KR102558260B1 - Fluoride-containg lubricant composition for actuator of camera module and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a fluorine-containing lubricant for a camera module actuator and a manufacturing method thereof, wherein the fluorine-containing lubricant is composed of a base oil and a thickener, wherein the base oil has an average molecular weight of 7,100 to 7,500 g/mol, a kinematic viscosity at 20 ° C of 1,700 to 2,100 mm / s, and a kinematic viscosity at 40 ° C of 4 It is a perfluoropolyether (PFPE) oil of 70 to 550 mm / s, and the thickener has an average particle size (D₅₀) is an emulsion-type polytetrafluoroethylene (PTFE) of 4 to 6 nm, and the fluorine-containing lubricant can form a semi-permanent lubricating film with control and durability when used in a ball guide type camera module actuator. Shows the effect.

Description

Fluorine-containing lubricant for camera module actuator and manufacturing method thereof

The present invention relates to a fluorine-containing lubricant for a camera module actuator and a method for manufacturing the same, and more particularly, to a high-performance fluorine-containing lubricant that can be used for movement control of a camera module actuator and a method for manufacturing the same.

An actuator for moving the lens module is provided in the camera module. Such actuators include an AF actuator for shifting a focus position by moving a lens up and down, an OIS actuator for adjusting a lens position by moving a lens in a direction opposite to a camera shake, and the like.

For the smooth operation of the lens module, lubricants such as oil or grease are used. In general, reactive greases such as silicone lubricants or lithium and calcium have been widely used. Also, recently, fluorine-based lubricants have been developed for the purpose of improving control performance, wear resistance and stability, and durability life of lubricants.

Republic of Korea Patent Publication No. 10-2020-0048979 discloses a technique for easily detecting the presence or absence of lubricant application by allowing a fluorescent material to be contained in a fluorine-based lubricant. As such a fluorine-based lubricant, a fluorine-based lubricant including perfluoropolyether (PFPE) oil is used.

In addition, Japanese Unexamined Patent Publication No. 2018-097313 discloses a technique of applying a lubricant between a spherical end surface of a protruding part and a spherical surface of a recessed part in an OIS actuator used for imparting a correction function to an optical unit. In this technology, the performance of the camera module is improved through structural improvement of the actuator.

The applicant has developed a method for producing a lubricant composed of PFPE oil and fluorine resin through Korean Patent Registration No. 10-2038369, and is manufacturing a lubricant having physical properties that can be used in electronic devices. If a manufacturing process for optimizing the physical properties of a lubricant is applied to a camera module actuator by applying such prior art, it is expected that the performance of the actuator that needs to precisely control a plurality of lenses can be further improved.

Republic of Korea Patent Publication No. 10-2020-0048979 Japanese Unexamined Patent Publication No. 2018-097313 Republic of Korea Patent Registration No. 10-2038369

The present invention has been made in view of the prior art as described above, and can improve the performance of the camera module actuator, and in particular, an improved fluorine-based lubricant composition that can solve the problem of driving failure due to temperature change and its manufacturing method. Its object is to provide.

In particular, when applied to a ball guide type actuator, it is intended to provide a fluorine-based lubricant composition that exhibits durability (lubricating stiffness) and forms a semi-permanent lubricating film to improve the performance of the actuator and a manufacturing method thereof.

The fluorine-containing lubricant for a camera module actuator of the present invention to solve the above problems is made of a base oil and a thickener, and the base oil has an average molecular weight of 7,100 to 7,500 g / mol, a kinematic viscosity at 20 ° C of 1,700 to 2,100 mm / s, and a kinematic viscosity at 40 ° C of 470 to 550 It is a perfluoropolyether (PFPE) oil of mm / s, and the thickener is an emulsion type polytetrafluoroethylene (PTFE) having an average particle size (D ₅₀ ) of 4 to 6 nm.

At this time, the fluorine-containing lubricant for the camera module actuator is preferably composed of 66 to 73 mass% of the base oil and 27 to 34 mass% of the thickener.

In addition, the fluorine-containing lubricant for the camera module actuator has a kinematic viscosity of 470 to 550 mm / s at 40 ° C, a penetration of 280 to 320 for 0.1 mm, an oil separation of 2 to 4% by weight at 204 ° C. for 24 hours, an evaporation rate of 0.2% by weight or less at 204 ° C. can be more than f.

