JPH07113040A - Blade for copier having ionic conductivity - Google Patents

Abstract

PURPOSE:To obtain the blade, containing a metallic salt in an ionic state in an urethane elastomer, capable of ensuring a sharp edge from a homogeneous material, having a high strength and excellent in abrasion resistance with hardly any change in electric resistance to a temperature change. CONSTITUTION:This blade comprises (B) a metallic salt in an ionic state in (A) an urethane elastomer having urethane bonds in the molecular structure. Furthermore, the concentration of the component (B) is preferably 1.0X10<-6> to 1.0X10<-2> (mol/g) based on 1g component (A) and the component (B) is preferably an alkaline (earth) metal. The resultant blade has preferably 10<5> to 10<6> (OMEGA.cm) electric resistivity expressed in terms of volume resistivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade for a copying machine such as a cleaning blade and a developing blade used in a copying machine for plain paper, and in particular, the blade itself has an antistatic property (semi-conductivity). is there.

[0002]

2. Description of the Related Art Generally, a plain paper copying machine forms an electrostatic latent image by exposing an optical image on the surface of a photoreceptor and converting light into an electric charge. By using static electricity, toner having an opposite polarity is attached to the electrostatic latent image on the surface of the photoconductor to develop it, and the toner image formed is further transferred to a sheet. Thereafter, heat is applied to the toner image to melt it, and the toner image is pressed and fixed on the paper. Here, the toner remaining without being completely transferred is scraped off by a urethane elastomer blade, and an operation of returning to the initial state is performed. This is called a cleaning operation, and the blade used here is called a cleaning blade.
Since the cleaning blade is pressed against the photoconductor and relatively slides, a crosslinked urethane elastomer having excellent mechanical strength is used so that the edge portion is less likely to be worn.

Further, in order to improve the cleaning property,
It has been proposed that the blade material be made of a material having antistatic property (semi-conductivity). This is because the toner that has not been transferred and remains is charged, so it is difficult to remove due to strong electrical adsorption with the photoconductor, and the scraped toner adheres to the blade and is collected. The problem is that the blade itself is not easy, and the problem is solved by making the blade itself conductive. However, some resistance is also necessary to prevent short circuits, and it is said that this material is preferably an antistatic material (semiconductive material). As a result, it is possible to substitute the conventional functions of removing charge and charging the photosensitive member by corona discharge, and there is also a proposal that it becomes possible to make the device compact and ozoneless (Japanese Patent Laid-Open No. 4-30447).
No. 6). There have been many proposals of charging blades that can be replaced with corona charging for the purpose of eliminating ozone, and JP-A-56-19434
9 and JP-A-60-147756.

Regarding the material, since the elastomer generally has a high electric resistance of 10 ¹¹ to 10 ¹⁴ (Ω · cm), polymers such as hydrin rubber, nitrile butadiene rubber and ethylene propylene rubber are used in addition to the conventional cast type urethane. On the other hand, generally, a method of adding powder of conductive material such as carbon, graphite, metal or metal oxide, or a method of adding a cation / anionic surfactant is considered. The developing blade is pressed against a developing roller or the like of the developing mechanism of the copying machine to play a role of making the thickness of the toner adhered on the roller a uniform layer and a role of charging the toner by the sliding friction.

Here, in order to ensure the above-mentioned charging, it has been proposed that a voltage is directly applied to the blade to give a charge to the toner to obtain stable charging, but such a blade is obtained. In order to achieve this, the above-described method of adding a conductive substance can be considered. In this way, by imparting antistatic property to the original function of the blade, adding the function of static elimination and charging, or improving the function, the static eliminator that has been separately provided until now. Proposals have been made to integrate chargers and make them compact.

[0006]

However, when trying to obtain a blade for a copying machine such as a cleaning blade or a developing blade having antistatic property, the above-mentioned method has the following problems. First, in the method of adding conductive fine particles such as carbon, there are problems that the electric resistance value is not stable and a sharp edge for cleaning cannot be secured because the dispersibility of the powder is poor. In addition, when cast type urethane contains additives, in many cases the high strength characteristic of it cannot be obtained,
There is a problem that it is easily worn and loses durability.

