JPH0364766A - Toner for developing electrostatic latent image - Google Patents

Abstract

PURPOSE:To improve fixability at low temp., anti-offsetting property and blocking resistance by rendering a specified range of modulus of dynamic shearing storage elasticity to a binding resin at each of specified temps. CONSTITUTION:The binding resin has a 1X10<5>-5X10<6>dyn/cm<2> range of modulus G' of dynamic shearing storage elasticity at 1Hz frequency at a temp. T1 expressed by equation I and 1X10<3>-5X10<4>dyn/cm<2> range to the resin at a temp. T2 expressed by equation II. A styrene-(meth)acrylate copolymer such as a styrene-butyl acrylate copolymer or polyester resin is preferably used as the binding resin. In the equations I, II, TR is the temp. ( deg.C) of a hot roll and TA is atmospheric temp. ( deg.C). Fixability at low temp., anti-offsetting property and blocking resistance are improved.

Description

[Detailed description of the invention] Kei Usei□Gekki Kyouwata The present invention relates to a toner for developing electrostatic latent images.

Traditionally, in the distorted electrophotographic method, an electrostatic latent image is formed on a photoreceptor by various methods, and then this electrostatic latent image is developed using a developer containing toner. A generally known method is to develop the toner image, transfer the toner image thus obtained onto a support such as paper, and fix it using heat, light, or the like.

The above toner image can be fixed by heating and melting the toner using a heater or hot roll, and then fusing and solidifying the toner onto the support, or by softening or dissolving the binder resin of the 1-toner with an organic solvent, and fixing the toner onto the support. A method of fixing the toner on a support, a method of fixing the toner on a support by applying pressure, etc. are known. Among these, the contact heat fixing method, represented by the heat roll fixing method, is superior to other methods in terms of high thermal efficiency, and in particular, it is capable of high-speed fixing.
Widely adopted.

However, in this contact heat fixing method, a part of the toner that came into contact with the heat roll during fixing adheres to the surface of the heat roll and is transferred again to the support during the next fixing process, resulting in a so-called offset phenomenon, which causes the fixed image to deteriorate. It may seriously impair the quality of the product.

Conventionally, therefore, materials such as polytetrafluoroethylene or silicone, which have excellent surface releasability, have been used for fusers, or silicone oil has been applied to the roll surface, but these measures have not been effective in copying. This increases the price of the copying machine or complicates the structure of the copying machine.

On the other hand, in order to solve the above-mentioned offset problem, it is also known to include, for example, a low molecular weight polyethylene wax or polyethylene wax in the toner and sufficiently melt the toner when heated. However, when wax is blended into toner as an anti-offset agent in this way, the cohesiveness of the toner increases, and due to the toner's electrification, it becomes difficult to perform smooth stirring, etc., resulting in a high-quality product. Unable to obtain a duplicate image.

Furthermore, various attempts to improve the binder resin of toner have been proposed. For example, in Japanese Patent Publication No. 51-23354,
Toners using crosslinked polymers as binder resins have been proposed. According to this method, offset resistance is improved, but when the degree of crosslinking of the binder resin is increased, the fixing temperature increases, resulting in poor fixing characteristics.

Generally, in order to improve the high-speed fixing properties of a toner, it is necessary to have excellent low-temperature fixing properties. For this purpose, it is necessary to lower the melting point of the binder resin, but when a binder resin with a low melting point is used in this way, the toner may block, causing storage problems.

As described above, to date, there has been no known toner that can be fixed at low temperatures and has excellent anti-offset and anti-blocking properties.

As a result of extensive research in order to solve the above-mentioned problems with conventional low-temperature fixing toners, the inventors of the present invention have discovered the use of a resin with specific viscoelastic behavior as a binder resin. The inventors discovered that it is possible to obtain a toner that can be fixed at low temperatures and has excellent anti-offset and anti-blocking properties, leading to the present invention.

The present invention aims to reduce the TJI amount by increasing the temperature of the hot roll ( ℃), T.A.
is the ambient temperature (℃), and the temperature T+ ('C) and Tt
When ('e) is defined by the following formula % formula %, when the binder resin is at temperature T, I
X l O'dyn/cm" ~ 5 X 10"dy
has a dynamic shear storage modulus G' (frequency IHz) in the range n/c- and at temperature Tt, I
103 dyn/cab” ~ 5 X 10' dyn/c
Dynamic shear storage modulus G in the range of m”.

