JPH0160823B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developer used for visualizing an electrostatic latent image formed by electrophotography, electrostatic recording, electrostatic printing, or the like.

So-called two-component dry developers comprising a mixture of carrier particles and toner particles have been well known. In this two-component dry developer, minute toner particles are held on the surface of relatively large carrier particles by the electric force generated by friction between the two particles, and when brought close to an electrostatic latent image, the electrostatic latent image The attraction force against the toner particles in the direction of the latent image due to the electric field formed by the toner particles overcomes the bonding force between the toner particles and the carrier particles, and the toner particles are attracted to the electrostatic latent image and the electrostatic latent image is visualized. It is something that The developer is used repeatedly while replenishing the toner consumed by development.

Therefore, during long-term use, the carrier must constantly triboelectrically charge the toner particles to a desired polarity and sufficient amount of charge. However, with conventional developers, a toner film is formed on the carrier surface due to mechanical collisions such as collisions between particles or collisions between particles and the developing machine, or heat generated by these, resulting in so-called spent, and the charging characteristics of the carrier are used. It decreases over time, requiring the entire developer to be replaced.

In order to prevent such spent formation, methods of coating the carrier surface with various resins have been proposed, but no satisfactory method has yet been obtained. For example, carriers coated with resins such as styrene-methacrylate copolymers and styrene polymers have excellent charging properties, but the critical surface tension of their surfaces is relatively high, and spent is likely to occur during repeated copying. Therefore, its lifespan as a developer is not very long. In addition, since the carrier coated with tetrafluoroethylene polymer has a low surface tension, it is difficult for the toner to become spent, but since the tetrafluoroethylene polymer is located at the most negative side in the triboelectrification series, the toner is transferred to the negative electrode. It cannot be used when attempting to be charged sexually. It is also possible to coat toner particles with silicone resin as a material with low surface tension, but silicone resin is also located on the slightly negative side of the triboelectrification series, so carrier particles coated with silicone resin are used to coat toner particles with a negative charge. For example, it is difficult to charge the
No. 49-21151, No. 49-27229, and No. 52-67331 proposed conventional negative polarity control agents added to toner particles were not satisfactory.

Therefore, in Japanese Patent Application No. 56-76780, the present applicant proposed a method in which carrier particles coated with a silicone resin and toner particles containing a metal complex type monoazo dye as a polarity control agent were combined to provide sufficient negative charge to the toner particles. We proposed a new developer that gives By including this metal complex type monoazo dye in the toner, even if carrier particles coated with silicone resin are used, the toner particles are sufficiently negatively charged to faithfully develop the electrostatic latent image at the initial stage of copying. However, positively charged toner particles gradually accumulate over the course of copying time, and after long-term use, toner particles also adhere to the background of the developed image obtained. was confirmed.

In the present invention, toner particles are sufficiently charged even when using carrier particles having a silicone resin surface that has a strong effect of preventing toner from becoming spent, and there is almost no accumulation of oppositely charged toner even when used for a long time. This provides a developer that does not generate.

That is, the present invention provides carrier particles whose surfaces are coated with silicone resin and the general formula: (However, X, Y, and Z represent hydrogen, halogen, carboxyl group, hydroxyl group, nitro group, sulfone group, and sulfamide group, and A represents H,
Represents K, Na or aliphatic ammonium cation. ) An object of the present invention is to provide an electrostatic latent image developer prepared by mixing toner particles containing a metal complex dye represented by

The silicone resin used in the present invention includes:
Any conventionally known silicone resin may be used, such as a room-temperature curing silicone resin represented by the general formula below, but it is easily understood from the essence of the present invention that other silicone resins may also be used. It is possible.

R: hydrogen atom, halogen atom, hydroxy group, methoxy group, _C1-4 lower alkyl group, or phenyl group _Commercially available silicone resins include, for example, KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, and SR2400 and SH840 manufactured by Toray Silicone. , SR2406 etc.

In the present invention, the carrier core material coated with silicone resin includes sand, cobalt, iron, copper, nickel, zinc, aluminum, brass, glass, and other nonmetallic materials with an average particle size of 20 to 1000μ, preferably 50 to 500μ. Conventionally used materials such as metals, metal alloys, etc. are widely used. The silicone resin may be coated by dissolving the resin in a solvent and applying it to the surface of the core material by a conventionally known means such as a spraying method.

The metal complex dye used in the present invention is preferably used in an amount of 0.1% by weight or more based on the toner resin component, and if it is less than 0.1% by weight, the toner particles are unlikely to be negatively charged. In particular, it is preferably mixed into the toner in a proportion of 0.5 to 10% by weight.

As the resin component constituting the toner particles, any conventionally known resin component can be used in the present invention, and examples include styrene resin, acrylic resin, polyvinyl chloride, polyvinyl acetate, epoxy resin, and alkyd resin. Examples include resin, polyethylene, phenolic resin, Bukiral resin, and polyester resin.

The toner particles of the present invention can be obtained by a known method, for example, by thoroughly mixing the above-mentioned resin components, a metal complex dye, and a coloring agent such as carbon black, which is usually necessary for forming a visible image although not necessarily required. It can be obtained by kneading in a hot roll mill, cooling and solidifying, then crushing and classifying. These toner particles have a surface area that is smaller than the surface area of the silicone resin surface of the carrier particles.
It is preferable to mix both particles to such an extent that they adhere to and account for 30 to 90% of the total amount.

