JP3119752B2 - Color toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color toner containing at least a binder resin and a colorant.

[0002]

2. Description of the Related Art In full-color copying, it is required to fix an image surface smoothly in order to satisfy the color reproducibility and glossiness of an image and the light transmittance of an OHP transfer material. From such a viewpoint, a fixing process using a heat roller using a soft roller that has a good follow-up property to unevenness due to color toner on the surface of an unfixed image is preferable.

On the other hand, color toners used for full-color copying are those which form a smooth surface easily by heating and pressing at the time of fixing, that is, those which have low elasticity at heating temperature. Needed.

However, color toners having low elasticity at the melting temperature tend to cause hot offset, and thus have a problem that the temperature range in which fixation is possible is narrowed.
Conventionally, a non-crosslinked polyester resin having a low molecular weight and a low softening point has been used as a binder resin as a resin capable of exhibiting good low-temperature fixability. However, this non-crosslinked polyester resin has many ester bonds (polar groups). ) In the main chain, the wettability and adhesion with the fixing roller are high, and the hot offset phenomenon is easily generated.

Further, a color toner having a low elasticity at a heating temperature has a low molecular weight of a binder resin constituting the color toner and does not have a sufficient strength.
For example, Japanese Patent Application Laid-Open No. 2-135559 discloses a low molecular weight
A technique using a styrene-acrylic resin having a low softening point as a binder resin is introduced, but such a resin is very brittle and has low hardness. Therefore, when a color toner using such a binder resin is used, the toner particles are crushed by stirring in the developing device, and fine powder is easily generated. Further, the external additive particles are easily buried on the surface of the toner particles having low hardness. And
The fine powder generated by the crushing and the toner particles in which the external additive particles are embedded have a large adhesive force to the carrier, so that the developability on the photoreceptor is reduced. Further, since the generated fine particles and the toner particles embedded with the external additive particles have a large adhesive force to the surface of the photoreceptor, the transferability is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances, and an object of the present invention is to provide:
It is an object of the present invention to provide a color toner capable of obtaining a fixed image having excellent surface smoothness. It is another object of the present invention to provide a color toner which does not cause hot offset in a fixing process using a heat roller. It is a further object of the present invention to provide a color toner having high strength that is not crushed even by stress caused by stirring in a developing device and high hardness that does not cause burying of an external additive.

[0007]

A color toner according to the present invention is a color toner containing at least a binder resin and a colorant, wherein the binder resin is a styrene- (meth) acrylate copolymer having an ion-crosslinking structure or an ionic copolymer. The color toner is composed of a (meth) acrylate (co) polymer having a crosslinked structure and has a storage elastic modulus at 90 ° C. of G ′ ₍₉₀₎ (dyne / cm ² ), 15
The storage elastic modulus at 0 ° C. is calculated as G ′ ₍₁₅₀₎ (dyne / cm
When defined as ² ), the following conditions are satisfied. <Conditions> 3 ≦ logG ′ ₍₉₀₎ ≦ 4.5 1 ≦ logG ′ ₍₁₅₀₎ ≦ 2.5

A copolymer having an ionic cross-linking structure comprises a styrene monomer of 0 to 49 mol%, a (meth) acrylate monomer of 50 to 99 mol%, and a half ester compound represented by the following formula (2). It is preferably obtained by reacting a polyvalent metal compound with a copolymer synthesized from 1 to 10 mol%.

[0009]

Embedded image Wherein R represents a hydrogen atom or a methyl group;
L represents a divalent linking group having an ester bond in the molecular chain and having 3 or more carbon atoms. ]

[0010]

[Action]

(1) Since the value of logG ' ₍₁₅₀₎ is 2.5 or less and the elasticity at the melting temperature is somewhat small, a smooth surface can be easily formed by heating and pressing at the time of fixing. (2) Since the value of logG ' ₍₉₀₎ is 4.5 or less and the elasticity at the heating temperature is somewhat small, a smooth surface can be formed even by fixing at a relatively low temperature. (3) Since the binder resin is composed of a styrene- (meth) acrylate copolymer or a (meth) acrylate (co) polymer, and the value of logG ' ₍₁₅₀₎ is 1 or more, wetting on the surface of the fixing roller. As a result, the occurrence of hot offset is suppressed, and the temperature range in which fixing can be performed is widened, as is clear from the results of Examples described later. (4) The binder resin is made of a (co) polymer having an ionic cross-linking structure, and the value of logG ' ₍₉₀₎ is 3
As described above, the brittleness of the (styrene-) acrylic (co) polymer is reduced, and the toner particles have excellent toughness at room temperature. Such toner particles are not crushed even by the stress caused by stirring in the developing device, and do not cause burying of the external additive. Therefore, as is clear from the results of Examples described later, excellent developing performance is obtained. And excellent transferability is stably expressed over a long period of time. In addition, since the ionic cross-linked structure is easily cut at the time of melting, it does not affect the properties at the melting temperature.

