JPS63200159A - Developing agent - Google Patents

Abstract

PURPOSE:To stabilize electric charge of a toner even in a wide range of temp. and humidity and to maintain satisfactory quality of a picture image by providing a coating layer comprising 1-20wt.% Sb and residual wt.% tin oxide on the surface of TiO2 powder. CONSTITUTION:A developing agent comprising toner particles, carrier, and fine electroconductive powder is provided wherein the fine electroconductive powder consists of fine TiO2 powder having >=10m<2>/g specific surface area and coated with 10-70wt.% coating layer on the surface of the TiO2 particles, and said coating layer consists of 1-20wt.% Sb and residual wt.% tin oxide. Sticking and accumulation of toner on the surface of the carrier is inhibited in this developing agent even after using for a long time, so a satisfactory picture image as good as a picture image in the initial stage is obtd. Moreover, satisfactory picture images of high density are obtd. in all environmental conditions such as at low temp.-low humidity circumstance, or high temp.-high humidity circumstance, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a developer for magnetic brush development.

[Prior Art] In electrophotography, an image is formed on a photoconductive material using electrostatic means, and when a developer consisting of toner and carrier is supplied to this electrostatic latent image, an electric charge is generated. The toner having a . As a method for developing an electrostatic latent image using such toner and carrier, there is a magnetic brush development method disclosed in US Pat. No. 2,874,063.

In such a developing method, toner particles are held on the surface of carrier particles having a larger particle size than the toner particles by electrostatic force. The electrostatic force is caused by toner particles and carrier particles coming into contact and generating frictional charges of opposite polarity. The toner particles must have the correct polarity and charge so that they are selectively attracted to the electrostatic latent image when they contact the latent image.

In conventional dry type developers, toner adheres and accumulates on the carrier surface during long-term use.

The normal triboelectric charging of a pair of toners and a carrier is partially replaced by a relationship of one toner and a toner, and the amount of triboelectrification of the toner changes over time, resulting in a reduction in the quality of the copied image. Further, the amount of frictional charge between the toner pair and the carrier was not stable due to the temperature and humidity conditions, resulting in a decrease in image density and fogging, which was not satisfactory.

As a method to solve these problems, a method of coating the carrier surface with various resins has been proposed, but carriers coated with resin have high resistance, resulting in strong edge effects and uneven solid areas. , and because it is difficult to apply a bias potential, there are problems in that the background portion is likely to be fogged.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned conventional problems, and to prevent toner from adhering and accumulating on the carrier surface even during long-term durability, and to prevent toner from adhering to and accumulating on the carrier surface, and to be able to withstand a wide range of temperature and humidity conditions. However, it is an object of the present invention to provide a developer that can stabilize the chargeability of toner and maintain good image quality.

[Means and effects for solving the problems] According to the present invention, there is provided a developer comprising at least toner particles, a carrier, and a conductive fine powder, wherein the conductive fine powder has a specific surface area of 10 m2/ A developer having a coating layer of 10 to 70% by weight on the particle surface of fine titanium dioxide powder having a particle size of 1 to 20% by weight, and the coating layer consisting of 1 to 20% by weight of antimony and the balance of tin oxide. is provided.

In the present invention, titanium dioxide fine powder having a specific surface area of 10 m2/g or more is used. If it is less than 10 m2/g, sufficient effects as a conductive powder cannot be obtained, probably due to poor dispersion in the carrier and toner particles.

In addition, the coating layer on the particle surface of the titanium dioxide fine powder is 1-
The coating layer is composed of 20% by weight of antimony and the balance is tin oxide, but even if the antimony content is less than 1% by weight or exceeds 20% by weight, titanium dioxide conductivity is △. The particle surface of the titanium dioxide fine powder is coated with the titanium dioxide fine powder in an amount of 10 to 70% by weight of the conductive fine powder, but if the coating layer is less than 10% by weight, the effect as a conductive fine powder is lost. If it exceeds 70% by weight, it will cause a decrease in the density of one image.

Further, the conductive fine powder used in the present invention has a specific resistance of 10
It is preferable that the thickness is 40.0 layers or less, and 104Ω・cm
If it exceeds this value, it will no longer function as a conductive fine powder.
It becomes impossible to stably maintain the chargeability of the toner.

