JP4517227B2 - Automotive headlight internal pressure adjustment filter - Google Patents

Description

  The present invention relates to a filter for adjusting internal pressure in an automobile headlight.

  Conventionally, various filters have been employed as an internal pressure adjusting filter as a method of diffusing the internal pressure of a headlight. There are a wide variety of materials such as glass wool, fluororesin, asbestos, etc., but they are shrinkable and have fine pores such as a fluororesin porous membrane or a gap that allows gas to pass through such as glass wool. Yes.

  The present invention provides an internal pressure adjusting filter that is intended to adjust the internal pressure of an automotive headlight that is pressurized by a rise in heat, and that further exhibits a waterproof and dustproof function.

  In the present invention, a breathable film formed by forming a craze is used as a member of an internal pressure adjusting filter that adjusts the internal pressure of a headlight for an automobile, which is pressurized by heat rise to achieve the above object.

  In a breathable film formed by forming a craze, the craze is a fine through-hole in which the voids constituting the craze are difficult for gas to permeate under normal conditions. It is something to give. Therefore, an internal pressure adjusting filter having excellent waterproof and dustproof properties is provided.

  As shown in FIG. 1, the automotive headlight internal pressure adjusting filter of the present invention has one or more internal pressure adjusting filters 4 using a breathable film formed by generating crazes at an arbitrary position of the headlight 2. There are places.

  This internal pressure adjusting filter 4 protects the headlight from pressure fluctuations caused by the heat generated by the lighting of the headlight. The fluctuation in pressure caused by heat generation is a factor that damages the headlight in a sealed state for the purpose of preventing the entry of foreign matter such as water droplets and insects, and is pressurized by the internal pressure adjustment filter. By releasing the internal pressure, the internal pressure is kept stable and the headlight is prevented from being damaged.

  The automotive headlight internal pressure adjusting filter of the present invention is characterized by using a breathable film formed by forming a craze. The crazed breathable film is provided with a striped craze region in a polymer resin film. Thus, a gas such as air is allowed to pass through in a slightly pressurized state, but liquids such as water and particles such as dust can be transmitted.

  The polymer resin used as the material of the polymer resin film can be formed into a film or a sheet, such as polyolefin, polyester, polyamide, styrene resin, polycarbonate, halogen-containing thermoplastic resin, nitrile resin, etc. A thermoplastic resin can be mentioned.

  The polyolefin is an α-olefin homopolymer or a copolymer with another α-olefin and / or α-olefin as a main component and another ethylenically unsaturated monomer. Here, the copolymer may be a block, random, graft, or a composite thereof. Examples of the ethylenically unsaturated monomer include unsaturated carboxylic acids or anhydrides such as methacrylic acid, methyl methacrylate, and maleic acid.

  Specific examples of useful polyolefins include low density branched polyethylene, high density linear polyethylene, low density linear polyethylene, isotactic polypropylene, syndiotactic polypropylene, poly <1-butene>, poly <4-methyl-1 -Pentene> and the like.

  Polyamide is a condensation product containing, as an essential component, a repeating unit having an aromatic or / and aliphatic amide group. Useful polyamides include nylon-4, nylon-6, nylon-6,6, nylon-4,6, nylon-12, amorphous nylon and the like. Among these, preferred polyamides are nylon-6, nylon-6,6, and amorphous nylon.

  Examples of the polyester include, for example, a thermoplastic polyester produced by condensing a dicarboxylic acid or a lower alkyl ester thereof, an acid halide or an acid anhydride derivative, and a glycol or a dihydric phenol according to an ordinary method. Can do. Among these polyesters, it is preferable to use saturated polyesters, particularly polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate.

  The styrene resin is a polymer of a vinyl aromatic compound, and specific examples of the vinyl aromatic compound include styrene, α-methylstyrene, paramethylstyrene, vinyl toluene, vinyl xylene, and the like. Styrenic resins are homopolymers and copolymers of these vinyl aromatic compounds. Among these, polystyrene is preferable, and rubber graft polystyrene (HIPS) and acrylonitrile / butadiene / styrene copolymer are preferably used.

  Polycarbonate includes aromatic polycarbonate, aliphatic polycarbonate, aliphatic / aromatic polycarbonate, etc. Among them, 2,2-bis (4-oxyphenyl) alkane, bis (4-oxyphenyl) ether, bis (4 It is preferable to use an aromatic polycarbonate composed of -oxyphenyl) sulfone, sulfide or sulfoxide bisphenols.

  Examples of the halogen-containing thermoplastic resin include homopolymers and copolymers such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, and vinyl fluoride. In addition, homopolymers and copolymers derived from vinylidene chloride can be mentioned. Among these, preferable halogen-containing thermoplastic resins include homopolymers of polyvinylidene fluoride, copolymers with tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and vinylidene chloride.

  The nitrile resin contains 50% by weight or more of α-β olefinic unsaturated mononitrile. Among these unsaturated mononitriles, it is preferable to use acrylonitrile and methacrylonitrile and mixtures thereof.

  Among the thermoplastic resins, polyolefin, polyester, styrene resin, and halogen-containing thermoplastic resin are preferably used from the viewpoint of moldability to a film or sheet and economical efficiency. These thermoplastic resins may be used alone, combined and used as a composition, or may be blended with another polymer resin, and two or more types of resins may be multilayered. It may be used.

