JPH0644161B2 - Electrophotographic toner composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic toner composition in which a colorant is dispersed in a binder resin.

2. Description of the Related Art The electrophotographic method generally uses a photoconductive substance to form an electrical latent image on a photoconductor by various means, and then develops the latent image with a toner and, if necessary, a paper. After transferring the powder image to, etc., it is fixed by heating or solvent vapor,
You get a copy.

As a method of visualizing an electrical latent image using toner,
Magnetic brush method, cascade developing method, powder cloud method and the like are known, but it goes without saying that fixing of the toner image is an important step in any developing method. Especially when considering application to a high-speed copying machine, since a heat roll fixing device is adopted, the toner image and the heat roll come into contact with each other in a heating and melting state at the time of fixing, and a part of the toner image adheres to the surface of the heat roll. It is required that relocation, so-called offset does not occur.

Obtaining such offset-free toner is a more difficult problem when considering application to a high-speed copying machine that does not use much electric power for a fixing device and uses a heat roll, a so-called labor-saving high-speed copying machine. Suits. That is, in order to prevent offset, the binder polymer used in the toner is required to be as strong as possible and have sufficient melt fluidity. However, in order to have melt fluidity, the toner must be heated to a considerably high temperature, which does not satisfy the demand for labor saving. Therefore, in order to save labor, fixing at low temperature is required, and it is preferable to use a resin having a low glass transition point and a low molecular weight. However, a resin having a low molecular weight naturally has no toughness and tends to cause offset.

Conventionally, for the toughening of toner for preventing offset, a polymer having an average molecular weight of about 100,000 or more, particularly a vinyl polymer, is often used. To fix a toner using a high molecular weight vinyl polymer at a low temperature, there is a method of lowering the glass transition point of the polymer as low as possible unless blocking occurs, or a fixing temperature is lowered by adding a plasticizer.

However, these methods not only lower the fixing point (minimum temperature for complete fixing) but also lower the hot offset temperature (temperature at which the offset starts to occur) at the same time, which results in a decrease in temperature between the fixing point and the hot offset temperature. This results in only moving the temperature range, the so-called fusing ratchet, to the low temperature side. If it is attempted to prevent the temperature of the hot offset temperature from decreasing due to the increase of the weight average molecular weight, the viscosity of the resin is increased and the effects of the glass transition point decrease and the addition of the plasticizer are diminished.

On the other hand, a polyester resin has a low glass transition point unlike a vinyl polymer, and a resin having a low molecular weight can be easily obtained. This means that the low temperature fixing toner can be easily obtained.

However, since the polyester resin is a low molecular weight resin, the offset is violent and the heat roll toner is
It cannot be used as it is.

Therefore, in order to take advantage of the properties of the vinyl-based polymer, which does not cause offset up to a high temperature, and the ability of the polyester to be fixed even at a low temperature, it is conceivable to blend both resins, for example, JP-A-54-114245.
It is described in Japanese Patent Publication No. However, in the case of a high molecular weight vinyl polymer and a low molecular weight polyester resin, the compatibility between the resins is poor and a non-uniform dispersion state results. In particular, the compatibility becomes worse as the molecular weights of the two differ, and when the dispersed state is observed with a phase contrast microscope, it is observed as if there are islands in the sea.

This is also observed when blending poorly compatible plastics, and is described in Plastics, 13 , No. 9, 1 (1962) as the sea-island theory.

When the sea-islands as described above are formed in the toner resin, the other components of the toner such as a polarity control agent such as a dye, a carbon black, and a coloring agent such as a magnetic substance are not sufficiently dispersed, and repeated copying is performed. Then, reversely charged toner is generated, and so-called fogging occurs.

On the other hand, in order to improve the dispersibility of the polyester resin and the vinyl polymer, a method of introducing a common segment into both and forming a graft copolymer has also been proposed. However, in the case of such a resin made into a copolymer, the advantages of the two resins, namely, the hot offset resistance and the low temperature fixing property, cannot be utilized and they are averaged.