Hereinafter, the present invention will be described specifically. The binder resin constituting the color toner of the present invention is a styrene- (meth) acrylate copolymer having an ionic cross-linking structure or a (meth) acrylate (co) polymer having an ionic cross-linking structure.

<Monomer Component> Monomers used for obtaining such a (co) polymer having an ionic cross-linking structure include styrene-based monomers, (meth) acrylate-based monomers, and are represented by the above formula (2). Half-ester compounds (hereinafter, referred to as “specific half-ester compounds”) and the like can be mentioned.

As the styrene monomer, styrene,
Alkyl styrene such as methyl styrene and diethyl styrene, and halogenated styrene such as chlorostyrene can be used.

The (meth) acrylic acid for obtaining the (meth) acrylic acid ester monomer includes acrylic acid,
Methacrylic acid, α-ethylacrylic acid and the like can be used. Examples of alcohols for obtaining (meth) acrylate monomers include alkyl alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol. An alcohol having 1 to 4 carbon atoms such as a halogenated alkyl alcohol obtained by partially halogenating an alkyl alcohol can be preferably used.

<Specific half-ester compound> The specific half-ester compound is a compound contained in a monomer component for introducing an ionic crosslinked structure into the (co) polymer. This specific half-ester compound can be obtained by an esterification reaction of a derivative of a (meth) acrylic acid having a hydroxyl group with a dicarboxylic acid, and specifically, monomethacryloyloxyethyl succinate and monomethacryloyloxyethyl fumarate Esters and the like can be mentioned.

Although the introduction of the ionic cross-linking structure into the (co) polymer can be carried out by a usual (meth) acrylic acid monomer, the (co) polymer obtained by using a specific half-ester compound is The long side chain is preferred because the position of the carboxyl group moves away from the main chain and the steric hindrance in the chemical structure is less likely to occur. Thereby, ionic crosslinking between the (co) polymer and the polyvalent metal compound can be efficiently generated.

In order to introduce an ionic crosslinked structure, a polyvalent metal compound may be reacted with a (co) polymer obtained from a monomer component containing a specific half-ester compound,
An ionic crosslinked structure is formed by the coordination bond (ionic bond) between the carboxyl group and the metal ion. Examples of suitable polyvalent metal compounds include, for example, acetates and oxides of alkaline earth metals and zinc group metals.

The (co) polymer having the ionic cross-linked structure has reduced brittleness of the (styrene-) acrylic (co) polymer and exhibits toughness at room temperature. As a result, it is not crushed even by the stress caused by stirring in the developing device, and the external additive is not buried. In addition, since the ionic crosslinked structure is easily cut at the time of melting, it does not affect the properties at the melting temperature.

The content ratio of the above-mentioned monomer component used to obtain the (co) polymer having an ion-crosslinked structure introduced therein is as follows: "styrene-based monomer: (meth) acrylate-based monomer: specific half-ester compound" Is 0
The molar ratio is preferably 49:50 to 99: 1 to 10 (molar ratio). When the proportion of the (meth) acrylate-based monomer is at least 50 mol%, the obtained (co) polymer will have a large cohesive energy density and will be more excellent in toughness, and the toner particles will have a higher toughness. Generation of fine powder due to crushing and burying of external additives are reliably prevented. From the viewpoint of improving the toughness of the (co) polymer, it is preferable to use a methacrylate monomer rather than an acrylate monomer. When the proportion of the specific half-ester compound is less than 1 mol%, it is difficult to form an effective ionic crosslinked structure. On the other hand, if this ratio is 10
If it exceeds mol%, the side chains are crystallized to form domains, which is not preferred because the transparency required for the color toner is impaired. That is, the transmitted light is scattered, which is disadvantageous for the color development of the OHP fixed image. In addition, the polyvalent metal compound for introducing the ionic cross-linking structure can be added to a monomer component for forming a binder resin. It is preferable to select in the range of from 0.5 to 0.5 mol.

