JPH01225975A - Wet type electrophotographic transfer method - Google Patents

Abstract

PURPOSE:To reduce image flow and image disturbance caused by corona discharge before transfer by providing a drying process reducing the quantity of carrier liquid of the developer on a photosensitive body between a developing process and a precharging process and specifying the quantity. CONSTITUTION:The drying process reducing the quantity of carrier liquid of the developer on the photosensitive body is provided between the developing process and the precharging process. The quantity of the carrier liquid of the developer on the photosensitive body is 2-20mg per 1mg of the solid component of the toner particles, i.e., the quantity of residual liquid is controlled to be 2-20mg/mg (toner weight). When the quantity of the residual liquid is less than that, transfer is not enough and transfer unevenness is generated. When it exceeds that, toner is scattered by the subsequent precharging and image flow is generated at the time of transfer. Thus, transfer images with high quality which have less disturbance caused by scattering of toner and less image flow due to surplus liquid can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a wet transfer method using a liquid developer, and more particularly to a wet transfer method with excellent transferred image quality.

"Prior Art" Conventionally, the following methods are known for developing an electrostatic latent image on a photoreceptor with a liquid developer and transferring the developed image to a transfer material such as a transfer material. .

One method is to develop the electrostatic latent image on the photoreceptor with a liquid developer, and then overlap the developed image on the photoreceptor with the transfer material while enough carrier liquid remains to perform corona transfer or bias roller transfer. One example is a method of transcribing the image.

In this method, flow may occur in the carrier liquid present between the transfer material and the photoreceptor during transfer, resulting in flow in the transferred image.

Another method is to directly bring the developed photoreceptor and transfer material into close contact with each other using a roller.
When in close contact, the carrier liquid on the photoreceptor flows, which may disrupt the image on the photoreceptor or cause flow in the transferred image.

As a method for preventing this drawback, Japanese Patent Publication No. 4A4-/7 Tata No. 1987 discloses a method in which two transfer rollers are provided and a bias opposite to that applied to the roller in the second wood is applied to the roller in the seventh wood. According to this method, disturbances in the transferred image can be prevented to some extent, but it is not sufficient. Also, Tokko Akira! /-4cl1
6j Hiroshi discloses a method in which after development, the thickness of the carrier liquid on the photoreceptor is controlled to 5 to 30 μm using Corona group 'tK, and then the image is transferred. This method improves the drawbacks of the above methods by interposing a sufficient amount of carrier liquid between the photoreceptor and the transfer material without requiring a wet transfer trap, thereby improving transfer efficiency and eliminating unnecessary contact with the transfer material. This reduces the penetration of liquid.

According to this method, the flow of the transferred image due to excess carrier liquid present during transfer is controlled by liquid thickness control.
Although this may be possible to some extent, it has the disadvantage that the image on the photoreceptor is disturbed due to the corona discharge performed to control the liquid thickness. Tokukai Show 3! - Tajiri 71
discloses a method in which a resin solution is interposed between the photoreceptor and the transfer sheet to uniformly control the amount of transfer adhesion, but this method does not sufficiently improve image disturbance during transfer.

Furthermore, when the transfer material obtained by this method is applied to a printing plate, there is a problem that the dissolved resin tends to adhere to the printing plate and cause scumming.

``Problems to be Solved by the Invention'' The first object of the present invention is to prevent artist flow that occurs when an image formed on a photoreceptor with a liquid developer is transferred to a transfer material, and to prevent image distortion due to corona discharge before transfer. An object of the present invention is to provide a transfer method with less disturbance.

A second object of the present invention is to provide a transfer method with excellent transfer efficiency.

Furthermore, a third object of the present invention is to provide a transfer method suitable for producing a high-quality lithographic printing plate with less background smudge.

"Means for Solving the Problem" The present inventors have developed an electrostatic latent image formed on an electrophotographic photoreceptor having a light guide layer on a conductive support, and an electrophotographic image containing at least toner particles and a carrier liquid. The development process involves developing with a liquid developer, which uses corona group t having the same polarity as the toner particles on the photoreceptor.
In the wet electrophotographic transfer method, which consists of a precharging step using K and a transfer step of transferring the image formed on the photoreceptor to a transfer material, a carrier liquid for the developer on the photoreceptor is removed between the development step and the precharging step. A drying step is provided to reduce the amount of the developer carrier liquid on the photoreceptor to the solid content of toner particles/g.
By setting λomit, the object of the present invention was achieved.

