JPH0827555B2 - Development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention provides a visible electrostatic latent image formed on a photoconductor or a dielectric in an electrophotographic apparatus or an electrostatic recording apparatus. The present invention relates to a developing method for forming an image.

(Prior Art) In an electrophotographic apparatus or an electrostatic recording apparatus, a toner is conventionally used in order to visualize an electrostatic latent image formed on an electrostatic image holding member made of a photoconductor, a dielectric or the like. A two-component developing method comprising a carrier is widely used as a developing method with good image quality.

However, while this two-component developing method has the above advantages, it has the following drawbacks.

The toner receives a triboelectric charge due to mutual friction between the toner and the carrier, but if it is used for a long period of time, the carrier surface is contaminated by the composition of the toner, and it becomes impossible to acquire a sufficient charge.

It is necessary to adjust the mixing ratio of the toner and the carrier within a predetermined range, but if it is used for a long period of time, the mixing ratio fluctuates and deviates from the predetermined range, and good development cannot be obtained.

In general, iron powder or glass beads whose surface is oxidized is often used as a carrier, but the carrier mechanically damages the surface of the photoconductor and shortens the life.

Therefore, various developing methods using a single-component toner composed of only toner have been proposed. In particular, many developing methods using a toner called magnetic toner containing magnetic powder have been proposed, among them, those based on U.S. Pat.Nos. 3909258 and 4121931 have been put into practical use. .

However, these methods also have the following drawbacks. That is, since a magnetic toner having a relatively low specific resistance is used, it is difficult to electrostatically transfer the developed image on the electrostatic latent image to a supporting member such as plain paper. I can't get a transcription.

Since the toner contains a large amount of magnetic powder, a color toner other than dark color cannot be obtained.

For this reason, recently, there has been proposed a developing method using a one-component toner which does not contain magnetic powder and has a large specific resistance, which has been conventionally used in the two-component developing method.

As such a developing method, for example, US Pat.
No. 847, No. 3152012, Japanese Patent Publication No. 41-9475, No. 45-2877
No. 54-3624, etc., touchdown method,
Those based on the impression method and the jumping method can be given.

However, when the toner used in the two-component developing method is used in such a one-component developing method, various problems occur as described below.

First, when such a method is used, there is a problem that the amount of triboelectric charging is insufficient.

Generally, in the one-component developing method, the toner is charged efficiently with the toner carrier and in a very short time, so that the electrostatic latent image formed on the photosensitive drum or the dielectric is visualized in a non-contact manner. It is necessary to obtain a sufficient charge amount (for example, about −0.5 to 15 μC / g when a selenium photosensitive drum is used).

However, there is a problem in that the triboelectric charging between the toner used in the conventional two-component developing method and the toner carrier does not provide a sufficient charge amount for visualizing. That is, in the conventional two-component developing method, the triboelectrification of the toner and the carrier is carried out for a sufficient time in order to obtain the amount of charge necessary to form a visible image. In the triboelectrification of the toner and the toner carrier in (3), the triboelectrification time is short, and the amount of charge required to form a visible image cannot be obtained.

Secondly, it is necessary to apply the toner very thinly and evenly on the surface of the toner carrier, but the toner used in the two-component developing method has a problem that it is difficult to form such a thin layer.

An example of the process of forming this thin layer will be described with reference to the sectional views of the drawings. In the figure, the elastic blade 2 is attached to the toner carrier 1.
While being pressed against each other at a pressure of 20 g / cm to 500 g / cm, the toner 4 in the toner container 3 is conveyed by the rotation of the toner carrier 1,
The elastic blade 2 coats the surface of the toner carrier 1 very thinly and evenly. Therefore, the toner 6 is required to have good fluidity and aggregation resistance.

However, the toner 4 in the toner container 3 often becomes cohesive and soul-like during the process of being conveyed by the rotation of the toner carrier 1, and the toner is not applied to the surface of the toner carrier 1. there were.

In addition, the toner 4 conveyed by the toner carrier 1
Due to the surface pressure between the elastic blade 2 and the toner carrier 1, abruptly high pressure is applied to these contact portions, so that frictional heat is generated and the toner 4 is softened and the surface of the toner carrier 1 is exposed. There is a problem in that the toner adheres and the toner is not applied evenly and thinly.

Further, when the softening point becomes high, the fixing temperature becomes high, and there is a problem that it is difficult to use it in a normal office copying machine.

Third, most of the toner composition is filled with the resin, and the proportion of the resin present on the surface of the toner is very large. Therefore, the resin that is negatively charged by friction with the elastic blade becomes positively charged toner. When used, a reverse polarity is generated due to charges generated on the toner particle surface between the toner particles, between the toner and the toner carrier, between the toner and the elastic blade, and troubles such as development fog and toner scattering are likely to occur. There is a problem.

These problems appear when a large number of copies are piled up, and therefore the conventional developing method using a one-component toner is substantially unsuitable for use in a copying machine.

