Ventilation film, ventilation member, and light emitting device

Abstract

Provided is a ventilation film which has air permeability in the thickness direction, is colored, and has a first main surface and a second main surface that is positioned on the opposite side of the first main surface. The second main surface has a greater lightness than the first main surface. The absolute value of the lightness difference between the first main surface and the second main surface is 1.5 to 76 inclusive. The lightness of the second main surface is 20 to 95 inclusive. The luminous transmittance of the light transmitted from the first main surface to the second main surface is 0.015 or less. The lightness mentioned above is the lightness L* of the CIE 1976 L*a*b* color space as specified in JIS Z 8781-4 (2013). The luminous transmittance is expressed by the value of a stimulus value Y of CIE tristimulus values as specified in JIS Z 8781-3 (2016). This ventilation film is suitable for use in light emitting devices such as lamps.

Description

Ventilation membrane, ventilation member, and light-emitting device

[0001] The present invention relates to a ventilation film, and a ventilation member and a light-emitting device that include the same.

[0002] An opening is usually provided in the housing of a vehicle electrical component such as a lamp. The provision of the opening ensures ventilation between the inside and outside of the housing, thereby, for example, alleviating pressure changes that may occur inside the housing. Patent Document 1 discloses a technique for fixing a ventilation membrane to the opening of the housing. Patent Document 1 also describes that fixing the ventilation membrane can ensure ventilation while preventing water and dust from entering the housing, and describes a fluororesin porous body and a polyolefin porous body as examples of the ventilation membrane.

[0003] Japanese Patent Application Laid-Open No. 2003-318557

[0004] Fluororesin porous bodies and polyolefin porous bodies are usually white or near-white in color. Meanwhile, vehicle lamps are becoming increasingly brighter due to improvements in light sources or demands for improved visibility and design. The air-permeable membrane is usually fixed to a surface of the lamp other than the irradiated surface, in other words, a position that is not visible from outside the vehicle while it is in motion. However, the inventors' studies have revealed that using a white or near-white air-permeable membrane increases the likelihood of light from the light source passing through the membrane and leaking from the gap between the lamp and the body. A possible way to suppress light leakage is to use a colored air-permeable membrane. However, it is necessary to prevent the air-permeable membrane fixed to the housing from being overlooked during inspections performed during the assembly of lamps and vehicles.

[0005] The present invention aims to provide a colored breathable membrane suitable for use in light-emitting devices such as lamps.

[0006] The present invention provides a breathable membrane having breathability in its thickness direction, the breathable membrane being colored, having a first main surface and a second main surface located opposite to the first main surface, the second main surface exhibiting a higher brightness than the first main surface, the absolute value of the difference in brightness between the first main surface and the second main surface being 1.5 to 76, the brightness of the second main surface being 20 to 95, and the luminous transmittance of light transmitted from the first main surface to the second main surface being 0.015 or less, wherein the brightness is measured according to the CIE 1976 L standard defined in JIS Z8781-4:2013. * , a * , b * Color space lightness L * The luminous transmittance is expressed by the stimulus value Y of the CIE tristimulus values ​​defined in JIS Z8781-3:2016.

[0007] From another aspect, the present invention provides a ventilation member comprising: the above-described ventilation membrane of the present invention; and a support member that supports the ventilation membrane.

[0008] From another aspect, the present invention provides a light-emitting device comprising: a housing having an opening; a light source housed in the housing; and an air-permeable membrane fixed to the housing so as to cover the opening, wherein the air-permeable membrane is the above-mentioned air-permeable membrane of the present invention.

[0009] In the breathable film of the present invention, the coloring is controlled so that the difference in lightness between one main surface (first main surface) and the other main surface (second main surface) is within a predetermined range, and the lightness of the second main surface, which has a relatively higher lightness, and the luminous transmittance of transmitted light from the first main surface, which has a relatively lower lightness, to the second main surface are within predetermined ranges. The breathable film with controlled coloring is suitable for achieving both the above-mentioned suppression of light leakage and prevention of oversight, and is suitable for use in light-emitting devices such as lamps.

[0010] FIG. 1 is a cross-sectional view schematically showing an example of a gas-permeable membrane of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a colored state of the gas-permeable membrane of the present invention. FIG. 3 is a plan view schematically showing an example of a state of the second main surface of the gas-permeable membrane of the present invention. FIG. 4 is a plan view schematically showing an example of a state of the second main surface of the gas-permeable membrane of the present invention. FIG. 5 is a plan view schematically showing an example of a state of the second main surface of the gas-permeable membrane of the present invention. FIG. 6 is a cross-sectional view schematically showing another example of a gas-permeable membrane of the present invention. FIG. 7 is a cross-sectional view schematically showing an example of a ventilation member of the present invention. FIG. 8A is a cross-sectional view showing cross section B-B of the ventilation member shown in FIG. 8A. FIG. 9A is a perspective view schematically showing an example of a light-emitting device of the present invention. FIG. 9B is a perspective view schematically showing a state of fixing the gas-permeable membrane in the light-emitting device shown in FIG.

[0011] A breathable membrane according to a first aspect of the present invention is a breathable membrane having breathability in a thickness direction, which is colored, and has a first main surface and a second main surface located opposite to the first main surface, wherein the second main surface exhibits a higher lightness than the first main surface, the absolute value of the difference in lightness between the first main surface and the second main surface is 1.5 or more and 76 or less, the lightness of the second main surface is 20 or more and 95 or less, and the luminous transmittance of light transmitted from the first main surface to the second main surface is 0.015 or less, wherein the lightness is measured according to CIE 1976 L as defined in JIS Z8781-4:2013. * , a * , b * Color space lightness L * The luminous transmittance is expressed by the stimulus value Y of the CIE tristimulus values ​​defined in JIS Z8781-3:2016.

