JP2736574B2 - 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 for copiers and printers, and more particularly to a method for controlling the change of environment such as temperature and humidity by adding hydrophobic amorphous titanium oxide ultrafine particles to toner. On the other hand, the charge amount is stable,
The present invention relates to a dry developer that makes a copy image clear.

[0002]

2. Description of the Related Art
In a dry developer for developing an electrostatic latent image comprising a positively chargeable carrier and a negatively chargeable toner, 0.05 to 1.0% by weight of the negatively chargeable toner is added to the toner as a post-processing agent. Silica fine powder (average particle diameter 100 mμ or less)
1 to 3.0% by weight of a hydrophobic titanium oxide fine powder (average particle diameter of 100 μm or less), and the weight ratio of both fine powders is 1: 5 to
A dry developer for developing an electrostatic latent image which is added in a 1: 1 ratio has been proposed (Japanese Patent Publication No. 2-27664). In this dry developer for developing an electrostatic latent image, a decrease in the initial charge amount and a decrease in the fluidity are suppressed by adding hydrophobic silica fine powder, and the charge amount increases with repetition of copying. The disadvantages of the hydrophobic silica fine powder are prevented by utilizing the property of the hydrophobic titanium oxide fine powder, which tends to reduce the charge amount, and as a whole, the flowability is good and regardless of the repetition of copying, An attempt is being made to obtain a developer having a stable charge amount.

However, in the present invention, the hydrophobic titanium oxide fine powder is crystalline, so that the difference in the amount of water vapor adsorbed between summer conditions of high temperature and high humidity and winter conditions of low temperature and low humidity causes the charge amount to be reduced. Fluctuates greatly, which is a fatal disadvantage in practical use. Furthermore, since the hydrophobic titanium oxide fine powder has high cohesiveness and low transparency, there is a disadvantage that the sharpness of a copy image is poor.

On the other hand, there has been proposed a dry developer characterized by containing amorphous (spherical) and spherical titanium oxide fine particles (Japanese Patent Application Laid-Open No. 62-28772). However, since the fine titanium oxide powder used in the present invention is hydrophilic, there is a problem that the control of the initial charge amount is insufficient.

[0005]

The inventors of the present invention have conducted intensive studies to solve such conventional problems, and as a result, pyrolyzed or hydrolyzed a volatile titanium compound in the gas phase. Immediately after the formation of the amorphous titanium oxide ultrafine particles, the titanium oxide ultrafine particles obtained by treating the surface of the particles with an organosilane compound in the gas phase are amorphous, In addition, despite the fact that it contains a large amount of adsorbed water, it is noted that it has high hydrophobicity, and also has high dispersibility and transparency. When added to the toner, it has been found that the amount of charge is stable against environmental changes such as temperature and humidity, and a clear copy image can be obtained. Based on this finding, the present invention has been completed.

That is, according to the present invention, after the volatile titanium compound is thermally decomposed or hydrolyzed in the gas phase to produce ultrafine amorphous titanium oxide particles, the surface of the particles is immediately and continuously treated in the gas phase with an organometallic compound. A dry developer in which amorphous and hydrophobic ultrafine titanium oxide particles obtained by treating with a silane compound are added to a toner at a ratio of 0.01 to 5% by weight. is there.

The amorphous and hydrophobic titanium oxide ultrafine particles used in the present invention are obtained by thermally decomposing or hydrolyzing a volatile titanium compound in a gas phase and serving as a core. Is immediately obtained by treating the surface of the particles with an organosilane compound in the gas phase . Here, a specific method for producing amorphous titanium oxide ultrafine particles serving as a nucleus is disclosed in JP-A-60-18641.
No. 8 and JP-A-61-201604.

That is, the volatile titanium compound is vaporized or atomized using a carrier gas (diluent gas) such as argon, helium, nitrogen, oxygen or air, and heated (at 600 ° C. or lower, preferably 250 to 350 ° C.). By mixing with water vapor at (under heating at a temperature of.degree. C.) to cause hydrolysis, or by heating to a temperature equal to or higher than the decomposition temperature and thermally decomposing, amorphous titanium oxide ultrafine particles serving as nuclei can be produced.

