JPH0424703B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrostatic image developing toner used for developing electrostatic images formed in electrophotography, electrostatic printing, electrostatic recording, etc. It is related to.

[Technical background of the invention]

For example, in electrophotography, an electrostatic latent image is usually formed by charging and exposing a latent image carrier made of a photoconductive photoreceptor, and then this electrostatic latent image is placed in a binder made of resin with a coloring agent, etc. The resulting toner image is transferred to a support such as transfer paper and fixed to form a visible image.

In order to obtain a visible image as described above, it is necessary to fix the toner image, and conventionally, a heat roller fixing method that has high thermal efficiency and can perform high-speed fixing has been widely adopted.

However, in recent years, there has been a strong demand from various viewpoints to perform the fixing process at high speed while keeping the temperature of the heat roller lower, and there is a need for toner that fully satisfies these demands. It is being

In addition, toner must be able to exist stably as a powder without agglomerating under the environmental conditions of use or storage, that is, it must have excellent blocking resistance. The problem with toner is that it is easy to cause an offset phenomenon, that is, a part of the toner that makes up the image is transferred to the surface of the heat roller during fixing, and this is transferred again to the transfer paper that is sent next, staining the image. It is necessary to provide the performance to prevent the occurrence of offset phenomenon, that is, to provide non-offset property.

[Conventional technology]

Conventionally, as disclosed in JP-A-50-87032, for example, a polymer formed by chemically linking a crystalline polymer with a low melting point and an amorphous polymer has been used as a binder constituting a toner. Techniques for use have been proposed.

[Problem that the invention seeks to solve]

However, in such technology, 100℃
Although it is possible to perform the fixing process at low temperatures before and after the fixing process, there is a drawback that an offset phenomenon occurs. On the other hand, in order to prevent the occurrence of the offset phenomenon, (1) means to increase the molecular weight of the polymer, (2) means to increase the dynamic elastic modulus of the crystalline polymer, and (3) means to increase the dynamic elastic modulus of the amorphous polymer. Possible methods include raising the glass transition point, but since the above method (1) results in poor pulverization properties, methods that include a normal pulverization step may require pulverization to the particle size required for the toner. It is difficult to increase the dynamic modulus of elasticity at temperatures above the melting point of the crystalline polymer using the method (2) above, and it is difficult to prevent the offset phenomenon from occurring using the method (3) above. However, there is a problem in that fixing performance deteriorates due to the high glass transition point.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide a film that has excellent anti-blocking properties and high storage stability, as well as excellent low-temperature fixing properties and non-offset properties, and to prevent the occurrence of offset phenomena. An object of the present invention is to provide a toner for electrostatic image development that can form an image at a lower temperature without being accompanied by.

Another object of the present invention is to provide a toner for electrostatic image development that is easy to crush and can be easily obtained into small-diameter toner particles through a normal crushing process.

[Means for solving problems]

The electrostatic image developing toner of the present invention has a melting point of 45 to
10 for total isocyanate with crystalline aliphatic polyester at 150°C and difunctional isocyanate.
It contains as a binder a resin obtained by chemically bonding ~40 mol% of trifunctional isocyanate, and the resin has a dynamic elastic modulus of 1.0×10 ⁴ dyn/cm ² or more at a temperature of 100°C. , melt viscosity at 100°C is 5.0× ¹⁰⁴ poise or less, weight average molecular weight Mw is 5000 to 100000, and number average molecular weight
Characterized by Mn of 2000 to 50000.

[Effect]

According to this configuration, the resin constituting the binder chemically combines a crystalline polymer made of a specific crystalline aliphatic polyester and a coupling agent made of a bifunctional isocyanate and a specific proportion of a trifunctional isocyanate. Since this resin is obtained by bonding, the crystalline polymer is linearly linked by a difunctional coupling agent made of a difunctional isocyanate, and is also linearly linked by a trifunctional coupling agent made of a trifunctional isocyanate. It becomes crosslinked. Therefore, during fixing, when the toner is heated to a temperature higher than the melting point of the crystalline polymer and the crystalline polymer portion melts, the toner particles remain in a highly fluid state within the particles but have a crosslinked structure due to the trifunctional isocyanate. This allows the toner particles to maintain their particle form, and as a result, the toner particles do not flow suddenly and a state of high elasticity is obtained.As a result, the transfer of the toner to the fixing roller is suppressed, and the toner is kept at a low temperature. It becomes established.

Since the transfer of toner to the fixing roller is inhibited in this way, it is no longer necessary to increase the molecular weight of the crystalline polymer in order to prevent the occurrence of the offset phenomenon. In the process, pulverization becomes easier.

Crystalline polymers exhibit almost no tackiness at temperatures below their melting point, and toner particles that reflect this property also have excellent blocking resistance.

