Paper feed roll and paper feeding device

Abstract

Provided are a paper feed roll improved in durability by maintenance of the frictional coefficient of the roll surface even in long-term use, and a paper feeding device.　Provided is a paper feed roll 12 comprising a shaft body 12a and an elastic body layer 12b formed on the outer peripheral surface of the shaft body 12a, the elastic body layer 12b being constituted from a rubber composition including urethane rubber, surface unevenness is formed by a plurality of projections on the outer peripheral surface of the elastic body layer 12b, the surface roughness Rz of the outer peripheral surface of the elastic body layer 12b being 30-280 μm, and the profile height of the projections when the surfaces of the projections are observed by microscope after feedthrough of 30,000 sheets of paper in a feedthrough test under the conditions below being 2.0-10 µm. Also provided is a paper feeding device 10 in which a paper feed roll is one or both of a paper delivery roll and a separation roll. Environment: 10°C × 10% RH; printer: load of 400 g and paper passthrough speed of 300 mm / sec

Description

Paper feed roll and paper feeder

[0001] The present invention relates to a paper feed roll and a paper feed device that are suitable for use in electrophotographic devices such as copying machines, printers, and facsimiles that employ an electrophotographic system.

[0002] Electrophotographic devices such as copiers, printers, and facsimiles that use electrophotography are equipped with a paper feeder, which includes a pickup roll that feeds paper from a paper cassette, a feed roll that transports the paper, and a retard roll.

[0003] For example, Patent Document 1 describes a paper feed and transport roll in which a grain pattern having a surface roughness Ra of 10 μm to 150 μm is formed on the roll surface, and the hardness is set to a range of 10° to 30° on the Shore A scale. Also, Patent Document 2 describes a paper feed device having a friction separation roller type separation paper feed unit consisting of a pair of rollers, in which the surface roughness of the surface of the separate roller is made higher than the surface roughness of the surface of the feed roller, and the surface roughness of the surface of the feed roller is set to 5 μm to 30 μm in ten-point mean roughness (Rz), and the surface roughness of the surface of the separate roller is set to 40 μm or more in ten-point mean roughness (Rz).

[0004] Japanese Patent Laid-Open No. 09-156784 Japanese Patent Laid-Open No. 2004-277025

[0005] These paper feed rolls maintain friction with the paper due to the tackiness inherent in the rubber, and transport the paper. Paper feed rolls must continue to maintain their paper transport function throughout their required service life. When the roll surface is made of urethane rubber, the urethane rubber is resistant to wear and can maintain its surface irregularities, so it has been considered to have excellent durability. However, when paper is fed through the roll for a long period of time, paper dust can adhere to the convex parts of the irregularities on the roll surface, and the coefficient of friction may not be maintained even if the surface irregularities are maintained.

[0006] The problem to be solved by the present invention is to provide a paper feed roll and a paper feed device that maintain the coefficient of friction of the roll surface even after long-term use and improve durability.

[0007] After extensive research, the inventors came up with the idea of ​​extending the life of the urethane rubber roll by actively wearing down a portion of the surface. They then decided to maintain the coefficient of friction by partially wearing down the convex surface of the urethane rubber roll using frictional force during use, forming minute depressions on the convex surface, and depositing paper powder in these depressions.

[0008] That is, the paper feed roll according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, the elastic layer being made of a rubber composition containing urethane rubber, the outer peripheral surface of the elastic layer having a surface irregularity formed by a plurality of convex portions, the surface roughness Rz of the outer peripheral surface of the elastic layer being 30 μm or more and 280 μm or less, and the profile height when the surface of the convex portions is observed under a microscope after 30,000 sheets have been passed through in a paper passing test under the following conditions: Environment: 10°C x 10% RH Printer: Load 400 g, paper passing speed 300 mm / sec

[0009] The JIS-A hardness of the surface of the elastic layer is preferably 30 degrees or more and 60 degrees or less. The isocyanate constituting the urethane rubber of the elastic layer is preferably diphenylmethane diisocyanate or tolylene diisocyanate. The paper feed roll according to the present invention may be either or both of a paper feed roll and a separation roll.

[0010] The paper feeder according to the present invention is characterized in that the paper feed roll is either one or both of a paper feed roll and a separation roll.