The type of the volatile titanium compound used as the raw material is not particularly limited, and has a volatility such as chloride, alkoxide and acetylacetonate of titanium, and is thermally decomposed or hydrolyzed in a gas phase. In this case, what generates amorphous titanium oxide ultrafine particles may be used.
These can be used alone or in combination of two or more.

In the present invention, after the titanium oxide ultrafine particles serving as a nucleus are generated by the gas phase method as described above, a vaporized or atomized organosilane compound is immediately mixed with the titanium oxide ultrafine particles. Subsequently, the particles are treated in the gas phase, and the surface of the particles is treated with an organosilane compound.

Here, the organosilane compound may be appropriately selected depending on the purpose and reactivity of the surface modification, and is not particularly limited. Specifically, for example, silane, alkylalkoxysilane, siloxane, polysiloxane,
What has volatilization, such as a coupling agent, and has a hydrophobic group and a reactive group which couple | bonds with titanium should just be used.
Among these, 1,2,3,4-tetramethyltetracyclosiloxane and the following general formula (I)

[0012]

Embedded image RnSi (OR ′) _4-n (I)

(Wherein, n represents an integer of 1 to 3, R, R ′
Represents an alkyl group or a phenyl group, respectively. )

It is preferable to use an alkylalkoxysilane represented by the formula:

Examples of the alkylalkoxysilane represented by the above general formula (I) include, for example, isobutyltrimethoxysilane, trimethylmethoxysilane, phenyltrimethoxysilane, octyltriethoxysilane and the like, with isobutyltrimethoxysilane being particularly preferred. .

In the present invention, such an organosilane compound is vaporized or atomized, mixed with a carrier gas and ultrafine titanium oxide particles as nuclei, and treated in a gas phase.

Here, the method for vaporizing or atomizing the volatile titanium compound or the organosilane compound is not particularly limited, and is determined by the vapor pressure, the thermal decomposition temperature, etc. of each substance. Bubbling method, spray method,
An ultrasonic spray method or the like is used. In the case of a substance which is solid at room temperature, it may be heated to sublimate, or may be melted and evaporated, or may be dissolved in a solvent and then supplied by the above-described various methods. Thus, amorphous and hydrophobic ultrafine titanium oxide particles used in the present invention can be obtained.

Hereinafter, the present invention will be described using an amorphous and
An example of a method for producing hydrophobic titanium oxide ultrafine particles,
This will be specifically described with reference to the drawings. FIG. 1 is a schematic view showing one embodiment of an apparatus used for producing amorphous titanium oxide ultrafine particles used in the present invention.

First, the volatile titanium compound as described above is sent to an evaporator 2 by a charge pump 1 to be vaporized or atomized, and is reacted by a carrier gas (nitrogen gas or the like) supplied from a carrier gas cylinder 3. To the ultrafine particle producing section 4A of the vessel 4.

On the other hand, if necessary, water is introduced into the heater 5 together with the carrier gas to prepare heated steam, and this heated steam is simultaneously sent to the ultrafine particle producing section 4A, and
Hydrolysis (or thermal decomposition) under heating at a temperature of 00 ° C. or less, preferably 250 to 350 ° C., produces amorphous titanium oxide ultrafine particles as nuclei.

The average particle diameter of the titanium oxide ultrafine particles as the nucleus is 0.005 to 0.1 μm, preferably 0.01 to 0.0 μm.
5 μm, and the particle size distribution is 0.001 to 0.5 μm, preferably 0.005 to 0.1 μm. The amount of water introduced at this time is not particularly limited. However, by setting the amount of water to be at least 5 times the theoretical amount necessary for hydrolyzing the volatile titanium compound, the particles of the titanium oxide ultrafine particles serving as nuclei can be obtained. The diameter can be reduced, and the transparency can be further improved. For the same reason, it is also effective to lower the concentration of the volatile titanium compound and to rapidly mix the volatile titanium compound with water.

Next, as described above, the titanium oxide ultrafine particles serving as nuclei produced in the ultrafine particle producing section 4A in the reactor 4 are subsequently introduced into the mixing and reforming section 4B in the reactor 4. ,
Here, the vaporized or atomized organosilane compound is mixed by the evaporator 2 ″ and processed in the gas phase.

