JPH0350562A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain a high-quality image without inner side void in transfer by using toner in which substance whose contact angle with water forms a specified smooth surface is contained for the surface layer of an electrostatic latent image holding body and using a transfer device which is made to abut with specified linear pressure. CONSTITUTION:The developer containing 0.01-0.1 pts. wt. substance whose contact angle with water forms the >=80 deg. smooth surface is used for the surface layer of the electrostatic latent image holding body 1 so as to develop an electrostatic charge image on the image holding body 1, then the developed image is electrostatically transferred through the transfer device 2. Abutting pressure used at such a time is set >=3g/cm as the linear pressure. Then, silicone oil, etc., is used as a coating substance and it moves to the image holding body 1 with the developer, so that the coating substance which remains without being transferred forms a water flexible coating film on the image holding body 1 with the mechanical action at a cleaning stage. Thus, the inner side void in transfer is not caused and the high-quality image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming method in which a transfer device of an electrophotographic apparatus is brought into contact with an electrostatic latent image carrier to transfer a developed image.

[Prior Art] In an image forming apparatus that includes a step of electrostatically transferring a transferable toner image formed on the surface of a latent image carrier to a sheet-like transfer material mainly made of paper, a rotating cylindrical, endless An endlessly running image carrier such as a belt is used, a transfer device to which a bias is applied is pressed against it, a transfer material is passed between the two, and the toner image on the image carrier side is transferred to the transfer material. A device having such a structure has already been proposed, for example, as disclosed in Japanese Unexamined Patent Publication No. 59-46664.

Compared to transfer means that utilize corona discharge, which has been widely used in the past, such a device adjusts the pressure force of the transfer roller against the image carrier to increase the adsorption area of the transfer material to the image carrier. can be enlarged, and the transfer material can be actively pressed and supported at the transfer site. Therefore, there is less risk of synchronization caused by the transfer material conveyance means or transfer misalignment due to loops or curls existing in the transfer material. It is easy to respond to requests such as reducing the diameter of the carrier.

However, on the other hand, in a device that performs transfer by contact, a certain amount of pressure must be applied to the transfer device because the transfer current is supplied from the contact portion. When contact pressure is applied, pressure is also applied to the toner image on the latent image carrier, causing aggregation. Furthermore, when the surface of the latent image carrier is made of resin, adhesion also occurs between the toner aggregates and the latent image carrier, inhibiting transfer to the transfer material, and in extreme cases, adhesion may occur. A phenomenon occurs in which strong parts are not transferred at all, resulting in image loss.

This phenomenon becomes particularly noticeable in the line portion of 0.1 to 2 mm. This is due to etch development in the line area, where a lot of toner is deposited and agglomeration is likely to occur due to pressure.
This is due to the fact that transcriptional defects are likely to occur. At this time, the output image is a copy with an image formed only on the outline, which is called a "transfer void." FIG. 1 shows an example of voids in the transfer. In the figure, a is an image transferred by corona transfer, and b is a hollow image transferred by a transfer roller.

"Transfer voids" are particularly noticeable when using thick paper of 100 g/am'' or more, OHP films with high smoothness, and when copying the second side.

In the case of thick paper, film, etc., the transfer material is thick, so the effect of the transfer electric field is small, and the pressure is strong, making it easier for the material to be hollowed out.

In addition, when copying the second side, when the transfer material passes through the fixing device during image formation on the first side, the release agent contained in the fixing device adheres to the transfer material to prevent offset, and when transferring the image on the second side, the toner It is thought that this prevents the adhesive from adhering to the transfer material, making hollowing out more likely.

From the above, in the case of a transfer device using a contact member, although there are many advantages such as miniaturization and low power consumption, the conditions for the transfer material are narrower. [Problems to be Solved by the Invention] An object of the present invention is to provide an image forming method that solves the above-mentioned problems.

An object of the present invention is to provide an image forming method using pressure transfer such as a contact transfer method, which has a transfer step that allows a high-quality image that is faithful to a latent image to be obtained regardless of the conditions of the transfer material. Our goal is to provide the following.

