JPH0452470B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic copying machine. In general, electrophotographic copying machines, especially electrophotographic copying machines that use plain paper as recording paper, develop the latent image formed on the photoreceptor with toner and transfer the toner image to the recording paper, thereby repeatedly printing the photoreceptor. Therefore, as a final step in a single electrophotographic process, it is necessary to clean the photoreceptor to remove residual toner adhering to it. As an example of such a cleaning method, a blade cleaning method is known in which a cleaning blade made of an elastic material is brought into contact with the photoreceptor and rubbed against the photoreceptor, and this method has the advantage of being very simple in structure. It's advantageous. Conventionally, known materials for blades used in this blade cleaning method include urethane rubber, silicone rubber, fluorine rubber, chloroprene rubber, butadiene rubber, etc. Among these, urethane rubber is more expensive than other rubbers. , its mechanical properties,
In particular, it is extremely useful in terms of its excellent wear resistance. Conventionally, in the cleaning blade, for example, urethane rubber obtained by reacting polyethylene adipate ester, polyoxypropylene glycol, caprolactone ester, etc. with polyisocyanate can be used as a material, as disclosed in JP-A-54-104840. Are listed. However, not all substances belonging to this group of substances are suitable as cleaning blades, regardless of their structure, molecular weight, etc. At present, polyethylene adipate ester is used as a raw material, and 4,
Polyisocyanate raw materials such as 4'-dimethylene diisocyanate and 1,5-naphthylene diisocyanate are used, and these are reacted and cured by the action of a glycol such as 1,4-butanediol, which is a curing agent. However, this cleaning blade has the drawback that its characteristics change greatly depending on changes in ambient temperature, and that it does not necessarily exhibit the desired cleaning effect satisfactorily at temperatures of, for example, 10° C. or lower. The present invention has been made based on the above circumstances, and its object is to provide an electrophotographic method in which a cleaning blade exhibits a good cleaning function even in a low-temperature environment and a good copy image can be formed. Copy machines are provided. This object is to provide an electrophotographic copying machine comprising a photoreceptor and a cleaning blade that cleans the surface of the photoreceptor by rubbing against the photoreceptor, the cleaning blade comprising a lactone ester component having 5 or less carbon atoms. This is achieved by an electrophotographic copying machine characterized in that it is made of urethane rubber obtained by reaction-curing a polylactone ester containing polyisocyanate and a polyisocyanate. The present invention will be specifically explained below with reference to the drawings. In the present invention, as shown in FIG. A photoreceptor drum 11 is provided to rotate in the direction of arrow A, and the outer peripheral area of the photoreceptor drum 11 is provided with a charging device 12 for charging the photosensitive layer, an original light image exposure device 18 for forming an electrostatic charge image, and Developing devices 14 for developing an electrostatic image are arranged in this order in the rotational direction of the photosensitive drum 11, and following the developing devices 14, a transfer sheet is fed along the path P by a transfer paper feeding roller 15. A transfer electrode 16 for electrostatically transferring a toner image formed by development onto paper and a separation electrode 17 for separating the transfer paper from the photoreceptor drum 11 are provided in this order, and the photoreceptor Exposure mechanism 18 for erasing charges along the rotational direction of drum 11
, and in the area following this, the holder 20
For example, the cleaning blade 19 is moved so that its leading edge extends over the entire width of the photoreceptor drum 11.