Hereinafter, the present invention will be explained by giving examples.

Example 1 A toner having an average particle size of 6 μm was prepared using a metal complex dye having the following structural formula (1) according to the following recipe.

Prescription Styrene resin 85 parts by weight Metal complex dye (structural formula (1)) 1 part by weight Carbon black 14 parts by weight Structural formula (1) On the other hand, silicone resin (Shin-Etsu Chemical KR250) 1
A silicone resin-coated carrier was obtained by coating the surface of 5 kg of 100μ iron oxide powder using a fluidized bed silicone device.

Mix the above carrier and toner to make a developer.
When I made 100,000 copies using Ricoh's FT-6400 copier (+electrostatic latent image formation, magnetic brush development method) while replenishing toner appropriately, the images were clear and the toner charge amount was 15μc/ g and no deterioration occurred at all.

Further, the amount of oppositely charged toner generated in the developer after the above test was measured as follows. i.e. 2mm
A DC voltage of 300V is applied to the parallel electrode plates arranged at intervals, the developer to be measured is flowed between the two electrodes, and the toner attached to the opposite electrode plate is attached to the transparent adhesive tape.
When this was pasted on a white paper and the reflection density was measured using a Macbeth densitometer, the reflection density was
It was found to be extremely low at 0.20, indicating that there is almost no oppositely charged toner.

Example 2 A toner having an average particle size of 8 μm was prepared using a metal complex dye having the following structural formula (2) according to the following recipe.

Toner formulation Styrene-acrylic resin (manufactured by Sanyo Chemical Co., Ltd.)
SBM600) 90 parts by weight Metal complex dye (Structural formula (2)) 1 part by weight Carbon black 9 parts by weight Structural formula (2) On the other hand, silicone resin (manufactured by Toray Silicone)
SR2406) 1 kg was coated onto the surface of 5 kg of 70μ iron oxide powder using a fluidized bed coating device to obtain a silicone resin-coated carrier.

A copying test was conducted in the same manner as in Example 1.
Even after copying 100,000 copies, no image deterioration occurred. Also, Example 1 regarding the amount of oppositely charged toner generated
When measured in the same manner as above, the reflection density was 0.21, and almost no oppositely charged toner was observed.

Example 3 Using a metal complex dye having the following structural formula (3), a toner having an average particle size of 7 μm was prepared according to the following recipe.

Prescription styrene resin (Hercules D-125)
85 parts by weight Metal complex dye (structural formula (3)) 2 parts by weight Carbon black 13 parts by weight Structural formula (3) A developer was prepared by mixing the above toner with the silicone resin coated carrier obtained in Example 1.
The initial charge amount was 18 μc/g. When the developer was subjected to a copying test in the same manner as in Example 1, the charge amount after copying 100,000 sheets was 16A6CCc/g, with almost no decrease, and no image deterioration was observed. The amount of oppositely charged toner generated was also measured in the same manner as in Example 1, and the reflection density was 0.20, with almost no oppositely charged toner being observed.

Example 4 A developer was produced in exactly the same manner as in Example 1, except that the metal complex dye represented by structural formula (4) was used.

Structural formula (4) When the above developer was subjected to a copying test in the same manner as in Example 1, the amount of charge after copying 100,000 sheets was almost unchanged from that at the initial stage of copying, and no image deterioration was observed. The amount of oppositely charged toner generated was also measured in the same manner as in Example 1, and the reflection density was 0.21, with almost no oppositely charged toner being observed.

Example 5 A developer was produced in exactly the same manner as in Example 1, except that the metal complex dye having structural formula (5) was used.

Structural formula (5) When the above developer was subjected to a copying test in the same manner as in Example 1, the amount of charge after copying 100,000 sheets was almost unchanged from that at the initial stage of copying, and no image deterioration was observed. The amount of oppositely charged toner generated was also measured in the same manner as in Example 1, and the reflection density was 0.22, with almost no oppositely charged toner being observed.

Example 6 Silicone resin (SR2411 manufactured by Toray Silicone)
1Kg to 100μ ferrite powder (Fe, Zn, Ni
A developer was produced in exactly the same manner as in Example 1, except that a silicone resin-coated carrier was obtained by coating the surface of 5 kg of ferrite using a fluidized bed coating device. When the developer was subjected to a copying test in the same manner as in Example 1, no image deterioration or scumming occurred even after copying 100,000 copies.
Also, regarding the amount of oppositely charged toner generated, Example 1
When measured in the same manner as above, the reflection density was 0.20, and almost no oppositely charged toner was observed.

Comparative Example A developer using structural formula (6) as a toner dye was manufactured in exactly the same manner as in Example 1, and the same test as in Example 1 was conducted. The later charge amount was 15μC/g compared to the initial charge amount,
There was almost no change at 13 μc/g, but from about 50,000 sheets onwards, the amount of reversely charged toner generated increased to a reflection density of 1.1 using the measurement method of Example 1, and there was not much background smudge on copies.

Structural formula (6)

Claims (1)

[Scope of Claims] 1. An electrostatic latent image developer comprising a mixture of carrier particles whose surfaces are coated with a silicone resin and toner particles containing a metal complex dye represented by the following general formula. General formula: (However, X, Y, and Z represent hydrogen, halogen, carboxyl group, hydroxyl group, nitro group, sulfone group, and sulfamide group, and A represents H,
Represents K, Na or aliphatic ammonium cations. )