JPH11160917A - Image forming method - Google Patents

Abstract

(57) [Problem] To provide a good image forming method for preventing a fimming phenomenon, a background stain, and a negative afterimage. SOLUTION: In a process of developing an electrostatic latent image by a liquid developer applied on a belt or a roller member using a liquid developer having at least a colorant and a binder in a dispersion medium, an average of the developer is averaged. The content of particles having a particle size of 0.20 μm or less is 30% or less, and the average particle size of the toner is 0.1%.
An image forming method characterized by having a thickness of 3 to 10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used in an electrophotographic copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art Electrophotographic developers are broadly classified into dry developers and wet developers (liquid developers). Liquid developers have the advantage that a clear image can be obtained because of their small toner particle size. In recent years, its use value has been reviewed.

In general, an electrophotographic liquid developer includes a colorant comprising carbon black, an organic pigment or a dye, an acrylic resin, a phenol-modified, an alkyd resin, a rosin,
A toner containing a binder made of a synthetic or natural resin such as synthetic rubber as a main component and a charge control agent such as lecithin, metal soap, linseed oil, and higher fatty acid added to a high-density resin such as petroleum-based aliphatic hydrocarbon. It is dispersed in a carrier liquid mainly composed of a solvent having an insulating property and a low dielectric constant.

In electrophotography using a liquid developer, a liquid developer (solid content of about 1% or less) is prepared by dispersing a liquid toner (solid content: 5 to 90%) in a highly insulating dispersion medium.
Develops the electrostatic latent image on the photoreceptor. In the copier, a liquid toner and a dispersion medium bottle are set, and a liquid toner (wet toner) and a dispersion medium consumed by making a copy are automatically detected, and a system for replenishing each is provided.

In a copying machine, after developing an electrostatic latent image on a photoreceptor with a liquid developer, excess liquid developer is removed from the photoreceptor. Generally, after removing excess liquid developer by a squeeze roller (reversely rotating without contacting the photoreceptor) or corona discharge, the toner is transferred to a transfer paper to obtain a copy after fixing.

[0006] In this case, if the viscosity of the liquid developer is increased, the liquid developer tends to be insufficiently removed by the squeeze roller, and the adhesion of the liquid developer to the photoconductor increases.
The image becomes a blurred blurred image. On the other hand, if the viscosity of the liquid developer is low, the removal of the liquid developer by the squeeze roller is large and the amount of the liquid developer adhered becomes too small, so that the toner is hardly transferred to the transfer paper, and the image density and solid uniformity are reduced. Would.

The toner developed on the photoreceptor is subsequently transferred onto a transfer material such as plain paper. Generally, the transfer rate of the toner depends on the properties of the transfer material, for example, smoothness, oil absorption, paper thickness, and the like. It is in the range of 50-100%. Especially in so-called lacquer paper having low smoothness, 50% of the toner remains on the photoreceptor,
It needs to be cleaned with a cleaning blade or the like. In this case, if toner that cannot be completely cleaned by the cleaning blade remains on the photoreceptor, charging, exposure and development are repeatedly performed thereon, and the toner is filmed on the photoreceptor, resulting in image contamination. cause. In the process using the intermediate transfer member, filming of the toner remaining on the intermediate transfer has been a problem.

Such a filming phenomenon has recently emerged as a major problem when it is used as a color toner, mainly a cyan toner. However, there are still few approaches to solving the filming phenomenon in the color of the liquid developer.

For example, Japanese Patent Application Laid-Open No. 60-179750 proposes a toner containing an acid amide compound. However, a conventional developing method using such a toner cannot maintain high image quality. About 600-1500
The filming phenomenon was confirmed when the sheets were continuously copied. Japanese Patent Application Laid-Open No. 49-71943 discloses that a developer using a higher alkylamine or a quaternary ammonium salt compound as a charge control agent enhances gradation reproducibility. However, the gradation of this liquid developer deteriorates over time or when the liquid toner (concentrated toner) is stored for a long period of time. Also, JP-A-51-24244, JP-A-58-52
No. 652 and the like, the liquid toner to which a higher alcohol is added has the same tendency.