<Storage Modulus of Color Toner> In the color toner of the present invention, the storage modulus G ′ _{(90) at 90} ° C. and the storage modulus G ′ _{(150) at} 150 ° C. are controlled to specific ranges. It is characterized by points. Specifically, logG ′ ₍₉₀₎ is in the range of 3 to 4.5, and l
ogG ′ ₍₁₅₀₎ is in the range of 1 to 2.5. log
The value of G ′ ₍₉₀₎ is mainly reflected in the toughness at room temperature. When logG ' ₍₉₀₎ is less than 3, the toughness at normal temperature is not sufficiently exhibited, and the crush resistance and high hardness of the toner particles cannot be sufficiently satisfied.
Further, the glass transition point is low, and the storage stability is poor. On the other hand, when this value is larger than 4.5, a large amount of heat energy is required to form a smooth fixed image surface, and the fixing temperature range is undesirably high. The value of logG ' ₍₁₅₀₎ is mainly reflected in the state at the time of melting. logG '
_{When (150)} is smaller than 1, the wettability and adhesion to the fixing roller surface are high, and hot offset is likely to occur. On the other hand, if this value is larger than 2.5, the elasticity at the melting temperature is large, so that a sufficiently smooth fixed image surface cannot be formed.

Here, the storage elastic modulus G ' ₍₉₀₎ and the storage elastic modulus G' ₍₁₅₀₎ are determined by a cone / plate method using a rheometer "Solid meter: MR-3 type" (manufactured by Nippon Rheology Co., Ltd.). (Dyne / cm
² ). Here, the measurement conditions were as follows: a cone angle of 1.8 deg, a cone diameter of 32.0 mm, a wire diameter of 1.0 mm, a frequency of 0.1 Hz, a torsion angle of 2.0 deg, a measurement start temperature of 200 ° C. The temperature rate was 2 ° C per minute.

<Colorant> The colorant constituting the color toner of the present invention is not particularly limited, and a commonly used dye or pigment can be used. In addition,
In producing the color toner of the present invention, a masterbatch in which a pigment is dispersed and contained in a high concentration in advance by using a flushing process in a part of the binder resin is prepared, and the masterbatch is mixed with the remainder of the binder resin. To produce a color toner. The color toner thus manufactured is excellent in dispersibility of the colorant and wettability to the binder resin, improves color development, and further improves crush resistance and offset resistance of the toner. it can.

<Various Additives> The color toner of the present invention may contain various internal additives and external additives such as a charge control agent, if necessary. As the charge control agent, a conventionally known charge control agent can be used, but since it constitutes a part of the color toner particles, it is preferably colorless or white. Specific examples of preferred charge control agents include salicylic acid and zinc salts of salicylic acid derivatives. As the external additive, generally used fine particles such as inorganic fine particles and organic fine particles, fatty acids,
A lubricant composed of a fatty acid metal salt or the like can be used.
In particular, by adding a fatty acid metal salt, the coefficient of friction between the toner particles and other substances is reduced, and as a result, the stress applied to the toner particles is reduced, so that crushing of the toner particles and burying of external additives are more effective. It is preferable because it can be prevented.

<Production Examples / Particle Size Range> The method for producing the color toner of the present invention is not particularly limited, and it can be produced by a conventionally known method. The particle size of the color toner of the present invention is in the range of 1 to 30 μm,
From the viewpoint of improving the resolution and surface smoothness of the formed image, those having a volume average particle size in the range of 3 to 9 μm are preferable.

The color toner of the present invention may be used as a two-component developer by mixing with a carrier, or when the color toner is a magnetic toner, it may be used as a one-component developer consisting of only the color toner. Can also. As such carriers, conventionally known carriers can be used, but carriers having low magnetization and small specific gravity are preferable. By using such a carrier having a low magnetization and a low specific gravity, stress applied to toner particles during mixing and stirring is reduced. Specifically, the magnetization is 15 to 40 em
A carrier having a u / g and specific gravity of ³ to 7 g / cm ³ can be preferably used. From the viewpoint of improving the durability of the carrier, a carrier in which a resin coating layer is provided on the surface of magnetic particles, or a carrier in which magnetic powder is dispersed in resin particles can be preferably used.

The color toner of the present invention can be suitably used in a fixing process using a heat roller. Here, the heat roller used in the fixing process has a surface layer that comes into contact with the surface of the unfixed image on the transfer material made of an elastic material, and the soft roller has a good followability to unevenness due to color toner on the surface of the unfixed image. Is preferable because the smoothness of the surface of the fixed image can be further improved. However, in the fixing process as described above, hot offset is likely to occur due to the high adhesiveness of the molten toner to the heat roller surface. Therefore, it is usual to apply a large amount of a release agent such as silicone oil. However, when the color toner of the present invention is used, the amount of the release agent to be applied can be suppressed to a very small amount, so that the fixed image caused by the applied release agent has stickiness, unevenness, and the like. No final fixed image can be obtained.

