WO2019088620A1

WO2019088620A1 - Electrostatic charge image developing toner

Info

Publication number: WO2019088620A1
Application number: PCT/KR2018/012911
Authority: WO
Inventors: Keiichi Ishikawa; Osamu Ieda; Takahiro DANNO
Original assignee: Hp Printing Korea Co., Ltd.
Priority date: 2017-10-31
Filing date: 2018-10-29
Publication date: 2019-05-09
Also published as: JP2019082619A

Abstract

An electrostatic charge image developing toner comprises a binder resin, a colorant, and wax. In a differential scanning calorimetry (DSC) curve associated with the electrostatic charge image developing toner, a melting point MP 2 is between 70 and 83 ºC, inclusive. In the DSC curve, a negative rate of change in heat flow dHF 21/dT defined between a temperature T 21 and a temperature T 22, is between -0.50 mW/ºC and -0.10 mW/ºC, inclusive, wherein T 21 and T 22 are lower than MP 2. In the DSC curve, a positive rate of change in heat flow dHF 22/dT defined between a temperature T 23, and a temperature T 24, is between 0.50 mW/ºC and 1.80 mW/ºC, inclusive, wherein T 23 and T 24 are higher than MP 2.

Description

ELECTROSTATIC CHARGE IMAGE DEVELOPING TONER

Various characteristics of an electrostatic charge image developing toner (hereinafter also simply referred to as "toner") are use in electrophotographic image forming systems. During fixing, for example, the toner includes such characteristics as a low-temperature fixing property, a hot-offset resistance property, as well as a property to impart gloss and coloring to images.

A low-temperature fixing property may be used to reduce the power consumption of a printer. In order to reduce the fixing temperature of a toner, the melt viscosity of the toner may be controlled at different temperatures under heating. One example method adds a crystalline resin to an amorphous resin, which is a main component of the toner.

To suppress the image hot-offset, the resin may have a certain melt viscosity or more under heating so that the toner does not migrate to a contact surface of a fixing component (roller or film), and that the toner have releasability from that surface. The releasability may be developed when a component such as wax forms a layer on a toner layer in a molten state.

FIG. 1 is a diagram schematically showing a DSC curve during a second temperature-rising for an electrostatic charge image developing toner.

FIG. 2 is a diagram schematically showing a DSC curve during a second temperature-rising for an example electrostatic charge image developing toner.

FIG. 3 is diagram schematically showing a DSC curve representing a thermal characteristic of a wax.

In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted.

Examples of an electrostatic charge image developing toner will now be described.

An example electrostatic charge image developing toner (hereinafter also simply referred to as "toner") comprises a binder resin, including an amorphous resin and a crystalline resin, a colorant, and wax, and has the thermal characteristics described below.

Thermal characteristics of toner

An example electrostatic charge image developing toner has predetermined thermal characteristics determined from a DSC curve obtained by differential scanning calorimetry (DSC). As a DSC curve may be affected by thermal history of a sample (i.e., toner), a first temperature-rising and a following temperature-lowering may be carried out, and thereafter the thermal characteristics based on a DSC curve obtained during a second (or subsequent) temperature-rising may be determined. This enables to evaluate the characteristics while removing the effects of thermal history. Further, a thermal characteristic during the temperature-lowering after the first temperature-rising may also be considered.

FIG. 1 is a diagram schematically showing a DSC curve for an electrostatic charge image developing toner (comprising a binder resin, including an amorphous resin and a crystalline resin, a colorant, and wax). As indicated above, this is a DSC curve during a second temperature-rising.

As shown in FIG. 1, as the temperature rises, the resin component included in the toner changes from a glass state to a molten state in the vicinity of a glass transition temperature Tge. As the temperature further rises thereafter, the wax component included in the toner melts in the vicinity of a melting point MPe. Then, the peak in DSC associated with the melting of the wax component is relatively acute (or pointy), in that the curve in the vicinity of the melting point MPe is steep relative to the rest of the DSC curve. Further, a temperature range in which the melting of the resin component occurs can be relatively easily distinguished from a temperature range in which the melting of the wax component occurs; as the temperature rises, the melting of the wax component occurs after the melting of the resin component.

During a fixing of a toner image, the toner melts in response to an amount of heat supplied, and molten wax bleeds out on an upper layer of the image.

In the case of the toner associated with the DSC curve shown in FIG. 1, substantially all amount of the wax melts at a predetermined temperature and bleeds out on the upper layer. This results in an excess amount of the wax in the upper layer of the image, which lowers the frictional force on the image surface and affects ease of writing with a writing tool such as a pencil.As the amount of wax increases on a surface layer during the fixing of the toner image, the amount of wax is also increased on an image surface after the fixing has been carried out. This may affect ease of writing on the image surface, as a friction force between the image surface and a writing tool may be reduced by the wax. Further, a difference in the friction force may be felt when writing on image surfaces, relative to writing on non-image surfaces.

With reference to FIG. 2, an example electrostatic charge image developing toner (also referred to herein as "toner") comprises a binder resin, including an amorphous resin and a crystalline resin, a colorant, and wax. After performing a first temperature-rising and a following temperature-lowering, the toner shows the following characteristics in a curve measured during a second temperature-rising in a differential scanning calorimeter.

A melting point MP ₂ is 70.0 ºC or more and 83.0 ºC or less (e.g. within a range of 70.0 ºC to 83.0 ºC, inclusive).

A rate of change in heat flow dHF ₂₁/dT between a temperature T ₂₁, which is lower than MP ₂ and at which a heat flow is lower than the heat flow at 60.0 ºC by 0.5 mW, and a temperature T ₂₂, which is lower than MP ₂ by 2 ºC, is -0.50 mW/ºC or more and -0.10 mW/ºC or less (e.g. within a range of -0.50 mW/ºC to -0.10 mW/ºC, inclusive).