[0012] In a second aspect of the present invention, for example, in the breathable membrane according to the first aspect, the second main surface has a first circular region and a second circular region, both of which are circles with a diameter of 6 mm, the first circular region and the second circular region are defined as the region on the second main surface having the greatest brightness and the region on the second main surface having the least brightness, respectively, and the absolute value of the difference in brightness between the first circular region and the second circular region is 2.0 or more.

[0013] In a third aspect of the present invention, for example, in the breathable membrane according to the first or second aspect, the second main surface has a first band-shaped region and a second band-shaped region adjacent to the first band-shaped region and having a lower brightness than the first band-shaped region.

[0014] In a fourth aspect of the present invention, for example, the breathable membrane according to any one of the first to third aspects includes a polytetrafluoroethylene (PTFE) porous membrane.

[0015] In a fifth aspect of the present invention, for example, the breathable membrane according to any one of the first to fourth aspects is made of a single-layer porous polytetrafluoroethylene (PTFE) membrane.

[0016] In a sixth aspect of the present invention, for example, the breathable film according to any one of the first to fifth aspects includes a uniaxially stretched film.

[0017] In a seventh aspect of the present invention, for example, in the breathable membrane according to any one of the first to sixth aspects, the water pressure resistance evaluated by the water resistance test specified in JIS L1092:2009 is 5 kPa or more.

[0018] In an eighth aspect of the present invention, for example, in the breathable membrane according to any one of the first to seventh aspects, the breathability in the thickness direction is 200 seconds / 100 mL or less, as expressed in terms of air permeability (Gurley air permeability) evaluated in accordance with Air Permeability Measurement Method B (Gurley method) defined in JIS L1096:2010.

[0019] In a ninth aspect of the present invention, for example, the breathable film according to any one of the first to eighth aspects has a thickness of more than 100 μm.

[0020] A ventilation member according to a tenth aspect of the present invention comprises: the ventilation membrane according to any one of the first to ninth aspects; and a support member that supports the ventilation membrane.

[0021] An eleventh aspect of the present invention provides a light-emitting device comprising: a housing having an opening; a light source housed in the housing; and an air-permeable membrane fixed to the housing so as to cover the opening, wherein the air-permeable membrane is the air-permeable membrane according to any one of the first to ninth aspects.

[0022] In a twelfth aspect of the present invention, for example, in the light-emitting device according to the eleventh aspect, the breathable film is fixed to the housing so that the first main surface faces the inside of the housing.

[0023] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0024] [Breathable Membrane] An example of a breathable membrane of this embodiment is shown in FIG. 1. The breathable membrane 1 of FIG. 1 is breathable in the thickness direction and is colored. The breathable membrane 1 has a first main surface 11 and a second main surface 12 located opposite the first main surface 11. The second main surface 12 has a higher brightness than the first main surface 11. In other words, the first main surface 11 and the second main surface 12 are main surfaces having a relatively low brightness and a relatively high brightness, respectively. The absolute value d1 of the brightness difference between the first main surface 11 and the second main surface 12 is 1.5 or more and 76 or less. The brightness of the second main surface 12 is 20 or more and 95 or less. The luminous transmittance of light transmitted from the first main surface 11 to the second main surface 12 is 0.015 or less. However, the above brightness is determined based on the CIE 1976 L standard defined in Japanese Industrial Standards (hereinafter referred to as JIS) Z8781-4:2013. * , a * , b * Color space lightness L *The luminous transmittance is expressed by the stimulus value Y of the CIE tristimulus values ​​defined in JIS Z8781-3:2016. In the breathable membrane 1, the first main surface 11 is usually more colored than the second main surface 12. The breathable membrane 1 in FIG. 1 includes a polytetrafluoroethylene (hereinafter referred to as PTFE) porous membrane. More specifically, the breathable membrane 1 is composed of a single layer of PTFE porous membrane. The lightness L of the main surface of the uncolored PTFE porous membrane is * is usually around 93 to 97.

[0025] Lightness L * To measure the lightness L, a measuring instrument such as a spectrophotometer or colorimeter conforming to the above standards can be used. * The lightness L may be calculated by converting the stimulus value Y of the CIE tristimulus values ​​calculated in accordance with the provisions of JIS Z8722:2009 using a conversion formula. * Between the stimulus value Y and the equation: L * =116(Y / Yn) 1 / 3 -16 (provided that Y / Yn>0.008856), or the formula: L * It is known to those skilled in the art that the following conversion formula holds: Y = 903.29 (Y / Yn); (when Y / Yn ≦ 0.008856). Yn is measured using the same measuring instrument and a white reflective standard (white plate) calibrated against a perfect diffuse reflector. Measurement of the stimulus value Y can be performed using a measuring instrument such as a spectrophotometer or colorimeter conforming to the above standard. However, the stimulus value Y must be determined under the following measurement conditions: - Measurement is performed under the geometric condition g (di: 0°). - The diameter of the integrating sphere is 150 mm. - The stimulus values ​​X, Y, and Z obtained when measuring the standard white plate are normalized so that they fall within ±0.03 of the reference value. - The light source used is auxiliary illuminant C for colorimetry specified in JIS Z8720:2012.

