JP2895837B2 - Method of developing electrostatic latent image - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for developing an electrostatic latent image using a non-magnetic one-component toner.

2. Description of the Related Art Conventionally, as a method for developing an electrostatic latent image using a non-magnetic one-component toner (generally made of colored resin particles), a thin layer of a toner charged to a desired polarity on a toner conveying member by friction with the member is used. On the latent image surface of an electrostatic latent image holding member (electrophotographic photosensitive member, electrostatic recording member, etc. holding an electrostatic latent image) disposed in contact with or in close proximity to the member. A so-called contact developing method of directly contacting and developing is widely used. In this method, as a toner conveying member, a member provided with a coating layer on a metal roller (referred to as a developing roller) is generally used. However, since such a developing roller needs various functions for contact development. For example, when the electrostatic latent image holding member combined with the developing roller is a rigid body such as a selenium photoreceptor, the coating layer is flexible so that a necessary developing nip is obtained on the developing roller. In order to have sufficient recoverability against force and to obtain the desired development characteristics, the coating layer on the cored bar must be uniform and, more importantly, the properties of the developing roller surface or near the surface are always stable To give a desired charge polarity and charge amount to the toner, good releasability from the toner, no filming of the toner, and an appropriate surface roughness (several μm) for forming a uniform thin toner layer. It has the following), that in order to reduce such chatter due to frictional resistance during contact is slipping, that such is the wear resistance is required. Regarding the filming of the toner, the amount of charge of the toner changes, and the amount of toner adhered on the developing roller becomes uneven. As a result, there is a problem that image unevenness occurs.

In response to these requirements, as a coating material for the core of the developing roller, a low-hardness elastic body, usually called rubber,
For example, polar rubbers such as nitrile-butadiene rubber (NBR), epichlorohydrin rubber (ECO), acrylic rubber, chloroprene rubber, silicone rubber, ethylene rubber
A material in which conductive fine particles such as carbon and metal are dispersed in high-resistance rubber such as propylene rubber and styrene-butadiene rubber has been used.

However, it has been difficult for conventional developing rollers using these coating materials to satisfy the above requirements, particularly the following items relating to surface characteristics. This is because, as the rubber becomes low in hardness, the surface abrasion becomes worse, it is difficult to finish to the required surface roughness (Rz) as a developing roller, and because of the surface tackiness, This is due to the fact that the friction resistance is high, the rubber strength is weak, and the rubber is weak, so that it is very easy to wear, and the toner releasability is poor.

Since the above-mentioned required items of the developing roller, especially the following items are closely related to the toner, improvement in terms of the toner has been desired.

The object of the present invention is to improve the toner together with the toner conveying member in the contact developing method using a non-magnetic one-component toner, thereby satisfying all the functional items required for the member, especially the items relating to the surface characteristics, and therefore always satisfy the requirements. An object of the present invention is to provide a method for developing an electrostatic latent image capable of stably forming a high-quality image.

The method of the present invention forms a thin layer of toner charged to a desired polarity by friction with the member on a toner conveying member, and forms the electrostatic latent image in contact with or close to the member. In the method of developing an electrostatic latent image by contacting the latent image surface of a holding member, a toner transport member includes a first coating layer made of an elastic material on a support and a flexible resin and conductive fine particles formed thereon. A colored resin particle as a base toner, and fine particles capable of being charged to a polarity opposite to that of the base toner due to friction with the toner conveying member. Characterized in that a mixed system is used.

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

The toner conveying member of the present invention has a function separation by providing a first coating layer and a second coating layer on a support, and is usually used in the form of a roller as in the related art, but is used in the form of a belt. You can also.

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

Regarding the first coating layer: The first coating layer can use any of the elastic bodies that constitute the conventional toner conveying member. In particular, it is desirable that the elastic body suitable for the present invention has a volume resistivity (ρ) in a so-called medium resistance region of 10 ⁶ to 10 ¹¹ Ω · cm. As a rubber used to form a stable elastic body with little variation in ρ,
Nitrile-butadiene rubber (NBR), which is a polar rubber,
There are epichlorohydrin rubber (ECR), acrylic rubber, chloroprene rubber, etc. Also used are silicone rubber, urethane rubber, ethylene-propylene rubber, styrene-butadiene rubber, etc. in which carbon black, metal oxide particles, etc. are dispersed as conductive fine particles. Yes, but especially NBR, ECR
Or a mixture thereof is preferred. Adjustment of ρ is, for example, NBR
In the case of (1), it can be easily carried out by increasing or decreasing the amount of nitrile, and in the case of a mixed system of NBR and ECR, by changing the mixing ratio. Of course, these have sufficient properties required for practical use, such as low hardness and wear resistance. In the case of the NBR-ECR mixed system, the ozone resistance is superior to that of NBR, so that a more reliable developing member can be obtained.

