JPH04309961A - Full color toner for electrostatic charge image development - Google Patents

Abstract

PURPOSE:To stably obtain a scrupulous image low in difference of chargeability in environment by allowing to contain silica which exists in semi-buried state, titania or alumina obtained by liquid phase process sticking in non-buried state on a surface. CONSTITUTION:A part of silica particle sticks to be buried into the surface, titania obtained by liquid phase process or alumina obtained by liquid phase process sticks to be in contact with a surface of a toner without buried into the surface. This is, hydrophobic treated silica exists in semi-buried state on a surface of the full color toner and titania or alumina obtained by liquid phase process and hydrophobic treated is stuck on the toner surface in non-buried state. Increasing of quantity of electrification in a low humidity is prevented while keeping chargeability of the toner since influence of the silica surface is suppressed with security of charge point carrying charge by allowing to exist silica particle on the toner surface in semi-buried state. In this case, 0.1-1.0wt.% preferably 0.1-0.5wt.% silica to the toner is added.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color toner for developing an electrostatic image for forming a full-color copy image.

0002

2. Description of the Related Art Electrophotographic systems are widely used in PPCs, printers, facsimile machines, etc., and a full-color image forming system that reproduces multiple colors by overlapping toners of multiple colors has come to be adopted. in general,
Toners used not only for full-color development methods but also for electrostatic latent image development include inorganic fine powders and toner surface treatments in order to impart fluidity to the toner and improve cleaning properties. Ru. As such inorganic fine particles, silica, titanium, or a mixture of both (for example, JP-A-60-136755 or JP-B No. 2-5) are used because they are easily available and have excellent fluidity.
5774) etc. are used.

[0003] However, full-color toner generally uses a resin with a lower softening point than the binder resin used in conventional black toner. It is necessary to add inorganic fine particles and perform surface treatment. In such cases, if silica is used alone as the inorganic fine particles, the silica itself is highly resistive and has a large specific surface area, so there is a problem that the amount of charge on the toner becomes too high and the image density becomes low. . This problem is particularly noticeable in low humidity environments. In addition, when titanium is used alone as inorganic fine particles, since titanium has a relatively large particle size and low resistance, the toner is likely to be insufficiently charged, causing fogging on the background and toner powder smoke. Problems tend to occur in high humidity environments.

0004

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a full-color toner having excellent fluidity, chargeability, and environmental stability. A further object of the present invention is to provide a full-color toner capable of forming high-quality images with excellent texture, image density, etc. without generating toner powder smoke or fog.

[0005]

That is, the present invention relates to a full color toner having silica existing in a semi-buried state on the surface and liquid phase titania or liquid phase process alumina attached to the surface in a non-buried state.

The type of full-color toner used in the present invention is not particularly limited, and any conventionally used full-color toner may be used. The present invention has a structure in which hydrophobized silica is present in a semi-buried state on the surface of such a full color toner, and titanium or alumina, which is obtained by a liquid phase method and has been hydrophobized, is attached to the toner. There is a characteristic in doing. By doing so, environmental fluctuations in toner charging performance are reduced, and images with fine texture in solid areas can be obtained.

The silica used in the present invention is one that is normally added to toner, that is, one that has a primary particle size of 5 to 20 μm and has been treated to be hydrophobic. For example, hydrophobic silica R-972 (primary particle size 16 mμm: manufactured by Nippon Aerosil Co., Ltd.), hydrophobic silica R-974 (primary particle size 12 m μm)
μm: Nippon Aerosil Co., Ltd.), hydrophobic silica R-976
(Primary particle size 7mmμm: manufactured by Nippon Aerosil Co., Ltd.), hydrophobic silica H2000, H2000/4 (primary particle size 10-15
mμm (manufactured by Wacker), etc. are available.