[0011] (1) The paper feed roll according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, the elastic layer being made of a rubber composition containing urethane rubber, the outer peripheral surface of the elastic layer having a surface irregularity formed by a plurality of convex portions, the surface roughness Rz of the outer peripheral surface of the elastic layer being 30 μm or more and 280 μm or less, and the profile height of the convex portion surface observed under a microscope after 30,000 sheets have been passed through in a paper passing test under the following conditions: Environment: 10°C x 10% RH Printer: Load 400 g, Paper passing speed 300 mm / sec

[0012] (2) In the above (1), the JIS-A hardness of the surface of the elastic layer is preferably 30 degrees or more and 60 degrees or less.

[0013] (3) In the above (1) or (2), the isocyanate constituting the urethane rubber of the elastic layer may be diphenylmethane diisocyanate or tolylene diisocyanate.

[0014] (4) In any one of the above (1) to (3), the paper feed roll may be either or both of a paper feed roll and a separation roll.

[0015] (5) In the paper feeder according to the present invention, the paper feed roll of any one of (1) to (3) above is either or both of a paper feed roll and a separation roll.

[0016] In the paper feed roll according to the present invention, the elastic layer is made of a rubber composition containing urethane rubber, and the outer peripheral surface of the elastic layer has a surface irregularity formed by a plurality of convex portions, and the surface roughness Rz of the outer peripheral surface of the elastic layer is 30 μm or more and 280 μm or less. In a paper feeding test under the above conditions, the surface of the convex portions has a profile height of 2.0 μm or more and 10 μm or less when observed under a microscope after 30,000 sheets have been fed. Therefore, the coefficient of friction of the roll surface is maintained even during long-term use, and durability is improved.

[0017] Here, if the JIS-A hardness of the surface of the elastic layer is 30 degrees or more and 60 degrees or less, the frictional force during use tends to partially wear down the convex surface of the urethane rubber roll, easily forming minute recesses on the convex surface.

[0018] Furthermore, if the isocyanate constituting the urethane rubber of the elastic layer is diphenylmethane diisocyanate or tolylene diisocyanate, it has excellent abrasion resistance, and frictional forces during use tend to partially wear down the convex surfaces of the urethane rubber roll, forming fine recesses on the convex surfaces.

[0019] The paper feed roll can be either or both of a paper feed roll and a separation roll.

[0020] Furthermore, in the paper feeding device of the present invention, since the paper feeding roll of the present invention is either or both of a paper feed roll and a separation roll, the coefficient of friction of the roll surface is maintained even over long periods of use, improving durability.

[0021] 1 is a schematic diagram of a paper feeding device; FIG. 2 is a diagram of the paper feeding operation of the paper feeding device shown in FIG. 1; FIG. 2(a) shows the state before one sheet of paper arrives between the rolls, and FIG. 2(b) shows the operation when one sheet of paper arrives between the rolls; FIG. 3(a) shows the state before two sheets of paper arrive between the rolls, and FIG. 3(b) shows the operation when two sheets of paper arrive between the rolls; FIG. 3(a) is an enlarged photograph of the convex surface of the elastic layer in Example 1, and FIG. 3(b) is a cross-sectional profile in the paper passing direction.

[0022] The paper feed roll according to the present invention will be described in detail below. Fig. 1 is a schematic diagram of a paper feed device. Figs. 2 and 3 are diagrams showing the paper feeding operation of the paper feed device shown in Fig. 1.

[0023] As shown in FIG. 1 , the paper feed device 10 includes a paper feed roll 12 (feed roll) and a separation roll 14 (retard roll). The paper feed roll 12 includes a shaft 12a and an elastic layer 12b formed on the outer periphery of the shaft 12a. The separation roll 14 includes a shaft 14a and an elastic layer 12bb formed on the outer periphery of the shaft 14a. The paper feed roll 12 is driven to rotate by power from a drive source (motor) (not shown) and functions to transport paper P. The separation roll 14 is pressed against the paper feed roll 12 with a predetermined pressure by a biasing member (e.g., a spring) (not shown). The separation roll 14 also includes a built-in torque limiter (not shown) that applies a brake torque in the direction opposite to the rotational direction (indicated by the arrow) in which paper P is transported.