[0026] Lightness L of the first principal surface 11 and the second principal surface 12 * The area of ​​the evaluation area of ​​the measuring device for determining the value (hereinafter referred to as the evaluation area) is 700 to 750 mm 2 The area of ​​the main surfaces 11 and 12 of the measurement object is small, and the evaluation area is set within the range of 700 mm 2If it is not possible to ensure this, the evaluation area may be reduced. * The evaluation is performed on at least 20% of the entire area of ​​the main surfaces 11 and 12 to be measured. An evaluation area that can achieve the evaluation at the above ratio may be set by measuring one location on the main surface, or an evaluation area that can achieve the evaluation at the above ratio may be set by evaluating multiple randomly selected locations on the main surface, and the average value of the measurements at each location is used as the lightness L. * It may be determined as follows.

[0027] The luminous transmittance Y is expressed by the stimulus value Y of the CIE tristimulus values ​​defined in JIS Z8781-3:2016. The stimulus value Y can be determined in accordance with the provisions of JIS Z8722:2009. It is known to those skilled in the art that the stimulus value Y corresponds to the luminous transmittance in the evaluation of a transparent object. The measurement conditions for the stimulus value Y are as described above. The evaluation area for determining the luminous transmittance Y is 165 to 185 mm 2 The area of ​​the main surfaces 11 and 12 of the measurement object is small, and the evaluation area is 165 mm 2 If it is not possible to ensure this, the evaluation area may be reduced. However, in this case, the evaluation of the luminous transmittance Y is performed on at least 20% of the entire area of ​​the principal surfaces 11 and 12 to be measured. An evaluation area that can achieve the evaluation at the above ratio may be set by measuring one location on the principal surface, or an evaluation area that can achieve the evaluation at the above ratio may be set by evaluating multiple randomly selected locations on the principal surface, and the average value of the measurements at each location may be determined as the luminous transmittance Y.

[0028] The lightness L between the first main surface 11 and the second main surface 12 * The lower limit of the absolute value d1 of the difference may be 5 or more, 9 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 33 or more, 35 or more, 40 or more, 45 or more, 47 or more, 50 or more, 52 or more, or even 55 or more. The upper limit of the absolute value d1 may be 75 or less, 72 or less, 70 or less, 67 or less, 65 or less, 62 or less, 60 or less, or even 57 or less.

[0029] Lightness L of the second principal surface 12 *The lightness L of the second main surface 12 may be 25 or more, 28 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 52 or more, 55 or more, 57 or more, 60 or more, 62 or more, 65 or more, 67 or more, 70 or more, 72 or more, or even 75 or more. * may be less than 93, 92 or less, 91 or less, 90 or less, 88 or less, or even 86 or less. The second main surface 12 may be colored.

[0030] Lightness L of the first principal surface 11 * is, for example, less than 50, and may be 47 or less, 45 or less, 42 or less, 40 or less, 37 or less, 35 or less, 32 or less, 30 or less, 27 or less, 25 or less, 22 or less, or even 20 or less. * The lower limit is, for example, 5 or more, and may be 7 or more, 10 or more, 12 or more, 15 or more, 17 or more, 20 or more, or even 23 or more.

[0031] The luminous transmittance Y of light transmitted from the first principal surface 11 to the second principal surface 12 may be 0.013 or less, 0.011 or less, 0.010 or less, 0.008 or less, 0.006 or less, 0.005 or less, 0.003 or less, 0.002 or less, or even 0.001 or less. The lower limit of the luminous transmittance Y may be 0.000.

[0032] The luminous transmittance Y of light transmitted from the second main surface 12 to the first main surface 11 can be in the same range as exemplified in the description of the luminous transmittance Y of light transmitted from the first main surface 11 to the second main surface 12.

[0033] Lightness L * the absolute value d1 of the difference between the lightness of the second principal surface L * The luminous transmittance Y of light transmitted from the first main surface 11 to the second main surface 12 can vary depending on, for example, the configuration and coloring method of the breathable membrane 1. Examples of the configuration of the breathable membrane 1 include the thickness, material, average pore size, and, if a stretched membrane is included, the stretching state and stretching method. The coloring method includes the type of colorant.

[0034] The second main surface 12 has a higher lightness L than the first main surface 11. * and the lightness L between the first main surface 11 and the second main surface 12 *The absolute value of the lightness L of the second main surface 12 is 1.5 or more and 76 or less. * is 20 or more and 95 or less, and the luminous transmittance Y of light transmitted from the first main surface 11 to the second main surface 12 is 0.015 or less, the coloring state of the breathable membrane 1 is not limited. In one example of the breathable membrane 1, when viewed in cross section in the thickness direction, the membrane is colored in a gradation pattern in which the degree of coloring gradually decreases from the first main surface 11 to the second main surface 12 (see FIG. 2 ).

[0035] The second main surface 12 has a lightness L * This aspect can contribute to improving the visibility of the breathable membrane 1. * In one example (see FIG. 3 ) having a large area and a small area of ​​lightness L , the second main surface 12 has a first circular area 21 and a second circular area 22, both of which are circular and have a diameter of 6 mm. The first circular area 21 has a lightness L on the second main surface 12. * The second circular area 22 is defined as the largest area on the second main surface 12. * is defined as the smallest area. The brightness L * The absolute value d2 of the difference between the lightness L and the lightness L may be 2.0 or more, 2.5 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or even 8 or more. * The upper limit of the absolute value d2 of the difference between the lightness L and the lightness L may be, for example, 76 or less, and may be 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, or even 25 or less. * The area of ​​the evaluation area for measuring the absolute value d2 of the difference is 1000 mm 2 It may be less than 800 mm 2 Below, 600mm 2 Below, 500mm 2 Below, 400mm 2 Below that, 300 mm 2 The lightness may be L or less. * The second major surface 12 having large and small areas may be visually perceived as having, for example, a mottled, marbled, rippled, or striped major surface.

