JP2010106165A - Liquid crystalline resin composition for injection molding, molded item obtained by molding the resin composition, and camera module comprising the molded item - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology suppressing fibrillation of a surface of a molded item to prevent deterioration of performance of the molded item, even when performing ultrasonic cleaning of the molded item including a liquid crystalline resin, as the ultrasonic cleaning itself for cleaning the molded item is known to fibrillate the surface of the molded item of the liquid crystalline resin and to cause new dropouts (dirt), and also these tiny dirt and dust, etc., are known to deteriorate performance of the molded item, such as optical characteristics when deposited on the molded item. <P>SOLUTION: A difference between a surface roughness Ra of the molded item obtained by injection molding of the liquid crystalline resin composition including silica with an average primary particle size of 5 μm or less and a surface roughness Ra of a mold is adjusted to 0.1 mm or less. The silica used preferably has the average primary particle size of 0.7 μm or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystalline resin composition for injection molding and a molded body formed by molding the resin composition.

  A group of plastics called engineering plastics has high strength and is being replaced by metal parts. Among them, a group of plastics called liquid crystalline resins melts while maintaining the crystal structure, so the volume changes between melting and solidification due to the high strength based on the crystal structure and the fact that the crystal structure does not change significantly during solidification. There is an advantage that the molding shrinkage is small and the dimensional accuracy of the molded product is excellent.

  Taking advantage of such excellent dimensional accuracy, it is used for precision instrument parts. In the case of precision equipment, especially optical equipment with a lens, slight dust, dust, etc. affect the performance of the equipment. For example, parts used in optical equipment such as camera modules, when small dust, oil, or dust adheres to the lens, significantly deteriorates the optical characteristics, and satisfactory performance cannot be obtained. Ultrasonic cleaning removes small dust, oil, dust, etc. adhering to the surface.

  However, the liquid crystalline resin is a resin whose surface is relatively easily fibrillated because the molecular orientation is particularly large at the surface portion. In the case of a liquid crystalline resin molded product, the ultrasonic cleaning itself for cleaning itself fibrillates the surface of the liquid crystalline resin molded product, and becomes a cause of new fallout (dust). Accordingly, there is a demand for a liquid crystalline resin material whose surface is not fibrillated by ordinary ultrasonic cleaning.

  As a resin molded body having improved surface characteristics, it is a resin molded body containing a liquid crystalline polymer and a fibrous filler, and an increase in surface roughness Ra value obtained by a specific surface tape peel test is 0.4 μm or less. There has been disclosed a resin molded body characterized by having a flat portion.

  According to the method described in Patent Document 1, it is useful as a component of an electric / electronic device or an optical device, and can prevent the generation of surface particles (foreign matter). Thus, when the technique described in Patent Document 1 is used, the surface characteristics can be improved.

  However, as described in the Examples of Patent Document 1, the generation of foreign matter in Patent Document 1 is a foreign matter that occurs when the surface is washed by gently stirring in pure water for 1 minute. Therefore, in the improvement of the surface characteristics by the method described in Patent Document 1, a satisfactory result cannot be obtained with respect to suppression of fibrillation during ultrasonic cleaning, which is the object of the present invention. That is, in the method described in Patent Document 1, when the resin molded body is exposed to severe conditions such as ultrasonic cleaning, a large amount of foreign matter is generated.

Furthermore, since the injection-molded product has a particularly large molecular orientation at the surface portion, surface fibrillation is likely to occur, and fluffing is likely when ultrasonic cleaning is performed. For this reason, there is a demand for a technique for improving surface characteristics that can be applied to injection molded articles.
JP 2008-239950 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique for suppressing fibrillation on the surface of a molded body even when the molded body containing a liquid crystalline resin is subjected to ultrasonic cleaning. It is in.

  The inventors of the present invention have made extensive studies in order to solve the above problems. As a result, by using a liquid crystalline resin composition containing silica having an average primary particle size of 5 μm or less, the difference between the surface roughness Ra of the injection mold and the surface roughness Ra of the obtained molded article is within a specific range. It has been found that it can be easily controlled and the above-mentioned problems can be solved, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A liquid crystalline resin composition for injection molding containing silica having an average primary particle size of 5 μm or less.

  (2) The liquid crystalline resin composition for injection molding according to (1), wherein the average primary particle size of the silica is 0.7 μm or less.