The fluorine-containing lubricant for a camera module actuator of the present invention includes a base oil pretreatment step of removing impurities by evaporating perfluoropolyether (PFPE) oil under reduced pressure, preparing a mixture by mixing 66 to 73% by mass of the base oil and 27 to 34% by mass of a thickener, aging the mixture, and a homogenization step of pressurizing and pulverizing the aged mixture using a three-stage roll mill.

At this time, in the step of preparing the mixture, it may be blended by stirring under reduced pressure (vacuum) conditions using a planetary mixer.

Applying the fluorine-containing lubricant for a camera module actuator according to the present invention can improve the performance of the camera module actuator, and in particular, solve the problem of poor driving due to temperature change.

In particular, when applied to a ball guide type actuator, performance of the actuator can be improved by showing durability (lubrication stiffness) and forming a semi-permanent lubricating film.

1 is a cross-sectional view of a ball guide type actuator (a) and a spring type actuator (b) applied to a general camera module.
2 is a process chart showing a process for manufacturing a fluorine-containing lubricant for a camera module actuator according to the present invention.

Hereinafter, the present invention will be described in detail.

The fluorine-containing lubricant of the present invention exhibits properties suitable for application to camera module actuators. Actuators used in the camera module include an AF actuator and an OIS actuator, and as shown in FIG. 1, the actuator may be divided into a ball guide method and a spring method according to a driving method.

Conventionally, a spring-type actuator with excellent productivity has been used, and a silicone-based lubricant has been applied to the spring and used to control the actuator including the spring. However, since recently released cameras such as smartphones have high performance and a folded zoom method is applied, driving speed and accuracy are required, and actuators with low battery consumption and durability are required. Therefore, there is a tendency to change from a spring type actuator to a ball guide type actuator.

Fluorine-based lubricants are used as lubricants applied to balls in the ball guide type actuators. These fluorine based lubricants have excellent drive control capability compared to silicon type lubricants and durability and lifespan when applied to ball guide type actuators. Appears to be able to improve. Therefore, the fluorine-based lubricant of the present invention is optimized to exhibit physical properties applicable to a ball guide type actuator applied to a camera module.

The fluorine-based lubricant is composed of a base oil and a thickener, and additives are sometimes added. At this time, physical properties may vary depending on the components and contents of the base oil and the thickener. In particular, a very small amount of lubricant is used in the ball guide type actuator to which the fluorine-based lubricant is applied. Since lubricating performance must be exhibited with a very small amount of lubricant, the performance of the actuator may change very sensitively to the physical property value of the lubricant.

Table 1 shows the standard performance indicators of actuator lubricants.

item Exam conditions unit Test Methods property value kinematic viscosity 40℃ mm/s ASTM D 445
KSM2014 470-550 100℃ mm/s 44-51 lead 25℃ / 60w 0.1 mm ASTM D 217
KSM2032 270-320 reason
100℃/ 24h weight% ASTM D 6184
KSM2050 2.0-4.0 evaporation 100℃/ 24h weight% ASTM D 972KS M 2037 0.0 149℃/ 24h 0.0 204℃/ 24h 0.2 load capacity RT/1760rpm/10sec kgf ASTM D 2596
KSM2026 800 copper corrosion 100℃/ 24h grade ASTM D 4048
KSM2046 ≤ 1a operating temperature range ℃ - -20 to 260

When applied to a ball guide type actuator, lubricants must maintain an intermediate state that does not clump or separate while increasing the driving performance of the balls, so that driving failures due to temperature changes do not occur. The NLGI grade is determined by penetration according to 60 passes at 25 ° C according to ASTM D4950, as shown in Table 2.

NLGI rating lead appearance 000 445-475 fluid 00 400-430 semi-fluid 0 355-385 very soft One 310-340 Soft 2 265-295 Greece 3 220-250 rigidity 4 175-205 very hard 5 130-160 stiffness 6 85-115 very hard

It was found to be applicable to the actuator when the NLGI grade was 1 or 2, but in addition to the NLGI grade, the change in physical properties for the ambient temperature at which the camera module is used must be minimized, so the evaporation amount at a temperature of up to at least 149 ° C. It is necessary to meet the condition of 0% by weight, and it is necessary to show an evaporation amount of 0.2% by weight or less for 24 hours even at a high temperature of about 200 ° C. In addition, in the case of a ball guide type actuator, there may be limitations in the performance that lubricants must control depending on the performance, size, and weight of the camera lens, and the load capacity must be 800 kgf or more to suit various camera lens conditions. Although it can be applied to actuators when the load capacity is low, the degradation of physical properties may occur depending on the camera lens, resulting in insufficient product reliability. Therefore, sufficient effects can be obtained when applied to actuators only when lubricants that can satisfy various physical property conditions are used.

