JPH08114942A - Electrophotographic developer - Google Patents

Abstract

PURPOSE: To obtain a toner preventing offsetting phenomenon in a low temp. region and capable of improving low-temp. fixability and the dispersibility of a material by melting and kneading. CONSTITUTION: This electrophotographic developer (toner) contains a colorant, styrene resin and low mol.wt. polyethylene wax having a wt. average mol.wt. Mw of <1,000.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a developer for electrophotography. More specifically, the present invention relates to an electrophotographic developer which contains a specific low molecular weight polyethylene wax, prevents the occurrence of an offset phenomenon in a low temperature region, and has excellent fixability.

[0002]

2. Description of the Related Art A method called a heating roller fixing method is generally used in which a heated fixing roller is used to fuse a toner image obtained by using an electrophotographic developer (hereinafter referred to as toner) to a transfer paper. Are known. However,
In this method, since the surface of the fixing roller and the toner image are in pressure contact with each other in a heating and melting state, a part of the toner image adheres to the surface of the fixing roller and is transferred, and this is a so-called offset in which it is transferred again to the next sheet to be fixed. A phenomenon may occur and the sheet to be fixed may be smeared. Therefore, preventing the toner from adhering to the surface of the fixing roller is one of the essential requirements in the heating roller fixing method.
Therefore, in Japanese Examined Patent Publication No. 57-52574, a low molecular weight polyethylene having a weight average molecular weight Mw of about 1,000 to 10,000 is used as a toner component in order to efficiently perform good heating roller fixing without causing a toner offset phenomenon. Proposed.

[0003]

However, as the low temperature fixing of toner progresses in recent years, it is required to prevent the offset phenomenon and to improve the fixing strength especially in the low temperature region, and the molecular weight as described above is required. Using low molecular weight polyethylene having a range as a toner component,
There is a problem that a toner having stable performance cannot be obtained in a low temperature region.

The present invention has been made to solve the above-mentioned conventional problems, and prevents an offset phenomenon in a low temperature region, and at the same time, fixes the material at a low temperature and melt-kneads the materials (charge control agent, carbon black, etc.). It is an object of the present invention to provide a toner having improved dispersibility.

[0005]

The electrophotographic developer (toner) of the present invention is an electrophotographic developer containing a colorant, a styrene resin and a low molecular weight polyethylene wax, and the weight of the low molecular weight polyethylene wax is The average molecular weight Mw is Mw <1000. When the weight average molecular weight Mw of the low molecular weight polyethylene wax used as a component of the toner according to the present invention is in the range of 600 to 800,
It is preferable because the low-temperature fixability is further improved. Further, the ratio of the weight average molecular weight Mw to the number average molecular weight Mn of the low molecular weight polyethylene wax is preferably Mw / Mn ≦ 1.5 for the same reason as above.

The low-molecular-weight polyethylene wax contained in the toner according to the present invention preferably has a low viscosity, and particularly has a melt viscosity at 130 ° C. of 50 cp or less, preferably 7 to 20 cp. In addition, the softening point of the low molecular weight polyethylene wax is 1 in order to lower the fusion temperature.
It is effective that the temperature is 20 ° C or lower, preferably 90 to 110 ° C.

As a result, the low-molecular-weight polyethylene wax contained in the toner according to the present invention exhibits a low-viscosity liquid when heated, so that when the toner containing the wax contacts the heated fixing roller, The low molecular weight polyethylene wax is liquefied and released on the toner surface,
Cover the surface of the fuser roller. Due to the releasability inherent in the low-molecular-weight polyethylene wax covering the surface of the fixing roller, the melted toner does not adhere to the surface of the fixing roller and the occurrence of the offset phenomenon is prevented.

Such a releasing effect is obtained not only when using a fixing roller whose surface is made of a releasing material, but also when using a fixing roller whose surface is made of a metal which is generally considered to have no releasing property. Is recognized. Therefore, when the toner according to the present invention is used, the offset phenomenon of the toner can be prevented and the fixing strength can be improved in a low temperature range without using a fixing roller having a surface formed of a releasing material. To be

The toner according to the present invention may contain various compounds having a releasing action other than the low molecular weight polyethylene wax in combination with the low molecular weight polyethylene wax. Examples of these compounds include cadmium salt of stearic acid, barium salt, lead salt, iron salt, nickel salt, cobalt salt, copper salt, strontium salt, calcium salt or magnesium salt, zinc salt of oleic acid, manganese salt, and iron salt. Salt, cobalt salt, copper salt, lead salt,
Or magnesium salt, zinc salt of palmitic acid, cobalt salt, copper salt, magnesium salt, aluminum salt or calcium salt, zinc salt of linoleic acid, cobalt salt or calcium salt, zinc salt of ricinoleic acid or cadmium salt, of caprylic acid Fatty acid metal salts such as lead salts and lead salts of caproic acid, relatively low molecular weight polypropylene, higher fatty acids having 28 or more carbon atoms, natural or synthetic paraffins, bis fatty acid amides such as ethylenebisstearoyl amide, etc. These compounds can be included alone or in combination of two or more.