In the present invention, the silica particles are allowed to exist in a semi-buried state on the toner surface. In this specification, the term "semi-buried state" refers to a state in which a part of the particles is embedded and attached to the toner surface, as shown in FIG. 1, and a state in which the particles are not embedded in the toner surface. As shown in FIG. 2, a state in which the toner is merely in contact with and adheres to the surface of the toner is referred to as a non-embedded state. When silica particles are present on the toner surface in a non-buried state, the silica itself tends to increase the charge amount of the toner, especially in low-humidity environments, because the silica itself is minute and has high resistance, and the amount of silica used is large. By making the silica particles semi-buried as shown in Figure 1, the invention makes it possible to secure charging points responsible for charging while suppressing the influence of the silica surface, thereby maintaining the charging ability of the toner. , it is possible to suppress an increase in the amount of charge at low humidity. If the amount of silica added is reduced in order to reduce the influence of the silica surface, the charging point will decrease, resulting in a decrease in the charging ability of the toner and also deteriorating the texture of the resulting copied image. In the present invention, silica is added in an amount of 0.1 to 1.0% by weight, preferably 0.1 to 0.5% by weight, based on the toner. If the amount is less than 0.1% by weight, there is no effect of adding silica, and if it exceeds 1.0% by weight, the high charge level and poor environmental resistance of silica cannot be improved. Furthermore, in the present invention, hydrophobically treated liquid phase titania or liquid phase alumina is allowed to exist on the toner surface in a non-buried state.

[0009] Titania or alumina used in the present invention has a particle size of 10 to 60 μm, and is used in an amount of 0.2 to 3.0% by weight, preferably 0.2 to 2.0% by weight, based on the toner.
Add % by weight. If it is less than 0.2% by weight, the effect of addition cannot be obtained, and if it is more than 3.0% by weight, the problem arises that the charging level becomes too low. Also, titania or alumina has a larger particle size than silica, so
It has the function of acting as a spacer between toners, which cannot be obtained with small particle size silica, and particularly prevents toner aggregation during transfer, contributing to the formation of a textured image. Therefore, if titania or alumina is used in a semi-buried state like silica, its effect as a spacer will be weakened and the fineness of the image will be impaired.

[0010] As titania or alumina, one produced by a liquid phase method is used. Products manufactured using the liquid phase method are
Since the surface has few irregularities and is not porous, it is difficult for moisture to adhere to it, and it is difficult for charge to leak from the toner surface, ensuring uniformity in the amount of charge between toner particles, and even in high humidity environments. There is no decrease in the amount of toner, and no fogging or toner powder smoke occurs. Another method for producing titania or alumina is known as the vapor phase method.However, titania or alumina produced using the vapor phase method is porous and has many surface irregularities, so it is easily affected by moisture. The above effects cannot be obtained.

[0011] The fine particles of silica, titania or alumina added to the toner are subjected to a hydrophobic treatment for environmental stability. As the hydrophobizing agent, various coupling agents such as silane type, titanate type, aluminum type, zircoaluminate type, silicone oil, etc. are used. Examples of silanes include chlorosilane, alkylsilane, alkoxysilane, and silazane.

[0012] The surface of inorganic fine powder such as silica or titania can be treated with a hydrophobizing agent under commonly used conditions, for example, by the following method. First, a hydrophobizing agent alone or tetrahydrofuran (THF)
, mixed and diluted with a solvent such as toluene, ethyl acetate, methyl ethyl ketone, or acetone, and while forcibly stirring the inorganic fine powder with a blender, a predetermined amount of the hydrophobizing agent or its diluted solution is dropped or sprayed. Add and mix thoroughly. Next, the obtained mixture is transferred to a vat or the like and placed in an oven to heat and dry. Thereafter, the mixture is stirred again using a blender to thoroughly crush the mixture. In such a method, each hydrophobizing agent may be used simultaneously. In addition to such a dry method, there is also a wet treatment method in which fine inorganic powder is immersed in a solution containing a hydrophobizing agent and an organic solvent, and the mixture is stirred and crushed.

[0013] Furthermore, it is preferable that the inorganic fine powder is subjected to a heat treatment at 100°C or higher before being subjected to the above-mentioned hydrophobization treatment. By adjusting the mixing conditions, silica, titania, or alumina as described above can be attached to the surface of the toner in a semi-buried state or in a non-buried state. Full color toner generally uses low viscosity resin to ensure color reproducibility.
The degree of burial depends largely on the mixing conditions.

[0014] The buried state can be achieved by increasing the mixing conditions by increasing the stirring speed, lengthening the stirring time, etc. Under such strong stirring conditions that the inorganic fine particles are buried in the toner particle surface, the agglomeration of the silica fine particles is broken up, and the fine particles adhere to the toner surface in a highly dispersed state (FIG. 1).