Also, in the process of developing an electrostatic latent image on a photoconductor with a developer by a toner applied or electrodeposited on a belt or roller member as in the process of the present invention, similarly to the filming phenomenon, Problems such as background soiling and negative afterimages have been found. Also, Japanese Patent Laid-Open No. 9-1
As described in JP-A-83859 and JP-A-179354, there is a method for producing a toner having a narrow particle size distribution, but there is a problem in transferability, which is not practical.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming method which can prevent a filming phenomenon, a background stain and a negative afterimage.

[0012]

The present inventors have intensively studied and studied the mechanism of occurrence of the filming phenomenon in order to solve the above problems and obtain stable image quality. As a result, the liquid developer does not contribute to the development of the electrostatic latent image by uniformly developing all the constituent materials of the toner by repeatedly developing, but instead of the fine particles of the toner such as resin, dispersant, and pigment. Was gradually accumulated in the dispersion medium, and the transfer characteristics became poor. As a result, it was found that toner filming occurred, and the image density and solid uniformity became poor.

That is, the present invention comprises the following items. (1) In a process of developing an electrostatic latent image using a liquid developer having at least a colorant and a binder in a dispersion medium with the liquid developer applied on a belt or a roller member, average particles of the developer are used. The content of the particles having a diameter of 0.20 μm or less is 30% or less, and the average particle diameter of the toner is 0.3 to 10%.
μm.

(2) The developer has a viscosity of 50 at 25 ° C.
The image forming method according to the above (1), wherein the image forming pressure is from 1 to 10,000 centistokes. (3) The image forming method according to (1), wherein the colorant is a pigment, and the pigment is dispersed in a dispersion medium together with a resin that is hardly soluble or insoluble at room temperature. (4) The dispersion medium is any one of fatty acid ester, fluorine oil, isoparaffin normal paraffin, silicone oil, silicone resin, wax, and liquid paraffin
The image forming method according to any one of the above (1) to (3), wherein the image forming method comprises one or more kinds.

(5) The image forming method as described in (1) above, wherein the liquid developer is obtained by dispersing a pigment and a resin by heating and melting them in a dispersion medium. (6) The process for developing an electrostatic latent image is a method of forming a toner layer on a roller or a belt, performing a corona discharge on the toner layer, and then developing the electrostatic latent image. The image forming method according to (1). (7) The image forming method according to (1) or (6), wherein the electrostatic latent image is developed after attaching a pre-wet liquid.

(8) The method according to (1), (6) or (7), wherein after the electrostatic latent image is developed, the toner image is transferred to the intermediate transfer member, and then an image is formed on a transfer member. Image forming method. (9) The photoconductor according to (1), (6), (7) or (8), wherein the surface of the photoconductor forming the electrostatic latent image has water repellency and oil repellency (θ = 30 ° or more). )).

In the process of developing an electrostatic latent image on a photoconductor with a toner coated or electrodeposited on a belt or a roller member as in the developing process of the present invention, the viscosity of the developer is related to the particle diameter in addition to the particle size. It is newly found that it is. That is, the average particle size of the toner of the present invention is 0.2 μm
The following content is 30% or less, the average particle diameter of the toner is 0.3 to 10 μm, and the viscosity of the developer of the liquid toner is within 50 to 10,000 centistokes. It was also found that negative afterimages were hardly generated.

When the content of 0.2 μm or less is 30% or more and the viscosity of the developer is 50 cst or less, the image density is low, and filming, negative afterimage, and background smear tend to occur.
When the average particle size is 10 μm and the viscosity is 10000 cst or more, filming, background staining, and negative image sticking hardly occur, but the resolution, gradation, and solid uniformity are poor. The preferred particle size is 0.
The viscosity of the 5 to 5 μm developer is 1 at 25 ° C. using a B-type viscometer.
00-5000 cst is suitable for this process. Next, the image forming process of the present invention will be described with reference to the drawings.

In FIG. 1, a photoconductor L, for example, an organic semiconductor, selenium, amorphous silicone, or another inorganic photoconductor rotating in the direction of the arrow is charged by corona charging E while rotating. When pre-wetting the carrier liquid, the F roller applies the insulating liquid with the F roller. Do not apply if prewetting is not required.