[0024] The paper P to be transported is stacked in a paper feed cassette 16. The surface of a pull-in roll 18 (pickup roll) is in frictional contact with the upper surface of the stacked paper P, and the pull-in roll 18 is configured to sequentially pay out the paper P from the paper feed cassette 16 toward the paper feed roll 12. The pull-in roll 18 has a shaft 18a and an elastic layer 18b formed on the outer periphery of the shaft 18a. The pull-in roll 18 is configured to rotate in conjunction with the drive of the paper feed roll 12 via a connecting member (such as a gear or timing belt) not shown.

[0025] As the paper feed roll 12 rotates, the pull-in roll 18 rotates, and paper P is fed one sheet at a time from the paper feed cassette 16 toward the paper feed roll 12. As shown in FIG. 2A, the paper feed roll 12 has been rotating since before the paper P arrived. As the paper feed roll 12 rotates, the separation roll 14, which is pressed against the paper feed roll 12, is driven to rotate against the brake torque due to the frictional force between the paper feed roll 12 and the separation roll 14 (between the rolls). When a sheet of paper P that has been fed arrives between the rolls, as shown in FIG. 2B, the paper P passes between the rolls and is conveyed in the paper feed direction Y.

[0026] When two sheets of paper P are fed from the paper feed cassette 16 toward the paper feed roll 12, as shown in FIG. 3A, before the arrival of the sheets P1 and P2, the paper feed roll 12 is driven to rotate, and the separation roll 14 is driven to rotate against the brake torque as the paper feed roll 12 rotates. When the two fed sheets P1 and P2 arrive between the rolls, as shown in FIG. 3B, the separation roll 14 comes into contact with the paper feed roll 12 via the two sheets P1 and P2. Because the frictional force acting between the two sheets P1 and P2 is small, the separation roll 14 is stopped by the brake torque and does not follow the rotation of the paper feed roll 12. As a result, the sheet P1 in contact with the paper feed roll 12 passes between the rolls as the paper feed roll 12 rotates, and is conveyed in the paper passage direction Y, while the sheet P2 in contact with the separation roll 14 is not conveyed. This prevents double feeding of sheets P.

[0027] The paper feed roll according to the present invention can be suitably used as the paper feed roll 12 (feed roll), the separation roll 14 (retard roll), the pull-in roll 18 (pickup roll), etc. in the paper feed device 10. The paper feed roll according to the present invention may be either or both of the paper feed roll 12 and the separation roll 14.

[0028] The configuration of the paper feed roll according to the present invention will be described below by taking the paper feed roll 12 as an example. Other paper feed rolls (separation rolls, pull-in rolls) have the same configuration.

[0029] The paper feed roll 12 according to one embodiment of the present invention includes a shaft 12a and an elastic layer 12b formed on the outer peripheral surface of the shaft 12a. The elastic layer 12b is a layer (base layer) that serves as the base of the paper feed roll 10. The elastic layer 12b is a layer that appears on the surface of the paper feed roll 12.

[0030] The shaft 12a may be a solid or hollow (cylindrical) body made of metal or resin. Examples of metal materials include iron, stainless steel, and aluminum. The elastic layer 12b may be bonded to the shaft 12a via an adhesive layer (primer layer). The adhesive, primer, etc. may be made conductive as necessary.

[0031] The elastic layer 12b is made of an elastic material and formed in a roll shape on the outer peripheral surface of the shaft 12a. The elastic layer 12b is composed of a rubber composition containing urethane rubber. The outer peripheral surface of the elastic layer 12b has a surface irregularity formed by a plurality of protrusions. The surface roughness Rz of the outer peripheral surface of the elastic layer 12b is 30 μm or more and 280 μm or less. By having the surface roughness Rz within this range, appropriate surface irregularities are formed on the outer peripheral surface of the elastic layer 12b, ensuring excellent paper transportability. The surface roughness Rz is the ten-point average roughness, which is the average value of values ​​measured at four circumferential locations at the center of the roll axial direction in accordance with JIS B 0601:1982. The ten-point average roughness Rz can be measured using a contact roughness meter.