The applicant has developed a lubricant for electronic devices through Korean Patent Registration No. 10-2038369. The lubricant used PFPE oil as a base oil and PTFE as a thickener. In addition, in order to improve the performance of the lubricant, high-purity oil is produced by removing impurities contained in the oil by performing a pretreatment of evaporating PFPE oil under reduced pressure.

In the present invention, by applying the prior art PFPE oil pretreatment method, high-purity PFPE oil is prepared to improve the physical properties of the lubricant.

As shown in FIG. 2, the fluorine-containing lubricant for the camera module actuator may include a base oil pretreatment step of removing impurities by evaporating PFPE oil under reduced pressure, preparing a mixture by mixing 66 to 73% by mass of the base oil and 27 to 34% by mass of a thickener, aging the mixture, and a homogenization step of pressurizing and pulverizing the aged mixture using a three-stage roll mill.

At this time, the base oil pretreatment step is a process of receiving fluorine oil in a heat source device and removing impurities (nanodust) contained in the fluorine oil by vacuum evaporation through a pressure reducing device, as disclosed in Korean Patent Registration No. 10-2038369. Can be applied.

In the prior art, fluorine oil is evaporated under reduced pressure at 200 to 250 ° C., because it is related to the amount of evaporation of impurities and fluorine oil. In the above temperature range, the reduced-pressure evaporation temperature of 200 to 250 ° C. is set because the emission level of impurities greatly increases along with the amount of self-evaporation of fluorine oil. However, the PFPE oil used in the present invention has an average molecular weight of 7,100 to 7,500 g / mol, a kinematic viscosity at 20 ° C of 1,700 to 2,100 mm / s, and a kinematic viscosity at 40 ° C of 470 to 550 mm / s. It is only 5% by weight, which is excellent in terms of thermal stability of the lubricant, but it was found that the vacuum evaporation temperature needs to be increased for the pretreatment process through vacuum evaporation. Therefore, in the base oil pretreatment step of the present invention, the vacuum evaporation temperature is increased to 260 to 270 ° C. and the vacuum evaporation time is shortened to 30 to 60 minutes to remove impurities evaporated from the heated PFPE oil by suction with a vacuum pump.

Thus, a mixture is formed by mixing the PFPE oil and PTFE prepared through the pretreatment, and aged to prepare an aged mixture. This manufacturing method is the same as the process disclosed in the prior art, but since the purpose of the present invention is to form a fluorine-based lubricant applicable to a ball guide type actuator, the mixing ratio of the base oil and the thickener is adjusted, and the mixing process is optimized to further increase the homogeneity of mixing.

Specifically, in the step of mixing the base oil and the thickener, a planetary mixer is used for stirring. Unlike a general stirrer, homogenous mixing is possible at a relatively high stirring temperature by using a planetary stirrer, and the combined mixture can be easily recovered. The effect can be obtained. Stirring and blending using the planetary stirrer is carried out under reduced pressure (vacuum) conditions of 10 ^-3 to 10 ^-4 torr for 1 to 2 hours at a speed of 150 to 200 rpm at 40 to 50 ° C. It was found that the properties of the lubricant desired in the present invention can be obtained. In the process of varying the stirring conditions, such as slowing down the stirring speed or lowering the temperature, the obtained lubricant did not exhibit physical properties such as durability or lifespan to the extent of being used for actuators.

In addition, in the step of aging the mixture, it is preferable to age at room temperature for 12 to 24 hours. Through the aging process, fine adjustment of the physical properties of the lubricant was found to play an important role in the performance through constant physical properties, and it was found that it was appropriate to complete the aging within 24 hours because productivity would decrease if the aging time was too long.

The aged mixture may be homogenized by pulverizing under pressure using a three-stage roll mill as in the prior art. In the three-stage roll mill, the rotation speed of each roll is set differently, and the particle size of the mixture is reduced through different pressure and transmission force due to the difference in rotation speed and the minute difference between the respective roll mills. Due to the decrease in particle size, the PTFE particles are miniaturized, making it easier for PFPE oil to penetrate, and through this, the lubricating performance of the lubricant is improved. In addition, it is preferable to repeat the homogenization step using the three-stage roll mill 3 to 5 times. That is, the homogenized powder passed through the 3-stage roll mill is put into the 3-stage roll mill again to repeat the same pressure crushing process, thereby reducing the difference in physical properties between batches of the fluorine-based lubricant and improving process reliability.