An object of the present invention is to provide an image forming method in which there is no phenomenon such as "transfer voids" or the like, or in which the phenomenon is suppressed.

An object of the present invention is to provide an image forming method using a developer that provides high quality images without transfer defects even when using various transfer materials such as thick transfer paper.

A further object of the present invention is to provide an image forming method using a developer that is stable against environmental changes such as high temperature and high temperature, low temperature and low humidity, and can always exhibit good characteristics.

[Means and effects for solving the problem] The present inventors
By containing in the toner a substance that forms a slippery surface with a contact angle of 80° or more with water on the surface layer of the electrostatic latent image holder, a transfer device that is brought into contact with water at a contact angle of 3 g/cm or more can be used. It has been found that satisfactory results can be obtained in the transfer process.

That is, the present invention provides an image forming method including a step of developing an electrostatic image on an electrostatic image carrier with a developer and electrostatically transferring the developed image to a transfer material via a transfer device, The charge image carrier and the transfer device have a linear pressure of 3 g/cI.
(1) The surface layer of the electrostatic latent image holder has a contact angle with water of 80
The substance that forms a slippery surface of 0. 01~1.0
This image forming method is characterized in that it uses a developer containing parts by weight.

The contact pressure used in the present invention is 3 g/linear pressure.
cm or more, particularly preferably 20 g/
cm.

Line pressure is calculated using the following formula.

(Linear pressure) [g/cml = (total pressure applied to the transfer member)
[g] ÷ (Length of contact) [cml If the contact pressure is less than 3 g, it is undesirable because conveyance shake of the transfer member and transfer failure due to insufficient transfer current occur.

Examples of the transfer device used in the present invention include a transfer roller as shown in FIG. 2 or a transfer belt as shown in FIG.

FIG. 2 is a schematic side view of the main parts of a typical image forming apparatus of this type, and the illustrated apparatus has a cylindrical image carrier ( A photoreceptor (hereinafter referred to as a photoreceptor) 1 is provided with a conductive transfer roller 2 in contact with the photoreceptor.

A primary charger is installed around the photoconductor 1 to uniformly charge its surface, and a light image such as image-modulated laser light or reflected light from a document is projected onto the charged surface to charge the surface of the photoconductor 1. an exposure section that attenuates the potential of and forms an electrostatic latent image;
It goes without saying that a cleaner for removing residual toner remaining on the surface of the photoreceptor even after transfer and other members necessary for image formation are provided, but these are all omitted.

The transfer roller 2 consists of a core metal 2a and a conductive elastic layer 2b, and the conductive elastic layer 2b is made of a volume resistive material such as urethane or EPDM in which a conductive material such as carbon is dispersed.
It should be made of an elastic material comparable to that of a can. A bias is applied to the core metal 2a by a constant voltage power supply 8.

FIG. 3 shows the present invention applied to a transfer belt. The transfer belt 9 is supported and driven by a conductive roller IO.

The transfer device is normally pressurized by applying pressure to the end bearing of the core metal 2a or lO.

The present invention is particularly effective for image forming apparatuses in which the surface of the latent image carrier is made of an organic compound. When an organic compound forms the surface layer, it has good adhesion with the binder resin contained in the toner, and especially when the same material is used, a chemical bond occurs at the contact point, resulting in poor transferability. This is because it decreases.

The surface material of the latent image carrier used in the present invention includes silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate,
Examples include styrene, polyethylene terephthalate, polycarbonate, etc., but are not limited to these, and other monomers or copolymerizations, blends, etc. of exemplified resins can also be used.

The present invention is particularly effective for image forming apparatuses in which the diameter of the latent image carrier 1 is 50 or less. This is because in the case of a small diameter drum, even if the linear pressure is the same, the curvature is large, so pressure concentration tends to occur at the contact area.

It is thought that the same phenomenon occurs with belt photoreceptors, and it is also effective for image forming apparatuses in which the radius of curvature at the transfer section is 25 mm or less.