[0032] The elastic layer 12b has a profile height of 2.0 μm or more and 10 μm or less when the convex surface is observed under a microscope after 30,000 sheets have been passed through in a paper passing test under the following conditions: The profile is measured in the paper passing direction for the surface convex portions seen when observed at 1000x magnification. The profile height is expressed as the average of measurements taken at two points (0° and 180°) in the circumferential direction at the center of the roll axial direction. Environment: 10°C x 10% RH Printer: Load 400 g, paper passing speed 300 mm / sec

[0033] In the present invention, the profile height of the convex surface is set to 2.0 μm or more and 10 μm or less in the paper feed test. In this way, by slightly wearing down the convex portions of the urethane rubber elastic layer 12b through long-term paper feed, depressions (concave portions) are formed in the convex portions. As a result, paper dust adhering to the convex portions is deposited in the concave portions formed by the wear, thereby maintaining the coefficient of friction of the roll surface. Furthermore, glossy paper and coated paper, which are special papers used for printing photographs and the like, are coated with components that impart gloss to the surface. When printing on such coated paper, these components may adhere to the roll surface. Adhesion of these components reduces the coefficient of friction of the roll surface, resulting in paper feed problems. In the present invention, the profile height of the convex surface is set to 2.0 μm or more and 10 μm or less in the paper feed test. In this way, by slightly wearing down the convex portions of the urethane rubber elastic layer 12b, the adhered components can be removed from the convex portions, thereby maintaining the coefficient of friction of the roll surface. For example, by adjusting the ratio of the crosslinking agent and chain extender in the urethane compounding, the convex portions of the urethane rubber elastic layer 12b can be made more susceptible to wear, which allows for such a configuration.

[0034] From the above viewpoint, the profile height is more preferably 2.5 or more, and even more preferably 4.0 or more. When the profile height is 2.5 or more, the durability is more excellent, and when the profile height is 4.0 or more, the durability is particularly excellent.

[0035] The JIS-A hardness of the surface of the elastic layer 12b is preferably 30 degrees or more and 60 degrees or less. If the JIS-A hardness of the surface of the elastic layer is 30 degrees or more and 60 degrees or less, the frictional force during use tends to partially wear down the surface of the protruding portions of the urethane rubber elastic layer 12b, making it easier to form minute recesses on the surface of the protruding portions. From the above viewpoint, the JIS-A hardness of the surface of the elastic layer 12b is more preferably 35 degrees or more and 50 degrees or less.

[0036] The urethane rubber constituting the elastic layer 12b is formed from a polyol and a polyisocyanate. The polyol and the polyisocyanate are not particularly limited as long as they are polyols and polyisocyanates for forming urethane rubber that are used to form the urethane rubber.

[0037] Examples of polyols include polyester polyols, polyether polyols, polycarbonate polyols, and acrylic polyols. Examples of polyester polyols that may be mentioned include polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexylene adipate (PHA), and copolymers of ethylene adipate and butylene adipate (PEA / BA). Examples of polyether polyols include polypropylene glycol (PPG), polytetramethylene glycol (PTMG), ethylene oxide-modified polyols thereof, and polyethylene glycol (PEG).

[0038] Examples of the isocyanate include 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), trimethylhexamethylene diisocyanate (TMHDI), tolylene diisocyanate (TDI), carbodiimide-modified MDI, polymethylene phenyl isocyanate (PAPI), orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), paraphenylene diisocyanate (PDI), lysine diisocyanate methyl ester (LDI), and dimethyl diisocyanate (DDI). These may be used alone as the isocyanate component, or two or more may be used in combination. Among these, 4,4'-diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI) are particularly preferred from the viewpoints of excellent abrasion resistance, suppressing large abrasion of the convex portions, and being suitable for slightly abrading the surfaces of the convex portions due to frictional forces during use.

[0039] The isocyanate may be an NCO-terminated urethane prepolymer obtained by reacting an isocyanate such as MDI with a polyol. The urethane prepolymer used as the isocyanate is NCO-terminated, so that the NCO% is preferably in the range of 5 to 30 mass%. The NCO% is calculated using the following formula:

[0040]

[0041] The amount of isocyanate blended is preferably set so that the NCO index (isocyanate index) is 100 or more, from the viewpoints of easily improving abrasion resistance, easily ensuring strength, and being less prone to settling. The NCO index is more preferably 105 or more, and even more preferably 110 or more. On the other hand, from the viewpoints of not being too hard and being easy to mold, it is preferably set so that the NCO index is 130 or less. The NCO index is more preferably 125 or less, and even more preferably 120 or less. The NCO index is calculated as the equivalent of isocyanate groups relative to 100, the total equivalent of active hydrogen groups (hydroxyl groups, amino groups, etc.) that react with isocyanate groups.