The thickness of the first coating layer is suitably about 0.5 to 10 mm. Also, the method of forming the first coating layer is generally such that when a roller is used as a support, the elastic body is formed by press molding, steam molding, or the like, and when a film is used as the support, the elastic body is dissolved in an appropriate solvent. It is dissolved and then formed into a desired thickness on a support by a coating method such as a dipping method or a spray method.

Second coating layer for: a surface layer of the toner carrying member, because a layer in contact with the toner releasing property is good to the toner volume resistivity ρ elastic body layer of the same level 10 ⁶ to 10 ¹¹ A flexible resin layer having a thickness of 5 to 60 μm, particularly 30 to 50 μm, which is Ω · cm and flexible is preferable. The elongation of this resin is 10-500%, especially 3
Those having 0 to 300% are preferred. If it is less than 10%, it will not be able to follow the low-hardness elastic body, causing cracks or the like when the toner conveying member is compressed. Can not be obtained.

On the other hand, when the thickness of the resin layer is 10 μm or less, particularly 5 μm or less, the influence of the elastic body of the first coating layer appears strongly, and the thickness variation of the resin layer is relatively large. On the other hand, when the thickness exceeds 60 μm, the positive effect of the first coating layer is undesirably reduced. In any case, the thickness of the resin layer depends on the properties of the selected resin, such as the electrical characteristics (in general, the higher the volume resistivity, the thinner the resin may be) and the higher the abrasion, the smaller the thickness. Determined by taking into account the balance with the layers.

Examples of the synthetic resin having the above-mentioned desirable properties as the second coating layer include a silicone resin, a urethane resin, a fluorine resin, and a modified fluorine resin. In order to make these resins have a medium resistance, carbon black and various kinds of metal fine particles are added as conductive materials. The addition amount is desirably as small as possible, and for that purpose, carbo black is preferred.

The method for forming the second coating layer is generally such that the resin and the conductive fine particles are dispersed in an appropriate solvent, a ball mill, a disperser such as a sand mill, and the viscosity of the coating solution is adjusted with a solvent as necessary, and then sprayed. It is intended to form a film to a desired thickness on the first coating layer by a coating method such as a dipping method or a dipping method.

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

In the second coating layer formed by the coating liquid, there may be a variation in ρ. However, such a problem is caused by sufficiently stirring the coating liquid at the time of coating to perform coating in a uniform dispersion state. This can be easily solved.

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

The toner of the present invention is smoothly supplied without causing agglomeration and lump on the toner conveying member as a performance required in contact development, and is charged to a desired polarity with an appropriate charge amount by friction with the member, and The ability to form a thin film uniformly and easily on the member (the thin toner layer is generally formed by a thin toner layer forming member such as a blade). However, conventional toners composed of general colored resin particles cannot satisfy all of these requirements, and have poor transportability during supply, particularly due to aggregation or lumps due to environmental changes or repeated use. It was also difficult to form a thin layer, and as a result, afterimages and image density unevenness were generated in combination with the performance of the toner conveying member, and it was difficult to obtain a clear image. The inventors of the present invention have made various investigations and have found that a mixed system in which ordinary colored resin particles are used as a base toner and fine particles that can be charged to a polarity opposite to the charge polarity of the base toner due to friction with the toner conveying member is added thereto. It was found that the use of the compound improved the fluidity of the base toner, and as a result, aggregation and the like did not occur at the time of supply, thereby improving the transportability.