A rate of change in heat flow dHF ₂₂/dT between a temperature higher than MP ₂ by 1 ºC and a temperature T ₂₄, which is higher than MP ₂ and at which a heat flow is lower than the heat flow at 60.0 ºC by 0.5 mW, is 0.50 mW/ºC or more and 1.80 mW/ºC or less (e.g. within a range of 0.50 mW/ºC to 1.80 mW/ºC, inclusive).

In the example electrostatic charge image developing toner, as wax emerges on the surface of toner particles in an amount such that the toner achieves a molten state, an amount of wax present on an image surface after fixing can be made constant (or more uniform), and a low-temperature fixing property, a hot-offset resistance property, and/or a writing property associated with ease of writing on images printed on the image surface, may be improved.

FIG. 2 shows a DSC curve of the example toner (also during a second temperature-rising). The resin component of the toner melts in the vicinity of a glass transition temperature Tg ₂ and the wax component melts in the vicinity of a melting point MP ₂, as the temperature rises. However, the peak in the DSC curve associated with the melting of the wax has a mild gradient in particular in a region of the curve corresponding to a temperature that is lower than the melting point MP ₂. Further, a temperature range in which the melting of the resin component occurs is not clearly distinguishable from and may overlap with a temperature range in which the melting of the wax component occurs. For example, during a temperature rise, the melting of the wax component begins while the melting of the resin component is underway, and these meltings may occur simultaneously at least in part.

In accordance with the above-described toner, the wax component may be melted in an amount to achieve a molten state of the resin component. When such a toner is used for developing an image, separation between the wax component and the resin component is less likely to occur and an upper layer formed on the image surface may include wax in an amount that improves a writing property (associated with ease of writing on the printed image with a writing tool). Accordingly, the touch and feel of the image surface may be more constant and/or uniform.

An example shape of the DSC curve will be further described.

Thermal characteristics during second temperature-rising

In FIG. 2, which shows a DSC curve during a second temperature-rising, the glass transition temperature is indicated as Tg ₂ and the melting point is indicated as MP ₂. The glass transition temperature Tg ₂ may be a temperature of 48.0 ºC or more, or 49.0 ºC or more in some examples, or in other examples, 50.0 ºC or more. Further, the glass transition temperature Tg ₂ may be 58.0 ºC or less, or 56.0 ºC or less in some examples, or in yet other examples, 54.0 ºC or less.

Additionally, the melting point MP ₂ may be 70.0 ºC or more, or 72.0 ºC or more in some examples, or in other examples, 74.0 ºC or more. Further, the melting point MP ₂ may be 83.0 ºC or less, or 81.0 ºC or less in some examples, or in yet other examples, 79.0 ºC or less.

Further, the DSC curve may have a mild gradient in the vicinity of the melting point MP ₂.

For example, where a heat flow at 60 ºC is H ₆₀ mW, T ₂₁ and T ₂₄, represent temperatures at which the heat flow is less than H ₆₀ mW by 0.5 mW in each of a lower temperature region and a higher temperature region , respectively, relative to the melting point MP ₂.

Further, a temperature lower than the melting point MP ₂ by 2.0 ºC is denoted as T ₂₂, and a temperature higher than the melting point MP ₂ by 1.0 ºC is denoted as T ₂₃.

Then, in a range not lower than the temperature T ₂₁ and not higher than the temperature T ₂₂, the gradient of the DSC curve, i.e., a rate of change in heat flow (dHF ₂₁/dT) may be -0.50 mW/ºC or more, or -0.45 mW/ºC or more according to some examples, or other examples, -0.40 mW/ºC or more. The rate of change in heat flow (dHF ₂₁/dT) may be of -0.10 mW/ºC or less.

Likewise, in a range not lower than the temperature T ₂₃ and not higher than the temperature T ₂₄, a rate of change in heat flow (dHF ₂₂/dT) may be 0.50 mW/ºC or more, or 0.52 mW/ºC or more in some examples, or in other examples 0.54 mW/ºC or more. Further, the rate of change in heat flow (dHF ₂₂/dT) may be 1.80 mW/ºC or less, or in some examples, 1.70 mW/ºC or less, or in other examples 1.60 mW/ºC or less.

It is noted that, in FIG. 2, dHF ₂₁/dT and dHF ₂₂/dT are examples.

When the example toner having the aforementioned thermal characteristics is used, the wax component may be melted in an amount corresponding to a molten state of the resin component, and an upper layer of the image may include an amount of wax such that a writing property with a writing tool can be improved, and the touch and feel of the image surface may be more constant and/or uniform.

In the foregoing, the effects of thermal history is removed by performing a temperature-rising and a following temperature-lowering, and a melting point and the like are determined during a second (or subsequent) temperature-rising. These values may differ from a melting point and the like determined from a DSC curve during the first temperature-rising, due to the effects of thermal history.

For example, a toner that exhibits the aforementioned numerical values during a second temperature-rising may have the following values during the first temperature-rising:

- a glass transition temperature Tg ₁ of 49.0 to 59.0 ºC and a melting point MP ₁ of 72.0 to 85.0 ºC;

- a rate of change in heat flow (dHF ₁₁/dT) of -1.20 to -0.10 mW/ºC in a temperature range of not lower than 60 ºC and not higher than a temperature lower than the melting point MP ₁ by 2.0 ºC; and

- a rate of change in heat flow (dHF/dT ₂₂) of 0.80 to 2.20 mW/ºC in a temperature range of not less than a temperature (T ₁₂) higher than the melting point MP ₁ by 1.0 ºC and not higher than a temperature lower than the melting point MP ₁ and at which a heat flow is lower than the heat flow at 60.0 ºC by 0.5 mW.

