JPS59116757A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To enhance fixability and stability of an electrographic toner by forming a coating layer made of a resin having >=50 deg.C glass transition temp. on the surface of the toner having at least one component resin having <=20 deg.C glass transition temp. CONSTITUTION:An electrophotographic toner is composed of a toner material being a core part and a coating layer covering the surface. The resin used for this toner material is a PE resin, etc. having <=20 deg.C glass transition temp. for enabling pressure fixing, that is, high ductility and malleability. The coating resin to be used as a resin, such as acrylic or styrene resin, having >=50 deg.C glass transition temp. This coating resin insulates the toner material from the exterior by coating it at the time except that of fixing, but at the time of fixing, it needs to be broken by a prescribed pressure. Such an electrophotographic toner has fluidity in the core toner material at the fixing temp. but not in the coating layer, and hence, stability and fixability can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrophotographic toner used for developing electrostatic latent images such as electrophotography.

[Technical background of the invention and its problems]

Various materials are used for electrophotographic toners according to seven fixing force formulas. There are two types of fixing methods: a heat fixing method and a pressure fixing method.Recently, the pressure fixing method has been attracting attention for the purpose of reducing power consumption and downsizing fixing devices. The pressure fixing method performs fixing using only pressure, and in this case, toner for electrophotography is a so-called low-temperature fixing toner.The low-temperature Uji toner uses a material whose main component is a resin with a transition temperature △ below room temperature, such as polyethylene. It is generated and awned. On the other hand, electrophotographic toners made of such materials are susceptible to blocking, adhesion, and adhesion in areas exposed to rise in room temperature or mechanical pressure in the cleaning blade of the photoreceptor or inside the developing device. For this reason, conventionally, fine powder of fluoride such as vinylidene fluoride, or a fluid phase such as silicone oil or silica oxide is washed and adhered to the surface of such toner for photographic use. However, when electrophotographic toner containing additives is used for a long period of time, the additives may detach from the electrophotographic toner and accumulate in the developing device, or may be deposited on image supports such as photoreceptors. There is a problem that it adheres and adversely affects the image.

[Purpose of the invention]

The present invention has been made in order to eliminate the above-mentioned problems, and is an electrophotographic photographic device that does not cause blocking even in high-temperature environments or when subjected to mechanical stress, and has good pressure fixing properties. It is intended to provide toner for use.

[Summary of the invention]

The present invention provides pressure constant M properties by coating the particle surface of a photochromic toner containing at least one component of a resin having a glass transition temperature of 20'Q or lower with a resin having a glass transition temperature of 50'Q or higher. This improves bronking resistance without deteriorating the properties.

[Embodiments of the invention]

Next, the present invention will be explained in detail with reference to one embodiment.

The electrophotographic toner of this embodiment is composed of a toner material forming the center and a coating layer covering the surface of the toner material. The composition of the above-mentioned toner material has a glass transition temperature of 20°C or less to achieve pressure fixing ability, that is, it is highly ductile and malleable at room temperature (under the environmental temperature where the toner is used),
Polyethylene laparotomy, etc., which easily causes deformation and flow when a predetermined pressure is applied, is used. In addition, other compositions include fixing aids such as enalene vinyl succinate copolymer, which is easily adsorbed on copy paper, carbon, magnetic powder (-component type magnetic toner material), etc. for monochrome use. (in cases where the coloring agent is used), etc. can be used. These toner material compositions are mixed and kneaded using a VC such as a pressure kneader, and the kneaded material is pulverized and classified to form a toner material (corresponding to a conventional toner).

The material forming the above-mentioned coating layer is a resin having a glass transition temperature of 50'O or higher, that is, a resin that causes fluidity (molecules constituting the resin move easily) under the environmental temperature where the toner is used. W fat, such as acrylic,
Styrene, styrene acrylic copolymer, polyester,
Epoxy resin or the like may be used.Also, the coating layer must cover the surface of the toner material except during fixing, isolate the toner material from the outside, and be destroyed by a predetermined pressure during fixing. It is. Therefore, it is desirable that the coating layer be made of a material that is brittle to some extent and that its thickness is as thin as possible. For this reason, in this example, a crosslinking agent is added to the above-mentioned acrylic, styrene, styrene-acrylic copolymer, polyester, epoxy resin, etc. to cause a chemical reaction (crosslinking), so that the material has a certain degree of brittleness. (Crosslinking degree 30
% or more):, ) is used as the material forming the coating layer.

This substance is also coated on the surface of the toner material by a spray drying method. That is, crosslinked materials such as acrylic, styrene, styrene-acrylic copolymer, polyester, and epoxy resin are mixed with toluene, methyl ether ketone,
The cross-linked resin described in E is coated on the surface of the toner material by passing the toner material into the atomized air of a solution dissolved in an organic solution such as dioxane, THF, trichlene, etc., and then drying under reduced pressure or at elevated temperature to perform the actual process. The electrophotographic toner in the example can be manufactured and recovered. At this time, in order to make the thickness of the coating layer on the surface of the toner material as thin as possible, acrylic, styrene, styrene-acrylic copolymer,
It is desirable that h of the material obtained by omitting crosslinking of polyester, epoxy resin, etc. is 1 Q wt % or less in terms of weight ratio. In addition, since the particle size of the collected toner increases due to partial aggregation of the toner material or other causes during the formation of the coating layer, the toner is classified as necessary. On the other hand, ataryl, styrene,
If the degree of crosslinking of styrene-acrylic copolymers, polyesters, epoxy resins, etc. is high, the degree of gelation of the substance will be high. When each section sprays this solution onto the toner material, it becomes difficult to spray it. Konoke 2. The limit of strength (which varies depending on the degree of crosslinking) is approximately determined by the combination of resin and solvent used. Therefore, in order to give the above-mentioned coating layer some degree of brittleness, the degree of crosslinking of the resin used as the coating layer must be determined by considering the combination of the resin used and the solvent used to dissolve the resin. Select as appropriate.

