conductive due to a sharp decrease in electrical resistance, and this state remains for a while even after the light irradiation in the exposure is finished. This is a phenomenon that lasts for a while.

As a continuous electrical insulating electrophotographic method utilizing such a phenomenon, for example, Japanese Patent Publication No. 60657/44657 discloses a photosensitive material containing polyvinylcarbazole, an electron-accepting substance and an electron-donating dye compound as a main component on a conductive support. For a continuous electrically insulating electrophotographic photosensitive material provided with a layer, 1) the entire surface of the photosensitive layer is heated and insulated, and then negatively charged, 2) imagewise exposed, and 3) positively charged. After that, the non-exposed portion is positively charged, 4) the formed electrostatic latent image is developed with toner, and then 5) the obtained toner image is transferred to a transfer paper to obtain a copy, and then, These steps 3) to 5) are repeated to obtain many copies.

However, in this method, writing on the photosensitive layer is performed by image exposure, so a considerable amount of light is required, and the optical system is complicated, and it is impossible to write digital data due to image exposure by the lens system. There are drawbacks.

Further, in the conventional connection electrically insulating electrophotographic method, even if a small number (for example, several tens) or a large number (for example, several hundreds) of copies are required, heating for insulating the photosensitive layer is required. A certain amount of heat was added according to the maximum number of copies.
For this reason, since the maximum amount of heat is applied even when copying a small number of sheets, the writing time does not change when copying a small number of sheets or a large number of sheets, and therefore the time to obtain the first copy is also unchanged, which is unreasonable. there were.

[Problems to be Solved by the Invention]

The object of the present invention is to eliminate the above-mentioned drawbacks in the prior art and to perform writing with a thermal head, thereby simplifying the exposure system, reducing the light quantity, and enabling digital writing. It is an object of the present invention to provide a rational connection electrically insulating electrophotographic method which can reduce the heating amount and the writing time and the time for obtaining the first copy.

[Constitution / Operation of Invention]

The continuous electroconnective electrophotographic method of the present invention is applied to a continuous electrically insulating electrophotographic photoconductor in which a photosensitive layer containing a charge transport substance and a conductivity change imparting agent as a main component is provided on a conductive support.
The entire surface of the photosensitive layer is exposed to make it conductive, 2) this surface is imagewise heated by a thermal head to insulate the heated portion, and 3) the entire surface of the photosensitive layer is negatively charged to make the insulated portion negative. After charging, 4) developing the formed electrostatic latent image with positively charged toner, and then 5) transferring the obtained toner image to a transfer paper to obtain a copy, and further 3), 4) above. In the continuous electrical insulating electrophotographic method for obtaining a large number of copies by repeating the steps 5 and 5), the heating amount by the thermal head in the step 2) is changed according to the required number of copies. It is a thing.

If a latent image is formed using the phenomenon described above with the persistently electrically insulating photoreceptor, from another perspective, it is necessary to first expose the entire surface to make the entire photosensitive layer conductive and then correspond to the original image. A method in which the portion to be insulated is heated by heating with a thermal head is also conceivable. FIG. 1 shows a process of forming an electrostatic latent image due to a change in conductivity of a photosensitive layer when light energy and heat energy are applied to a persistent electrically insulating photoreceptor according to such a writing method. As shown in FIG. 2, the photosensitive member used here is one in which a photosensitive layer 25 containing a charge transport material and a conductivity change imparting agent as main components is provided on a conductive layer 24 of a conductive support 23. (A is a photoconductor).

In FIG. 1, the charge transport material, which is one of the components in the photosensitive layer 25, is a so-called P-type semiconductor having a small hole mobility. The other component in the photosensitive layer, the conductivity change imparting agent X ^+-
Takes a stable ionic structure before exposure (for example, in the case of a spiropyran compound, it has a stable ionic structure due to ring opening), acts as a hole trapping agent, and imparts insulating properties to the photosensitive layer. When the entire surface of the photosensitive layer 25 in such an insulating state is irradiated with light in the absorption wavelength range of the conductivity change imparting agent [FIG. 1 (a)], the conductivity change imparting agent temporarily changes from a stable ionic structure due to a photochemical reaction. Changes to a chemically stable nonionic structure (for example, in the case of a spiropyran compound, the ring is closed to be in a temporarily stable state). This non-ionic structure conductivity-changing agent no longer acts as a hole trapping agent and becomes so-called conductive.

In this way, the photosensitive layer 25, which is made entirely conductive, is attached to the thermal head 2.
When imagewise heated by, the conductivity change imparting agent in the heated portion (inside the dotted line) has a stable ionic structure (for example, in the case of spiropyran compounds, it becomes an ionic structure by ring opening), and as a hole trap agent work. The holes thus injected from the conductive layer 24 into the photosensitive layer 25 are repeatedly trapped and detrapped by the conductivity change imparting agent, so that the mobility is lowered, so that the photosensitive layer in the heated portion becomes insulative [FIG. )].