The base toner, which is one component of the above-described mixed toner, is made of colored resin particles which are conventional general toners. The colored resin particles are produced by melt-kneading a binder resin, a colorant and, if necessary, a polarity controlling agent, pulverizing the kneaded material, and classifying the kneaded material to an appropriate particle size. As the binder resin, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer) Polymers, styrene-octyl acrylate copolymers, styrene-phenyl acrylate copolymers, etc.), styrene-methacrylate copolymers (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer,
Styrene-based resins (styrene or styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl methyl acrylate copolymer, styrene-acrylonitrile-acrylate copolymer, etc. Styrene-substituted homopolymer or copolymer), vinyl chloride resin, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene,
Ionomer resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin,
Polyvinyl butyral and the like and mixtures thereof.

Colorants include carbon black, various dyes and pigments.

Examples of the polarity controlling agent include a quaternary ammonium compound and an amino group-containing polymer for positive polarity, and a metal salicylate for negative polarity.

In addition, the base toner has thermal characteristics, electrical characteristics,
For the purpose of adjusting physical properties and the like, it is also possible to add auxiliaries such as various plasticizers (such as dibutyl phthalate and dioctyl phthalate) and resistance adjusting agents (such as tin oxide, lead oxide and antimony oxide).

As the fine particles for addition, which is the other component of the mixed toner, SiO ₂ , TiO ₂ , Al ₂ O ₃ , CeO, Sic, zinc stearate, etc. which are generally known as a fluidity improver, an abrasive, or a lubricant are used. Is done. The amount of the fine particles for addition is set so that the fine particles are present in an amount of 1 × 10 ^{−4 to} 5 × 10 ⁻² mg / cm ² in a developing area where the toner thin layer on the toner conveying member and the latent image holding member are in contact with each other. It is preferable that the adjustment be made. If the abundance is less than 1 × 10 ⁻⁴ mg / cm ² , the transfer efficiency (development efficiency) of the toner from the toner conveying member to the latent image holding member is poor, resulting in an image with low image density and no contrast. When the abundance exceeds 5 × 10 ^-2 mg / cm ² , the image density is sufficient, but fog and background stain may occur.

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

(1) Example of forming first coating layer After kneading uniformly using two rolls at the mixing ratios in Table 1, primary vulcanization was performed under the above conditions, and the thickness of the elastic layer was 6 mm on a 8 mmφ cored roller, and the outer diameter of the roller was 20 mm.
And then vulcanized at 150 ° C. for 4 hours. Table 1 also shows the volume resistivity and the rubber hardness of this forming roller. The measuring methods of the volume resistivity and the rubber hardness are as follows.

For measuring the volume resistivity, set the sample roller at 20 ° C and 60SRH
After standing in the environment for 16 hours, the measurement is performed using an electrometer 610C manufactured by Keithley. The electrode at the time of measurement uses a copper foil tape of 10 mm width (3M tape No.1245), and the distance between the main electrode and the guard electrode is 1 mm.

The measurement of rubber hardness is based on vulcanized rubber physical test method JIS K630.
Perform according to 1.

(2) Example of forming second coating layer The above composition was dispersed in a ball mill to prepare a master batch. The carbon black is Black
Pearls L (Cabot) was used.

Based on this type of different masterbatch, base resin and hardener are added to make the carbon black / resin solid content = F / R ratio
Adjusted to 0.10. Table 3 shows the composition of the obtained paint.

The second coating layer was formed by spray-coating the coating material for the second coating layer on the first coating layer and drying and curing at 100 ° C. for 2 hours. The thickness of the second coating layer is 30 μm.

 Hereinafter, the method of the present invention will be described with reference to examples.

Example 1 95 parts by weight of a styrene-acrylic resin (SBM-73, manufactured by Sanyo Chemical), low molecular weight polypropylene 5 亜 鉛 zinc salicylate 3 〃 carbon black (C # 44, manufactured by Mitsubishi Carbon) 7 加熱 was heated and kneaded with a hot roll mill. After cooling, the mixture was roughly pulverized using a hammer mill and then pulverized with a pulverizer using an air jet method, and the obtained fine powder was classified to obtain a base toner having an average particle diameter of 10 μm. The charge amount (hereinafter referred to as Q / M on the conveying member) when the base toner was thinned on the toner conveying member was -14.2 μc / g. Next, titanium oxide fine particles having a Q / M of +2.5 μc / g on the conveying member were added to the base toner so that the abundance in the development area became 1.5 × 10 ⁻³ mg / cm ² , Was obtained. The method for measuring the charge amount (Q / M) of the base toner and the fine particles for addition is as follows. That is, the thinned toner on the toner conveying member is sucked from a suction port 12 of a metal suction device having a metal suction cell 11 having a filter 10 therein as shown in FIG. The weight M of the toner and the quantity of electricity Q flowing during the suction are measured by a coulomb meter 13,
Calculate Q / M.