It is an object of the present invention to provide an electrophotographic toner composition which does not cause hot offset on a heat roll, can be fixed with a small amount of heat, and has good charging stability.

As a result of intensive studies, the inventors of the present invention have found that even with a vinyl-based polymer and a polyester resin, which have been considered to have poor compatibility as described above, the compatibility is improved under certain conditions and the advantages of both are utilized. As a result, they have found out that the present invention has been made.

That is, the present invention provides an electrophotographic toner composition comprising a binder resin and a colorant dispersed therein, wherein the binder resin has a weight average molecular weight of 8000 to 16000 and a glass transition temperature of 55 ° C to
65 ° C polyester resin and weight average molecular weight of 200,000-5
At least one selected from acrylic acid having a glass transition temperature of 50 ° C to 65 ° C, methacrylic acid, maleic acid, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl methacrylate, glycidyl acrylate, alkoxymethylol acrylamide, and allyl alcohol having a glass transition temperature of 0,000. A mixture of one monomer and a vinyl polymer obtained by copolymerizing a monomer containing at least one monomer selected from styrene, vinyltoluene, methylstyrene, acrylonitrile, and methacrylonitrile as a monomer component, and in the mixture The ratio of the polyester resin to the vinyl polymer is 25 to 54 wt%.

When the weight average molecular weight of the polyester resin is less than 8,000 and the molecular weight of the vinyl-based polymer exceeds 500,000, the compatibility of the two resins deteriorates to form a so-called sea-island, and a colorant,
It is not preferable because the dispersibility of the charge control agent and the like deteriorates and the charge becomes unstable. Also, the molecular weight of polyester resin is 16
If it exceeds 000, the characteristic of polyester, which is low temperature melting, cannot be fully utilized. The molecular weight of the vinyl polymer is 20
If it is less than 10,000, the offset temperature will be low, and the advantages of the vinyl-based polymer, which is less likely to cause offset, cannot be utilized.

The glass transition temperature is preferably high in order not to cause hot offset, but it is not desirable to raise the glass transition temperature to 65 ° C. since the fixing lower limit temperature rises too much. Further, the polyester resin is more likely to be melted first during fixing, and if the vinyl polymer is not yet melted, it is not fixed during fixing and a so-called cold offset is formed. Therefore, the glass transition temperature of the polyester resin is preferably 55 ° C. to 65 ° C. and has a high glass transition point. If the glass transition temperature of the vinyl-based polymer is less than 50 ° C., the heat-resistant storability deteriorates and so-called toner blocking occurs. Therefore, it is important that the glass transition temperature of the vinyl polymer is 50 ° C to 65 ° C.

When the blending ratio of the polyester resin to the vinyl polymer in the mixture of the polyester resin which is the binder resin of the toner and the vinyl polymer is less than 25 wt%,
Although hot offset does not occur, the purpose of low temperature fixing cannot be achieved. On the other hand, if it exceeds 54 wt%, the lower limit fixing temperature does not decrease so much, and the decrease in the hot offset temperature is larger. Therefore, the temperature difference between the fixing temperature and the hot offset temperature, that is, the so-called fading latitude is narrowed, which is not preferable.

The polyester resin and vinyl-based polymer used in the toner of the present invention are required to satisfy the above weight average molecular weight and glass transition temperature. Specific examples of both are as follows.

The polyester resin is composed of a dihydric alcohol as shown in the following group A and a dibasic acid as shown in the group B, and a trihydric or higher alcohol or carboxylic acid as shown in group C. May be added as a third component.

Group A: ethylene glycol, triethylene glycol,
1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bis Phenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2.2) -2,2'-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenol) Enil)
Propane, polyoxyethylene (2.0) -2,2-bis (4
-Hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4
-Hydroxyphenyl) propane and the like.

Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sepatic acid, malonic acid,
Linoleic acid, esters of these acid anhydrides or lower alcohols, etc.

Group C: trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid.

