JPH021881A - How to develop an electrostatic latent image - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing electrostatic latent ridges using a non-magnetic one-component toner.

Conventional Techniques Conventionally, as a method for developing electrostatic latent images using non-magnetic one-component toner (generally made of colored resin particles), a thin layer of toner charged to a desired polarity by friction with the toner conveying member is deposited on the toner conveying member. The latent image surface of an electrostatic latent image holder (an electrophotographic photoreceptor, an electrostatic recording medium, etc. that holds an electrostatic latent image) is formed in a layer and is placed in contact with or in close proximity to the member. The so-called contact development method, in which the material is developed by bringing it into direct contact with the material, is widely used. In this method, a metal roller with a coating layer (called a developing roller) is generally used as the toner conveying member, but such a developing roller requires various functions for contact development. 1. For example, if the electrostatic latent image holder combined with the developing roller is a rigid body such as a selenium photoreceptor, the developing roller must have: ■ a flexible coating layer so as to obtain the necessary developing nip, and ■ contact. The coating layer on the core metal must be uniform in order to obtain the desired development characteristics, and more importantly, the characteristics of the surface or near the surface of the developing roller must be , ■ Constantly and stably imparting the desired charge polarity and amount of charge to the toner, ■ Good releasability from the toner,
Toner does not film; ■ Appropriate surface roughness (several μm or less) to form a uniform thin toner layer; ■ Smoothness to reduce chattering due to frictional resistance during contact. (1) Abrasion resistance. Regarding (2), when toner filming occurs, the amount of toner charge changes, causing unevenness in the amount of toner adhering to the developing roller, and as a result, there is a problem that unevenness of images occurs.

In response to these demands, the coating material for the core metal of the developing roller is a low-hardness elastic material, usually called rubber, such as nitrile-butadiene-rubber (NOR), ebichlorohydrin rubber (ECO), Polar rubbers such as acrylic rubber and chloroprene rubber, and high-resistance rubbers such as silicone rubber, ethylene-propylene rubber, and styrene-butadiene rubber, in which conductive fine particles of carbon, metal, etc. are dispersed, have been used.

However, it has been difficult for conventional developing rollers using these coated materials to satisfy the above-mentioned requirements, particularly regarding surface properties.

This is because the surface abrasiveness deteriorates as the hardness of the rubber decreases, making it difficult to finish the surface to the required surface roughness (Rz) for a developing roller, and because the surface is sticky, it is difficult to polish the surface with the contact member. This is due to the fact that it has high friction resistance, has low rubber strength and is therefore very easy to wear, and has poor toner releasability.

Note that the required items for the developing roller, especially the items listed below (1), are closely related to the toner, so improvements from the toner perspective were also desired.

7-Uniformity The purpose of the present invention is to improve the toner in contact development using a non-magnetic one-component 1-toner, together with the 1-henner and the conveying member, thereby achieving all the functional items required of the member, especially items related to surface properties. It is an object of the present invention to provide a method for developing an electrostatic latent image that satisfies the above requirements and can therefore consistently form high-quality images.

Week-1" Also, the method of the present invention involves forming a thin layer of toner charged to a desired polarity on a toner conveying member by friction with the member, and bringing this into contact with the member.

Alternatively, in a method of developing an electrostatic latent image by bringing it into contact with the latent image surface of an electrostatic latent image holder disposed in close proximity, a first coating layer made of an elastic material on a support and its A second coating layer made of a flexible resin and conductive fine particles is provided on the toner, and colored resin particles are used as the base toner, and the charging polarity of the base toner is changed by friction with the toner conveying member. This is characterized by the use of a mixed system in which fine particles that can be charged to the opposite polarity are added.

First, the toner conveying member used in the present invention will be explained.

The toner conveying member of the present invention is designed to separate functions by providing a first coating layer and a second coating layer on a support,
Usually, it is used in the form of a roller as in the past, but it can also be used in the form of a belt.

As the support, a metal roller is used in the case of a roller shape, and a plastic film, a metal film, etc. is used in the case of a belt shape. The materials, forming methods, etc. used for the first coating layer and the second coating layer are as follows.

Regarding the first coating layer: For the first coating layer, any elastic body constituting a conventional toner conveying member can be used. In particular, it is desirable that the elastic body suitable for the present invention has a volume resistivity (ρ) in the so-called medium resistance region of 10 6 to 10”Ω・am.Rubber used to form a stable elastic body with little variation in ρ Nitrile-butadiene rubber (NB) is a polar rubber.
R), epichlorohydrin rubber (ECR), acrylic rubber.

