Fixation roller

Abstract

To provide a fixation roller having a foamed elastic layer and exhibiting high durability even under high-compression conditions.SOLUTION: The present invention provides a fixation roller including a shaft body 11 and a foamed elastic layer 12 on the outer circumferential surface of the shaft body 11. The foamed elastic layer 12 is formed from a resin composition for a foamed elastic layer containing a millable-type silicone rubber, a crosslinking agent, and a foaming agent. The foamed elastic layer 12 includes, at each of both ends in an axial direction X, at least one tapered portion (13, 14) in which the thickness t of the foamed elastic layer 12 decreases linearly, and the angle θ formed between the surface (13a, 14a) of the tapered portion (13, 14) and the surface 12a of the foamed elastic layer 12 is 120° to 150°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuser roller. [Background technology]

[0002] Various image forming devices using electrophotography are employed in printers such as laser printers and video printers, copiers, facsimiles, and multifunction devices thereof. Electrophotographic image forming devices are equipped with various printing sponge rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, secondary transfer rollers, pressure rollers, paper feed rollers, and fixing rollers, each having a shaft body and an elastic layer formed on the outer circumferential surface thereof.

[0003] Among these sponge rollers, for example, pressure rollers and fixing rollers are compressed to fix toner to a recording medium. When these rollers are compressed under high compression conditions, the end of the rubber layer escapes outward, causing the rubber to break down starting from the area near the core. To solve this problem, for example, Patent Document 1 proposes a roll having an end of the elastic layer in which the radial thickness gradually decreases toward the axial end, the gradually decreasing portion having a curved portion and a tapered portion continuing from the curved portion to the end face of the elastic layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Utility Model Registration No. 3165925 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 does not describe the issues and problems that may arise when the elastic layer is a foamed elastic layer and is compressed at a high compression ratio. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixing roller having a foamed elastic layer, which has high durability even under high compression conditions. [Means for solving the problem]

[0006] The inventors discovered that the problem of rubber being destroyed from the vicinity of the core wire can be solved by providing a portion at the axial end of the foamed elastic layer where the thickness of the foamed elastic layer gradually decreases linearly at a predetermined angle, and thus arrived at the present invention. The present invention is a fixing roller comprising a shaft body and a foamed elastic layer on the outer periphery of the shaft body, the foamed elastic layer being formed from a resin composition for a foamed elastic layer containing millable silicone rubber, a crosslinking agent, and a foaming agent, and the foamed elastic layer has at least one tapered portion at each end of the axial direction, in which the thickness of the foamed elastic layer decreases linearly, and the angle formed between the surface of the tapered portion and the surface of the foamed elastic layer is 120° or more and 150° or less.

[0007] The axial length of the tapered portion is preferably 3% or more and 10% or less of the total length of the foamed elastic layer.

[0008] The blowing agent preferably includes at least one of a chemical blowing agent and unexpanded microballoons.

[0009] The thickness of the foamed elastic layer in the circumferential direction at the center of the axial direction is preferably 3 mm or more and 15 mm or less. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a fixing roller having a foamed elastic layer, which has high durability even under high compression conditions. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an embodiment of a fixing roller of the present invention. [Figure 2] FIG. 10 is a cross-sectional view showing a tapered portion of another embodiment of the fixing roller of the present invention. [Figure 3] FIG. 10 is a cross-sectional view showing a tapered portion of a fixing roller of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Fuser roller] As shown in FIG. 1, a fixing roller 10 of the present invention includes a shaft 11 and a foamed elastic layer 12 on the outer periphery of the shaft 11. Each component will be described in detail below.

[0013] <Shaft> The shaft 11 may preferably be a conductive shaft used in a conventionally known fuser roller. The shaft 11 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. This type of shaft 11 is also generally known as a "core metal."

[0014] Shaft 11 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. Shaft 11 may include, for example, a core made of an insulating resin and a plated layer provided on the core. Such shaft 11 can be obtained, for example, by plating a core made of an insulating resin to make it conductive. The shaft 11 is preferably a cored bar in order to obtain good electrical conductivity.

[0015] The shape of the shaft 11 is preferably, for example, rod-like or tubular. The cross-sectional shape of the shaft 11 may be, for example, circular or elliptical, or may be non-circular such as polygonal. The shaft 11 may be solid or hollow. The outer peripheral surface of the shaft 11 may be subjected to treatment such as cleaning, degreasing, or primer treatment.

