JPH07120073B2 - Toner for electrostatic image development - Google Patents

Description

The present invention relates to a toner for developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing, etc., and is particularly suitable for heat roller fixing. It relates to toner.

[Prior Art] Conventionally, as electrophotographic methods, many methods are known as described in US Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748. Generally, a photoconductive substance is used to form an electrical latent image on a photoconductor by various means, and then the latent image is developed with toner, and a transfer material such as paper is used as necessary. After the toner image is transferred to, the toner image is fixed by heating, pressure or solvent vapor to obtain a copy.

Various methods and devices have been developed for the final step of fixing the toner image on a sheet such as paper. The most popular method at present is a pressure heating method using a heating roller.

The pressure-bonding heating method using a heating roller is applied to the surface of a heating roller whose surface is formed of a material having releasability for toner.
The fixing is performed by passing the toner image surface of the sheet to be fixed under pressure under contact. In this method, since the surface of the heat roller and the toner image on the sheet to be fixed are brought into contact with each other under pressure, the thermal efficiency at the time of fusing the toner image on the sheet to be fixed is extremely good, and rapid fixing is possible. It is possible and very effective in a high speed electrophotographic copying machine. However, in the above method, since the heat roller surface and the toner image are in contact with each other in a molten state under pressure, a part of the toner image adheres to and transfers to the fixing roller surface, and re-transfers to the next sheet to be fixed. A so-called offset phenomenon may occur and the sheet to be fixed may be soiled. Preventing toner from adhering to the surface of the heat fixing roller is one of the essential conditions of the heat roller fixing method.

As described in JP-B-51-23354, such an offset phenomenon is likely to occur when a low molecular weight resin is used. Therefore, it is considered that the offset phenomenon can be prevented by using a crosslinked resin as described in the publication, but even if the degree of crosslinking is simply increased,
There are many problems because the fixing temperature becomes high, and in the case of a magnetic toner, the fixing temperature rises and the offset resistance deteriorates.

Further, for the purpose of not adhering the toner to the surface of the fixing roller, for example, the roller surface is formed of a material excellent in releasability from the toner, such as silicon rubber or fluorine resin,
Further, in order to prevent offset and prevent fatigue of the roller surface, the roller surface is coated with a thin film of a liquid having a good releasability such as silicone oil. However, this method is extremely effective in preventing toner offset, but there is a problem that the offset preventing liquid evaporates by heating, and a device for supplying the offset preventing liquid is required. It has problems such as complexity. Therefore, the direction of preventing the offset by supplying the offset preventing liquid is not preferable, and the present situation is that the development of a toner having a wide fixing temperature range and high offset resistance is desired.

Further, as a matter of course, the toner is required to have excellent anti-blocking property, developing property, transfer property, cleaning property, etc. in addition to the fixing property, but the conventional toner has the following defects. Had one or more. That is, most toners that are easily melted at a relatively low temperature by heating are likely to cake or aggregate during storage or in a copying machine. Many toners have poor triboelectric and flow properties due to environmental humidity changes. Further, with many toners, the density of the obtained image changes due to the collision between toner particles and carrier particles due to repeated development due to continuous use and mutual deterioration of the toner, carrier particles and photosensitive plate due to contact between them and the surface of the photosensitive plate. Alternatively, the background density is increased and the quality of the copy is degraded. With more toner, when the amount of toner attached to the surface of the photosensitive plate having a latent image is increased to increase the density of the copied image, the background density is usually increased and a so-called fog phenomenon occurs. Therefore, there is a demand for a toner which has various toner characteristics and is suitable for the heat roller fixing method.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a toner having excellent physical and chemical properties, which overcomes the above-mentioned defects of the toner.

An object of the present invention is to provide a toner for fixing on a heat roller, which has good low-temperature fixability and offset resistance.

Further, an object of the present invention is to provide a toner for fixing on a heat roller, which has a good chargeability and always shows a stable chargeability during use, and which gives a clear and fog-free image.

Further, an object of the present invention is to provide a toner for fixing on a heat roller, which has excellent fluidity, does not cause aggregation, and has excellent impact resistance.

Further, an object of the present invention is to provide a toner for fixing on a heat roller, which has less adhesion to the toner holding member or the surface of the photoconductor.

Further, an object of the present invention is to provide a magnetic toner which, when used as a magnetic developer, exhibits good and uniform magnetism and can be fixed on a heat roller.