The present invention will be described in detail below.

First, a desired potential is applied by a corona charger to a photoreceptor, which will be described later, to form an electrostatic latent image, and the image is developed using a liquid developer. The liquid developer used here is lOΩ・
It contains toner particles consisting of a colorant and a fixing agent in a non-aqueous solvent with an insulating property of more than 100%, a dispersing agent to keep the toner particles stable, and a charge control agent to clarify the polarity of the toner particles and control the charge. Although colorants are generally not necessary when used for lithographic printing,
It is desirable to have one for ease of plate inspection. After development, if necessary, it can be rinsed with a non-aqueous solvent of io Ω or more. This rinsing can remove soluble components such as ionic components and dispersants in the developer.

Next, the developed and optionally syringed photoreceptor is dried to reduce the amount of the developer carrier liquid on the photoreceptor. Examples of drying methods include, but are not limited to, natural drying methods in which the material is left for a certain period of time, methods in which the material is left to dry for a certain period of time, methods in which the product is blown with cold or warm air, methods in which the product is blown with pressurized air, and methods that utilize radiant energy such as infrared rays. . However, methods that disturb the image on the photoreceptor are not preferred. For example, a method using corona discharge of the same polarity as the toner or a corona discharge of the opposite polarity, a method of contacting a roller, etc. are not necessarily preferable because they may disturb the image on the photoreceptor.

The remaining amount of carrier and liquid is 2 to 20 da/■ (toner weight)
It is important to control it so that If the remaining liquid amount is less than this, the transfer will be insufficient and creases and uneven transfer will occur. Further, if the amount is more than this, the toner will be scattered due to the next precharging, and a flow at the end of the image will occur during transfer.

The image on the photoreceptor in which the amount of carrier liquid has been reduced in this manner is subjected to si-recharging by corona discharge having the same polarity as the toner.

This precharging uniformly charges the image on the photoreceptor to the same polarity. At this time, the amount of remaining liquid on the photoreceptor is 2oq/
If the weight of the toner is exceeded, the toner on the image will scatter,
As mentioned above, the image f/o is distorted. This precharge step is effective in increasing transfer efficiency during the next transfer. The precharged photoreceptor is overlapped with a transfer material and the image is transferred to the transfer material using electrostatic transfer or by applying a voltage directly to the transfer material if the transfer material is conductive. The transferred image is fixed by heating, solvent vapor, or the like.

As described above, in the present invention, an electrostatic latent image formed on a photoreceptor is processed through a development step, which may optionally include a rinsing step after the development, to reduce the amount of remaining liquid on the photoreceptor to 1 to 2 Qη/. (toner weight)
The wet transfer method consists of a drying process in which the toner is dried, a precharging process using a corona discharge of the same polarity as the toner, and a transfer process in which the toner is transferred to a transfer material. By this transfer method, it was possible to obtain a high-quality transferred image with less image disturbance caused by toner scattering and less image flow caused by excess liquid. Furthermore, it was possible to transfer with high transfer efficiency.

Although it is not fully understood why such an effect is achieved, the present inventors think as follows.

The present inventors discovered that when transferring an image developed with a liquid developer, if precharging is applied after a certain period of time after development, toner scattering will be reduced, and that the toner should be precharged after a certain period of time. There is no toner scattering when charging, but
It was found that the transfer efficiency decreased and uneven transfer occurred.

There are times when precharging does not cause toner scattering and times when uneven transfer does not occur, and these differ depending on the type of developer carrier liquid, and when rinsing is performed, it depends on the type of rinsing liquid used. I found something different. Specifically, this will be explained in Examples.

It is desirable that the precharge be applied to the same polarity as the toner. The amount of precharging to be applied cannot be determined as it varies depending on the type of photoreceptor and the type of developer, but it is approximately ±≠, j~7. □KV (distance between photoreceptor and wire 10u).