The present invention will be explained in detail below.

In the present invention, a crystalline aliphatic polyester having a melting point of 45 to 150°C, a difunctional isocyanate, and a trifunctional isocyanate in an amount of 10 to 40 mol% based on the total isocyanate are chemically bonded. , a resin with specific physical properties is used as a binder.

As a crystalline polymer, its melting point is 45-150
℃ crystalline aliphatic polyester is used,
If a toner with a melting point of less than 45° C. is used, the toner particles tend to aggregate, resulting in decreased blocking resistance, while if a melting point of more than 150° C. is used, low-temperature fixing becomes difficult.

In the resin used as the binder, the proportion of the crystalline polymer is about 75 to 95% by weight. Further, the binder may contain a crystalline polymer and/or an amorphous polymer in addition to the resin. As such an amorphous polymer, polyester, styrene-acrylic polymer, etc., which are incompatible with the resin, can be preferably used, and the usage ratio is 0 to 50% by weight, preferably 5% by weight.
~40% by weight.

Further, the resin has a dynamic elastic modulus of 1.0×10 ⁴ dyn/cm ² or more at a temperature of 100°C and a melt viscosity of 5.0×10 ⁴ poise or less at a temperature of 100°C.

In addition, the weight average molecular weight Mw of the resin is 5000~
100000, particularly preferably within the range of 10000 to 50000, and the number average molecular weight Mn of the resin is
It is preferably in the range of 2,000 to 50,000, particularly 3,000 to 15,000. When the weight average molecular weight Mw of the resin is too large, pulverization tends to be difficult in the pulverization step in the toner manufacturing process.

The melting point of the crystalline polymer and the dynamic elastic modulus of the resin in the above can be measured as follows.

<Measurement of melting point of crystalline polymer> According to differential scanning calorimetry (DSC), several mg of the crystalline polymer to be combined with the coupling agent is heated at a constant heating rate (10℃/
The melting point is defined as the melting peak value when heated at (min).

<Measurement of dynamic elastic modulus of resin> A resin sample used as a binder is melted at a certain temperature, a sine wave vibration is applied to the sample in the molten state, and the dynamic elastic modulus is measured from the torsion amplitude ratio and phase difference. obtain.

As mentioned above, the crystalline polymer used in the present invention is a crystalline aliphatic polyester having a melting point within the range of 45 to 150°C, and has a reactive group at its end that can be chemically bonded to a coupling agent. It has a hydroxyl group and/or a carboxyl group.

This crystalline polymer has a weight average molecular weight of
Mw is 3000-50000 and the number average molecular weight Mn is 1000
It is preferably within the range of ~20,000. When using a crystalline polymer having a molecular weight too large or too small, pulverization tends to be difficult in the pulverizing step in the toner manufacturing process.

Specific substances of the crystalline aliphatic polyester include, for example, polydecamethylene adipate, polydecamethylene azelate, polydecamethylene oxalate, polydecamethylene sebacate, polydecamethylene succinate, polyethylene sebacate, and polyethylene suberate. , polyethylene succinate, polyhexamethylene sebacate, polyhexamethylene suberate, polyhexamethylene oxalate, polyhexamethylene succinate, poly-10-hydroxycaprylic acid, poly-6
-hydroxycaproic acid, poly-3-hydroxypropionic acid, and the like.

In the present invention, difunctional isocyanates and 10 to 40 mol % of trifunctional isocyanates, based on the total isocyanates, are used as coupling agents. When the ratio of trifunctional isocyanate to the total isocyanate exceeds 40 mol%, gelation of the resin may occur, pulverization becomes difficult in the pulverization process in the toner manufacturing process, and the melt viscosity of the toner at low temperatures becomes high. This may make low-temperature fixing difficult. On the other hand, if the proportion of trifunctional isocyanate is too small, it is likely to be difficult to obtain the elastic modulus required to prevent the offset phenomenon.

Specific examples of such coupling agents include the following.

(1) Difunctional isocyanate hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, tolidine diisocyanate, naphthylene diisocyanate, isophorone diisocyanate,
Xylylene diisocyanate.

(2) Trifunctional isocyanate triphenylmethane triisocyanate, 1,
3,6-hexamethylene triisocyanate,
1,6,11-undecane triisocyanate, tris(isocyanate phenyl) thiophosphate.

The electrostatic image developing toner of the present invention contains a colorant and optional additives in a binder made of the above-mentioned specific resin.