[Means and Actions for Solving Problems] The present invention provides a vinyl-based polymer A polymerized by using only an organic peroxide-based initiator as a polymerization initiator, and an azo-based initiator as a polymerization initiator. A toner for developing an electrostatic charge image containing a binder resin containing a vinyl polymer B polymerized by using only the above and a colorant, wherein the melt index of the vinyl polymer A (hereinafter referred to as MI and Is smaller than the melt index of the vinyl polymer B, and relates to an electrostatic charge image developing toner.

That is, in order to solve the above-mentioned problems, the present inventors have examined the branched structure and the fine structure of the binder resin which is the main component of the toner, and found that the same monomer species, monomer composition, molecular weight, It has been found that the fine structure is different depending on the kind of the polymerization initiator, regardless of the amount of the crosslinking agent added, and the effect on the toner performance is extremely large.

That is, when an organic peroxide was used as an initiator and the fine structure was analyzed, the following characteristics were obtained. In addition to the ladder-shaped cross-linking part due to bifunctional vinyl monomer, etc., it is considered that the fine structure contains cross-linking due to recombination between radicals generated by hydrogen abstraction from the main chain. It was found that a large amount of high molecular weight components were contained. This makes it more elastic and mechanically stronger than polymers with other initiators of the same monomer type, monomer composition, and molecular weight, and when used as a toner component, it has better offset resistance than that by simple crosslinking with a crosslinking agent. It also has good durability and stability for long-term use.

When an azo-based initiator is used, the polymer has a low melt viscosity with respect to the molecular weight and a high fluidity at the time of melting. It is considered that this is because with the azo-based initiating radical, hydrogen abstraction from the main chain is unlikely to occur, and there is no crosslinking due to the initiator radical. For this reason, it is possible to form a resin component that easily melts on the transfer material and forms a toner that adheres well to the transfer material.

However, if only a polymer using an organic peroxide initiator or a polymer using an azo-based initiator is used alone, all of the above-mentioned problems are irrespective of MI, molecular weight, and molecular weight distribution. I could not be satisfied.

Further, even if two or more polymers obtained by using an organic peroxide initiator are used, they have a drawback in fluidity at the time of melting, inferior pulverizability and a problem in productivity.

Further, when two or more polymers based on an azo-based initiator are used,
Image contamination is apt to occur due to stains on the fixing roller, and increasing the molecular weight in order to prevent it has resulted in poor fixability.

Therefore, it has been found that the above problems as a toner can be solved by mixing and using different polymers which retain the characteristic effect depending on each polymerization initiation species and by using the respective functions in combination.

That is, the object of the present invention is achieved by using the respective polymers of the organic peroxide initiator and the azo initiator in combination.

Furthermore, when the polymer obtained using an organic peroxide initiator as the polymerization initiator is A and the polymer B obtained using an azo initiator, the MI of the polymer is It is good that it is a combination B. As a result, it was found that the above-mentioned properties of the respective polymerization initiators are exerted as the polymer, and the above-mentioned problems are solved as the toner.

Here, setting the MI of the polymers A and B to polymer A> polymer B does not fully utilize the features imparted to each polymer found by the present invention, and the problem is not solved. That is, the ultra-high molecular weight contained in the polymer A and the crosslinking in the fine structure by the organic peroxide-based initiator are more effective than when the polymer component has an MI smaller than that of the polymer B. The characteristics that the melt viscosity is low and the melt fluidity is high with respect to the molecular weight of the polymer B due to the initiator are
It is effective when MI is larger than.

The organic peroxide initiator used to obtain the polymer A in the present invention has an -OO bond, and examples thereof include isobutyl peroxide, benzoyl peroxide, lauroyl peroxide, and 2,4-dichlorobenzoyl peroxide. , O-methylbenzoyl peroxide, bis-
3,5,5-Trimethylhexanoyl peroxide, p-
Diacyl peroxides such as chlorobenzoyl peroxide; cumene hydroperoxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, 2,4,4-trimethylpentyl-2
-Hydroperoxides such as hydroperoxide; dicumyl peroxide, 2,5-dimethyl-2,5-di- (t-butylperoxide) hexane, t-butylcumylperoxide, di-t-butylperoxide Dialkyl peroxides such as 1,3-bis- (t-butylperoxyisopropyl) benzene; 1,1-di-t-butylperoxycyclohexane, 2,2-di-
Peroxyketals such as (t-butylperoxy) butane; alkyl peresters such as t-butylperoxyisobutyrate, t-butylperoxyacetate and t-butylperoxybenzoate, diisopropylperoxydicarbonate, di- Percarbonate such as 3-methoxybutyl peroxydicarbonate can be used.