[0042] The urethane composition forming the urethane rubber may contain, as necessary, a chain extender, a crosslinking agent, and a catalyst, as well as a plasticizer, an ionic conductive agent, a foaming agent, a surfactant, a flame retardant, a colorant, a filler, a stabilizer, a mold release agent, and the like.

[0043] The chain extender is a bifunctional compound such as a diol or diamine that can react with polyurethane. A chain extender having a number average molecular weight of 300 or less is preferred. Examples of chain extenders include diols such as 1,4-butanediol (1,4-BD), ethylene glycol (EG), 1,6-hexanediol (1,6-HD), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylene glycol, and triethylene glycol, and aromatic diamines such as 2,2',3,3'-tetrachloro-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diphenylmethane, trimethylene-bis(4-aminobenzoate), and 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane. These chain extenders may be used alone or in combination of two or more. Among these, 1,4-butanediol (1,4-BD), ethylene glycol (EG), 1,6-hexanediol (1,6-HD), etc. are preferred from the viewpoint of ensuring physical properties and easily achieving improved moldability.

[0044] The crosslinking agent is a trifunctional or higher functional compound, such as a triol or triamine, that can react with polyurethane. Those with a number average molecular weight of 300 or less are preferred. Examples of crosslinking agents include trimethylolpropane (TMP), glycerin, pentaerythritol, sorbitol, and 1,2,6-hexanetriol. These may be used alone or in combination as crosslinking agents. Of these, trimethylolpropane (TMP) is preferred from the viewpoint of ensuring physical properties and easily achieving improved moldability.

[0045] In the urethane composition, a relatively low proportion of crosslinker is preferred from the viewpoint of facilitating the formation of fine recesses on the convex surfaces by partially wearing down the convex surfaces of the urethane rubber elastic layer 12b due to frictional forces during use. From the above viewpoints, the blending ratio of the chain extender to the crosslinker in the urethane composition is preferably chain extender / crosslinker = 1.5 or more and 4.5 or less by mass. More preferably, it is 1.7 or more and 4.2 or less, and even more preferably, it is 2.0 or more and 4.0 or less. Furthermore, from the above viewpoints, the blending amounts of the chain extender and the crosslinker may be appropriately adjusted. The blending amount of the chain extender in the urethane composition is preferably within a range of 0.5 to 5.0 parts by mass per 100 parts by mass of the urethane prepolymer. Furthermore, the content of the crosslinker in the urethane composition is preferably within a range of 0.5 to 1.0 part by mass per 100 parts by mass of the urethane prepolymer.

[0046] The catalyst is not particularly limited, and examples thereof include amine compounds such as tertiary amines, organometallic compounds such as organotin compounds, etc. Examples of tertiary amines include trialkylamines such as triethylamine, tetraalkyldiamines such as N,N,N',N'-tetramethyl-1,3-butanediamine, aminoalcohols such as dimethylethanolamine, ethoxylated amines, ethoxylated diamines, ester amines such as bis(diethylethanolamine) adipate, triethylenediamine (TEDA), cyclohexylamine derivatives such as N,N-dimethylcyclohexylamine, morpholine derivatives such as N-methylmorpholine and N-(2-hydroxypropyl)-dimethylmorpholine, and piperazine derivatives such as N,N'-diethyl-2-methylpiperazine and N,N'-bis-(2-hydroxypropyl)-2-methylpiperazine. Examples of organotin compounds include dialkyltin compounds such as dibutyltin dilaurate and dibutyltin di(2-ethylhexoate), as well as stannous 2-ethylcaproate and stannous oleate. These may be used alone or in combination as catalysts. Among these, triethylenediamine (TEDA) is preferred from the viewpoints of resistance to hydrolysis and minimal contamination due to bleeding.

[0047] The catalyst content in the urethane composition is not particularly limited as long as it is within a range that favorably promotes the urethanization reaction. For example, it is preferably within a range of 0.01 to 5 parts by mass, and more preferably within a range of 0.1 to 3 parts by mass, per 100 parts by mass of polyol.

