JP2595239B2 - Electrophotographic developing toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a toner for electrophotographic development used in electrophotography employing a pressure fixing heat fixing method.

[Prior Art] In a color image, among the elements of the image quality, the gloss of the image greatly affects the image quality.

When the image has no gloss, that is, when the surface reflected light is diffusely reflected, in order to simultaneously visually recognize a part of the internal reflected light having a predetermined color and a part of the surface diffuse reflected light,
The perceived color density is reduced. Therefore, in this case, the image looks pale and the image lacks power.

Conventional full-color copying machines use a low-temperature softening type toner and a silicone roller applied with silicone oil. However, the life of a silicone roller with improved releasability is short. For this reason, fluororesin roller fixing is desired, but fluororesin roller fixing is inferior in releasability as compared with silicone roller fixing as a whole system, and low-temperature softening toner tends to cause hot offset. ,
There was virtually no constant temperature range.

[Purpose] As a result of earnest research on the gloss of this image,
An object of the present invention is to solve the above-described problems of the related art by providing an electrophotographic toner that can be fixed by pressing a heating member having a surface made of a fluororesin into contact with a toner-carrying surface by pressing and fixing the toner, and exhibiting excellent gloss. I have.

[Structure] As described in the claims, the structure of the present invention for achieving the above object is a toner for electrophotographic development, which is fixed by a pressure bonding heating method (heat roll fixing method) using a fluorine resin and a fixing roller. , The dynamic viscoelastic properties of the toner are such that the storage elastic modulus [G ′ (ω)] at a frequency of 100 rad / sec.
When the value is 1 × 10 ⁵ (dyn / cm ² )
Are toners for electrophotographic development in the range of 1.7 ≦ tan δ ≦ 3.

The mechanism by which a glossy image can be formed by the toner of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the unfixed toner 1 on the support 2 enters a fixing device and is fixed through the following steps.

(1) As shown in FIG. 2, the unfixed toner contacts the heating roller 3, and the toner changes from a solid state to a glass transition state to a rubber state by heat conduction.

(2) When the toner is in a rubber state, plastic deformation starts due to the pressure between the two rollers 3 and 4, and the toner particles are united and the toner penetrates into the support 2. The surface of the toner 1 is in close contact with the surface of the heating roller 3, and the surface of the toner is melted to form a surface molten layer 5, which becomes smooth.

(3) It is released from the pressure between the rollers 3 and 4, released from the heating roller, and discharged from the fixing device. The toner 1 and the support 2 are cooled, solidified and adhered.

As a mechanism for generating gloss during fixing, in (1), the toner behaves as a viscoelastic body. In (2), the toner is deformed by the pressure, and its surface becomes smooth. The magnitude of the strain and the time to be applied are determined by the conditions of the fixing device, and are respectively a pressure and a nip time. In (3), the toner is released from the pressure, and a stress acts on the toner to restore the toner to its original state. Those close to the elastic body have a small rate of time reduction of stress, and therefore have a large rate of recovery to the original state as shown in FIG. The surface of the toner having such characteristics becomes uneven. On the other hand, those that are close to viscous materials have a large rate of time reduction of stress, and therefore have a small rate of recovery to the original state. Since the toner having such characteristics maintains a smooth state as shown in FIG. 3, a glossy image is obtained. Useful models are conceivable.

According to such a model, the dynamic viscoelasticity of the toner is an important factor. Among dynamic viscoelasticity, tan δ is a ratio of a storage elastic modulus [G ′ (ω)] indicating a spring property (elasticity) and a loss elastic modulus [G ″ (ω)] indicating a dashpot property (viscosity). (G '/ G "), and as a result of earnestly studying the glossiness of the image, the above-described structure of the invention has been reached.

That is, when tan δ is in the range of 1.70 ≦ tan δt ≦ 3.00, in fixing by the pressure bonding heating method, there is sufficient release property,
There is an advantage that a usable fixing range is obtained, and the image surface becomes smooth due to plastic deformation, and a glossy image is obtained.