On the other hand, as the mixing conditions become weaker, the degree of embedding becomes smaller, and it is possible to realize a non-embedded state in which the material is in contact with the surface. In this case, the agglomeration of fine particles such as titania is not completely destroyed, and the fine particles adhere to the surface of the toner particles in an aggregated state (FIG. 2). Examples of resins to which the manufacturing method of the present invention can be applied include resins that ensure light transmittance and fixing properties and have a certain degree of heat resistance as full-color toner constituent resins, such as polystyrene resins, styrene resins, etc.
Examples include acrylic resins, polyethylene resins, epoxy resins, and polyester resins. especially,
Polyester resins are preferably used, including polyols such as bisphenols, ethylene glycols, triethylene glycol, 1,2-propylene glycol, and 1,4-butanediol, and aliphatic resins such as maleic acid and itaconic acid. Examples include those obtained by polycondensing dihydrochloric acid groups such as unsaturated dihydrochloric acid, phthalic acid, terephthalic acid, isophthalic acid, malonic acid, and succinic acid. Alternatively, a modified polyester resin may be used in which an unsaturated polyester is present in a polyester resin and an aromatic vinyl monomer is graft-polymerized to the unsaturated polyester. The proportion of polyester in this modified polyester is 50% by weight or more, preferably 60 to 90% by weight.
It is.

In the present invention, the polyester resin constituting the toner has a number average molecular weight (Mn) of 250.
0-12000, dispersity (Mw/Mn) 2-6, glass transition point (Tg) 50-70°C, melting point (Tm) 8
A temperature of 0°C to 120°C is suitable. When these physical properties are not satisfied, the toner cannot have sufficient light transmittance, and its fixing properties and heat resistance are reduced.

[0017] The above-mentioned polyester resin usually has poor environmental stability, but according to the present invention, it can be used satisfactorily.

As a coloring agent, for example, as a yellow coloring agent, C.I. I. Pigment Yellow 12, C. I.
pigment yellow 13 etc. as a red (magenta) coloring agent. I. Pigment Red 122, C. I. Pigment Red 57:1, C.I. as a blue (cyan) colorant. I. Pigment Blue 15 and the like can be mentioned, but the colorant is not limited to these, and pigments, dyes, etc. of various colors conventionally used in translucent color toners can be used. The present invention will be explained below with reference to Examples.

(Titanium Production Example) 100 parts by weight of titanium dioxide (MT600B; manufactured by Teika Corporation) having a primary particle size of 50 mμm produced by a liquid phase method was mixed with the following structural formula [i]

A solution prepared by diluting 5 parts by weight of silicone oil with 50 parts by weight of xylene was spray coated. After drying, the obtained titanium dioxide was heat-treated at 150° C. for 1 hour to obtain hydrophobized titanium dioxide A.

(Production example of resin for full color toner) 68 parts by weight of polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane, 16 parts by weight of isophthalic acid, 16 parts by weight of terephthalic acid, maleic anhydride. A flask was charged with 0.3 parts by weight and 0.06 parts by weight of dibutyltin oxide, and the reaction was continued at 230° C. for 24 hours under a nitrogen atmosphere, and then taken out to obtain a polyester resin containing unsaturated polyester. The weight average molecular weight of the obtained polyester resin was 10,600. This polyester resin 5
0 parts by weight and 50 parts by weight of xylene were charged into a flask and dissolved. The temperature was raised until the xylene refluxed, and a solution of 13 parts by weight of styrene and 0.4 parts by weight of azobisisobutyronitrile dissolved in 2% by weight of methyl methacrylate was added dropwise under nitrogen atmosphere over about 30 minutes while the xylene was refluxing. . After the dropwise addition, the mixture was kept warm for 3 hours, xylene was distilled under reduced pressure, and the resin was taken out to obtain a binder resin having a weight average molecular weight of 13,100, a melt viscosity at 100°C of 6×10 4 poise, and a glass transition temperature of 63°C. However, the melt viscosity was measured using a flow tester CFT-500 manufactured by Shimadzu Corporation, with a nozzle diameter of 1 mm,
This value was measured under the conditions of a nozzle length of 1 mm, a load of 30 kg, and a temperature increase rate of 3° C./min.

