JP2017155201A - Coating composition for dryable lubrication film and dryable lubrication film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition for dryable lubrication film for forming a dryable lubrication film having more excellent low friction and abrasion resistance compared to conventional ones and the dryable lubrication film.SOLUTION: The coating composition for dryable lubrication film is a coating composition for forming a dryable lubrication film excellent in low friction, contains a solid lubricant, spherical resin fine particles having average particle diameter of 2-30 μm and a binder resin as solid components, has percentage content of the solid lubricant and the spherical resin fine particle to the binder resin in a range of 0.3-2.0, and percentage content of the solid lubricant to the spherical resin fine particle in a range of 0.4-3.5.SELECTED DRAWING: None

Description

  The present invention relates to a coating composition for a dry lubricating film, and more particularly to a dry lubricating film coating composition capable of forming a dry lubricating film excellent in low friction and a dry lubricating film thereof.

  Conventionally, a dry lubricating film in which a solid lubricant is dispersed and contained in a resin has been used for the purpose of preventing initial familiarity with OA equipment, home appliances, automobiles, industrial machines, etc., improving seizure properties, and reducing oil. This dry lubricating film is formed by applying a composition containing a solid lubricant and a binder resin to the surface of a metal member or the surface of a rubber or resin member with an appropriate film thickness, and drying or heat curing to form a film. It is what is done.

  The dry lubricating coating cured on the surface of the member is fixed on the surface of the member by the adhesive force of the resin, and exhibits lubricity and wear resistance by the solid lubricant contained in the coating. As the solid lubricant used in the dry lubricating coating composition, molybdenum disulfide, polytetrafluoroethylene, graphite and the like are generally used. As the binder resin, polyamide-imide resin, polyimide resin, epoxy resin, polyurethane resin and the like are widely used. Such a dry lubricating coating has been widely applied up to now, as disclosed in, for example, Patent Document 1.

  However, the characteristics required for the dry lubricating coating are diversified, and the conventional dry lubricating coating has some problems in terms of low slidability and wear resistance. In particular, in recent years, low load load and low friction in the sliding form region in surface sliding are often required, and a dry lubricating film having even more excellent low friction and wear resistance is desired. ing.

JP-A-7-97517 Japanese Patent Laid-Open No. 10-7520

  The present invention has been proposed in view of such circumstances, and a coating composition for a dry lubricating film for forming a dry lubricating film having a lower friction and wear resistance that is more excellent than conventional ones. It is an object of the present invention to provide a product and a dry lubricating film thereof.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, the dry lubricant film in which the solid lubricant and the spherical resin fine particles are dispersed in the binder resin and the content ratio of these components is in a specific range achieves a low coefficient of friction and a sliding The inventors have found that the amount of wear during movement is small, and have completed the present invention.

  (1) A first invention of the present invention is a coating composition for forming a dry lubricating film excellent in low friction, and has a solid lubricant as a solid component and an average particle diameter of 2 to 30 μm. A spherical resin fine particle and a binder resin, the solid lubricant with respect to the binder resin and the content ratio of the spherical resin fine particles are in the range of 0.3 to 2.0, the solid lubrication with respect to the spherical resin fine particles It is a coating composition for dry lubricating coatings in which the content ratio of the agent is in the range of 0.4 to 3.5.

  (2) According to a second aspect of the present invention, in the first aspect, the spherical resin fine particles are in a ratio of 6 parts by mass to 47 parts by mass with respect to 100 parts by mass of the total solids contained in the coating composition. It is a coating composition for a dry lubricating film.

  (3) According to a third aspect of the present invention, in the first or second aspect, the solid lubricant is 6 parts by mass to 47 parts by mass with respect to 100 parts by mass in total of solids contained in the coating composition. It is a coating composition for dry lubricating films, contained in a proportion of

  (4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the binder resin is 33 parts by mass to 77 parts by mass with respect to a total solid content of 100 parts by mass contained in the coating composition. It is a coating composition for a dry lubricating film, contained in a proportion by mass.

  (5) A fifth invention of the present invention comprises a solid lubricant, spherical resin fine particles having an average particle diameter of 2 μm to 30 μm, and a binder resin, and the solid lubricant and the spherical resin for the binder resin The dry lubricating film has a content ratio of fine particles in the range of 0.3 to 2.0, and a content ratio of the solid lubricant to the spherical resin fine particles in a range of 0.4 to 3.5.

