JPH03107867A - Developer for electrophotography - Google Patents

Abstract

PURPOSE:To improve fixing strength by making combination use of a toner contg. a thermosetting resin and a toner contg. the hardener of the thermosetting resin. CONSTITUTION:The toner contg. the thermosetting resin and the toner contg. the hardener of the thermosetting resin are used in combination. The thermosetting resin is exemplified by, for example, an epoxy resin, urea resin, melamine resin, etc. The use of the epoxy resin is preferable above all in order to enhance the adhesive strength of the toner. The hardener to be used varies with the kind of the resin to be used and the hardeners adequate for the respective resins are selectively used. The thermosetting reaction in addition to the fusion among the toners are induced by the heat treatment at the time of fixing and, therefore, the adhesive strength between the toners is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic developer used in an image forming apparatus such as a copying machine.

<Prior Art> In general, electrophotography involves a charging process in which a photoreceptor is uniformly charged by corona discharge, and an exposure process in which an original image is exposed to the charged photoreceptor to form an electrostatic latent image corresponding to the original image. , a development process in which the electrostatic latent image is developed with a developer containing toner to form a toner image, a transfer process in which the toner image is transferred to a base material such as paper, and a toner image transferred onto the base material is fixed. The so-called Carlson process, which consists of a fixing process to obtain an image, is widely used.

In the fixing step, a heat roller fixing method has conventionally been used. In this method, toner adhered to a substrate is melted by a heat roller and a pressure roller or a heat roller and a belt roller under high temperature and pressure, and is crushed to form an image on the substrate.

A more detailed analysis of the toner fixing process reveals that (1) thermal energy is applied to the toner as it passes through the above-mentioned fixing mechanism, and (2) there is a semi-heating process in which the toner is heated close to its softening point. The toner progresses in the following order: molten state, (3) spreading on the base material due to fusion between toners, and (4) penetration into the base material, and then fixing is completed.

<Problems to be Solved by the Invention> However, conventional fixing methods using heat fusion have drawbacks such as toner peeling off due to bending of the base material after image formation and toner adhesion to frictional objects (such as cloth) due to friction. The fixing strength of the toner was not sufficient. In order to solve these problems, binder resins (styrene polymers, acrylic polymers, ethylene polymers, etc.) conventionally used in toner have been developed.
Although various studies have been conducted on thermoplastic resins such as vinyl acetate copolymers and polyvinyl chloride, the reality is that no developer with sufficiently satisfactory fixing strength has been obtained.

The present invention has been made to eliminate the above-mentioned problems, and an object of the present invention is to provide an electrophotographic developer that has excellent fixing strength of toner to a base material such as paper and does not cause peeling or the like.

Means and Effects for Solving the Problems The electrophotographic developer of the present invention includes a toner containing a thermosetting resin and a toner containing a curing agent for the thermosetting resin.

In other words, the present inventors have found that, in general, it is the adhesive force caused by the fusion between toners that greatly contributes to the fixing strength to the base material.
Based on the knowledge that if the adhesive strength between toners is high, the toner that has penetrated into the base material will prevent the toner from peeling off the base material surface and improve the fixing strength, and as a result of extensive research, we have found that When using a developer containing a toner containing a curable resin and a toner containing a curing agent, heat treatment during fixing causes not only fusion but also a thermosetting reaction between the toners. They discovered a new fact that the adhesive strength is significantly improved, and completed the present invention.

The thermosetting resin used in the present invention includes:
Examples include epoxy resin, urea resin, melamine resin, phenol resin, resorcinol resin, polyurethane, vinyl urethane, etc. Epoxy resin, phenol resin, or polyurethane is particularly preferred for ease of toner preparation. It is preferable to use it in order to increase the fixing strength of the toner.

The curing agent used varies depending on the type of resin to be used, and a curing agent suitable for each resin is selected and used. For example, when using epoxy resin, bis(4-
Alicyclic polyamines such as aminocyclohexyl)methane; 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecyl imidazole, 2-phenylimidazole, 1
-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2,4-diamino-6-
[2-Methylimidazolyl-(1)]-]ethyl-5y
Imidazole compounds such as a+-triazine; BF3
BF complexes such as monoethylamine complex; diaminodiphenylmethane, diaminodiphenylsulfone, m-
Aromatic polyamines such as phenylenediamine; phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, chlorendic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bis(anhydrotrimate) methyl Examples include acid anhydrides such as cyclohexenetetracarboxylic anhydride, trimellitic anhydride, and polyazelaic anhydride; phenolic resins such as novolak; amino resins; dicyandiamide; and hydrazide compounds such as adipic acid hydrazide.

Further, when a novolac type phenol resin is used, an example of the curing agent is hexamethylenetetramine. Furthermore, when polyurethane is used, various polyols, polyamines, polyisocyanates, etc. can be mentioned as curing agents.