Next, when the surface of the photosensitive layer 25 is uniformly negatively charged by the charger 4, the photosensitive layer in the insulating portion is negatively charged. Therefore, a charge distribution corresponding to the image, that is, an electrostatic latent image is formed on the heated portion of the photosensitive layer [FIG. 1 (c)]. Or this conductive and insulating state is stable in the dark for a long time,
Therefore, the photoreceptor used in the method of the present invention has a memory property.

The present invention utilizes such a heat-sensitive method, and after load-charging the insulating portion of the photosensitive layer selectively insulated by the thermal head as described above, development by a conventional method,
If the transfer is performed, a copy is obtained. The conductive and insulating portions of the photosensitive layer are retained during multiple copies. In addition, by exposing the entire surface after copying many sheets,
The photoconductor is restored to its original state. Therefore, the photoconductor can be used for another multiple copy many times without replacing the photoconductor with a new photoconductor each time one multicopy is completed.

Next, the method of the present invention will be described in more detail with reference to the embodiment shown in FIG. The photoreceptor used here is in the form of a sheet, for example, In ₂ O ₃ --SnO on a polyester film support.
₃ (ITO) is vacuum-deposited to provide a conductive layer, and a photosensitive layer made of polyvinylcarbazole and a spiropyran compound is further provided thereon.

The photoconductor sheet A is sent out by the photoconductor drive roller 11 and wound up by the photoconductor drive roller 10.
It is wound around the rotating drum 1 made of Al. Incidentally roller
11 is the unused portion of the photosensitive sheet A, while the roller 10 is the used portion. Also these rollers 10,1
1 rotates together with the drum when the rotating drum 1 rotates, but each drum can be rotated independently when the drum is stopped.

The thermal head 2, the platen roller 3, the charging device 4, the developing device 5, the transfer device 6, the separating device 7, the cleaning device 8 and the entire surface exposure device 9 are provided on the rotary drum 1 so as to surround the drum along the outer circumference of the drum. Are arranged in sequence.

When copying is started, the photosensitive sheet A sent from the driving roller 11 is entirely irradiated by the entire surface exposure device 9, so that the entire surface of the photosensitive layer is made conductive.

In order to convert an image of an original (not shown) on the contact glass 22 into an electric signal, the original image is reflected by the light of the light source 16 for illuminating the original, the reflector 15, the original, the first mirror 17, the second mirror 18
Then, an image is formed on the photoelectric conversion element 21 by the lens 20 through the third mirror 19. The image information converted into an electric signal is subjected to data processing by the control circuit 26 shown in FIG. 4 and then transferred to the thermal head 2, where the heating elements at the locations corresponding to the black dots of the image generate heat. The photoconductor sheet A is brought into close contact with the thermal head 2 by the platen roller 3. After the heating of one line is completed, the image reading is also advanced by one line, and the photosensitive sheet A is also moved by one line by the drive rollers 10 and 11, and the same exposure, reading and writing are performed. The conductive portion formed by exposure to light on the photosensitive member and the insulating portion formed by heating are kept in their respective states during copying of a large number of sheets.

When the writing by the thermal head 2 is completed, the head 2
Moves in the direction of the arrow and leaves the photoconductor sheet, and the copying process is started. The rotating drum rotates, and the heated portion of the photosensitive member is selectively negatively charged by leaving the corona of the negative charging device 4. A voltage of about -6 KV is applied to this device. The drum further rotates, and the developing device 5 causes the page charge toner to adhere to the charged portion. The developing roller 5a in the developing device 5 is biased to a negative polarity to prevent background stains.

The toner on the photoconductor is transferred to the transfer paper (plain paper) 14 fed from the paper feeding device 13 by the transfer device 6 which performs negative corona discharge. The toner remaining without being transferred is removed by the cleaning device 8.

Thereafter, by repeating the same steps from charging without performing the entire surface exposure and writing with the thermal head, it is possible to carry out continuous multiple copy without writing.

When a series of copying is completed and a new original is to be copied, by exposing the entire surface-writing by the thermal head,
It is possible to copy using the same photoconductor. After copying a predetermined number of sheets with the same photoconductor, the photoconductor sheets on the rotary drum 1 can be replaced by the drive rollers 10 and 11 if necessary.

In the continuous electric insulation electrophotographic method of the present invention as described above, the heating amount is changed by the thermal head depending on whether the required number of copies is small or large, but the effect will be described.

In the persistent electrically insulating photosensitive member used in the method of the present invention, the insulating property is lowered and the surface potential is decreased each time the charging process is repeated, that is, the copying process is repeated, and the surface potential is reduced by the heating amount for making the insulating property. It has the characteristic that the amount of decrease of changes. That is, in this type of photoconductor, when the heating amount is large, the decrease in the surface potential during repeated charging is small, and conversely, when the heating amount is small, the decrease in the surface potential increases. This situation will be described with reference to the drawings. In FIG. 6, the surface potential when the photosensitive layer is heated by the maximum heating amount and the maximum number of copies N ₂ is obtained is Vp volt. If the surface potential can secure Vp, there will be no effect on the copied image. If the heating amount is reduced here, that is, if the heating time is shortened, the decrease in the surface potential increases each time charging is repeated, but while the surface potential is up to Vp,
That is, until the number of N ₁ is not influence on the image, necessary number of copies would be less amount of heat as long as N ₁ or less.