(Color toner production example ■) (i) Yellow toner

Part by weight: Styrene acrylic modified polyester resin obtained above
100・Organic pigment Lionol Yellow
FG-1310
2.5 (manufactured by Toyo Ink Mfg. Co., Ltd.) - Charge control agent (Bontron E-84; manufactured by Orient Chemical Co., Ltd.) 3 The above materials were thoroughly mixed in a Henschel mixer, kneaded in a twin-screw extruder, and then cooled. The mixture was coarsely pulverized using a feather mill, and then a jet pulverizer and an air classifier were used to obtain particles having a particle size of 5 to 20 μm (average particle size 10.5 μm). The obtained particles and 0.3% by weight of hydrophobized silica H2000/4 (
(manufactured by Wacker) in a Henschel mixer at 1000 r.
pm for 3 minutes. Subsequently, 0.9% by weight of titanium dioxide A was added and treated at 1000 rpm for 0.5 minutes. In this way, yellow toner (■) was obtained. When the surface of the yellow toner ■ was observed using a scanning electron micrograph (SEM), silica was uniformly present in a semi-buried state on the toner surface without agglomerating, and titanium dioxide was not buried and was agglomerated. It was confirmed that it was attached in a state where it was attached. (ii) Magenta toner Lionol Red 6B F as pigment
A magenta toner (2) was prepared in the same manner as the yellow toner except that 2.5 parts by weight of G-4213 (manufactured by Toyo Ink Manufacturing Co., Ltd.) was used. (iii) Cyan toner Lionol Blue FG-7 as pigment
A cyan toner (2) was prepared in the same manner as the yellow toner except that 2.5 parts by weight of C.350 (manufactured by Toyo Ink Manufacturing Co., Ltd.) was used. (iv) Black toner As a pigment, Lionol Yellow FG-1310
(manufactured by Toyo Ink Manufacturing Co., Ltd.) 2 parts by weight
Lionol Red 6B FG-4213 (
Toyo Ink Manufacturing Co., Ltd.) 5 parts by weight Lion
ol Blue FG-7350 (manufactured by Toyo Ink Manufacturing Co., Ltd.) A black toner (2) was produced in the same manner as the yellow toner except that 5 parts by weight was used.

(Color toner production example (■)) In the above color toner production example (■), hydrophobized titanium dioxide A
Hydrophobic titanium T-805 (
Yellow toner (2), magenta toner (2), cyan toner (2), and black toner (2) were produced in the same manner except that 0.9% (manufactured by Nippon Aerosil Co., Ltd.) was used.

(Color toner production example ■) In the above color toner production example ■, the mixing conditions using the Henschel mixer were as follows: 1000 rpm, 1 minute for silica H2000/4, 1000 rpm, 0.5 for titanium dioxide A. A yellow toner (2), a magenta toner (2), a cyan toner (2), and a black toner (2) were produced in the same manner except that the toner was heated for 3 minutes. When each of the obtained toners was observed using a SEM, both silica and titanium dioxide were found to be attached to the toner surface in a non-embedded state.

(Color toner production example ■) In the above color toner production example ■, silica using a Henschel mixer,
Yellow toner (1), magenta toner (2), cyan toner (2), and black toner (2) were produced in the same manner except that silica H2000/4 and titanium dioxide A were simultaneously mixed at 1000 rpm for 4 minutes. When each of the obtained toners was observed using a SEM, both silica and titanium dioxide were found to be attached to the toner surface in a semi-buried state.

(Color toner production example ■) In the above color toner production example ■, the mixing order of silica and titanium was reversed, and the mixing conditions using the Henschel mixer were changed to 1000 rpm for titanium dioxide A and silica H200 for 3 minutes.
Yellow toner (2), magenta toner (2), cyan toner (2), and black toner (2) were produced in the same manner except that the speed was 1000 rpm and 0.5 minutes for 0/4. When each of the obtained toners was observed using a SEM, it was found that silica was not buried and titanium dioxide was present on the surface of the toner in a semi-buried state.

(Carrier Production Example) A styrene-acrylic copolymer (1.
5:7:1.0:0.5) and 20 parts by weight of the butylated melamine resin were diluted with toluene to prepare a styrene acrylic resin solution with a solid ratio of 2%. Using fired ferrite powder (F-300; average particle size: 50 μm, bulk density: 2.53 g/cm3; manufactured by Powder Tech Co., Ltd.) as the core material,
The above 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 is opened to 21 pores.
It was crushed using a sieve shaker equipped with screen meshes of 0 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 heated at 170°C in the above oven.
It was fired 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 52 μm, and the amount of coating resin (
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 resin-coated carrier, weighed accurately in advance to weigh W0 (g) 10
Place it in a cc magnetic crucible and accurately weigh the entire weight W1 (g). 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. Immediately after reaching room temperature, the weight W2 (g) of the crucible containing the carrier is accurately weighed. Coated resin amount (Rc)
is determined by the following formula.