[0036] As shown in FIG. 4 , the first circular region 21 and the second circular region 12 may be adjacent to each other on the second main surface 12 .

[0037] Partially lightened * In another example (see FIG. 5 ) having a region with a large lightness L and a region with a small lightness L , the second main surface 12 has a first band-shaped region 31 and a region adjacent to the first band-shaped region 31 and having a lightness L less than the first band-shaped region 31. * The first band-shaped region 31 and the second band-shaped region 32 usually have a width and length that are visible to the naked eye. The width may vary along the direction in which each band-shaped region extends, and the variation may be irregular. As shown in FIG. 6 , the first band-shaped region 31 may include a first circular region 21. The second band-shaped region 32 may include a second circular region 22. The first circular region 21 included in the first band-shaped region 31 and the second circular region 22 included in the second band-shaped region 32 may be adjacent to each other on the second main surface 12. The first band-shaped region 31 and the second band-shaped region 32 may be arranged to have an area of ​​1000 mm on the second main surface 12. 2 Below, 800mm 2 Below, 600mm 2 Below, 500mm 2 Below, 400mm 2 Below that, 300 mm 2 It can be in the following range:

[0038] Partially lightened * Whether the second main surface 12 has large and small regions, and if so, the configuration of each region can vary, for example, depending on the configuration of the breathable membrane 1 and the coloring method. Examples of the configuration of the breathable membrane 1 include the thickness, material, average pore size, and, if a stretched membrane is included, the stretching state and stretching method. The coloring method includes the type of colorant. According to the studies of the present inventors, when a coloring method is selected in which a dye solution is applied to one main surface of the raw membrane before coloring, the thicker the breathable membrane 1 is, and the more the breathable membrane 1 includes a uniaxially stretched membrane, the more likely it is that the second main surface 12 will have a lightness L * There is a strong tendency for the saturation to have areas of high and low density.

[0039] The breathable membrane 1 in FIG. 1 includes a PTFE porous membrane. The breathable membrane 1 may include a membrane other than a PTFE porous membrane. In this specification, a porous membrane refers to a membrane having a plurality of pores that can contribute to breathability in the thickness direction. Examples of other membranes are porous membranes made of resins other than PTFE. Examples of other resins include fluororesins other than PTFE, such as polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer, as well as polyolefins such as polyethylene, ultra-high molecular weight polyethylene, polypropylene, poly-4-methylpentene-1, and poly-1-butene. A PTFE porous membrane is particularly suitable for achieving a high balance of breathability and waterproofness in the breathable membrane 1 and for suppressing the permeation of foreign matter such as water and dust.

[0040] The average pore size of the PTFE porous membrane is, for example, 0.01 to 5 μm, and may be 2 μm or less, or even 1 μm or less. The average pore size of the PTFE porous membrane can be measured in accordance with ASTM (American Society for Testing and Materials) F316-86.

[0041] The porosity of the PTFE porous membrane is, for example, 50 to 99%. The porosity of the PTFE porous membrane 1 can be calculated by substituting the mass, thickness, area (area of ​​the main surface) and true density of the membrane into the following formula. The true density of PTFE is 2.18 g / cm 3 Formula: Porosity (%) = {1 - (mass [g] / (thickness [cm] × area [cm 2 ]×True density [g / cm 3 ])) × 100

[0042] The gas-permeable membrane 1 in FIG. 1 is a single layer. The gas-permeable membrane 1 may be a multilayer membrane including two or more layers. The multilayer gas-permeable membrane 1 may include one or more PTFE porous membranes, or may be composed of two or more PTFE porous membranes. FIG. 7 shows an example of a gas-permeable membrane 1 composed of two or more PTFE porous membranes. The gas-permeable membrane 1 in FIG. 7 includes a first PTFE porous membrane 2 and a second PTFE porous membrane 3. The main surface of the first PTFE porous membrane 2 constitutes the first main surface 11, and the main surface of the second PTFE porous membrane 3 constitutes the second main surface 12. The first PTFE porous membrane 2 is usually colored. The first PTFE porous membrane 2 and the second PTFE porous membrane 3 may be colored to different degrees. In other words, the gas-permeable membrane 1 may include two or more PTFE porous membranes 2, 3 having different degrees of coloration. The second PTFE porous film 3 may be colored or may not be colored.

[0043] The breathable membrane 1 may include a uniaxially stretched membrane. A stretched membrane usually has a unique pore structure that can be changed depending on the stretching method and stretching conditions. According to the study by the present inventors, the pore structure of a uniaxially stretched membrane is such that the second main surface 12 is partially brightened with a lightness L * This can contribute to having large and small areas.

[0044] The uniaxially stretched membrane that the breathable membrane 1 may comprise may be a PTFE porous membrane. A PTFE porous membrane is typically composed of countless PTFE fine fibers (fibrils) and may have PTFE agglomerated portions (nodes) where multiple fibrils are connected. Fibrils are typically formed by stretching a PTFE sheet, which is an agglomerate of PTFE. A PTFE porous membrane that is a uniaxially stretched membrane may have a configuration in which multiple fibrils connect between relatively large nodes, depending on the stretching temperature.