However, when tan δ <1.70, there is sufficient releasability and a wide fixing range can be obtained. However, since the elasticity of the toner is high, the image surface is not smooth and a glossy image cannot be obtained.

On the other hand, if tan> 3.00, there is no sufficient releasability, and an offset phenomenon occurs with respect to the Teflon heating roller.

By the way, to explain the measurement of the viscoelastic properties, an instrument for measuring the rheological properties is generally called a rheometer. The rheometer used in the present invention is a Rheometrics Dynamics Spectrometer RDS-7700 manufactured by RHEOMETRICS.INC (USA).

The condition was that the frequency was fixed at ω = 100 rad / sec, and the distortion rate was automatic. In this state, the temperature was raised and the temperature dependency was measured. From this result, the tangent loss tan δ when the storage elastic modulus G ′ = 10 ⁵ dyn / cm ² was measured. The effective fixing time of the hot roll fixing device is usually about 1 × 10 ^{-2 to} 5 × 10 ^-2 seconds, and the rheological properties of the toner were measured at the corresponding angular frequency ω = 100 rad / sec.

The kind of the binder resin used in the present invention may be any resin generally used as a toner resin. However, since the viscoelastic properties of the binder resin strongly affect the viscoelastic properties of the toner, the viscoelasticity of the resin itself should be considered.

As the binder resin used in the present invention, for example, polystyrene, poly-P-chlorostyrene, a homopolymer of styrene such as polyvinyltoluene and a substituted product thereof, styrene-P
-Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-
Styrene-based copolymers such as vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, poly (vinyl chloride), Polyvinyl acetate, polyethylene, polypropylene, silicone resin, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin modified rosin, terpene resin, phenol resin, xylene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum Resin, chlorinated paraffin, paraffin wax or the like is used alone or as a mixture. Among such resins, styrene-based resins, polyesters, epoxy resins, and the like, which are excellent in transparency in terms of full-color image formation, are particularly preferable. As described above, since the viscoelasticity of the resin strongly affects the viscoelasticity of the toner itself, it is considered that it is better to select the resin itself from the range of 1.7 ≦ tanδ ≦ 3 shown in the claims of the present invention. Also, generally this
Resins showing the range of tan δ are the weight average molecular weight of the resin (▲
▼) and number average molecular weight (▲ ▼) ratio ▲ ▼ / ▲
▼ seems to be relatively small and ▲ ▼ / ▲ ▼ ≦ 10 seems to be many.

Benzidine yellow (for example, CI Pigment Yellow 12), monoazo dye (for example, CI Solvent Yellow 16), and nitrophenylamine sulfonamide (CI Disperse Yellow 33) can be used as a colorant for the electrophotographic toner of the present invention. And magenta is quinacridone (for example, CI Pigment Red 12
2), anthraquinone dyes and diazo dyes (CI Solvent Red 19). Examples of cyan include copper phthalocyanine (CI Pigment Blue 15) and indanthrene blue, and examples of black include carbon black and nigrosine dye. Of course, if it is not intended to apply the toner of the present invention to full-color electrophotography, it is natural that many other known dyes and pigments can be used.

The toner of the present invention can be used as a two-component developer that is mixed with a carrier to form a developer, or as a one-component developer by known methods. When used as a two-component developer, any known carrier can be used, and examples thereof include magnetic powders such as iron powder, glass beads, and those whose surfaces are treated with a resin.

As a means for fixing the electrophotographic toner of the present invention on a recording material, a generally known pressure heating fixing method (heating roll fixing method) may be used. The heat roller for pressing the toner together with the (rigid) recording material is desirably a rigid body because it is due to the plastic deformation of the toner layer in the pressure heating step. In other words, the heat roller that forms the nip width with the recording material and the toner layer between the pressure roller and the toner layer is glossy because the rigid roller that becomes non-compliant contact fixing applies pressure from the direction perpendicular to the recording material surface Is easy to obtain.