[0048] Examples of plasticizers include polyether esters, adipic acid ether esters, adipic acid polyesters, adipic acid esters, sebacate esters, benzoates, azelates, trimellitates, and phthalates. Among these, polyether esters, adipic acid ether esters, and benzoates are preferred from the viewpoint of excellent compatibility with the polyol of the urethane prepolymer. Of these, polyether esters are particularly preferred.

[0049] The content of the plasticizer is preferably 10 parts by mass or more and 60 parts by mass or less, more preferably 20 parts by mass or more and 55 parts by mass or less, and even more preferably 25 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the urethane prepolymer.

[0050] The thickness of the elastic layer 12b is not particularly limited and may be set appropriately within the range of 2 to 25 mm.

[0051] The elastic layer 12b can be formed by molding using a mold. For example, a core material is coaxially placed in the hollow portion of a roll molding mold, an uncrosslinked rubber composition is injected, and the composition is heated and cured (crosslinked), followed by demolding to form a tubular elastic layer 12b. A molding mold having recesses formed on its inner circumferential surface in shapes corresponding to the protrusions can be used. The paper feed roll 10 can be formed by inserting the shaft 12a into the cylindrically formed elastic layer 12b. Note that the method for imparting a shape to the outer circumferential surface of the elastic layer 12b is not limited to transfer using a mold, and may also be polishing or the like.

[0052] In the paper feed roll 10 configured as described above, the elastic layer 12b is made of a rubber composition containing urethane rubber, and the outer peripheral surface of the elastic layer 12b has a surface irregularity formed by a plurality of protrusions. The surface roughness Rz of the outer peripheral surface of the elastic layer 12b is 30 μm or more and 280 μm or less, and the profile height of the protrusion surface when observed under a microscope after passing 30,000 sheets of paper under the above conditions is 2.0 μm or more and 10 μm or less. With this paper feed roll 10, the frictional force during use partially wears the protrusion surface of the urethane rubber roll, forming fine recesses on the protrusion surface, and paper powder is deposited in these recesses, thereby maintaining the friction coefficient. This maintains the friction coefficient of the roll surface even over long periods of use and improves durability. Furthermore, even when printing on such coated paper, the frictional force during use partially wears the protrusion surface of the urethane rubber roll, removing components adhering to the surface from the protrusions, thereby maintaining the friction coefficient of the roll surface over long periods of use.

[0053] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0054] The present invention will be described in detail below using examples and comparative examples.

[0055] Example 1 Preparation of Urethane Composition 65 parts by mass of polytetramethylene ether glycol (PTMG) and 25 parts by mass of polypropylene glycol (PPG) were vacuum degassed and dehydrated at 80°C for 1 hour, and then 13 parts by mass of isocyanate (TDI) was added and reacted for 1 hour at 80°C under a nitrogen atmosphere to prepare urethane prepolymer A. Next, the prepared urethane prepolymer A was vacuum degassed at 90°C for 30 minutes, and then 2.2 parts by mass of chain extender (1,4-butanediol (1,4-BD)), 0.6 parts by mass of crosslinker (trimethylolpropane (TMP)), 0.01 part by mass of catalyst (triethylenediamine (TEDA)), and 25 parts by mass of plasticizer (polyether ester) were blended with 100 parts by mass of urethane prepolymer A, and the mixture was stirred and mixed under reduced pressure for 2 minutes to prepare an uncrosslinked urethane composition.

[0056] <Preparation of paper feed roll> A core metal (outer diameter φ10 mm) was set coaxially in the through hole of a roll molding die having an uneven structure on the inner peripheral surface, and the prepared urethane composition was poured into the die and subjected to a curing reaction at 140°C for 60 minutes to prepare a paper feed roll in which an elastic layer (thickness 6 mm) was formed on the outer peripheral surface of the shaft.

[0057] Examples 2 to 5 Paper feed rolls were produced in the same manner as in Example 1, except that the blending compositions were changed as shown in Table 2.

[0058] Examples 6 to 11 Paper feed rolls were produced in the same manner as in Example 1, except that the composition was changed to another urethane prepolymer as shown in Table 1 and the blending composition was changed as shown in Table 2.

[0059] Comparative Examples 1 and 2 Paper feed rolls were produced in the same manner as in Example 1, except that the blending compositions were changed as shown in Table 2.

