JPH08262794A - Electrophotographic toner and image forming method - Google Patents

Abstract

PURPOSE: To make it possible to suppress the occurrence of image defects and image flow of an amorphous silicon photoreceptor by using a binder resin specified in the content of residual volatile matter to a specific value. CONSTITUTION: The binder resin having the content of the residual volatile matter to <=0.02wt.% is used. The residual volatile matter refers to the material removed from the binder resin when the binder resin is heated and rested for two hours at >=105 deg.C under ordinary pressure. The residual volatile matter in the binder resin is <=0.02wt.%, more preferably <=0.008wt.% and further preferably <=0.005wt.%. The image defects and image flow are liable to arise if the residual volatile matter exceeds 0.02wt.%. Styrenes, such as polystyrene and polyvinyl toluene, and single polymers of their substitutes, etc., are usable alone or in combinations of >=2 kinds as the binder resin. Commercially marketed resins or resins synthesized by a suspension polymn., method, etc., are usable by confining their residual volatile matter to <=0.02wt.% by drying by heating, reduced pressure drying, drying by heating under reduced pressure, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for electrophotography and a method for developing electrophotography, and more specifically, it applies electrophotography such as an electrostatic copying machine or a laser beam printer using an amorphous silicon photoconductor. The present invention relates to an electrophotographic toner used in an image forming apparatus and an electrophotographic developing method.

[0002]

2. Description of the Related Art The electrophotographic method generally uses a photoconductive material to form an electric latent image on a photoconductor by various means, and then uses the electrophotographic toner with an electrophotographic toner. After being developed and visualized as a toner image, the toner image is transferred from the surface of the photoreceptor to a transfer material such as paper, and then heated,
An image forming method in which a copy is obtained by fixing with pressure, heat and pressure, or solvent vapor.

As the electrophotographic toner used in the above image formation, a mixture of a fixing resin containing a colorant such as carbon black and a charge control agent is melted and kneaded, and then a predetermined particle size is obtained. Granulated products are used.

Amorphous silicon photoconductors, selenium photoconductors, organic photoconductors, etc. are used as the electrophotographic photoconductors used for the image formation. Of these,
Amorphous silicon photoconductor is a photoconductor having an amorphous silicon layer on the surface of an aluminum drum, which has high photosensitivity and is made of a pollution-free material, and is a photoconductor having excellent reliability and durability. . However, there is a problem that pinholes are easily generated on the surface of the amorphous silicon layer in the manufacturing process. If pinholes are present on the surface of the amorphous silicon layer, image defects such as black spots and white spots occur in the output image, and the image quality is significantly impaired.

It is considered that the above-mentioned image defects derived from pinholes on the surface occur through the following processes.
First, in the step of visualizing an image, fine particles such as a fluidizing agent in a developer and fine particles of a carrier are embedded in pinholes of a photosensitive layer to form protrusions on the surface of the photosensitive layer. As the visualization process is repeated, the components in the toner adhere to the protrusions. Since the adhered matter is soft, for example, a low molecular weight organic substance contained in the toner, if the adhered quantity is increased, the adhered matter is easily extended to the surface of the photosensitive layer by the cleaning blade of the copying machine or the like. Whether the deposit has polarity or not, when the photoconductor is exposed after being charged, it is between the surface potential of the adhered part after exposure and the surface potential of the non-adhered part in the vicinity. When a potential difference occurs and it is developed with toner, the adhered portion causes an image defect.

Further, in the amorphous silicon photoconductor,
When the humidity in the environment is high, SiO existing on the surface of the photoconductor
Since water is bound to the surface of the photoreceptor and the resistance of the surface of the photoreceptor is reduced, image deletion easily occurs. Similarly, S existing on the surface of the photoconductor
When iO is combined with a polar component in the toner, it may cause image deletion.

In order to prevent such image defects and image deletion, a surface treating agent having a function of polishing the surface of the photoconductor is usually added to the electrophotographic toner used together with the amorphous silicon photoconductor. ing.

