JPS63266461A - Positive chargeable toner - Google Patents

Abstract

PURPOSE:To stabilize the positive chargeability of a toner by using a specified styrene-acrylic copolymer and a specified azine compd. CONSTITUTION:The titled toner contains a copolymer produced by copolymerizing a styrene monomer with an acrylic ester monomer in the presence of an azonitrile initiator such as azobisisobutylnitrile as a fixing medium and an azine compd. of >=6pH such as nigrosine as a positive charge controller. The positively chargeable toner hardly undergoes a change in the extent of positive charge with the lapse of time, is positively charged in a short kick-off time and is hardly scattered.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a positively chargeable toner used in electrophotography, and more specifically, the present invention relates to a positively charged toner used in electrophotography. , relates to a positively chargeable toner that is also excellent in other toner properties.

(Prior Art) Electrophotography is used for purposes such as detailed copying and high-speed printers, but it requires a toner with positive chargeability depending on the type of photoreceptor used.

As a fixing medium for toner, styrene-acrylic copolymer is particularly suitable from the viewpoint of toner moldability, fixability, and offset resistance, but conventional styrene-acrylic copolymer is Most of the toners used were negatively chargeable and were not suitable for use as positively chargeable toners.

JP-A No. 61-219963 discloses a copolymer containing 2 to 15% by weight of an aminoacrylic monomer in the total components and using an azonitrile initiator as a polymerization initiator, and a copolymer containing a metal, A positively chargeable toner containing a metal oxide, metal sulfide, or metal halide is described.

(Problems to be Solved by the Invention) The aminoacrylic monomer in the positively chargeable toner is
This imparts positive chargeability to the toner, but it has the drawback of worsening the pulverizability of the toner. For this reason, the toner contains gold such as metal oxides to improve the crushability.

However, these metal oxides, etc. are not only unnecessary components in toner, but also metal oxides, etc. contained in toner tend to wear out the crusher and classifier. It is desirable not to contain it.

Therefore, an object of the present invention is to provide a positively charged toner for electrophotography that contains a styrene-acrylic copolymer as a fixing medium and exhibits stable positive chargeability.

Another object of the present invention is to reduce the change in the amount of charge over time, to have a fast charging start-up 9, to reduce toner scattering and background fogging, and to provide a combination of toner formability (crushability), fixability, and offset resistance. Another object of the present invention is to provide an excellent positively chargeable toner.

(Means for Solving the Problems) According to the present invention, a copolymer obtained by polymerizing a styrene monomer and an acrylic ester monomer in the presence of an azonitrile initiator is used as a fixing medium. Contains and has a pH of 6
Containing the above azine compound as a charge control agent
- A positively chargeable toner with characteristics is provided.

(Function) The first feature of the toner of the present invention is that a copolymer obtained by polymerizing a styrene monomer and an acrylic ester monomer in the presence of an azonitrile initiator is used as a fixing medium. be. First, the glass transition point (
Tg) can be freely adjusted within a range suitable for the toner, and thereby a desired combination of crushability, fixability, and anti-offset properties for the toner can be obtained.

In addition, in styrene-acrylic copolymers obtained using organic peroxide initiators, which are the most typical among polymerization initiators, acidic substances remain in the resin as initiator decomposition residues (impurities). Therefore, even if a positive charge control agent is blended into this copolymer, this decomposition residue inhibits positive chargeability. On the other hand, in the copolymer resin polymerized using an azonitrile initiator according to the present invention, there is no substance that inhibits positive chargeability, and it is thought that the decomposition residue of the azonitrile initiator rather contributes to positive chargeability. As a result, the positive chargeability of the toner is stabilized.

The second feature of the positively chargeable toner of the present invention is that an azine compound having -6 or more is combined as a charge control agent with the above-described specific copolymer fixing medium. That is, various types of azine compounds for charge control are known depending on their manufacturing conditions, etc., but according to the present invention, those with - of 6 or more are particularly selected from among them, and this is combined with a specific By blending it into a copolymer, a toner can be obtained that has stable positive chargeability, has a fast charging start-up, and has an extremely small change in charge amount over time.