FIG. 2 is an explanatory view showing one embodiment of the mixed reforming section 4B. In the figure, reference numeral 6 denotes a flow path of titanium oxide ultrafine particles A serving as a nucleus, and reference numeral 7 denotes an organosilane compound B.
It is a flow path. Here, the angle α between the flow path 6 of the titanium oxide ultrafine particles A serving as a nucleus and the flow path 7 of the organosilane compound B is not particularly limited, but is preferably 0 to 90 °. When a volatile organosilane compound that is easily decomposed is used, if the angle is outside this range, ultrafine particles of the organosilane compound alone are generated and the surface is not modified,
It is not preferable because it tends to be a mixture of ultrafine particles.
FIG. 2 shows the case where the angle α between the two flow paths is 45 °.

As described above, the organosilane compound is vaporized or atomized by the evaporator 2 ″, supplied to the mixing and reforming section 4B together with the carrier gas, and mixed with the ultrafine titanium oxide particles serving as nuclei.

When the ultrafine titanium oxide particles serving as the nucleus and the organosilane compound are mixed, it is preferable that any one of the following cases (1) to (3) is satisfied. (1) First, the concentration of the organosilane compound is
The concentration is preferably equal to or lower than the concentration of the volatile titanium compound which is the raw material of the titanium oxide ultrafine particles to be the core. The concentration herein refers to the total mol amount of all gases including carrier gas, volatile titanium compound, organosilane compound, water vapor (when hydrolyzed) and other gases.
Mol of volatile titanium compound or organosilane compound
Indicates the percentage of the amount. Here, when the concentration of the organosilane compound is equal to or higher than the concentration of the volatile titanium compound, if the organosilane compound is easily decomposed, ultrafine particles of the organosilane compound alone are generated, and the surface modification is not performed. It is not preferable because it may be a mixture of ultrafine particles of a volatile titanium compound and an organosilane compound.

(2) Next, the mixing of the ultrafine titanium oxide particles and the organosilane compound is performed so that the ratio u ₂ / u ₁ of the former flow rate u ₁ to the latter flow rate u ₂ is 0.1 or more. Preferably, the reaction is performed so as to be usually 0.1 to 10, more preferably 0.2 to 5, and still more preferably 0.5 to 3.
And When a volatile titanium compound that is easily decomposed is used, mixing at a flow rate ratio outside this range generates ultrafine particles of the organosilane compound alone, surface modification is not performed, and the volatile titanium compound, There is a possibility that separate ultrafine particles of the silane compound are generated.

(3) There is a case where it is not necessary to correspond to the above (1) or (2). That is, the particle size obtained when the organosilane compound is hydrolyzed or thermally decomposed under the same conditions as when the volatile titanium compound is hydrolyzed or thermally decomposed in the gas phase becomes the titanium oxide serving as the core. The average particle diameter of the ultrafine particles is more than, preferably 2 times or more, more preferably 5 times or more, or low reactivity which does not generate particles by itself is used. Compounds satisfying such conditions include, for example, isobutyltrimethoxysilane, trimethylmethoxysilane, phenyltrimethoxysilane, octyltriethoxysilane, and the like. As described above, it is preferable that the angle α between the flow paths is set to be 0 to 90 ° when the two are mixed as described above.

The mixture thus properly mixed is processed in the gas phase in the mixing and reforming section 4B. The reaction temperature at this time is 0 to 400 ° C, preferably 100 to 300 ° C.
It is. Here, when the reaction temperature is 400 ° C. or higher, the organosilane compound is easily decomposed, and the hydrophobicity is easily lowered. At the time of this reaction, steam, ammonia, amines such as stearylamine and the like may be supplied in order to promote the decomposition of the organosilane compound and to promote the reaction on the surface of the amorphous titanium oxide ultrafine particles.

The residence time from the generation of the ultrafine titanium oxide particles to the mixing with the organosilane compound is within 1 minute, preferably within 10 seconds, more preferably within 1 second. If the residence time is 1 minute or more, the aggregation of the amorphous titanium oxide ultrafine particles serving as the nucleus proceeds, and it becomes impossible to make the surface hydrophobic at the ultrafine particle level. Furthermore, the residence time and flow rate in the reactor after mixing the organosilane compound are not particularly limited, but usually, the residence time is 0.01 to 10 seconds, and the flow rate is 0.01 to 50 m.
/ S range.

