JPH0311365A - Electrostatic charge image developer - Google Patents

Abstract

PURPOSE:To improve the rising characteristic and distribution characteristic of electrostatic charges by using a polyester resin which is formed by bringing a specific diol component and polyvalent carboxylic acid into cocondensation polymn. and which has a specific relation between the acid value and hydroxyl group value as a binder. CONSTITUTION:The resin which is the polyester resin formed by bringing the diol component expressed by formula I and at least one kind of bivalent carboxylic acid, the acid anhydride thereof or the lower alkyl ester thereof and at least one kind of tervalent or higher valency carboxylic acid, the acid anhydride thereof or the lower alkyl ester thereof or/and terhydric or higher hydric alcohol into the cocondensation polymn. and satisfies formula II is used as the binder. In the formula, OR<1>, OR<2> denote an oxyethylene group or oxypropylene group; x, y denote >=1 integer; the average value of x+y denotes 2 to 7. In the formula II, Av denotes the acid value of the polyester resin; OHv denotes the hydroxyl group value; Av is in a 20 to 35 KOHmg/g range. The rising characteristic and distribution characteristic of the electrostatic charges are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a developer used for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc. of copying machines, laser printers, etc. The electrophotographic method has been widely known for a long time.

For example, a visible image is formed through the following steps.

■ The photoconductive insulating layer is uniformly charged by corona discharge, etc., and then light is selectively irradiated by image exposure or laser beam scanning exposure, and the charge on the irradiated area is dissipated to form an electrostatic latent image. .

■ This latent image is visualized using a developer called toner to form a visible image (development process).

■ A visible image is transferred directly or onto another substrate such as paper (transfer process) and then fixed (fixing process).

Also known is a method in which electrostatic latent image vessels are formed by selectively charging with a bottle electrode.

In either case, the developer is required to have strict characteristics because it has a great influence on the success or failure of the development process, transfer process, and fixing process, and in turn determines image characteristics, running costs, etc. of the device.

Developers can be broadly classified into two component developers, which consist of toner and carrier, and one-component developers, in which the toner itself functions as a carrier. It is broadly divided into a regular development method in which the toner is attached to the latent image bearing part of the photoreceptor, and a reversal development method in which the toner is attached to the non-latent image bearing surface, but in both cases there is a method for controlling the charging characteristics of the developer. is an important issue.

Polyester resins are attracting attention as binder resins for such toners. For example, Tokuko Sho 63-437
No. 43 reports that stable images with less fog can be formed by using a negatively charged electromagnetic toner containing magnetic fine particles in a polyester resin having an acid value of 5 to 60. However, just adjusting the acid value does not provide sufficient charging characteristics. The rise characteristics of the IF charge and the distribution characteristics of the charge are poor.

If the charging start-up characteristics are poor, it will take a long time and agitation to stabilize, making it difficult to design a compact developing device, and contaminating the inside of the machine due to toner scattering. On the other hand, if the charge distribution characteristics are poor, the life of the developer will be shortened due to the generation of spent toner, and fogging will occur on the image, making it difficult to stabilize the image quality.

JP 63-68848, JP 63-68849, JP 63-68850, JP 63-68851
The publication describes an electrophotographic developer using a polyester resin containing the diol component of the present invention and having an OHv (hydroxyl value)/AV (acid value) of 1.2 or more (AV/○Hv of 0.83 or less). It has been reported that by using toner, offset can be prevented and fixing can be performed at low temperatures, and furthermore, toner fluidity can be improved and blocking characteristics can be improved. In addition, each of the above-mentioned publications states that if the acid value is too low, the amount of triboelectricity of the polyester resin will decrease, and on the other hand, if the acid value is too high, the environmental stability of the toner will be impaired.
It is stated that polyester resins ranging from 1 to 60 have been used conventionally.

However, the inventions described in these publications do not pay attention to the method of controlling the charging of toner, and in fact, A v
/ A toner using a polyester resin with an OHv of 0.83 or less as a binder does not have sufficient charge rise characteristics and distribution characteristics.

If these charging characteristics are poor, not only will the design of the compact device be compromised as described above, but it will also cause toner scattering, generation of spent toner, and unstable image quality.

In addition, regarding the improvement of the fixing characteristics of toner using polyester resin, Japanese Patent Publication No. 11902/1982 and No. 6
It is described in JP-A-1-59333, JP-A-63-225245, and JP-A-63-225246.

The present invention is intended to provide an electrostatic image developer with improved charge rise characteristics and distribution characteristics.

11 houses and 1 belly of light The electrostatic image developer of the present invention is:

(a) a diol component represented by the following general formula (r); (b) at least one divalent carboxylic acid, its acid anhydride, or its lower alkyl ester; (C) a trivalent or higher polyvalent At least one carboxylic acid, its acid anhydride or its lower alkyl ester, or/
and a polyester resin obtained by cocondensation polymerization with a trihydric or higher polyhydric alcohol, where Av10Hv=1.0-1. The present invention is characterized in that a polyester resin having an AV of 20 to 35 (K OHmg/g) is used as a binder.

