JPH0720657A - Developer - Google Patents

Abstract

PURPOSE:To provide a developer preventing the increase of the amt. of electric charges on a start developer, giving stable image density from the beginning of development and having stability to an environmental change. CONSTITUTION:A start developer fed into a developing unit and a developer for replenishing a consumed developer are used so as to satisfy the relation of y<x [where (x) is the amt. (g/cm<3>) of an electric charge controlling agent exposed to the surfaces of toner particles used in the start developer and (y) is the amt. (g/cm<3>) of an electric charge controlling agent exposed to the surfaces of toner particles used in the developer for replenishment].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer, and more particularly to a start developer and a replenishment developer supplied to a developing device of a copying machine.

[0002]

2. Description of the Related Art In electrophotographic copying, triboelectrically charged toner electrostatically adheres to an electrostatic latent image on a photoconductor, and the toner is transferred and fixed on a copy paper to form a copied image. Therefore, the copying process always includes the process of frictionally charging the toner.

The triboelectrification property of the toner is determined by the replenishment of the developer at the initial stage of use of the developer (the developer used at this time is called "start developer") (the developer used at this time is referred to as "replenishment development"). After being treated as an agent, its properties change. This is, for example, 2 consisting of toner and carrier
This is because, in the case of the component developer, when the toner and the carrier are mixed and stirred, the charge characteristic of the carrier is significantly changed due to the spent of the toner component on the carrier surface, and the charge amount of the toner is greatly changed. More specifically, since the carrier in the start developer does not become spent due to the charge control agent (CCA) in the toner component, the toner tends to be excessively tribocharged. Even in the case of the one-component developer, the tendency is the same as that of the two-component developer, considering the toner friction with the blade instead of the carrier.

Particularly, in the case of the start developer, the toner charge amount increases in a room temperature and low humidity environment, the toner adhesion amount to the electrostatic latent image decreases, and the image density (ID) decreases. Further, in the case of a two-component developer, if the charge amount of the toner becomes high, the counter charge of the carrier also rises, and there is a problem that the carrier adheres to an unnecessary place in the image.

In order to prevent an increase in the initial charge amount of the starting developer as described above, there is known a technique of setting the mixing ratio (T / C ratio) of the toner to the carrier to 8 to 10%, which is higher than the usual 6%. However, it is difficult to maintain such a high T / C ratio, there is a large variation in the T / C ratio, and there is a problem that the image density is still reduced in a low humidity environment.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents an increase in the charge amount of the starting developer, provides a stable image density from the initial stage of development, and is stable to environmental changes. It is characterized in that a developer is provided.

[0007]

The above-mentioned object is to increase the amount of charge control agent (CCA) on the toner surface of the start developer, and to replenish the toner with the amount of surface exposed CCA less than that amount. It is achieved by using as.

That is, in the present invention, the exposed amount of the charge control agent exposed on the surface of the toner particles used for the starting developer supplied to the developing device is defined as x (g / cm ³ ), and the consumed developer is Development wherein the exposure amount of the charge control agent exposed on the surface of the toner particles used for the replenishing developer for replenishment is y (g / cm ³ ) and y <x Regarding agents.

The charge control agent of the toner for the starting developer is used with a surface exposure amount higher than that of the replenishment toner, and the charge control agent on the surface of the toner is used as a contact partner for triboelectric charging of the toner, for example, a carrier, Spent quickly with a blade. As a result, the toner charge amount can be prevented from increasing and the toner charge amount can be stabilized even if the environment changes. In particular, it is possible to prevent the charge amount from increasing in a low humidity environment, and to stabilize the image density.

The surface exposure amount of the charge control agent can be adjusted by changing the addition amount of the charge control agent. For example, when the toner is prepared by kneading and pulverizing, it can be adjusted by changing the kneading and pulverizing conditions. In this case, for example, when the fixing resin, the charge control agent and other additives are mixed in a short time, the surface exposure amount of the charge control agent can be increased. As another method, toner particles are prepared without adding a charge control agent, and then a hybridizer (manufactured by Nara Machinery Co., Ltd.)
It is also possible to make the adjustment by causing the charge control agent particles to collide with the toner surface in a high-speed air flow using the above, and fixing the charge control agent on the toner surface.