Thermal characteristics during temperature-lowering

While FIG. 2 shows thermal characteristics during a temperature-rising (during a second temperature-rising), the thermal characteristics of a toner may be established during a temperature-lowering. To remove the effects of thermal history of the toner, a first temperature-lowering is carried out after performing a first temperature-rising.

During a temperature-lowering, a melting point is denoted as MP _d. The melting point MP _d may be 70.0 ºC or more, or in some examples, 71.0 ºC or more, and or in other examples, 72.0 ºC or more. Further, the melting point MP _d may be 80.0 ºC or less, or in some examples, 79.0 ºC or less, or in other examples, 78.0 ºC or less.

Further, in a range not lower than 60.0 ºC and not higher than 65.0 ºC, a rate of change in heat flow (dHF _d1/dT) may be 0.20 mW/ºC or more, or 0.21 mW/ºC or more in some examples, or in other examples, 0.22 mW/ºC or more. Further, the rate of change in heat flow (dHF _d1/dT) may be 0.50 mW/ºC or less, or 0.45 mW/ºC or less in some examples, or 0.40 mW/ºC or less in yet other examples.

Further, a temperature higher than the melting point MP _d by 2.0 ºC is denoted as T _d3, and a temperature higher than the melting point MP _d by 3.0 ºC is denoted as T _d4. Then, in a range not lower than the temperature T _d3 and not higher than the temperature T _d4, a rate of change in heat flow (dHF _d2/dT) may be -5.00 mW/ºC or more, -4.50 mW/ºC or more in some examples, or in other examples, -4.00 mW/ºC or more. Further, the rate of change in heat flow (dHF _d2/dT) may be -0.30 mW/ºC or less, or in some examples, -0.50 mW/ºC or less, or in other examples, -0.80 mW/ºC or less.

The examples electrostatic charge image developing toner comprises, at least, a colorant, a releasing agent (such as wax) and a binder resin.

The binder resin comprises an amorphous resin and a crystalline resin. For example, an amorphous polyester resin may be used as the amorphous resin and a crystalline polyester resin may be used as the crystalline resin.

As the amorphous resin, an amorphous styrene-acrylic resin or other resins may also be used. Further, other crystalline resins may also be used as the crystalline resin.

The amorphous polyester resin may have a weight-average molecular weight ranging from 5000 to 50000, inclusively, in some examples, or from 10000 to 40000, inclusively, in other examples. When the weight-average molecular weight is within a range of 5000 to 50000, inclusive, a toner having improved low-temperature fixing property and storage property can be achieved. The weight-average molecular weight may be 50000 or less, in some examples, to prevent deterioration of the low-temperature fixing property. The weight-average molecular weight may be 5000 or more, in some examples, to maintain a good storage property.

The weight-average molecular weight of the amorphous polyester resin may be controlled by adjusting a synthesis temperature, a synthesis time and the like. Further, the weight-average molecular weight of the amorphous polyester resin may be determined, for example, by gel permeation chromatography (GPC) measurement.

The amorphous polyester resin may be synthesized by performing a dehydration condensation of a polycarboxylic acid component and a polyol component, and by subjecting the resin obtained by the dehydration condensation to urethane extension. The amorphous polyester resin may be a mixture of two or more amorphous polyester resins, when used for a binder resin according to some examples.

The polycarboxylic acid component which may be used for synthesizing the amorphous polyester resin includes generic organic polycarboxylic acids, such as aliphatic carboxylic acids, aromatic carboxylic acids, anhydrides thereof, and lower alkyl (with 1 to 4 carbons) esters thereof. Examples include aliphatic (including cycloaliphatic) dicarboxylic acids such as alkane dicarboxylic acids with 2 to 50 carbons (oxalic acid, malonic acid, succinic acid, adipic acid, lepargylic acid, sebacic acid and the like), and alkene dicarboxylic acids with 4 to 50 carbons (alkenyl succinic acid such as dodecenyl succinic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, glutaconic acid and the like). The aromatic dicarboxylic acids include aromatic dicarboxylic acids with 8 to 36 carbons (phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid and the like), anhydrides thereof, and lower alkyl (with 1 to 4 carbons) esters thereof.

The polyol component which may be used for synthesizing the amorphous polyester resin includes generic polyols. Examples include aliphatic diols with 2 to 36 carbons (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butane diol, 2,3-butane diol, 1,5-pentane diol, 2,3-pentane diol, 1,6-hexane diol, 2,3-hexane diol, 3,4-hexane diol, neopentyl glycol, 1,7-heptane diol, dodecane diol and the like); polyalkylene ether glycols with 4 to 36 carbons (diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and the like); 2 to 4 carbon alkylene oxide (hereinafter AO) (such as ethylene oxide (hereinafter EO), propylene oxide (hereinafter PO) and butylene oxide) adducts of the above aliphatic diols with 2 to 36 carbons (with 2 to 30 added moles); cycloaliphatic diols with 6 to 36 carbons (1,4-cyclohexane dimethanol, hydrogenated bisphenol A and the like); 2 to 4 carbon AO adducts of the above cycloaliphatic diols (with 2 to 30 added moles); and 2 to 4 carbon AO adducts of bisphenols (bisphenol A, bisphenol F, bisphenol S and the like) (with 2 to 30 added moles).

A polyisocyanate component to perform urethane extension and usable for synthesizing the amorphous polyester resin includes generic organic polyisocyanate compounts. Examples include diphenylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, p-phenylene diisocyanate, toluene diisocyanate, naphtalene diisocyanate, dibenzyl dimethylmethane-p,p'-diisocyanate, hexamethylene diisocyanate, norbornene diisocyanate, nurates compounds thereof and adducts thereof.