Examples of the azo-based initiator used for obtaining the polymer B include-
C-N = a compound having an N-bond, for example, R-N =
'Represented by, R, R' N-R is _{CH 3, CH (CH 3)} 2, CH (CH 3)
(CN), C (CH ₃ ) ₂ (CN), CH (CH ₃ ) (C ₆ H ₅ ), CH (C
₆ H ₅ ) ₂ , C (CH ₃ ) ₂ (CO ₂ CH ₃ ), C (CH ₃ ) (i-butyl) (C
N) and so on. Here, R = R 'and R ≠ R' may be used.

As the method for producing the polymer of the present invention, it can be synthesized by using a known polymerization means such as solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization and the like. As a process for synthesizing the polymer for binder, solution polymerization, suspension polymerization, and emulsion polymerization are preferable in controlling the degree of polymerization, molecular weight, and molecular weight distribution. The solution polymerization method is more preferable. This is because, in the emulsion polymerization method or suspension polymerization method, a monomer is emulsified or dispersed in water which is a continuous phase by using an additive such as a surfactant or a dispersion stabilizer, and then a polymer is prepared by adding a salt or the like. Thus, the obtained polymer contains the hydrophilic additive as described above. When such a hydrophilic additive is present in the toner, the toner often absorbs moisture under high humidity to cause a decrease in specific resistance, which often adversely affects the electrical properties of the toner. Further, in the bulk polymerization method, when the degree of polymerization increases, problems such as gel effect occur, and it is very difficult to control the polymerization reaction.

To obtain the polymer in the toner of the present invention, the following monomers can be applied as the monomer.

Styrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert. Styrene and derivatives thereof such as -butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene; ethylene, propylene, Ethylene unsaturated monoolefins such as butylene and isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid Methyl, ethyl methacrylate, propyl methacrylate, methacrylic acid-n-bu Α-methylene aliphatic monoesters such as tyl, isobutyl methacrylate, -n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate. Carboxylic acid esters; methyl acrylate, ethyl acrylate, -n-butyl acrylate, isobutyl acrylate, propyl acrylate, -n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, Acrylic acid esters such as 2-chloroethyl acrylate and phenyl acrylate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl methyl ketone, Vinyl ketones such as nylhexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone; vinylnaphthalenes; acrylonitrile, methacrylonitrile, acrylamide There are vinyl monomers such as acrylic acid or methacrylic acid derivatives.

At the time of polymerization, the following crosslinking agent is present for polymerization,
It may be a cross-linked polymer.

Divinylbenzene, divinylnaphthalene, divinyl ether, divinyl sulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate , 1,6-
Hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4-methacryloxydiethoxyphenyl) propane, 2,2'-bis (4-acryloxy) Diethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dibromoneopentyl glycol dimethacrylate, allyl phthalate, 1,2-propylene glycol, 1,3
-General cross-linking agents such as butanediol can be used as appropriate.

In the present invention, the MI of the polymer A is 0.10 to 1.2 g / 10 minutes, preferably 0.30 to 1.00 g / 10 minutes. The MI of the polymer B is 1.3 to 10.0 g / 10 minutes, preferably 1.4 to 5.0 g.
/ 10 minutes.

Melt index here is the flow test method of Japanese Industrial Standards using the device JIS K 7210 described, 125 ℃, load 2160g, orifice inner diameter 2.0955 ± 0.
The measurement was carried out with a length of 0051 mm and a length of 8.000 ± 0.025 mm.

In the present invention, the mixing weight ratio of the polymer A and the polymer B is preferably A / B = 0.1 to 2.0, more preferably A / B = 0.
25-1.5 is good. If the amount of the polymer B is too much with respect to the amount of the polymer A, the offset to the roller at the time of fixing and the releasability of the transfer paper are poor, and the cohesiveness is increased. On the other hand, if the amount is too small, the minimum fixing temperature rises, and at the same time, the flow characteristics during heating tend to be inferior and sufficient fixing cannot be achieved. Tends to be difficult to effectively pulverize.