(The symbols in the formula indicate the following: OR", OR" nioxyethylene group or oxypropylene group. Explain.

The polyester resin used in the present invention is composed of (a) a specific diol component, in which 2 to 7 moles of ethylene oxide or propylene oxide are added on average to bis(4-hydroxyphenyl)propane, (b) divalent carboxylic acids, (
C) Obtained by cocondensation polymerization with trihydric or higher carboxylic acids and/or trivalent or higher alcohols.

(a) Specific examples of the diol component of general formula (I) include:
Polyoxypropylene (2,2)-2,2-bis(4-
hydroxyphenyl)propane, polyoxypropylene (3,3)-2,2bis(4-hydroxyphenyl)propane, polyoxyethylene(2,0)-2,2-bis(4-hydroxyphenyl)propane, polyoxy Propylene (2,0)-polyoxyethylene (2,0)-2
Examples include 2-bis(4-hydroxyphenyl)propane and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane.

Further, other dihydric alcohol components can also be used in combination within a range that does not impair the effects of the present invention.

Examples of the dihydric alcohol component include the following.

1) Diols; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1°3-propylene glycol, 1,4-
Butanediol, neopentyl glycol, 1,4-butynediol, 1,5-bentanediol, 1,6-hexanediol, 1,4-cyclohexane dimetatool, dipropylene glycol, polyethylene glycol,
Polypropylene glycol, polytetramethylene glycol, etc.

2) Bisphenols; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylated bisphenol A, and polyoxypropylenated bisphenol A (excluding those within the scope of the present invention).

(b) As divalent carboxylic acids, divalent carboxylic acids,
This acid anhydride or this lower alkyl ester is used.

Examples of dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sepatic acid, azelaic acid, malonic acid, Or n-butylsuccinic acid, n-butenylsuccinic acid, inbutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid, n-octenylsuccinic acid,
Examples include alkyl or alkenyl succinic acids such as n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid, and isododecenylsuccinic acid.

Among the components (c), the carboxylic acid having 5 or more valences is l
, 2,4-benzenetricarboxylic acid (trimellitic acid)
, 1,2.5-benzenetricarboxylic acid, 2,5.7-
naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, l
.

2.5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,
1,2,4-cyclohexanetricarboxylic acid, tetra(
Examples include (methylenecarboxyl)methane, 1,2,7.8-octane tetracarboxylic acid, pyromellitic acid, and Empol trimer acid. These acid anhydrides or lower alkyl esters can also be used.

Among the components (e), trihydric or higher alcohols include:
Sorbitol, 1,2,3.6-hexantetrol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2.
4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3. 5-trihydroxymethylbenzene and the like are used.

By cocondensation polymerization using trivalent or higher carboxylic acids and/or trivalent or higher alcohol (phenol) as part of the cocondensation polymerization component.

A portion of the polyester resin is crosslinked. The degree of crosslinking can be expressed as ethyl acetate-insoluble content or chloroform-insoluble content as described in JP-A-63-68848. Aromatic carboxylic acid and aliphatic carboxylic acid (alkyl or alkenyl succinic acid) are used together as acids to obtain a resin with a chloroform insoluble content of 25%.

In the polyester resin of the present invention, the ratio Av10HV of acid value (Av) to hydroxyl value (○HV) is 1.0 to 1.
5, preferably 1.1 to 1.4, which improves charging rise characteristics and distribution characteristics. As a result, the toner is sufficiently charged in a short stirring time, the developing device can be downsized, and the toner is prevented from scattering inside the machine. Furthermore, since the generation of toner that is charged to the opposite polarity can be suppressed, fogging can be prevented and stable image quality can be obtained, making it particularly suitable as a toner for reversal development. Furthermore, generation of toner that is strongly charged exceeding a set value is prevented. When such toner is generated, it strongly adheres to the carrier, resulting in spent toner.

The life of the developer will be shortened.

If the Av/OHv ratio is less than 1.0, the above effects cannot be sufficiently obtained; on the other hand, if this ratio is less than 1.0,
If it exceeds 5, it will be difficult to control one reaction, making it impossible to obtain a polyester resin with stable performance as a binder for toner.

Furthermore, the polyester resin of the present invention has an AV of 20 to 3.
5 (K OHag/g), preferably 20 to 30. If the AV is less than 20, the advantage of the negative charging property of the polyester resin of the present invention cannot be fully exploited. On the other hand, if the AV exceeds 35, the Q/M will be strongly affected by humidity, especially in high humidity. (charge amount per unit weight) increases, and there is a strong tendency for image density to decrease.

The acid value and hydroxyl value of polyester resin are JISK 00
It is measured according to the method specified in 70.

AV/OHV ratio in polyester resin, AV
The value can be adjusted by using more of the carboxylic acid components in terms of the number of functional groups than the entire -〇H components in the cocondensation polymerization reaction, and because the number of terminal functional groups decreases as the cocondensation polymerization progresses. This can be done by adjusting the degree.

Polyester resins are produced by known cocondensation polymerization reactions, such as those described in the above-mentioned published patent publications.