[0045] The breathable film 1 may have a thickness of more than 100 μm. The thickness may be 105 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, 140 μm or more, or even 150 μm or more. The upper limit of the thickness is, for example, 5000 μm or less. However, the thickness of the breathable film 1 is not limited to the above example. According to the study by the present inventors, a large thickness of the breathable film 1 means that the second main surface 12 partially has a low brightness L. *This can contribute to having large and small areas.

[0046] The breathable membrane 1 may be waterproof. The breathable membrane 1 may have a water pressure resistance of 5 kPa or more as evaluated by a water resistance test specified in JIS L1092:2009. The water pressure resistance may be 10 kPa or more, 20 kPa or more, 30 kPa or more, 40 kPa or more, 50 kPa or more, 60 kPa or more, 70 kPa or more, 80 kPa or more, 90 kPa or more, or even 100 kPa or more. The upper limit of the water pressure resistance may be 400 kPa or less. The water pressure resistance may be a value when the first main surface 11 is the surface to which water pressure is applied during testing.

[0047] The water pressure resistance of the breathable membrane 1 can be measured using a measuring jig in accordance with the above-mentioned water resistance test method as follows. An example of the measuring jig is a stainless steel disk having a diameter of 47 mm and a through-hole (having a circular cross section) having a diameter of 2 mm at the center. This disk has a thickness that does not deform due to the water pressure applied when measuring the water pressure resistance. Measurement of the water pressure resistance using this measuring jig can be carried out as follows.

[0048] The breathable membrane 1 to be evaluated is fixed to one side of the measuring jig so as to cover the opening of the through-hole of the measuring jig. Fixing is performed so that water does not leak from the fixed part of the membrane during water pressure resistance measurement. The breathable membrane 1 can be fixed using double-sided adhesive tape with a water passage hole punched in the center, whose shape matches the shape of the opening. The double-sided adhesive tape can be placed between the measuring jig and the breathable membrane 1 so that the circumference of the water passage hole and the circumference of the opening coincide. Next, the measuring jig with the breathable membrane 1 fixed is set in the testing device so that the surface opposite the fixed surface of the breathable membrane 1 becomes the water pressure application surface during measurement, and the water pressure resistance is measured according to Water Resistance Test Method A (low water pressure method) or Method B (high water pressure method) specified in JIS L1092:2009. However, the water pressure resistance is measured based on the water pressure when water comes out from one point on the membrane surface of the breathable membrane 1. The measured water pressure resistance can be used as the water pressure resistance of the breathable membrane 1. The test device may have the same configuration as the water resistance test device exemplified in JIS L1092:2009 and have a test piece mounting structure on which the above-mentioned measuring jig can be set.

[0049] The air permeability in the thickness direction of the breathable membrane 1 is expressed as air permeability (Gurley air permeability) determined in accordance with Air Permeability Measurement Method B (Gurley method) specified in JIS L1096:2010, and may be, for example, 200 seconds / 100 mL or less, 150 seconds / 100 mL or less, 100 seconds / 100 mL or less, 75 seconds / 100 mL or less, 50 seconds / 100 mL or less, 45 seconds / 100 mL or less, 40 seconds / 100 mL or less, 35 seconds / 100 mL or less, 30 seconds / 100 mL or less, 25 seconds / 100 mL or less, 20 seconds / 100 mL or less, or even 18 seconds / 100 mL or less. The lower limit of the Gurley air permeability is, for example, 0.5 seconds / 100 mL or more, and may be 1 second / 100 mL or more, 3 seconds / 100 mL or more, 5 seconds / 100 mL or more, 8 seconds / 100 mL or more, or even 10 seconds / 100 mL or more. The Gurley air permeability may be a value when the first main surface 11 is used as the pressure application surface during testing.

[0050] Even when the size of the breathable membrane 1 is smaller than the recommended size (approximately 50 mm × 120 mm) of a test piece in the Gurley method, the Gurley air permeability can be evaluated by using a measuring jig. An example of the measuring jig is a polycarbonate disk having a thickness of 2 mm and a diameter of 47 mm and a through-hole (having a circular cross section with a diameter of 1 mm or 2 mm) at the center. Measurement of the Gurley air permeability using this measuring jig can be carried out as follows.

[0051] The breathable membrane 1 to be evaluated is fixed to one surface of the measuring jig so as to cover the opening of the through-hole of the measuring jig. The fixation is performed so that during measurement of the Gurley air permeability, air passes only through the opening and the effective test portion of the breathable membrane 1 to be evaluated (the portion overlapping with the opening when viewed from a direction perpendicular to the main surface of the fixed breathable membrane 1), and the fixed portion does not obstruct the passage of air through the effective test portion of the breathable membrane 1. To fix the breathable membrane 1, double-sided adhesive tape with a vent hole punched in the center having a shape matching the shape of the opening can be used. The double-sided adhesive tape can be placed between the measuring jig and the breathable membrane 1 so that the periphery of the vent hole coincides with the periphery of the opening. Next, the measuring jig with the breathable membrane 1 fixed thereto is set in a Gurley air permeability tester so that the fixed surface of the breathable membrane 1 is downstream of the air flow during measurement, and the time t1 for 100 mL of air to pass through the breathable membrane 1 is measured. Next, the measured time t1 was measured using an effective test area of ​​642 mm2 as defined in the air permeability measurement method B (Gurley method) of JIS L1096:2010. 2 ] per unit area of ​​the effective test portion of the breathable membrane [mm 2 ]) / 642 [mm 2 ]}, and the resulting converted value t can be used as the Gurley air permeability of the breathable membrane 1. When the above-mentioned circular plate is used as the measuring jig, the area of ​​the effective test portion of the breathable membrane 1 is the area of ​​the cross section of the through-hole. It has been confirmed that the Gurley air permeability measured without using a measuring jig for a breathable membrane 1 that meets the size of the above-mentioned test piece agrees well with the Gurley air permeability measured using the measuring jig after cutting the breathable membrane 1 into small pieces, i.e., that the use of the measuring jig does not substantially affect the measured value of the Gurley air permeability.

