JPH08179669A - Cleaning blade for electrophotographic device - Google Patents

Abstract

PURPOSE: To provide a cleaning blade ensuring low-temp. characteristics and preventing permanent set and chatter at high temp. CONSTITUTION: In this cleaning blade consisting of a blade member made of polyurethane elastomer, a support member and an adhesive layer, the polyurethane elastomer consists of high mol.wt. polyol, an isocyanate compd. and a chain extending-crosslinking agent. The high mol.wt. polyol is polyethylene adipate. The chain extending-crosslinking agent consists of 1,4-butanediol, 1,6- hexanediol and trimethylolpropane. The ratio between the total number of the hydroxyl groups of the 1,4-butanediol and 1,6-hexanediol and the number of the hydroxyl groups of the trimethylolpropane is (85:15) to (60:40) and the ratio between the number of the hydroxyl groups of the 1,6-hexanediol and that of the 1,4-butanediol is (97:3) to (50:50).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning blade for an electrophotographic apparatus, which maintains a stable cleaning property over a wide temperature range for a long period of time.

[0002]

2. Description of the Related Art An electrophotographic apparatus has a photoconductor provided with a photoconductive layer on its surface. During operation, the outer peripheral surface of the photoconductor is uniformly charged, and then the object to be copied is covered. An electrostatic latent image is formed by exposing the outer peripheral surface through a copy image, toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to paper or the like and fixed. Is.

In this process, a part of the toner remains on the outer periphery of the photoconductor after the transfer, and it is necessary to remove this residual toner. Such toner removal is performed by a cleaning blade. As the cleaning blade, one having a structure in which a blade member made of an elastic body is joined to a support made of a metal plate is usually used.

The above-mentioned blade member has little wear and permanent distortion due to rubbing against a mating member such as a photoconductor, and pressure during bonding,
Polyurethane elastomers are usually used because they require properties such as small deformation of the adhesive due to solvent. The hardness of the blade member is preferably 65 to 80 degrees (JIS-A) because it does not damage the photoreceptor and requires an appropriate pressure contact force during cleaning.

In order to satisfy these characteristics, usually,
As the chain extender or cross-linking agent used for producing the polyurethane elastomer, bifunctional component 1,4-butanediol and trifunctional component trimethylolpropane are used in combination.

[0006]

The electrophotographic apparatus is usually used in an environment of 5 to 40 ° C. At this time, the temperature in the apparatus is 5 to 60 ° C. Cleaning blade
Good cleaning properties are required within this temperature range.

In order to satisfy the cleaning characteristics of the cleaning blade at a low temperature, it is necessary to add a large amount of 1,4-butanediol, but if this is done, the permanent set will become large and deformation will occur after long-term use, resulting in poor cleaning. In addition, the impact resilience at high temperatures becomes large, which results in chattering of the blade member when used at high temperatures. Conversely, a large amount of trimethylolpropane may be added to reduce permanent distortion and high-temperature impact resilience of the cleaning blade, but doing so increases the glass transition temperature and results in poor cleaning properties at low temperatures, and cleaning at low temperatures There is a problem that the characteristics and the prevention of permanent distortion and chattering noise at high temperature cannot be achieved at the same time.

In order to solve such a problem, conventionally,
Although the composition of the polyol that constitutes the soft segment and the content of the isocyanate compound that forms the hard segment have been mainly studied, low molecular weight chain extension
Almost no studies have been made on cross-linking agents, or only individual studies of chain extenders and cross-linking agents have been made, and no combination of these has been made.

In view of the above, it is an object of the present invention to provide a cleaning blade for an electrophotographic apparatus, which has both low temperature characteristics and permanent distortion and prevention of chattering noise at high temperatures.

[0010]

The gist of the present invention is to provide a cleaning blade for an electrophotographic apparatus comprising a blade member made of a polyurethane elastomer, a supporting member and an adhesive layer, wherein the polyurethane elastomer is a high molecular weight polyol, Isocyanate compound and chain extension
A cross-linking agent, the high molecular weight polyol is polyethylene adipate, and the chain extender / cross-linking agent is 1,
Consisting of 4-butanediol, 1,6-hexanediol and trimethylolpropane, the number of hydroxyl groups of 1,4-butanediol in the above chain extender / crosslinker and 1,6-
The ratio of the total number of hydroxyl groups of hexanediol to the number of hydroxyl groups of trimethylolpropane is 85:15 to 60:40, and the number of hydroxyl groups of 1,6-hexanediol is
The ratio with the number of hydroxyl groups of 4-butanediol is 97: 3-5.
It is about 0:50.

The blade member of the cleaning blade for an electrophotographic apparatus of the present invention is made of polyurethane elastomer. The above polyurethane elastomer is produced by a prepolymer method in which a high molecular weight polyol and an isocyanate compound are first reacted to form a prepolymer having isocyanate groups at both ends, and the prepolymer is cured with a chain extender / crosslinking agent.