By adding conventionally known coloring agents, charge control agents, anti-offset agents, etc. to the polyester resin of the present invention to form a toner with a desired particle size, and mixing this with a carrier, dry secondary processing is performed. It can be a component developer. Also.

By adding magnetic particles into the toner.

It can be a component-based magnetic developer.

Examples of the coloring agent include various carbon blacks, phthalocyanine blue, rhodamine, benzidine yellow, and the like.

As the charge control agent, nigrosine dyes, triphenylmethane dyes, metal-containing azo dyes, copper phthalocyanine dyes, etc. are used.

As the offset inhibitor, paraffin wax, low molecular weight polyolefin, etc. are used.

As the carrier, an iron oxide carrier, a ferrite carrier, or the like is used.

- In the case of component-based magnetic toner, iron, cobalt,
Ferromagnetic powders such as nickel and ferrite are added.

Moreover, external additives such as hydrophobic silica can also be added.

According to the present invention, a specific diol component and a polyhydric carboxylic acid are co-condensed, and AV10HV=1.0 to 1.5.
By using a polyester resin having an AV of 20 to 35 as a binder to form an electrostatic image developer, charging rise characteristics and distribution characteristics can be improved. Therefore, the toner is sufficiently charged in a short stirring time, making it possible to downsize the developing device and, by extension, the entire device. Further, it is possible to prevent internal contamination due to toner scattering and the generation of spent toner, and furthermore, it is possible to prevent fogging and obtain stable image quality.

10 parts by weight of bisphenol A polyoxyethylene adduct of general formula (I) (average number of moles added 2.2), 5 parts by weight of terephthalic acid, 3 parts by weight of alkenylsuccinic acid, 2 parts by weight of trimellitic anhydride A polyester resin having the following properties was produced by cocondensation polymerization of the following parts.

Acid value Av=28.0 (KOH-g/g) Hydroxyl value OHv
=22.0(KOHug/g)AV10HV=1.2
7 Softening point = 128°C Glass transition point Tg: 60°C Chloroform insoluble content = 25% Here, the acid value and hydroxyl value are JIS K 0070
Measured according to. However, for the acid value, dioxane was used as the solvent, and for the hydroxyl value, the acetylation time was 2 hours.

In addition, the softening point was determined as the temperature at which half of the sample flowed out using a flow tester.

Using this polyester resin, the following composition was measured and mixed.

Polyester resin 85% by weight Polypropylene wax 550P 5% by weight Carbon black (Regal 400R) g% by weight Charge control agent (Bondron S-34) 1% by weight After cross-mixing, this mixture is pulverized to a size of 5 to 25 μm using a jet mill to form a toner. I got it.

Next, 1000 g of silicone-coated ferrite carrier having an average particle size of 70 μm and 40 g of the above toner were mixed in a Nauta mixer to produce a two-component developer.

Various AV values were obtained by repeating the same operation as above except for changing the ratio of diol component, divalent carboxylic acid, trivalent carboxylic acid, and carboxylic acid component.

A two-component developer using a polyester resin having an Av10Hv ratio as a toner binder was manufactured.

Regarding each of these developers, toner scattering, fogging,
Spent (Table 1) and rise characteristics (Figure 1) were evaluated. The evaluation methods and results are as follows.

(I) Toner scattering inside the machine Using a laser printer F-800 manufactured by Kyocera ■, 10
After printing 10,000 copies, they were inspected visually and the in-machine scattering was evaluated using the following criteria, and the results are shown in Table 1 below.

l-determined standard O: No scattering at all 0: Good scattering Δ: Slight scattering ×: Large scattering Table-1: Evaluation of toner scattering inside the machine It can be seen that the in-flight scattering has been improved.

(2) Fogging Fog was determined using a limit sample.

O: No fog is observed at all Q: Fog cannot be detected with the naked eye Δ: Fog is visible with the naked eye Based on the quantitative determination of carbon content! Constant standard O: No increase in carbon content, no image change 0: Slight increase in carbon content, no image change Δ: Increase in carbon content, slight image deterioration ×: Large increase in carbon content, image deterioration (4) The developer is stirred with a rocking mixer and Q/M (μC/g
) was measured by the blow-off method, and the results are shown in FIG. Note that symbols 1 to 4 in Figure 1 correspond to ■ to ■ in Table-1 above.
corresponds to

By setting the Ay value and the A v / OHv ratio within the range of the present invention, the charge amount rises sharply with a small number of stirrings,
It turns out that it is stable at an appropriate level.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the number of times of stirring and Q/M (μC/g), and represents the rising charging characteristics of the developer6.

Claims (1)

[Claims] 1. (a) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... (I) (The symbols in the formula indicate the following: OR^1, OR^2 : oxyethylene group or oxypropylene group at least one alkyl ester; (c) at least one trivalent or higher polyhydric carboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof; or/
and a polyester resin obtained by cocondensation polymerization with a trihydric or higher polyhydric alcohol, where A_v/OH_v=1.0-1. 5, and A_v is 20 to 35 (KOHmg/g
) An electrostatic image developer characterized by using a polyester resin falling within the range of (1) as a binder.