Further, 0.1 to 10% by weight (more preferably 0.2 to 5% by weight) of an ethylene-based olefin homopolymer or ethylene-based olefin copolymer having a melt viscosity at about 150 ° C. of 10 to 10 ⁶ cps should be added to the toner. As a result, the dispersibility and compatibility of the pigment and the magnetic fine particles with respect to the toner are improved, and the adverse effects on the surface of the photoconductor, the kneading member, etc. are reduced. Here, to be applied as an ethylene-based olefin homopolymer or ethylene-based olefin copolymer,
Polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-
There are ethyl acrylate copolymers and the like, and those containing 50 mol% to 100 mol% (more preferably 60 mol% to 100 mol%) of an olefin monomer in the above copolymer are preferable.

The Brookfield method was used to measure the melt viscosity, and here, a B-type viscometer equipped with a small amount of sample adapter was used.

In the toner of the present invention, any suitable pigment or dye is used as a colorant. For example, carbon black,
There are known dyes and pigments such as iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow.

Further, when the toner of the present invention is a magnetic toner, it may also serve as a colorant, but iron, cobalt, nickel, such as ferromagnetic elements and alloys containing these, compounds such as magnetite, hematite and ferrite, Magnetic powders conventionally known as magnetic materials such as alloys and compounds of manganese and other ferromagnetic alloys may be contained. Carbon black, nigrosine, metal complex salts, colloidal silica powder, fluororesin powder, etc. may be added for the purpose of charge control, prevention of aggregation and the like.

The toner of the present invention can be applied to various developing methods. For example,
Magnetic brush developing method, cascade developing method, US Patent No.
3,909,258, a method using a conductive magnetic toner, JP-A-53-31136, a method using a high resistance magnetic toner, JP-A-54-42141, JP-A-55-1.
There are a method described in Japanese Patent No. 8656, a fur brush developing method, a powder cloud method, an impression method and the like.

A toner image formed on a fixing sheet such as paper using the toner according to the present invention does not cause a toner offset phenomenon even when a fixing roller that does not supply an offset preventing liquid to the surface thereof is used. You can freeze the fixing with a heat roller. The surface of the fixing roller is, for example, Teflon (manufactured by DuPont) or Fluon (ICI
(Manufactured by K.K.) and Keru F (manufactured by 3M) or the like, or fluorine-based resin, silicon rubber, or those having a smooth surface formed of silicon resin, and in some cases, those having a metal surface can be used.

[Examples] Production examples of polymers are shown below.

Production Example I 40 parts by weight of toluene was placed in a three-necked flask, and 85 parts by weight of styrene, 45 parts by weight of butyl acrylate, and 0.5 parts by weight of divinylbenzene were added, the gas phase was replaced with nitrogen gas, and the temperature was kept at 80 ° C. Benzoyl peroxide 0.
What melt | dissolved 5 weight part was dripped using the dropping funnel which replaced nitrogen gas for 30 minutes, and also stirred at 80 degreeC for 8 hours. Next, 5 parts by weight of a toluene solution containing 0.3 part by weight of benzoyl peroxide was added dropwise, the temperature was further raised to 90 ° C., and the temperature was maintained for 3 hours to complete the polymerization. After cooling, the polymer was precipitated in a large amount of methanol, the precipitate was separated, dried at 60 ° C. and recovered. The MI of this polymer is 0.70g / 10 minutes, and _W is
It was 420,000.

Production Example II 80 parts by weight of styrene as a monomer, methyl methacrylate
The same procedure as in Preparation Example I was repeated except that 20 parts by weight of divinylbenzene (0.6 parts by weight) and t-butylperoxybenzoate (0.3 parts by weight) were used. The MI of this polymer is 1.0 g / 1
At 0 minutes, _W was 352,000.

The production example of the polymer B is shown below.

Production Example III 40 parts by weight of toluene was placed in a three-necked flask, 80 parts by weight of styrene, 20 parts by weight of butyl acrylate, and 0.5 parts by weight of divinylbenzene were added, and the gas phase was replaced with nitrogen gas, and then maintained at 80 ° C., toluene. What melt | dissolved azobisisobutyronitrile 1.0 weight part in 10 weight parts is dripped using the dropping funnel which replaced with nitrogen gas for 30 minutes, and also for 5 hours.
Stirred at 80 ° C. Then azobisisobutyronitrile 0.
Add 5 parts by weight of a toluene solution containing 5 parts by weight, and add 9 parts by weight.
The temperature was raised to 0 ° C., and the temperature was maintained for 2 hours to complete the polymerization. After cooling, the polymer was precipitated in a large amount of methanol, the precipitate was separated, dried at 60 ° C. and recovered. MI of this polymer
Was 2.1 g / 10 minutes and _W was 280,000.