[0007] In addition, the addition of a surfactant or the like has a small effect of reducing the electric resistance, so that it has to be added in a large amount, and conversely, if added in a large amount, deterioration of physical properties and precipitation from the elastomer surface pose problems. Become. In particular, at low humidity, there is no effect of reducing electric resistance, and it is difficult to obtain stability. On the other hand, liquid urethane for casting has the advantage that, in order to obtain a plate-shaped molded product using a centrifugal molding machine, the molding surface on the atmosphere side, which is not the mold surface, is smooth, which is convenient for obtaining sharp edges. However, other rubber compounds are disadvantageous. Due to the above-mentioned problems, there is no antistatic blade that has been adopted so far, and development has been awaited.

In view of the above problems, the present invention has an object to provide a blade for a copying machine having ion conductivity having the following specifications. 1. Be able to secure sharp edges (unevenness is 10μ or less) with a homogeneous material. 2. Maintains the properties of urethane elastomer, has high strength and is excellent in wear resistance. 3. The electrical resistivity of the urethane elastomer is 10 ⁵ to 10 ¹⁰ (Ω · cm) in terms of volume resistivity, and the change in resistance is small with respect to environmental changes in temperature.

[0009]

In order to achieve the above object, the present invention provides a copier blade made of a urethane elastomer having a urethane bond in its molecular structure,
This urethane elastomer was allowed to contain a metal salt in an ionic state. Further, the concentration of the metal salt is 1.0 × 10 ⁻⁶ to 1.0 × 10 with respect to 1 (g) of the urethane elastomer.
The range was ^-2 (mol / g). Further, the contained metal salt is an alkali metal salt or an alkaline earth metal salt.
Further, the blade for a copying machine having the above structure has an electric resistivity of 10 ⁵ to 10 ¹⁰ (Ω · cm) in terms of volume resistivity and has a charge removing or charging function.

Urethane was selected as the elastomer because it is easy to retain the salt in an ionic state and, as described above, the blade has high mechanical strength. The urethane elastomer used is generally called casting urethane, and may be one conventionally used. Usually, a urethane prepolymer prepared by reacting a polyol with a diisocyanate is heated and defoamed, a curing agent is added, and a sheet-shaped molded product is obtained by a centrifugal molding machine. Generally, as a composition used for a blade for a copying machine, for example, a urethane prepolymer composed of polyester polyol and MDI (4,4′-diphenylmethane diisocyanate),
A mixture of 4-BG (butanediol) and TMP (trimethylolpropane) was added as a crosslinking agent.

As the metal salt to be added, basically all metal salts can be used, but in view of solubility in polymer, ionic conduction efficiency, inhibition of cross-linking, etc., it is an alkali metal salt or an alkaline earth metal salt. Specifically, specifically, the cation is Li, Na, K, Mg, Ca, and the anion is Cl, Br, I, ClO ₄ , SCN, BF ₄ , CF.
₃ , SO _3, etc., and compounds of these combinations are selected. Of these, lithium salt is particularly preferable because it has a small atomic radius and ions easily move in the polymer. For example,
LiI, LiClO ₄ , LiSCN, and LiBF ₄ .

The addition ratio is 1.0 × 10 ^-6 to 1.0 × 10 ^{-2 with} respect to 1 g of the urethane elastomer.
The range is (mol / g). 1.0 × 10 ^-6 (mol
/ G) or less, the effect of reducing the electric resistance value is small,
The desired electrical resistance cannot be obtained. Furthermore, 1.0 x 1
If the content is 0 ^-2 (mol / g) or more, the electric resistance value may be too low, the once-dissolved salt may be crystallized in the polymer to deteriorate the physical properties, or a sharp edge may not be obtained. Alternatively, it may cause problems such as precipitation.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. (Example 1) Polyester polyol and MDI (4,
A urethane prepolymer was obtained from 4′-diphenylmethane diisocyanate) by a conventional method. The resulting prepolymer had a free isocyanate group content of 7.06% and 8
The viscosity at 0 ° C. was 1900 centipoise. 1,4-BG (butanediol) and TMP as cross-linking agent
A mixture of (trimethylolpropane) is used, and 1 g of LiClO ₄ (lithium perchlorate) is dissolved in 100 g of this cross-linking agent mixture to prepare a curing agent solution. This solution was added to the urethane prepolymer so that the isocyanate group / hydroxyl group equivalent ratio was 1.05, and mixed by stirring to obtain a molding material. In this case, the salt content is 7.5 × 10 ⁻⁶ (mol / g) with respect to 1 (g) of the urethane elastomer.
Becomes

