JPH04322257A - Electrostatic charge image developing method - Google Patents

Abstract

PURPOSE:To enhance chargeability characteristics in an early stage and at the time of friction and image density and fineness in texture, and the like and to solve problems, such as toner scattering. CONSTITUTION:The toner containing as a post-treating agent hydrophobic silica and hydrophobic titania or alumina is used as a toner for a starter toner or a replenishing toner, and the content of the hydrophobic titania or the hydrophobic alumina in the starter toner is set to a content more than the content of those in the replenishing toner.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to electrophotography, electrostatic recording,
The present invention relates to a method of developing an electrostatic charge image in electrostatic printing or the like.

0002

2. Description of the Related Art Generally, in electrophotography, a certain amount of toner is charged into a developing device, and copies are made repeatedly.
A system is adopted in which when the toner decreases by a certain amount, the decreased amount of toner is replenished. Conventionally, toner is used to replenish the decreased amount (hereinafter referred to as "replenishment toner").
Usually, the same toner (hereinafter referred to as "starter toner") that is initially loaded into the developing device is replenished.

[0003] Toner used in electrophotography has a fluidizing agent such as silica, titania or alumina added thereto in order to improve fluidity, cleaning properties, etc. of the toner. Since silica is the most easily available, it is mainly added as a general-purpose fluidizing agent, but silica alone has problems such as high initial charge level, environmental instability, and reduced fluidity due to embedding. In order to prevent these problems, toners have been proposed in which, in addition to silica, a fluidizing agent such as titania or alumina is added in combination.

[0004] By adding a fluidizing agent in combination in this way, the high initial charge amount of silica can be suppressed and the toner can be quickly charged to the required appropriate charge level. Because it is possible to
Toner can be made to have excellent initial image characteristics, but titania or alumina inherently have a lower charge level than silica, so if used for a long period of time, they will be affected by these and the amount of charge will be insufficient. This causes problems such as toner scattering and associated problems such as image fogging. Furthermore, due to toner consumption, even if toner is supplied, the essential problem of insufficient toner charge amount during continuous printing cannot be solved.

[0005]

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and has excellent initial charging characteristics and charging characteristics during durability printing, and is capable of forming images with excellent image density and image quality without fogging. An object of the present invention is to provide a method for developing an electrostatic image.

[0006]

[Means for Solving the Problems] That is, the present invention uses hydrophobic silica as a post-treatment agent and a toner containing hydrophobic alumina or hydrophobic alumina as a starter toner and a replenishment toner. The present invention relates to an electrostatic image developing method characterized in that the content of hydrophobic titania or hydrophobic titania is greater than the content of hydrophobic titania or hydrophobic alumina in a replenishment toner.

In the starter toner used in the present invention, the amount of hydrophobic silica is 0.1 to 1.0% by weight, preferably 0.2 to 0.5% by weight, based on the toner before addition of the post-processing agent. Add a proportion of Hydrophobic titania or hydrophobic alumina is added in an amount of 0.2 to 3.0% by weight, preferably 0.2 to 2.0% by weight, based on the toner before addition of the post-treatment agent. In addition to silica, by adding a certain amount of titania or alumina, while maintaining characteristics such as toner fluidity and image quality, the excessively high initial charging characteristics of silica are suppressed, and charging is quickly achieved to an appropriate charging level. This makes it possible to form an image with sufficient image density and excellent image quality. If the amounts of silica and titania added are outside the above ranges, the fluidity of the toner will deteriorate, and further problems will occur in the texture, fog, etc. of the formed images.

[0008] As the replenishment toner used in the present invention,
Hydrophobic silica is added in the same amount as added to the starter toner, and hydrophobic titania or hydrophobic alumina is added in a smaller amount than that added to the starter toner. The specific amount of addition is when the amount of hydrophobic titania or hydrophobic alumina added to the starter toner is TA weight %, and the amount of hydrophobic titania or hydrophobic alumina added to the replenishment toner is TB weight %. , TA-TB difference is 0.1 to 1.0% by weight, preferably 0.1 to 0.9% by weight. By doing so, it is possible to eliminate the insufficient amount of charge during printing, and to stably form an image with excellent image density, texture, etc., without causing toner scattering, fogging, etc. TA-T
If the difference in B is outside the above range, toner scattering and image fogging will become a problem.