[0016] The axial length of shaft 11 is not particularly limited and may be adjusted appropriately depending on the type of image forming apparatus in which it is installed. The diameter of shaft 11 (diameter of the circumscribed circle) is also not particularly limited and may be adjusted appropriately depending on the type of image forming apparatus in which it is installed.

[0017] <Foamed elastic layer> The foamed elastic layer 12 is provided to impart to the fixing roller 10 hardness and elasticity that enable it to be pressed against an object with an appropriate nip width and nip pressure. The foamed elastic layer 12 is formed by vulcanizing a resin composition for a foamed elastic layer on the outer peripheral surface of the shaft body 11. The resin composition for a foamed elastic layer contains at least (A) millable silicone rubber, (B) a crosslinking agent, and (C) a foaming agent.

[0018] (A) Millable silicone rubber The millable silicone rubber is preferably an addition-curing type millable silicone rubber, which preferably contains, for example, at least (a) an organopolysiloxane and (b) a filler.

[0019] (a) Organopolysiloxane (a) Organopolysiloxane is represented by the following average composition formula (1): R 1 n SiO (4-n) / 2 …(1) In formula (1), n ​​is a positive number between 1.95 and 2.05. 1 represents a substituted or unsubstituted monovalent hydrocarbon group, which may be the same or different. The hydrocarbon group preferably has 1 or more and 12 or less carbon atoms, more preferably 1 or more and 8 or less carbon atoms.

[0020] R 1Examples of the R include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl groups, cycloalkyl groups such as cyclohexyl groups, alkenyl groups such as vinyl, allyl, butenyl, and hexenyl groups, aryl groups such as phenyl and tolyl groups, and aralkyl groups such as β-phenylpropyl groups. 1 may be groups in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom, a cyano group, etc. Examples of hydrocarbon groups having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

[0021] The (a) organopolysiloxane is preferably one whose molecular chain terminals are blocked with a trialkylsilyl group such as a trimethylsilyl group, a dialkylaralkylsilyl group such as a dimethylvinylsilyl group, a dialkylhydroxysilyl group such as a dimethylhydroxysilyl group, or a trialalkylsilyl group such as a trivinylsilyl group.

[0022] (a) Organopolysiloxane preferably has two or more alkenyl groups in the molecule. (A) Organopolysiloxane preferably has two or more alkenyl groups in the molecule. 1 Of these, it is preferable that the alkenyl group account for 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less).Vinyl groups are particularly preferable as the alkenyl groups contained in (A) organopolysiloxane.

[0023] (a) Organopolysiloxane can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of a cyclic polysiloxane such as a siloxane trimer or tetramer. (a) Organopolysiloxane may be essentially a linear diorganopolysiloxane, or may be partially branched. (a) Organopolysiloxane may also be a mixture of two or more types with different molecular structures.

[0024] The organopolysiloxane (a) preferably has a kinematic viscosity at 25°C of 100 cSt or more, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. The degree of polymerization of (a) organopolysiloxane is preferably, for example, 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0025] (b) Filler (b) Examples of fillers include silica-based fillers, such as fumed silica and precipitated silica.

[0026] Silica-based fillers include R 2 Si(OR 3 A surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by formula (R) 3 can be preferably used. 2 may be a group having a vinyl group or an amino group, such as a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, or a mercapto group. 3 may be an alkyl group, such as a methyl group or an ethyl group. Silane coupling agents are readily available, for example, under the trade names "KBM1003" and "KBE402" manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a standard method. Commercially available surface-treated silica-based fillers may be used, such as "Zeothix 95" manufactured by JMHUBER Corporation.

[0027] The amount of silica-based filler blended is preferably 11 to 39 parts by mass, and more preferably 15 to 35 parts by mass, per 100 parts by mass of (a) organopolysiloxane. The average particle size of the silica-based filler is preferably 1 to 80 μm, and more preferably 2 to 40 μm. The average particle size of the silica-based filler can be measured as the median size using a particle size distribution analyzer based on laser diffraction.

[0028] Examples of the millable silicone rubber that can be used in the present invention include KE-571-U, KE-1571-U, KE-951-U, KE-541-U, KE-551-U, KE-561-U, KE-961T-U, KE-1541-U, KE-1551-U, KE-941-U, and KE-971T-U manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, examples of millable silicone rubber that can be used include KE-87C-40PU and the like, which contain a conductivity-imparting agent.