G is a writing exposure unit. K is a toner developing roller and can be applied by an electrodeposition method in which the toner is uniformly applied to the developing roller K from the toner container I by the toner roller J. A voltage is applied to the toner layer on the developing roller by the corona discharge unit H or not, and then the latent image on the photoconductor L is developed by the developing roller K and visualized. Each roller may be made of rubber, metal, plastics, or the like, and may be made of a material having a smooth surface, a rough surface, a sponge shape, an elasticity, or a material having low surface energy.

The transfer material B transfers the toner image on the photoconductor L onto the transfer material B by the transfer roller A. A good image can be formed on the transfer material by a transfer method such as pressure, corona discharge, heating, or a combination of heating and pressure, corona and pressure, or a combination of corona and heating. Further, in order to clean the surface of the photoconductor, the remaining toner is removed by a cleaning roller C and a cleaning blade D, and the next copy is performed.

FIG. 2 differs from FIG. 1 in that it includes a step F of coating the pre-wet liquid with a felt F from a roller. The pre-wet liquid is applied with felt as needed, but need not always be applied. The toner is applied to the developing roller K from the toner container I through the rollers J ₁ and J ₂ , and a DC voltage is applied to the applied toner layer from the corona discharge unit H. It may not be applied, FIG.
The developing roller K has a longer contact width with the photoconductor L than in FIG. 1, and is designed so that the latent image can be sufficiently developed with toner.

The toner image developed on the photoconductor is transferred to a transfer member B by a corona discharge section A to form an image. If necessary, the toner image is further fixed on the transfer member in the drying section.

FIG. 3 shows an example of a developing process for outputting a color copy. Yellow, magenta, cyan and black toner containers I and J on photoconductor
The latent image on the photoreceptor L is developed for each color, transferred to the intermediate transfer member M, and then transferred to the transfer member B by the transfer roller A using pressure, corona, heat, a combination of pressure and heat, and color copy. Create FIG. 4 shows an image forming process for color copying.

As in FIG. 3, yellow, magenta, cyan,
The latent image on the photoconductor L is developed by the belt N for applying the toner layer to the toner containers J and I for storing the black toner, and the toner image is transferred to the transfer member B. For the belt N for applying the toner layer, a cleaning roller O and a cleaning blade P are used for cleaning C and the belt is reused. Belt N is PET, EVA, V
CL, rubber, metal belt and the like. The belt can be used by changing its elasticity, surface roughness, surface energy and the like.

The surface of the photoconductor L is coated with a fluororesin, a silicone resin, a water-soluble resin, or the like to a thickness of 1 to 10 μm to increase water repellency and oil repellency, and to improve transfer rate, background contamination, and cleaning properties. it can. The configuration of the electrophotographic liquid developer according to the invention is such that a colorant, a binder, a charge control agent, and the like are dispersed in a dispersion medium (a non-polar, highly insulating liquid).

The dispersing medium may be any non-polar, highly insulating liquid. In particular, hexane, octane, isooctane, decane, and isoparaffin-based solvents such as Isopar E and Isopar G from Exxon are used. One or two of Isopar L, Isopar M, Isopar V, silicone oil, fatty acid ester, Isopar H, Shell Solsell 71, fluorine oil, iso-paraffin, n-paraffin, waxes, liquid paraffin The above is excellent.

These dispersion media are also used as a dispersion medium (carrier liquid) of a liquid toner.

The colorant plays a role of visualization,
There are many inorganic and / or organic pigments and dyes, including carbon black, ultramarine, navy blue, phthalocyanine pigments,
Azine-based pigments, triphenylmethane-based pigments, azo-based pigments, condensation-based pigments, and the like are used.

In particular, the use of a colorant whose pigment surface is coated with a dispersion medium, ie, a resin insoluble in a carrier liquid (non-polar insulating liquid), is effective in preventing the filming phenomenon. This is because covering the pigment surface with a resin insoluble in the carrier liquid makes it difficult for the pigment to dissolve in the dispersion medium during dispersion.