[0052] The breathable membrane 1 is typically colored black or gray, but the color is not limited to the above examples.

[0053] The colorant may be a dye or a pigment, but is preferably a dye from the viewpoint of preventing it from falling off from the breathable membrane 1. Falling off from the breathable membrane 1 may cause discoloration, and if the colorant is conductive, damage to electrical circuits or electronic components located near the breathable membrane 1. Furthermore, when the colorant is a dye or an insulating pigment, the breathable membrane 1 can be made insulating, depending on the material of the breathable membrane 1. The insulating property can be achieved by, for example, a 1×10 14 It is expressed by a surface resistivity of 1×10 Ω / □ or more. 15 Ω / □ or more, 1×10 16 Ω / □ or more, even 1×10 17 It may be Ω / □ or more.

[0054] Examples of dyes include azo dyes and oil-soluble dyes, and examples of pigments include carbon black and metal oxides, but the dyes and pigments are not limited to these examples.

[0055] The shape of the breathable membrane 1 is, for example, a polygon including a square and a rectangle, a circle, an ellipse, an irregular shape, or a strip shape when viewed from a direction perpendicular to the first main surface 11 and the second main surface 12. However, the shape of the breathable membrane 1 is not limited to the above examples.

[0056] The gas-permeable membrane 1 may be subjected to a liquid-repellent treatment. The liquid-repellent treatment can be performed by a known method. The liquid-repellent treatment includes a water-repellent treatment and an oil-repellent treatment. The gas-permeable membrane 1 may be a membrane that has not been subjected to a liquid-repellent treatment.

[0057] The breathable membrane 1 can be used, for example, as a membrane that allows gas to pass through while blocking foreign matter such as water and dust. Examples of breathable membranes include a waterproof membrane that is placed in an opening in the housing of a light-emitting device such as a lamp and allows gas to pass through while preventing water from entering through the opening, and a dustproof membrane that is placed in the opening and allows gas to pass through while preventing dust from entering through the opening. The light-emitting device is not limited to a lamp. Furthermore, the housing in which the breathable membrane 1 is placed may be the housing of an electronic device or electronic component other than a light-emitting device. The uses of the breathable membrane 1 are not limited to the above examples. The breathable membrane 1 has a relatively high brightness L *The first main surface 12 having the smallest diameter may be disposed at the opening so as to face the inside of the housing. This arrangement is particularly suitable for suppressing light leakage from the light-emitting device through the gas-permeable film 1.

[0058] The breathable membrane 1 can be produced, for example, by applying a coloring liquid containing a colorant to one main surface of the base membrane before coloring, and then removing the solvent or dispersion medium (hereinafter, the solvent and dispersion medium will be collectively referred to as "solvent") contained in the dyeing liquid by drying or the like. A known application method can be used for the application. However, the method for producing the breathable membrane 1 is not limited to the above example. The main surface (coated surface) to which the coloring liquid is applied has a relative brightness L * can be the first main surface 11 having a small

[0059] The coloring liquid may not contain a liquid repellent agent. Although it depends on the material of the breathable membrane 1, if the coloring liquid contains a liquid repellent agent, the wettability of the coloring liquid with respect to the base membrane is increased, and the brightness L * It can be difficult to increase the difference.

[0060] When the colorant is a dye, the concentration of the dye in the coloring liquid (dyeing liquid) may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, or even 4.5% by weight or more.

[0061] When the coloring liquid contains a liquid repellent agent, the amount of the liquid repellent agent blended may be, for example, less than 20 parts by weight, 18 parts by weight or less, or even 16 parts by weight or less, per 100 parts by weight of the coloring liquid.

[0062] The base film can be formed by a known method. For example, the base film can be a PTFE porous film, which can be formed by extruding and rolling a mixture of PTFE fine powder and a molding aid into a sheet, removing the molding aid, and then stretching the sheet. The stretching may be uniaxial stretching. The stretching may be performed at a temperature above the melting point of PTFE.

[0063] [Ventilation Member] An example of a ventilation member of this embodiment is shown in FIGS. 8A and 8B. FIG. 8B shows a cross section B-B of the ventilation member 4 of FIG. 8A. The ventilation member 4 of FIGS. 8A and 8B includes a ventilation membrane 1 and a support member 5 that supports the ventilation membrane 1. In the example of FIGS. 8A and 8B, the shape of the ventilation membrane 1 is rectangular when viewed from a direction perpendicular to the first main surface 11 and the second main surface 12. The shape of the support member 5 corresponds to the shape of the peripheral edge of the ventilation membrane 1 when viewed from the same direction, specifically a frame shape. However, the shapes of the ventilation membrane 1 and the support member 5 are not limited to the above example, as long as the support member 5 can support the ventilation membrane 1. A ventilation member 4 including the support member 5 can reinforce the ventilation membrane 1 and improve handleability. Furthermore, the support member 5 can serve as an attachment margin for the ventilation membrane 1.