In the transfer process, the photoreceptor and the transfer material are brought into close contact or separated by a certain distance, and a corona discharge with a polarity opposite to that of the toner particles is applied from the transfer material side, or a voltage with a polarity opposite to that of the toner particles is applied if the transfer material is conductive. and perform the transcription.

The photoreceptor used in the present invention includes well-known organic photoconductors and inorganic photoconductors.

A dielectric material charged with a charging needle can also be used.

Organic photoconductors include a wide variety of well-known organic photoconductors. A specific example is [Research Disclosure J (
Re5earch I)isclosure) magazine +t
There are substances described in oy3r (Article titled "Electrophotographic Elements, Materials and Processes", issue 1973, page 61 et seq.).

For example, poly-N-vinyl carbashield 2. ≠, 7-) An electrophotographic photoreceptor consisting of li-nitrofluor and lentur-on (US Pat. No. 3,4Lt≠, 237), poly-N-vinylcarbazole sensitized with a pyrylium salt dye (%Kiakihiro?- 26611), an electrophotographic photoreceptor whose main component is an organic pigment (% Kaisho≠2-37j≠3), an electrophotographic photoreceptor whose main component is a eutectic complex consisting of a dye and a resin (Japanese Patent Application Laid-open No. 4
'7-1073! r), an electrophotographic photoreceptor in which copper 7-thalocyanine is dispersed in a resin (%Ko-shoz, t-/j47), and the like. Other publications include Electrophotography Society Journal, Volume 25, No. 3 (
Examples include substances described on pages 62 to 76 of Iriri.

As the inorganic photoconductor used in the present invention, "Electro-photography J"
Typical examples include various inorganic compounds disclosed in Phys. J R. Specific examples include zinc oxide, zinc sulfide, cadmium sulfide, selenium, selenium-tellurium alloy, selenium-arsenic alloy, selenium-tellurium-arsenic alloy, and the like.

In addition, amorphous silicon can also be mentioned.

Any known developer can be used as the liquid developer used in the present invention. For example, special public Sho 3J-131/
1 special public show 33-/j hiro 24L% special public show! 0-4LOO/
7. Tokukai Sho≠Tata r1. Jl/-1 Unexamined Showa JR-/2
Examples include the developer disclosed in F'AJI, % Kaisho A/-/1024ct. Of these, Japanese Patent Publication No. 4/-/10λ4t
Particular preference is given to liquid developers comprising toner particles having fibers as disclosed in t.

These liquid developers generally include a carrier liquid, a colorant that forms toner particles, a coating made of a polymeric resin that provides fixation properties for the colorant, and a function that promotes the dispersion of toner particles and stabilizes the dispersion. It consists of a dispersant and a load moderating agent that controls the polarity and load tm of the toner particles.

As the coating material, various known resins can be used. Copolymers of ethylene and (meth)acrylic acid, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl acrylate, and copolymers of ethylene and (meth)acrylic acid disclosed in 102≠Ryo Preferred examples include ethylene copolymers such as copolymers of acid esters and terpolymers of ethylene/(meth)acrylic acid/(meth)acrylic esters.

The carrier liquid and rinsing liquid have an electrical resistance of /X10
A non-polar non-aqueous solvent having a resistance of Ω·0 or more and a dielectric constant of 3 or less can be used. Examples of the non-aqueous solvent include solvents such as linear or branched aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons; From the viewpoints of octane, isooctane, decane, isodecane, dodecane, isododecane, nonane, and isoparaffin-based petroleum agents, Isopar E1 Aitsuno ξ-G1 Isopar H, Isopar L (Isopar "l5 Opar J" is a product of Exxon Co., Ltd.) Suitable examples include Tsurupetsioo, Shell Silua/(manufactured by Shell), and the like.

The toner particle coagulation in the developer is not particularly limited, but
90.1-109 per liter of fastener/l. (That is, toner particles iy and carrier liquid/θ0~io.