(Frequency 1) 1z).

In the present invention, the binder resin includes any resin conventionally used in toners, such as styrene, O
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-chlorostyrene, vinyl acetate, vinyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, isobutyl acrylate, n-acrylate Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate , isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate, diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, acrylic acid One or more (co) radically polymerizable monomers such as glycidyl, glycidyl methacrylate, acrylic acid, methacrylic acid, 2-vinylpyridine, 4-vinylpyridine, etc.
Polymers may be mentioned. Moreover, polyester resin is also suitably used.

In particular, in the present invention, styrene-(meth)acrylic acid copolymers, such as styrene-butyl acrylate copolymers, and polyester resins are preferably used.

In the toner for developing electrostatic latent images according to the present invention, the above-mentioned binder resin has temperatures TI ('c) and 'r, where TI is the hot roll temperature (°C) and 'ra is the ambient temperature (°C).
(°C) is defined by the following formula % formula %, when the binder resin is at temperature TI, I
X 10'dyn/c+s"~5 X 10'dy
has a dynamic shear storage modulus G' (frequency IHz) in the range of "n/cm" and at temperature T2, I
10 dyn/cm"~5 x 10' dyn/c
- dynamic shear storage modulus G in the range.

(frequency IHz).

The fixability of toner using a heated roll is closely related to the melt viscoelasticity of the thermoplastic resin that is the binder resin, and the
When the dynamic shear storage modulus G'' (frequency IHz) at is smaller than I x 10 'dyn/cm'',
It is susceptible to thermal deformation at low temperatures, causing the toner to aggregate or lose fluidity during storage. On the other hand, the dynamic shear storage modulus G' (frequency IH2) at temperature T1 is 5
When it is larger than 10 'dyn/cm', a large amount of energy is required to fix the toner, and in the actual machine,
A heat roll with a high set temperature and a fixing device with a wide nip width are required, which inevitably causes cold offset at low temperatures.

On the other hand, when the dynamic shear storage modulus G' (frequency IHz) at temperature T2 is smaller than I x 103 dyn/c+*'', the toner obtains viscoelastic properties sufficient to overcome the adhesion with the hot roll. On the other hand, if the dynamic shear storage modulus G' (frequency IHz) at temperature T2 is 5 x 10'd
yn/cm", a large amount of energy is required to fix the toner, and as mentioned above, in nine actual machines, a heat roll with a high temperature setting and a fixing device with a wide nip width are required, and the cold offset occurs at low temperatures.

In the toner for developing electrostatic latent images according to the present invention, conventionally,
In the production of toner, any powder or granular dyes and pigments used as colorants and/or charge control agents may be contained. These include metal-containing dyes and pigments and organic acid metal salts, and specifically Examples include, in addition to carbon black, organic pigments such as phthalocyanine pigments, nigrosine dyes including dyes of the following formula, (wherein, X3 represents a cation species), and (X- is Electron-donating dyes such as nigrosine dyes represented by (in the formula, X represents an anion species)
Examples include electron-accepting dyes such as metal complex salts of monoazo dyes shown in

Further, the toner may contain a low molecular weight polyolefin wax as an anti-offset agent. As such a low molecular weight polyolefin wax, for example, polyethylene wax or polypropylene wax is suitably used.

The toner according to the present invention can be obtained by kneading the binder resin as described above together with the dye/pigment and anti-offset agent as required, and pulverizing the mixture to a desired particle size. Further, according to the present invention, the obtained toner particles may be surface-treated with colloidal silica or the like.

When the toner according to the present invention is used in a two-component development system, a substance known as a carrier, which is well known in the electrostatic electrophotographic technical field, is added to the toner and used as a two-component developer. In this two-component developer, the amount of toner blended is in the range of 2 to 20% by weight, preferably 5 to 10% by weight. Examples of carriers include iron powder,
Ferrite powder, magnetite powder, powder made of a composite of resin and magnetic material, etc. are used. Furthermore, a so-called coach carrier can also be used. However, it is not limited to these.

