JPH01195456A - Developer - Google Patents

Abstract

PURPOSE:To obtain a developer which does not absorb moisture even in high- humidity environment by using a toner which is low in the change rate of the conductivity of water after dispersion with respect to the conductivity of water before dispersion. CONSTITUTION:The toner (a) is further carried by rotation of a developing roller 18 and is brought near to a photosensitive drum 2, where the toner (a) is transferred from the roller 18 onto the drum 2 and the electrostatic latent image on the drum 2 is developed. The toner image is thus formed. This toner image is transferred to paper (p) by a transfer charger 6 and is then melted by a heater roller 8, by which the image is fixed onto the paper p. The toner does not absorb moisture even in the high-humidity environment when the toner contains less hydrophilic ions on or within the same, i.e., when the toner having 1<alpha<100 (wherein alpha is a change rate of the conductivity of water after dispersion to that before dispersion when the toner is dispersed in the water) is used. The good electrostatic charge quantity and image are thereby maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developer, and more particularly to an improved developer for use in an electrophotographic device.

(Prior Art) In an electrophotographic device or an electrostatic recording device, as a developing method for visualizing an electrostatic latent image formed on the surface of an electrostatic image carrier made of a photoreceptor, a dielectric material, etc. A two-component developing method using a developer consisting of toner and carrier is widely used as a developing method with good image quality. On the other hand, various development methods using a one-component developer consisting only of toner have also been proposed.

However, the toners used in these development methods have hygroscopic properties themselves, and hygroscopic substances tend to adhere to the surface, so the toner absorbs moisture depending on the humidity, causing high humidity. Under environmental conditions, this results in a decrease in image density and an increase in background fog. Further, even if good image quality is obtained in a high humidity environment at the initial stage of use, the toner often absorbs moisture during a life test and the image quality deteriorates. In this case, a great deal of effort and time is required to check the moisture resistance in order to select a toner with excellent moisture resistance.

In addition, instead of toner manufactured by conventional pulverization method,
Toners made by carrying out polymerization reactions in an aqueous phase are beginning to be used. However, since this type of toner is originally manufactured in an aqueous phase, hydrophilic substances tend to adhere or remain on the surface, making moisture resistance a particular problem.

(Problem to be Solved by the Invention WrJ) As described above, according to the conventional image forming method, an image of excellent quality could not be obtained due to the hygroscopicity of the toner used in the developer.

The present invention was made to solve the above problems, and an object of the present invention is to provide a developer that makes it possible to obtain images of excellent quality.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an electrostatic image carrier that holds an electrostatic latent image on its surface;
The electrostatic latent image on the surface of the electrostatic image carrier is removed by arranging a developer carrier carrying a developer on its surface at a certain interval and transferring the developer to the electrostatic image carrier. This developer relates to a developer used in a visualizing image forming method, and when this developer is dispersed in water, the rate of change α in the conductivity of water after dispersion relative to the conductivity of water before dispersion is 1.
<α<100.

In addition, in this specification, the electrical conductivity of water is the value obtained by measuring at 25 degreeC with the electrical conductivity meter (manufactured by Itaba Manufacturing Co., Ltd.: DS-8F).

Also, the rate of change α in the conductivity before and after dispersing the toner in water is
The conductivity of the supernatant liquid after dispersing 5% by weight of toner in ion-exchanged water with a conductivity of σ1 and boiling this dispersion is the conductivity of a supernatant liquid of σ2.
was measured and calculated using the following formula.

α-(σ2-σl)/σ1 A styrene-acrylic-aminomethacrylic copolymer is suitable as the resin component of the toner used in the present invention.

As the acrylic component or methacrylic component used in the synthesis of the above copolymer, conventionally known acrylic acid and derivatives thereof, and methacrylic acid and derivatives thereof can be used.

Examples of acrylic acid derivatives include acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, and octyl acrylate; Examples include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, and octyl methacrylate.

Furthermore, as a monomer having an amino group, a methacrylic acid derivative represented by the following general formula can be used in the synthesis of the above copolymer.