It becomes ooey. ) Various known charge control agents can be used, and the concentration thereof is from po, oi to 10P1, preferably o, oi-ip, per liter of developer. Furthermore, various known dispersants can be used, and the concentration of the dispersant is determined by the developer l! This is 0.0/~jop.

Preferably o, i to ioy.

The transfer material used in the present invention is not particularly limited, and various materials can be used. For example, plain paper used in PPC copying machines, various surface coated papers, ZnO
Examples include coated paper and aluminum substrates for printing plates.

Among these, aluminum substrates for printing plates can be cited as a preferred transfer material.

In the present invention, since there is a drying step, substantially the entire surface of the transfer material is not wetted with liquid despite the use of a liquid developer. Therefore, the present invention is suitable for producing a lithographic printing plate using a printing substrate as a transfer material. A liquid developer generally contains toner particles dispersed in a carrier liquid, a charge control agent, a dispersed polymer, etc. as dissolved components.

If any of these adheres to the printing plate, it may cause contamination of non-image areas called so-called scumming during printing. The present invention can include a rinsing step if necessary, but even if the rinsing step is not included, these components will remain in the transfer material since it has been substantially dried in the drying step after the development step. There is no transcribing.

All aluminum substrates used in general presensitizing plates (PS plates) can be used as substrates for lithographic printing plates, but the surface must be treated with graining, anodizing, etc. Preferred examples include aluminum substrates made of aluminum.

"Effects of the Invention" By applying the transfer method of the present invention, it is possible to greatly improve the image disturbance caused by toner scattering due to precharging and the flow of the image during transfer, which conventionally occurred. , it was possible to obtain a high-quality transferred image using a liquid developer.

"Example" Next, an example will be described, but the effects of the present invention are not limited thereto.

Example-l Polycarbonate (trade name “Lexan lλl” G, E
(manufactured by Co., Ltd.) ioys diarylamine compound 61 shown below, steryl dye 60 shown below as a sensitizer
~ was dissolved in 10 g of methylene chloride.

This solution was then coated with a wire bar onto a 100 micron thick polyethylene terephthalate film with a notradium deposited layer, dried to remove the coating solvent and form a 4 micron thick photoconductive layer. and an electrophotographic photoreceptor was manufactured.

(Diarylamine compound) (Styryl dye) On the other hand, a liquid developer having fibers in toner particles was prepared in a manner similar to Example t of JP-A/-/10JlAr as follows.

The components having the following composition were mixed in a kneader and kneaded at 0C for 2 hours to obtain a mixture. This mixture was cooled in a kneader and then ground in the same kneader. 1 part by weight of this pulverized material and ≠ parts by weight of Isopar H were dispersed in an Indian shaker for 6 hours to obtain a dispersion.

This dispersion was diluted with Aituno ξ-G so that the solid content of the toner was 1/1 Dip, and at the same time basic barium itronate was added as a charge control agent to impart negative chargeability to 1/1/1 Dip.
A liquid developer was prepared by pressurizing the liquid developer.

(Composition for crosstalk) The surface of the previously prepared electrophotographic photoreceptor is charged to 1000μ, image exposure is applied through a positive original document to create an electrostatic latent image, and immediately after development with the liquid developer described above, The sample was rinsed with Isopar H or Isopar G (manufactured by Ekun Corporation), which is a nonpolar aliphatic hydrocarbon used in the carrier liquid, and then left indoors (270 cm, 16%) to air dry. The relationship between the drying time of the transmitted image density/j and the amount of carrier liquid remaining on the electrophotographic photoreceptor is shown in Figure 177 when the rinsing liquid is iso and e-H.
The case shown in FIG. 2 is shown in FIG. Here, the vertical axis indicates the value of the amount of remaining liquid converted to the weight of toner in the image area.

After leaving it for a certain period of time to reduce the amount of rinsing liquid by air drying, it was precharged at 16 KV using a corona charger.

Next, attach the image surface of the electrophotographic photoreceptor to Fuji Photo Film
It was stacked on an aluminum substrate used in the S version FPD-If and transferred by applying a negative corona discharge from the electrophotographic photoreceptor side. Table 1%2 shows the results regarding the drying time after rinsing, toner scattering on the photoreceptor due to precharging, transferred image quality, and transfer efficiency when Isopar G was used as the rinsing liquid.