The addition amount of these compounds to the toner is generally 0.1% with respect to 100 parts by weight of the resin component of the toner.
It is about 1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. By adding these compounds to the toner, the compatibility of the low molecular weight polyethylene wax with the resin component is further improved, and the colorant and the electrostatic charge can be improved. Similarly, the dispersibility of other toner additives such as a control agent is further improved. Further, when the resin component has a relatively fragile property, it can be prevented from being over-pulverized in the pulverizing step during the production of the toner, and the desired particle size can be obtained in a high yield. You can Further, the stability of the toner is increased, the triboelectric chargeability is not changed even during long-term use, and the life of the toner can be remarkably extended. Incidentally, various other toner additives can be added to the toner according to the present invention, if necessary.

A styrene resin is used as a resin component contained in the toner according to the present invention. The styrene resin may be a homopolymer of styrene or a copolymer of styrene and another vinyl monomer. Monomers for forming these copolymers include olefins such as p-chlorostyrene, vinylnaphthalene, ethylene, propylene, butylene, isobutylene, and vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride. Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate. Α-methylene aliphatic monocarboxylic acid esters such as 2-chloro-ethyl acrylate, phenyl acrylate, α-chloromethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, Meta Acu Lilonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc., vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, etc., eg N
There are N-vinyl compounds such as -vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone, and one or more of these can be copolymerized with a styrene monomer.

Of the above styrene resins, styrene / acrylic copolymer resins having a molecular weight distribution consisting of a low molecular weight peak of 5,000 or less, preferably 3000 to 4000 and a high molecular weight peak of about 400,000 are preferred. By using this styrene / acrylic copolymer resin, the compatibility with the low molecular weight polyethylene wax is increased, and it is effective in preventing the offset phenomenon and in saving power during kneading in the toner manufacturing process.

A thermoplastic resin obtained by mixing the styrene resin with another resin can also be used as the resin component of the toner according to the present invention. Other resins that can be mixed with the styrene resin include vinyl naphthalene, vinyl halides such as vinyl chloride, vinyl bromide and vinyl fluoride, such as vinyl acetate, vinyl propionate, vinyl benzoate, butyric acid. Vinyl esters such as vinyl, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-chloro-ethyl acrylate, phenyl acrylate, α- Esters of α-methylene aliphatic monocarboxylic acids such as methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, methacrylonitrile, acrylamides such as vinyl methyl ether, vinyl isobutyl ether. Vinyl ethers such as vinyl ether and vinyl ethyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone, such as N
-Homopolymers obtained by polymerizing monomers such as N-vinyl compounds such as vinylpyrrole, N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidene, or copolymers prepared by combining two or more of these monomers. There are polymerized copolymers or non-vinyl type thermoplastic resins such as rosin-modified phenol formalin resin, oil-modified epoxy resin, polyurethane resin, cellulose resin and polyether resin.

When these resins are used in admixture with a styrenic resin, they should be present in an amount such that at least about 25% by weight styrene component is present, based on the total weight of the resulting resin. It is preferable to mix both. This is because the releasability of the toner to the fixing roller is closely related to the existing amount of the styrene component, and the releasability of the toner to the fixing roller tends to decrease as the styrene component decreases.

The toner according to the present invention contains a colorant capable of forming a visible image by a phenomenon. As the colorant, pigments or dyes are used, for example, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue keloride, phthalocyanine blue, malachite green oxa. Rate, lamp black, rose bengal and mixtures thereof are used. Among the above colorants, it is desirable to use carbon black having a particle size of 50 nm or less, preferably 20 to 30 nm. This improves the dispersibility of carbon black during melt-kneading in the toner manufacturing process and improves the image density.