The conductive fine powder is preferably added in an amount of 0.1 to 5% by weight based on the weight of the toner, and is effective when the amount of the conductive fine powder is less than 0.1% by weight based on the weight of the toner. On the other hand, if it exceeds 5% by weight, the triboelectric charging properties between the toner and the carrier will be inhibited, resulting in a foggy image, which is not preferable.

The method of coating the fine titanium dioxide powder with the above material may be a spray method, CVO method, sputtering method, or vapor deposition method, but from the viewpoint of cost and operability, the method described in JP-A-58-2
09003, by simultaneously adding a dilute aqueous hydrochloric acid solution containing tin chloride and antimony chloride and aqueous ammonia to a heated suspension of fine titanium dioxide powder while controlling the pH of the suspension. More preferred is a method in which a hydration reaction product of tin and titanium dioxide is deposited on the surface of titanium dioxide.

Examples of carrier particles used in the present invention include iron,
Metals such as nickel, cobalt, manganese, chromium, rare earths, alloys or oxides thereof, etc. can be used. Moreover, there are no special restrictions on the manufacturing method. In order to control the ability to impart charge to the toner, the carrier particles may be further coated with a resin or the like, and the coating may be applied by dissolving or suspending the resin or other coating material in a solvent. Any conventionally known method can be applied, such as a method of adhering the powder to a powder, or a method of simply mixing powder.

Substances that adhere to the carrier surface vary depending on the toner material, but include, for example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, di-t-butyl salicylic metal complex, and styrene resin. , acrylic resin, polyacid, polyvinyl butyral, nigrosine,
Amine acrylate resin, basic dye and its lake.

It is appropriate to use fine silica powder, fine alumina powder, etc. alone or in combination, but the invention is not necessarily limited to this.

The amount of the above-mentioned compound treated is generally 0.1 to 30% by weight (preferably 0.5 to 20% by weight) based on the carrier.
) is desirable.

The binder resin for toner used in the present invention includes monopolymers of styrene and its substituted products such as polystyrene, polyp-chlorostyrene, and polyvinyltoluene: styrene-
p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer.

Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer,
Styrene-butyl methacrylate copolymer, styrene-α
-Methyl chlormethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-
butadiene copolymer, styrene-imprene copolymer,
Styrenic copolymers such as styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene , polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin , paraffin wax, etc.
Can be used alone or in combination.

Further, any suitable pigment or dye can be used as a coloring agent. For example, there are known dyes and pigments such as carbon black, iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow.

In addition, as a charge control agent, amino compounds, quaternary ammonium compounds and organic dyes, especially basic dyes and their salts,
Benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin γ and crystal violet, metal-containing dyes, salicylic acid alloy compounds, etc. may be added, and furthermore, they may interfere with the effects of the present invention. Magnetic powder may be added to a certain extent.

The toner structure described above may be used for a toner produced by a commonly used mixing-pulverization method, or may be used for a wall material, a core material, or both of microcapsule toner.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that the parts shown below are parts by weight.

Example 1 Toner particles having an average particle size of 12 Bm were obtained.

On the other hand, conductive fine powder was obtained as follows using the manufacturing method disclosed in JP-A-58-209003 and JP-A-58-209002. Ti0z with specific surface area 30.1 layer 2/g
Stir and disperse 100g in pure water (2000mj) and heat to 7.
Heat and maintain at 0°C. Next, a separately prepared 2N HC
I! Aqueous solution 400 tons! Ci'n・5Hz023
A solution containing 20g of 0g and 5bCRs and NH3
The aqueous solution and the aqueous solution were simultaneously added dropwise over 1 hour so that the pH of the suspension was maintained at 8. After filtering and washing the product, it was heated to 500℃ for 2 hours.
A conductive fine powder was obtained by heat treatment for a period of time. The obtained white fine powder had a specific resistance of 250 Ω"am.

Next, 0.2% by weight of the obtained conductive fine powder was added to the toner particles. A developer was prepared by mixing 6 parts of toner containing conductive fine powder with 100 parts of spherical iron powder having an average particle size of 7.1.

Using this developer, NP-8500 machine (manufactured by Canon Co., Ltd.)
When I ran it for a long time, I was able to get an image as good as the initial one even after 10,000 sheets.