The fixing roller (heat roller) of the pressure heat fixing device used in the present invention is aluminum, stainless steel,
A heat-resistant release resin layer such as a tetrafluoroethylene resin is provided as a thin layer having a thickness of about 20 to 100 μm on the outer peripheral surface of a metal hollow roller core made of iron, copper or the like. Note that the outer peripheral surface of the fixing roller is in contact with the toner layer and is smooth to give gloss.

The pressure roller is pressed against the fixing roller at least at the time of fixing by a known means, and forms a nip width,
An elastic layer made of silicon rubber, fluorine rubber, fluorosilicone rubber or the like is provided relatively thick on the outer peripheral surface of a metal roller core. The heating method of the fixing roller and, if necessary, the heating method of the pressure roller may be a known method. Further, if necessary, a liquid having excellent releasability, such as silicone oil, can be applied to the fixing roller to improve the releasability of the roller.

Hereinafter, the embodiment will be described in detail. The amounts (parts) of the components described in the examples are all parts by weight.

Example 1 Composition of Toner Resin: Styrene-n-butyl methacrylate copolymer (▲ = 33.000, ▼ = 9.200, ▼ / ▲ = 3.6) 100
Part Colorant: Copper phthalocyanine blue (CI Pigment Blue 15) 5 parts ^* Viscoelasticity of toner tan δ = 2.60 (G '= 10 ^-5 dyn / cm ² at ω = 100 rad / sec) Heat the above mixture with a three-roll mill After kneading and allowing to cool,
The resultant was coarsely pulverized by a cutting mill and further finely pulverized by an ultrasonic jet mill pulverizer, and classified by a zigzag classifier to obtain a toner having an average particle diameter of 11 μm.

5 parts of the toner and a spherical ferrite carrier (average particle diameter)
100 μm, resin coating) were mixed to prepare a developer.

Similarly, the colorant was changed to 5 parts of benzidine yellow (CI Pigment Yellow 12) to prepare a yellow toner, and similarly, the colorant was changed to 5 parts of quinacridone (CI Pigment Red 122) to prepare a magenta toner.

The viscoelasticity was tan δ = 2.50 for the yellow toner and tan δ = 2.55 for the magenta toner. A yellow toner and a magenta toner were prepared as developers similarly to the cyan toner.

Ricoh Richo Colo with modified fixing unit for copy test
r 5000 (hereinafter referred to as RC-5000) was used. The fixing roller of the RC-5000 breaker uses a Teflon resin (Dupont, polyfluoroethylene) on the outer peripheral surface of an aluminum hollow cored bar.
A 50μm thick (φ50m / m) coated roller with a 5mm thick silicone rubber (KE-1300RTV made by Shin-Etsu Chemical) on the outer peripheral surface of an aluminum hollow cored bar (φ50m / m)
m). A silicone oil (KF-96 manufactured by Shin-Etsu Chemical Co., Ltd.) was slightly applied to the surface of the heating roller as a releasing aid. Fixing conditions: linear speed 105mm / sec, nip
The width (the width of the contact between the fixing roller and the pressure roller) was 8 mm, and the pressure was 8 kgf / cm ² .

A copy test was performed on the YMC three-color developer using the RC-5000, and a full-color image was formed by superimposing the three colors. The obtained image had a glossiness of about 45% in the shadow area and about 25 to 30% in the halftone area. It was not a glossy finish that is often seen in fixing with a silicon roller, but a finish in which the toner layer thickness similar to printing was not felt. The image was good in color development and good in quality.

In addition, a single color image of each color of YMC was formed in the single color mode of RC-5000. Maximum image density of these images (Max.ID)
And glossiness with a variable-angle gloss meter [JIS Z-8741 (1983) Method 3
Gs (60 °)]. (See Table 1.) As a result, a satisfactory monochromatic copy having sufficient gloss and high maximum image density was obtained.

Hereinafter, in Examples 2 to 4, toners were produced under the same conditions as in Example 1 except for the composition of the toner described therein, and images were produced under the same conditions.