[0016]

When the toner containing the low molecular weight polyethylene wax of the present invention is used, when the toner comes into contact with the heated fixing roller, the low molecular weight polyethylene wax in the toner is liquefied and released on the toner surface, Covering the surface of the fixing roller, the melted toner does not adhere to the surface of the fixing roller. When a specific styrene / acrylic copolymer resin is used as the resin component of the toner,
The compatibility with the low molecular weight polyethylene wax is increased. Furthermore, when carbon black having a specific particle diameter is used as the colorant of the toner, the dispersibility of the carbon black during melt-kneading in the toner manufacturing process is improved.

[0017]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Raw materials for the toners of Examples and Comparative Examples are shown below. Styrene / butyl acrylate copolymer 100 parts by weight Carbon black MA-100 (manufactured by Mitsubishi Kasei) 6 parts by weight Charge control agent Bonitoron P-51 (manufactured by Orient Chemical Industry Co., Ltd.) 2 parts by weight Polypropylene wax High wax NP-505 (Mitsui Petrochemical) 2 parts by weight Polyethylene wax (PE WAX) 1 part by weight

The above materials were mixed, melt-kneaded, pulverized and classified to form a toner, and externally added using silica R972 (manufactured by Nippon Aerosil Co., Ltd.) as a fluidizing agent. The average particle size of the obtained toner is 9.5 μm.
Met. An unfixed sample of this toner prepared by Sharp Corporation SD2060 was used with a nip width of 9 mm and a peripheral speed of 400.
A fixing test was performed using an SD2060 external fixing tester (manufactured by Sharp) adjusted to mm / sec. (Test paper cat letter)

The methods for measuring the physical properties of the toners obtained in each of the examples and comparative examples and the respective evaluation criteria are shown below. 1. Molecular weight The molecular weight was measured by the GPC method.

2. Non-offset region The non-offset region (° C.) refers to a temperature region in which the offset phenomenon does not occur, and the wider it is, the better. The offset means that toner adheres to the fixing roller. The evaluation criteria are as follows. ◯: The width of the offset area is 95 ° C or more and the lower limit value is 1
40 ° C. or less Δ: Lower limit value of offset region is 140 ° C. or less ×: Lower limit value of offset region> 140 ° C.

3. 150 ° C. minimum residual rate 150 ° C. minimum residual rate (%) is the value determined by the following formula after scraping a sample prepared by an external fixing tester at 150 ° C. with a cloth loaded with 1 kg. It is calculated and obtained by the method of least squares.

[Equation 1] The evaluation criteria are as follows. ○: 70% or more ×: less than 70%

4. Black Solid Remaining Ratio Black solid means the density when the image density (ID) is 1.3, and the image density was measured by a Macbeth densitometer.
The black solid residual ratio (%) is the black solid residual ratio at ID = 1. 3, and is an index showing the fixing property of the toner. The evaluation criteria are as follows. A: 95% or more B: 90% or more, less than 95% X: less than 90%

5. Spent Rate The spent rate (%) means the amount of toner components adhering to the carrier per fixed amount after 2000 times of copying, and the higher this is, the more the adhering components are and the lower the function of the carrier is. . The evaluation criteria are as follows. ○: 0.05% or less ×: Exceeded 0.05%

6. Melt viscosity Melt viscosity (cp) refers to the viscosity at the time of melting at a certain temperature. The melt viscosity was measured with Rheomat 115A (manufactured by Contrabass).

7. Softening point The softening point (° C.) refers to the temperature at which the toner softens, and was measured using a flow tester (manufactured by Shimadzu Corporation).

8. Filming Filming means that the toner adheres to the drum and the photosensitive member in the adhered portion does not function. Evaluation is SD2
Visual inspection was performed in the 060 live-action test. The evaluation criteria are as follows. ◯: The constituent components of the toner are not visually confirmed on the surface of the photoconductor. Δ: The constituent components of the toner are visually confirmed on the surface of the photoconductor.

9. Torque Torque is measured by the current value of the kneading machine motor during melt kneading, and the evaluation criteria are as follows. ◯: 160 A or less Δ: 160 A or more and less than 200 A ×: 200 A or more

10. Yield value The yield value is the amount of toner consumed during copying. In this embodiment, an original having a solid black ratio of 6% is used and the number of grams of toner consumed (g / 5k) when 5000 copies are taken.
Represents the yield value. The evaluation criteria are as follows. ◯: 160 g / 5 k or less Δ: 160 g / 5 k or more, 170 g / 5 k or less x: 170 g / 5 k or more

The results of evaluating the toners obtained in Examples 1 and 2 and Comparative Examples 1 to 5 are shown in Table 1 below.