The thermosetting resin-containing toner (hereinafter simply referred to as resin-containing toner) in the present invention is composed of the thermosetting resin, a colorant, a charge control agent, and a release agent.

In addition, when the curing agent used is itself a binding resin such as an amino resin, in addition to the curing agent, the toner containing a curing agent also contains the same coloring agent, charge control agent, and other releasing agent as the resin-containing toner. It consists of molding agents, etc. On the other hand, when the curing agent itself does not serve as a binding resin, a thermoplastic resin conventionally used as a binding resin is added in addition to the above-mentioned ingredients. Examples of thermoplastic resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl acetate copolymer, and styrene. -Maleic acid copolymer, styrene-acrylic acid ester copolymer (
Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.)
, styrene-methacrylate copolymer (styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl chloroacrylate copolymer , styrenic resins such as styrene-acrylonitrile-acrylic acid ester copolymers (unipolymers or copolymers containing styrene or styrene substitutes), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic acid resins , phenyl resin, epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, etc., especially styrene. It is preferable to use a styrene-based resin or a styrene-acrylic resin.

Examples of the coloring agent include black pigments such as carbon black and acetylene black; yellow pigments such as yellow lead, zinc yellow, and cadmium yellow; red yellow lead, molybdenum orange,
Orange pigments such as permanent orange GTR; red pigments such as red red, cadmium red, red lead; violet pigments such as manganese violet, fast violet B1 methyl violet lake; blue pigments such as ultramarine blue, cobalt blue, alkali blue lake; chrome green, Green pigments such as chromium oxide and malachite green lake; zinc white,
Examples include white pigments such as titanium oxide and antimony white; and various metal powders such as conductive carbon black and aluminum powder.

Charge control agents include those for positive charge control and those for negative charge control.Those intended for positive charge control include organic compounds having basic nitrogen atoms, such as basic dyes, aminopyrine, and pyrimidine. Examples thereof include compounds, polynuclear polyamino compounds, etc. On the other hand, those aimed at controlling negative charge include carboxyl group-containing compounds such as alkyl salicylic acid metal chelates.

Examples of the mold release agent include aliphatic resins such as low-molecular polypropylene, aliphatic metal salts, higher fatty acids, fatty acid esters, and especially aliphatic resins having a weight average molecular weight of 1000 to 10000. Preferred examples include low molecular weight polypropylene and paraffin wax.

A suitable blending ratio of the toner is illustrated below. Note that % indicates the ratio to the total amount of toner.

(Left below) a) Formulation example (components) of resin-containing toner and curing agent-containing toner that itself serves as a binding resin (wt%) Thermosetting resin 80-90 or curing agent colorant 5-15 Charge control agent 1-10 Release agent 1-5 Formulation example (components) of toner containing a curing agent that does not itself serve as a binding resin (% by weight) Thermoplastic resin 40-70 Curing agent 50-20 Colorant 5-15 Charge control agent 1 to 10 release agent ], ~ 5 The mixing ratio of the resin-containing toner and the curing agent-containing toner, that is, the mixing ratio when used as a developer, is 10 to 10 of the resin-containing toner.
In order to obtain high adhesive strength, it is preferable that the curing agent toner be used in a range of 15 to 100 parts by weight relative to 0 parts by weight.

These toners are cured only in a hot atmosphere of 50° C. or higher and are not cured at room temperature, and therefore have excellent storage stability. Therefore, since both toners can be mixed and used from the beginning, handling is easy.

The image transferred onto a substrate such as paper using these toners is heat-treated by a heat roller fixing method, an oven fixing method, a flash fixing method, etc., so that thermal energy is transferred to the toner. , the conventional bonding by fusion of toners and a thermosetting reaction between the resin and curing agent contained in both toners occur, and the bonding and adhesion of the toners with each other and the toner with the crystal phase creates an image with high fixing strength. will be obtained.

<Example> Hereinafter, the electrophotographic developer of the present invention will be explained in detail by giving examples.

(Left below) Example 1 (1) Preparation of resinous white toner (components) (1iIi) Amount%) Epoxy resin 85 (Epicoat, manufactured by Yuka Shell Co., Ltd.) Carbon black ](] (MA-1,00, Mi Charge control agent 3 (Subilon Black TRI+, manufactured by Hodogaya Chemical Co., Ltd.) Low molecular weight niboribrobylene 2 (Viscol 550 P% manufactured by Ohyo Kasei I) These components were mixed and melted and kneaded. After cooling, the toner was crushed and classified to obtain a toner having a measured diameter of 1 μn.

(Left below) (2) Preparation of toner containing curing agent (components) (wt%) Amino resin
85 (Knee panties, manufactured by Mitsui Toatsu Co., Ltd.) Carbon blank 8 (MA-1,00S manufactured by Mitsubishi Chemical Corporation) Charge control agent 6 (Subiron Black TRH.