  (6) A sixth invention of the present invention is the dry lubricating film according to the fifth invention, wherein the surface roughness is 0.9 or more.

  ADVANTAGE OF THE INVENTION According to this invention, the coating composition for dry lubricant films for forming the dry lubricant film which has the further outstanding low friction property and abrasion resistance, and its dry lubricant film can be provided.

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

<< 1. Dry Lubricant Coating Composition >>
The dry lubricating coating composition (hereinafter also simply referred to as “coating composition”) according to the present embodiment is a coating composition for forming a dry lubricating coating excellent in low friction.

  Specifically, the coating composition contains, as solid content, a solid lubricant, spherical resin fine particles having an average particle diameter of 2 μm to 30 μm, and a binder resin, and is a volatile component, and the binder resin Contains an organic solvent for dissolving the solvent. In this coating composition, the content ratio of the solid lubricant and spherical resin fine particles to the binder resin ((solid lubricant + spherical resin fine particles) / binder resin) is in the range of 0.3 to 2.0, and spherical The content ratio of the solid lubricant to the resin fine particles (solid lubricant / spherical resin fine particles) is in the range of 0.4 to 3.5.

<1-1. Constituents>
[(A) Solid lubricant]
(A) The solid lubricant is not particularly limited. For example, polytetrafluoroethylene (PTFE), graphite, molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), boron nitride (BN) , Melamine cyanurate (MCA) and the like. Among them, it is particularly preferable to use polytetrafluoroethylene from the viewpoints of exhibiting more excellent low friction properties and excellent chemical stability. These solid lubricants can be used alone or in combination of two or more.

  As content of a solid lubricant, it is preferable that it is the range of 6 mass parts-47 mass parts with respect to the solid content total 100 mass parts contained in a coating composition, and it is the range of 10 mass parts-40 mass parts. It is more preferable, and it is especially preferable that it is 15-35 mass parts. When the content of the solid lubricant is less than 6 parts by mass with respect to 100 parts by mass of the total solid content, the friction reducing effect may not be sufficiently exhibited. On the other hand, when the content exceeds 47 parts by mass, the solid lubricant is formed. There is a possibility that the wear amount of the coating film increases and the excellent wear resistance may not be exhibited.

[(B) Spherical resin fine particles]
(B) The spherical resin fine particles are resin fine particles having a spherical shape and an average particle diameter of 2 μm to 30 μm. Thus, by including spherical resin fine particles in a predetermined ratio, the surface roughness Ra of the dry lubricating film to be formed can be increased, and contact with parts such as metal parts that are mating materials during sliding is possible. A low friction coefficient can be realized by reducing the area.

  With respect to the average particle size of the spherical resin fine particles, if the average particle size is less than 2 μm, the surface roughness of the dry lubricating coating does not increase effectively, and the contact area with the mating material increases and exhibits a sufficient friction reducing effect. It may not be. On the other hand, when the average particle size exceeds 30 μm, the amount of coating wear increases and the wear resistance decreases. The average particle size can be measured using, for example, a laser diffraction particle size analyzer.

  Specifically, examples of the types of spherical resin fine particles include acrylic resin, nylon 12 resin, nylon 6 resin, melamine resin, and polyethylene resin. Among them, it is particularly preferable to use acrylic resin and nylon 12 resin because they can exhibit more excellent low friction. These spherical resin fine particles can be used singly or in combination of two or more.

  The content of the spherical resin fine particles is preferably in the range of 6 to 47 parts by mass with respect to the total solid content of 100 parts by mass contained in the coating composition, and is preferably in the range of 10 to 40 parts by mass. It is more preferable, and it is especially preferable that it is 15-35 mass parts. As in the case of the solid lubricant, if the content of the spherical resin fine particles is less than 6 parts by mass with respect to the total solid content of 100 parts by mass, the friction reducing effect may not be sufficiently exhibited, When the amount exceeds 47 parts by mass, the amount of wear of the formed film increases and there is a possibility that excellent wear resistance may not be exhibited.