Example 2 Composition of Toner Resin: Styrene-ethyl methacrylate copolymer (▲
▼ = 53.000, ▲ ▼ = 18.000, ▲ ▼ / ▲
▼ = 2.9) 100 parts Colorant; carbon black 8 parts Example 3 Composition of Toner Resin: Styrene-maleic acid ester copolymer (▲
▼ = 59.000, ▲ ▼ = 27.000, ▲ ▼ / ▲ ▼
= 2.2) 100 parts Coloring agent: Copper phthalocyanine 5 parts Example 4 Composition of Toner Resin: Polyester (▲ = 21.000, ▲ ▼ =
4.000, ▲ ▼ / ▲ ▼ = 5.3) 100 parts Colorant: CI Pigment Red 87 5 parts Comparative Example 1 Composition of Toner Resin: Styrene-2-ethylhexyl methacrylate copolymer (▲ = 180.000n, ▲ = 4.200, ▲
▼ / ▲ ▼ = 42.9) 100 parts Colorant: Copper phthalocyanine blue 5 parts ^* Similarly yellow toner colorant: Benzidine yellow 5 parts Magenta toner colorant: Quinacridone 5 parts Viscoelastic cyan toner tanδ = 1.12 Magenta toner tanδ = 1.10 yellow Toner tan δ = 1.10 A three-color YMC developer was obtained from the above mixture in the same manner as in Example 1. In the single color mode copy test, none of the YMC images was glossy and lacked vividness. In the full color mode copy test, a gloss level of about 7% was obtained in the shadow area and about 5% in the halftone area of the full color image, giving a very poor impression. The color developability of each color was poor, and the image was not visible.

Hereinafter, in Comparative Examples 2 to 4, toners were produced under the same conditions as in Comparative Example 1 except for the composition of the toner described therein, and images were produced under the same conditions.

Comparative Example 2 Composition of Toner Resin: Styrene-n-butyl acrylate copolymer (▲ = 220.000, ▼ = 10.000, ▼ /
▲ ▼ = 22.0) 100 parts Colorant: carbon black 8 parts Comparative Example 3 Toner Composition Resin: Styrene-methyl methacrylate copolymer (▲ ▼ = 120.000, ▲ = 20.000, ▲ /
▲ ▼ = 6.0) 100 parts Colorant: Copper phthalocyanine 5 parts Comparative Example 4 Composition of Toner Resin: Polyester (▲ ▼ = 43,000, ▲ ▼ =
3,100, ▲ ▼ / ▲ ▼ = 13.9) 100 parts Coloring agent: 5 parts of CI Pigment Red 87 Test Results The test results of the toners of the above Examples and Comparative Examples are shown in Table 1 below.

Comparative Example 5 Composition of Toner Resin: Polyester (▲ ▼ = 12,000, ▲ ▼ =
3,200, ▲ ▼ / ▲ ▼ = 3.8) 100 parts Colorant: copper phthalocyanine 5 parts ^* Cyan toner → tanδ = 3.12 The same mixture as in Example 1 was used to obtain a cyan developer. When a copying test was performed on this developer, an offset phenomenon occurred from a low temperature, and an image could not be obtained.

[Effects] As described above, the toner of the present invention has high glossiness, and a full-color image using the toner can provide a high-quality image having good glossiness and vivid coloration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state where the toner of the present invention is not fixed, FIG. 2 is a schematic diagram showing a fixing process, FIG. 3 is a schematic diagram showing a state after fixing, and FIG. 4 is a toner of a comparative example. FIG. 3 is a schematic view showing a state after fixing. 1 ... toner, 2 ... support, 3 ... heating roller, 4
…… Pressing roller, 5… Surface melting layer.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihisa Okamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-59-214864 (JP, A)

Claims (1)

(57) [Claims] 1. A toner for electrophotographic development in which a heating member having a surface made of a fluororesin is brought into contact with and pressed against a toner carrying surface and fixed by the electrophotographic developing toner.
The storage modulus [G ′ (ω)] of 100 rad / sec is 1 × 10 ⁵ (dyn
/ cm ² ), the mechanical cutting loss (tanδ) is 1.7 ≦ tanδ
A toner for electrophotographic development, which is in the range of ≦ 3.