Furthermore, in all environments, the image reflection density was 23℃, 6
1645.15°C at 0% RH, 1.48 at 10% RH.
At 35° C. and 90% RH, it was as high as 1.42, and a clear image without fogging was obtained. Also, the toner charge amount at this time is the first
It was stable as shown in the table.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the conductive fine powder used in Example 1 was not added to the toner particles, but the image density decreased with the number of durable sheets and blurring also occurred. . Another 15℃.

In a low temperature, low humidity environment of 10% RH, soil burrs were noticeable from the beginning. Further, the toner charge amount at this time changed significantly due to environmental changes as shown in Table 1.

Comparative Example 2.3 Instead of the conductive fine powder used in Example 1, TiO2 fine powder (specific surface area 30.1/g, specific resistance 3.5X10
6Ω・cm), Sr+O2 fine powder (specific surface area 15
m2/g, specific resistance? .

(Margin below) Example 2 Toner particles having an average particle size of 11 pm were obtained.

Next, 0.1% by weight of the conductive fine powder obtained in Example 1 was added to the toner. A developer was prepared by mixing 6 parts of toner with conductive fine powder added to 100 parts of ferrite particles coated with silicone resin and having an average particle size of 60 gm. Using this developer, MP-850 was prepared in the same manner as in Example 1.
After long-term endurance with 0 aircraft (4 cannons),
Even after 100,000 sheets of durability, images as good as the initial images were obtained.

Next, a method for measuring the amount of triboelectric charge in the present invention will be described.

FIG. 1 is an explanatory diagram of a frictional charge amount measuring device.

A metal measurement container 12 with a conductive screen 13 of 400 meshes (can be changed as appropriate to a size that does not allow magnetic particles to pass through) at the bottom is filled with the toner whose triboelectric charge is to be measured or the surface treatment substance for the magnetic particles. , amorphous iron powder with a particle size between 200 and 300 mesh (EFV 20 manufactured by Nippon Iron Powder)
0/300; The surface is untreated and is similar to the toner carrier.
Approximately 4 g of a mixture (developer) with a weight ratio of 1:9 (which has virtually no triboelectric charging properties) is put therein, and a metal lid 14 is placed on top. At this time, the weight of the entire measurement container 2 is taken as L (g).
Next, in the suction device 11 (at least the portion in contact with the measurement container 2 is an insulator), suction is performed from the suction port 17 and the air volume control valve 16 is adjusted to set the pressure of the vacuum gauge 15 to 70 layers Hg. In this state, suction is applied sufficiently (for about 1 minute) to suction and remove the surface treatment substance of the toner or magnetic particles. The potential of the electrometer 19 at this time is assumed to be V (volt).

Here, 18 is a condenser whose capacity is C (tF), and the weight of the entire measurement container after suction is weighed W2 (g
). This triboelectric charge amount T (pc/g) is calculated as shown in the following formula.

FIG. 2 is an explanatory diagram schematically showing an example of a measuring device for measuring specific resistance. - As for the measurement conditions, the thickness of the sample 2 was set to [■], the current value when the DC power source 4 was connected was read by the ammeter 5, and the specific resistance was determined using the following calculation formula.

(Sample thickness d, electrode area S, applied voltage ■.

Current value after 1 minute) [Effects of the invention] As described above, the developer of the present invention does not adhere or accumulate toner on the carrier surface even after long-term durability, and it is possible to obtain images as good as the initial one. . In addition, good images with high density can be obtained in all environments, including low temperature and low humidity, high temperature and high humidity.

[Brief explanation of the drawing]

Figure 1 shows the frictional charge amount measuring device used in the example,
The figure is a schematic diagram of an example measuring device for measuring specific resistance. DESCRIPTION OF SYMBOLS 11... Suction machine, 12... Measurement container, 13... Conductive screen, 14... Metal lid, 15...
Vacuum gauge, 16... Air volume control valve, 17... Suction port, 1
8... Capacitor, 19... Electrometer, 21...
electrode. 22... Sample, 23... Insulator, 24... DC power supply, 25... Ammeter, 26... Shield case.

Claims (1)

[Claims] A developer comprising at least toner particles, a carrier, and a conductive fine powder, wherein the conductive fine powder has a specific surface area of 10 to 70% by weight on the particle surface of a titanium dioxide fine powder having a specific surface area of 10 m^2/g or more. A developer comprising a coating layer, the coating layer comprising 1 to 20% by weight of antimony and the remainder tin oxide.