  In addition, regarding such spherical resin fine particles, a technology to be applied as a component contained in a dry lubricating film has been found up to the present time as a slip material, in particular, a technology for blending in cosmetics (see, for example, Patent Document 2). Has not been found.

[(C) Binder resin]
(C) The binder resin is not particularly limited. For example, polyamideimide resin, urethane resin, epoxy resin, phenol resin, acrylic resin, silicone resin, silicone polyester resin, melamine resin, polyimide resin, polyether mon Phon resin, polyether ether ketone resin, etc. are mentioned. Among these, a binder resin containing a polyamide-imide resin is particularly preferable in terms of good wear resistance and high adhesion to various metal substrates. These binder resins can be used alone or in combination of two or more.

  As content of binder resin, it is preferable that it is the range of 33 mass parts-77 mass parts with respect to 100 mass parts of solid content total contained in a coating composition, and it is the range of 40 mass parts-60 mass parts. Is more preferable, and about 50 parts by mass is particularly preferable. If the content of the binder resin is less than 33 parts by mass with respect to 100 parts by mass of the total solid content, the amount of wear of the formed film increases, and excellent wear resistance may not be exhibited. If it exceeds 77 parts by mass, the content of the solid lubricant and spherical resin fine particles is relatively reduced, and the friction reducing effect may not be sufficiently exhibited.

[(D) Organic solvent]
(D) The organic solvent is for dissolving the above-described binder resin. The organic solvent is preferably selected in consideration of the dissolving power with respect to the binder resin to be used, drying property, and the like. Specifically, for example, when a polyamideimide resin is used as a binder resin, an organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, cyclopentanone or the like is used. Can be mentioned. These organic solvents can be used alone or in combination of two or more.

[(E) Other additives]
Moreover, the coating composition which concerns on this Embodiment can contain a various additive component as needed. Specifically, the additive is not particularly limited. For example, paint additives such as an anti-settling agent, a wetting and dispersing agent, an antifoaming agent, and a surface conditioner can be used.

<1-2. About the content ratio>
In the coating composition according to the present embodiment, the content ratio of (A) solid lubricant and (B) spherical resin fine particles to (C) binder resin (([A] + [B]) / [C]) Is in the range of 0.3 to 2.0.

  Here, the descriptions [A], [B], and [C] are respectively the contents in the solid content of (A) solid lubricant, (B) spherical resin fine particles, and (C) binder resin ( Part by mass). The same applies to the following).

  In the above-mentioned preferable content range, the content ratio of the constituent component represented by ([A] + [B]) / [C] is in the range of 0.3 to 2.0, so that excellent friction reduction is achieved. While exhibiting the effect, it is possible to form a dry lubricating coating with high wear resistance while suppressing the amount of coating wear. When the content ratio of the constituent component represented by ([A] + [B]) / [C] is less than 0.3, the friction reducing effect is hardly exhibited. On the other hand, when it exceeds 2.0, although the low friction coefficient is exhibited, the amount of coating wear increases.

  In addition, the content ratio of the component represented by ([A] + [B]) / [C] is more preferably in the range of 0.5 to 1.5, and is about 1.0. Is particularly preferred.

  Moreover, in the coating composition which concerns on this Embodiment, the content ratio ([A] / [B]) of (A) solid lubricant with respect to (B) spherical resin fine particle is the range of 0.4-3.5. It is.

  In the range of the preferred content described above, the content ratio of the constituent component represented by [A] / [B] is in the range of 0.4 to 3.5, thereby exhibiting an excellent friction reducing effect, A dry lubricating coating with high wear resistance can be formed while suppressing the amount of coating wear. When the content ratio of the constituent component represented by [A] / [B] is less than 0.4, the spherical resin fine particles contained in the dry lubricating coating are significantly removed by sliding, and the amount of coating wear increases. On the other hand, if the content ratio exceeds 3.5, the surface roughness Ra of the dry lubricating coating is reduced, and as a result, the contact area with the component that is the counterpart material during sliding increases, and a friction reducing effect appears. It becomes difficult.

  In addition, as a content rate of the structural component represented by [A] / [B], it is more preferable that it is the range of 0.7-2.5, and it is especially preferable that it is about 1.0.