The high molecular weight polyol used in the present invention is composed of polyethylene adipate. The polyethylene adipate has a molecular weight of 1,000 to 500.
A range of 0 is preferred. If it is less than 1000, the low temperature properties are significantly impaired, and if it exceeds 5000, the mechanical properties are poor.

The isocyanate compound used in the present invention is not particularly limited, and examples thereof include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), naphthylene diisocyanate (NDI),
Examples thereof include trisine diisocyanate (TODI), isomers and modified products thereof.

The chain extender / crosslinking agent in the present specification is a compound that causes a crosslinking reaction and a crosslinking reaction at the same time as the molecular chain extension reaction to cure, and may be simply referred to as a crosslinking agent or a curing agent. The chain extender / crosslinking agent used in the present invention includes 1,4-butanediol (hereinafter referred to as “14BG”), 1,6-hexanediol (hereinafter referred to as “16HG”) and trimethylolpropane (hereinafter referred to as “TMP”). ) Consists of. The compounding ratio in the above chain extender / crosslinking agent is 1
Total number of hydroxyl groups of 4BG and 16HG and TM
The ratio of P to the number of hydroxyl groups is 85:15 to 60:40,
Moreover, the ratio of the number of hydroxyl groups of 16HG and the number of hydroxyl groups of 14BG is 97: 3 to 50:50.

The ratio of the total number of hydroxyl groups of 16HG and that of 14BG is 85:15 with respect to the number of hydroxyl groups of TMP.
If it is more than 60:40, the chemical crosslink density is too low and the strain property is large. If it is less than 60:40, the chemical crosslink density is too much, so that the molecular chain is constrained and the glass transition temperature is significantly increased and the hard segment Since the concentration decreases, the hardness decreases, so the range is limited.

When the ratio of the number of hydroxyl groups of 16HG is more than 97: 3 with respect to the number of hydroxyl groups of 14BG, 16HG and 14
Aggregation of the hard segment formed by BG and isocyanate is reduced, the glass transition temperature is remarkably increased because the soft segment and the hard segment are mixed more than necessary, and the hardness is lowered due to the reduction of the cohesive force of the hard segment. When it is less than 50, the properties of 14BG are strengthened, the phase separation between the hard segment and the soft segment tends to proceed, and the strain property is increased, so that the range is limited.

The blade member according to the present invention can be obtained, for example, by molding a polyurethane elastomer by using a centrifugal molding method, a mold molding method or the like, cutting it into a predetermined size, and washing it if necessary. it can.

The supporting member according to the present invention is not particularly limited, and examples thereof include those made of rigid metal or elastic metal, plastic, ceramics, etc., and usually an untreated steel plate. It is possible to use a steel plate that has been surface-treated such as zinc phosphate treatment or chromate treatment, or a steel plate that has been subjected to a plating treatment, or the like. In the production of the cleaning blade for an electrophotographic apparatus of the present invention, it is preferable that the support member is used after being degreased with a solvent or the like.

The method for adhering the cleaning blade for an electrophotographic apparatus of the present invention is carried out by a commonly used method. For example, a commonly used adhesive is applied to the above support, and a blade member is attached thereon. It is done by things. After pasting, heating and pressing may be performed. Alternatively, the support coated with the adhesive may be placed in a mold in which the shape of the blade member is engraved, and bonded at the same time when the polyurethane elastomer is formed.

The blade member according to the present invention is a developing blade for regulating the toner layer thickness in order to carry a thin layer of toner on the outer periphery of the developing roll in the developing section of the electrophotographic apparatus, and a cleaning blade for the transfer belt in the transfer section. Etc. can also be applied.

[0021]

The impact resilience of the blade member at high temperature is caused by the micro and macro Brownian motions of the molecular chains, so it is necessary to control the Brownian motion to suppress the impact resilience. This movement of the molecular chain is largely influenced by the soft segment portion of the urethane elastomer. In order to control the movement of the molecular chain, there is a method of increasing the polar group density as a polyol composition or providing a steric hindrance, but in the method of providing a steric hindrance to the molecular chain, the intermolecular physical bond decreases. Therefore, it has an adverse effect on the breaking strength and strain characteristics. In the blade member according to the present invention, by using polyethylene adipate as the high molecular weight polyol, a polar group is introduced into the soft segment and Brownian motion of the molecular chain is reduced, so that impact resilience at high temperature can be suppressed.

The hard segment component needs to be physically coupled with the soft segment in order to control the Brownian motion of the soft segment and reduce the distortion characteristic. On the other hand, if the physical bond between the hard segment and the soft segment progresses too much, the movement of the soft segment is excessively controlled, resulting in a marked increase in the glass transition temperature. When 14BG is used as the chain extender / crosslinking agent, the hard segment composed of 14BG and isocyanate has a high cohesive property, and the hard segment and the soft segment tend to undergo phase separation, resulting in poor physical bondability.