In addition, the lubricant of the present invention uses PFPE oil having an average molecular weight of 7,100 to 7,500 g / mol as a base oil, a kinematic viscosity of 1,700 to 2,100 mm / s at 20 ° C, and a kinematic viscosity of 470 to 550 mm / s at 40 ° C, and an average particle size (D ₅₀ ) of 4 to 6 nm as a thickener. Mulled PTFE is used. The components of the base oil and the thickener itself are the same as in the prior art, but are different from the base oil and thickener used in the prior art lubricant in that the properties of the components used to optimize the properties of the lubricant are adjusted.

PFPE oil consists of a unit structure of -CF ₂ CF(CF ₃ )O- and a unit structure of -CF ₂ O-, and the physical properties vary according to the molar ratio of each unit structure. Therefore, the performance as a lubricant for PFPE oil of various molar ratios was evaluated, with an average molecular weight of 7,100 to 7,500 g / mol, a kinematic viscosity at 20 ° C of 1,700 to 2,100 mm / s, a kinematic viscosity at 40 ° C of 470 to 550 mm / s, and a kinematic viscosity at 100 ° C of 44 to 51 mm / s. The performance as a lubricant was found to be the best when PFPE oil was used.

In addition, the PTFE is a fluororesin in the form of particles, and is used for various purposes such as ink, paint, coating agent, wax, and lubricant depending on the size, shape, specific surface area, and oil absorption of the particle. Therefore, various types of PTFE were evaluated for use as thickeners.

The PTFE can be divided into an emulsion form, a gel form, and a sintered form according to properties, and the emulsion form of PTFE has been shown to be advantageous in expressing thinkener performance. It was found that the gel form and the sintered form were insufficient in oil absorption when used as a thickener, and in fluorine-based lubricants for actuators, the use of emulsion-type PTFE was evaluated as preferable because the thickener performs a function to control motion and improve durability. In particular, it is preferable to use PTFE having an average particle size (D ₅₀ ) of 4 to 6 nm, and in the above particle size range, the bulk density is 300 to 350 g / L, and the surface area is 7.5 m / g or more.

In order to evaluate whether the fluorine-based lubricant according to the present invention can be used for a camera module actuator, the following test evaluation was conducted.

As the base oil, PFPE oil with properties shown in Table 3 was used, and as a thickener, PTFE particles with properties shown in Table 4 were used. PFPE oil was used after undergoing a base oil pretreatment process in which impurities were removed by evaporation under reduced pressure.

item A B C D E F ISO grade 15 22 100 150 460 460 Average molecular weight (g/mol) 2000 2400 3700 4100 6900 7300 kinematic viscosity
(mm/s) 20℃ 38 60 250 470 1500 1850 40℃ 15 22 80 147 420 510 100℃ 3.2 4.1 10 16 40 47 viscosity index 60 73 108 117 144 148 evaporation
(%) 120℃ 22h 9 6 - - - - 149℃ 22h - 20 2 0.7 0.3 - 204℃ 22h - - 15 1.7 0.9 0.5 Pour point (℃) -58 -50 -35 -30 -25 -20 Density (g/cm at 20℃) 1.87 1.88 1.90 1.91 1.91 1.92 Kinematic viscosity measurement method: ASTM D445
Viscosity index measurement method: ASTM D2270
Evaporation measurement method: ASTM D2595
Pour Point Determination Method: ASTM D97
Density measurement method: ASTM D4052

item One 2 3 4 5 6 7 8 Surface area (㎡/g) >7.5 >7.5 3 2.17 2.17 2.15 2.17 2.16 D50 (μm) 7 5 13 15 4 8 500 500 Bulk density (g/ℓ) 325 325 500 380 260 400 450 450 Melting point (℃) 330±5 330±5 325±5 330±5 330 325 320 320

The 6 types of PFPE oil and 8 types of PTPF particles were mixed and aged in the same ratio as in Table 5, and then pressurized and pulverized 3 times in a 3-stage roll mill to prepare a lubricant.

base oil thickener Base oil: thickener Example 1 A One 70:30 Example 2 B 2 70:30 Example 3 C 3 70:30 Example 4 D 4 70:30 Example 5 E 5 70:30 Example 6 F 6 70:30 Example 7 E 7 70:30 Example 8 F 8 70:30 Example 9 E One 70:30 Example 10 F 2 70:30 Example 11 E One 80:20 Example 12 F 2 80:20

The results of evaluating the physical properties of the lubricants of Examples 1 to 12 are shown in Table 6.