[0029] (B) Crosslinker Examples of the crosslinking agent include an addition reaction crosslinking agent and an organic peroxide crosslinking agent. Suitable examples of the addition reaction crosslinking agent include organohydrogenpolysiloxanes, which are known as addition reaction crosslinking agents having two or more SiH groups (SiH bonds) in one molecule. The addition reaction crosslinking agents can be used alone or in combination of two or more. The amount of the addition reaction crosslinking agent to be added is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the resin composition for the foamed elastic layer. When an addition reaction crosslinking agent is used, the organic peroxide crosslinking agent can crosslink the millable silicone rubber by itself, but when used in combination as an auxiliary crosslinking agent for the addition reaction crosslinking agent, the physical properties such as strength and distortion of the resulting fixing roller or pressure roller can be further improved.

[0030] Examples of organic peroxide crosslinking agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The amount of the organic peroxide crosslinking agent is usually 0.1 to 7 parts by mass per 100 parts by mass of the resin composition for the foamed elastic layer. The organic peroxide crosslinking agents can be used alone or in combination of two or more.

[0031] The addition reaction crosslinking agent is preferably used in combination with an addition reaction catalyst. Examples of the addition reaction catalyst include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium catalysts, and rhodium catalysts. The amount of the addition reaction catalyst to be added can be a catalytic amount.

[0032] (C) Foaming agent The foaming agent may be any known foaming agent used to form the foamed elastic layer 12. For example, at least one of a chemical foaming agent and unexpanded microballoons may be used. As for chemical foaming agents, inorganic foaming agents include sodium bicarbonate and ammonium carbonate, while organic foaming agents include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among organic azo compounds, azodicarboxylic acid amide and azobis-isobutyronitrile are preferably used. Azobis-isobutyronitrile is particularly preferably used.

[0033] Examples of unexpanded microballoons include resin microballoons. Resin microballoons preferably have a thermoplastic resin outer shell. Examples of thermoplastic resins constituting the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. Resin microballoons whose shell resin softening temperature is within an appropriate range in accordance with the curing temperature of the silicone rubber are preferably used. Examples of evaporative substances to be encapsulated include hydrocarbons such as butane and isobutane. The average particle size of the unexpanded microballoons is preferably 5 μm or more and 50 μm or less, and more preferably 5 μm or more and 25 μm or less.

[0034] Unexpanded microballoons suitable for the present invention are commercially available as the "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and the "Expancel Series" (manufactured by Expancel Co., Ltd.), etc. Unexpanded resin microballoons suitable for the present invention are selected from resin microballoons that have the function of expanding at a temperature higher than the decomposition temperature of the chemical foaming agent used to form the foamed elastic layer 12. The amount of foaming agent added is preferably 0.5% by mass or more and 6% by mass or less, from the viewpoint of obtaining cells with a low specific gravity and uniform size relative to 100 parts by mass of the resin composition for foamed elastic layer.

[0035] (D)Catalyst The resin composition for the foamed elastic layer may contain a catalyst. The catalyst is preferably an addition reaction catalyst, and examples of the addition reaction catalyst include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. The amount of the addition reaction catalyst to be added may be a catalytic amount.

[0036] The resin composition for the foamed elastic layer may contain various additives, such as conductive agents, auxiliary agents such as chain extenders, catalysts, dispersants, antioxidants, antioxidants, non-silica fillers such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, and solvents.

[0037] The foamed elastic layer 12 is formed on the outer peripheral surface of the shaft body 11 by heat curing and molding simultaneously or successively using a known molding method. The method for forming the foamed elastic layer 12 is not particularly limited and may be continuous vulcanization by extrusion molding, pressing, injection molding, etc. For example, extrusion molding may be selected.

[0038] The method for curing the resin composition for the foamed elastic layer may be any method that can apply the heat required for curing (vulcanization) the resin composition for the foamed elastic layer. The heating temperature when vulcanizing the resin composition for the foamed elastic layer is preferably 100°C or higher and 500°C or lower, and more preferably 120°C or higher and 300°C or lower. The heating time is preferably several seconds to 1 hour or lower, and more preferably 10 seconds to 35 minutes or lower. Furthermore, secondary vulcanization may be performed as necessary.