There are chloroprene rubbers, silicone rubbers, urethane rubbers, ethylene-propylene rubbers, etc. in which conductive fine particles such as carbon black and metal oxide particles are dispersed.
Styrene-butadiene rubber etc. can also be used, but especially NB
R, ECR or mixtures thereof are preferred. For example, in the case of NBR, ρ can be adjusted by increasing or decreasing the amount of nitrile, or by changing the amount of NBR.
In the case of a mixed system of BR and ECR, this can be easily done by changing the mixing ratio. Of course these have low hardness,
It has sufficient properties necessary for practical use, such as wear resistance. Also N
Since the BR-ECR mixture has better ozone resistance than NOR, a developing member with higher reliability can be obtained.

Note that the thickness of the first rlI layer is suitably about 0.5 to 10 mm. In addition, the first coating layer is generally formed by forming the elastic body by press molding, steam molding, etc. when a roller is used as the support, or by dissolving the elastic body in an appropriate solvent when using a film as the support. The solution is dissolved and formed into a film to a desired thickness on a support by a coating method such as a dipping method or a spray method.

Regarding the second rI1 layer: It is the surface layer of the toner conveying member and is in contact with the toner, so it has good releasability with respect to the toner, and has a volume resistivity ρ.
is 10' to 1011 Ω・Cm, which is the same level as the elastic layer,
Flexible thickness 5-60 μm, especially 30-50 μm
The synthetic resin layer is preferred.

In addition, the elongation of this resin is 10 to 500%, especially 30 to 3
00% is preferable. If it is less than 10%, it will not be able to follow the low hardness elastic body, causing cracks to occur when compressing the toner conveying member, and if it is more than 500%, the polishing properties will be poor, so the desired surface roughness cannot be achieved. is not obtained.

Furthermore, if the thickness of the resin layer is less than 10 μm, especially less than 5 μm, the influence of the elastic material of the first coating layer will be strong, and the variation in the thickness of the resin layer will become relatively large, which is not preferable. On the other hand, if the thickness exceeds 60 .mu.m, the positive effect of the first layer will be reduced, which is not preferable. In any case, the thickness of the resin layer depends on the electrical properties of the selected resin (in general, the higher the volume resistivity, the thinner the resin is), the more abrasive the resin, the thinner the resin, etc., and the first coating. Determine the overall balance with the layers.

Examples of synthetic resins having the above-mentioned desirable properties for the second coating layer include silicone resins, urethane resins, fluororesins, modified fluororesins, and the like. In order to make these resins medium resistance, carbon black, various metal fine particles, etc. are added as conductive materials, but in order to maintain the properties of the synthetic resin as much as possible and make them medium resistance, conductive materials are added. It is desirable that the amount added be as small as possible, and carbon black is preferred for this purpose.

Generally, the second coating layer is formed by dispersing the resin and conductive particles in an appropriate solvent using a dispersing machine such as a ball mill or sand mill, adjusting the viscosity of the coating liquid with a solvent as necessary, and then spraying the coating liquid. A film is formed to a desired thickness on the first coating layer by a coating method such as a coating method or a dipping method.

In this case, if necessary, a suitable primer may be used between the first coating layer and the second coating layer to further firmly bond these layers.

Note that the second coat rI1. formed by the coating liquid. Variations in ρ may occur in the layers, but such problems can be easily solved by sufficiently stirring the coating solution during coating and coating in a uniform dispersion state.

Next, toner used with the above-described toner conveying member will be explained.

The toner of the present invention has the performance required in contact development: it is smoothly supplied onto the toner conveying member without causing agglomeration, lumps, etc., it is charged to a desired polarity with an appropriate amount of charge by friction with this member, and A thin film can be uniformly and easily formed on the member (the toner thin layer is generally formed by a toner thin layer forming member such as a blade).
can be mentioned. However, conventional toner made of general colored resin particles cannot satisfy all of these requirements, and has poor transportability, such as agglomeration and lumps during supply, especially due to environmental changes or repeated use. It is also difficult to form a uniform thin layer, and as a result, combined with the performance of the toner conveying member, residual images and uneven image density occur, making it difficult to obtain clear images. As a result of various studies, the inventors of the present invention found that a mixture was prepared in which normal colored resin particles were used as a base toner, and fine particles that could be charged to a polarity opposite to the 71F polarity of the base toner by friction with a toner conveying member were added. It has been found that when this system is used, the fluidity of the base toner is improved, and as a result, aggregation does not occur during supply, and therefore the transportability is also improved.