[0064] The material of the support member 5 is typically a resin, a metal, or a composite material thereof. The support member 5 may also be a double-sided adhesive tape.

[0065] The breathable membrane 1 and the support member 5 can be laminated together by various joining methods such as thermal lamination, heat welding, ultrasonic welding, and joining with an adhesive or pressure sensitive adhesive.

[0066] 8A and 8B, the support member 5 is disposed on one side of the breathable membrane 1. The support member 5 may be disposed on both sides of the breathable membrane 1.

[0067] The ventilation member 4 may be a waterproof member having the breathable membrane 1 as a waterproof membrane. The ventilation member 4 may be a dustproof member having the breathable membrane 1 as a dustproof membrane.

[0068] [Light-emitting device] An example of a light-emitting device of this embodiment is shown in Figures 9A and 9B. The light-emitting device shown in Figures 9A and 9B is a lamp 41 for a vehicle. Figure 9A shows the lamp 41 as seen from the side of the irradiation surface 42. Figure 9B shows the lamp 41 as seen from the side opposite to the irradiation surface 42. Two openings 44 are provided in the housing 43 of the lamp 41, and a breathable membrane 1 is fixed so as to cover each opening 44. The breathable membrane 1 has a relatively low brightness L *The lamp 41 is fixed to the housing 43 so that the small first main surface 11 faces the inside of the housing 43. The breathable membrane 1 covers the opening 44 from the outside of the housing 43. In the lamp 41, the breathable membrane 1 is fixed, thereby suppressing the transmission of light from the light source 45 through the opening 44. Furthermore, the breathable membrane 1 has the second main surface 12 facing the outside of the housing 43, making it suitable for visual confirmation during inspection of the lamp 41.

[0069] Examples of the light-emitting device are lamps, signal lights, and backlights for electronic devices such as cameras and displays. The light-emitting device may be for a vehicle. However, the light-emitting device is not limited to the above examples.

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0071] [Evaluation Method] The method for evaluating the breathable membranes produced in the present examples will be described below.

[0072] (Lightness L * ) Lightness of the main surface L * The stimulus value Y of the CIE tristimulus values ​​was measured using a spectrophotometer (SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) capable of evaluation in accordance with the provisions of JIS Z8722:2009, and this was converted into the value Y using the conversion formula L * =116(Y / Yn) 1 / 3 -16 by L * The lightness L * The evaluation of the lightness L was carried out for each of the first main surface 11 and the second main surface 12. The measurement conditions were as described above. * The evaluation area for determining the area is a circle with a diameter of 30 mm (area 706.5 mm 2 )

[0073] The lightness L of the first circular region 21 and the second circular region 22 on the second main surface 12 * Each evaluation area is a circle with a diameter of 6 mm (area 28.3 mm 2 ) except that the lightness of the main surface L * was similarly sought.

[0074] (Luminous transmittance Y) The luminous transmittance Y was determined by measuring the CIE tristimulus stimulus value Y using a spectrophotometer (Murakami Color Research Laboratory, integrating sphere spectral transmittance measuring instrument DOT-3C) capable of evaluation in accordance with the provisions of JIS Z8722:2009. The evaluation was performed on the transmitted light from the first principal surface 11 to the second principal surface 12, and on the transmitted light from the second principal surface 12 to the first principal surface 11. The measurement conditions were as described above. The evaluation area for determining the luminous transmittance Y was a circle with a diameter of 15 mm (area 176.6 mm 2 )

[0075] (Water Pressure Resistance) The water pressure resistance (limit water pressure resistance) was evaluated by the method described above. The evaluation was performed with the first main surface 11 as the water pressure application surface.

[0076] (Air permeability in the thickness direction) The air permeability in the thickness direction was evaluated as Gurley air permeability by the method described above. The evaluation was performed with the first main surface 11 as the pressure application surface.

[0077] [Preparation of raw membrane] (raw membrane A) 100 parts by weight of PTFE fine powder (manufactured by AGC, CD123E) and 20 parts by weight of ISOPAR M (manufactured by Ando Bakelami) as a molding aid were uniformly mixed, and the resulting mixture was compressed using a cylinder and then ram extrusion molded into a sheet. Next, the sheet-like mixture was rolled to a thickness of 0.24 mm through a pair of metal rolls, and then heated to 170 ° C to dry and remove the molding aid to obtain a sheet molded body. Next, the sheet molded body was stretched in the longitudinal direction (rolling direction) at a stretching temperature of 380 ° C and a stretching ratio of 4.2 times to obtain a PTFE porous membrane as raw membrane A. The obtained porous membrane was a uniaxially stretched membrane.

[0078] (Base film B) 100 parts by weight of PTFE fine powder (manufactured by Daikin Industries, F104) and 20 parts by weight of n-dodecane (manufactured by Japan Energy) as a molding aid were uniformly mixed, and the resulting mixture was compressed using a cylinder and then ram extrusion molded into a sheet. Next, the sheet-like mixture was rolled to a thickness of 0.2 mm through a pair of metal rolls, and then stretched at a ratio of 4.5 times in the width direction, and further heated at 150 ° C to dry and remove the molding aid to obtain a sheet molded body. Next, the sheet molded body was stretched in the longitudinal direction (rolling direction) at a stretching temperature of 300 ° C and a stretching ratio of 4 times, and then stretched in the width direction at a stretching temperature of 150 ° C and a stretching ratio of 25 times, and further calcined at 400 ° C to obtain a PTFE porous film as base film B. The obtained porous film was a biaxially stretched film.