The material of the cleaning blade 19, which is provided so as to face each other with a pressing force of ~25 g/cm, is obtained by reaction-curing a polylactone ester containing a lactone ester component having 5 or less carbon atoms with a polyisocyanate. An electrophotographic copying machine is constructed using urethane rubber. Reference numeral 21 denotes a collection container for toner scraped off by the cleaning blade 19. The present invention is characterized in that the material of the cleaning blade 19 is urethane rubber obtained from a specific polylactone ester, and the structure of the electrophotographic copying machine other than this is arbitrary. In the present invention, as described above, since the cleaning blade 19 is made of a specific urethane rubber, the cleaning blade has good physical properties, especially stability at low temperatures. Therefore, a good and stable cleaning effect can be obtained even in a low-temperature environment, and a good copy image can be formed. The reason why such excellent effects are obtained is not necessarily clear, but the inclusion of a lactone ring component allows the urethane rubber to have good physical properties, and the number of carbon atoms in the lactone is 5 or less. Therefore, compared to the case where the polylactone ester forming the urethane rubber is composed of a lactone ester component having more than 5 carbon atoms, the number of ester components will be larger for the same molecular weight. The intramolecular bonding force of the ester group in the ester component is effectively exerted, and as a result, the resulting urethane rubber has good physical properties, and it does not become brittle and harden especially at low temperatures, so it still maintains good physical properties. It is presumed that this is because In the urethane rubber used as the material of the cleaning blade in the present invention, the number of carbon atoms in the polylactone ester, which is the raw material of the component, is 5.
If the proportion of the ester component based on the following lactones is too low, desirable characteristics cannot be obtained, and it is preferable to use a polylactone ester containing at least 30% by weight or more. The polylactone ester obtained from the ester of lactone having 5 or less carbon atoms, which is a raw material for the urethane rubber that is the material of the cleaning blade, preferably has an average molecular weight in the range of 1,000 to 4,000. The method for measuring the average molecular weight is to add an acetylation reagent consisting of acetic anhydride and pyridine to polylactone ester, acetylate it at a specified reaction temperature and for a certain period of time, and calculate the amount of potassium hydroxide required to neutralize the acetic acid produced. terminal by
This value is obtained by quantifying OH groups and measuring the number average molecular weight. In addition, since the polylactone ester is actually obtained as a mixture of various components with different bonding states, it is not necessarily appropriate to define it by a specific structural formula, but this polylactone ester can be expressed by the general formula [I]. If it were to be shown, it would probably look something like the following. General formula [I] HO[-X ₁ ] _n -R[-X ₂ ] _o -OH In the formula, X ₁ and X ₂ are cleavage residues of a lactone ring having 5 or less carbon atoms and are mutually They may be the same or different, the sum of m and n is 2 to 35, and m:n is 1:3 to
The range is such that the ratio is 3:1. R is a linking group for X ₁ and X ₂ and is a divalent organic group having about 800 or less carbon atoms. In addition, the average molecular weight (molecular weight based on the above measurement method) of the compound represented by general formula [I] is preferably
1000-4000, and the lactone ester component (X ₁
The content of +X ₂ ) is preferably 30% by weight or more. In order to produce a polylactone ester as represented by the above general formula [I], 1 mol of a polymerization initiator is added to 2 to 35 mol of the same or different lactone compound having 5 or less carbon atoms, temperature 150
Ring-opening addition polymerization is performed at ~300°C to obtain a polylactone ester with an average molecular weight of 1,000 to 4,000.
Examples of the polymerization initiator include -OH group, -
An organic compound having at least two active hydrogen groups such as _NH2 group or -SH group is used. The lactone compound for forming the lactone ring-cleaved residue in the general formula [I] has a 3- to 6-membered lactone ring and has 5 or less carbon atoms. Specific examples of such lactone compounds include the following.