Next, the toner used in the present invention will be described.

The film-forming substance used in the present invention includes silicone oils represented by the following formula (for example, dimethyl silicone oil, alkyl-modified silicone oil, α
- Examples include methylstyrene-modified silicone oil, chlorphenyl silicone oil, and fluorine-modified silicone oil.

Further, fatty acid metal soaps 01 (R-C-0) M represented by the following formula include, for example, zinc stearate, zinc laurate, zinc myristate, calcium stearate, aluminum stearate, and the like.

Although examples of film-forming substances have been given above, the present invention is not limited to these.

The contact angle of the surface of the electrostatic image carrier with water is measured as follows. Using a Kyowa contact angle meter CA-DS, mount the sample so that the surface is horizontal when viewed through a straight mirror.

10 pg of pure water subjected to ion-exchange treatment is dropped onto the surface, and 1/2θ is measured using a straight mirror. From this, the contact angle θ is determined. Film formation is thought to be mainly carried out during the cleaning process. It will be done.

In other words, the electrostatic charge moves along with the developer onto the image carrier,
The film material remaining without being transferred is broken or stretched by mechanical action in the cleaning process, thereby forming a water-repellent film on the holder.

The amount of film substance added is 0 to 100 parts by weight of toner.
．． The amount is preferably 01 to 1.0 parts by weight.

If the amount is less than 0.01 part by weight, no effect of the addition will be observed and problems regarding transfer will occur. Moreover, if it exceeds 1.0 parts by weight, film formation will occur on other parts such as the developer carrier, causing problems regarding the developer. Particularly preferably, 0.03 to 1.0 parts by weight is used.
It is 0 parts by weight.

In the present invention, examples of the binder resin of the toner include monopolymers of styrene and its substituted products such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, Polymer, tyrene-vinyltoluene copolymer,
Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer. Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer. Styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl Styrenic copolymers such as methyl ketone copolymer, styrene-butadiene copolymer, styrene-isobrene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, polyvinyl acetate, polyethylene, polybrobylene, silicone Resin, polyester, epoxy resin, polyvinyl butyral, rosin. Modified rosin, terbene resin, phenolic resin. Xylene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. may be used alone or in combination.

In the present invention, among these resins, styrene-acrylic copolymers are preferably used, particularly styrene-n-butyl acrylate (St-nBA) copolymers, styrene-n-butyl methacrylate (St-nBA) copolymers, and styrene-n-butyl methacrylate (St-nBA) copolymers. -nBMA)
Copolymer, styrene-n-butyl acrylate-2-ethylhexyl methacrylate (St-nBA-2EHMA
) copolymers etc. are preferably used.

Further, as coloring materials that can be added to the toner according to the present invention, conventionally known carbon black, copper phthalocyanine,
Iron black etc. can be used.

The toner according to the present invention may contain a magnetic material. The contained magnetic fine particles are substances that are magnetized when placed in a magnetic field, such as powders of ferromagnetic metals such as iron, cobalt, and nickel, or magnetite, γ-F e t
Alloys and compounds such as O s + ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of 2 to 20 m"/g, particularly 2.5 to 12 m" by nitrogen adsorption method.
/g, and preferably a magnetic powder having a Mohs hardness of 5 to 7.

The content of this magnetic powder is preferably 10 to 70% by weight based on the amount of toner.

Further, the toner of the present invention may contain a charge control agent if necessary, such as a metal complex salt of a monoazo dye; salicylic acid;
A negative charge control agent such as a metal complex salt of alkyl salicylic acid, sialkyl salicylic acid or naphthoic acid is used.

The toner according to the present invention is generally manufactured as follows.

■Uniformly disperse the binder resin, optionally magnetic material, and dyes and pigments as coloring agents using a mixer such as a Henschel mixer.

(2) Melt and knead the dispersion obtained above using a Niichi goo, an extruder, a roll mill, or the like.

■After coarsely pulverizing the mixed material with a cutter mill, hammer mill, etc., finely pulverize it with a jet mill, etc.