[0060] Comparative Examples 3 to 8 Paper feed rolls were produced in the same manner as in Example 1, except that the composition was changed to other urethane prepolymers as shown in Table 1 and the blending composition was changed as shown in Table 2.

[0061] The materials used are as follows: (Polyether polyol) PTMG: "PTG2000" manufactured by Hodogaya Chemical, Mn=2000 PPG: "Exenol 828" manufactured by AGC, Mn=5000, trifunctional (Plasticizer) Plasticizer (polyether ester plasticizer): "Adeka Cizer RS-1000" manufactured by ADEKA

[0062] The JIS-A hardness and surface roughness Rz of the elastic layer of the fabricated paper feed roll were measured. Furthermore, the surface profile of the convex portions of the elastic layer was measured using a laser microscope. Furthermore, the durability of the fabricated paper feed roll was examined.

[0063] (JIS-A Hardness) In accordance with JIS K 7321, the hardness of the outer peripheral surface of the elastic layer was measured with a type A durometer under a load of 9.8 N.

[0064] (Surface Roughness) In accordance with JIS B 0601:1982, the ten-point average roughness Rz was calculated from the average value of values ​​measured at four points in the circumferential direction at the center of the roll in the axial direction. The ten-point average roughness Rz was measured using a contact-type roughness meter. Measurement speed: 0.3 mm / sec, Measurement length: 4.0 mm, Stylus: 08

[0065] (Surface Profile) In a paper-feeding test under the following conditions, the surface of the protrusions was observed under a microscope after 30,000 sheets had been passed through, and the profile height (μm) was determined. The profile was measured in the paper-feed direction for the surface protrusions seen when observed at 1000x magnification. The profile height was expressed as the average of measurements taken at two points (0° and 180°) in the circumferential direction at the center of the roll axial direction. Enlarged photographs of the protrusion surface and their cross-sectional profiles are shown in Figures 4(a) and (b). Environment: 10°C x 10% RH Printer: 400 g load, paper-feeding speed: 300 mm / sec Paper: Oji Paper Super White Lilac A3 Microscope: Laser microscope (KEYENCE "LASER MICROSCOPE VK-X series" 1000x magnification)

[0066] (Durability) Using the prepared paper feed roll, printing was repeatedly performed until a paper jam occurred, and the number of sheets passed before the jam was measured. After 20,000 sheets were passed, the coefficient of friction of the outer surface of the elastic layer and the amount of wear of the convex portions (calculated from the difference in the height of the convex portions before and after the test) were also measured. The evaluation machine was a Konica Minolta "bizhub C658," and evaluation was performed using Oji Paper's "Super White Lilac A3" in a 10°C x 10% RH environment. Evaluation was based on continuous paper feed durability using an actual machine. When the number of sheets passed before a paper jam due to the paper feed roll occurred was 30,000 or more, it was evaluated as "◎," when it was 20,000 or more but less than 30,000, it was evaluated as "○," when it was 15,000 or more but less than 20,000, it was evaluated as "△," and when it was less than 15,000, it was evaluated as "×."

[0067] (Durability with Coated Paper) Using the prepared paper feed roll, printing was repeatedly performed until a paper jam occurred, and the number of sheets passed before the jam was measured. After 2,000 sheets were passed, the coefficient of friction of the outer surface of the elastic layer and the amount of wear of the convex portions (calculated from the difference in the height of the convex portions before and after the test) were also measured. The evaluation was performed using a Konica Minolta "bizhub C658" printer under a 10°C x 10% RH environment, using Fujifilm Business Innovation's "OS Coated Paper w." The evaluation was based on continuous paper feed durability using an actual printer. The number of sheets passed before a paper jam due to the paper feed roll occurred was evaluated as "◎" if it was 1,000 or more, "○" if it was 700 or more but less than 1,000, "△" if it was 500 or more but less than 700, and "×" if it was less than 500.

[0068]

[0069]

[0070]

[0071] In Examples 1 to 11, the elastic layer is made of urethane rubber and has a surface roughness Rz of 30 μm to 280 μm, and the profile height of the convex surface after a paper feed test of 30,000 sheets is 2.0 μm to 10 μm. In these Examples, no paper jams occurred in the durability test, and the coefficient of friction of the roll surface is maintained even after long-term use, demonstrating excellent durability. Furthermore, even when printing on coated paper, no paper jams occurred up to 500 sheets of paper feed in the durability test, demonstrating that the coefficient of friction of the roll surface is maintained even after long-term use, demonstrating excellent durability.