[Table] Further, as the polymerization initiator for forming the linking group R in the general formula [I], the following compounds may be mentioned, for example.

【table】

[B-2]

Commercial product: “Desmodyur N” manufactured by West German Bayer [B-3] Metaphenylene diisocyanate

[Formula] Commercial product: "Naphconate" manufactured by National Aniline Co., Ltd. [B-4] Tolylene diisocyanate and

Commercially available mixtures with [Formula]: "Desmodyur T" manufactured by Bayer AG, West Germany "Hylen TM" manufactured by DuPont [B-5] 2,4-tolylene diisocyanate dimer Commercial product: "Desmodyur TT" manufactured by West German Bayer [B-6] Reaction product of toluylene isocyanate and trimethylolpropane Commercial product: "Desmodyur L" manufactured by West German Bayer AG Commercial product: "Coronate L" manufactured by Nippon Polyurethane Kogyo Co., Ltd. [B-7] 3,3'-dimethyl-diphenyl-
4,4'-diisocyanate Commercial product: "Hyren H" manufactured by DuPont [B-8] Diphenylmethane-4,4'-diisocyanate Commercial product: "Millionate MT" manufactured by Nippon Polyurethane Industries [B-9] 3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate Commercial product: “Hiren DMM” manufactured by Dupont [B-10] Torphenylmethane-triisocyanate Commercial product: "Desmodyur R" manufactured by West German Bayer AG [B-11] Polymethylene phenyl isocyanate Commercial product: “Millionate MR” manufactured by Nippon Polyurethane Industries [B-12] Naphthalene-1,5-diisocyanate Commercial product: "Desmodyur 15" manufactured by West German Bayer [B-13] Dicyclohexylmethane diisocyanate Manufactured by Allied Chemical Co., Ltd. Specific examples of the curing agent include the following.

[Table] In order to manufacture a cleaning blade made of urethane rubber using the above polylactone ester, polyisocyanate and curing agent, the following method is suitable. That is, a polylactone ester that has been dehydrated and a polyisocyanate are mixed and reacted at a temperature of 70 to 150°C for 10 to 120 minutes to prepare a urethane prepolymer. A liquid rubber composition is prepared by adding a curing agent at a ratio such that the ratio of the number of moles of the polyester to the number of moles of hydroxyl groups and/or amino groups formed by the polyester and the curing agent is 1.00 to 1.30. For example, pour it into a centrifugal casting machine kept at a temperature of about 140°C. FIG. 2 shows an example of a centrifugal casting machine, in which 31 is a heating chamber, 32 is a heating fluid flow path for heating the heating chamber 31, 33 is a heat insulating material layer, 34 is an opening/closing door, and 35 is a cylindrical rotor. , 36 is a drive shaft, and 37 is a motor. The rubber composition is injected into the rotor 35 which is rotating at high speed, and is uniformly spread over the casting surface by the inner peripheral surface of the rotor 35 due to the centrifugal force caused by the rotation. A cylindrical film-like body 38 (indicated by a chain line) is formed by spreading to a certain thickness. This film-like body 38 is solidified as the crosslinking by the curing agent progresses, and the thus formed solidified urethane rubber layer is peeled off from the casting surface, and then heat-treated and aged for several days to form a rubber plate for a blade. This rubber plate is cut to meet the specifications of the intended electrophotographic copying machine to produce a cleaning blade. In addition to the above-mentioned centrifugal casting method, there are other methods, such as injecting and solidifying into a mold in the shape of a cleaning blade, or press-forming with such a mold.
Any of these methods can advantageously produce a cleaning blade made of urethane rubber. Incidentally, the above-mentioned urethane rubber may contain an anti-aging agent such as monocarbodiimide. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto. Examples 1-10 According to what is shown in Table 1, lactone and polymerization initiator were measured and mixed at a temperature of 150-350°C for about 30 to
A total of 10 types of polylactone esters PLE1 to PLE10 were synthesized by addition polymerization for 180 minutes.

[Table] Polyisocyanate was added to these 10 types of polylactone esters according to what is shown in Table 2, and the reaction was carried out at a temperature of approximately 70°C for 100 minutes to synthesize polyurethane prepolymer. After adding a crosslinking agent and reacting at a temperature of 120°C for 2 minutes, the rubber composition that is still in a liquid state is
The mixture was injected into the rotor of the centrifugal casting machine shown in Figure 2, which was maintained at a temperature of around 140°C, and the rotor was rotated at approximately 1000 revolutions per minute, continuing to rotate for 20 to 120 minutes to form a solidified rubber layer. This was peeled off, taken out, heat treated in a heating furnace at a temperature of about 140°C for 180 minutes, and then aged for 6 to 8 days at room temperature.
A total of 10 types of cylindrical urethane rubber plates UR1~
Got UR10. These urethane rubber plates
Hardness according to JISK6301A scale is 65~
It was within a practically useful range of 76 degrees.