(Problems to be Solved by the Invention) As described above, the conventional developing method has a problem that the advantages of the non-magnetic one-component toner cannot be fully utilized, and it is particularly difficult to control the triboelectric charge. It was

The present invention has been made to solve these problems, solves the above-mentioned various problems, uniformly forms a thin toner layer on a toner carrier, and has a stable triboelectric charge amount and a triboelectric charge amount distribution. It is sharp and uniform, does not cause development fog, is faithful to the electrostatic latent image, and is capable of visualizing the electrostatic latent image with high quality without causing toner scattering around the edges of the latent image. An object is to provide a developing method using a component toner.

[Structure of the Invention] (Means for Solving Problems) In order to solve the above problems, the present invention provides an electrostatic latent image holding member for holding an electrostatic latent image on the surface and a non-magnetic one-component toner on the surface. The non-magnetic one-component toner is applied onto the toner carrier, and the toner is transferred to the electrostatic latent image carrier and the static latent image carrier is transferred to the toner carrier. In a developing method for visualizing an electrostatic latent image on the surface of an electrostatic latent image carrier, the non-magnetic one-component toner is a positively charged non-magnetic one-component toner containing at least a resin and a colorant, and the resin is a glass. Transition point is 50 ℃ or higher, Softening point is 110 ℃ ～ 160
+25 to 150 μC plus the amount of triboelectrification charge for surface area
It is assumed that the resin is only / m ² .

Here, the triboelectric charge amount relative to the surface area means that the resin is pulverized and classified into 5 to 25 μm, and the 50% weight average particle diameter is 9
Resin made up to ~ 15μm, iron oxide powder (TE
FV: Nippon Iron Powder Co., Ltd.) 3% by weight, and this was sprayed onto a 400-mesh conductor net with 1 kg / cm ² of N ₂ gas, followed by blow-off method (TB-200: Toshiba Chemical Co., Ltd.) It is a value obtained by dividing the charge amount measured for a minute by the surface area measured by the BET method.

If the glass transition point of the resin used as the positively charged non-magnetic one-component toner is less than 50 ° C, the storage stability will be poor, and if the softening point is less than 110 ° C, offset will occur.
If it exceeds ℃, it will not fix.

If the triboelectric charge amount of this resin is less than plus 25 μC / m ² , it becomes difficult to charge, and if it exceeds plus 150 μC / m ² , it is difficult to form an image on the electrostatic image carrier.

Therefore, the resin used as the positively charged non-magnetic one-component toner of the present invention has a glass transition point of 50 ° C. or higher and a softening point of
110 ℃ ~ 160 ℃, plus the amount of triboelectric charge on the surface area
Especially frictional charge amount must be 25~150μC / m ² is desirably positive 50~120μC / m ^2.

Further, any resin can be used as long as this condition is satisfied.

That is, as the resin of the present invention, if the above-mentioned conditions are satisfied, for example, polystyrene and copolymers, polyesters and copolymers, polyethylene and copolymers, acrylate and methacrylate resins and copolymers, silicone resins, polypropylene and Copolymer,
Wax, polyamide resin, polyurethane resin and the like can be used alone or in combination.

Examples of the colorant used in the present invention include carbon black, fast yellow G, benzidine yellow, pigment yellow, indo first, orange, irgadine red, carmine FB, permanent porcelain FRR, pigment orange R and resole red 2.
Known colorants such as G, lake red C, rhodamine FB, rhodamine B lake, phthalocyanine blue, pigment blue, brilliant green B, phthalocyanine green, and quinacridone can be used.

Further, a wax may be added to the positively charged non-magnetic single-component toner of the present invention, if necessary, in order to improve anti-offset characteristics.

It should be noted that the positively charged non-magnetic one-component toner of the present invention contains a hydrophobic colloid having the same polarity as that of the toner, such as colloidal silica, in order to improve the fluidity and aggregation resistance of the toner, if necessary. The fine particles may be added in an amount that does not affect the charge amount of the toner, for example, 0.05 to 5 parts by weight.

(Operation) Next, a developing process to which the present invention is applied will be described with reference to the drawings.

As shown, the electrostatic image carrier 5 is rotated in the direction of the arrow. In the developing section, the toner carrier 1 rotates so as to move in the same direction as the surface of the electrostatic image carrier 5, and the one-component non-magnetic toner 4 sent from the toner container 3 is pressed onto the toner carrier 1. The elastic blade 2 is applied thinly and uniformly on the toner carrier, and friction between the toner carrier and the elastic blade and the toner imparts a charge having a polarity opposite to the electrostatic image charge to the toner particles.

At this time, in the developing section, a DC bias or an AC bias or a bias in which DC and AC are superposed may be applied between the toner carrier 1 and the surface of the electrostatic image carrier 5.

(Example) Next, the Example of this invention is described.

 The parts in the following examples are parts by weight.