Specifically, for example, 30 parts by weight of phthalocyanine blue and 80 parts by weight of a styrene / vinyltoluene / vinylpyrrolidone (40/3/5) copolymer are kneaded in a kneader at 140 ° C., and then heated at 150 ° C. Kneading with a roller for 2 hours, pulverizing to make a colorant (pigment), followed by styrene-vinyltoluene-vinylpyrrolidone copolymer,
The pigment surface is coated with a polymer insoluble in a dispersion medium such as an acrylic resin, an ethylene-acrylic acid copolymer, or an ethylene-methyl methacrylate-fumaric acid copolymer. According to the use of such a pigment whose surface is coated with a resin insoluble in a dispersion medium, a fine particle toner having a particle diameter of 0.1 μm or less is not easily generated.

In a general pigment used in the production of an electrophotographic toner, since a dispersant such as rosin and wax is contained in the pigment body, the dispersant such as wax dissolves in a dispersion medium when the pigment is dispersed. However, at the time of development, the dispersant from the pigment may elute and a filming phenomenon may occur. Therefore, by using a pigment to which a dispersant is not added, the pigment is less likely to be dissolved in a dispersion medium, which is effective in preventing a filming phenomenon.

The binder is a resin or polymer that plays a role of fixing. Specifically, vinyl acetate, a polymerized polymer of a vinyl ester represented by vinyl propionate and the like, a polymerized polymer of acrylic acid and methacrylic acid ester,
Furthermore, synthetic resin rubber represented by styrene-butadiene system, and natural rubber, and modified natural rubber, rosin and rosin modified resin, epoxy resin, silicone resin, styrene resin, coumarone indene resin, and cyclopentadiene polymerized polymer Petroleum resin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate-acrylic acid copolymer, polyethylene wax, etc. are used.

The charge controlling agent plays a role of stably maintaining the polarity of the toner, and includes inorganic and organic pigments, organic dyes, resins having a polar group in the molecule and aromatic carboxylic acids, alcohols, ketones, esters, ethers and the like. An amine or the like is used, and a polymer containing the same is also used for this purpose. In addition, various kinds of metal soaps such as cobalt naphthenate and manganese octoate may be used as needed.

The above-mentioned four components are not clearly classified. For example, dyes and pigments may play a role of coloring as well as a role of charge control, and a resin or polymer having a polar group may play a role of fixing. At the same time, it may play a role of charge control.

In the liquid developer of the present invention, a dispersant is added to the liquid toner in order to disperse the liquid toner in the carrier liquid. Dispersing agents include Sunwax E200, E
Polyethylene resins such as 250P and 131-P (manufactured by Sanyo Chemical Industries), polypropylene resins such as Viscol 500P and 600P (manufactured by Sanyo Chemical Industries), Denka Vinyl SS
-100, SS-130, DSS-130 (manufactured by Denki Kagaku Kogyo Co., Ltd.), etc., paraffin wax, natural wax, surfactant and the like. These may be added to the colorant or alone, but it is better not to add them to the colorant. The following two representative methods are used to separate toner particles (fine particle toner) having a particle size of 0.2 μm or less.

A. Method Performed after Dispersion of Toner (1) Centrifugation Method The liquid toner is centrifuged to separate fine particle toner. Specifically, it is 30-
Centrifuge for 60 minutes to separate the upper particulate toner.

(2) Filtration Method The liquid toner is filtered through a filter to separate the filtrate. Specifically, there is separation by a filter cloth, filter paper, or various filters. (3) Electrodeposition The liquid toner is filtered through a filter to separate the filtrate.

Specifically, a liquid toner is filled and a DC voltage of 1 to 10 kV is applied between the electrode plates. In the case of (+) toner, the toner adhering to the cathode plate is collected. In the case of (-) toner, on the contrary, the toner attached to the anode plate is collected. Thus, a toner having a solid content of 15 to 95% by weight is obtained. By this electrodeposition method, it is possible to remove fine particle toner having a slow electrode migration speed of 0.2 μm or less.