From the results in Table 11 and Table 2, the amount of remaining liquid that does not cause toner scattering due to precharging or uneven transfer is between 2 and 20 instant/1119 (toner weight) for both Isopar H and G. I understand. 3 and 3 show enlarged views (photographs) of the state of toner scattering on the photoreceptor when precharging is applied.

Fig. 3 shows the precharge for io seconds after rinsing the table -/, and Fig. 3 shows the precharge for io seconds after rinsing.

The halftone dots in the enlarged image are /30 lines/inch, sb, and the area ratio is io.
%. Further, the magnification factor is 7r times.

For comparison, the transfer efficiency was extremely low (30% or less) when the transfer was performed without precharging.

Next, the transfer material obtained in Table 7 was heated for /JO0C-1 minute, and then subjected to surface treatment by gumming, and a printing test was conducted (Davidson ROO printing machine).

As a result, while the samples with a short drying time after rinsing (10 seconds, 1 minute) caused a slight amount of background smudge, the samples made after Hiroba had almost no background smudge.

In addition, as a result of the same printing test with the transfer without rinsing, the results showed that the drying time was short (10 seconds, 1
(min.), the degree of background staining was greater than that of the rinsed one.

From the above results, it was found that the transfer method of the present invention has excellent transfer image quality and transfer efficiency, and causes less scumming when used as a printing plate.

Example 2 In Example 1 VC, a test was conducted by changing the drying after rinsing from natural drying to cold air from a dryer (room temperature). As a result, when the residual liquid amount was 2 to 20'I9/η (toner weight), transfer could be performed without toner scattering or transfer unevenness caused by precharging.

Example-3 In Example-C, drying was carried out using hot air (so 0c on the photoreceptor) instead of cold air from a dryer. It showed good transferability.

In Examples - Ko Examples -/, transfer was carried out as follows. After development, rinsing and drying, the sensitive material was brought into contact with the same aluminum plate used in Example 7, and a direct current of 2001 was applied to the aluminum plate for transfer. The same results as Example 7 were obtained in terms of transfer efficiency and transferred image.

Example-j- was tested in exactly the same manner as in Example-7 except that the ethylene/methacrylic acid copolymer used as the pigment coating agent was replaced with another ethylene copolymer.

As a result, the residual liquid amount on the photosensitive material was 2 to 20 η/cm (the toner in the toner weight showed good transferability as in Example-7).

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the relationship between the drying time after development and rinsing and the amount of liquid remaining on the photoreceptor in Example -/. Fig. 1 shows the case where the rinsing liquid is Iso and tH, and Fig. 2 shows the case where the rinsing liquid is Isono G. FIGS. 3 and 3 are enlarged views (photographs) showing the state of scattering of toner particles on the photoreceptor when precharging is applied after rinsing with Isopar H in Example-1. Figure 3 shows IO seconds after rinsing, and Figure 3 shows the precharge after rinsing. The magnification is 7r times. Patent applicant Fuji Photo Film Co., Ltd. Figure 3 Figure 41

Claims (3)

[Claims] (1) A developing step in which an electrostatic latent image formed on an electrophotographic photoreceptor having a photoconductive layer provided on a conductive support is developed with an electrophotographic liquid developer containing at least toner particles and a carrier liquid; In the wet electrophotographic transfer method, which consists of a pre-charge step using a corona discharge of the same polarity as the toner particles on the body, and a transfer step in which the image formed on the photoreceptor is transferred to a transfer material, the photoreceptor is removed between the development step and the pre-charge step. A drying step is provided to reduce the amount of the carrier liquid of the developer on the photoreceptor so that the carrier liquid of the developer on the photoconductor is reduced to 2 to 20% per 1 mg of solid content of toner particles.
A wet electrophotographic transfer method characterized in that mg. (2) The wet electrophotographic transfer method according to claim 1, wherein the liquid developer contains an ethylene copolymer as a toner particle component. (3) The wet electrophotographic transfer method according to claim 1, wherein the transfer material is an aluminum plate.