Further, the crystalline polyester resin has a weight-average molecular weight ranging from 5000 to 15000, inclusively, in some examples, and from 7000 to 14000, inclusively, in other examples. When the weight-average molecular weight is within a range of 5000 to 15000, inclusive, a toner having improved low-temperature fixing property and storage property can be achieved. The weight-average molecular weight is 15000 or less in some examples, to prevent deterioration of the low-temperature fixing property. The weight-average molecular weight may be 5000 or more in some examples, to prevent deterioration of the storage property due to compatibilization with the amorphous polyester resin.

The weight-average molecular weight of the crystalline polyester resin may be controlled by adjusting a synthesis temperature, a synthesis time and the like. The weight-average molecular weight of the crystalline polyester resin may be determined, for example, by gel permeation chromatography (GPC) measurement.

The crystalline polyester resin may be synthesized by performing a dehydration condensation of a polycarboxylic acid component and a polyol component. The crystalline polyester resin may be a mixture of two or more crystalline polyester resins, when used for a binder resin according to the above-described examples.

The polycarboxylic acid component which may be used for synthesizing the crystalline polyester resin includes aliphatic polycarboxylic acids and the like. Examples include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, decanedioic acid, dodecanedioic acid and the like.

The polyol component which may be used for synthesizing the crystalline polyester resin includes aliphatic polyols. Examples include ethylene glycol, 1,4-butane diol, 1,6-hexane diol, 1,8-octane diol, 1,9-nonane diol, 1,10-decane diol and the like.

The wax (releasing agent) which may be included in the example toner may include solid paraffin wax, microwax, rice wax, aliphatic amide wax, aliphatic wax, aliphatic monoketones, aliphatic metal salt wax, aliphatic ester wax, partly saponified aliphatic ester wax, silicone varnish, higher alcohols, carnauba wax and the like. Further, polyolefins such as low molecular-weight polyethylene and polypropylene may also be used.

When a tetrahydrofuran-soluble portion of the wax is measured by gel permeation chromatography, components with a molecular weight of 1000 or less occupy 0.2 % or more in a peak area ratio in the chromatogram, according to some examples. Further, the components with a molecular weight of 1000 or less occupy 0.40 % or less in some examples, or 0.38 % or less in other examples, and 0.35 % or less in yet other examples.

When the components with a molecular weight of 1000 or less are in such a range, the toner has a good storage property.

The aforementioned thermal characteristics of the example electrostatic charge image developing toner may be suitably achieved, depending on the type of wax used.

As the colorant, either an inorganic colorant or an organic colorant may be used. Examples thereof include dyes and pigments such as carbon black, lamp black, magnetite, black titanium oxide, chrome yellow, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, hansa yellow G, rhodamine 6G, calco oil blue, quinacridone, benzidine yellow, rose bengal, malachite green lake, quinoline yellow, C. I. Pigment Red 48:1, C. I. Pigment Red 57:1, C. I. Pigment Red 122, C. I. Pigment Red 184, C. I. Pigment Red 269, C. I. Pigment Yellow 12, C. I. Pigment Yellow 17, C. I. Pigment Yellow 93, C. I. Pigment Yellow 97, C. I. Pigment Yellow 155, C. I. Pigment Yellow 180, C. I. Solvent Yellow 93, C. I. Solvent Yellow 162, C. I. Pigment Blue 5:1, C. I. Pigment blue 15:3. These may be used alone (e.g. in isolation) or in mixture.

Further, the example electrostatic charge image developing toner may contain iron element, silicon element and sulfur element. The content of the iron element may be within a range of 1.0 Х 10 ³ ppm to 1.0 Х 10 ⁴ ppm, inclusive. The content of the silicon element may be within a range of 1.0 Х 10 ³ ppm to 5.0 Х 10 ⁴ ppm, inclusive. The content of the sulfur element may be within a range of 500 ppm to 3000 ppm, inclusive. The ppm (parts per million) unit express a mass fraction.

The iron element and the silicon element may be components derived from an aggregating agent used in the production of the example toner, and the sulfur element may be a component derived from a catalyst and the aggregating agent. Accordingly, the contents of the iron element and the silicon element in the example electrostatic charge image developing toner may be controlled by adjusting the type and amount of the aggregating agent used, and the content of the sulfur element may be controlled by adjusting the type and amount of the catalyst and the aggregating agent used.

The content of the iron element in the electrostatic charge image developing toner may be 1.0 Х 10 ³ ppm or more, as stated above, or 1.2 Х 10 ³ ppm or more in some example, or in yet other examples, 1.5 Х 10 ³ ppm or more. Further, the content of the iron element may be 1.0 Х 10 ⁴ ppm or less, or 9.0 Х 10 ³ ppm or less in some examples, or in yet other examples, 8.0 Х 10 ³ ppm or less.

When the content of the iron element is in such a range, the toner may be used as an electrostatic charge image developing toner with improved properties. An iron element content of 1.0 Х 10 ⁴ ppm or less may prevent a minimum fixing temperature (MFT) of the toner from becoming too high. Further, the iron element content may be of 1.0 Х 10 ³ ppm or more , to form toner particles.

The content of the silicon element in the electrostatic charge image developing toner may be 1.0 Х 10 ³ ppm or more, as stated above, or in some examples, 1.2 Х 10 ³ ppm or more, or in other examples, 1.5 Х 10 ³ ppm or more. Further, the content of the silicon element may be 5.0 Х 10 ³ ppm or less, or in some examples, 4.5 Х 10 ³ ppm or less, or in yet other examples, 4.0 Х 10 ³ ppm or less.

When the content of the silicon element is in such a range, the toner may be used as an electrostatic charge image developing toner. The silicon element content of 5.0 Х 10 ³ ppm or less may prevent a minimum fixing temperature (MFT) of the toner from becoming too high. Further, a silicon element content of 1.0 Х 10 ³ ppm or more may be used to form toner particles.