In the present invention, examples of the styrene monomer include vinyltoluene, α-methylstyrene, α-chlorostyrene, etc. in addition to styrene, and examples of the acrylic ester monomer include acrylic acid or methacrylic acid. esters such as methyl ester, ethyl ester, clobyl ester, butyl ester, amyl ester, 2
-Ethylhexyl ester and the like. The copolymerization ratio of the styrene monomer and the acrylic ester monomer can be varied, but for the above-mentioned purpose, the copolymerization ratio of the styrene monomer and the acrylic ester monomer is 5:95. to 95:5. In particular, it is desirable to use them in combination at a weight ratio of 10:90 to 90:10.

The polymerization initiator used in the polymerization of these monomers is an azonitrile, preferably an azobisnitrile represented by the formula %, where R1, R2, R3 and R4 are hydrogen atoms or alkyl groups. , suitable examples thereof include azobisisobutylnitrile, azobisisovaleronitrile, and the like. The amount of the azonitrile initiator used may be a so-called catalytic amount, generally 0.05 to 5% by weight, particularly 0.1 to 3% by weight based on the total amount of monomers.
It is best to use the amount of %.

Copolymerization can be carried out by methods known per se, such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization.

The styrene-acrylic copolymer used in the present invention has a molecular weight of 1, generally 1,000 to 40,000, particularly 2,000 to 3,000.
It is preferable to have a number average molecule i (Mn) of 0, and the molecular weight distribution represented by the ratio (My/Mn) of the weight average molecular weight (Ml) to the number average molecule it (Mn) is 3.
5 to 40. In particular, it is desirable that it be within the range of 4.0 to 30. Further, the glass transition point (Tg) is generally 40 to 110°C, particularly 50 to 100°C, and the ring and ball softening point is preferably in the range of 100 to 170°C, particularly 110 to 160°C.

Examples of the azine compound used as a charge control agent include nigrosine and nigrosine paste. This product is obtained by adding a small amount of iron chloride to a mixture of aniline, aniline hydrochloride, and nitrobenzene, heating the mixture, and sulfonating the resulting dye with sulfuric acid if necessary.In this case, the degree of sulfonation, Various products can be obtained depending on the degree of neutralization and the degree of purification by washing with water.

A charge control agent suitable for the purposes of the present invention is available from Orient Chemical Industry Co., Ltd. under the trade name BONTRON N-01. The charge control agent is preferably used in an amount of 0.5 to 10% by weight, particularly 1 to 5% by weight, based on the aforementioned copolymer fixing medium.

In addition to the above-mentioned essential components, the positively chargeable toner of the present invention may contain toner compounding agents known per se, such as coloring pigments such as carmen black, olefin resin non-releasing agents such as low molecular weight polypropylene, etc. . The coloring pigment is preferably used in an amount of 2 to 20% by weight per fixing medium, and the release agent is preferably used in an amount of 91 to 10% by weight per fixing medium.

Toner particles are produced by blending the above-mentioned components, kneading at a temperature higher than the softening point of the resin, and pulverizing this mixed wire composition.
Then, the classification operation is easily carried out.

The particle size of the toner particles is preferably such that the average particle size is in the range of 7 to 15 microns. In order to adjust the fluidity of the toner particles, a fluidity regulator based on vapor phase aluminum oxide may be added to the surface of the toner particles.

The toner of the present invention is used for developing a negative electrostatic latent image by forming a magnetic brush in the form of a two-component developer mixed with a magnetic carrier such as iron powder or ferrite. The toner is preferably used in an amount of 1 to 15% by weight, particularly 2 to 122 parts by weight, based on the developer.

(Effects of the Invention) According to the present invention, a toner that uses a styrene-acrylic copolymer and has stable positive chargeability is provided, and this toner has little change in charge amount over time and also has a rise in charge. As a result, it has the advantage of less toner scattering and background capri, and also has an excellent combination of toner formability, fixing property, and offset resistance.

Examples will be described below, but the present invention is not limited thereto.

Example 1 Styrene/n-butyl acrylate copolymer (composition ratio 70
:30,M,,=198,000.

Mn=9860, M, /Mn=20.08, T
g=65.1℃, ring and ball softening point=130.5℃) 100
Parts by weight, Carmen Black (Mitsubishi Kasei 144) 10 parts by weight, Polypropylene (Sanyo Kasei H; Visco-/l/
660P) 2 parts by weight, and an azine compound (pi(6,
8, manufactured by Orient Kagaku Kogyo; Gentron N-01) was mixed by melting, and then pulverized using Jetmi A/ and classified to produce a toner having a particle size of 5 to 25 μm.