On the other hand, the developing roller having the first coating layer prepared in Formulation 1 in Table 1 and the second coating layer prepared in Example 1 in Table 3 using Formulation 1 in Table 2 as the masterbatch was used as the second batch.
Contact developing device shown in the figure [1 is an electrostatic latent image holding member (here, an electrophotographic photosensitive member) 2 is a toner conveying member (here, a developing roller), 3 is a toner layer thickness regulating member, and 4 is a toner supply Member, 5 is a stirring blade, 6 is a toner, 7 is a toner tank], and the mixed toner is supplied thereto. At room temperature and normal humidity, the amount of fine particles for addition in the development area is 1.5 × 10 ^{− 3} mg /
The electrostatic latent image on the electrophotographic photosensitive member was developed under the condition of cm ² . Next, the obtained image was transferred onto plain paper and fixed with a hot roller, whereby a clear copy image was obtained. Further
10,000 copies were made continuously, but the image quality was the same as the initial one.
It was clear.

In addition, a clear copy image was obtained under both environments of 10 ° C.-15% RH and 30 ° C.-90% RH.

The contact developing method as shown in FIG. 2 will be described in more detail. Toner (in this case, mixed toner) 6 contained in the toner tank 7 is forcibly brought to the toner supply member 4 by the stirring blade 5. Is supplied to the toner supply member 4. Then, the toner taken in the toner supply member 4 is conveyed to the toner conveying member 2 by the toner supply member being strongly rotated in the direction of the arrow, and is rubbed, and electrostatically or physically attracted by the toner. Then, a uniform thin toner layer is formed on the conveying member by the rotation of the toner conveying member 2 and the toner layer thickness regulating member 3, and the toner is charged by friction. Thereafter, the electrostatic latent image is transported to the latent image surface of the electrostatic latent image holding member 1 arranged in contact with or in close proximity to the toner conveying member 2, and the electrostatic latent image is developed by contact with the toner thin layer.

Example 2 95 parts by weight of a styrene-acrylic resin (SBM-73, manufactured by Sanyo Chemical) low molecular weight polypropylene 5 {metal-containing complex 4} carbon black (C # 44, manufactured by Mitsubishi Carbon) 6} A mother toner was prepared in the same manner. The Q / M of the mother toner on the conveying member was −12.1 μc / g.
Q / M on the conveying member is + 7.5μc / g for this base toner.
Aluminum oxide fine particles in the developing area are 1 ×
It was added so as to have a concentration of 10 ⁻³ mg / cm ² to obtain a mixed toner of the present invention.

Next, a developing roller having a first coating layer prepared using Formulation 2 in Table 1 and a second coating layer prepared in Example 2 in Table-3 using the master batch of Formulation 2 in Table-2 was used. 1
The same as in Example 1 except that the mixed toner was set in the developing device shown in the figure and then the mixed toner was supplied to this device, and the amount of the fine particles for addition in the developing area was set to 1 × 10 ⁻³ mg / cm ^2. When continuous copying was performed at room temperature and normal humidity, a clear copy was obtained both at the beginning and after 10,000 copies.

Further, a clear image was obtained under both environments of 10 ° C.-15% RH and 30 ° C.-90% RH.

Example 3 95 parts by weight of styrene-acrylic resin (SBM-700, manufactured by Sanyo Kasei) low molecular weight polypropylene 5 {zinc white salicylate 3} carbon black (C # 44, manufactured by Mitsubishi Carbon) 6} A mother toner was prepared in the same manner.
The Q / M of the mother toner on the conveying member was -15.0 μc / g. Next, for this base toner, Q / M on the conveying member is +1.
6.5 μc / g zinc stearate microparticles were added so that the abundance in the development area was 5 × 10 ⁻⁴ mg / cm ² to obtain a mixed toner of the present invention.