The content of the sulfur element in the example electrostatic charge image developing toner may be 500 ppm or more, as stated above, and the content of the sulfur element may be 3000 ppm or less, or 2500 ppm or less in some examples, or in yet other examples 2000 ppm or less.

When the content of the sulfur element is 500 ppm or more and 3000 ppm or less, the toner may be used as an electrostatic charge image developing toner. A sulfur element content of 3000 ppm or less may be used for imparting the toner with improved electrical properties. A sulfur element content of 500 ppm or more may be used to form toner particles.

The content of each element in the electrostatic charge image developing toner can be measured by fluorescent X-ray analysis. Further, the toner may also include other additives.

Examples

Further examples of the electrostatic charge image developing toner will be described.

An example electrostatic charge image developing toner is produced by making and/or using crystalline resin and amorphous resin, colorant and wax, respectively.

Method of producing electrostatic charge image developing toner

Process 1: preparation of amorphous polyester resin

Esterification

A 500 mL separable flask was charged with 100 g of 2-mole adduct of propylene oxide of bisphenol A (available from Adeka Corp., Product name: Adeka Polyether BPX-11), 34.74 g of maleic acid anhydride (abbr. MA, available from Adeka Corp.), and 0.98 g of paratoluene sulfonic acid monohydrate (abbr. PTSA, available from Wako Junyaku K.K.). Then, nitrogen was introduced into the flask and, while stirring the flask with a stir device, the mixture of 2-mole adduct of propylene oxide of bisphenol A, maleic acid anhydride and paratoluene sulfonic acid monohydrate was heated to 70 ºC and dissolved. After that, the temperature of the mixed solution in the flask was elevated to 97 ºC, while stirring the flask. The flask was then vacuumed (to 10 mPa·s or less) and, while stirring the flask, a dehydration condensation reaction between 2-mole adduct of propylene oxide of bisphenol A and maleic acid anhydride was performed at 97 ºC for 45 hours to form a polyester resin.

The polyester resin formed in the esterification was partly removed from the flask to identify physical properties.

The resulting polyester resin had a weight-average molecular weight of 4450.

Urethane extension

After returning the pressure in the flask to normal pressure, 9.05 g of diphenylmethane diisocyanate (abbr. MDI, available from Wako Junyaku K.K.) and 29.02 g of toluene (available from Wako Junyaku K.K.) were added. Thereafter, nitrogen was introduced into the flask and, while stirring the flask, the polyester resin obtained in the esterification and diphenylmethane diisocyanate were reacted at 97 ºC until unreacted diphenylmethane diisocyanate was depleted to form a urethane extended polyester resin. The depletion of unreacted diphenylmethane diisocyanate was confirmed by removing part of the solution from the flask, measuring the solution with an infrared spectrophotometer and determining the absence of an isocyanate peak around 2275 cm ^-1.

Collection

An amorphous polyester resin was obtained by evaporating toluene from the solution obtained in the urethane extension and in which the urethane extended polyester resin had been formed.

The resulting amorphous polyester resin had a weight-average molecular weight of 14030 and a glass transition temperature of 60.3 ºC.

Process 2: preparation of amorphous polyester resin dispersion

A 3L dual jacket reaction vessel was charged with 300 g of the amorphous polyester resin prepared according to Process 1, 250 g of methyl ethyl ketone (hereinafter MEK), and 50 g of isopropyl alcohol (hereinafter IPA). Then, the amorphous polyester resin obtained in Process 1 was dissolved in a mixed solvent of MEK and IPA under an atmosphere of about 30 ºC, while stirring the flask with a semicircular impeller. Thereafter, 27 g of 5 % aqueous ammonia solution was slowly added to the reaction vessel, while stirring the reaction vessel, followed by the addition of 1200 g of water at a rate of 20 g/min to form an emulsion liquid. After that, the mixed solvent of MEK and IPA was removed from the emulsion liquid by vacuum distillation to obtain amorphous polyester resin latex.

Particles in the resulting amorphous polyester resin latex had a volume average particle size Dv50 of 129 nm and a volume average particle size distribution index GSDv of 1.18.

Process 3: preparation of crystalline polyester resin

A 500 mL separable flask was charged with 198.7 g of 1,9-nonane diol (available from Wako Junyaku K.K.), 250.6 g of dodecanedioic acid (available from Wako Junyaku K.K.), and 0.45 g of paratoluene sulfonic acid monohydrate (abbr. PTSA, available from Wako Junyaku K.K.). Then, nitrogen was introduced into the flask and, while stirring the flask with a stir device, the mixture of 1,9-nonane diol, dodecanedioic acid and PTSA was heated to 80 ºC and dissolved. After that, the temperature of the mixed solution in the flask was elevated to 97 ºC, while stirring the flask. The flask was then vacuumed (to 10 mPa·s or less) and, while stirring the flask, a dehydration condensation reaction between 1,9-nonane diol and dodecanedioic acid was performed at 97 ºC for 5 hours to obtain a crystalline polyester resin.

The resulting crystalline polyester resin had a weight-average molecular weight of 13304 and a melting point of 67.03 ºC.

Process 4: preparation of crystalline polyester resin dispersion

A 3L dual jacket reaction vessel was charged with 300 g of the crystalline polyester resin prepared according to Process 3, 250 g of MEK, and 50 g of IPA. Then, the crystalline polyester resin obtained in Process 3 was dissolved in a mixed solvent of MEK and IPA under an atmosphere of about 30 ºC, while stirring the flask with a semicircular impeller. Thereafter, 25 g of 5 % aqueous ammonia solution was slowly added to the reaction vessel, while stirring the reaction vessel, followed by the addition of 1200 g of water at a rate of 20 g/min to form an emulsion liquid. After that, the mixed solvent of MEK and IPA was removed from the emulsion liquid by vacuum distillation to obtain crystalline polyester resin latex.