■Use a zigzag classifier to uniform the particle size distribution of the finely pulverized material and classify it into toner.

Other toner manufacturing methods that can be used include a polymerization method and a capsule method. An outline of these manufacturing methods will be described below.

(Polymerized toner) (1) A polymerizable monomer, an optional polymerization initiator, a colorant, etc. are granulated in an aqueous dispersion medium.

(2) Classifying the granulated monomer composition particles into appropriate particle sizes.

(2) Polymerizing the monomer composition particles having a specified particle size obtained by the above classification.

(2) After removing the dispersant by appropriate treatment, the polymerized material obtained above is filtered, washed with water, and dried to obtain l.ner.

(Capsule toner) ■Knead resin and, if necessary, magnetic powder etc. using a mixer to obtain a toner core material in a molten state.

■Pour toner core material into water and stir vigorously to create fine particle core material.

(2) Put the core material fine particles into the shell material solution, drop a poor solvent while stirring, and cover the core material surface with the shell material to encapsulate it.

(2) The capsules obtained above are passed through an oven and then dried to obtain a toner.

The present invention is particularly effective for toner manufactured by a process of pulverization using wind power.

This is thought to be due to the fact that toner produced by wind pulverization has more irregularities than other methods, and its sphericity is lower, resulting in a larger contact area with the drum and higher adhesion. .

The developer used in the image forming method of the present invention preferably further contains hydrophobic silica fine powder.

In the case of a negatively charged magnetic one-component developer, it contains negatively charged hydrophobic silica fine powder and positively charged resin fine particles treated with a silane coupling agent and/or silicone oil,
and 0.01 to 3 parts by weight of the silica per 100 parts by weight of the negatively charged magnetic toner, and 0.02 to 3 parts by weight of the resin fine particles.
The content is preferably within the range of 3 parts by weight.

The fine silica powder used in the present invention is so-called dry silica or fumed silica, which is produced by vapor phase oxidation of a silicon halide compound, and its surface is treated with a silane coupling agent and/or silicone oil. This is fine silica powder.

A preferred silane coupling agent includes hexamethyldisilazane (HMDS).

Preferred silicone oils include those having a viscosity of about 50 to 1,000 centistokes at 25°C, such as dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, and chlorphenyl silicone oil. , fluorine-modified silicone oil, etc. are preferred. For the purpose of the present invention, silicone oil containing a large amount of -OH groups, -COO groups, -NH2 groups, etc. is not preferred.

[Example] 1 part by weight of dog I0 paste The above mixture was melt-kneaded in a twin-screw ruder heated to 160°C, then cooled, and the cooled material was crushed into a mesh with an opening diameter of 2 mm in a hammer mill (mechanical crusher). Coarsely grind it to the level of a bath, then use a jet mill (wind-powered grinder) to
It was pulverized to about 0μ. The finely pulverized product was classified using a DS classifier (wind classifier) so that the volume average particle diameter as measured by a Coulter counter was 11.5 gm to prepare a negatively charged insulating magnetic toner.

The insulating magnetic toner had a triboelectric charge amount of -13 pc/g with respect to the iron powder carrier as measured by a blow-off method.

Zinc stearate (SZ-2000 manufactured by Sakai Chemical Co., Ltd.) was added as a film forming material to 100 parts by weight of the negatively charged magnetic toner.
) and 0.4 parts by weight of hydrophobic silicic acid fine powder treated with HMDS were respectively added to the toner and mixed in a Henschel mixer to prepare a one-component developer.

The obtained developer was transferred to a commercially available copying machine FC-5 (manufactured by Canon Inc., OPC laminated type negatively charged photoreceptor, drum diameter φ30).
A transfer device as shown in FIG. 1 was further incorporated into the transfer device. The conditions for the transfer roller are: surface rubber hardness of the transfer roller is 2r, transfer current is 1 pA, and contact pressure is 50 [g].
/cml.