Next, a developing roller having a first coating layer prepared using Formulation 3 in Table 1 and a second coating layer prepared in Example 3 in Table-3 using the master batch of Formulation 3 in Table-2 was used. 1
The same as in Example 1 except that the mixed toner was set in the developing device shown in the figure and the mixed toner was continuously supplied to the device, and the amount of the fine particles for addition in the developing region was changed to 5 × 10 ⁻⁴ mg / cm ^2. When continuous copying was performed at room temperature and normal humidity, a clear copy was obtained both at the beginning and after 10,000 copies.

Further, a clear image was obtained under both environments of 10 ° C.-15% RH and 30 ° C.-90% RH.

Example 4 A mixed toner was prepared in the same manner as in Example 1 except that a nigrosine dye was used instead of the zinc salicylate. Q / M of the mixed toner on the conveying member is + 13.1μc / g
Met. Next, the Q /
Silicon oxide fine particles having an M of −20.0 μc / g were added so that the abundance in the development region was 1 × 10 ⁻³ mg / cm ² , to obtain a mixed toner of the present invention.

Next, the developing roller used in the first embodiment is set in the apparatus shown in FIG. 1, and the charge polarity of the latent image on the photosensitive member is reversed from that in the first embodiment. Hereinafter, the abundance of the fine particles for addition in the development area is 1 × 10 ⁻³ mg / c
When addition was m ² was subjected to continuous copying under Similarly normal temperature and normal humidity as in Example 1, the initial nor clear after copying 10,000 sheets copying is obtained.

Further, a clear image was obtained under both environments of 10 ° C.-15% RH and 30 ° C.-90% RH.

Comparative Example 1 First coating layer prepared using Formulation 1 in Table 1 and Table
Developing was carried out in the same manner as in Example 1 except that a developing roller having a second coating layer prepared using a formulation excluding the masterbatch from Example 1 of Example 3 (and thus containing no carbon black) was used. Although a clear image was obtained under normal temperature and normal humidity, in an environment of 10 ° C. and 15% RH, the copy image was stained by toner adhesion to the background.

Comparative Example 2 Copying was performed at room temperature and normal humidity in the same manner as in Example 1 except that the base toner was used alone instead of the mixed toner. After 10,000 copies, 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 fine particles for addition, and the same procedure as in Example 1 was performed using this mixed toner. When development was carried out under normal temperature and normal humidity, an image having low density and 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 that in Example 1. When development was carried out at room temperature and normal humidity in the same manner as in Example 1, the density was low.
An image without contrast was obtained.

Example 5 The amount of fine particles for addition in the development area was 5 × 10 ⁻⁵ mg / cm ²
Continuous copying was carried out at room temperature and normal humidity in the same manner as in Example 1, except that an image having a slightly lower density was obtained at the beginning of copying, and the image density further decreased slightly after copying 10,000 sheets.

Example 6 The abundance of the fine particles for addition in the development area was 8 × 10 ⁻² mg / cm ²
Continuous copying was carried out at room temperature and normal humidity in the same manner as in Example 1 except that a clear image with high density was obtained at the beginning of copying, but after 10,000 copies, some background stains and fog occurred. did.

 Table 4 below shows the results.

As described above, the method of the present invention satisfies all the functional items required for the above-mentioned member by improving the toner together with the toner conveying member in the contact developing method using a non-magnetic one-component toner, in particular, the items relating to the surface characteristics. Therefore, a high-quality image can always be formed stably.

[Brief description of the drawings]

FIG. 1 is a diagram of an apparatus 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 the embodiment. 1: electrostatic latent image carrier 2: toner transport member 3: toner layer thickness regulating member 4: toner supply member, 5: stirring blade 6: toner, 7: toner tank 10: filter, 11: suction cell 12: toner Suction port, 13: Coulomb meter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Motoi Orihara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Koji 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Tomoe Hagiwara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Kazuo Nojima, 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-62-223771 (JP, A) JP-A-62-27751 (JP, A)

Claims (1)

(57) [Claims] 1. An electrostatic latent image formed on a toner conveying member in a thin layer of toner charged to a desired polarity by friction with the member, and contacting or adjacent to the member. In the method of developing an electrostatic latent image by contacting the latent image surface of a holding member, a toner transport member includes a first coating layer made of an elastic material on a support and a flexible resin and conductive fine particles formed thereon. A colored resin particle as a base toner, and fine particles capable of being charged to a polarity opposite to that of the base toner due to friction with the toner conveying member. A method for developing an electrostatic latent image, characterized by using a mixed system.