[0027]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to only these. In addition,
Hereinafter, “parts” indicates “parts by weight”.

Example 1 Preparation of Copolymer (Binder Resin) Styrene, methyl methacrylate, monomethacryloyloxyethyl succinate, and zinc oxide were mixed with 3
A polymerizable mixture having a composition of 0: 67: 3: 0.3 (molar ratio) was copolymerized to prepare a copolymer having an ionic crosslinked structure. Preparation of Pigment Masterbatch A copolymer having an ionic cross-linking structure prepared in the same manner as described above, and a magenta pigment “CI Pigment No. 1
22 "was mixed at a weight ratio of 6: 4, and a flushing treatment was performed to prepare a pigment master batch. Production of Color Toner 100 parts of the copolymer prepared above, 20 parts of the pigment masterbatch prepared above, and 3 parts of zinc salt of 3,5-ditert-butylsalicylic acid were mixed with a Henschel mixer. After melt-kneading with an axial extruder, solidifying by cooling, and coarsely pulverized, colored particles having a volume average particle size of 8.5 μm were obtained using a particle collision type fine pulverizer and an airflow classifier. For 100 parts of the obtained colored particles, 0.5 part of hydrophobic silica "R-972" (manufactured by Nippon Aerosil Co., Ltd.) and 1.0 part of hydrophobic titania "T-805" (manufactured by Nippon Aerosil Co., Ltd.) And 0.2 parts of aluminum stearate (lubricant), and the mixture is mixed using a Henschel mixer to obtain the color toner T of the present invention.
1 was produced.

<Examples 2 to 5> Except that the copolymer having an ionic cross-linking structure and the polymerizable mixture used for preparing the pigment masterbatch had a composition according to the formulation shown in Table 1 below. In the same manner as in Example 1, color toners T2 to T5 of the present invention were produced.

<Comparative Examples 1 to 7> Same as Example 1 except that the polymerizable mixture used for preparing the copolymer and the pigment masterbatch had a composition according to the formulation shown in Table 1 below. To produce color toners H1 to H7 for comparison.

For each of the color toners obtained as described above, a rheometer “Solid meter: M
The storage elastic modulus G ′ ₍₉₀₎ and the storage elastic modulus G ′ ₍₁₅₀₎ were measured by a cone / plate method using “R-3 type” (manufactured by Nippon Rheology Co., Ltd.). Here, the measurement conditions were as follows: a cone angle of 1.8 deg, a cone diameter of 32.0 mm, a wire diameter of 1.0 mm, a frequency of 0.1 Hz, a torsion angle of 2.0 deg, a measurement start temperature of 200 ° C. The temperature rate was 2 ° C per minute. "LogG 'for each color toner
₍₉₀₎ "and" logG ' ₍₁₅₀₎ "are also shown in Table 1.

[0032]

[Table 1]

<Preparation of Carrier> The volume average particle diameter is 45 μm.
m, on the surface of a Cu—Fe-based core particle having a specific gravity of 5.0 at a ratio of 2.0% by weight with respect to the core particle,
A resin-coated carrier composed of a styrene-methyl methacrylate resin [styrene / methyl methacrylate = 4/6 (molar ratio)] was formed to prepare a resin-coated carrier.

<Preparation of Developer> The color toners (T1 to T5 and H1 to H5) obtained in the above Examples and Comparative Examples
7) and the above resin-coated carrier were mixed using a V-type mixer so that the toner concentration became 7% by weight, to prepare Developers 1 to 5 and Comparative Developers 1 to 7. .

<Evaluation of Developer> Using the developers 1 to 5 and the comparative developers 1 to 7 obtained as described above, an image forming test and a mixing and stirring test of the developers were performed, and the gloss (image surface) ), Offset resistance, toner particle size (crush resistance), developability and transferability were evaluated.

The glossiness and the anti-offset property were determined by forming a fixed image using a full-color copying machine "DC9028" (manufactured by Konica Corporation) in which the configuration of the fixing device was modified as follows. . (Configuration of Fixing Device) As shown in FIG. 1, a heater lamp 1 (halogen lamp, 600 W) is built in the center, and an LTV rubber layer 3
The heater roller 1 is built in the center and the fixing roller on which a hollow aluminum roller 2 having a diameter of 60 mm is formed.
A fixing device comprising a pressure roller having a TV rubber layer 4 formed thereon. In the same figure, 5 is a cleaning roller, 6 is an oil application roller, 7 is an oil supply roller, 8 is a silicon oil storage tank, and 9 is an oil regulating blade. In addition,
The surface temperatures of the fixing roller and the pressure roller were adjustable, and the fixing linear speed was set to 160 mm / sec.