≪2. Process for producing dry lubricating coating composition >>
It does not specifically limit as a manufacturing method of the coating composition which concerns on this Embodiment, It can manufacture by a conventionally well-known method.

  Specifically, it can be produced by blending and kneading a binder resin, solid lubricant, spherical resin fine particles, which are solid components, and an organic solvent, which is a volatile component, at a predetermined ratio. At this time, it is important that the solid lubricant and the spherical resin fine particles are uniformly dispersed in the binder resin uniformly dissolved by the organic solvent.

  For example, as a method for producing this coating composition, first, among the total solid content of 100 parts by mass, the binder resin is preferably 33 parts by mass to 77 parts by mass, the solid lubricant is 6 parts by mass to 47 parts by mass, and spherical. The resin fine particles are weighed so as to have a ratio of 6 parts by mass to 47 parts by mass. Moreover, the organic solvent which is a volatile component is measured so that it may become a ratio of 55 mass parts-900 mass parts with respect to 100 mass parts of solid content total, for example according to the kind and content of binder resin.

  Next, an organic solvent is charged into the stirring vessel, and then a binder resin, a solid lubricant, and spherical resin fine particles are charged, and a rotary stirrer such as a dissolver type stirrer is dissolved until these materials are uniformly dissolved. To stir. Thereafter, using a sand mill type, three roll type dispersing machine or the like, a dispersion treatment for uniformly dispersing the solid lubricant and the spherical resin fine particles in the binder resin is performed. In addition, it is good also as a coating composition by diluting by adding an organic solvent after dispersion | distribution.

≪3. Formation of dry lubricating film by coating composition >>
As described above, the coating composition according to the present embodiment is for forming a dry lubricating film, and this coating composition is applied to an object to be coated, and then subjected to a curing treatment. By applying, a dry lubricating film can be formed.

<3-1. Method for forming dry lubricating film>
(Coating)
The material to be coated is not particularly limited, and examples thereof include a metal member, a rubber member, a resin member, and the like, and a coating composition can be formed on the surface of these members to form a film. In addition, by selecting the binder resin described above according to the type of member to be coated, it is possible to form a film having high adhesion to any coated material, and to reduce the friction coefficient. The film can be effectively reduced.

(Application method)
The method of applying the coating composition to the object to be coated is particularly limited. For example, air spray coating, dipping coating, brush coating, tumbling by spraying, and screen printing are the same as in general coating materials. Or the like. The selection of these coating methods can be determined according to the shape of the object to be coated and the processing quantity.

  In addition, before apply | coating a coating composition to a to-be-coated object, the degreasing process with respect to the to-be-coated object, the surface treatment for improving the adhesiveness of a film, or a washing process can be performed.

(Dry lubricating film thickness)
The film thickness of the dry lubricating film to be formed is not particularly limited, and may be appropriately determined according to the use of the article to be coated. For example, it is preferably about 5 μm to 50 μm, and 10 μm to 15 μm. More preferably, it is about.

  In applying the coating composition to an object to be coated, a dry film obtained by curing the coating film (dry lubricating coating composition) by means of heating or the like has a desired film thickness (dry film thickness). Thus, it is preferable to apply after determining the coating amount.

(Curing treatment)
The curing treatment of the coating film formed by applying the coating composition to the object to be coated can be performed by a normal coating film baking technique. Specifically, for example, the coating film can be cured by baking the coating film by performing hot air heating, infrared heating, high-frequency heating, or the like. Thus, the film obtained by curing the coating film becomes a dry lubricating film.

  More specifically, the firing conditions for curing the coating film are not particularly limited, and can be determined according to the composition of the binder resin or the like in the used coating composition. For example, when a polyamide-imide resin is used as the binder resin, the curing temperature is preferably in the range of 100 ° C. to 300 ° C., more preferably in the range of 150 ° C. to 280 ° C., these curing temperatures. It can set suitably in the range of and can bake. Moreover, it does not specifically limit as baking processing time (curing time), For example, it can set suitably in the range of 10 minutes-60 minutes, and it is more preferable to set it as about 30 minutes-60 minutes.