Example 1 Styrene 85 parts n-Butylmethacrylate 10 parts Diethylaminoethylmethacrylate 5 parts Azobisisobutyronitrile 8 parts The above mixture is stirred at 65 ° C. for 6 hours to give a glass transition point of 72.0.
℃, softening point 122 ℃ (R & B method), triboelectric charge amount 69.1μC
/ m ^2, to obtain a number-average molecular weight 9,300, styrene -n-butyl methacrylate diethylaminoethyl methacrylate resin having a weight average molecular weight 181,000.

Next, 95 parts of the resin obtained above, 4 parts of carbon black, and 1 part of wax were premixed in a ball mill for about 2 hours, and then kneaded in a pressure kneader for about 1 hour.

Next, after cooling this kneaded product, coarsely crushed with a hammer mill,
It was finely pulverized with a jet mill, and the pulverized product was classified by a wind classification method to obtain a toner having a particle size of 5 to 25 μm.

Then, 100 parts by weight of this toner and 0.5 part by weight of positively charged colloidal fine particles (RA-200: manufactured by Nippon Aerosil Co., Ltd.) are mixed by a ball mill and adhered to the surface of the colloidal fine particles to obtain 50% weight average particle. A one-component non-magnetic toner having a diameter of 13.2 μm was obtained.

The triboelectric charge amount of this toner measured by the blow-off method was plus 28.5 μC / m ² .

Next, a commercially available copying machine (trade name: Rhodry 3301 manufactured by Toshiba Corp.) modified so that a negatively chargeable OPC photoconductor can be installed.
The above-mentioned one-component non-magnetic toner was supplied to the apparatus shown in the drawing for development, and a clear image free from development fog was obtained.

Further, even in a high temperature and high humidity (30 ° C., 85% RH) environment, there was no development fog and there was no reduction in image density, and clear images with good transfer efficiency were obtained.

Further, a clear image with high density was obtained even in an environment of low temperature and low humidity (5 ° C., 10% RH).

Furthermore, when fixed with a heat roll fixing device, 170 ° C
From the beginning, fixing did not occur, and offset did not occur even at 220 ° C.

Example 2 90 parts of bisphenol type polyester having a number average molecular weight of 4,100 and a weight average molecular weight of 32,000, and a number average molecular weight of 30,000,
A high amine value styrene-diethylaminomethacrylate resin with a weight average molecular weight of 60,000 and an amine value of 178 mg / KOHg (10 g) was kneaded with three rolls, and the glass transition point was 82.5 ° C and the softening point was 13
A resin having a triboelectric charge amount of 87.5 μC / m ² at 5 ° C. was obtained.

Then, the same procedure as in Example 1 was carried out except that 95 parts of the mixed resin obtained above was used in place of the styrene-n-butyl methacrylate-diethylaminomethacrylate resin of Example 1, and there was no development fog and there was no static. A clear image without toner scattering around the edge of the latent image was obtained.

The 50% weight average particle diameter of this toner was 12.3 μm, and the triboelectric charge amount was plus 31.5 μC / m ² .

[Advantage of the Invention] According to the developing method of the present invention configured as described above, the developing system in which the triboelectric charge amount between the toner and the elastic blade or between the toner and the toner carrier is stable and is used It is possible to control the charge amount suitable for the above, and therefore, the development fog and the toner scattering around the edge of the latent image, which could not be solved sufficiently in the past, are eliminated, and a high image density can be obtained.

Furthermore, even when the toner is used continuously for a long period of time, the initial characteristics can be maintained, high-quality images can be used for a long period of time, and the friction of the toner when used under high-temperature high-humidity or low-temperature low-humidity environmental conditions. The charge amount is stable and hardly changes at room temperature and normal humidity, there is no development fog or reduction in image density, and it is possible to perform development faithful to the latent image.
Also, the transfer efficiency is excellent.

[Brief description of drawings]

The drawing is a cross-sectional view schematically showing a main part of a developing device for a one-component developing method. 1 ... toner carrier 2 ... elastic blade 3 ... toner container 4 ... toner 5 ... electrostatic image carrier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Uehara 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute, Inc. (56) Reference JP-A-61-28957 (JP, A) JP 61-57854 (JP, A) JP-A-60-3648 (JP, A) JP-A 61-109066 (JP, A) JP-A 61-198247 (JP, A) JP-A 61-198248 (JP , A)

Claims (2)

[Claims] 1. An electrostatic latent image carrier that holds an electrostatic latent image on the surface and a toner carrier that carries a non-magnetic one-component toner on the surface are arranged at a constant interval, and the non-magnetic one In the developing method, the component toner is applied onto the toner carrier, and the toner is transferred to the electrostatic latent image carrier to visualize the electrostatic latent image on the surface of the electrostatic latent image carrier. The component toner is a positively charged non-magnetic one-component toner containing at least a resin and a colorant, and the resin has a glass transition point of 50 ° C. or higher and a softening point of 110 ° C. to 160 ° C.
+25 to 150 μC plus the amount of triboelectrification charge for surface area
A developing method characterized in that only a resin having a density of / m ² is used. 2. The developing method according to claim 1, wherein the non-magnetic one-component toner contains 0.05 to 5 parts by weight of positively charged colloidal silica.