[0030]

[Table 1]

As is clear from the results in Table 1, the toners of Examples 1 and 2 according to the present invention, that is, the weight average molecular weight Mw is Mw <1000, and the weight average molecular weight Mw is
A toner containing a low-molecular-weight polyethylene wax having a ratio of Mw / Mn of Mw / Mn ≦ 1.5 is excellent in prevention of an offset phenomenon in a low temperature region and in fixing property (fixing strength) of the toner. There was found.

The evaluation results of the toners obtained in Examples 3 to 6 and Comparative Example 6 are shown in Table 2 below.

[0033]

[Table 2]

As is clear from the results in Table 2, the toners of Examples 3 to 6 according to the present invention are excellent in the prevention of the offset phenomenon in the low temperature region and in the fixing property (fixing strength) of the toner. found. In addition, when the weight average molecular weight of the low molecular weight polyethylene wax was in the range of 600 to 800, the above effect was particularly remarkable.

The evaluation results of the toners obtained in Examples 7 to 10 and Comparative Examples 7 to 8 are shown in Table 3 below. The weight average molecular weight Mw of the low molecular weight polyethylene waxes used in Examples 7 to 10 and Comparative Examples 7 to 8 was Mw <1000.

[0036]

[Table 3]

As is clear from the results shown in Table 3, the toners of Examples 7 to 10 according to the present invention, that is, the toners containing the low molecular weight polyethylene wax having a melt viscosity at 130 ° C. of 50 cp or less, are in the low temperature range. It was proved that the prevention of the offset phenomenon and the fixing property (fixing strength) of the toner were excellent. The melt viscosity of the low molecular weight polyethylene wax is 7 to 20 cp / 130 ° C.
In the case of the range, the above effect was particularly remarkable.

The results of evaluating the toners obtained in Examples 11 to 14 and Comparative Examples 9 to 10 are shown in Table 4 below. The weight average molecular weight Mw of the low molecular weight polyethylene waxes used in Examples 11 to 14 and Comparative Examples 9 to 10 was Mw <1.
It was 000.

[0039]

[Table 4]

As is clear from the results shown in Table 4, the toners of Examples 11 to 14 according to the present invention, that is, the toners containing the low molecular weight polyethylene wax having the softening point of 120 ° C. or less, are offset phenomenon in the low temperature region. It has been found that the toner is excellent in prevention of occurrence of toner and the fixing property (fixing strength) of the toner. In addition, especially when the softening point of the low molecular weight polyethylene wax is in the range of 90 to 110 ° C.,
The effect was remarkable.

Next, the ID measured by the aforementioned Macbeth densitometer and the amount of toner adhered to each ID (mg / c
The relationship of m ² ) is shown in FIG. Also, toner consumption (g / 5k) in the aging test using an original with a black solid ratio of 6%
The transition of is shown in FIG. The PE of the toner of Example 15
The weight average molecular weight Mw of WAX was 957, and the ratio Mw / Mn of Mw and the number average molecular weight Mn was 1.28. On the other hand, the weight average molecular weight Mw of PE WAX of the comparative example 11 toner was 2420, and Mw and the number average molecular weight Mn.
And the ratio Mw / Mn was 3.96. However, the particle size of carbon black was 20 to 50 nm in both cases.

As is clear from FIG. 1, for example, ID =
It can be seen that when the toner of Example 15 according to the present invention is used to obtain 1.3, the toner adhesion amount is about 80 to 90% as compared with the toner of Comparative Example 11. Also in FIG. 2, the toner of Example 15 according to the present invention is the same as Comparative Example 11
It can be seen that the printing ability is higher than that of the above toner, that is, the hiding power of the toner is improved. Therefore, the toner according to the present invention requires less toner consumption,
It was also found to be effective in reducing copy costs.

The evaluation results of the toners obtained in Examples 16 to 19 and Comparative Example 12 are shown in Table 5 below. The weight average molecular weight Mw of the low molecular weight polyethylene waxes used in Examples 16 to 19 and Comparative Example 12 was Mw <1000.

[0044]

[Table 5]

As is clear from Table 5, the toners of Examples 16 to 19 according to the present invention, that is, styrene / acrylic type toners having a molecular weight distribution consisting of a low molecular peak of 5,000 or less and a high molecular peak of about 400,000. Copolymer resin (S
The toner containing t / Ac) prevents the occurrence of the offset phenomenon in the low temperature region and fixes the toner (fixing strength).
It was found that it is excellent in the above and that it is effective in reducing the torque during melt-kneading. When the low molecular peak of the styrene / acrylic copolymer resin was in the range of 3000 to 4000, the above effect was particularly remarkable.