Coloring agents include carbon black, nigrosine dye (CI No. 50415B), and aniline blue (CI No.
50405), Calco Oil Blue (CINo.azoec
Blue3), Chrome Yellow (CINo.14090), Ultramarine Blue (CINo.77103), DuPont Oil Red (CINo.26105), Quinoline Yellow (CI
No.47005), methylene blue chloride (CINo.
52015), Phthalocyanine Blue (CINo.74160),
Malachite Green Oxalate (CINo.
42000), lampblack (CI No. 77266), rose bengal (CI No. 45435), mixtures thereof, and others. These colorants need to be contained in a sufficient proportion to form a visible image of sufficient density, and are usually about 1 to 20 parts by weight per 100 parts by weight of the binder.

Examples of additives that may be added as necessary include a charge control agent, a lubricant for improving fluidity, and others.

〔Example〕

Examples of the present invention will be described in detail below, but the present invention is not limited to these Examples.

Example 1 [Production of resin constituting binder] Structural formula [A] A crystalline polymer consisting of polyhexamethylene sebacate represented by the above structural formula [A] (melting point: 66
°C, dynamic elastic modulus: 1.8 × 10 dyn/cm ² (100 °C), melt viscosity: 2.2 × 10 poise (100 °C), weight average molecular weight
Mw: 14800, number average molecular weight Mn: 6460, OH value:
22.5) and xylene in a reaction vessel by stirring and mixing.
Heated to 140°C. After reflux, in the reaction system,
Hexamethylene diisocyanate whose number of moles corresponds to 25% of the total number of moles of OH groups in the above polyhexamethylene sebacate, and trifunctional isocyanate "Desmodyur R" whose number of moles also corresponds to 5%.
(manufactured by Bayer) dissolved in a chloroform solution was added and reacted at 140°C for 1 hour.
The solvent was distilled off under reduced pressure, and the crystalline polymer polyhexamethylene sebacate, the difunctional coupling agent hexamethylene diisocyanate, and the trifunctional coupling agent "Desmodyur R" were chemically bonded. A resin was obtained.
This will be referred to as "Resin 1".

The weight average molecular weight Mw of this resin 1 is 31800, the number average molecular weight Mn is 8910, and the dynamic elastic modulus is 3.2×
10 ⁴ dyn/cm ² (100°C), melt viscosity was 4.5×10 ⁴ poise (100°C), and melting point was 64°C.

Although the structure of this resin 1 is not precisely known,
It is thought that in the following structural formula, [B] partially becomes [B'], resulting in a crosslinked structure.

-[[A]-[B]-] _o (wherein, [A] is the structural formula [A] in Example 1)
[B] represents the same thing as represents, and [B′] is represents. ) 100 parts by weight of the above Resin 1 and 10 parts by weight of carbon black "Mogull L" (manufactured by Kayabot Corporation) were mixed, pre-dispersed, kneaded with heated rolls, cooled and pulverized to give an average particle size of approx. An 11 μm toner was produced. This is referred to as "toner 1".

The dynamic elastic modulus of this toner 1 is 2.5×10 ⁵ dyn/cm ²
(100°C), and the melt viscosity was 3.1×10 ⁵ poise (100°C).

2 parts by weight of this toner 1 and an average particle size of 100 μm
A developer is prepared by mixing with 98 parts by weight of a resin-coated carrier of The resulting toner image was transferred onto transfer paper, and the temperature of the heating roller was adjusted.
A photocopying test was conducted in which a copy image was formed by fixing it using a heated roller fixing device set at 100°C.

In the obtained copied image, the toner fixability was good, and there was no image staining caused by the offset phenomenon. Further, the toner stored in the developing device did not aggregate and existed stably as a fine powder, and had excellent blocking resistance.

Example 2 In the same manner as in Example 1, polyhexamethylene sebacate and xylene were stirred and mixed in a reaction vessel to give 140%
heated to ℃. After reflux, the reaction system contains hexamethylene diisocyanate in a mole number corresponding to 20% of the total mole number of OH groups in the polyhexamethylene sebacate, and trifunctional isocyanate "Desmodyur R" in a mole number corresponding to 10%. " (manufactured by Bayer) dissolved in a chloroform solution was added, and the mixture was reacted at 140°C for 1 hour. The solvent was then distilled off under reduced pressure to form polyhexamethylene sebacate, which is a crystalline polymer. A resin was obtained in which hexamethylene diisocyanate, a bifunctional coupling agent, and "Desmodyur R", a trifunctional coupling agent, were chemically bonded. This will be referred to as "Resin 2".

The weight average molecular weight Mw of this resin 2 is 43400, the number average molecular weight Mn is 9820, and the dynamic elastic modulus is 8.1×
10 ⁴ dyn/cm ² (100°C), melt viscosity was 9.2×10 ⁴ poise (100°C), and melting point was 64°C.

A toner was produced in the same manner as in Example 1 using the above Resin 2. This will be referred to as "toner 2".

The dynamic elastic modulus of this toner 2 is 7.4×10 ⁵ dyn/cm ²
(100°C), and the melt viscosity was 6.6×10 ⁵ poise (100°C).