The blade member according to the present invention uses 16HG having a slightly longer molecular chain than 14BG in combination with 14BG to appropriately reduce the aggregation of the hard segment and increase the mixing property with the soft segment, which is effective. Since such a physical bond can be formed, the strain characteristic is improved, the increase in the glass transition temperature is suppressed, and the cleaning property at low temperature is not impaired. Further, by using TMP, which is a trifunctional component, in combination with the 14BG, 16HG combination system, chemical cross-linking can be introduced into the structure to improve strain characteristics.

[0024]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Production Example 1 Synthesis of Prepolymer Polyethylene adipate (Nipporan 4060, manufactured by Nippon Polyurethane Industry Co., Ltd., hydroxyl group content 56.2 KOHmg / g) was used as a high molecular weight polyol. The high molecular weight polyol was dried under reduced pressure at 80 ° C. for 12 hours. To 100 g of this high molecular weight polyol, 39.5 g of 4,4'-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MT) was added, and the mixture was mixed at 80 ° C under N ₂ for 3 times.
A prepolymer was obtained by reacting for a time. The NCO content of the obtained prepolymer was 6.5% by weight.

Preparation Example 2 Synthesis of Prepolymer Polybutylene adipate (Nipporan 4010, manufactured by Nippon Polyurethane Industry Co., Ltd., hydroxyl group content 56.2 KOHmg / g) was used as a high molecular weight polyol. Production Example 1 below
A prepolymer was obtained in the same manner as above.

Production Example 3 Synthesis of Prepolymer Polycaprolactone as a high molecular weight polyol (Placcel 220 manufactured by Daicel Chemical Industries, Ltd., hydroxyl group content 56.
1 KOH mg / g) was used. Thereafter, the same procedure as in Production Example 1 was carried out to obtain a prepolymer.

Examples 1 to 5 and Comparative Examples 1 to 10 Molding of blade member The prepolymers obtained in Production Examples 1 to 3 were defoamed under reduced pressure at 100 ° C for 1 hour. The OH / NCO ratio is generally set to 0.9, and the 16HG / 14BG / TMP ratio is added to the prepolymer at the ratio shown in Table 1, mixed for 2 to 3 minutes, and added to a centrifugal molding machine at 140 ° C. for 1 hour. And formed into a sheet having a thickness of 2 mm. After post-crosslinking at 110 ° C. for 24 hours, the blade member was obtained by cutting into a predetermined size.

Evaluation of physical properties Hardness (Hs) was measured with a JIS-A spring hardness meter. The permanent elongation was the value after punching with JIS-1 dumbbell and holding at 200% elongation for 10 minutes. The glass transition temperature (Tg) shows the peak temperature of tan δ measured by a spectrometer under the condition of 5% elongation 10 Hz. The impact resilience is 25 according to JIS K 6301.
It was measured at ℃ and 50 ℃.

Table 1 shows the blending contents and physical property values. In Table 1, HG is 1,6-hexanediol, B
G represents 1,4-butanediol, and OH ratio represents the ratio of the number of hydroxyl groups.

[0031]

[Table 1]

Evaluation (1) The blade members of Examples and Comparative Examples were attached to a supporting member by a usual method, that is, using a double-sided tape to form a cleaning blade, which was set in a printer (Matsushita Electric Industrial Co., Ltd., product number P-5400). Then, continuous printing was performed under the conditions of 5 ° C. and 50 ° C., and each chattering noise and cleaning property were evaluated. (2) With the cleaning blade set on the photoconductor, the cleaning blade was left for 1 month in an atmosphere of 45 ° C., taken out, and then set in a copying machine to evaluate the cleaning property at room temperature.
Table 2 shows the results.

[0033]

[Table 2]

[0034]

EFFECT OF THE INVENTION Since the cleaning blade for an electrophotographic apparatus of the present invention has the above-mentioned constitution, the glass transition temperature is kept at a low temperature and the repulsion elasticity at a high temperature is controlled while suppressing the permanent set, so that a wide temperature range can be obtained. A stable cleaning property can be obtained over a long period of time.

Claims (1)

[Claims] 1. A cleaning blade for an electrophotographic apparatus comprising a blade member made of a polyurethane elastomer, a supporting member and an adhesive layer, wherein the polyurethane elastomer comprises a high molecular weight polyol, an isocyanate compound and a chain extender / crosslinking agent. The high molecular weight polyol is made of polyethylene adipate, the chain extender / crosslinking agent is made of 1,4-butanediol, 1,6-hexanediol and trimethylolpropane,
The ratio of the total number of hydroxyl groups of 1,4-butanediol and the number of hydroxyl groups of 1,6-hexanediol to the number of hydroxyl groups of trimethylolpropane in the chain extender / crosslinking agent is 85:
An electrophotographic apparatus characterized in that the ratio of the number of hydroxyl groups of 1,6-hexanediol to the number of hydroxyl groups of 1,4-butanediol is 97: 3 to 50:50. Cleaning blade.