Kinematic viscosity (㎟/s) lead
(0.1mm) reason
(weight%) Evaporation (% by weight) Load capacity (kgf) 40℃ 100℃ 25℃
/60w 100℃/ 24h 100℃
/24h 149℃
/24h 204℃
/24h RT/1760rpm
/10sec Example 1 15 3.2 268 4.9 15 38 70 400 Example 2 22 4.1 272 3.1 8 18 56 400 Example 3 80 10 270 5.4 0.3 1.8 14 500 Example 4 147 16 269 3.6 0.1 0.5 1.7 620 Example 5 420 40 272 8.7 0.0 0.2 0.8 620 Example 6 510 47 270 11.8 0.0 0.0 0.2 620 Example 7 420 40 272 5.1 0.0 0.2 0.8 500 Example 8 510 47 269 5.0 0.0 0.0 0.2 500 Example 9 420 40 278 3.2 0.0 0.2 0.8 620 Example 10 510 47 305 2.1 0.0 0.0 0.2 800 Example 11 420 40 278 5.5 0.0 0.2 0.8 620 Example 12 510 47 282 5.0 0.0 0.0 0.2 800

Looking at the results of Table 6, in the case of the lubricant of Example 10 in which PFPE oil F and PTPF particles 2 were combined, the load carrying capacity was the highest at 800 kgf while satisfying physical properties such as kinematic viscosity, consistency, oil separation rate, and evaporation. From these results, it was found that the fluorine-containing lubricant composed of the base oil and the thickener according to the present invention exhibits physical properties suitable for use in camera module actuators.

Although the present invention has been described through preferred embodiments as described above, it is not limited to the above embodiments, and various modifications and changes can be made by those skilled in the art within the scope of not departing from the spirit of the present invention. Such modifications and variations are to be regarded as falling within the scope of this invention and the appended claims.

Claims (5)

In the fluorine-containing lubricant for a camera module actuator consisting of base oil and a thickener,
The base oil has an average molecular weight of 7,100 to 7,500 g / mol, a kinematic viscosity at 20 ° C of 1,700 to 2,100 mm / s, a kinematic viscosity of 470 to 550 mm / s at 40 ° C, a kinematic viscosity at 100 ° C of 44 to 51 mm / s, and after 22 hours at 204 ° C It is a perfluoropolyether (PFPE) oil with an evaporation mass loss of 0.5% by weight,
The thickener is an emulsion-type polytetrafluoroethylene (PTFE) having an average particle size (D ₅₀ ) of 4 to 6 nm, a bulk density of 300 to 350 g / ℓ, and a surface area of 7.5 m / g or more Fluorine-containing lubricant for camera module actuators.
The method of claim 1,
The fluorine-containing lubricant for the camera module actuator is a fluorine-containing lubricant for a camera module actuator, characterized in that consisting of 66 to 73 mass% of the base oil and 27 to 34 mass% of the thickener.
The method of claim 1,
The fluorine-containing lubricant for the camera module actuator has a kinematic viscosity of 470 to 550 mm / s at 40 ° C, a penetration of 280 to 320 for 0.1 mm, an oil separation of 2 to 4% by weight at 204 ° C. A fluorine-containing lubricant for a camera module actuator, characterized in that.
A method for manufacturing a fluorine-containing lubricant for a camera module actuator according to claim 1,
A base oil pretreatment step of removing impurities by evaporating perfluoropolyether (PFPE) oil under reduced pressure;
Preparing a mixture by mixing 66 to 73% by mass of the base oil and 27 to 34% by mass of the thickener;
aging the mixture;
A homogenization step of pressurizing and pulverizing the aged mixture using a three-stage roll mill;
Method for producing a fluorine-containing lubricant for a camera module actuator comprising a.
The method of claim 4,
The method of preparing a fluorine-containing lubricant for a camera module actuator, characterized in that the step of preparing the mixture is mixed under reduced pressure using a planetary mixer.