  (3) A difference in surface roughness between the mold surface roughness Ra and the molded body surface roughness Ra, which is obtained by injection molding the liquid crystalline resin composition for injection molding described in (1) or (2). A molded product having a thickness of 0.1 mm or less.

  (4) The molded product according to (3), wherein the difference in surface roughness is 0.03 mm or less.

  (5) A camera module comprising the molded article according to (3) or (4).

  According to the present invention, the difference between the surface roughness Ra of a molded product obtained by injection molding a liquid crystalline resin composition containing silica having a specific average primary particle size and the surface roughness Ra of a mold surface used for injection molding. By adjusting the thickness to 0.1 mm or less, the surface characteristics of the molded body can be improved. As a result, even if the obtained molded body is subjected to ultrasonic cleaning, the surface is not fibrillated, and adverse effects on the electronic machine or the like caused by the fibrillation can be suppressed.

  Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

  The present invention provides a surface roughness Ra of a molded article formed by molding a liquid crystalline resin composition for injection molding containing silica having an average primary particle size of 5 μm or less (hereinafter sometimes simply referred to as “liquid crystalline resin composition”). The difference between the surface roughness Ra of the injection mold and the injection mold is adjusted to 0.1 mm or less. That is, by using a liquid crystalline resin composition for injection molding containing silica having an average primary particle size of 5 μm or less as a molding material, the surface of the resulting molded body is not fibrillated even by ultrasonic cleaning. The effect is obtained. The molded body surface roughness refers to the surface roughness Ra of the molded body before ultrasonic cleaning, and the average primary particle size of silica can be measured by laser diffraction particle size distribution measurement.

<Liquid crystal resin composition>
The liquid crystalline resin composition contains a liquid crystalline polymer and silica having an average primary particle size of 5 μm or less. Hereinafter, these materials will be described in the order of liquid crystalline polymer and silica.

[Liquid crystal polymer]
The liquid crystalline polymer used in the present invention refers to a melt processable polymer having a property capable of forming an optically anisotropic molten phase. The property of the anisotropic molten phase can be confirmed by a conventional polarization inspection method using an orthogonal polarizer. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing a molten sample placed on a Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. When the liquid crystalline polymer applicable to the present invention is inspected between crossed polarizers, the polarized light is normally transmitted even in the molten stationary state, and optically anisotropic.

  Although it does not specifically limit as said liquid crystalline polymer, It is preferable that it is aromatic polyester or aromatic polyester amide, The polyester which partially contains aromatic polyester or aromatic polyester amide in the same molecular chain is also the range. It is in. They preferably have a logarithmic viscosity (IV) of at least about 2.0 dl / g, more preferably 2.0-10.0 dl / g when dissolved in pentafluorophenol at 60 ° C. at a concentration of 0.1% by weight. .) Are used.

  The aromatic polyester or aromatic polyester amide as the liquid crystalline polymer applicable to the present invention is particularly preferably at least one compound selected from the group of aromatic hydroxycarboxylic acids, aromatic hydroxyamines, and aromatic diamines. Aromatic polyesters and aromatic polyester amides as constituent components.

More specifically,
(1) A polyester mainly composed of one or more aromatic hydroxycarboxylic acids and derivatives thereof;
(2) mainly (a) one or more of aromatic hydroxycarboxylic acids and derivatives thereof; and (b) one or more of aromatic dicarboxylic acids, alicyclic dicarboxylic acids and derivatives thereof; c) Polyester comprising at least one or more of aromatic diol, alicyclic diol, aliphatic diol and derivatives thereof;
(3) mainly (a) one or more aromatic hydroxycarboxylic acids and derivatives thereof; (b) one or more aromatic hydroxyamines, aromatic diamines and derivatives thereof; and (c). A polyesteramide comprising one or more of aromatic dicarboxylic acid, alicyclic dicarboxylic acid and derivatives thereof;
(4) mainly (a) one or more aromatic hydroxycarboxylic acids and derivatives thereof; (b) one or more aromatic hydroxyamines, aromatic diamines and derivatives thereof; and (c). One or more of aromatic dicarboxylic acid, alicyclic dicarboxylic acid and derivatives thereof; and (d) at least one or more of aromatic diol, alicyclic diol, aliphatic diol and derivatives thereof, and And polyester amides composed of Furthermore, you may use a molecular weight modifier together with said structural component as needed.