However, if the surface treatment agent is added too much, the amorphous silicon film on the surface of the photoconductor is excessively polished, resulting in a problem that the durability of the photoconductor is deteriorated. On the other hand, if the addition amount is insufficient, the effect of preventing the occurrence of image defects and image deletion cannot be sufficiently obtained, and conventionally, the addition amount of the surface treatment agent had to be adjusted very delicately.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and provides a toner capable of suppressing the occurrence of image defects and image deletion on an amorphous silicon photoconductor. With the goal.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present inventors have found that the components in the toner adhering to the surface of the photoconductor, which are the root cause of the image defects and image deletion, are By finding out that it is the residual volatiles in the binder resin used, and by defining the content of the residual volatiles in the binder resin used, it was found that the above problems can be effectively solved, The invention was completed.

That is, the electrophotographic toner of the present invention uses a binder resin having a residual volatile content of 0.02% by weight or less. This achieves the above object.

Further, the image forming method of the present invention uses an amorphous silicon photoconductor and the above toner. This achieves the above object.

Furthermore, the present invention relates to a binder resin for toner having a residual volatile content of 0.02% by weight or less.

The present invention will be described in more detail below.

In the present invention, the "residual volatile matter" means a substance removed from the binder resin when the binder resin is left under heating at 105 ° C. or higher for 2 hours under normal pressure.

The binder resin used in the toner of the present invention has a residual volatile content in the resin of 0.02% by weight or less, preferably 0.008% by weight or less, and further preferably
It is 0.005% by weight or less. If the residual volatile content exceeds 0.02% by weight, image defects and image deletion are likely to occur.

As such a resin, any polymer known to those skilled in the art as a binder resin for an electrophotographic toner can be used as long as the residual volatile content in the resin is 0.02% by weight or less. , Polystyrene having a residual volatile content in the resin of not more than 0.02% by weight, homopolymers of styrene such as poly-p-chlorostyrene and polyvinyltoluene, and substituted products thereof; styrene-p-chlorostyrene copolymer, styrene- Vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer , Styrene-
Styrene-based copolymers such as vinyl methyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers;
Polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane resin, polyamide resin, furan resin, epoxy resin, xylene resin, Polyvinyl butyral resin, terpene resin, coumarone indene resin,
Petroleum resin, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer,
Ionomer resins, styrene-butadiene copolymers, styrene-isoprene resins, linear saturated polyesters and the like can be used. These may be used alone or in combination of two or more.

Usually, a commercially available resin or a resin synthesized by a suspension polymerization method or the like is 0.1 to 0.5% by weight.
It has some residual volatiles. Such a resin can also have a residual volatile content of 0.02% by weight or less by heat drying, vacuum drying, heat vacuum drying, etc., and can be used in the toner of the present invention.

When a toner is obtained by a kneading and pulverizing method using the above-mentioned conventional resin, the toner obtained by melting and kneading a mixture containing a conventional resin, a colorant and the like under predetermined melting and kneading conditions. The residual volatile content therein may be 0.02 wt% or less based on the resin contained. Suitable melting / kneading conditions vary depending on the kneading machine used, and for example, when a twin-screw extrusion kneading machine PCM30 (made by Ikegai) is used as a kneading device, the processing speed is 2 to 12 kg / h, preferably 3 to 10 kg / h. More preferably 4-8k
g / h. The shaft rotation speed is 100 to 300 rpm, preferably 140 to 280 rpm, and more preferably 200.
~ 280 rpm. The protrusion temperature of the toner component kneaded product is 140 ° C to 250 ° C, preferably 150 ° C to 20 ° C.
The temperature is 0 ° C., particularly preferably 150 to 180 ° C., but not limited thereto.

The kneading machine is not particularly limited as long as the same conditions as the melting and kneading conditions can be achieved, but for example, 2
The present roll kneading machine, the three-roll kneading machine, the scale-up machine of the PCM30 and the like can be used.

The toner of the present invention contains a binder resin as an essential component, and may further contain a compounding agent such as a colorant, a charge control agent, a release agent and a magnetic powder, if necessary.

The following are preferably used as the colorant.