The toner particle size, developability and transferability were measured using a full-color copying machine “DC9028” (manufactured by Konica Corporation) modified so that the developing device could be driven alone. The agent was charged into a developing device, and mixed and stirred for 3 hours in an environment at a temperature of 40 ° C. and a relative humidity of 60%, and evaluated.

(Evaluation Items) Glossiness (Smoothness of Image Surface) The surface temperature of the fixing roller and the surface temperature of the pressure roller were set to 1
The temperature was set to 30 ° C., and the glossiness of the formed solid black fixed image was measured according to JIS Z8741. Offset Resistance The surface temperature of the fixing roller and the pressure roller was sequentially increased, and the temperature at which hot offset occurred was measured. Toner particle size (crush resistance) The volume average particle size of the color toner was measured before and after stirring in the developing device. Developability Before and after stirring in the developing device, the toner amount per unit area (mg / cm ² ) of the color toner conveyed to the surface of the photoconductor for developing the electrostatic latent image was measured. Transferability Before and after stirring in the developing device, the ratio (%) of the amount of toner transferred onto the support to the amount of toner transferred to the surface of the photoreceptor was measured. The results are shown in Table 2 below.

[0039]

[Table 2]

As can be seen from the results in Table 2, the color toners T1 to T of the present invention produced according to Examples 1 to 5
No. 5 is excellent in all of the smoothness, offset resistance, crush resistance, developability and transferability of the image surface, and can form a stable color-fixed image. On the other hand, the color toners H1 to H5 whose values of logG ′ ₍₉₀₎ and logG ′ ₍₁₅₀₎ are out of the range of the present invention.
Are not able to exhibit the above-mentioned performances in a well-balanced manner. The color toners H6 to H7 using the linear polyester resin as the binder resin are:
In particular, it has poor offset resistance.

[0041]

According to the present invention, the binder resin is a (styrene-) (meth) acrylate (co) polymer having an ionic cross-linking structure, and has a storage modulus of G ' ₍₉₀₎ and a storage modulus of G' _(90). Since the storage elastic modulus G ′ ₍₁₅₀₎ is controlled in a suitable range, a color fixed image having excellent surface smoothness suitable for full-color copying can be formed, and hot offset occurs in a fixing process using a heat roller. Do not let. In addition, it has high strength that is not crushed even by stress due to stirring in the developing device, and high hardness that does not cause burying of external additives, etc. A stable color fixed image can be formed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a modified fixing device in a full-color copying machine used for an image forming test.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heater lamp 2 Hollow aluminum roller 3 LTV rubber layer 4 HTV rubber layer 5 Cleaning roller 6 Oil application roller 7 Oil supply roller 8 Silicon oil storage tank 9 Oil regulating blade

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-353866 (JP, A) JP-A-3-96963 (JP, A) JP-A-3-231757 (JP, A) JP-A-2- 298956 (JP, A) JP-A-4-56869 (JP, A) JP-A-4-98264 (JP, A) JP-A-62-116063 (JP, A) JP-A-2-184862 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/087 G03G 9/09

Claims (2)

(57) [Claims] 1. A color toner containing at least a binder resin and a colorant, wherein the binder resin is a styrene- (meth) acrylate copolymer having an ionic cross-linking structure or a (meth) acrylate (co) having an ionic cross-linking structure. The storage elastic modulus at 90 ° C. of the color toner is represented by G ′
₍₉₀₎ (dyne / cm ² ), wherein the storage elastic modulus at 150 ° C. is defined as G ′ ₍₁₅₀₎ (dyne / cm ² ). <Conditions> 3 ≦ logG ′ ₍₉₀₎ ≦ 4.5 1 ≦ logG ′ ₍₁₅₀₎ ≦ 2.5 2. A half-ester compound represented by the following formula 1, wherein a copolymer having an ionic cross-linking structure comprises 0 to 49 mol% of a styrene monomer, 50 to 99 mol% of a (meth) acrylate monomer, and The color toner according to claim 1, wherein the color toner is obtained by reacting a polyvalent metal compound with a copolymer synthesized from 1 to 10 mol%. Embedded image Wherein R represents a hydrogen atom or a methyl group;
L represents a divalent linking group having an ester bond in the molecular chain and having 3 or more carbon atoms. ]