＼HR4 (In the formula, R1, R2, R3, and R4 all have 1 or more carbon atoms.
8 alkyl group. ) Monomers having an amino group represented by the above general formula include 2-dimethylamino-2-methylpropyl methacrylate, 2-dimethylamino-2-ethylbutyl methacrylate, and 2-dimethylamino-2-propylhexyl methacrylate. , 2-diethylamino-2-methylpropyl methacrylate, 2-diethylamino-2-ethylbutyl methacrylate, 2-diethylamino-2-propylhexyl methacrylate, and the like.

In addition, as a polymerization initiator for copolymerizing a monomer having an amino group to a styrene-acrylic copolymer or a styrene-methacrylic copolymer, azobis 2-(isobutyronitrile), azobis 2-(2 A nitrile initiator typified by -naphthyl)propylonitrile and the like can be used.

The toner colorants used in the present invention include carbon black, Fast Yellow G, benzidine yellow, pigment yellow, Indofast, orange,
Irgazin Red, Carmine FB, Permanent Bordeaux FRR, Pigment Orange R1 Resole Red 2
Known coloring agents such as G, Lake Relado C10-Damine FB, Rhodamine B Lake, Phthalocyanine Blue, Pigment Blue, Brilliant Green B1 Phthalocyanine Green, Quinacridone, etc. can be used.

(Function) The reason why the toner absorbs moisture is thought to be due to the presence of hydrophilic ions on or inside the toner. That is, when a toner is dispersed in water, if hydrophilic ions are present on or inside the toner, the hydrophilic ions seep into the water, and the conductivity of the water changes significantly. When such a toner is used, hydrophilic ions attract moisture in the air in a high humidity environment, and as a result, the toner absorbs moisture and the band 11
5 m, resulting in a decrease in image density and an increase in background fog. On the other hand, when there are few hydrophilic ions on the surface or inside of the toner, that is, when the toner is dispersed in water, the rate of change α in the conductivity of water after dispersion relative to the conductivity of water before dispersion is 1<α When using a toner with a molecular weight of <100, the toner does not absorb moisture even in a high humidity environment, and therefore a good charge amount and image can be maintained.

Note that the present invention is applicable not only to non-magnetic component developers but also to magnetic-component developers.
It is equally applicable to component and two-component developers.

(Example) Hereinafter, the present invention will be explained more specifically by showing examples of the present invention.

First, an image forming apparatus for performing development using the developer of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view showing an image forming apparatus for performing development using the developer of the present invention. In FIG. 1, reference numeral 2 indicates a photosensitive drum (image carrier) that rotates in a predetermined direction. An electrostatic latent image is formed on the surface of the photosensitive drum 2 by a charging device and an exposure device (not shown). Furthermore, a developing device 4, a transfer charger 6, and a heat roller (fixing means) 8 are provided around the photosensitive drum 2. The developing device 4 has a container 10, and an opening 12 is formed in a portion of the container 10 that faces the photosensitive drum 2. Inside this container 10, there are a storage section 14, an agitator 16, a developing roller (toner carrier) 18, a supply roller 20, and a coating blade (frictional charging member).
22 are provided. Toner a is supplied to the storage portion 14 through an openable lid 24 . The stirrer 16 is connected to the housing section 14
The supply roller 20 is for stirring the toner inside.
The toner a stirred by the agitator 16 is supplied to the surface of the developing roller 18. The coating blade 22 is a suppressing member made of an elastic material, and forms a toner layer by pressing the toner a supplied to the surface of the developing roller 18, and also triboelectrically charges the toner.

This blade 22 is supported on the inner wall of the container 10 by a holder 26. In addition, the pressing force of this blade is
The pressing force adjustment member 28 adjusts the pressure to 20 to 200 g/cm.

The developing roller 18 transports the toner a layer-formed and frictionally charged by the coating blade 22, brings it close to the electrostatic latent image on the photoreceptor drum 2, and transfers it. Also,
A bias voltage from a bias power source 30 is applied between the developing roller 18 and the photosensitive drum 2. Note that reference numeral 32 is a conveyance path for the paper (image support) p that passes between the photosensitive drum 2 and the transfer charger 6 and through the heat roller 8.