Black pigments: carbon black such as furnace black, channel black, thermal, gas black, oil black, acetylene black, lamp black, aniline black; white pigments: zinc white, titanium oxide, antimony white, zinc sulfide; red pigments : Red iron oxide, cadmium red, red lead, mercury sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; orange color Pigment: Red lead yellow lead, molybdenum orange, permanent orange GTR, pyrazolo orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, Andrenslen Brilliant Orange GK; Yellow pigments: yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, Naples yellow, naphthol yellow S, hunter yellow G, hunter yellow 10G, benzidine. Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; Green Pigment: Chrome Green, Chromium Oxide, Pigment Green B, Malachite Green Lake, Fanal Yellow Green G; Blue Pigment: Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partial Chloride, Fast Sky Blue, Indanthrene Blue BC; Purple Pigment: Manganese Purple, Fast Bio B, methyl violet lake; extender pigment: barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white; conductive pigment: conductive carbon book, aluminum powder; photoconductive pigment: zinc oxide, selenium , Cadmium sulfide, cadmium selenide.

The colorant may be used in an amount of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the binder resin.

As the charge control agent, a positive charge control agent or a negative charge control agent can be used depending on the polarity of the toner.

Examples of the positive charge control agent include organic compounds having a basic nitrogen atom, such as basic dyes, aminopyridines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and fillers surface-treated with these compounds. Can be used.

As the negative charge control agent, a compound containing a carboxy group (for example, a metal chelate of alkylsalicylic acid), a metal complex salt dye, a fatty acid soap, a metal salt of naphthenic acid and the like can be used.

The charge control agent is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.
It may be used in a proportion of parts by weight.

Examples of the releasing agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Among them, the weight average molecular weight is 1000-
About 10,000 aliphatic hydrocarbons are preferred. Specifically, one kind or a combination of two or more kinds of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms is preferable.

The release agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.

As the magnetic powder, various ferrites such as ferric tetroxide (Fe ₃ O ₄ ) and ferric sesquioxide (γ-Fe _2).
O ₃ ), iron oxide zinc (ZnFe ₂ O ₄ ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), iron cadmium oxide (CdFe _2).
O ₄ ), iron gadolinium oxide (GdFe ₅ O ₄ ), iron oxide copper (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), neodymium iron oxide (NdFeO ₃ ), barium iron oxide (Ba)
Fe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂ O ₄ ),
Iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (L
aFeO ₃ ), iron powder, cobalt powder, nickel powder and the like.

The toner of the present invention can be prepared by the following method.

The toner of the present invention can be manufactured by a well-known method for manufacturing toner. For example, the components constituting the toner are homogeneously pre-kneaded by a dry blender, a Henschel mixer, a ball mill or the like to obtain a mixture.
The obtained mixture is uniformly melt-kneaded by using a kneading device such as a Panbury mixer, a roll, a uniaxial or biaxial extrusion kneader and the like. The obtained kneaded product may be cooled, pulverized, and classified as necessary to produce a raw toner powder.
Raw toner powder can also be produced by a suspension polymerization method or the like. The toner has a volume average particle diameter (median diameter by Coulter counter) of 5 to 25 μm.
It is preferably 5 to 15 μm, and particularly preferably 7 to 12 μm.

The above toner raw powder is made into a toner by adding an external additive, if necessary. The external additive can improve the fluidity and chargeability of the toner.

As the external additive, various conventionally known materials such as inorganic fine particles, resin fine particles and metal stearates can be used. In particular, silica-based surface treatment agents containing hydrophobic or hydrophilic silica fine particles, for example, hydrophobic or hydrophilic silica fine particles such as ultrafine particulate anhydrous silica and colloidal silica are preferably used. The external additive is added in an amount of 0.1 to 2.0% by weight based on the total weight of the toner, that is, the total weight of the raw toner powder and the external additive.

The toner of the present invention can be mixed with a magnetic carrier such as ferrite or iron powder to be used as a two-component developer in an image forming apparatus.

As the magnetic carrier, a ferrite type magnetic carrier is preferably used. Fe and Cu,
Soft ferrite containing at least one, preferably two or more metal components selected from the group consisting of Mg, Mn, and Ni can be suitably used. For example, particles of sintered ferrite of copper-zinc-magnesium ferrite, especially spherical particles, can be used as soft ferrites. The surface of the magnetic carrier may not be coated, but it is preferable that it is coated with a silicone resin, a fluorine resin, an epoxy resin, an amino resin, a urethane resin or the like. The particle size of the magnetic carrier is 30 to 200
It is desirable that the thickness is in the range of 50 μm, particularly 50 to 150 μm. The saturation magnetization of the carrier is preferably 30 to 70 emu / g, particularly 45 to 65 emu / g.