[Table] The proportions represent the parts per 100 parts of ester UR: Urethane rubber plate MDI: Diphenylmethane-4,4'-diisocyanate TDI: Tolylene diisocyanate 1,4B: 1,4-butanediol MOCA: 3,3'-dichloro- 4,4'-Diaminodiphenylmethane When the thickness distribution of these urethane rubber plates was investigated, the error was found to have an accuracy of ±15 μm. These urethane rubber plates thus obtained were cut according to the specifications of an electrophotographic copying machine "U-Bix 3000" (manufactured by Konishiroku Photo Industry Co., Ltd.) to obtain a total of 10 types of cleaning blades CB1 to CB10. Then, an electrophotographic copying machine is configured using each of the cleaning blades CB1 to CB11 described above as the cleaning blade 19 in the configuration shown in FIG. 1, and continuous copying is performed under various environmental conditions shown in Table 3. The number of copies until staining due to defects occurred was determined. The cleaning blade 19 has an angle between its tip contact portion and the surface of the photoreceptor drum 11 with respect to the upstream surface.
It was held by the holder 20 so that the pressing force F was 25 g/cm at 160 degrees. The results are also shown in Table 3. Note that "40,000" indicates that no cleaning failure occurred even when the number of copies reached 40,000.

[Table] Comparative Example 1 For comparison, a polyurethane prepolymer was synthesized according to the procedures shown in Table 4 using polyethylene adipate ester instead of polylactone ester in the example, and a comparative urethane rubber was prepared in the same manner as above. Obtained board UR11.

[Table] Comparative Example 2 In Example 1, ε-caprolactane having 6 carbon atoms was used instead of δ-valerolactone, PPG with a molecular weight of about 1500 was used as a polymerization initiator, and the lactone content was about 25% by weight. % polylactone ester PLE12 was synthesized and used,
Urethane rubber plate UR1 for comparison in the same manner as UR1
I got 2. Comparative Example 3 A comparative urethane rubber plate was prepared in the same manner as in Comparative Example 1, except that polyoxypropylene glycol was used instead of polyethylene adipate ester.
I got UR13. The above comparison urethane rubber plates UR11 to UR1
Cleaning blades CB11 to CB13 were obtained in the same manner as in the example using each of No. 3, and a similar cleaning test was conducted using each of them. The results are shown in Table 5.

[Table] As is clear from the above results, this book is equipped with a cleaning blade made of urethane rubber obtained by reacting polylactone ester containing a lactone ester component having 5 or less carbon atoms with polyisocyanate. According to the invented electrophotographic copying machine, it is practically necessary, especially at low temperatures.
It can be cleaned well for 5,000 times, especially when using polylactone ester containing 30% by weight or more of a lactone ester component with 5 or less carbon atoms, or a polylactone ester with an average molecular weight of 1,000 to 4,000, even at low temperatures. Good copy images can be formed over multiple times.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of the configuration of an electrophotographic copying machine, and FIG. 2 is an explanatory sectional view of a centrifugal casting machine for manufacturing cleaning blades. 11... Photosensitive drum, 12... Charging device, 1
3... Original light image exposure mechanism, 14... Developing device, 15
... Feeding roller, P ... Passage, 16 ... Transfer electrode, 17 ... Separation electrode, 18 ... Exposure mechanism for charge erasing, 19 ... Cleaning blade, 20 ...
...Holder, 21...Toner collection container, 31...
Heating chamber, 32...Heating fluid flow path, 33...Insulating material layer, 34...Opening/closing door, 35...Cylindrical rotor, 3
6... Drive shaft, 37... Motor.

Claims (1)

[Scope of Claims] 1. In an electrophotographic copying machine comprising a photoreceptor and a cleaning blade that cleans the surface of the photoreceptor by rubbing against it, the cleaning blade has a carbon atom number of 5 or less. An electrophotographic copying machine characterized in that the material is urethane rubber obtained by reaction-curing a polylactone ester containing a lactone ester component and a polyisocyanate. 2. The electrophotographic copying machine according to claim 1, wherein the content of the lactone ester component having 5 or less carbon atoms in the polylactone ester is 30% by weight or more. 3 Average molecular weight of polylactone ester is 1000~
4000, an electrophotographic copying machine according to claim 1.