The vinyl polymer is a copolymer composed of a monomer having a functional group shown in group D below and a monomer copolymerizable with a monomer of group D shown in group E, and the acrylic resin shown in group F as the third component. Acid esters may be added.

Group D: acrylic acid, methacrylic acid, maleic acid, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl methacrylate, glycidyl acrylate,
Alkoxymethylol acrylamide, allyl alcohol.

Group E: styrene, vinyltoluene, methylstyrene, acrylonitrile, methacrylonitrile.

Group F: methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate,
Cyclohexyl methacrylate, stearyl methacrylate, etc.

Examples of the colorant used in the toner of the present invention include carbon black, nigrosine dye (C.INo.50415B), aniline blue (C.INo.50405), and chalco oil blue (C.INo.
Azoec Blue 3), Chrome Yellow (C.INo.14090), Ultramarine Blue (C.INo.77103), Dyupon Oil Red
(C.INo.26105), quinoline yellow (C.INo.47005), methylene blue chloride (C.INo.52015), phthalocyanine blue (C.INo.74160), malachite green oxalate (C.INo.42000), Ranfubrak (C.INo.77266), Rose Bengal ((C.INo.45435) and their mixtures, etc. can be mentioned. This colorant is in a sufficient proportion so that a sufficient visible image is formed on development. It is necessary that the content of the binder resin be about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

Further, the toner of the present invention can be used for both dry one-component developer and two-component developer, and as the magnetic substance in the case of one component, iron such as ferrite and magnetite,
An alloy containing an element exhibiting ferromagnetism such as cobalt or nickel, or an alloy containing no compound or a ferromagnetic element but exhibiting ferromagnetism by appropriate heat treatment, for example, manganese-copper-aluminum or manganese- Examples thereof include alloys of the type called Heusler alloys containing manganese such as copper-tin and copper, or chromium dioxide. The magnetic substance is uniformly dispersed in the binder resin in the form of fine powder having an average particle size of 0.3 to 5 μm. The content of the magnetic particles is 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of the toner.

The toner composition according to the present invention is made by any of the well known toner mixing and grinding methods. For example, all the ingredients are mixed in predetermined amounts, mixed and milled to thoroughly mix all the ingredients, and then the resulting mixture is micronized. In another known method of forming toner powders, the colorant, resin and solvent are ball milled and the toner formulation mixture is spray dried.

In order to use the toner composition according to the present invention by the cascade developing method, the magnetic brush developing method, the C-shell developing method and the like, the composition has an average particle size represented by weight percentage of about 30 microns or less. This average particle size should be between about 4 and 20 microns for optimum results. For use in powder cloud development, a particle size of just under 1 micron is desirable.

Coated carriers and uncoated carriers used in cascade development, magnetic brush development, C-shell development and the like are well known, but toner particles adhere to the carrier particles and surround them. The carrier particles may be formed of any suitable material as long as the donor powder acquires a charge of the opposite polarity to that of the carrier particles when the carrier particles are in intimate contact with the toner powder. Accordingly, the toner compositions of the present invention may be mixed with conventional carriers to develop electrostatic latent images on any suitable electrostatic latent image bearing surface including conventional photoconductive surfaces. used.

Effects According to the present invention, the molecular weight of the polyester resin and the vinyl-based polymer, the appropriate range of the glass transition temperature is selected, and both are mixed at an appropriate mixing ratio. A toner having a stable charge can be obtained without sacrificing the property of the vinyl polymer that does not cause hot offset.

Hereinafter, the effects of the present invention will be specifically shown by examples.

Example 1 A polyester resin composed of polyoxyethylenated bisphenol A and fumaric acid (glass transition temperature 60 ° C., weight average molecular weight 12000), and styrene-nBMA-2EHA copolymer (8
(0: 5: 15) (glass transition temperature 55 ° C., weight average molecular weight 300,000) at various ratios, and carbon rack 15
The parts were kneaded and finely pulverized with a Jetomizer used for ordinary toner production to obtain 7 types of toner having an average particle size of 11.5 μm.