The base toner, which is one component of the mixed toner described above, is made of colored resin particles, which is a conventional general toner. The colored resin particles are produced by melt-kneading a binder resin, a colorant and, if necessary, a polarity control agent, pulverizing the kneaded material, and classifying it into an appropriate particle size. The binder resin used here is polystyrene, chloropolystyrene, and polystyrene.
α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer , styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate ester copolymer (styrene-methyl methacrylate copolymer).

Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer Styrenic resins such as polymers (unipolymers or copolymers containing styrene or styrene substitutes), vinyl chloride resins, rosin-modified maleic acid resins, phenolic resins, epoxy resins, polyester resins, low molecular weight polyethylene, low molecular weight polypropylene, Examples include ionomer resins, polyurethane resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins, polyvinyl butyral, and mixtures thereof.

Coloring agents include carbon black, various dyes, and pigments.

Examples of polarity control agents include quaternary ammonium compounds and amino group-containing polymers for positive polarity, and salicylic acid metal salts for negative polarity.

In addition, the base toner contains various plasticizers (dibutyl phthalate, dioctyl phthalate, etc.) and resistance adjusters (tin oxide,
It is also possible to add auxiliary agents such as lead oxide, antimony oxide, etc.).

The additive fine particles that are the other component of the mixed toner include Sin, TiO2, An20. , CeO, SiC,
Zinc stearate and the like are used. The amount of these additive particles added is 1 x 10-
It is preferable to adjust the amount to be 4 to 5 X 1O-2B/cm2. This abundance is lXl0−'m
If the amount is less than 5 g/cm2, the toner transfer efficiency (development efficiency) from the toner transport member to the latent image holding member is poor, resulting in an image with low image density and no contrast.
If it exceeds X 10-2 mg/c+n', the image density is sufficient, but fogging, background stains, etc. may occur.

Next, an example of manufacturing a developing roller as a toner conveying member used in the present invention will be shown below.

(Left below) (1) Example table for forming the first coating layer - 1 Monthly income (1) B) After kneading each mixture uniformly using two rolls at the mixing ratio shown in Table 1, The material was then vulcanized and formed into an 8 mm diameter cored roller with an elastic layer thickness Gvn and a roller outer diameter of 20 mm, followed by secondary vulcanization at 150° C. for 4 hours. The volume resistivity and rubber hardness of this forming roller are also shown in Table-1. The method for measuring volume resistivity and rubber hardness is as follows.

To measure the volume resistivity, the sample roller was heated at 20°C for 60S.
After being left in an RI+ environment for 16 hours, the test was carried out using a Goo 21 Electrometer 6100. The electrode during measurement was a 10 mm wide copper foil tape (3M tape No. 124).
5), the distance between the main electrode and the guard electrode is set to 1 mm.

Rubber hardness can also be measured using the vulcanized rubber physical test method JIS K.
6301.

(Margin below) (2) Formation example of second coating layer Table-2 (Blending unit part 1! The composition of the ingredients is shown in Table 3.

Table 3 The above formulations were dispersed in a ball mill to create masterbatches. In addition, as carbon black, Black
K Pearls L (Cabot) was used.

Based on these different types of masterbatches, a main agent and a curing agent were added to adjust the carbon black/resin solid content = F/R ratio to 0.10. Obtained coating) Solvent (a) Toluene xylene (b) Toluene Ethyl acetate 50wt% 50st% 39,Ost% 17.5wt% Butyl acetate 17.5wt% Ethyl cellosolve acetate 17.5wt% Methyl isobutyl ketone 3. ht% xylene
2.6%it% cyclohexane
2.0% (C) xylene
The 100% second coating layer was formed by spray coating the second coating layer coating on the first coating layer and drying and curing at 100° C. for 2 hours. Note that the thickness of the second coating layer is 30 μm.

The method of the present invention will be explained below using examples.