As described above, the surface-modified ultrafine titanium oxide particles (amorphous hydrophobic ultrafine titanium oxide particles) used in the present invention are obtained. The fact that the surface-modified ultrafine titanium oxide particles are amorphous
It is clarified by X-ray diffraction analysis and is spherical. The method for collecting the obtained surface-modified titanium oxide ultrafine particles is not particularly limited, and may be performed using a usual filter, an electric dust collector, or the like. In FIG.
An example in which the surface-modified ultrafine titanium oxide particles are collected using the filter 8 is shown.

The hydrophobicity of the surface-modified ultrafine titanium oxide particles thus obtained is usually 30 to 80% in terms of hydrophobicity measured by a water-methanol titration method. Details of the water-methanol titration method will be described later. Since the ultrafine particles are amorphous, they contain 1 to 10% by weight of adsorbed water. Since it contains a large amount of adsorbed water, it has the characteristic that it is hardly affected by temperature and humidity environment.

In the present invention, the hydrophobic ultrafine titanium oxide particles thus obtained are added to the toner. In addition, you may add to a carrier as needed. In this case, the carrier is added to the coating layer of the core particles. Here, as the constituent components of the toner, known components can be arbitrarily used, and in addition to a binder resin and a colorant, a magnetic substance, a charge control agent, and the like can be used. As the binder resin, for example, polyester, polystyrene, styrene acrylic resin, methacrylic resin, a derivative thereof, or a mixture thereof can be used. As a coloring agent, a pigment such as carbon black or a dye may be appropriately used.

The compounding amount of the hydrophobic amorphous titanium oxide ultrafine particles in the toner is 0.01 to 5% by weight, preferably 0.1 to 3% by weight. When the blending amount of the hydrophobic amorphous titanium oxide ultrafine particles is less than 0.01% by weight, the effect of stabilizing the charge amount is not sufficiently obtained. On the other hand, when the blending amount exceeds 5% by weight, the effect is not changed. Is uneconomical.

There is no particular limitation on the method of blending the hydrophobic amorphous titanium oxide ultrafine particles into the toner. The blending is performed during the production of the toner, and the mixture is kneaded with a roll mill, a Hensiel mixer, a twin-screw extruder, or the like, and then bin-milled or jet-milled. And the like, or may be added to and mixed with the finished toner.

[0035]

Next, the present invention will be described in detail with reference to examples.

Example 1 (1) Hydrophobic amorphous titanium oxide ultrafine particles
Abbreviated as hydrophobic titania. 1) Using the apparatus shown in FIG. 1, hydrophobic titania A was manufactured as follows. Titanium tetraisopropoxide (T
i (O-iC ₃ H ₇ ) ₄ ) was charged to the charge pump 1 at 24.1 g / hr.
The nitrogen gas in the carrier gas cylinder 3 (1.
(5 Nm ³ / hr) and introduced into the evaporator 2 heated to 200 ° C. to completely vaporize the raw material. On the other hand, using a charge pump 1 ′, 1127 g / hr of water was vaporized in an evaporator 2 ′ together with nitrogen gas (0.15 Nm ³ / hr) in a carrier gas cylinder, and further heated to 500 ° C. 5
And heated steam was prepared. The excess amount of water vapor at this time was 368 times the theoretical amount. This heated steam is supplied to the reactor 4 together with the raw material vaporized as described above.
To the ultrafine particle production section 4A of the reactor 4,
The raw material was hydrolyzed at a temperature of 260 ° C. to synthesize ultrafine titanium oxide. At this time, the speed of feeding into the reactor 4 was 18.3 m / s on the raw material side and 11.7 m / s on the steam side.
The flow rate in the reactor 4 after mixing was 21.9 m / s.