The mixing ratio of the magnetic carrier and the toner is generally 98: 2 to 90:10 by weight, and particularly 97: 3 to 9.
A weight ratio of 4: 6 is preferred.

[0039]

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited thereto.

In the following examples, all parts are parts by weight unless otherwise specified.

(Preparation Example 1 of Binder Resin) Styrene 8
A mixture of 0 parts by weight, 20 parts by weight of n-butyl methacrylate, and 1 part by weight of 2,2-azobisisobutyronitrile was added to 400 parts by weight of water containing 10 parts by weight of tricalcium phosphate under a nitrogen stream. Suspension polymerization was carried out at 65 ° C. for 10 hours while stirring using a stirrer. The obtained polymer was recovered, washed with dilute hydrochloric acid, immersed in methanol, and vacuum dried at 60 ° C. for 24 hours to give a styrene-acryl copolymer (GPC) having a residual volatile content of 0.005% by weight. Weight average molecular weight of 229000)
I got

(Preparation Example 2 of Binder Resin) Styrene 8
A mixture of 0 parts by weight, 15 parts by weight of n-butyl methacrylate, 5 parts by weight of methacrylic acid, and 3 parts by weight of 2,2-azobisisobutyronitrile was added to 300 parts by weight of toluene, and the mixture was further heated at 70 ° C. for 6 hours. 2 up to 90 ℃
Solution polymerization was carried out for a period of time. The resulting polymer was reprecipitated in methanol and then dried at 100 ° C. for 5 hours.
In the same manner as in Preparation Example 1, a styrene-acrylic copolymer having a residual volatile content of 0.01% by weight (weight average molecular weight 96500 by GPC method) was obtained.

(Preparation Example 3 of Binder Resin) Styrene 7
Suspension polymerization was carried out in the same manner as in Preparation Example 1 using 0 parts by weight, 15 parts by weight of 2-ethylhexyl methacrylate, 15 parts by weight of methyl methacrylate, and 1.5 parts by weight of benzoyl peroxide. The obtained polymer was recovered, washed with dilute hydrochloric acid, and vacuum dried at 60 ° C. for 24 hours to give a styrene-acryl copolymer having a residual volatile content of 0.02% by weight (weight average molecular weight 127,000 by GPC method). ) Got.

(Preparation Example 4 of Binder Resin) Styrene 8
Suspension polymerization was carried out at 70 ° C. for 6 hours using 0 parts by weight, 20 parts by weight of n-butyl methacrylate, and 0.8 parts by weight of 2,2-azobisisobutyronitrile. Further, a styrene-acryl copolymer having a residual volatile content of 1.0% by weight (weight average molecular weight of 367 by GPC method) was prepared in the same manner as in Preparation Example 1 except that the polymer was not immersed in methanol.
000) was obtained.

(Preparation Example 5 of Binder Resin) A residual volatile content of 0.5 wt% was obtained in the same manner as in Preparation Example 2 except that the obtained polymer was not reprecipitated in methanol and dried at 100 ° C. for 5 hours. % Styrene-acrylic copolymer (GP
A weight average molecular weight of 95,000 was obtained by Method C.

(Preparation Example 6 of Binder Resin) A styrene-acryl copolymer having a residual volatile content of 0.6% by weight was prepared in the same manner as in Preparation Example 3 except that the obtained polymer was vacuum dried at room temperature for 24 hours. Polymer (weight average molecular weight by GPC method 1
25000) was obtained.

(Example 1) 100 parts by weight of the styrene-acrylic copolymer of Preparation Example 1 as a binder resin, carbon black as a colorant (primary particle size 14 n before melt-kneading)
m, a specific surface area of 300 cm ² / g), 8 parts by weight, 2 parts by weight of a low molecular weight polyolefin as a release agent, and 1 part by weight of TRH (Hodogaya Chemical Co., Ltd.), which is a metal complex salt of an azo dye as a charge control agent. 6 kg of this mixture was put into a twin-screw extrusion kneader (model number "PCM30" manufactured by Ikegai Seisakusho Co., Ltd.), and the heater temperature was adjusted so that the shaft rotation speed was 250 rpm and the protrusion temperature of the kneaded product was 180 ° C. After melt-kneading, the mixture was cooled, pulverized and classified using a jet pulverizer (manufactured by Nippon Pneumatic Co., Ltd., model number "ID-2"), and raw toner powder having an average particle diameter of 12 µm was obtained.