（Ｘ：アルキレン（Ｃ１〜Ｃ４）、アルキリデン、−Ｏ−、−ＳＯ−、−ＳＯ_２−、−Ｓ−、−ＣＯ−より選ばれる基である）

（Ｙ：−（ＣＨ_２）_ｎ−（ｎ＝１〜４）、−Ｏ（ＣＨ_２）_ｎＯ−（ｎ＝１〜４）より選ばれる基である。） Preferable examples of specific compounds constituting the liquid crystalline polymer applicable to the present invention include p-hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 6-hydroxy-2-naphthoic acid, 2,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 4,4′-dihydroxybiphenyl, hydroquinone, resorcin, aromatic diols such as compounds represented by the following general formula (I) and the following general formula (II); terephthalic acid, isophthalic acid, 4 , 4′-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid and aromatic dicarboxylic acids such as compounds represented by the following general formula (III); aromatic amines such as p-aminophenol and p-phenylenediamine Can be mentioned.

(X: alkylene (C1 -C4), _{alkylidene, -O -, - SO -,} - SO 2 -, - S -, - is a group selected from CO-)

(Y is a group selected from — (CH ₂ ) _n — (n = 1 to 4) and —O (CH ₂ ) _n O— (n = 1 to 4).

[silica]
The present invention is characterized by containing silica having an average primary particle size of 5 μm or less. By injection-molding the liquid crystalline resin composition containing silica having the above particle diameter, the difference between the surface roughness Ra and the mold surface roughness Ra of the molded body can be made 0.1 mm or less. As a result, fibrillation on the surface of the molded product can be suppressed even by ultrasonic cleaning. In particular, silica having an average primary particle size of 0.7 μm or less is preferable. If the silica has the average primary particle size as described above, it is easy to adjust the difference between the surface roughness Ra of the molded body and the mold surface roughness Ra within 0.1 mm. By using such a liquid crystalline resin composition, the surface characteristics of the molded body are greatly improved, and even if the molded body is subjected to ultrasonic cleaning, the surface of the molded body is hardly fibrillated. As a result, it is possible to suppress an adverse effect on the electronic machine or the like caused by fibrillation of the surface of the molded body. In the conventional liquid crystalline resin composition, it is extremely difficult to adjust the difference between the surface roughness Ra of the molded body and the mold surface roughness Ra within 0.1 mm. If it is contained, the surface roughness of the molded body can be easily adjusted to 0.1 mm or less regardless of the molding conditions. When the average primary particle size is larger than the above range, the difference between the surface roughness Ra of the molded body and the mold surface roughness Ra tends to be difficult to adjust to 0.1 mm or less. As a result, as compared with the case where the silica having the preferable particle diameter is used, when the molded body is ultrasonically cleaned, the surface of the molded body is likely to fluff.

  In particular, when the average primary particle diameter of silica is 0.7 μm or less, the difference between the surface roughness Ra of the molded body and the mold surface roughness Ra is easily suppressed to 0.03 mm or less. As described above, by using silica having an average primary particle size of 0.7 μm or less, the surface characteristics of the molded body are remarkably improved, and even when the obtained molded body is ultrasonically cleaned, fluff that can be visually confirmed can be obtained. An excellent molded article that is completely absent can be obtained. In general, in the case of an optical instrument having a precision instrument part, particularly a lens, a slight amount of dust, dust or the like affects the instrument performance. A molded body in which the surface of the molded body is not fluffed even after ultrasonic cleaning as described above is particularly preferable as a component of a precision instrument or the like.

  As described above, by using a liquid crystalline resin composition containing silica having an average primary particle size of 0.7 μm or less, the surface properties of the molded body are remarkably improved, and it is particularly preferable as a component such as a precision instrument.

  The content of silica having an average primary particle size of 5 μm or less in the liquid crystalline resin composition is not particularly limited, but is preferably 5% by mass to 50% by mass. If it is 5% by mass or more, it is preferable because it can be stably molded, and if it is 50% by mass or less, it is preferable because it does not cause an extreme increase in accuracy. More preferably, it is 10 mass% to 40 mass%.