This molding material was poured into a molding drum (diameter 200 mm, width 500 mm, temperature 140 ° C.) of a centrifugal molding machine and rotated at 600 rpm for 1 hour. The obtained molded product is demolded and further heat treated at 110 ° C. for 9 hours,
After cooling, the annular molded product was precisely cut to obtain a polyurethane elastomer plate-shaped molded product.

Example 2 A plate-shaped molded product was obtained in the same manner as in Example 1 except that the content of the metal salt in Example 1 was adjusted as follows. A curing agent solution was prepared by dissolving 10 g of LiClO ₄ in 100 g of the crosslinking agent mixture. In this case, the content of the metal salt is 7.5 × 10 ⁻⁵ (mol / g) with respect to 1 (g) of the urethane elastomer.

Example 3 A plate-shaped molded product was obtained in the same manner as in Example 1 except that the content of the metal salt in Example 1 was adjusted as follows. 50 g of LiClO ₄ was dissolved in 100 g of the crosslinking agent mixture to prepare a curing agent solution. In this case, the content of the metal salt is 3.6 × 10 ⁻⁴ (mol / g) with respect to 1 (g) of the urethane elastomer.

Comparative Example 1 A plate-shaped molded product was obtained in the same manner as in Example 1 except that no metal salt was added to the curing agent.

(Comparative Example 2) Conductive carbon black (Ketjen Black (registered trademark) EC manufactured by Lion Akzo Co.) was added to 100 g of the urethane prepolymer of Example 1.
Fine powder was mixed at a ratio of 20 g, and after being mixed by a ball mill,
I tried to obtain a molded product with a curing agent that does not add metal salts,
Since the viscosity increased, the thickness of the plate-shaped molded product obtained by centrifugal molding was not uniform.

Comparative Example 3 A cationic active agent (Antex (registered trademark) C-200 manufactured by Toho Chemical Co., Ltd.) was mixed with 100 g of the curing agent at a ratio of 10 g instead of the metal salt of Example 1, and In the same manner as in Example 1, a plate-shaped molded product was obtained. The physical properties of the above plate-shaped molded product were evaluated, and the results are shown in Table 1. Regarding the physical properties of normal state, JIS K 6
It measured according to 301. The electrical resistivity is JIS K69
According to No. 11, it was measured with a digital ultra-high resistance meter manufactured by Advantest Corporation.

[0020]

[Table 1]

In the evaluation of the physical properties shown in Table 1, in comparison with the case of not containing the metal salt of Comparative Example 1, in the example, the electrical resistivity was 10 ⁷ to ¹⁰ 10 in terms of volume resistivity depending on the addition amount of the metal salt.
It can be seen that the target level can be controlled to (Ω · cm) and the physical properties such as strength are not impaired. On the other hand, in the case of adding the carbon fine particles of Comparative Example 2, it can be seen that due to this dispersion problem, the strength is significantly reduced and the moldability is not good. Further, it can be seen that in Comparative Example 3 in which the cationic activator was added, the strength was slightly lowered and the effect of lowering the resistance was small. Further, in terms of moldability, Examples 1 to 3 and Comparative Example 1 had no problem, and sharp edges (irregularities of 10 μm or less) were obtained.