The exposure amount of the charge control agent exposed on the surface of the toner particles of the start developer is 1.0 × 10 ^{−6 to} 1.0.
× 10 ^-4 g / cm ³ , preferably 3.8 × 10 ^{-6 to} 3.8.
It is preferably set to ^{x10 -5} g / cm ³ . Further, the specific exposure amount should be appropriately set in consideration of the developing method, the type of charge control agent, the contact partner with the toner, and the like.

When the starting developer is consumed and the developer is replenished, the toner of the replenishing developer is used with the amount of the surface exposure charge control agent being smaller than that of the toner of the starting developer. . Even if the amount is small, the amount is almost the same as the amount of the toner of the commonly used developer exposed on the surface thereof. This is because at the stage of replenishing the developer, the charge control agent in the toner component is sufficiently spent as a contact partner for the triboelectric charging of the toner, and the chargeability is stable. This is because it is no longer necessary to increase the amount of surface exposure.

The amount of toner surface exposure of the charge control agent of the toner of the replenishing developer is specifically 1.0 × 10 ^{−8 to} 1.0 × 1.
0 ⁻⁵ g / cm ³ , preferably 3.8 × 10 ^{−8 to} 3.8 × 1
It is desirable to adjust to 0 ^-6 g / cm ³ .

In the present invention, the resin used for the toner may be any resin as long as it is generally used as a binder resin in the production of toner, for example polystyrene resin, Poly (meth) acrylic resin, polyolefin resin, polyamide resin,
Polycarbonate resin, polyether resin, polysulfone resin, polyester resin, epoxy resin,
Use of a thermoplastic resin such as a butadiene resin, a thermosetting resin such as a urea resin, a urethane resin, a urea resin, an epoxy resin, a copolymer thereof, a block polymer, a graft polymer or a polymer blend. You can The resin is not limited to a resin in a complete polymer state such as a thermoplastic resin, but may be an oligomer or prepolymer such as in a thermosetting resin, or a resin containing a crosslinking agent. It is possible.

When the toner contains an offset preventing agent, various waxes, particularly low molecular weight polypropylene, polyethylene, or polyolefin type waxes such as oxidized polypropylene and polyethylene are used as the offset preventing agent. It is preferably used.

Such a wax has a number average molecular weight Mn of 1,000 to 20,000 and a softening point T.
It is preferable to use one having m of 80 to 150 ° C. In addition, when the resin forming the core particles has a polar group, it is desirable to use a wax having a polar group from the viewpoint of compatibility. Further, in the present invention, since the toner is used as a magnetic toner, when the magnetic fine particles are contained in the toner, fine particles made of a known magnetic material can be used. For example, in the case of obtaining a black toner, Is black and magnetite (ferric tetroxide) that also has a function as a coloring agent can be used. When obtaining a color toner, use a material having a small black tint such as metallic iron. .

Typical examples of such magnetic materials include, for example, metals exhibiting ferromagnetism such as cobalt, iron and nickel, aluminum, cobalt, iron, lead, magnesium, nickel, zinc, antimony and beryllium. ,
Alloys of metals such as bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, mixtures thereof, oxides, fired bodies (ferrite)
It is possible to include fine particles of a known magnetic material such as.

In the present invention, the charge control agent used is
It may be any known charge control agent, for example,
As the charge control agent for positive charging, an azine compound nigrosine base EX, Bontron N-01, 02, 04, 0
5,07,09,10,13 (manufactured by Orient Chemical Industry Co., Ltd.), oil black (manufactured by Chuo Synthetic Chemical Company), quaternary ammonium salt P-51, polyamine compound P-52, Sudan Chief Schwarz BB (solvent black 3) :
C. I. No. 26150), Fetschwarz HBN
(C.I. No. 26150), Brilliant Spirits Schwarz TN (manufactured by Farben Fabriken Bayer), alkoxylated amines, alkylamides, molybdic acid chelate pigments, imidazole compounds and the like can be used, and negative As the charge control agent for charging, chromium complex salt type azo dyes S-32, 33, 34, 3
5, 37, 38, 40, 44 (manufactured by Orient Chemical Industry Co., Ltd.), Eisenspiron Black TRH, BHH (manufactured by Hodogaya Chemical Co., Ltd.), Kayaset Black T-22,004 (manufactured by Nippon Kayaku Co., Ltd.), aluminum complex salt E -86 (manufactured by Orient Chemical Industry Co., Ltd.), salicylic acid metal complex E-81 (manufactured by Orient Chemical Industry Co., Ltd.), calixarene compound and the like can be used.