[0027]

[Math 1]

The carrier particle size was measured using a laser diffraction particle size distribution analyzer manufactured by Microtrac. The bulk density was measured according to JIS Z 2504 using a bulk specific gravity meter manufactured by Kuramochi Scientific Instruments Manufacturing Co., Ltd. The thermal decomposition peak temperature was measured using a thermal analyzer (manufactured by Seiko Electronics Co., Ltd., SSS-
5000) from the DSC curve.

(Evaluation) (Example) Yellow obtained in color toner production example (■),
Magenta, cyan, and black toners and the carrier prepared in the carrier manufacturing example were mixed at a weight ratio of 8:92 to prepare a full color developer. This developer is applied to a full color copying machine (C
F-70 (manufactured by Minolta Camera Co., Ltd.) was used to evaluate the following items. ●Charge amount: Based on blow-off method (toner concentration: 8% by weight). ●Fog on images (BGD) As mentioned above, with various toner and carrier combinations, using the above copier in a normal temperature and humidity environment (25°C, 55%)
, low temperature and humidity environment (10℃, 15%), high temperature and humidity environment (30℃
, 85%). Regarding the fog on the image, evaluate the toner fog on the white background image,
Ranked. A rank of △ or higher is practically usable, but a rank of ○ or higher is desirable. ●Image texture As described above, images were printed using the above-mentioned copying machine under the same conditions as above, using various toner and carrier combinations. Regarding the 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. ●Image density (I.D.) Copy under the same conditions as above, and I.D. D. was evaluated. The image density of the solid area was measured using a Sakura densitometer and ranked. A rank of △ or above is practically usable, but a rank of ○ or above is desirable. ●Environmental change in charging (△Q) The amount of charge after storing the developer for 24 hours at 10°C and 15% (QLL), and the amount of charging after storing the developer for 24 hours at 30°C and 85% (QHH) ) and find the difference △Q; △Q
=QLL-QHH(μc/g) and rank them as follows.
Environmental changes in charging were evaluated. × means that it is not practical due to large environmental fluctuations, and △ or more means that it is practically usable.
○ indicates that it is desirable.

(Comparative Example 1) The yellow, magenta, cyan, and black toners obtained in color toner production example (■) and the carrier prepared in carrier production example were mixed in a weight ratio of 8:92.
to prepare a full color developer. This developer was evaluated for the above items using a full color copying machine (CF-70; manufactured by Minolta Camera Co., Ltd.).

(Comparative Example 2) The yellow, magenta, cyan, and black toners obtained in color toner production example (■) and the carrier prepared in carrier production example were mixed in a weight ratio of 8:92.
to prepare a full color developer. This developer was evaluated for the above items using a full color copying machine (CF-70; manufactured by Minolta Camera Co., Ltd.).

(Comparative Example 3) The yellow, magenta, cyan, and black toners obtained in color toner production example (■) and the carrier prepared in carrier production example were mixed at a weight ratio of 8:92 to prepare a full color developer. . This developer was evaluated for the above items using a full color copying machine (CF-70; manufactured by Minolta Camera Co., Ltd.).

(Comparative Example 4) The yellow, magenta, cyan, and black toners obtained in Color Toner Production Example (■) and the carrier prepared in Carrier Production Example were mixed at a weight ratio of 8:92 to prepare a full color developer. . This developer was evaluated for the above items using a full color copying machine (CF-70; manufactured by Minolta Camera Co., Ltd.). The above results are shown in Table 1 below.
summarized in.

[0034]

[Table 1]

[0035]

Effects of the Invention The full-color toner of the present invention has little environmental variation in charging performance and can stably produce fine-grained images.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a toner surface on which inorganic fine particles are present in a buried state.

FIG. 2 is a diagram schematically showing a toner surface on which inorganic fine particles are present in an attached state.

Claims (1)

[Claims] 1. A full-color toner for developing electrostatic images, which has silica present in a semi-buried state on the surface and liquid-phase titania or liquid-phase alumina attached to the surface in a non-buried state.