The toner to which the post-processing agent of the present invention is added is generally fine particles consisting of at least a binder resin such as acrylic resin, polystyrene resin, polyester resin, styrene-acrylic copolymer resin or epoxy resin, and a colorant, and a magnetic carrier. There are toners that are used as two components together with particles, toners that are used as a non-magnetic single component, and toners that are used as a single component that contains a magnetic agent inside the toner (magnetic toner). It can also be applied to the toner used in the method. This will be explained below using examples.

Production example of green toner (Binder resin: Production of vinyl-modified polyester resin) Polyoxyethylene (2)-2,2-bis(4
68 parts by weight of -hydroxyphenyl)propane, 16 parts by weight of isophthalic acid, 16 parts by weight of terephthalic acid, 0.3 parts by weight of maleic anhydride, and 0.06 parts by weight of dibutyltin oxide were placed in a flask and heated at 230°C under a nitrogen atmosphere. The reaction was continued for 24 hours and then taken out. The weight average molecular weight of the obtained unsaturated polyester resin was 10,600.

50 parts by weight of this unsaturated polyester resin,
50 parts by weight of xylene was charged into a flask and dissolved. The temperature was raised until the xylene refluxed, and a solution of 13 parts by weight of styrene, 0.4 parts by weight of azobisisobutyronitrile dissolved in 2 parts by weight of methyl methacrylate was added dropwise under nitrogen atmosphere over about 30 minutes while the xylene was refluxing. . Keep warm for 3 hours after dropping.
After distilling xylene under reduced pressure, the resin was taken out, and the weight average molecular weight was 13,100, and the melt viscosity at 100°C was 6x.
A binder resin having 104 poise and a glass transition temperature of 63°C was obtained. However, the melt viscosity is a value measured using a Shimadzu flow tester CFT-500 under the conditions of a nozzle diameter of 1 mm, a nozzle length of 1 mm, a load of 30 kg, and a temperature increase rate of 3° C./min.

0012

Part by weight: Styrene acrylic modified polyester resin obtained above
100・Organic pigment Lionol Blue FG
-7350 (manufactured by Toyo Ink Mfg. Co., Ltd.) 3. Charge control agent (Bontron E-84, manufactured by Orient Chemical Co., Ltd.)
3 The above materials were thoroughly mixed using a Henschel mixer, kneaded using a twin-screw extruder, and then cooled. The mixture was coarsely pulverized using a feather mill, and then using a jet pulverizer and an air classifier, particles having a particle size of 5 to 25 μm (average particle size 10.5 μm) were obtained. The particles obtained as described above are referred to as raw toner (A).

Example of manufacturing carrier Styrene consisting of styrene, methyl methacrylate, 2-hydroxyethyl acrylate, and methacrylic acid
Acrylic copolymer (1.5:7:1.0:0.5)8
0 parts by weight and 20 parts by weight of the butylated melamine resin were diluted with toluene to prepare a styrene acrylic resin solution with a solids ratio of 2%.

[0014] Calcined ferrite powder (F-300
; Average particle size: 50 μm, bulk density: 2.53 g/cm3
; The styrene acrylic resin solution was applied using a spiller coater (manufactured by Okada Seiko Co., Ltd.) and dried. The obtained carrier was baked at 140° C. for 2 hours in a hot air circulation oven. After cooling, the ferrite powder bulk was crushed using a sieve shaker equipped with screen meshes with openings of 210 μm and 90 μm to obtain resin-coated ferrite powder. The above-mentioned application, firing, and crushing were repeated three more times for this ferrite powder (first firing).

The ferrite powder obtained in the first firing was fired in the oven at 170° C. for 3 hours (secondary firing). After cooling, the ferrite bulk was crushed in the same manner as above to obtain a resin-coated carrier. The average particle size of the obtained carrier was 5
2 μm, the coating resin amount (Rc) was 2.95%, the thermal decomposition peak temperature was 295° C., and the electrical resistance was about 4×10 10 Ωcm.

The amount of coated resin (Rc) was determined as follows. Approximately 5 g of the resin-coated carrier is placed in a 10 cc magnetic crucible in which the weight W0 (g) has been accurately weighed in advance, and the entire magnetism W1 (g) is accurately weighed. This crucible was placed in a muffle furnace, and the temperature was raised to 900°C at a rate of 15 degrees per minute, and the crucible was left at 900°C for 3 hours to burn the coating resin, and then allowed to cool to room temperature. After reaching room temperature,
Immediately, accurately weigh the weight W2 (g) of the crucible containing the carrier. The amount of coated resin (Rc) is determined by the following formula.