The toner a is further conveyed by the rotation of the developing roller 18 and approaches the photosensitive drum 2 . At this position, the toner
The toner image is transferred from the developing roller 18 to the photoreceptor drum 2, whereby the electrostatic latent image on the photoreceptor drum 2-L is visualized and a toner image is formed.

This toner image is transferred onto the paper p by the transfer charger 6, then melted by the heat roller 8 and fixed onto the paper p.

Next, a toner according to the present invention was manufactured as follows. In addition, the blending amount "parts" is "parts by weight".

Styrene-n-butyl methacrylate [glass transition point T
gnia 2. O℃, Softening point: 122℃ (R&R method), Number average molecular weight: 79,300, Polymerization average molecular weight: 181,00
0] 92 parts, carbon black 4 parts, wax 3 parts,
and charge control agent (E82: manufactured by Orient Chemical Co., Ltd.) 2
The mixture was premixed in a ball mill for about 2 hours and then kneaded in a pressurized niegu for about 1 hour.

Next, after cooling this mixed material, it was coarsely pulverized using a hammer mill, then finely pulverized using a jet mill, and the pulverized material was classified using an air classification method to obtain a toner having a size of 5 to 25 μm.

Thereafter, 100 parts of this toner and colloidal fine particles (R-
972 (manufactured by Nippon Aerosil Co., Ltd.) in a ball mill to adhere colloidal fine particles to the surface of the toner particles.
The component toner was obtained.

The conductivity of water after dispersing this toner in water was measured and was found to be 52.5 μS/am.

The rate of change α in the conductivity of water after dispersion with respect to the conductivity of water before dispersion was a value satisfying 1×α<100.

When this toner was supplied to the above-mentioned image forming apparatus and developed, a clear image without development fog was obtained.

Similarly, high temperature (30℃) and high humidity (85%RH)
) There was no development fog when the image was developed under the following environment.
No decrease in image density was observed, and a clear image with good transfer efficiency was obtained.

Further, when this image was fixed using a heat roll fixing device, both fixing and offset were good in the range of 170 to 220° C., and images of the same quality were obtained even after fixing 10,000 sheets.

Next, as a comparative example, a nonmagnetic component toner having a 50% weight average particle size of 11.5 μm was obtained in the same manner as in the above Example except that 5 parts of dodecylbenzenesulfonic acid was added as a dispersant.

When the conductivity of water after dispersing this toner in water was measured, it was 143 μS/cm, and the rate of change α in the conductivity of water after dispersion with respect to the conductivity of water before dispersion was 118. .

This toner is supplied to the above-mentioned image forming apparatus and is heated to 30°C.
When development was carried out under a high humidity (85% RH) environment, development fog occurred and an unclear image was obtained.

[Effects of the Invention] As explained above, when the developer of the present invention is dispersed in water, the rate of change α in the conductivity of water after dispersion with respect to the conductivity of water before dispersion is 1<α. Since it is <100, it does not absorb moisture even in a high humidity environment, and therefore, when the developer of the present invention is used, good images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an image forming apparatus used in an embodiment of the present invention. 2... Photosensitive drum, 4... Developing device, 6... Transfer charger, 8... Heat roller, 10... Container,
DESCRIPTION OF SYMBOLS 12... Opening, 14... Storage part, 16... Stirrer, 18... Developing roller, 20... Supply roller, 22
...Coated blade. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] An electrostatic image carrier that holds an electrostatic latent image on its surface and a developer carrier that carries a developer on its surface are arranged at a constant interval, and the developer is transferred to the electrostatic image carrier. A developer used in an image forming method for visualizing an electrostatic latent image on the surface of an electrostatic image carrier by dispersing the electrostatic latent image on the surface of the electrostatic image carrier, wherein when dispersed in water, the conductivity of the water after dispersion is lower than the conductivity of the water before dispersion. A developer characterized in that the rate of change α is 1<α<100.