[0079] (Examples 1 to 5, 7 to 8, Comparative Examples 2 to 4) A mixture of a black dye (SP BLACK 91L, manufactured by Orient Chemical Industry Co., Ltd., dye concentration 25% by weight) and a solvent was prepared as a dye solution. The solvent was added so that the dye concentration (solids concentration; the same applies hereinafter) in the dye solution would be the value shown in Table 1 below. The solvent was methyl ethyl ketone (MEK). Next, the prepared dye solution was applied to one main surface of raw membrane A, and then the membrane was naturally dried in an atmosphere of 20°C and 50% relative humidity to obtain breathable membranes of Examples 1 to 5, 7 to 8 and Comparative Examples 2 to 4 colored with the dye. The dye solution was applied using an applicator to the coating thickness shown in Table 1.

[0080]

[0081] (Example 6) A load was applied in the thickness direction to the laminate of the breathable membrane of Comparative Example 4 and the base membrane A by moving a roller weighing 2 kg back and forth once to obtain a breathable membrane of Example 6 composed of two layers of PTFE porous membranes.

[0082] (Comparative Example 1) A mixture of a black dye (SP BLACK 91L, manufactured by Orient Chemical Industry Co., Ltd., dye concentration 25 wt%) and a solvent was prepared as a dyeing solution. The solvent was added so that the dye concentration in the dyeing solution was 2.1 wt%. The solvent was a mixed solution of toluene and methyl ethyl ketone (MEK). The mixing ratio, expressed by volume, was toluene:MEK = 75:25. Next, the prepared dyeing solution was applied to one main surface of the base membrane B, and then air-dried in an atmosphere of 20°C and relative humidity 50%, to obtain a breathable membrane of Comparative Example 1 colored with the above dye. The dyeing solution was applied using an applicator to a coating thickness of 17 μm.

[0083] Comparative Example 5 The raw film A was used as Comparative Example 5.

[0084] The evaluation results for each of the breathable membranes of the Examples and Comparative Examples are shown in Tables 2A and 2B below.

[0085]

[0086]

[0087] Next, for the breathable membranes of Examples 1, 7, and 8 and Comparative Example 1, the lightness L of the first circular region and the second circular region on the second main surface was * The results of the evaluation are shown in Table 3 below. * In the evaluation of the brightness L, two more circular regions (a third circular region and a fourth circular region; both of which are circles with a diameter of 6 mm) were randomly set, and the brightness L * Table 3 shows the brightness L of the additional circular regions. * is also shown.

[0088]

[0089] The breathable membrane of the present invention can be used in the same applications as conventional breathable membranes.

Claims

1. A breathable film having air permeability in the thickness direction, which is colored, has a first main surface and a second main surface located opposite to the first main surface, the second main surface exhibits a greater brightness than the first main surface, the absolute value of the brightness difference between the first main surface and the second main surface is 1.5 to 76, the brightness of the second main surface is 20 to 95, and the luminous transmittance of the transmitted light from the first main surface to the second main surface is 0.015 or less. However, the brightness is determined based on the CIE 1976 L standard defined in JIS Z8781-4:2013. * , a * , b * Color space lightness L * The luminous transmittance is represented by the stimulus value Y of the CIE tristimulus values ​​defined in JIS Z8781-3:2016.

2. The breathable membrane according to claim 1, wherein the second principal surface has a first circular region and a second circular region, both of which are circles with a diameter of 6 mm, the first circular region and the second circular region are defined as the region on the second principal surface having the greatest brightness and the region on the second principal surface having the least brightness, respectively, and the absolute value of the brightness difference between the first circular region and the second circular region is 2.0 or more.

3. The breathable membrane described in claim 1, wherein the second main surface has a first band region and a second band region adjacent to the first band region and having a lower brightness than the first band region.

4. The breathable membrane of claim 1, comprising a polytetrafluoroethylene (PTFE) porous membrane.

5. The breathable membrane according to claim 1, which is composed of a single layer of polytetrafluoroethylene (PTFE) porous membrane.

6. The breathable membrane of claim 1, comprising a uniaxially stretched membrane.

7. The breathable membrane described in claim 1, having a water pressure resistance of 5 kPa or more as evaluated by the water resistance test specified in JIS L1092:2009.

8. The breathable membrane according to claim 1, wherein the breathability in the thickness direction is 200 seconds / 100 mL or less, as expressed in terms of air permeability (Gurley air permeability) evaluated in accordance with the breathability measurement method B (Gurley type method) defined in JIS L1096:2010.

9. The breathable membrane according to claim 1, having a thickness of more than 100 μm.

10. A ventilation member comprising: the ventilation membrane according to any one of claims 1 to 9; and a support member that supports the ventilation membrane.

11. A light-emitting device comprising: a housing having an opening; a light source housed in said housing; and an air-permeable membrane fixed to said housing so as to cover said opening, said air-permeable membrane being the air-permeable membrane according to any one of claims 1 to 9.

12. The light-emitting device according to claim 11, wherein the air-permeable membrane is fixed to the housing such that the first main surface faces the inside of the housing.

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