When 5 parts of the toner and 95 parts of ferrite carrier were mixed and a continuous copying test was conducted using a copier DC-111 manufactured by Sanda Kogyo, which was modified to form a negatively charged latent image,
Even after copying 100,000 sheets, good images were obtained with no decrease in image density and no background capri. Also, 10℃, 15SRH
Similar copying tests were conducted under the low temperature and low humidity conditions of 35 DEG C. and 85 SRH, and even under these special environments, good images were obtained without any reduction in image ambiguity or background capri.

Furthermore, after a developer made of the toner and ferrite carrier was stirred and triboelectrically charged, it was allowed to stand at room temperature and humidity for 90 days, and Figure 1 shows the change in the amount of charge. As is clear from the figure, the initial charge amount (15.5μ
C/9) hardly decreased to 15μ even after 90 days.
C/! i was shown. Furthermore, Figure 2 shows the change in the amount of charge with respect to the mixing and stirring time.
After a few minutes, the desired amount of charge (approximately 15μc7g) was reached, indicating that the charge buildup was quick. Incidentally, the amount of charge was measured by the blow-off method.

Comparative Example-1 Styrene/n-butyl acrylate copolymer obtained by solution polymerization using benzoyl peroxide as a polymerization initiator in an amount of 2% by weight based on the total monomer weight (composition ratio 70:30,
M,,=165,000,M,=7100.

M,, 7Mn=23.2, Tg=62.8°C, ring and ball softening point=126.4°C) 1! -1 A toner was produced in exactly the same manner as in Example 1, except that the copolymer used in Example 1 was replaced.

A test similar to Example 1 was conducted using a developer prepared by mixing 5 parts of the toner and 95 parts of ferrite carrier. In a copying test, there was a lot of background capri and toner scattering inside the machine after 100,000 sheets were printed. Furthermore, under special circumstances, the image density decreased. As is clear from Figure 1, the change in the amount of charge over 90 days shows that the initial amount of charge decreases to half after 90 days, and as shown in Figure 2, the initial amount of charge decreases to half after 10 minutes. Even if mixed and stirred, the desired band [i (approximately 15 μC/I
i) was not achieved.

Comparative Example-2 The azine compound with a voice value of 6.8 used in Example 1 was changed to a voice value of 3,
A toner was produced in exactly the same manner except that the azine compound No. 2 (manufactured by Orient Chemical Industry Co., Ltd.: ?Ntron N-05) was used.

A developer was obtained by mixing 5 parts of the toner and 95 parts of ferrite carrier, and the same test as in Example 1 was conducted. In the copy test, there were many background capris through 100,000 copies,
There was significant toner scattering. Furthermore, under special environments, the image density decreased.

As can be seen from Figure 1, the initial charge amount decreased to less than half after 90 days. Also, in the case of charging start-up 9, a satisfactory result was not obtained as in Comparative Example-1.

Comparative Example-3 100 parts by weight of the copolymer used in Comparative Example 1, 10 parts by weight of Chikara Den Black (manufactured by Mitsubishi Kasei; $44), 2 parts by weight of polypropylene (manufactured by Sanyo Chemical: Pisco/L/660-P) A toner was produced in the same manner as in Example 1 using 5 parts by weight of an azine compound having a -value of 3.2.

A developer was obtained by mixing 5 parts of the toner and 95 parts of 7-product light carrier, and the same test as in Example 1 was conducted. In the copying test, after 100,000 sheets, there was a noticeable occurrence of background capri and toner scattering, which was the worst condition. Furthermore, under special circumstances, the image density was significantly reduced. 9
As for the change in the amount of charge during 0 days, the desired amount of charge was not obtained from the beginning, and there was almost no charge after 90 days.

Furthermore, the charging start-up was poor, and even after stirring for 10 minutes, the amount of charging did not reach even half of the desired amount.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the change in the amount of charge when a developer comprising a toner and a ferrite carrier according to the present invention is stirred and triboelectrified and then left for 90 days at room temperature and pressure. FIG. 2 is a diagram showing changes in the amount of charge with respect to mixing and stirring time.

Claims (1)

[Claims] (1) Contains a copolymer obtained by polymerizing a styrene monomer and an acrylic ester monomer in the presence of an azonitrile initiator as a fixing medium, and uses an azine compound with a pH of 6 or more as a charge control agent. A positively chargeable toner comprising: