JP3284897B2 - Dry developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry developer used in electrophotography, electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art In a dry developer for electrophotography and electrostatic recording, its flowability is enhanced so that coagulation does not occur in a developer container, and the developer is smoothly supplied to a developing section. In addition, in order to make the triboelectric charging property of the toner less susceptible to external environmental fluctuations, and to stabilize the charge amount and charge sign of the toner, the inorganic additive of the fine particles is used as an external additive (hereinafter referred to as an external additive). It is widely practiced to add a small amount of a compound such as silica, alumina or titania.

[0003] However, the desired performance is not always easily exhibited due to the shape and physical properties such as hygroscopicity and triboelectricity of these external additives. Therefore, the particle size of the external additive is selected, and the surface thereof is treated with various hydrophobizing agents (JP-A-56-140356, JP-A-58-88759).
JP-A-5-34984, JP-B-56-128957, JP-B-1-58501, JP-A-3-30855, JP-A-6-16179), and a toner together with an external additive. An attempt to define the shape (Japanese Patent Laid-Open No. 4-204664) and a method in which an external additive is embedded in a toner in a predetermined ratio in advance and a free external additive coexists (Japanese Patent Laid-Open No. 7-43931) have been proposed. ing.

[0004] However, none of these has yet been obtained with satisfactory performance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer which is further improved in fluidity and toner chargeability, taking into account the problems of the above-mentioned technologies. Therefore, the present inventors have studied to achieve the above object. As a result, it was found that simply adding the external additive to the toner did not sufficiently exert the effect of the external additive for the following reasons. That is,
The particle size of the external additive that is generally used is very small compared to that of the toner, so that when the external additive is added in order to improve the fluidity, a multi-layer is formed around the toner particles. When an external additive is present, favorable fluidity of the toner is obtained, but the fine particles of the external additive present together with the toner in the container may be buried in the toner particles due to agitation or aging, or may be firmly adhered to the toner surface to some extent. When the toner particles adhere to the toner particles, the amount of external additive particles acting to reduce friction between toner particles is reduced between the toner particles, and the fluidity is deteriorated as compared with the initial stage. Furthermore, in such a situation of the external additive, the chance of the toner particles and the external additive particles coming into contact with each other is reduced, so that the initially expected triboelectric controllability given to the toner is also lost with the consumption of the developer. In addition to the tendency, the initial good triboelectric charging property changes.

Accordingly, the present inventors dispose a small amount of small-sized toner particles between the main toner particles and the external additive particles with respect to the main toner particles in terms of both volume and quantity as a developer. The method was examined, and the present invention was found to be superior to the conventional method of adding an external additive in terms of the durability of fluidity and the stability in triboelectric charging of the toner.

[0007]

Means for Solving the Problems A first invention is a coloring agent,
Based on 100 parts by weight of a toner mainly composed of a thermoplastic resin and having an average particle diameter of 8 to 12 μm obtained through a pulverizing and classifying step,
A mixture of toner particles having the same composition and small particles having an average particle diameter of 3 to 5 μm and inorganic particles having a particle diameter of 1 μm or less is used.
It is a dry developer characterized by being mixed in an amount of up to 50 parts by weight. A second invention is the developer according to the first invention, wherein the inorganic fine particles are 30 to 60 parts by weight based on 100 parts by weight of the small-sized toner particles.

A third invention is that the inorganic fine particles are alumina or alumina whose surface is modified with silicon oil or an aminofluorosilane derivative as required to adjust the charge code and charge amount of the toner. The dry developer according to the first invention or the second invention, characterized in that: A fourth invention is the developer according to any one of the first to third inventions, wherein the colorant is at least one selected from organic / inorganic pigments and magnetic substances.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The particle size of a toner mainly used for forming an image of the present invention has a distribution of 8 to 12 μm, and an external additive such as alumina which is inorganic fine particles to be added thereto is It is a fine particle size having a maximum distribution in the 0.01 to 0.1 μm region. Therefore, in order to prevent the above-mentioned undesired phenomena from occurring, three to three steps are required in the toner manufacturing process.
A small particle size toner having a distribution having a peak at 5 μm is interposed in a necessary minimum amount.

First, a fine powder external additive is mixed with the small particle toner to make the external additive fine particles conform to the surface of the small particle toner. A main toner comprising a mixture of a small particle size toner and a fine powder external additive, in which the fine powder external additive thus formed is partially adhered to the surface thereof, and is free and present near the surface. When a small amount is added to the toner, the small particle size toner and the fine powder external additive make the movement of the main toner smooth. As for the details of the mechanism that forms the basis of the present invention, a quantitative analysis has not been made, so it is necessary to wait for further studies, but figuratively, a very large gear (with many teeth) is very Assuming that a small gear (having a small number of teeth) is engaged, when a large gear is driven, the rotation torque increases and rotation becomes difficult.

However, at this time, it is considered that when a gear having an intermediate size is interposed between the two, it is very similar to a situation where a large torque is not required for the rotation and the rotation can be performed smoothly.

The method for obtaining the dry developer of the present invention includes:
For 100 parts by weight of the small particle size toner having an average particle size of 3 to 5 μm, the range is 0.01 to 0.01 μm, or 50 to 20 μm.
Add 30 to 60 parts by weight of alumina particles having a surface area of 0 m ² / g and mix well with a mixer to obtain 8 to 12 μm.
m based on 100 parts by weight of the main toner having an average particle size of
20 to 50 parts by weight. As a result, it is possible to obtain a developer having good fluidity that is resistant to environmental changes.

The dry developer of the present invention is stable even in the charged state of the toner, and can maintain an appropriate charge amount for development even when the developer is consumed as the copying machine is operated.

The inorganic fine particles used in the present invention are not particularly limited as long as the particle diameter is 1 μm or less. Representative examples include alumina and silica.

It is said that when the external additive is silica, the silica tends to be negative, and when the alumina is alumina, the toner tends to be positive. When the toner is directly mixed with the toner, since the external additive adheres to the toner surface, the charging sign of the toner is not necessarily reversed. However, in the method of the present invention, since the external additive is likely to be present together with the small particle size toner, the charging of the main toner is considered to be stable.

The effect of the external additive on the charge of the toner is generally determined mainly by the charge environment and the amount of charge of the toner. It is determined by the thermoplastic resin, and the external additive is considered to play an auxiliary role. In the method in which the external additive fine powder is directly added to and mixed with the main toner as in the above-described conventional means, the external additive particles adhere to and adhere to the main toner surface over time such as stirring. Since this greatly affects the triboelectric charging property of the main toner, the charging sign is adversely affected when the amount of charge of the toner is large.

In the present invention, an appropriate charge control agent is added to the main toner in an appropriate amount in the resin. However, in the present invention, since the effect of the small particle size toner on the external additive fine particles exerted on the main toner was reduced, the charging of the main toner did not change with time in both positive and negative toners.

A comparison of the suitability of alumina and silica as external additives showed that alumina was advantageous. This is because alumina has greater hydrophobicity and generally has a larger particle size than silica. It is considered that a better result was obtained than silica fine powder due to the tendency of positive charging. In the case of alumina, in order to obtain the optimal charging state and fluidity state of the surface, and to reduce the positive charging tendency of alumina, coating with a small amount of silicone oil or aminofluorosilane also improves the effect. It is effective from the case.

Furthermore, in the above description, a one-component developer has been described in mind. However, depending on the triboelectric charging property of the main toner and the developing method, and further depending on the characteristics of the toner, a one-component developer may be used in the two-component developing method. It goes without saying that the toner is required to have good fluidity and triboelectric stability as in the case of the developing method.

That is, as a toner for expressing a pictorial color, there is a problem in that an opaque substance (magnetite magnetic substance, etc.) or a coloring matter which adversely affects the hue, lightness, and saturation of a colorant is mixed in the toner. .

[0021]

The present invention will be described below in more detail with reference to examples.

Example 1 Crushed thermoplastic resin of styrene / acrylic copolymer 10
0 parts by weight of magnetite 45 for magnetic toner
Parts by weight and 3 parts by weight of nigrosine as a charge control agent for making a positively charged toner, and add 3 parts by a Henschel mixer.
After mixing for 0 minutes, the mixture was kneaded with an extruder having a temperature of 200 ° C. After cooling, it was crushed into small pieces to form pellets, and then crushed by a jet mill. The pulverized product was subjected to a classifier to obtain a toner powder group having a necessary distribution, and classified for each specific distribution particle. From this classification, a small particle size toner having an average particle size of 4 μm was selected, and 0.01 to 0.1 μm with respect to 100 parts by weight of the toner.
50 parts by weight of alumina fine powder (manufactured by Nippon Aerosil Co., Ltd.) having a particle size distribution of m were added and mixed, and mixed at room temperature for 5 hours in a ball mill containing ceramic balls. Next, of the classified toner, 40 parts by weight of the mixture of the small diameter toner and the alumina fine powder just prepared was added to 100 parts by weight of the toner having an average particle diameter of 10 μm, and the mixture was stirred well and mixed with the intended developer. Done In the flow test of this developer, the initial value was the same as that of the developer produced by the conventional method, and the value of the developer remaining after copying was the same as the initial value. In contrast, the conventional method showed deterioration. In the charge amount test of the toner as a real machine image by the suction method, the value at the initial stage and after the experiment is about 2
At 0 μc / g, there was no significant change and the value was satisfactory. In the actual image output test, this developer is used as a standard for the developer test. A prescribed amount is charged into the developer container of the copier development unit of R company using a positive development type and one-component development type using an organic photoreceptor. In low-humidity, low-temperature, normal-temperature, normal-humidity, high-temperature, high-humidity environments,
A continuous test of 00 copies was performed using three originals of solid, 7% characters and continuous tone. As a result, measured data and image quality satisfying the specified values in image density, fog, gradation, etc. were obtained, and a clear superior difference as compared with the result of the conventional developer performed in parallel Was seen and was fully satisfied.

When the surface condition of the developer according to the present invention at the time of 5000 copies was observed by SEM, alumina particles buried or adhered were hardly seen on the surface of the main toner particles having an average particle diameter of 10 μm which mainly form an image. Alumina particles were present on the surface of the small-sized toner particles, where the degree of burial was larger than in the initial state, and the surrounding free alumina particles were observed to be slightly reduced, and almost all copying started. It was determined that the time state was maintained (FIGS. 1 and 2). In contrast, with the toner of the conventional production method, considerable alumina particles embedded or adhered to the surface of the main toner particles as compared with the initial stage were observed (FIGS. 3 and 4). I think it has been proved that it is in the state as originally planned.

This also agrees with an experimental result in which the charge code and the charge amount of the toner are not greatly affected by the alumina external additive.

Example 2 A black non-magnetic developer was prepared in the same manner as in Example 1. However, this time, the charge control agent was changed from nigrosine to isol black for negative charging (manufactured by Hodogaya Chemical Co., Ltd.), and 3 parts by weight and 5 parts by weight of carbon black pigment were mixed instead of magnetite as the pigment. The same alumina was used for the externally added fine powder. A developer prepared in the same manner as in Example 1 with such a composition was mixed with 3 parts by weight of the spherical ferrite carrier particles in an amount of 100 parts by weight using a V-type mixer to obtain a developer. Also in this developer, the flow test showed the same value in the initial stage and after the experiment. In addition, in the triboelectric charging test of the toner by the suction method, the value at the initial stage and after the experiment was about 18 μc / g, and a value almost within the specified range was obtained.

Next, as an actual machine test, the same test as in Example 1 was performed by a two-component developing type laser printer of Company M by reversal type development using an organic photoreceptor which is also a standard testing machine, and was compared as a comparative object. Significantly better results were obtained compared to the conventional two-component developer used. This test confirmed that satisfactory performance as a negatively charged toner was obtained even when alumina was used as an external additive.

Example 3 A cyan developer was prepared in the same manner as in Example 1. As a pigment, 10 parts by weight of a phthalocyanine blue organic pigment (manufactured by Toyo Ink Co., Ltd.) is used for 100 parts by weight of a resin, and 0.3 parts by weight of a cationic surfactant having no spectral absorption in a visible region is used as a charge control agent. Was used to form a positively charged developer. As in Example 1, the toner having an average particle size of 4 μm
Then, 45 parts by weight of 100 m ² / g alumina particles (manufactured by Nippon Aerosil Co., Ltd.) were added, and the powder for external addition was similarly prepared.
Furthermore, 25 parts by weight of the main toner were added and mixed to obtain a one-component developer. In the test, in the performance test performed in comparison with the conventional cyan toner manufactured by our company, the measured values after the actual machine test showed no deterioration in the fluidity and the triboelectric chargeability. The actual machine comparison test was performed using the same standard test machine as in Example 1. Also in this test, image quality having a remarkably superior difference from the conventional toner was confirmed.

[0028]

As is apparent from the above description, the main toner which forms the main component of the image formation after the alumina fine powder adheres to the surface of the small particle size toner and is present in the vicinity of the small particle size toner even in a free state. When used in an electrostatic copying machine or an electrostatic printer, it is possible to minimize the change in the fluidity of the developer and the change in the charging performance of the toner when used in an electrostatic copying machine or an electrostatic printer. I found something. Further, the influence of the alumina external additive on the charge code and the charge amount of the toner could be made auxiliary. Further, it was confirmed that the composition was effective for color toners and both one-component and two-component developers.

Therefore, by using the developer according to the present invention, it is possible to stabilize the performance of an electrostatic copying machine or an electrostatic printer, thereby contributing to improvement in reliability of device performance and reduction in cost in device design. At the same time, the economical efficiency of the developing material is improved, which greatly contributes to the reduction of the running cost on the user side.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a toner at the start of copying in Example 1 of the present invention.

FIG. 2 is an electron micrograph of the toner when 5000 sheets were copied in Example 1 of the present invention.

FIG. 3 is an electron micrograph of a toner at the start of copying according to a conventional method.

FIG. 4 is an electron micrograph of the toner when 5000 sheets were copied according to a conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (4)

(57) [Claims] 1. An average particle diameter of the same composition of 3 to 5 parts per 100 parts by weight of a toner mainly containing a colorant and a thermoplastic resin and having an average particle diameter of 8 to 12 μm obtained through a pulverization and classification step.
the small particle size toner particles [mu] m, 1 [mu] m or less of the inorganic fine particles
A dry developer comprising 20 to 50 parts by weight of a mixture of the above. 2. The method according to claim 1, wherein 100 parts by weight of the small-sized toner particles
It is characterized in that the machine particles are 30 to 60 parts by weight.
The developer according to claim 1. 3. The method according to claim 1, wherein the inorganic fine particles are alumina or alumina whose surface is modified with silicon oil or an aminofluorinated silane derivative as required to adjust the charge code and charge amount of the toner. Claim
Item 3. The dry developer according to Item 1 or 2 . 4. A colorant comprising at least one selected from organic and inorganic pigments and magnetic substances.
The developer according to claim 1 .