[0017]

[Math 1]

The carrier particle size was measured using a laser diffraction particle size distribution analyzer manufactured by Microtrac.

The bulk density was measured in accordance with JIS Z 2504 using a bulk specific gravity meter manufactured by Kuramochi Scientific Instruments Manufacturing Co., Ltd.

The thermal decomposition peak temperature was determined from a DSC curve using a thermal analyzer (Seiko Electronics Co., Ltd., SSS-5000).

Example 1 Based on raw toner (A), ■ Starter toner Hydrophobic titania (manufactured by Nippon Aerosil Co., Ltd.: T-805) 1.65 wt%
Hydrophobic silica (manufactured by Wacker: H2000/4
) 0.3wt% ■
Replenishment toner Hydrophobic titania (manufactured by Nippon Aerosil Co., Ltd.: T-805) 0.8wt%
Hydrophobic silica (manufactured by Wacker: H2000/
4) 0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

Example 2 For raw toner (A): ■ Starter toner Hydrophobic titania (same as Example 1) 0.95w
t% hydrophobic silica (same as Example 1)
0.3wt% ■ Replenishment toner Hydrophobic titania (same as Example 1) 0.8
wt% hydrophobic silica (same as Example 1)
0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

Example 3 For raw toner (A): ■ Starter toner Hydrophobic titania (same as Example 1) 1.1
wt% hydrophobic silica (same as Example 1)
0.3wt% ■ Replenishment toner Hydrophobic titania (same as Example 1) 0.8
wt% hydrophobic silica (same as Example 1)
0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

Example 4 Based on raw toner (A), ■ Starter toner Hydrophobic alumina (manufactured by Nippon Aerosil Co., Ltd.: RX-C) 1.1 wt%
Hydrophobic silica (same as Example 1)
0.3wt%
■Replenishment toner Hydrophobic alumina (manufactured by Nippon Aerosil Co., Ltd.: RX-C) 0.8wt%
Hydrophobic silica (same as Example 1)
0.3wt% ■
, (2) were mixed using a Henschel mixer to obtain a toner.

Comparative Example 1 Compared to raw toner (A), both ■starter toner and ■replenishment toner were hydrophobic titania (Example 1).
)
0.8wt% hydrophobic silica (same as Example 1)
0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

Comparative Example 2 Compared to raw toner (A), ■ Starter toner Hydrophobic titania (same as Example 1) 2.0
wt% hydrophobic silica (same as Example 1)
0.3wt% ■ Replenishment toner Hydrophobic titania (same as Example 1) 0.8
wt% hydrophobic silica (same as Example 1)
0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

Comparative Example 3 Compared to raw toner (A), ■Starter toner Hydrophobic titania (same as Example 1) 0.8
wt% hydrophobic silica (same as Example 1)
0.1wt% ■ Replenishment toner Hydrophobic titania (same as Example 1) 0.8
wt% hydrophobic silica (same as Example 1)
0.3 wt% (1) and (2) were mixed in a Henschel mixer to obtain a toner.

The toners obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were mixed with the carrier at a content of 8.0% by weight to prepare a developer. Copied images were formed using a copying machine CF-70 (manufactured by Minolta Camera Co., Ltd.) so that the toner consumption amount was about 200 mg per copy, and the initial images and images after printing 5000 copies were evaluated. The evaluation items are as follows.

・Charge amount Blow-off method was used (toner concentration: 8% by weight). - Image density The amount of toner adhesion per unit area of the solid image area was measured and ranked as follows. ○: The adhesion amount was 0.9 mg/cm2 or more as ○. ×: The adhesion amount was less than 0.9 mg/cm 2 as ×. - Texture on the image The texture on the half image was evaluated and ranked. A rank of △ or higher is practically usable, but a rank of ○ or higher is desirable. - Fog on images Toner fog on white background images was visually measured and ranked. Although it is practically usable at △ rank and above,
○ or above is desirable. The results are summarized in Table 1 below.

[0030]

[Table 1]

[0031]

Effects of the Invention: During printing, the charging properties are as good as the initial charging properties, and it is possible to form excellent images with high image density and no fog.

Claims (1)

[Claims] Claim 1: A toner containing hydrophobic silica and hydrophobic titania or hydrophobic alumina as a post-treatment agent is used as a starter toner and a replenishment toner, and the content of hydrophobic titania or hydrophobic alumina in the starter toner is reduced. , an electrostatic image developing method characterized in that the content of hydrophobic titania or hydrophobic alumina is greater than that of a replenishing toner.