The obtained toner raw powder has an average particle size of 0.0
0.3% by weight of 15 μm silica fine powder and 0.1% by weight of alumina fine powder having an average particle size of 0.013 μm were externally added and mixed for 2 minutes with a Henschel mixer to obtain a toner.

(Example 2) A toner was obtained in the same manner as in Example 1 except that the resin of Example 1 was changed to the resin of Preparation Example 2.

(Example 3) A toner was obtained in the same manner as in Example 1 except that the resin of Example 1 was changed to the resin of Preparation Example 3 and the alumina fine particles were changed to resin fine powder.

(Comparative Example 1) The resin of Example 1 was added to the resin of Preparation Example 4 and the colorant was used to have a primary particle size of 14 nm and a specific surface area of 200 c.
It changed to m ² / g carbon black, and except for not using the non-treated fine silica powder in the same manner as in Example 1 to obtain a toner.

(Comparative Example 2) The resin of Example 1 was added to the resin of Preparation Example 5 and a colorant was added to have a primary particle size of 20 nm and a specific surface area of 200 c.
m ² / g of carbon black, and 0.15% by weight of silica fine powder and 0.05% by weight of alumina fine powder
A toner was obtained in the same manner as in Example 1 except that it was used.

(Comparative Example 3) The resin of Example 3 was used as the resin of Preparation Example 6, and the colorant was used as the primary particle diameter 27 nm and specific surface area 1
A toner was obtained in the same manner as in Example 3, except that the carbon black was changed to 00 cm ² / g.

(Evaluation of Toner) The toners obtained in the above Examples and Comparative Examples were evaluated for the following items. Table 1 shows the evaluation results. The toners were evaluated by mixing the toners obtained in the above Examples and Comparative Examples with a ferrite carrier having an average particle size of 100 μm to obtain a two-component developer having a toner concentration of 3.5%, which was used as an electrophotographic copying machine. (Sanda Kogyo Co., Ltd., model number “DC-6090”, heating pressure roll fixing method, using amorphous silicon photosensitive drum) was used for evaluation. The evaluation items and evaluation methods are as follows.

(A) Image Defect A predetermined original was continuously copied, the number of copies in which an image defect occurred was recorded, and evaluated according to the following criteria: ◯: No image defect even in 30,000 copies or more Δ: 20,000 copies or more Image defects occur on less than 30,000 sheets x: Image defects occur on less than 20,000 copies.

(B) Image deletion In continuous copying in the above evaluation item (a), the number of copies in which an image deletion phenomenon occurred was recorded and evaluated according to the following criteria: ◯: No image deletion after 30,000 copies or more Δ: Image deletion occurs in 20,000 copies or more and less than 30,000 copies x: Image deletion occurs in less than 20,000 copies.

(C) Image quality In continuous copying in the above evaluation item (a), the image density of the copied image obtained was measured with a reflection densitometer, and when the image density became lower than 1.30 for the first time. The number of printed sheets was recorded and evaluated according to the following criteria: ◯: No reduction in image density even after 30,000 copies or more Δ: Reduction in image density after 20,000 copies or more and less than 30,000 copies x: Reduction in image density after less than 20,000 copies

[0058]

[Table 1]

As can be seen from Table 1, the toners of Examples 1 to 3 using the binder resin having a residual volatile content of 0.02% by weight or less have a residual volatile content of 0. Image defects and image deletion were less likely to occur than the toners of Comparative Examples 1 to 3 using the binder resin in an amount of more than 0.02% by weight.

[0060]

By using the electrophotographic toner of the present invention, image defects are less likely to occur in electrophotographic image formation using an amorphous silicon photoreceptor, and a high quality copied image can be stably obtained. Further, since it becomes unnecessary to finely adjust the amount of the surface treatment agent added externally during the toner production, the toner production can be made efficient and stable.

Claims (3)

[Claims] 1. A toner for electrophotography, comprising a binder resin having a residual volatile content of 0.02% by weight or less. 2. An image forming method using the toner according to claim 1 and an amorphous silicon photoconductor. 3. A binder resin for use in an electrophotographic toner, which has a residual volatile content of 0.02% by weight or less.