Further, in the present invention, a fluidizing agent may be added to the toner in order to enhance its fluidity. Examples of such fluidizing agents include silica, aluminum oxide, titanium oxide and magnesium fluoride. Etc. can be used alone or in combination.

In the present invention, organic fine particles may be attached or fixed on the surface of the toner in order to improve the fluidity and cleaning property thereof. Examples of such organic fine particles include emulsion polymerization method. Styrene granulated by a wet polymerization method such as a non-aqueous dispersion polymerization method or a gas phase method
Various organic fine particles such as (meth) acryl, benzoguanamine, melamine, Teflon, silicon, polyethylene, polypropylene, acryl fluoride and vinylidene fluoride may be used alone or in combination.

Further, in the present invention, a one-component developer or a two-component developer obtained by mixing toner and a magnetic carrier can be used as the developer.

As the magnetic carrier that can be used in the present invention, a known magnetic carrier that has been generally used in the past can be used. For example, a carrier composed of magnetic material particles such as iron or ferrite, or a magnetic material particle can be used as a resin. It is possible to use a coated carrier coated with or the like, a binder type carrier in which magnetic material fine particles are dispersed in a binder resin, or the like.

When the amounts of the surface-exposed charge control agents of the toner for the starting developer and the toner for the replenishing developer are used in the above relationship, the toner / carrier mixing ratio (T / C ratio) is started in the case of the two-component developer. The same T / C ratio for the supply and the supply,
Moreover, a low T / C ratio of about 6% can be consistently applied from the start of initial development. The T / C ratio control becomes easy and the variation is eliminated.

In the present invention, the exposure amount of the charge control agent on the toner surface is represented by the number of grams per unit volume of the toner, and is calculated by the following equation (Equation 1).

[0025]

[Equation 1]

In the above (Equation 1), the weight (g) of the exposed charge control agent means the amount of the charge control agent exposed on the toner surface, and the value obtained as follows.

The toner is agitated and mixed in ethanol to elute the charge control agent exposed on the toner surface. Next, the absorbance of the solution is measured with a spectrophotometer, and the amount of the charge control agent in the solution is calculated from the measured value. The value calculated in this way is the weight of the exposure charge control agent.

The present invention will be further described below with reference to specific examples.

EXAMPLES Preparation of Microcarriers As magnetic carriers (microcarriers) used by mixing with toner, 100 parts by weight of polyester resin and Z
n-type ferrite (maximum magnetization: 68 emu / g, Hc: 1
10, volume specific electric resistance: 8.5 × 10 ⁷ Ω · cm) 5
00 parts by weight and 2 parts by weight of carbon black (MA # 8: manufactured by Mitsubishi Kasei Co., Ltd.) were sufficiently mixed and pulverized with a Henschel mixer. Next, the mixture was melt-kneaded by using an extrusion kneader set to a cylinder part 180 ° C. and a cylinder head part 170 ° C. This kneaded material was left to cool and then coarsely pulverized using a feather mill. Further, the coarsely pulverized product was finely pulverized with a jet mill and then classified with a classifier to obtain a carrier having an average particle size of 55 μm.