The electrophotographic toner of this example made as described above is
Under the operating environment temperature, the toner material forming the center of the toner material is in a state where it is easy to flow. This is because, as mentioned above, the toner material is made of a resin with a low glass transition temperature (20 DEG or less). However, this toner material has a toner [
The crow transition temperature (50°
0 or more), that is, a coating layer made of a material that does not flow under the environmental temperature at which the toner is used.

Therefore, in the electrophotographic toner of this embodiment, the toner material forming the center portion is protected by this coating layer, and flow is prevented from occurring under the environmental temperature at which the toner is used. Therefore, when the electrophotographic toner of this example is used in an electronic multi-function machine, even if it is subjected to mechanical stress under the operating environment temperature, the toner particles may coagulate and harden (blocking) in the developing device. ), it will not fuse to the surface of the photoreceptor and adversely affect the image. In addition, when the environmental temperature in which the toner is used is high or easy to change, and when fixing the image formed by the toner for the prince photograph of this example on copy paper, etc., a predetermined pressure △ must be applied. As a result, the coating layer is destroyed and the toner material forming the center part oozes out and moves, making pressure fixing possible. In particular, in this embodiment, since the coating layer is made of a resin having a certain degree of brittleness as described above, it is easily destroyed by a predetermined pressure during fixing. Therefore, the electrophotographic toner of this embodiment is There is no deterioration in pressure fixing properties due to the material being covered with a coating layer.

The results of a comparative experiment between the electrophotographic toner of this example and a conventional toner will be shown below.

For example, polyethylene resin: Sunwax 171P (Sanyo Chemical) 40 wt%, ethylene succinate pyrolyte copolymer: Evaflex 220 (Mitsui Polychemical) 10 wt%,
Magnetic powder; BL-too (4tan Kogyo) 50wt% composition was mixed and kneaded in a pressure kneader, and this was further crushed and classified to form a conventional toner with a weight average particle size of 12μ (the toner material in this example). corresponding) was generated. Also, the degree of crosslinking (
Using a solution of a styrene acrylic resin (glass transition temperature Tg50"0 or higher) with a gelation degree of 30" dissolved in a toluene solvent, the surface of the above conventional toner is coated with a crosslinking degree of 30" and a glass transition temperature of 30" by spray drying. A coating layer made of styrene acrylic resin at a temperature of 50°C or higher was formed.The weight ratio to the conventional toner was 10 wt% or less.After this, the electron particles of this example with a weight average particle size of 12μ were classified. Photographic toners were collected.The above conventional toner and the electrophotographic toner of this example were as follows:
Q that was tested for fixability without twisting, i.e. 35Kg/c1
A comparison was made of the fixing properties of the conventional toner fixed at a pressure of rL and the electrophotographic toner of this example in terms of the rubbing strength against paper of a solid image, but no difference was found.

This shows that the electrophotographic toner in this embodiment, despite being covered with the coating layer, has the same good fixing properties as the conventional toner that is not covered with the coating layer. Next, we compared the blocking resistance by continuously operating the developing device using the conventional toner and the electrophotographic toner of this example. On the other hand, the electrophotographic toner of this example did not show any toner clumping even after continuous operation for more than 12 hours. The temperature inside the developing device was approximately 40° C. at the end of the operation. This shows that the electrophotographic toner of this example has much better -C blocking resistance than conventional toners. As described above, the electrophotographic toner of this example maintains good fixing properties and does not cause blocking even when subjected to mechanical stress.

Note that the present invention is not limited to this embodiment.

The present invention produces the above-mentioned effects by coating the surface of the toner material forming the center, that is, the surface of the conventional toner, with a resin having a glass transition temperature of 50°C or more, and the present invention achieves the above-mentioned effects without changing the gist thereof. Various modifications are possible.

[Object of the present invention]

As explained above, according to this embodiment, even in a high temperature environment or when subjected to mechanical stress, the
Therefore, for example, toner particles that harden in a developing device, etc., do not fuse to the surface of a photoreceptor that supports a toner image and adversely affect the image, and have good fixing properties. A toner for electrophotography can be provided.

Procedural amendment band (voluntary) Showa 5th report, 7. Evening 9th, Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, Name of the invention: Toner for electrophotography 3, Relationship to the amended person case Patent Applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, Agent: Uchisaiwai-cho, Chiyoda-ku, Tokyo 100 1-1-6 Column 6 of the detailed description of the invention in the specification, contents of amendment (1) "Degree of gelling power" on page 6, line 19 of the specification is amended to "degree of gelling" 0 ( 2) Similarly, page 7, line 9: “Toner material is easy to flow.”
``Toner material fluidly deforms due to pressure.''
Corrected with 0 or more

Claims (1)

[Scope of Claims] (1) In an electrophotographic toner containing at least one component of a resin having a glass transition temperature of 20°C or lower, the surface of the electrophotographic toner contains a resin having a glass transition temperature of 50°C or higher. (2) A toner for electrophotography according to claim 1, characterized in that a resin constituting the coating layer has a gelation degree of 30 or more. Toner 0 (3) The toner for electrophotography according to claims 1 and 2, wherein the weight ratio of the resin constituting the coating layer is 10 wt% or less.