<3-2. Dry lubricating coating>
A dry lubricating film can be formed by applying and curing the coating composition for a dry lubricating film on the surface of an object to be coated such as a metal member as described above. Specifically, the dry lubricating film formed by the coating composition according to the present embodiment is a film containing a solid lubricant, fine spherical resin particles having an average particle diameter of 2 μm to 30 μm, and a binder resin. The content ratio of the solid lubricant and the spherical resin fine particles to the binder resin is in the range of 0.3 to 2.0, and the content ratio of the solid lubricant to the spherical resin fine particles is in the range of 0.4 to 3.5. .

  According to such a dry lubricating coating, the friction coefficient is low and excellent low friction properties are exhibited, and the amount of wear is small even when sliding with a mating material such as a metal part and stable over a long period of time. In addition, the coating state is maintained and the wear resistance is excellent.

  The dry lubricating film is not particularly limited, but the surface roughness (Ra) is preferably 0.9 or more, more preferably 1.0 or more, and particularly preferably 1.3 or more. preferable. The larger the surface roughness of the dry lubricating coating, the smaller the contact area between the coating and the sliding material, and the effect of reducing friction is more effectively exhibited. The upper limit of the surface roughness is not particularly limited, but is preferably 3.0 or less, more preferably 2.5 or less, and particularly preferably 2.0 or less. If the surface roughness is too large, the spherical resin fine particles are likely to fall off due to sliding, and the amount of wear of the coating may increase. In addition, the surface roughness (Ra) of the dry lubricating film can be measured using a surface roughness meter.

  EXAMPLES Hereinafter, although the Example and comparative example of this invention are shown and this invention is demonstrated more concretely, this invention is not limited to these Examples and comparative examples.

≪Example, comparative example≫
A dry lubricating coating composition was produced, and the resulting coating composition was applied to an object to be coated (steel plate) and cured to form a dry lubricating coating, and a frictional wear test was performed on the dry lubricating coating. . The confirmation items of the friction and wear test were the coefficient of friction and the amount of wear of the dry lubricating coating.

[Production of coating composition for dry lubricating coating]
Polyamideimide resin as a binder resin, polytetrafluoroethylene (PTFE) as a solid lubricant, and acrylic resin and nylon 12 resin as spherical resin fine particles are weighed in proportions by mass shown in Tables 1 and 2 below. did. Also, an organic solvent (N-methyl-2-pyrrolidone and xylene) in the same amount as the total amount of these solid components was prepared, mixed with the solid components, and dissolved. Furthermore, a fluorine-based surfactant, a silicone-based antifoaming agent, and a silicone-based surface conditioner were added as additives, and each component was sufficiently stirred and dispersed.

  When stirring and dispersing, kneading was performed using a bead mill. As stirring and dispersing conditions by the bead mill, φ1.5 zirconia beads were used as a dispersion medium, 80% filled with respect to a vessel capacity of 1.4 L, and 1-pass dispersion treatment was performed at a flow rate of 0.4 mL / min. Thereby, a coating composition for a dry lubricating film was produced.

[Formation of dry lubricating film]
Next, an SPCC-SB steel plate (length 100 mm, width 50 mm, thickness 1 mm, # 240 polished product) was used as an object to be coated, and the resulting coating composition was applied to the surface of the steel sheet by air spray coating. Uniform application. Subsequently, the steel sheet on which the coating film was formed was placed in a hot air circulating furnace, and the coating film was thermally cured under conditions of a firing temperature of 230 ° C. and a firing time of 40 minutes, thereby forming a dry lubricating coating. The film thickness of the dry lubricating coating was 10 μm.

  In addition, the surface roughness Ra of the obtained dry lubricating coating was measured using a surface roughness meter (Taylor Hobson, Form Talysurf S4F). Table 3 also shows the measurement results.

≪Evaluation test, evaluation result≫
[Friction and wear test]
The friction coefficient of the formed dry lubricating coating was measured using a friction and wear tester (friction player) (manufactured by Reska Co., Ltd., friction player FRP-2100). The setting conditions for the friction player test were SUJ-2 10 mmφ balls, the load was 200 g, the sliding speed was 0.1 m / s (rotating circle diameter: φ20 mm, rotating speed: 95.5 rpm), and the measurement time was 30 minutes. .

  The average friction coefficient of each of the dry lubricating coatings of Examples and Comparative Examples obtained by the frictional wear test and the sliding trace of the dry lubricating coating after the test were measured as a wear amount by a surface roughness meter.