As described above, since the toner according to the present invention contains a binder resin having a predetermined viscoelastic behavior, it not only has excellent low-temperature fixing properties but also excellent anti-offset properties and anti-blocking properties. .

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Styrene-butyl acrylate copolymer (Mw=1.9X
10′, Mn=5.5×103) 100 parts by weight,
Low molecular weight polypropylene as anti-offset agent (
Viscole 550 P, manufactured by Sanyo Chemical Industry Co., Ltd.) 3 parts by weight,
Carbon black (Mitsubishi Chemical Carbon Black M)
A-8) 5 parts by weight and a monoazo chromium dye as a charge control agent (Spiron Black TRH manufactured by Hodogaya Chemical Industry ■)
) 2 parts by weight were mixed and melt-kneaded in a twin-screw extruder,
Grind with a jet grinder. Next, the particles were classified using an air classifier to prepare toner having a particle size of 5 to 20 μm.

This toner is 100! 0.3 parts by weight of Kay # fine powder (Aerosil R-972 manufactured by Nippon Aerosil ■) is mixed with the amount,
A developer was prepared by mixing this with a carrier (EFV250 manufactured by Nippon Tetsuko) so that the toner concentration was 6% by weight.

This developer was applied to a commercially available plain paper copying machine (Sanyo Electric Co., Ltd. 5FT-
11022) and 1oo at ambient temperature (TA)
Continuous copying of 00 sheets was performed and the images were evaluated.

In the above copying machine, the heat roll temperature (Ti) is 175~
185°C, and Go at the temperature T of the styrene-butyl acrylate copolymer at this time is 5.9
10'dyn/ca+"~1.2 x 10'dy
n/cm” and Go at temperature Tg is 3.5
10'dyn/cm" ~ 5.2 x 10'dyn
/c-.

The fixing strength was measured at a portion where the reflection density of the copied image fixed on the surface of the transfer paper was 1.4. As for the fixing strength, the load of cotton cloth is 250 g/an! 20 on the image
It was rubbed back and forth and evaluated based on the rate of change in concentration. Also,
Regarding offset resistance, the state of toner adhesion to the fixing roller was observed. Storage stability was evaluated based on the presence or absence of agglomeration of the toner after the toner was left at a constant temperature of 50° C. for 24 hours.

The melt viscoelasticity of the binder resin was measured using a Dynamometer Analyzer Model RDA-700 (manufactured by Rheometrics) by mounting the sample on a parallel flat plate with a diameter of 25 m and a gap length of 2111 mm. The measurement conditions are each frequency I Hz.
s The temperature variable range was 60 to 250°C. By applying a sinusoidal strain at one end of the cell and detecting the stress generated at the other end, the dynamic shear storage elastic modulus Go and dynamic shear loss elastic modulus G'' in the molten state can be determined.

The results are shown in Table 1.

Thereafter, toners were prepared in the same manner, and fixing strength, offset properties, storage stability, and image gradation were examined in the same manner.

Example 2 Polyester resin (Mw = 1.7 x 10',
Mn=0.6X10', gel fraction 43%) 100 parts by weight, 3 parts by weight of the same low molecular weight polypropylene as in Example 1, 5 parts by weight of carbon black, and 2 parts by weight of the same monoazo chromium dye as in Example 1. , in the same manner as in Example 1,
A toner having a particle size of 5 to 20 μm was prepared, and a fine silicic acid powder was mixed with this toner, and further mixed with a carrier to prepare a developer.

Go of the above polyester resin at temperature T is 1.8
X 10'dyn/cm" ~ 2.7 X 10'
dyn/cm" and Go at temperature T! is 5.2 x 10"dyn/cm" 1.7 x 10
'dyn/c-.

Comparative Example 1 Styrene-butyl acrylate copolymer (Mw=1, lX
10', Mn-0,4X 10') 100 parts by weight,
A toner having a particle size of 5 to 20 μm was prepared in the same manner as in Example 1 using 3 parts by weight of the same low molecular weight polypropylene as in Example 1, 5 parts by weight of carbon black, and 2 parts by weight of the same monoazo chromium dye as in Example 1. was prepared, silicic acid fine powder was mixed with this toner, and further mixed with a carrier to prepare a developer.