(manufactured by Hodogaya Chemical Co., Ltd.) Low molecular weight polypropylene 1 (Viscol 550P, manufactured by Mitsubishi Kasei Co., Ltd.) These components were mixed and melted using I2 in the same manner as in 1 above, and pulverized to obtain toners having the same average particle size.

Next, the resin-containing toner and the curing agent-containing toner...
They were mixed at a ratio of 7:43 (weight ratio), and 3.5% by weight of the resulting mixed toner was mixed with 96.5% by weight of a ferrite carrier (manufactured by Dowa Iron Powder Co., Ltd.) to prepare a developer.

Example 2 A curing agent-containing toner was prepared with the following blending ratio.

That is, a curing agent (phthalic anhydride) which is difficult to form into a toner by itself is used, and a styrene-acrylic resin, which is a thermoplastic resin, is mixed with this curing agent (phthalic anhydride).

(component) (lii'l: ffl
%) Styrene-acrylic resin 50 (manufactured by Sekisui Chemical Co., Ltd.) Phthalic anhydride 40 (manufactured by Wako Pure Chemical Industries, Ltd.) Carbon black 6 (MA-100, manufactured by Mitsubishi Chemical Corporation) Charge control agent 3 (Sviron Black TRH1) (manufactured by Tsuchiya Chemical Co., Ltd.) Low molecular weight polypropylene 1 (Bisyl 550P, manufactured by Sanyo Chemical Co., Ltd.) These components were mixed, melted and kneaded at 711, allowed to cool, then crushed and classified to produce toner with an average particle size of 11 μm. death.

Ta.

Using the toner obtained in Example 1 as the resin-containing toner,
This resin-containing toner and curing agent-containing toner were mixed at 42:58.
3.5% by weight of the resulting mixed toner was mixed with 96.5% by weight of a ferrite carrier (manufactured by Dowa Iron Powder Co., Ltd.) to prepare a developer.

Comparative Example Using a thermoplastic resin, a toner that was fixed only by heat fusion was produced. The blending ratio of this toner is as follows.

(Ingredients) (% by weight) Styrene-acrylic resin 87 (manufactured by Tsukisui Kagaku Co., Ltd.) Carbon black 8 (MA-100, manufactured by Mitsubishi Chemical Corporation) Charge control agent 2 (Subiron Black Tl?H.

(manufactured by Hodogaya Chemical Co., Ltd.) Low molecular weight polypropylene 3 (Viscol 550P, manufactured by Mitsubishi Kasei Co., Ltd.) These components were mixed, kneaded, crushed and classified in the same manner as in Example 1 to prepare a toner having an average particle size of 11 μm. 3. of this toner.
5% by weight and 96.5% by weight of ferrite carrier (described above)
A developer was prepared by mixing with

Toner fixability evaluation test Each developer obtained in Example 1.2 and Comparative Example was put into a copying machine (Mita DC-AO manufactured by Mita Kogyo Co., Ltd.),
The image was copied and the fixing performance was evaluated. The fixing temperature at this time was set at 135°C.

The test method and test results are shown below.

(A) Folding Fixability Test The solid black portion of the image was bent with a certain external force, the state of the toner at the folded portion was observed, and evaluated based on the following criteria.

O... No damage to the toner at the bent part △...
Toner destruction at the folded part is small × ... Toner destruction at the folded part is large
At a constant speed), the toner adhering to the surface of the cloth was observed and evaluated based on the following criteria.

○ ・・・ No toner adhesion to the cloth surface △ ・・・
There is toner adhesion to the cloth surface, and the image condition is slightly deteriorated. A tape with a constant adhesive force was peeled off at a constant speed, and the amount of toner attached to the tape was observed and evaluated based on the following criteria.

O・-・ No toner adhesion to the tape △ ... Toner adhesion to the tape, slight deterioration of the image condition Shown in the table below.

(Left below) From the table, it can be seen that the toner obtained in the comparative example is only heat-fused.
It can be seen that the toners obtained in Examples have excellent fixing strength and do not peel off easily because the toners obtained in Examples also undergo a thermosetting reaction in addition to heat fusion.

<Effects of the Invention> According to the present invention, since the developer is composed of a toner containing a thermosetting resin and a toner containing a curing agent, a thermosetting reaction occurs between the toners due to heat treatment during fixing. Therefore, the adhesive force between the toners is significantly improved compared to the case where only fusion is used, and therefore, the fixing strength of the image to the substrate is increased, and peeling resistance is improved.

Claims (1)

[Scope of Claims] 1. An electrophotographic developer comprising a toner containing a thermosetting resin and a toner containing a curing agent for the thermosetting resin. 2. The electrophotographic developer according to claim 1, wherein the toner containing the curing agent further contains a thermoplastic binder resin.