In this way, by changing the heating amount according to the required number of sheets, the formation time of the insulating pattern corresponding to the original,
Therefore, it is possible to shorten the time until the first copy is obtained.

FIG. 5 shows a flowchart for carrying out the method of the present invention by changing the heating amount by the thermal head as described above.

Next, the constituent materials of the persistent electrically insulating photosensitive member used in the method of the present invention will be described in detail.

In the field of electrophotography, Al is often used as a conductive support or conductive layer, but it is disadvantageous because it forms an oxide film on the surface and acts as a barrier layer for hole injection. Therefore, as the material of the conductive layer of the photoreceptor used in the method of the present invention, ITO and other Z
n, Ti, Au, Ag, Fe, Sn, Cu, In and other metals or semiconductor elements,
Alternatively, oxide semiconductors such as SnO ₂ , In ₂ O ₃ , ZnO, TiO, NiO, WO, and V ₂ O ₅ can be exemplified.

The charge transporting material used in the photosensitive layer includes the following (I),
Examples are the substances shown in (II), (III) and (IV).

(I) Polymer photoconductor Polyvinyl carbazole, poly N-ethylenically unsaturated group substituted carbazoles, poly N-ethylenically unsaturated group substituted phenothiazines, polyvinyl pyrene and the like.

(II) Low-molecular-weight photoconductors Oxodiazoles, hydrazones, pyrazolines, triphenylmethane derivatives, etc. substituted with alkylaminophenyl groups and the like.

(III) Polymer conductor Polyacetylene, polydiacetylene, etc.

On the other hand, the conductivity change imparting agent is a substance that reversibly changes the structure between nonionic and ionic by light or heat energy, and a spiropyran compound or a derivative thereof can be exemplified.

The compounding ratio of the charge transporting substance and the conductivity change imparting agent in the photosensitive layer can be selected according to the function to be obtained and the intended use, but usually, the conductivity imparting agent is 0 per mol of the charge transporting substance. .
01 to 1 mol is suitable. The charge transport material and the conductivity change imparting agent are used together with an appropriate binder (silicone resin, polycarbonate resin, polyacetal resin, etc.) to form a photosensitive layer.

The shape of the photoreceptor may be a sheet shape, a drum shape, a plate shape, a belt shape, or the like.

[Advantageous effects of the invention]

According to the continuous electrically insulating electrophotographic method of the present invention, since writing is performed by the thermal head, the exposure system can be simplified, the light amount can be reduced, and digital writing can be performed. Also, since the writing time is changed according to the required number of copies,
The latent image formation time and the time until the first copy is obtained can be shortened. Further, for the same reason, the total heat generation amount of the head is reduced, and the life of the head can be extended.

[Brief description of drawings]

FIG. 1 is an explanatory view of a latent image forming process in the method of the present invention, FIG. 2 is a sectional view of an example of a continuously electrically insulating electrophotographic photosensitive member used in the method of the present invention, and FIG. 3 is a method of carrying out the method of the present invention. FIG. 4 is a control circuit diagram for processing image information sent to the apparatus of FIG. 3, FIG. 5 is a flow chart for carrying out the method of the present invention, and FIG. 6 is a thermal head. FIG. 6 is a diagram showing a change in surface potential of a photosensitive layer due to a difference in heating amount of FIG. A: Permanently electrically insulating electrophotographic photosensitive member in which a photosensitive layer 25 is provided on the conductive layer 24 of the conductive support 1 ... Rotary drum, 2 ... Thermal head 4 ... Charger, 5 ... Developing device 6 ... Transfer device, 8 ... Cleaning device 9 ... Full exposure device 10, 11 ... Photoconductor drive roller 12 ... Fixing device, 14 ... Transfer paper (plain paper) 26 ... Control circuit

Claims (1)

[Claims] 1. A continuous electrically insulating electrophotographic photosensitive member comprising a conductive support and a photosensitive layer containing a charge-transporting substance and a conductivity-change imparting agent as main components. 1) The entire surface of the photosensitive layer is exposed. To make the entire surface electrically conductive, 2) heat this surface imagewise with a thermal head to insulate the heated portion, 3) negatively charge the entire photosensitive layer to negatively charge the insulating portion, and 4) form it. Developed electrostatic latent image with positively charged toner, and then
5) A continuous electric insulating electrophotographic method in which the obtained toner image is transferred to a transfer paper to obtain a copy, and then the steps 3), 4) and 5) are repeated to obtain a large number of copies. 2. In the continuous electro-insulating electrophotographic method, the heating amount by the thermal head in the step 2) is changed according to the required number of copies.