Particles in the resulting crystalline polyester resin latex had a volume average particle size Dv50 of 136 nm and a volume average particle size distribution index GSDv of 1.19.

Process 5: preparation of cyan pigment dispersion

A reaction vessel having a volume of 3L and equipped with a stirrer, thermometer and a condenser was charged with 540 g of a cyan pigment (available from Dainichi Seika Kogyo K.K., ECB303), 27 g of an anionic surfactant (available from Dow Chemical Company, product name: Dowfax2A1) and 2450 g of distilled water, and then pre-dispersion was performed for about 10 hours with gentle stirring. After perforing the pre-dispersion for 10 hours, 400 g of glass beads with a diameter of 0.8 mm or more and 1 mm or less were added and dispersed in a bead mill (ZetaRS of Netzsch GmbH, Germany) for 4 hours. A colorant dispersion was obtained thereby.

The resulting cyan pigment particles had a volume average particle size Dv50 of 170 nm and a volume average particle size distribution index GSDv of 1.24. The concentration of the colorant in the resulting colorant dispersion was 18.1 wt%.

Process 6: preparation of example wax dispersion (1st test wax dispersion)

A reaction vessel was charged with 270 g of Wax A from Table 1, 2.7 g of an anionic surfactant (Dowfax2A1), and 400 g of ion exchange water. After heating the inside of the hermetic reaction vessel to 110 ºC, a homogenizer (available from IKA Company, product name: ULTRA-TURRAX T50) was used for dispersing, and then a high pressure homogenizer (Yoshida Kikai Kogyo K.K., product name: NanoVater NVLES008) was used to perform dispersing 360 minutes. 250 g ion exchange water was added to the obtained dispersion, and a first wax dispersion was obtained after making it uniform by stirring. The concentration of the wax in the resulting wax dispersion was 29.1 wt%.

As indicated in Table 1, tangential withdrawal temperature (ºC), endothermic onset temperature (ºC) and melting point (peak: ºC) are considered as wax properties. These are shown in FIG. 3. FIG. 3 is one example of a DSC curve of wax, and a tangential withdrawal temperature, an endothermic onset temperature and a melting point are shown.

The tangential withdrawal temperature denotes a point at which a heat flow from a previous temperature range starts to deviate from a baseline (linear portion). Further, the endothermic onset temperature denotes a cross point between the baseline and a tangent line having a minimum gradient.

Process 7: preparation of other example wax dispersions

2nd to 7th test wax dispersions, were obtained with a similar process to Process 6, while using Waxes B to G, respectively, from Table 1 instead of Wax A.

Further, 8th to 10th test wax dispersions, which are dispersions of comparative test examples, were obtained with a similar process to Process 6, while using comparative waxes indicated in Table 1 (Behenyl behenate, HNP-51, and polyethylene wax) instead of Wax A.

Table 1 shows the tangential withdrawal temperatures, endothermic onset temperatures and melting points for the different types of wax that were used.

Table 1

Process 8: preparation of example toner (Test Example 1)

A 3L reaction vessel was charged with 544.1 g of the amorphous polyester resin latex obtained in Process 2, 47.6 g of the crystalline polyester resin latex obtained in Process 4, 78.1 g of the colorant dispersion obtained in Process 5, 106.1 g of the first wax dispersant (releasing agent dispersant) obtained in Process 6, 7.0 g of an anionic surfactant (Dowfax2A1), and 1109 g of deionized water. After that, the reaction vessel was stirred for 3 minutes with a homogenizer (ULTRA-TURRAX T50). Thereafter, 63.2 g of polysilica iron with a concentration of 3.0 wt% (available from Suido Kiko Kaisha, product name: PSI-100) was added as an aggregating agent. Then the reaction vessel was stirred with the homogenizer and the temperature of the mixed solution in the reaction vessel was elevated to 44 ºC at a rate of 1 ºC/min, and further to 47 ºC at a rate of 0.7 ºC/min, and the temperature was maintained at 47 ºC until primary aggregated particles were obtained with a volume average particle size of 5 μm or more and 6 μm or less. The stirring of the reaction vessel was performed by controlling the rotation speed of the rotary blade of the homogenizer so that a stirring state can be maintained in response to a change in viscosity of the mixed solution in the reaction vessel. It was determined that the primary aggregated particles had reached the predetermined volume average particle size, by removing part of the mixed solution from the reaction vessel and analyzing the primary aggregated particles contained in the solution.

After that, 212.0 g of the amorphous polyester resin latex obtained in Process 2 was added to the reaction vessel and, while stirring the reaction vessel, the primary aggregated particles and the amorphous polyester resin were aggregated for 60 minutes to form a coated layer of the amorphous polyester resin on the outer surfaces of the primary aggregated particles, and a dispersion of coated aggregated particles was obtained. Thereafter, 63.0 g of aqueous sodium hydroxide solution with a concentration of 1N was added to the reaction vessel, and the reaction vessel was maintained for 20 minutes while stirring. After that, while stirring the reaction vessel, the mixed solution in the reaction vessel was heated to 89 ºC, and the temperature was maintained at 89 ºC until the circularity of the coated aggregated particles reached 0.97 or more and 0.98 or less.

After that, the mixed solution in the reaction vessel was cooled to 28 ºC or lower, and then toner particles were collected by filtration and a toner of Example 1 was obtained after drying.

Process 9: preparation of other example toners

Toners of Test Example 2 to Test Example 7 were prepared with a process similar to Process 8, while using the afore-mentioned 2nd to 7th test wax dispersions, respectively, instead of the 1st test wax dispersant. Further, toners of Comparative Test Examples 8 to 10 were prepared with a process similar to Process 8, while using the afore-mentioned 8th to 10th test wax dispersions instead of the1st test wax dispersant.