[0072] FIG. 4 shows an enlarged photograph (a) of the convex surface of the elastic layer in Example 1 and its cross-sectional profile (b) in the paper feed direction (direction of the arrow). The darker areas in the enlarged photograph (a) are fine recesses formed on the convex surface. From the enlarged photograph (a), it can be seen that fine irregularities are formed on the convex surface of the example. The horizontal axis of the cross-sectional profile (b) represents the distance in the direction of the arrow (paper feed direction), and the vertical axis represents the depth. In the cross-sectional profile (b), it can be seen that there are several places along the paper feed direction where the depth suddenly increases and then suddenly decreases, indicating the presence of several recesses. The shear force of the transported paper moves paper dust along the paper feed direction and accumulates in the recesses created by friction. Over long-term use, paper dust generated during paper feed accumulates in the recesses, maintaining the friction coefficient of the roll surface and improving durability. Furthermore, when printing on coated paper, the components coated on the surface of the coated paper adhere to the convex parts of the roll surface, but as the convex parts of the roll surface wear, the adhered components are removed from the convex parts of the roll surface, thereby maintaining the coefficient of friction of the roll surface and improving durability.

[0073] In contrast, in Comparative Examples 1 to 8, the elastic layer was made of urethane rubber and had a surface irregularity with a surface roughness Rz of 30 μm or more and 280 μm or less, and the profile height was less than 2.0 μm. In these Comparative Examples, minute depressions on the surface of the protrusions on which paper dust can accumulate were not formed, and the paper dust reduced the coefficient of friction of the protrusions, resulting in paper jams in the durability test and poor durability. Furthermore, when printing on coated paper, components coated on the surface of the coated paper adhered to the protrusions on the roll surface, and since the protrusions on the roll surface were not worn, the adhered components remained on the protrusions, reducing the coefficient of friction of the protrusions, resulting in paper jams in the durability test up to 500 sheets passed, resulting in poor durability.

[0074] Furthermore, a comparison between the examples reveals that when the profile height is 2.5 or more, the durability is superior, and when the profile height is 4.0 or more, the durability is particularly superior.

[0075] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention.

[0076] 10 Paper feed device 12 Paper feed roll (paper feed roll) 12a Shaft body 12b Elastic layer 14 Separation roll 14a Shaft body 14b Elastic layer 16 Paper feed cassette 18 Pull-in roll 18a Shaft body 18b Elastic layer P, P1, P2 Paper

Claims

1. It comprises a shaft and an elastic layer formed on the outer surface of the shaft, The elastic layer is composed of a rubber composition including urethane rubber. The urethane composition forming the aforementioned urethane rubber contains a chain extender and a crosslinking agent, and the blending ratio of the chain extender and the crosslinking agent in the urethane composition is chain extender / crosslinking agent = 1.5 or more and 4.5 or less. The outer surface of the elastic layer has surface irregularities formed by a plurality of protrusions. The surface roughness Rz of the outer surface of the elastic layer is 30 μm or more and 280 μm or less. A paper feed roll in which, when the surface of the protrusion is observed under a microscope after feeding 30,000 sheets of paper in a paper feeding test under the following conditions, the profile height is between 2.0 μm and 10 μm. Environment: 10℃ x 10%RH Printer: Load 400g, Paper feed speed 300mm / sec

2. The paper feed roll according to claim 1, wherein the JIS-A hardness of the surface of the elastic layer is 30 degrees or more and 60 degrees or less.

3. The paper feed roll according to claim 1 or claim 2, wherein the isocyanate constituting the urethane rubber of the elastic layer is diphenylmethane diisocyanate or tolylene diisocyanate.

4. A paper feed roll according to claim 1 or claim 2, wherein the paper feed roll and / or a separation roll are either one or both.

5. A paper feeding device wherein the paper feeding roll according to claim 1 or claim 2 is either a paper feed roll or a separation roll, or both.

6. The paper feed roll according to claim 1 or claim 2, wherein the blending ratio of the chain extender and the crosslinking agent in the urethane composition is chain extender / crosslinking agent = 1.7 or more and 4.2 or less.