Go of the above styrene-butyl acrylate copolymer at temperature TI is 8.1 x 10'dyn/c1-1.
3X 10 'dyn/cs+' and temperature'
rz Go is 1.7 x 10” dyn/c
m” to 5.OX 10 “dyn/cm”.

In a copying test, this developer caused an offset phenomenon at low temperatures, making it impossible to obtain a sufficient image, and regarding storage stability, the occurrence of aggregates was observed.

Comparative Example 2 Styrene-butyl acrylate copolymer (Mw=2.87
Using 100 parts by weight of X10', Mn-1,0xlO'), 3 parts by weight of the same low molecular weight polypropylene as in Example 1, 5 parts by weight of carbon black, and 2 parts by weight of the same monoazo chromium dye as in Example 1, Example In the same manner as in Example 1, a toner having a particle size of 5 to 20 μm was prepared, and this toner was mixed with fine silicic acid powder, and further mixed with a carrier to prepare a developer.

Go of the above styrene-butyl acrylate copolymer at temperature T is 6.3 x 10'dyn/c1~1.
8X 10'dyn/c-, and G' at temperature T2 is 4. l X 10 'dyn/c+s'
~7. OX 10 'dyn/cm''.

This developer was only able to obtain a fixing strength of 78% in a copying test.

Comparative Example 3 Polyester resin (Mw = 1.2 x 10', M
n-0,3X10', gel fraction 13%>100 parts by weight,
A toner having a particle size of 5 to 20 μm was prepared in the same manner as in Example 1 using 3 parts by weight of low molecular weight polypropylene, 5 parts by weight of carbon black, and 2 parts by weight of the same monoazo chromium dye as in Example 1. was prepared, silicic acid fine powder was mixed with this toner, and further mixed with a carrier to prepare a developer.

G'' of the above polyester resin at temperature TI is 7.7
X 10 'dyn/cm" ~ 9. I X 10
'dyn/cm' and Go at temperature T2
is 0.9X10! dyn/c+w”~4.6 X 10
It was 'dyn/cab'.

In a copying test, this developer caused an offset phenomenon at low temperatures, making it impossible to obtain a sufficient image, and regarding storage stability, the occurrence of aggregates was observed.

Comparative Example 4 Polyester resin (Mw = 1.4 x 10', M
n-0,5X10', gel fraction 60%) 100 parts by weight,
A toner having a particle size of 5 to 20 μm was prepared in the same manner as in Example 1 using 3 parts by weight of low molecular weight polypropylene, 5 parts by weight of carbon black, and 2 parts by weight of the same monoazo chromium dye as in Example 1. was prepared, silicic acid fine powder was mixed with this toner, and further mixed with a carrier to prepare a developer.

Go of the above polyester resin at temperature TI is 9.3
X 10'dyn/cm"~2.OX 10'
dyn/c-, and Go at temperature Tt is 5
．． lX10'dyn/c+w" ~8.5 X 10
'dyn/c-.

This developer was only able to obtain a fixing strength of 83% in a copying test.

Claims (3)

[Claims] (1) In a toner for developing an electrostatic latent image in which a colorant, a charge control agent, and an anti-offset agent are optionally contained in a binder resin, T_R is the hot roll temperature (°C) and T_A
is the ambient temperature (℃), and the temperature T_1 (℃) and T_2
(℃) using the following formula T_1=9(T_R-T_A)/20+T_AT_2=
When defined by T_R, the binder resin has a temperature of 1 at temperature T_1.
×10^3dyn/cm^2~5×10^6dyn/c
dynamic shear storage modulus G′ in the range m^2 (frequency 1 Hz
) and at temperature T_2, 1×10^■
A toner for developing electrostatic latent images, characterized in that it has a dynamic shear storage modulus G' (frequency of 1 Hz) in the range of dyn/cm^2 to 5 x 10^4 dyn/cm^2. (2) The toner for developing electrostatic latent images according to claim 1, wherein the binder resin is a styrene-(meth)acrylate copolymer. (3) The toner for developing electrostatic latent images according to claim 1, wherein the binder resin is a polyester resin.