Test evaluation

Each of the example toners prepared as described above was analyzed with a differential scanning calorimeter. The results are shown in Table 2. Table 2 also shows the contents of iron element (Fe), silicon element (Si), and sulfur element (S) in the toners (by fluorescent X-ray analysis) and the amounts of components with a molecular weight of 1000 or less in a tetrahydrofuran-soluble portion of the waxes (by gel permeation chromatography).

The differential scanning calorimeter used was DSC Q2000 available from TA Instruments. During measurements with the differential scanning calorimeter, the temperature was raised at 10 ºC per minutes from 30 ºC to 140 ºC, then also lowered at 10 ºC per minute to 0 ºC, and further thereafter again raised at 10 ºC per minute to 140 ºC. The samples were made uniform to 10 mg ± 1 mg.

Values during temperature-rising were measured in a second temperature-rising after performing a temperature-rising and a following temperature-lowering, so as to avoid the effects of thermal history of the toners. Values during temperature-lowering were measured in the temperature-lowering following the first temperature-rising.

The evaluation items in Table 2 concerning the second temperature-rising and the temperature-lowering have a similar meaning as for the previously described examples. As shown in Table 2, the thermal characteristics of a toner may be set by selecting the thermal characteristics of a wax material to be used.

Table 2

The fixing property of each toner was evaluated in the following manner, with the use of an image forming apparatus.

The "Samsung CLP-610ND Color Laser Printer (printing speed: 21 pages/min)" operating on a single-component developing system was used as the image forming apparatus. As a transfer medium, "Fuji Xerox Full-Color copying paper J (82 g/cm ², A4 size)" was used.

The set temperature of the fixing device was changed to determine a minimum fixing temperature (MFT) and a hot-offset non-occurring temperature (HOT). The difference between MFT and HOT defines a fixing temperature range. Note that MFT is a minimum temperature at which fixing can be made, and the lower the more desirable. HOT is a maximum temperature at which hot-offset does not occur, and the higher the more desirable. As the fixing temperature range is the difference between MFT and HOT and thus the broader the more desirable.

Further, a writing property was measured by printing an image on the transfer medium, with the fixing temperature set at an intermediate temperature between MFT and HOT, and the density of a line was evaluated according to the following criteria after drawing a 2 cm line under a load of 500 gf, using a Mitsubishi Pencil Hi-Uni (HB). The evaluation scores are identified as follows: A for dense (good), B for slightly thin, C for rather thin (acceptable for practical purposes), D for thin, E for slipping and hard to write on. The results of evaluation are shown in Table 3.

Table 3

Results of evaluation

As shown in Table 3, the Test Examples 1 to 7 had MFTs in a range of 117 ºC to 140 ºC, which are lower than MFTs of Comparative Test Examples 1 to 3 which were in a range of 141 ºC to 151 ºC.

Further, the Test Examples 1 to 7 had HOTs in a range of 170 ºC to 190 ºC, which are generally higher than HOTs of Comparative Test Examples 1 to 3 since HOTs of Comparative Test Examples 1 and 2 were 165 ºC and 172 ºC. The HOT of Comparative Test Example 3 was 214 ºC and thus was the highest among the Test Examples and Comparative Test Examples In addition, the MFT Comparative Test Example 3 was also highest at 151 ºC. Further, Comparative Test Example 3 was evaluated as D in terms of the writing property.

Test Example 7 was attributed C in terms of the writing property and, even though this may correspond to an acceptable level from a practical point of view, it is inferior among the Test Examples 1 to 7. Further, the HOT was 170 ºC and was lower than 172 ºC of Comparative Test Example 2. However, the MFT was 117 ºC, the lowest of Test Examples 1 t o7.

The MFT of Test Example 5 was 140 ºC, the highest among the Test Examples 1 to 7, and only differs by 1 ºC from 141 ºC of Comparative Test Example 1, which is the lowest MFT among the Comparative Test Examples. However, the HOT of Test Example 5 was 190 ºC, the highest among the Test Examples 1 to 7, and thus is significantly different from 165 ºC of Comparative Test Example 1.

Regarding Test Examples 1 to 4 and 6, the MFTs and the HOTs are both greater than Comparative Test Examples 1 and 2. The fixing temperature ranges of Test Examples 1 to 7 vary from 50 ºC to 60 ºC, which is about twice the ranges of Comparative Test Examples 1 and 2, at 24 ºC and 28 ºC, respectively. The fixing temperature range of Comparative Test Example 3 is as broad as 63 ºC, but it is inferior in terms of the writing property, as indicated above.

The writing property of Test Examples 1 to 6 were either A or B, which are relatively good. The writing properties of Comparative Test Examples 1 and 2 are A or B, however the MFTs and HOTs are poorer than those of the Test Examples 1 to 7, as indicated above.

As discussed above, the results of Test Examples 1 to 7 are more satisfactory than the results of Comparative Test Examples 1 to 3, in terms of overall evaluation of MFT, HOT and writing property.

The electrostatic charge image developing toner disclosed herein may be used in electrophotography, as it can achieve a writing property with a writing tool and a more constant (or more uniform) feel to the touch, while maintaining a low-temperature fixing property and a hot-offset resistance property.

It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail.