When these toners were mixed with iron powder carrier and the fixing point, offset point and charge stability were determined with a copying machine (FT-4060 manufactured by Ricoh), the results shown in the table below were obtained. When this result is graphed, it becomes as shown in the figure. In the figure, A is the offset generation temperature, B is the fixing possible temperature range, C is the minimum fixing temperature, and D is the energy-saving fixing range.

From this, in the range where the ratio of polyester resin to vinyl resin is 25 to 54 wt% (No. 3, 4 and 5), the minimum fixing temperature C is low, the hot offset temperature is high, and the charging stability is good. I understand. When the ratio of polyester resin exceeds 54 wt%, fixing temperature range B
It is shown in the figure that the value of becomes smaller rapidly.

On the other hand, 30 parts of polyester resin (glass transition temperature 50 ° C, weight average molecular weight 4000) and styrene-butadiene copolymer (glass transition temperature 50 ° C, weight average molecular weight 1.5 million)
Toner (No.
8) was prepared and a fixing test was conducted. As a result, the hot offset temperature was 240 ° C. and the minimum fixing temperature was 140 ° C., which was good, but the charging stability was poor. As a result of observing the cross section of this toner with a transmission electron microscope, the toner has the sea-island structure described above, and it is presumed that the charging stability is poor due to the poor dispersibility of both resins.

Example 2 Polyester resin composed of bisphenol A and maleic anhydride (glass transition temperature 55 ° C., weight average molecular weight 1000
0) and styrene-nBMA copolymer (glass transition temperature 65
Example 1 by changing the compounding ratio of ° C and weight average molecular weight 350,000)
The same evaluation as was done. As a result, the same results as those shown in the previous table and the figures were obtained, and the best ratio was 25 to 54 wt% of the polyester resin to the vinyl polymer.

Example 3 Polyester resin composed of bisphenol A and maleic anhydride (glass transition temperature 55 ° C., weight average molecular weight 10000)
The same evaluation as in Example 1 was carried out by changing the compounding ratio of the methyl methacrylate-nBMA copolymer (glass transition temperature 55 ° C., weight average molecular weight 320,000). As a result, the same results as in Example 1 were obtained, and the best ratio of the polyester resin to the vinyl polymer was in the range of 25 to 54 wt%.

Example 4 Polyester resin composed of polyoxyethylenated bisphenol A and fumaric acid (glass transition temperature 60 ° C., weight average molecular weight 12000) and styrene-ethyl acrylate copolymer (glass transition temperature 60 ° C., weight average molecular weight 310,000) The same evaluation as in Example 1 was performed by changing the compounding ratio of. as a result,
The same results as in Example 1 were obtained, and the best ratio was in the range of 20 to 35 wt% of the polyester resin to the vinyl polymer.

[Brief description of drawings]

The figure shows an example of a graph showing the effect of the blending ratio of the polyester resin and the vinyl resin on the performance of the toner. A: Offset generation temperature, B: Fixable temperature range C: Minimum fixing temperature, D: Energy saving fixing range

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhiro Nakayama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-54-114245 (JP, A) JP-A-58 -11955 (JP, A)

Claims (1)

[Claims] 1. An electrophotographic toner composition comprising a binder resin and a colorant dispersed therein, wherein the binder resin has a weight average molecular weight of 8000 to 16000 and a glass transition temperature of 55 to 65 ° C.
Polyester resin and a weight average molecular weight of 200,000 to 500,000, glass transition temperature 50 ℃ ~ 65 ℃ acrylic acid, methacrylic acid,
At least one monomer selected from maleic acid, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl methacrylate, glycidyl acrylate, alkoxymethylol acrylamide, and allyl alcohol, and styrene, vinyltoluene, methylstyrene,
It is a mixture with a vinyl polymer obtained by copolymerizing a monomer containing at least one monomer selected from acrylonitrile and methacrylonitrile as a monomer component, and the ratio of the polyester resin to the vinyl polymer in the mixture is 25 to 54 wt%. And an electrophotographic toner composition.