Using this toner 2, an actual photographic test was conducted in the same manner as in Example 1. Copied images obtained with the heating roller temperature set at 100°C had slightly poor toner fixing performance;
In the copy image obtained by setting the temperature to 130℃,
The fixing properties of the toner were good, and there was no image staining due to offset phenomenon. Further, the toner in the developing device did not aggregate and had excellent blocking resistance.

Comparative Example 1 [Manufacture of resin constituting the binder] Xylene was added to the same polyhexamethylene sebacate as used in Example 1, mixed by stirring in a reaction vessel, and heated to 140°C. After reflux, a xylene solution of hexamethylene diisocyanate was added in an amount corresponding to 30% of the number of moles of OH groups in the polyhexamethylene sebacate. After reacting at 140° C. for 1 hour, xylene was distilled off under reduced pressure to obtain a resin consisting of linked polyhexamethylene sebacate represented by the following structural formula. This is referred to as "Comparative Resin 1".

Although the structure of Comparative Resin 1 is not precisely known, it is thought to have the following structure without a crosslinked structure.

-[[A]-[B]-] _o (In the formula, [A] and [B] represent the same structural formulas [A] and [B] in Example 1.) Weight average molecular weight Mw is 26300,
Number average molecular weight Mn is 9870, dynamic elastic modulus is 5.4×
10 dyn/cm ² (100°C), melt viscosity was 1.1×10 ² poise (100°C), and melting point was 63.

A toner was produced in the same manner as in Example 1 using Comparative Resin 1. This is referred to as "comparison toner 1."

The dynamic elastic modulus of this comparison toner 1 is 3.3×
10 ² dyn/cm ² (100°C), and the melt viscosity was 5.6×10 ² poise (100°C).

Using this comparative toner 1, a developer was prepared in the same manner as in Example 1, and using this developer, Example 1
I conducted a live-action test in the same way.

In the obtained copied image, the toner fixability was good, but there was considerable image staining due to the offset phenomenon.

Comparative Example 2 [Manufacture of resin constituting the binder] Polyhexamethylene sebacate similar to that used in Example 1 and xylene were stirred and mixed in a reaction vessel and heated to 140°C. After reflux, all OH of the above polyhexamethylene sebacate is added to the reaction system.
Add a solution of hexamethylene diisocyanate in a mole number corresponding to 10% of the group mole number and trifunctional isocyanate "Desmodyur R" (manufactured by Bayer) in a mole number corresponding to 20% in a chloroform solution. When the mixture was reacted at 140°C, it became highly viscous in a short time and gelled to the point where the solvent could not be easily distilled off. It was impossible to manufacture toner using this resin.

〔Effect of the invention〕

As explained above, according to the toner for electrostatic image development of the present invention, the resin constituting the binder contains a crystalline polymer made of a specific crystalline aliphatic polyester, a difunctional isocyanate, and a total isocyanate. This resin is obtained by chemically bonding a coupling agent consisting of 10 to 40 mol% of a trifunctional isocyanate. At the same time, part of the crystalline polymer has a crosslinked structure with trifunctional isocyanate, and therefore, during fixing, the toner is heated to a temperature higher than the melting point of the crystalline polymer, and this crystalline polymer When the part melts, the toner particles are in a highly fluid state within the particles, but the cross-linked structure by the trifunctional isocyanate maintains the particle shape, so the fluidity of the toner particles suddenly decreases. A state of high elasticity is obtained without occurrence of the toner, and as a result, while low-temperature fixing is achieved, toner transfer to the fixing roller is suppressed, and an image can be formed without occurrence of an offset phenomenon. In this way, since the offset phenomenon can be prevented while using a crystalline polymer, it is not necessary to increase the molecular weight of the crystalline polymer in order to prevent the offset phenomenon, and therefore the toner manufacturing process can be improved. In the pulverization step, which is one of the steps, pulverization is easy and toner production is simple. Since the low tackiness below the melting point of the crystalline polymer is reflected, the toner particles have excellent blocking resistance, and as a result, the toner does not aggregate and can exist stably in a fine particle form, making it possible to preserve the toner. Good stability.

Claims (1)

[Claims] 1. A crystalline aliphatic polyester having a melting point of 45 to 150°C, a difunctional isocyanate, and a trifunctional isocyanate in an amount of 10 to 40 mol% based on the total isocyanate are chemically bonded. The resulting resin is contained as a binder, and the resin has a dynamic elastic modulus at a temperature of 100°C.
1.0×10 ⁴ dyn/cm ² or more, melt viscosity at 100°C 5.0×10 ⁴ poise or less, weight average molecular weight Mw
5000~100000, and number average molecular weight Mn is 2000~
50,000.