[Other ingredients]
The liquid crystalline polymer may be a polymer blended with another thermoplastic resin as long as the effects of the present invention are not impaired. The thermoplastic resin used in this case is not particularly limited. For example, an aromatic polyester comprising a polyolefin such as polyethylene or polypropylene, an aromatic dicarboxylic acid such as polyethylene terephthalate or polybutylene terephthalate, and a diol or oxycarboxylic acid. , Polyacetal (homo or copolymer), polystyrene, polyvinyl chloride, polyamide, polycarbonate, ABS, polyoxyphenylene oxide, polyoxyphenylene sulfide, fluororesin and the like. These thermoplastic resins can be used in combination of two or more. Moreover, in order to improve various properties such as mechanical, electrical, chemical properties and flame retardancy, various additives and reinforcing agents can be added to these resins as necessary.

  The liquid crystalline resin composition used in the present invention includes a nucleating agent, a pigment such as carbon black and an inorganic calcined pigment, an antioxidant, a stabilizer, a plasticizer, a lubricant, and a mold release agent, as long as the effects of the present invention are not impaired. A composition imparted with desired characteristics by adding an additive such as a flame retardant is also included in the liquid crystalline resin composition used in the present invention.

<Manufacture of molded body>
The molded product of the present invention can be obtained by injection molding the above-mentioned liquid crystalline resin composition for injection molding. When the liquid crystalline resin composition is injection-molded, the molecular orientation becomes particularly large at the surface of the molded body, and when the molded body is subjected to ultrasonic cleaning, the surface of the molded body tends to be fibrillated. However, by using a specific liquid crystalline resin composition as in the present invention, the surface of the molded body is fibrillated even by ultrasonic cleaning by bringing the surface roughness Ra of the molded body close to the surface roughness Ra of the mold. Can be suppressed and the adverse effects associated therewith can be prevented. The molding conditions are not particularly limited, and the molding can be performed by appropriately changing to the most preferable conditions depending on the type of the liquid crystalline resin composition.

  As described above, the molding conditions for injection molding are not particularly limited, but preferred molding conditions vary slightly depending on the type of the liquid crystalline resin composition, but the mold temperature is 80 ° C. to 250 ° C., and the injection speed is 30 mm / sec. To 300 mm / sec is preferable. The present invention also provides a technique capable of adjusting the difference between the molded body surface roughness Ra and the mold surface roughness Ra within a range of 0.1 mm or less despite the wide range of molding conditions. This is one of the features of the invention.

  As described above, when silica having an average primary particle size of 0.7 μm or less is used, the range of molding conditions further expands, and the difference between the surface roughness Ra of the molded body and the mold surface roughness Ra is almost irrespective of the molding conditions. It can be adjusted to 0.1 mm or less.

<Molded body>
The molded object of this invention is a molded object obtained by shape | molding said liquid crystalline resin composition by said method. The molded body of the present invention is characterized in that the difference between the surface roughness Ra of the molded body after molding and the mold surface roughness Ra is adjusted to 0.1 mm or less. By adjusting the difference in surface roughness to the above range, it is possible to suppress the fibrillation of the molded body that occurs when the molded body is ultrasonically cleaned, and the fuzzy resin is peeled off due to the fibrillation and has an adverse effect on electronic machines and the like. Can be prevented. The difference between the surface roughness Ra of the molded body and the mold surface roughness Ra is more preferably 0.03 mm or less. By suppressing the difference in surface roughness to 0.03 mm or less, it is possible to obtain an excellent molded body having no fluff that can be visually confirmed even if the obtained molded body is ultrasonically cleaned as described above. This is because it is particularly preferable as a component for precision instruments.

  The molded body of the present invention is used as a precision instrument part for ultrasonically cleaning the molded body after molding, such as a camera, a laser disk pickup, a carriage of a floppy (registered trademark) disk player, an arm, a lead screw, or a pickup of a compact disk player. Further, it is particularly preferable as a precision part to which friction, impact, etc. are applied. In the molded body of the present invention, by suppressing the difference between the molded body surface roughness Ra and the mold surface roughness Ra to 0.1 mm or less, the surface of the molded body is fibrillated even if the molded body is ultrasonically cleaned. Can be suppressed. Therefore, adverse effects due to the resin powder due to fibrillation can also be avoided. In particular, the molded article of the present invention is suitable as a camera module in a camera part.