[0039] (Tapering part) 1, the foamed elastic layer 12 of the fixing roller 10 of this embodiment has at least one tapered portion (13, 14) at each end in the axial direction X, where the thickness t of the foamed elastic layer 12 linearly decreases. In this embodiment, the case where the foamed elastic layer 12 has one tapered portion at each end will be described. The angle θ formed between the surfaces (13a, 14a) of the tapered portions (13, 14) and the surface 12a of the foamed elastic layer 12 is 120° or more and 150° or less. When the angle θ formed between the surfaces (13a, 14a) of the tapered portions (13, 14) and the surface 12a of the foamed elastic layer 12 is 120° or more, localization of stress on the end faces can be suppressed, and when the angle θ is 150° or less, the tapered shape can be maintained. The angle θ is preferably 135° or more and 150° or less. The foamed elastic layer 12 has gradually tapered portions (13, 14), which can prevent the rubber from being destroyed at the ends of the foamed elastic layer 12 under high compression conditions.

[0040] The axial length of the tapered section (13, 14) (W 13 ,W 14 ) are the nip width W of the foamed elastic layer 12, respectively. 12 It is preferably 3% or more and 10% or less, and more preferably 5% or more and 8% or less.

[0041] In another embodiment, as shown in Fig. 2, the gradually tapering portion 13 may be composed of two portions, a first gradually tapering portion 23A and a second gradually tapering portion 23B. Note that Fig. 2 shows only the left side of the foamed elastic layer 12, and the end of the foamed elastic layer 12 on the right side of the page also has a gradually tapering portion composed of two portions. When the tapered portion is composed of two portions, the angle θ2 formed between the surface 23b of the second tapered portion 23B and the surface 12a of the foamed elastic layer 12 is preferably smaller than the angle θ1 formed between the surface 23a of the first tapered portion 23A and the surface 12a of the foamed elastic layer 12. The angle θ2 formed between the surface 23b of the second tapered portion 23B and the surface 12a of the foamed elastic layer 12 can be selected, for example, from the range of 120° to 150°. The angle θ1 is the same as the angle θ described above. In this way, by providing a two-stage tapered portion, stress concentration at the end portion can be more effectively alleviated than in the case of a one-stage tapered portion.

[0042] The thickness t of the foamed elastic layer 12 in the circumferential direction of the axial center portion of the fixing roller 10 is preferably 3 mm or more and 15 mm or less. Note that the thickness in this specification refers to the thickness in the direction perpendicular to the axial direction of the fixing roller 10.

[0043] The outer peripheral surface of the foamed elastic layer 12 may be subjected to a surface treatment such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, itro treatment, or flame treatment in order to improve adhesion to the coating layer described below.

[0044] <Other configurations> The fixing roller of the present invention may have a covering layer provided on the outer periphery of the foamed elastic layer 12. The covering layer is preferably a resin tube. Materials that can be used for the resin tube include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), ETFE (tetrafluoroethylene-ethylene copolymer), PVDF (polyvinylidene fluoride), polyethylene terephthalate, polyamide, polyimide, polycarbonate, polystyrene, ABS, polyurethane, etc. Among these, PFA is preferred. More preferably, the resin tube is made of PFA. The resin tube can be produced by melt extrusion of a resin composition, etc. The resin tube can be attached to the foamed elastic layer 12 provided with the adhesive layer by a known pressurized insertion method or reduced pressure insertion method. The thickness of the resin tube is preferably 30 μm or more and 60 μm or less from the viewpoint of providing a conductive layer on the inner surface.

[0045] As described above, the fixing roller of the present invention has tapered portions at both axial ends of the foamed elastic layer, where the thickness of the foamed elastic layer decreases linearly. This prevents stress during compression from concentrating on the foamed elastic layer near the shaft, which would otherwise cause the foamed elastic layer to be destroyed, thereby making it possible to obtain a fixing roller with high durability even under high compression conditions. [Example]

[0046] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0047] [Example 1] The fixing roller of Example 1 was produced by the following procedure. (Formation of primer layer) An electroless nickel-plated shaft (made of SUM23, diameter 10 mm, length 274.2 mm) was washed with ethanol, and its surface was coated with a silicone primer (product name "Primer No. 16", manufactured by Shin-Etsu Chemical Co., Ltd.). The primer-treated shaft was baked in a gear oven at 150°C for 10 minutes and then cooled at room temperature for at least 30 minutes, forming a primer layer on the outer surface of the shaft.