[Evaluation results]
Tables 1 and 2 below collectively show the solid content compositions (compositions of the dry lubricating film) of the coating compositions produced in Examples and Comparative Examples, and the evaluation results thereof.

  From the results shown in Table 1 and Table 2, the dry lubricant film containing the solid lubricant, the spherical resin fine particles, and the binder resin, and containing those constituent components in a specific ratio has a low friction coefficient, Further, it can be seen that the wear depth of the coating film is also reduced, which is excellent in low friction properties and wear resistance.

  Specifically, when Examples 1 to 3 and Comparative Examples 4 and 5 are compared, the ratio of the solid lubricant and the spherical resin fine particles is constant at 1.0, and the content ratio of the binder resin , The ratio represented by (solid lubricant + spherical resin fine particles) / binder resin is in the range of 0.3 to 2.0 in Examples 1 to 3, and 0. In Comparative Examples 4 and 5, respectively. 2 and 2.5. As a result, in the dry lubricating coating of Examples 1 to 3, the wear coefficient was low and the wear amount was small and the wear resistance was excellent, whereas in the dry lubricating coating of Comparative Example 4, the wear amount was Although it was small, the coefficient of friction was as large as 0.32 and the frictional property was inferior. In the dry lubricating film of Comparative Example 5, although the friction coefficient was relatively low, the wear depth was 5.2 μm and the wear resistance was high. It was inferior in nature.

  Further, when Example 1, Example 4, Example 5, and Comparative Examples 1 to 3 are compared, the content ratio of the binder resin ((solid lubricant + spherical resin fine particles) / binder resin) is 1. When the content ratio between the solid lubricant and the spherical resin fine particles is changed with 0 being constant, the ratio represented by the solid lubricant / spherical resin fine particles is 0.4 to 2.3 in Examples 1, 4, and 5. In Comparative Examples 1 to 3, they were 0, 4.0, and 0.3, respectively. As a result, the dry lubricating coatings of Examples 1, 4, and 5 had a low wear coefficient and a small amount of wear and excellent wear resistance, whereas the dry lubricating coatings of Comparative Examples 1 and 3 were spherical. The resin fine particles fall off due to sliding, and the wear amount increases, resulting in poor wear resistance. In the dry lubricating coating of Comparative Example 2, the surface roughness of the coating is small and the contact area with the counterpart material is large. As a result, the coefficient of friction was increased and the friction was inferior.

  Furthermore, from the results of Example 1 and Example 6, it was found that the spherical resin fine particles have the same excellent low friction and wear resistance regardless of whether the average particle size is small or large. It was.

Claims (6)

A coating composition for forming a dry lubricating film excellent in low friction,
As a solid component, containing a solid lubricant, spherical resin fine particles having an average particle diameter of 2 μm to 30 μm, and a binder resin,
The content ratio of the solid lubricant and the spherical resin fine particles to the binder resin is in the range of 0.3 to 2.0, and the content ratio of the solid lubricant to the spherical resin fine particles is 0.4 to 3.5. A coating composition for a dry lubricating coating that is in the range. The coating composition for a dry lubricating film according to claim 1, wherein the spherical resin fine particles are contained in a ratio of 6 parts by mass to 47 parts by mass with respect to 100 parts by mass of the total solid content contained in the coating composition. The dry lubricant film coating composition according to claim 1 or 2, wherein the solid lubricant is contained in a ratio of 6 parts by mass to 47 parts by mass with respect to 100 parts by mass of the total solid content contained in the coating composition. . The dry lubricant film according to any one of claims 1 to 3, wherein the binder resin is contained in a ratio of 33 parts by mass to 77 parts by mass with respect to 100 parts by mass of the total solid content contained in the coating composition. Coating composition. A solid lubricant, spherical resin fine particles having an average particle diameter of 2 μm to 30 μm, and a binder resin,
The content ratio of the solid lubricant and the spherical resin fine particles to the binder resin is in the range of 0.3 to 2.0, and the content ratio of the solid lubricant to the spherical resin fine particles is 0.4 to 3.5. The range is a dry lubricating coating. The dry lubricating film according to claim 5, wherein the surface roughness is 0.9 or more.