Further, the above Examples 1 to 3 and Comparative Examples 1 to 3
The cleaning property was evaluated using a blade for a copying machine made of the urethane elastomer. As shown in FIG. 1, the evaluation apparatus has a charging corotron 2, a developing machine 3, a transfer corotron 4, a charge removing corotron 5, and a cleaning roller 5 at a predetermined interval on the surface of a drum-shaped photoconductor 1 that rotates at a constant peripheral speed. The blades 6 are arranged facing each other.
Using this evaluation device, the surface of the photoreceptor 1 is charged, an electrostatic latent image is formed by light image exposure, and the latent image is developed with the toner supplied from the developing device 3 to form a toner image. Then, the toner image is transferred to the plain paper through the transfer corotron 4 at a constant temperature and pressure. Further, the residual toner after the transfer on the surface of the photoreceptor 1 can be scraped off by the cleaning blade 6 via the static elimination corotron 5. still,
In this device, the cleaning blade 6 is attached to the metal holder 7
By connecting to the AC power source 8 or grounding via the, an AC voltage can be applied and a blade ground can be performed as described later.

The evaluation was carried out using the above evaluation device. In order to confirm the static elimination effect, A when the static elimination corotron 5 before cleaning is used, B when the static elimination corotron 5 is not used and the blade is grounded, and AC voltage for static elimination of the photoconductor 1 through the cleaning blade 6. 1000
The cleaning property was evaluated for each of C when Vpp was applied and C. The evaluation was performed by classifying the degree of dirt due to the residual toner on the plain paper after transfer into 5 ranks. The larger the number is, the better the cleaning property is (the less the stain is), and the practical level is 3 or more. The results are shown in Table 2.

[0024]

[Table 2]

From the results shown in Table 2, it can be seen that the examples have a cleaning property of a practical level without using a static eliminator, and the cleaning properties are further improved by applying an alternating current.
This eliminates the need for corona discharge and enables cost reduction and downsizing of the device. Further, it is also advantageous for ozoneless. On the other hand, Comparative Example 1 without antistatic property
It can be seen that, although A is excellent in removing electricity before cleaning, B and C are inferior in cleaning property due to electric attraction between the photoconductor and the toner. It can be seen that in Comparative Example 2, a sharp edge cannot be obtained because the carbon black as the conductive agent is poorly dispersed, and the cleaning property of A is remarkably poor. Further, Comparative Example 3 is inferior in evaluation in B and C because the antistatic property is not sufficient. As described above, by using the urethane elastomer containing the metal salt in the ionic state, the copying machine blade having the desired functionality can be provided.

[0026]

EFFECTS OF THE INVENTION By using a blade for a copying machine using a urethane elastomer containing a metal salt in an ionic state according to the present invention, as compared with the case of using a conventional elastomer to which carbon or metal particles are added. As a result, it is possible to reduce variations in the electric resistance of the blade for the copying machine. Further, the mechanical strength is the same as that in the case where no metal salt is added, and there is no problem with abrasion. Further, the copier blade of the present invention has a low electrical efficiency of 10 ^{5 in} terms of volume resistivity.
Since it has an antistatic property of -10 ¹⁰ (Ω · cm),
In addition to exhibiting excellent charge removal and cleaning properties as a cleaning blade, it also exhibits excellent thin film forming ability and toner charging performance as a developing blade, making it possible to use both a cleaning blade and a developing blade with one copier blade. did.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main mechanical portion of an evaluation device.

[Explanation of symbols]

 1 Photoreceptor 2 Charging Corotron 3 Developing Machine 5 Eliminating Corotron 6 Cleaning Blade

Claims (4)

[Claims] 1. A copier blade comprising a urethane elastomer having a urethane bond in its molecular structure,
A blade for a copying machine having ion conductivity, wherein the urethane elastomer contains a metal salt in an ionic state. 2. The concentration of the metal salt is 1.0 × 10 ⁻⁶ to 1.0 × 10 with respect to 1 (g) of the urethane elastomer.
^The blade for a copying machine having ion conductivity according to claim 1, which is in a range of ^-2 (mol / g). 3. The blade for a copying machine having ion conductivity according to claim 2, wherein the contained metal salt is an alkali metal salt or an alkaline earth metal salt. 4. The blade for a copying machine has an electric resistivity of 10 ⁵ to 10 ¹⁰ (Ω · cm) in terms of volume resistivity and has a charge removing or charging function. A blade for a copying machine having the ion conductivity according to the item 1.