Next, FIG. 3 shows the relationship between the ID and the toner adhesion amount when the particle size of carbon black is changed.
The changes in toner consumption are shown in each. The particle diameters of carbon black used in each of the examples and comparative examples are as follows. Example 20: 45 nm Example 21:30 nm Example 22: 22 nm Example 23: 15 nm Comparative example 13: 75 nm In addition, PE of the toner of Examples 20 to 23 and Comparative example 13 is used.
The weight average molecular weight Mw of WAX was 957, and the ratio Mw / Mn of Mw and the number average molecular weight Mn was 1.28.

From FIG. 3, Examples 20 to 23 according to the present invention are shown.
In the case of using the above toner, that is, the toner containing carbon black having a particle diameter of 50 nm or less, the hiding power of the toner, that is, the dispersion of carbon black is improved, and from FIG. 4, the hiding power is improved. As a result, the transition of toner consumption is also reduced, and it has been found that it is effective in cost reduction. When the particle size of carbon black is in the range of 20 to 30 nm, the above effect was particularly remarkable.

[0048]

By using a low-molecular-weight polyethylene wax having a weight-average molecular weight Mw of Mw <1000 as a constituent of the toner of the present invention, the low-molecular-weight polyethylene wax contained in the toner when contacted with a heated fixing roller is used. The molecular weight polyethylene wax is liquefied and released on the surface of the toner to cover the surface of the fixing roller, and the melted toner does not adhere to the surface of the fixing roller. As a result, it is possible to prevent the occurrence of the offset phenomenon in the low temperature region and improve the fixability of the toner. Further, by setting the ratio of the weight average molecular weight Mw and the number average molecular weight Mn of the low molecular weight polyethylene wax to Mw / Mn ≦ 1.5, the above effect becomes more remarkable.

By setting the melt viscosity of the low molecular weight polyethylene wax to 50 cp / 130 ° C. or less, the surface of the fixing roller is more uniformly covered with the melted low molecular weight polyethylene wax, and the occurrence of the offset phenomenon is effectively prevented. It Further, by setting the softening point of the low molecular weight polyethylene wax to 120 ° C. or lower, the fusion temperature can be lowered.

5000 as the resin component of the toner of the present invention
By using a styrene / acrylic copolymer resin having a molecular weight distribution consisting of the following low molecular weight peak and a high molecular weight peak of about 400,000, the compatibility with the low molecular weight polyethylene wax becomes large and the offset phenomenon occurs. Can be prevented, and further power saving can be achieved during kneading in the toner manufacturing process.

By using carbon black having a particle size of 50 nm or less as the colorant component of the toner of the present invention, the dispersibility of carbon black during melt-kneading in the toner manufacturing process is improved, and the image density is improved. To be Further, the copy cost can be reduced by reducing the toner consumption amount.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between ID and toner adhesion amount when toners containing polyethylene waxes having different molecular weights are used.

FIG. 2 is a characteristic diagram showing changes in toner consumption when toners containing polyethylene waxes having different molecular weights are used.

FIG. 3 is a characteristic diagram showing the relationship between ID and toner adhesion amount when toners containing carbon black having different particle diameters are used.

FIG. 4 is a characteristic diagram showing a transition of toner consumption when toners containing carbon black having different particle diameters are used.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 9/08 325 361 (72) Inventor Koji Shinkawa 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Mihoko Okada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) In-house Yoshiaki Akazawa, 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture (72) Inventor Masaaki Otsuki 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture

Claims (6)

[Claims] 1. An electrophotographic developer containing a colorant, a styrene resin and a low molecular weight polyethylene wax, wherein the weight average molecular weight Mw of the low molecular weight polyethylene wax is Mw <1000. Developer. 2. The electrophotographic developer according to claim 1, wherein the ratio of the weight average molecular weight Mw of the low molecular weight polyethylene wax to the number average molecular weight Mn is Mw / Mn ≦ 1.5. 3. The electrophotographic developer according to claim 1, wherein the low-molecular-weight polyethylene wax has a melt viscosity of 50 cp / 130 ° C. or less. 4. The electrophotographic developer according to claim 1, wherein the softening point of the low molecular weight polyethylene wax is 120 ° C. or lower. 5. The styrene resin is a styrene / acrylic copolymer resin having a molecular weight distribution consisting of a low molecular weight peak of 5000 or less and a high molecular weight peak of about 400,000. The described electrophotographic developer. 6. The electrophotographic developer according to claim 1, wherein the colorant contains carbon black having a particle size of 50 nm or less.