B. Method before dispersion of toner (1) Synthetic method In liquid polymerized toner, it is difficult to produce a fine particle toner having a particle diameter of 0.2 μm or less by adjusting the amount of a dispersant added or changing the formulation of a monomer and a pigment. Synthesized from

(2) Purification Method A liquid toner is produced by purifying a resin or a pigment of a liquid toner, removing a low molecular weight polymer or a pigment, and previously removing a pigment component dissolved in a dispersant. As a result, a fine particle toner having a particle size of 0.2 μm or less
% By weight, preferably 10% by weight or less. Further, in spite of the advantage that an image having a high solid content can be formed at a high solid content concentration, conventionally, in order to prevent the filming phenomenon, it is conventionally 3.0% by weight, preferably 1.0% by weight. The following liquid toners have been frequently used.

However, since the filming phenomenon hardly occurs in the liquid developer according to the present invention, 5 to 100% by weight of a high solid content liquid toner, which cannot be considered in the conventional image forming method, is directly used as the liquid developer. An image forming method in which the filming phenomenon hardly occurs even when used was found.

For example, a water-repellent / oil-repellent layer composed of a thin film layer of a silicone resin or a fluororesin is provided on a selenium drum, charged and exposed, and an electrostatic latent image is developed with a liquid developer containing a high solid content liquid toner. Is also possible. It is also possible to develop the electrostatic latent image with the high solid content toner of the present invention after prewetting with a highly insulating liquid.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described specifically with reference to examples. These examples only show a part of the present invention, and the contents of the invention are not limited by the examples. Comparative Example 1 (Production of liquid toner) Carbon black # 44 (manufactured by Mitsubishi Carbon Corporation) 10 parts by weight Ethylene-vinyl acetate copolymer 80 parts by weight Isopar H 300 parts by weight These were taken in an attritor and dispersed at 30 ° C. for 2 hours. Thus, a liquid toner A was manufactured. Comparative Example 2 In Comparative Example 1, a toner A ′ was prepared with 800 parts by weight of Isopar H.

Example 1 A toner was dispersed in a centrifuge at 3000 rpm for 15 minutes to obtain a liquid toner B.

Example 2 A liquid toner C was obtained by removing the fine particle toner from the toner A using a filter having a diameter of 0.2 μm over 24 hours. Example 3 A toner was separated by the following electrodeposition method to obtain a liquid toner D.

A DC voltage of (+) 6 kV was applied to the electrode plate, and the toner was separated from the electrode plate while performing electrodeposition for 60 seconds. Using the liquid toner image forming process shown in FIG. 1, the filming, the image density, the gradation, the bleeding, the resolution, and the presence or absence of a negative afterimage were evaluated.

(1) The particle size of the liquid toner is measured by a particle size distribution analyzer using a centrifugal sedimentation method. (2) Viscosity measurement of toner with a day viscometer at 250 ° C. (cst) (3) The number of sheets where the filming phenomenon occurred was recorded. (4) Image density was measured with a Macbeth densitometer. (5) The gradation was evaluated on a scale of 10 on a gray scale. (6) Image bleeding was visually evaluated in 1 to 5 steps.

Rank 5 was blurred, 4 was slight, 3 was no problem in use, and 2 and 1 were problems in use. (7) The resolution was evaluated using the Takenoko Chart of the Electrophotographic Society of Japan. Below 5.3, there is a problem in use. Table 1 shows the results.

[0050]

[Table 1]

Example 4 Copper phthalocyanine blue 50 parts by weight Lauryl methacrylate 120 parts by weight Styrene 50 parts by weight Methacrylic acid 10 parts by weight BPO 5 parts by weight Dispersant (polyethylene wax 250P) 155 parts by weight A mixture consisting of 155 parts by weight was dispersed in a ball mill for 24 hours. did.

This dispersion was treated with silicone oil KF58.
Polymerized liquid toner E was obtained by dropwise polymerization in a flask containing 300 parts by weight and 100 parts by weight of isopropyl myristate over 2 hours. The polymerization temperature was 80 ° C. for 6 hours.

Example 5 Copper phthalocyanine blue (containing a dispersant) 10 parts by weight Ethylene maleic anhydride copolymer 40 parts by weight Styrene / butadiene resin 20 parts by weight Isopar V 100 parts by weight A mixture composed of 100 parts by weight was dispersed with a Keddy mill for 2 hours, and the liquid was dispersed. Toner F was obtained.

Example 6 Liquid toner F was heated to 70 ° C., dispersed by a Keddy mill for 2 hours, and cooled to obtain toner G. Example 7 Using the liquid toner F, an image was formed after pre-wetting of Isopar V with the pre-wet roller F of FIG.