  In view of the ease of formation of crazes, it is desirable to use a resin having a glass transition temperature of −45 ° C. or higher, preferably −30 ° C. or higher, particularly preferably −15 ° C. or higher. When used as a composition or in a multilayered form, it is preferable that the glass transition temperature of the thermoplastic resin, which is the main component, is within the above range. In the case of a thermoplastic resin exhibiting a glass transition temperature lower than this, it is difficult to efficiently form a craze because it is too flexible.

  The polymer resin film or sheet obtained by using the thermoplastic resin is not particularly limited in its production method, and can be obtained by applying various molding methods. Those obtained by applying a die extrusion molding method or a blow-up inflation molding method are industrially advantageous.

  The thickness of the polymer resin film is generally 0.5 to 1,000 μm, preferably 1 to 800 μm, particularly preferably 2 to 500 μm.

The polymer resin film has a molecular orientation degree with a birefringence of 0.5 × 10 ⁻³ or more, preferably 1 × 10 ⁻³ or more, particularly preferably 1.5 × 10 ⁻³ or more. It is effective for forming. In a film having a molecular orientation whose birefringence is out of the above range, it is difficult to easily form a target craze. The degree of orientation refers to the resin structure, the take-up speed, the cooling speed, the molecular weight of the resin, the molecular weight distribution, the tacticity, and other molecular structures at the time of forming the film. If there is, it can be controlled by changing the blow-up ratio or the like, and therefore, a film having an orientation degree in a desired preferable range can be produced by appropriately controlling these.

  The birefringence referred to here is expressed as a difference between the main refractive indexes. For example, the difference (n1−n2) between the refractive index (n1) in the film forming direction and the refractive index (n2) in the direction perpendicular thereto. ) And is one of the indexes expressing the degree of molecular orientation. In practice, these birefringences can be measured by using a polarizing microscope and a compensator. The larger this value, the greater the anisotropy, and the more likely it is to cause crazing.

  The striped craze of the crazed breathable film used in the present invention basically has a width of generally 0.5 to 100 μm, preferably 1 to 50 μm, substantially parallel to the molecular orientation direction of the polymer resin film. Is. The striped craze needs to have a ratio of the number of crazes penetrating in the thickness direction of the film to 10% or more, preferably 20% or more, particularly preferably 40% or more with respect to the total number of crazes. If the ratio is less than the above range, sufficient air permeability cannot be obtained.

  The craze is formed in a direction substantially parallel to the molecular orientation direction. The craze is formed by pulling in the direction perpendicular to the molecular chain orientation direction, and the craze is formed in a direction perpendicular to the molecular chain orientation direction. Because it is difficult to do. The craze mentioned here includes a surface craze appearing on the surface of the polymer resin film and an internal craze generated inside, and refers to a region having a fine crack-like pattern. This craze is composed of molecular bundles (fibrils) and microvoids, and the gas permeability of various gases is generated in this portion.

Although the above-mentioned permeable breathable film varies depending on the type of resin used, for example, when a homopolymer of polyvinylidene fluoride is used, the gas permeability of oxygen and nitrogen gas is generally 0.3 to 100,000 × 10 ⁴ cm. ^{3 / m 2 · 24hr · atm} . Generally ^{10~100,000 × 10 4 g / m 2} · 24 hr in moisture permeability. Transparency is generally from 1 to 99.5 haze, preferably from 2 to 90 haze, particularly preferably from 5 to 80 haze. The tensile strength can be generally in the range of 50 to 500 ks / cm ² , preferably 60 to 500 ks / cm ² , particularly preferably 75 to 500 ks / cm ² .

  The craze formed on the polymer resin film is generally formed in an interval of 0.1 to 1,000 μm, preferably 1 to 800 μm, and is an amount that can be recognized as a striped region.

  Since the breathable film containing craze used in the present invention has the striped craze, it has functions of breathability and moisture permeability. The mechanism is that the craze formed in stripes penetrates in the thickness direction of the film or sheet, so that gas such as oxygen, nitrogen or water vapor passes by diffusing through this craze zone and air permeability is developed. .

  The degree of breathability of the crazed breathable film can be adjusted by changing the width of the craze formed in the polymer resin film, the distance between the crazes, and the ratio of the number of crazes penetrated. Specifically, by adjusting the degree of molecular orientation of the polymer resin film, the temperature at which the craze is formed, the tension of the polymer resin film (tension in the tension state), the folding angle of the film, etc. Breathability can be controlled and a breathable film can be provided according to the intended use.

  For example, increasing the tension when forming a craze or reducing the folding angle reduces the spacing between the generated crazes and increases the percentage of the number of crazes penetrated, resulting in increased breathability. . The air permeability film containing craze adjusted by changing the width of the craze, the distance between the crazes, and the ratio of the craze penetrated is the gas permeability, moisture permeability, transparency and tensile strength of the oxygen and nitrogen gas. Etc. can be controlled.

  Since the present invention has both breathability, waterproofness and dustproofness at the same time, the performance of electrical products such as mobile phones is maintained, and when it is applied to lighting equipment that generates heat, it causes heat generation. Damage due to fluctuations in internal pressure is avoided.

Schematic which shows an example of the filter for internal pressure adjustment provided in the headlight of the motor vehicle.

Explanation of symbols

2 Headlight
4 Internal pressure adjustment filter

Claims (1)

A breathable film having a non- existent characteristic that allows a gas such as air to pass through in a slightly pressurized state but allows liquids such as water and particles such as dust to permeate. A filter for adjusting the internal pressure of an automotive headlight, characterized by being used.

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