  As described above, particularly when the average primary particle diameter of silica is 0.7 μm or less, it becomes easy to suppress the surface roughness of the molded body to 0.03 mm or less, and as a result, there is no fluff that can be visually confirmed. A molded body can be obtained. Thus, if it is a molded object with almost no fuzz, it can be used especially preferably for the use of precision equipment parts, such as a camera module, a SAW filter, and a hermetic seal.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Material>
Liquid crystalline polymer: Vectra E950iSX (manufactured by Polyplastics)
Glass fiber: ECS03T-786H (Nippon Electric Glass Co., Ltd.) Fiber diameter 10.5 μm
(The fiber length of the glass fiber was adjusted by the extrusion conditions (screw rotation speed, cylinder temperature))
Spherical silica: Admafine SO-C2 (manufactured by Admatechs), average primary particle size 0.5 μm
True spherical silica: Denka fused silica FB-5S DC (manufactured by Denki Kagaku Kogyo Co., Ltd.), average primary particle size 4.0 μm

<Example>
Using the materials shown in Table 1 in the proportions shown in Table 1, molding was performed under the molding conditions shown below. The mold temperature and injection speed were molded under the conditions shown in Table 1. A molded body of 12.5 mm × 120 mm × 0.8 mm was obtained. The molded body was cut in half and evaluated.

[Molding condition]
Molding machine EC40 (Toshiba Machine Co., Ltd.)
Cylinder temperature 350 ° C
Holding pressure 50MPa x 5sec
Cooling time 10 sec
Screw rotation speed 100r. p. m
Screw back pressure 1MPa

<Comparative example>
Using the materials shown in Table 1 in the proportions shown in Table 1, molding was performed under the same molding conditions as in Examples. A molded body having the same size as the example was obtained.

<Evaluation>
The surface roughness of the obtained molded body was measured. About the center part of the molded object cut | disconnected in half, surface roughness Ra was measured using the ultra deep color 3D shape measurement microscope VK-9500 (made by Keyence Corporation). Further, the surface roughness Ra of the mold was also measured in the same manner as the molded body.

The compacts cut in half of the examples and comparative examples were subjected to an ultrasonic cleaner in water at room temperature for 1 minute. Thereafter, the molded bodies before and after being subjected to an ultrasonic cleaning machine were compared, and the area (raised area) of the fluffed portion on the surface of the molded body was evaluated. The evaluation of the area of the fuzzy part was performed visually. The average of three evaluations is shown in Table 1. FIG. 1 shows the relationship between the surface roughness before applying the ultrasonic cleaner and the raised area after applying the ultrasonic cleaner. The evaluation area is 750 mm ² (12.5 mm × 60 mm).

  As apparent from the results of Examples 1 to 5 and Comparative Examples 1 to 4 in FIG. 1 and Table 1, the surface of the molded body was obtained by using a liquid crystalline resin composition containing silica having an average primary particle size of 5 μm or less. The difference between the roughness Ra and the mold surface roughness Ra can be adjusted to 0.1 mm or less, and the raised area on the surface of the molded body can be suppressed even if the molded body is subjected to ultrasonic cleaning.

The raised area after ultrasonically cleaning the molded body is preferably 15 mm ² or less, more preferably 0 mm ² or less. If the surface characteristics of the surface of the molded body can be improved so as to realize the preferable raised area as described above, the adverse effect of the resin powder due to fibrillation can be sufficiently suppressed. By using silica having an average primary particle size of 0.7 μm or less, the above raised area can be suppressed to 0 mm ² even after ultrasonic cleaning, which is particularly preferable as a component of precision equipment.

It is a figure which shows the relationship between the difference of molded object surface roughness Ra and metal mold | die surface roughness Ra, and the raising area after applying to an ultrasonic cleaning machine.

Claims (5)

  A liquid crystalline resin composition for injection molding comprising silica having an average primary particle size of 5 μm or less.   The liquid crystalline resin composition for injection molding according to claim 1, wherein the silica has an average primary particle size of 0.7 μm or less.   A liquid crystal resin composition for injection molding according to claim 1 or 2 is injection-molded, and the difference in surface roughness between the mold surface roughness Ra and the molded body surface roughness Ra is 0.1 mm or less. Is a molded body.   The molded article according to claim 3, wherein the difference in surface roughness is 0.03 mm or less.   The camera module which consists of a molded object of Claim 3 or 4.

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