The primary charging was set to -700V, and the photosensitive drum and developing drum (
A gap was set so that the developer layer on the magnet (within the magnet) was not in contact with the developer layer, and an AC bias (f = 1,800 Hz, Vl + 9 = 1) was applied.
, 600 V) and DC bias (Voc= -
Image formation was performed while applying a voltage of 300 V) to the developing drum. The toner fixed image produced and fixed by a heating and pressure roller was evaluated as follows. The results are shown in Table 1.

(1) Image density 2 Normal paper for copiers (75 g/m"
) Evaluation was made by maintaining image density when 1,000 sheets were passed.

○ (Good): 1.35 or more, Δ (Acceptable): l. O~1.34
, × (impossible): 1. 0 or less (2) Transfer condition: Strict transfer conditions, 120 g/m
” was passed through thick paper and evaluated based on the state of transfer omission.

○: Good, △: Practical, ×: Not practical (3) Paper conveyance condition: 1,000 sheets of 50 g/m" thin paper
Sheets were passed through and the occurrence of incorrect conveyance, such as skewed feeding, was evaluated.

○: Less than 1 time/1,000 sheets, △: 2 to 4 times/1,000 sheets, ×: 5 or more times/1,000 sheets (4) Image quality: Visually evaluated toner scattering, roughness, etc. .

◯: Good, △: Practical, x: Not Practical Image printing was carried out in the same manner as in Example 1, except that the contact pressure was set to zo[g/cml]. The results are shown in Table 1.

Image printing was carried out in the same manner as in Example 1, except that the contact pressure was 5 g/cm. The results are shown in Table 1.

4 Image formation was carried out in the same manner as in Example 1, except that 0.1 part by weight of aluminum stearate (SA-2000, manufactured by Sakai Chemical Co., Ltd.) was used as the film forming material. The results are shown in Table 1.

Image formation was carried out in the same manner as in Example 1, except that 0.1 part by weight of magnesium laurate was used as the material for forming the blood clot film. The results are shown in Table 1.

! Image formation was carried out in the same manner as in Example 1, except that 0.1 part by weight of calcium myristate was used as the 5-membered 1 film-forming substance. The results are shown in Table 1.

Blood supply dish l Silicone oil (KF manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a film-forming substance.
-96) Image printing was carried out in the same manner as in Example 1 except that the amount was 0.05 part by weight. The results are shown in Table 1.

Image formation was carried out in the same manner as in Example 1, except that the amount of the adhesive film-forming substance added was 0.02 parts by weight. The results are shown in Table I.

Image formation was carried out in the same manner as in Example 1, except that the amount of film-forming substance added was 1.0 parts by weight. The results are shown in Table 1.

Image printing was carried out in the same manner as in Example 1, except that the contact pressure for each unit was 2 g/cm. The results are shown in Table 1.

Image formation was carried out in the same manner as in Example 1, except that the amount of the film-forming substance added was 1.5 parts by weight. The results are shown in Table 1.

Comparison of results Except for not adding film-forming substances, Example 1 Image display was performed in the same manner as above.

Table 1 shows the results. Shown below.

Table 1 [Effects of the Invention] The present invention improves the developer under appropriate contact pressure during the transfer process, so it is possible to obtain high-quality images without causing transfer defects. .

[Brief explanation of drawings]

FIG. 1 shows an example of a transfer void, and FIGS. 2 and 3 are schematic side views of main parts of the image forming apparatus.

Claims (2)

[Claims] (1) In an image forming method including a step of developing an electrostatic charge image on an electrostatic charge image carrier with a developer and electrostatically transferring the developed image to a transfer material via a transfer device, [a] the electrostatic charge The image carrier and the transfer device have a linear pressure of 3 g/c.
[b] The surface layer of the electrostatic latent image holder has a contact angle with water of 8 m or more;
The substance that forms a smooth surface of 0° or more is 0.01 to 1.0
An image forming method characterized by using a developer containing parts by weight. (2) The image forming method according to claim (1), wherein the transfer device is a transfer roller or a transfer belt.