Production Example IV 75 parts by weight of styrene as a monomer, 25 parts by weight of 2-ethylhexyl acrylate, 0.3 parts by weight of divinylbenzene,
The same procedure as in Preparation Example III was repeated except that 3 parts by weight of azobisisobutyronitrile was used. The MI of this polymer is 4.8
g / 10 minutes, _W was 160,000.

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

Example 1 50 parts by weight of the polymer synthesized in Production Example I, 50 parts by weight of the polymer synthesized in Production Example III, 3 parts by weight of nigrosine, 60 parts by weight of magnetic powder (Fe ₃ O _{4 having} an average particle size of 0.3 μm), and Polyethylene 2
The parts by weight were kneaded for 30 minutes at a temperature of 150 ° C. using a roll mill. After cooling, the powder was finely pulverized with an air jet type pulverizer, and particles having a particle size of 5 to 20 μm were selected with an air classifier to obtain a toner. 0.5 parts by weight of hydrophobic colloidal silica was externally added to 100 parts by weight of this toner to obtain a developer.

The above developer was applied to a commercial copying machine NP-3525 (manufactured by Canon). The fixing temperature of the developer was 140 ° C., and offset development was not observed from the fixing temperature of 140 ° C. to 210 ° C.

Further, the temperature of the fixing roller was set to 160 ° C., and a durability test of 30,000 sheets was conducted. As a result, a good image with high image density including fog and no fog was obtained. Also,
Even after 30,000 sheets, there was no offset development on the fixing roller, and there were no problems such as scratches and toner fusion on the surface of the photosensitive drum, cleaning blade, developing sleeve, and aggregation in the developing device.

Example 2 A developer was obtained in the same manner as in Example 1 using 20 parts by weight of the polymer synthesized in Production Example II and the polymer synthesized in Production Example IV.

When a test was conducted in the same manner as in Example 1, the fixing temperature was
At 135 ° C., roller stain and image stain due to offset development were not seen in the durability test.

Comparative Example 1 A developer was obtained in the same manner as in Example 1 by using 50 parts by weight of the polymer of Production Example I and 50 parts by weight of the polymer having an MI of 3.2, which was synthesized in substantially the same manner as in Production Example I. The amount of fine pulverization by the air jet type pulverizer was 89% of that in Example 1.

Further, when the same test as in Example 1 was conducted, the fixing temperature was inferior at 160 ° C., and further, because the flow adhesion of the toner to the paper was insufficient, the fixed image was easily removed by rubbing the image area.

Comparative Example 2 Example 1 was prepared using 50 parts by weight of the polymer of Production Example III and 50 parts by weight of a polymer having an MI of 1.0, which was synthesized in the same manner as in Production Example IV.
A developer was obtained in the same manner as in. When tested in the same manner as in Example 1, the fixing temperature was 140 ° C., but when set to 160 ° C. and subjected to a durability test of 30,000 sheets, the fixing roller was stained with toner during the durability test. And caused image pollution.

Comparative Example 3 A developer was obtained in the same manner as in Example 1 by using the polymer having MI of 3.2 used in Comparative Example 1 and the polymer having MI of 1.0 used in Comparative Example 2. When tested in the same manner as in Example 1,
The fixing temperature was inferior at 160 ° C, and an offset to the fixing roller occurred in the durability test set at 160 ° C.

[Effect of the Invention] As described above, by defining the melt index of the polymers A and B by the organic peroxide initiator and the azo initiator as polymer A <polymer B and using it as the binder resin, A toner having excellent low-temperature fixability, anti-offset property, durability, fixability, etc., with less adhered matter to the photoconductor, and a high-density image free from fog can be obtained.

Claims (1)

[Claims] 1. A vinyl-based polymer A polymerized by using only an organic peroxide-based initiator as a polymerization initiator, and a vinyl-based polymer polymerized by using only an azo-based initiator as a polymerization initiator. A toner for developing an electrostatic charge image containing a binder resin containing a polymer B and a colorant, wherein the melt index of the vinyl polymer A is smaller than the melt index of the vinyl polymer B. Characteristic toner for developing electrostatic image.