Claims

An electrostatic charge image developing toner comprising a binder resin, including an amorphous resin and a crystalline resin, a colorant, and a wax, wherein the toner is characterized by a temperature-rising curve measurable with a differential scanning calorimeter, and wherein in the temperature-rising curve:

a melting point MP ₂ of the wax is no less than 70.0 ºC and no more than 83.0　ºC;

a rate of change in the heat flow dHF ₂₁/dT between a temperature T ₂₁, which is lower than MP ₂ and at which a heat flow is lower than the heat flow at 60.0 ºC by 0.5 mW, and a temperature T ₂₂, which is lower than MP ₂ by 2 ºC, is no less than -0.50 mW/ºC and no more than -0.10 mW/ºC; and

a rate of change in the heat flow dHF ₂₂/dT between a temperature T ₂₃, which is higher than MP ₂ by 1 ºC, and a temperature T ₂₄, which is higher than MP ₂ and at which a heat flow is lower than the heat flow at 60.0 ºC by 0.5 mW, is no less than 0.50 mW/ºC and no more than 1.80 mW/ºC.
The electrostatic charge image developing toner according to claim 1, wherein,

the temperature-rising curve measured with the differential scanning calorimeter is a curve measured after removing the effects of thermal history of the electrostatic charge image developing toner by performing a temperature-rising and a following temperature-lowering at least once.
The electrostatic charge image developing toner according to claim 1, wherein,

the temperature-rising curve is associated with a second temperature rising following a first temperature rising, and

wherein in a temperature-lowering curve measured with the differential scanning calorimeter and associated with a temperature lowering performed between the first temperature-rising and the second temperature-rising:

a melting point MP _d is no less than 70.0 ºC and no more than 80.0 ºC;

a rate of change in heat flow dHF _d1/dT between 60.0 ºC and 65.0 ºC is no less than 0.20 mW/ºC and no more than 0.50 mW/ºC; and

a rate of change in heat flow dHF _d2/dT between a temperature Td ₃, which is higher than MP _d by 2 ºC, and a temperature T _d4, which is higher than MP _d by 3 ºC, is no less than -5.00 mW/ºC and no more than -0.30 mW/ºC.
The electrostatic charge image developing toner according to claim 1, further comprising an iron element, a silicon element and a sulfur element.
The electrostatic charge image developing toner according to claim 4, wherein:

a content of the iron element is no less than 1.0 Х 10 ³ ppm and no more than 1.0 Х 10 ⁴ ppm;

a content of the silicon element is no less than 1.0 Х 10 ³ ppm and no more than 5.0 Х 10 ⁴ ppm; and

a content of the sulfur element is no less than 5.0 Х 10 ² ppm and no more than 3.0 Х 10 ³ ppm.
The electrostatic charge image developing toner according to claim 1, wherein,

the wax comprises a tetrahydrofuran-soluble portion having between 0.2 % and 0.4 %, inclusive, of components with a molecular weight of 1000 or less, according to gel permeation chromatography.
An electrostatic charge image developing toner comprising:

a binder resin, including an amorphous resin and a crystalline resin;

a colorant; and

a wax,

wherein the electrostatic charge image developing toner is characterized by a temperature-rising curve measurable with a differential scanning calorimeter, and the temperature-rising curve represents a heat flow as a function of a temperature of the electrostatic charge image developing toner, and wherein in the temperature-rising curve:

a melting point MP ₂ of the wax is between 70.0 ºC and 83.0 ºC, inclusive;

a negative rate of change in heat flow dHF ₂₁/dT defined between a temperature T ₂₁ and a temperature T ₂₂, is between -0.50 mW/ºC and -0.10 mW/ºC, inclusive, wherein T ₂₁ and T ₂₂ are lower than MP ₂; and

a positive rate of change in heat flow dHF ₂₂/dT defined between a temperature T ₂₃, and a temperature T ₂₄, is between 0.50 mW/ºC and 1.80 mW/ºC, inclusive, wherein T ₂₃ and T ₂₄ are higher than MP ₂.
The electrostatic charge image developing toner according to claim 7, wherein

T ₂₁is associated with a heat flow value lower by 0.5 mW, relative to a heat flow value at 60.0 ºC,

T ₂₂ is lower than MP ₂ by 2 ºC,

T ₂₃ is higher than MP ₂ by 1 ºC, and

T ₂₄ is associated with a heat flow value lower by 0.5 mW, relative to the heat flow at 60.0 ºC.
The electrostatic charge image developing toner according to claim 7, wherein,

the temperature-rising curve measured with the differential scanning calorimeter is a curve measurable in a second temperature rising of the electrostatic charge image developing toner, second temperature rising following a first temperature rising and a temperature lowering of the electrostatic charge image developing toner.
The electrostatic charge image developing toner according to claim 7, wherein the temperature-rising curve is associated with a temperature rising preceded by a temperature lowering, and wherein

the temperature lowering is associated with a temperature-lowering curve wherein:

a melting point MP _d of the wax is between 70.0 ºC and 80.0 ºC, inclusive;

a positive rate of change in heat flow dHF _d1/dT between 60.0 ºC and 65.0 ºC, is between 0.20 mW/ºC and 0.50 mW/ºC, inclusive; and

a negative rate of change in heat flow dHF _d2/dT between a temperature Td ₃, which is higher than MP _d by 2 ºC, and a temperature T _d4, which is higher than MP _d by 3 ºC, is between -5.00 mW/ºC and -0.30 mW/ºC, inclusive.
The electrostatic charge image developing toner according to claim 7, further comprising an iron element, a silicon element and a sulfur element.
The electrostatic charge image developing toner according to claim 11, wherein

a content of the iron element is between 1.0 Х 10 ³ ppm and 1.0 Х 10 ⁴ ppm, inclusive;

a content of the silicon element is between 1.0 Х 10 ³ ppm and 5.0 Х 10 ⁴ ppm, inclusive; and

a content of the sulfur element is between 5.0 Х 10 ² ppm and 3.0 Х 10 ³ ppm, inclusive.
The electrostatic charge image developing toner according to claim 7, wherein,

the wax comprises a tetrahydrofuran-soluble portion having between 0.2 % and 0.4 %, inclusive, of components with a molecular weight of 1000 or less according to gel permeation chromatography.