Example 1 Low molecular weight polypropylene 5 n salicylic acid zinc salt 3 was heated and kneaded in a heated roll mill, cooled, coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer to obtain a product. The fine powder obtained was classified to obtain a base toner having an average particle size of 10 μm. When this base l.toner was formed into a thin layer on a toner transport member, the amount of charge (hereinafter referred to as 07M on the transport member) was −14.2 μc/g. Next, 07M on the conveying member is + for this base toner.
Titanium oxide fine particles of 2.5 μc/g were added so that the amount present in the development area was 1.5 x 10'' mg/cm2 to obtain the mixed toner of the present invention. The method for measuring the charge amount (07M) of fine particles is as follows.That is, the thin layer of toner on a toner conveying member is transferred to a metal suction cell with a filter 10 inside as shown in FIG. The weight M of the toner sucked from the suction port 12 of the suction mount and collected at the rear end of the suction cell and the amount of electricity Q flowing during suction are determined using a coulomb meter 13, and 07M is calculated.

On the other hand, FIG. 2 shows a developing roller having a second coating layer prepared according to Example 1 shown in Table 3 using Formulation 1 shown in Table 2 as a master batch and a second coating layer prepared according to Formulation 1 shown in Table 1. [In the figure, 1 is an electrostatic latent image holding member (electrophotographic photoreceptor in this case), 2 is a toner conveying member (developing roller in this case), 3 is a toner layer thickness regulating member, 4 is a toner supplying member, 5 is a stirring blade, 6 is a toner, and 7 is a toner tank], the mixed toner is supplied thereto, and the amount of additive fine particles in the development area is 1.5X 10 at room temperature and normal humidity.
The electrostatic latent image on the electrophotographic photoreceptor was developed under the conditions of -'mg/am2.

The resulting image was then transferred onto plain paper and fixed using a heated roller, resulting in a clear copy image. 10 more
I made 000 copies in a row, but the image quality remained the same as the initial one.
It was clear.

Further, clear copy images were obtained under both environments of 10° C.-15% R)1 and 30° C.-90% R)1.

To explain in more detail the contact development method as shown in FIG.
The toner is forcibly brought to the toner supply member 4 and supplied to the toner supply member 4.

Then, the toner taken into the toner supply member 4 is conveyed to the toner conveyance member 2 by strong rotation of the toner supply member in the direction of the arrow, and is rubbed by the toner conveyance member 2, where it is electrostatically or physically attracted. Then, by rotating the toner conveying member 2 and toner layer thickness regulating member 3, a uniform thin layer of toner is formed on the conveying member and frictionally charged. Thereafter, the toner is transported to the latent image surface of the electrostatic latent image holding member 1 that is placed in contact with or in close proximity to the toner conveying member 2, and the toner 7I
The electrostatic latent image is developed by the contact with m.

Example 2 A base toner was prepared in the same manner as in Example 1 using 5 n of low molecular weight polypropylene and 4 n of metal-containing complex. The 07M of this base toner on the conveying member was -12.1 μc/g. With respect to this base toner, aluminum oxide fine particles with 07M of +7.5 μc/g on the conveying member are added in an amount of IlX in the development area.
The mixture was added to give lo-3ffi/am2 to obtain the mixed toner of the present invention.

Next, a developing roller having a second coating layer prepared using Formulation 2 of Table 1 and a second coating layer prepared according to Specific Example 2 of Table 3 using the masterbatch of Formulation 2 of Table 2 was applied. The mixed toner was then set in the developing device shown in FIG. 1, and the mixed toner was subsequently supplied to this device. Similarly, when continuous copying was performed at room temperature and humidity, clear copies were obtained both at the initial stage and after copying 10,000 copies.

Furthermore, clear images were obtained under both environments of 10° C.-15% R)I and 30° C.-90% RH.

Example 3 A base toner was prepared in the same manner as in Example 1 using 5 low molecular weight polypropylene, 3 zinc white salicylate, and 6 carbon black (C#44, manufactured by Mitsubishi Carbon). The Q/M of this base toner on the conveying member was -15.0 μc/g. Next, for this base toner, Q/M on the conveying member is +
A mixed toner of the present invention was obtained by adding 16.5 .mu.c/g of fine zinc stearate particles in an amount of 5.times.10@-4 mg/Cm2 in the development area.