Preparation of toner for starter 100 parts by weight of thermoplastic styrene acrylic resin-Additive for offset prevention; 4 parts by weight of low molecular weight polypropylene-8 parts by weight of carbon black MA # 100 (manufactured by Mitsubishi Kasei) -Bontron N- 01 (Nigrosine dye, manufactured by Orient Chemical Industry Co., Ltd.) 4 parts by weight

The above materials were placed in a 10 liter Henschel mixer and mixed for 2 minutes at 2000 rpm. The mixture was continuously extruded and kneaded with a kneader PCM30 (1 / d: 32.5). Next, the kneaded product was cooled and coarsely pulverized, and the coarsely pulverized product was pulverized and classified by a jet pulverizer and a classifier to obtain toner particles having an average particle size of 13.5 μm.

The obtained toner particles have the charge control agent Bontron N-01 on the surface thereof in the range of 6.84 × 10 ^{−6 to} 7.60 × 10 ^−6.
g / cm ³ was exposed on the toner surface.

Preparation of Developer A developer was obtained by mixing the carrier and toner obtained above in a toner / carrier (T / C) ratio of 6%. 30 g of this developer was put into a 50 cc polybin and mixed.

The amount of the charge control agent Bontron N-01 deposited on the carrier surface (carrier spent amount) increased linearly until the 13th hour of mixing, and 1.04 × 1 after the 13th hour.
0 was ^-3% by weight constant.

The carrier spent amount is expressed as a weight percentage of a value obtained by dividing the weight of the charge control agent adhering to the surface of the carrier by the weight of the carrier itself. The amount of the charge control agent attached to the carrier surface is measured in the same manner as the measurement of the charge control agent exposed on the toner surface.

[0035]

Comparative Example Comparative Toner A conventional toner was prepared as a comparative toner. The same components, compositions, and conditions were used as in the preparation of the starting toner, except that the mixing conditions were 2000 rpm for 4 minutes.

The obtained toner has an average particle size of 13.5 μm, and the exposure amount of the charge control agent Bontron N-01 on the toner surface is 1.9 × 10 ^{−6 to} 3.8 × 10 ⁻⁶ g / cm 3. ^{Was 3} . Preparation of Developer The carrier prepared in Example and the comparative toner were mixed at a T / C ratio of 8% to obtain a developer. The mixing conditions are the same as in the example.

The amount of charge control agent Bontron N-01 deposited on the carrier surface (carrier spent amount) increased linearly up to the third hour of mixing, and was 0.19 × 10 ⁻³ after the third hour.
It became constant at weight%.

[0038]

[Evaluation] Using the developers of Examples and Comparative Examples, an initial printing durability test (0 to 1000 sheets) was performed under a low humidity environment (25 ° C, 10%) (N / L environment), and image density (ID ) Was measured. The results are shown in FIG. 1 (the vertical line represents the ID and the horizontal line represents the number of printed sheets).

In FIG. 1, the upper three broken lines show the results of the improved start toner, and the lower three broken lines show the results of the comparative start toner. The symbol "◇" in the figure
And “∇” indicate the results when the toner in the developing device near the toner supply port of the developing device is developed.
“□” and “Δ” indicate the results when the toner in the developing device located farthest from the toner supply port is developed. "+" And "x" are "◇" or "▽" and "□"
Alternatively, the result is shown in the case where the toner in the middle of the position of the toner in the developing device represented by “Δ” is developed.

As can be seen from FIG. 1, the developer of the example had a stable ID in a low-humidity environment, while the toner of the comparative example showed (+, □, ◇), ID was significantly different.

The above results indicate that the carrier of the developer of the embodiment is appropriately spent with the toner,
This shows that the carriers were not overactivated by each other, while the developers of the comparative examples showed that the carriers were not properly spent on the toner and the toner charge amount was unstable. .

[0042]

EFFECTS OF THE INVENTION The developer of the present invention does not increase the charge amount of the start developer and the ID decreases accordingly, and achieves a stable charge amount and ID even with environmental changes.

[Brief description of drawings]

FIG. 1 shows the relationship between the number of copies and the image density (ID).

Claims (1)

[Claims] 1. The consumed amount of the developer is replenished by setting the exposure amount of the charge control agent exposed on the surface of the toner particles used for the start developer supplied to the developing device as x (g / cm ³ ). The amount of exposure of the charge control agent exposed on the surface of the toner particles used in the replenishing developer is set to y (g / c
m ³ ) and used in the relationship of y <x.