Example 8 Copper phthalocyanine blue of liquid toner F was converted to Isopar M
Toner kneaded in advance with an ethylene / vinyl acetate resin insoluble in water
I got Then, a copy was obtained by the image forming process of FIG.

Example 9 A copy was made by an image forming process having an intermediate transfer member shown in FIG. 3 using silicone oil KF96-1000 cst instead of Isopar V of liquid toner F. Example 10 Using the toner of the liquid toner F, an image was formed on the surface of the toner layer after a positive charge of 1 kV was precharged in the image forming process of FIG.

Example 11 A photoreceptor having a contact angle of 59 ° was prepared by subjecting the surface of the photoreceptor shown in FIG. 1 to a water / oil repellent treatment with a silicone resin. Using this image forming process, a copy was obtained with the liquid toner F. Table 2 summarizes the evaluation results.

[0058]

[Table 2]

When the liquid toner of the present invention was used, the viscosity of the toner was within 50 to 10,000 cst, and the content of the fine particle toner having a particle size of 0.2 μm or less was 30% or less. Therefore, as can be seen from Examples 1 to 11, filming was performed continuously for 1000 times.
It can be seen that the image density, gradation, image bleeding, image resolution, resolution are high, and no negative image sticking occurs even when the sheet is copied. In Comparative Examples 1 and 2, 30% or more of fine particles having a particle size of 0.2 μm or less, and in Comparative Example 2, the viscosity was 50 cst or less.
Bleeding etc. are decreasing.

[0060]

As can be seen from the comparison between Examples 1 to 11 and Comparative Examples 1 and 2, according to the present invention, the toner has an average particle diameter of 0.3 to 10 μm, 0.2μ
m is 30 wt% or less, and the viscosity is 50-1.
Use of the 0000 cst developer has an effect of preventing filming and negative afterimage. Claim 3
Also in Examples 1 to 11, as shown in Examples 1 to 11, there is no occurrence of filming and negative image lag, and an effect of improving image density, gradation, resolution, and blurred image quality is recognized.

[Brief description of the drawings]

FIG. 1 shows an example of an image forming process to which the present invention is applied.

FIG. 2 shows another example of an image forming process to which the present invention is applied.

FIG. 3 shows another example of the image forming process to which the present invention is applied.

FIG. 4 shows another example of an image forming process to which the present invention is applied.

Claims (9)

[Claims] In a process of developing an electrostatic latent image with a liquid developer applied on a belt or a roller member using a liquid developer having at least a colorant and a binder in a dispersion medium, The content having an average particle size of 0.20 μm or less is 30% or less, and the average particle size of the toner is 0.1% or less.
An image forming method having a thickness of 3 to 10 μm. 2. A developer having a viscosity of 50 to 1 at 25 ° C.
2. The image forming method according to claim 1, wherein the density is 0000 centistokes. 3. The image forming method according to claim 1, wherein the colorant is a pigment, and the pigment is dispersed in a dispersion medium together with a resin that is hardly soluble or insoluble at room temperature. 4. The dispersion medium according to claim 1, wherein the dispersion medium comprises one or more of fatty acid ester, fluorine oil, isoparaffin, normal paraffin, silicone oil, silicone resin, wax, and liquid paraffin. 3. The image forming method according to any one of 3. 5. The image forming method according to claim 1, wherein the liquid developer is obtained by dispersing a pigment and a resin by heating and melting the dispersion in a dispersion medium. 6. A method for developing an electrostatic latent image, comprising: forming a toner layer on a roller or a belt; performing corona discharge on the toner layer; and developing the electrostatic latent image. 2. The image forming method according to claim 1, wherein: 7. The image forming method according to claim 1, wherein a pre-wet liquid is attached to the electrostatic latent image and then developed. 8. The image according to claim 1, wherein an image is formed on a transfer member after the electrostatic latent image is developed, and after the toner image is transferred to the intermediate transfer member. Forming method. 9. The photoconductor on which an electrostatic latent image is formed has water and oil repellency (θ = 30 ° or more). Item 10. The image forming method according to Item 8.