[0048] (Formation of foamed elastic layer) First, a resin composition for a foamed elastic layer was prepared. The details of the composition are as follows. -Resin composition for foamed elastic layer- (A) 100 parts by mass of addition-curing millable silicone rubber (KE-951-U, manufactured by Shin-Etsu Chemical Co., Ltd.) (B) Crosslinking agent (C-25B, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part by mass (C) Foaming agent (AIBN, manufactured by Otsuka Chemical Co., Ltd.) 2.0 parts by mass (D) 0.5 parts by mass of catalyst (C-25A, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0049] The resin composition for the foamed elastic layer was extrusion molded onto the outer circumferential surface of the shaft. In the extrusion molding, the composition was heated at 180°C for 30 minutes in an infrared heating furnace (IR furnace), and then cured by heating at 200°C for 7 hours in a gear oven (secondary heating). This resulted in the formation of a foamed elastic layer on the outer circumferential surface of the foamed elastic layer. The thickness of the foamed elastic layer was 20 mm.

[0050] (Formation of tapered portion) Next, after the secondary heating, a shaping process was performed. That is, the coarse-foamed elastic layer after the secondary heating was shaped so that the cross section perpendicular to the axial direction of the shaped foamed elastic layer was the same circle along the axial direction. This shaping process was performed by cutting, grinding, and polishing the surface of the coarse-foamed elastic layer after the secondary heating. A cylindrical grinding machine was used as the device for cutting, grinding, and polishing the surface of the coarse-foamed elastic layer after the secondary heating. Note that this shaping process also removes a thin coating that may form on the surface of the coarse-foamed elastic layer after the secondary heating. The tapered portion was formed as described above. The angle θ of the tapered portion formed at the end of the foamed elastic layer was 140°. The thickness of the central portion of the foamed elastic layer was 15 mm.

[0051] [Comparative Example 1] As shown in Fig. 3, the fixing roller was manufactured by polishing the foamed elastic layer so that the θ angle was 90° without providing a tapered portion at the end of the foamed elastic layer in the axial direction X. The thickness of the foamed elastic layer at the center was 15 mm.

[0052] [evaluation] The following evaluations were carried out on the above Examples and Comparative Examples. The evaluation results are shown in Table 1.

[0053] (Durability test) A durability test was carried out on the fixing rollers of Example 1 and Comparative Example 1. The hardness was measured under the following test conditions. <Test conditions> Testing machine: driven testing machine Test temperature: 210℃ Test speed: 200 rpm Push-in amount (pushing rate): 7.5 mm (50%)

[0054] After the test, the fixing roller was evaluated according to the following criteria. The evaluation results are shown in Table 1. <Evaluation criteria> ○: No change in the edge of the foamed elastic layer △: Cracks found at the edge of the foamed elastic layer ×: The foamed elastic layer was destroyed.

[0055] [Table 1]

[0056] As shown in Table 1, the fixing roller of Example 1, which has a tapered portion, showed no change in the end of the foamed elastic layer even after 200 hours of running, demonstrating excellent durability even under high compression conditions. On the other hand, the fixing roller of Comparative Example 1, which does not have a tapered portion, showed cracks in the end of the foamed elastic layer after 50 hours and was destroyed after 200 hours. [Explanation of symbols]

[0057] 10 Fuser roller 11 Shaft 12 Foam elastic layer 12a Surface of foam elastic layer 13, 14 Tapered section 13a, 14a (tapered part) surface 23A First tapered section 23B Second tapering section 23a Surface of the first tapered section 23b Surface of the second tapered portion

Claims

1. A shaft body and a foamed elastic layer on the outer periphery of the shaft body are provided. the foamed elastic layer is formed from a resin composition for a foamed elastic layer, which contains a millable silicone rubber, a crosslinking agent, and a foaming agent; The foamed elastic layer has at least one tapered portion at each of both ends in the axial direction, where the thickness of the foamed elastic layer decreases linearly, The angle formed between the surface of the gradually tapering portion and the surface of the foamed elastic layer is 120° or more and 150° or less.

2. 2. The fixing roller according to claim 1, wherein the axial length of the gradually tapered portion is 3% to 10% of the total length of the foamed elastic layer.

3. 2. The fuser roller of claim 1, wherein the foaming agent comprises at least one of a chemical foaming agent and unexpanded microballoons.

4. 2. The fixing roller according to claim 1, wherein the foamed elastic layer has a circumferential thickness in the axial center portion of the roller of 3 mm to 15 mm.

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