On the other hand, isobutyltrimethoxysilane (iC ₄ H ₉ Si (OCH ₃ )) is used as an organosilane compound for surface modification.
₃ ) was converted to nitrogen gas (1.5 Nm) in the carrier gas cylinder 3 at a flow rate of 10.8 g / hr using the charge pump 1 ′.
³ / hr), and introduced into an evaporator 2 ′ heated to 200 ° C. to completely vaporize the raw materials. The vaporized isobutyltrimethoxysilane is mixed with the ultrafine particulate titanium oxide and the nitrogen stream containing the heated steam in the mixing and reforming section 4B in the reactor 4 and reacted at 260 ° C. Hydrophobic ultrafine titanium oxide particles whose surfaces were modified with organosilane were obtained. At this time, the angle α formed between the flow path 6 and the flow path 7 of the mixing and reforming section 4B was 90 °. The rate at which the vaporized isobutyltrimethoxysilane is fed into the mixing and reforming section 4B is 18.3 m / s, the flow rate of the ultrafine titanium oxide is 21.9 m / s, and The flow velocity in the mixed reforming section 4B was 2.5 m / s. The residence time from the generation of the ultrafine titanium oxide particles to the mixing with isobutyltrimethoxysilane was 0.46 millisecond, and the residence time in the mixed reforming section 4B was 0.12 seconds. . The properties of the obtained hydrophobic titania A are shown in Table 1 below.

[0038]

[Table 1]

(2) Production and evaluation of dry developer Thermoplastic polyester resin (number average molecular weight: about 600
0) A mixture of 95 parts by weight, 4 parts by weight of carbon black MA100 (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), and 1 part by weight of the hydrophobic titania A obtained in (1) above was kneaded with a roll mill at 150 ° C. for 20 minutes. After that, the mixture was pulverized using a jet mill to obtain a toner having an average particle diameter of 9 μm. 200 g of the above toner and a carrier (made by Nippon Iron Powder, trade name:
EFV250 / 400) was mixed to prepare a two-component dry developer. This developer was placed in an electrophotographic apparatus (trade name: PPC-900, manufactured by Ricoh Co., Ltd.) and subjected to summer conditions (30 ° C., 80%
RH) and winter conditions (10 ° C, 15% RH), continuous 3000
A zero-sheet copy test was performed, and the charge amount of the toner before and after the test was measured by a blow-off method, and the image density and background density at the beginning and end of the test were measured with a reflection densitometer, respectively, and the toner scattering amount and image sharpness were measured. evaluated. These results are described in the second section below.
It is shown in the table.

Example 2 (1) Production of Hydrophobic Titania B In Example 1 (1), phenyltrimethoxysilane (iC ₄ H ₉ Si (OCH ₃ ) ₃ ) was used instead of isobutyltrimethoxysilane as the organosilane compound. Methoxysilane (C ₆ H ₅ Si (OC
The same operation as in Example 1 (1) was carried out except that H ₃ ) ₃ ) was supplied at a flow rate of 12.1 g / hr.
Was manufactured. (2) Production and evaluation of dry developer The same procedure as in Example 1 (2) was carried out except that the hydrophobic titania B obtained in the above (1) was used. The results are shown in Table 2 below.

Example 3 (1) Production of Hydrophobic Titania B In Example 1 (1), instead of isobutyltrimethoxysilane (iC ₄ H ₉ Si (OCH ₃ ) ₃ ), trimethylmethoxy was used as the organosilane compound. Silane ((CH ₃ ) ₃ SiOCH ₃ )
Example 1 except that was supplied at a flow rate of 8.8 g / hr.
The same operation as in (1) was performed to produce hydrophobic titania C. (2) Production and Evaluation of Dry Developer The procedure was the same as in Example 1 (2), except that the hydrophobic titania C obtained in (1) was used. The results are shown in Table 2 below.

Example 4 (1) Production of Hydrophobic Titania B In Example 1 (1), instead of isobutyltrimethoxysilane (iC ₄ H ₉ Si (OCH ₃ ) ₃ ), 1, The same operation as in Example 1 (1) was performed except that 2,3,4-tetramethyltetracyclosiloxane (-(-CH ₃ HSiO-)- ₄ ) was supplied at a flow rate of 14.8 g / hr. And hydrophobic titania D. (2) Production and evaluation of dry developer The same procedure as in Example 1 (2) was carried out except that the hydrophobic titania D obtained in the above (1) was used. The results are shown in Table 2 below.