Next, a developing roller having a first coating layer prepared using Formulation 3 of Table 1 and a second coating layer prepared according to Example 3 of Table 3 using the masterbatch of Formulation 3 of Table 2 was applied. The mixed toner was then set in the developing device shown in FIG. Similarly, when continuous copying was performed at room temperature and humidity, clear copies were obtained both at the initial stage and after copying 10,000 copies.

Furthermore, clear images were obtained under both environments of 10° C.-15% 11+1 and 30° C.-90% RH.

Example 4 A mixed toner was prepared in the same manner as in Example 1 except that nigrosine dye was used instead of zinc salicylate.

The Q/M of this mixed toner on the conveying member is +13.1μ
6 Next, silicon oxide fine particles with a Q/M of -20.0 μc/g on the conveying member were added to this base toner, which had a Q/M of -20.0 μc/g.
It was added so that the amount present in the development area was I x 10-3 mg/am'' to obtain the mixed toner of the present invention.

Next, the developing roller used in Example 1 was set in the apparatus shown in FIG. 1, and after the charge polarity of the latent image on the photoreceptor was reversed from that in Example 1, the mixed toner was supplied to this apparatus. , hereinafter, the amount of additive fine particles present in the development area is expressed as l x 10-
Continuous copying was performed at normal temperature and normal humidity in the same manner as in Example 1 except that the concentration was 3 mg/cm2, and clear copies were obtained both at the initial stage and after copying 10,000 copies.

Furthermore, clear images were obtained under both environments of 10° C.-15% RH and 30° C.-90% R11.

Comparative Example 1 The first coating layer created using the formulation 1 in Table 1 and Table 3
Development was carried out in the same manner as in Example 1, except for using a developing roller having a second coating layer prepared using the formulation from Specific Example 1 except for the masterbatch (therefore, it did not contain carbon black either). A clear image was obtained under normal temperature and normal humidity, but under an environment of 10° C.-15% R+1, stains due to toner adhesion to the background portion were observed in the copied image.

Comparative Example 2 Copying was performed at room temperature and humidity in the same manner as in Example 1 except that toner 1 to base 1 was used alone instead of the mixed toner, and an image with a slightly low density was obtained at the initial stage of copying. However, after copying 10,000 sheets, the image density further decreased.

Comparative Example 3 A mixed toner was prepared in the same manner as in Example 1 except that the silicon oxide fine particles used in Example 4 were used as the additive fine particles. When I developed it at room temperature and humidity, I found that the density was low.
An image with no contrast was obtained.

Comparative Example 4 A mixed toner was prepared in the same manner as in Example 1 except that the base toner used in Example 4 was used, and the charge polarity of the latent image on the photoreceptor was reversed from Example 1. When development was carried out at room temperature and humidity in the same manner as in Example 1, an image with low density and no contrast was obtained.

Example 5 The amount of additive fine particles in the development area was 5 x 10-5 mg.
When continuous copying was performed at room temperature and humidity in the same manner as in Example 1 except that /am2 was used, an image with slightly low density was obtained at the initial stage of copying, and the image density further decreased slightly after copying 10,000 sheets. .

Example 6 The amount of additive fine particles in the development area was set to 8×10-”mg
Continuous copying was performed at room temperature and humidity using the same method as in Example 1, except that the setting was 10,000 sheets. Fog occurred.

The following results are shown in Table-4.

According to Table-4. ] As described above, the method of the present invention improves the toner together with the toner conveying member in the contact development method using non-magnetic one-component toner, thereby achieving all the functional items required of the member,
In particular, it satisfies the requirements regarding surface properties, and therefore can consistently form high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a device for measuring the amount of charge of each mixed component of a mixed toner used in the method of the present invention, and FIG. 2 is a schematic diagram of a contact developing device used in Examples. 1: Electrostatic latent image carrier 2: Toner transport member 3: Toner layer thickness regulating member 4: Toner supply member 5: Stirring blade

Claims (1)

[Claims] 1. Form a thin layer of toner charged to a desired polarity by friction with the toner conveying member, and transfer this to an electrostatic latent image carrier disposed in contact with or close to the toner conveying member. In a method of developing an electrostatic latent image by bringing it into contact with a latent image surface, the toner conveying member includes a first coating layer made of an elastic material on a support and a second coating layer made of a flexible resin and conductive fine particles on the support. A mixed system in which colored resin particles are used as a base toner, and fine particles that can be charged to a polarity opposite to that of the base toner by friction with a toner conveying member are added. A method for developing an electrostatic latent image, characterized by using.