Example 5 In Example 1 (2), a thermoplastic polystyrene resin (number average molecular weight:
Except for using about 9000), the same operation as in Example 1 (2) was performed. The results are shown in Table 2 below.

Example 6 Thermoplastic polyester resin (number average molecular weight: about 6000) 9
5 parts by weight, carbon black MA100 (Mitsubishi Chemical Industries)
4 parts by weight were kneaded with a roll mill at 150 ° C. for 20 minutes, and then pulverized using a jet mill.
The same operation as in Example 1 (2) was performed except that 1 part by weight of the hydrophobic titania A produced in (1) was added and mixed to obtain a toner having an average particle diameter of 9 μm. The result is the second
It is shown in the table.

Comparative Example 1 In Example 1 (2), instead of hydrophobic titania A, as hydrophobic titania, Aerosil T805 (anatase type, titania P-25 manufactured by Degussa) was hydrophobized with octyltrimethoxysilane. Ex.) Was performed in the same manner as in Example 1 (2). The results are shown in Table 2 below.

Comparative Example 2 (1) Production of Ultra-Hydrophilic Amorphous Titanium Oxide Fine Particles The procedure of Example 1 (1) was repeated, except that no organosilane was supplied. And hydrophilic ultrafine titanium oxide particles were produced. (2) Production and evaluation of dry developer The procedure was the same as in Example 1 (2) except that the hydrophilic amorphous titanium oxide ultrafine particles obtained in (1) above were used. The results are shown in Table 2 below.

[0047]

[Table 2]

According to Table 2, the dry developing agents of Examples 1 to 6 are different from the dry developing agents of Comparative Examples 1 and 2 in that the toner is charged under the high-temperature and high-humidity summer condition and the low-temperature and low-humidity winter condition. It can be seen that since the amount is constant, the image density is high and the background density is low, that is, the amount of toner scattered is small, and a clear image can always be obtained even if the annular condition changes.

[0049]

The surface of the hydrophobic ultrafine titanium oxide particles used in the present invention is hydrophobized in the form of ultrafine particles, and the amount of water adsorbed inside the particles is large. Titanium oxide ultrafine particles that are stable at a high level of property. In the present invention, since such hydrophobic amorphous titanium oxide ultrafine particles are added to the toner, the toner is stable in a state in which the charging characteristics are high with respect to changes in the temperature and humidity environment, and a clear dry image of a copy image is obtained. Has become a developer.

[0050]

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of an apparatus used for producing ultrafine amorphous titanium oxide particles used in the present invention.

FIG. 2 is an explanatory diagram showing one embodiment of a mixed reforming section in a reactor.

[Explanation of symbols]

 1,1 ', 1' 'charge pump 2,2', 2 '' evaporator 3 carrier gas cylinder 4 reactor 4A ultrafine titanium oxide production section 4B mixing reforming section 5 heater A ultrafine titanium oxide B organosilane compound 6 Flow path of ultrafine titanium oxide 7 Flow path of organosilane compound 8 Filter

Continuation of the front page (56) References JP-A-4-40467 (JP, A) JP-A-60-186418 (JP, A) JP-A-61-1201604 (JP, A) JP-A-4-348354 (JP, A) JP-A-4-188148 (JP, A) JP-A-62-28772 (JP, A)

Claims (3)

(57) [Claims] After the volatile titanium compound is thermally decomposed or hydrolyzed in the gas phase to produce amorphous titanium oxide ultrafine particles, the surface of the particles is immediately and continuously treated with an organosilane compound in the gas phase. A dry type developer obtained by adding amorphous and hydrophobic ultrafine titanium oxide particles to a toner at a ratio of 0.01 to 5% by weight obtained by the treatment. 2. The dry developer according to claim 1, wherein the amorphous and hydrophobic ultrafine titanium oxide particles contain 1 to 10% by weight of adsorbed water. 3. An organosilane compound represented by the general formula (I): RnSi (OR ′) _4-n (I) (wherein n represents an integer of 1 to 3, and R and R ′ are , Each of which represents an alkyl group or a phenyl group.).