Breathable film, breathable member, and light emitting device

Abstract

The provided gas-permeable film has gas permeability in the thickness direction, is colored, and has a first main surface and a second main surface located on the opposite side of the first main surface. The second main surface exhibits a higher 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 or more and 76 or less. The second main surface has a brightness of 20 or more and 95 or less. The visual transmittance of light transmitted from the first principal surface to the second principal surface is 0.015 or less. Wherein the lightness is the lightness L * of CIE 1976 L *, a * and b * color spaces specified in JIS Z8781-4: 2013, and the lightness is the lightness L * of the CIE 1976 L *, a * and b * color spaces. The visual transmittance is represented by the value of the stimulus value (Y) of the CIE tristimulus value specified in JIS Z8781-3: 2016. The breathable film is suitable for light-emitting devices such as lamps.

Description

Technical Field

[0001] The present invention relates to a breathable film, a breathable member including the breathable film, and a light-emitting device. Background Art

[0002] An opening is usually provided in a housing of a vehicle electrical component such as a lamp. By providing the opening, ventilation between the inside and outside of the housing can be ensured, and thus, for example, a pressure change that may occur inside the housing can be alleviated. A technique of fixing a breathable film to the opening of the housing is disclosed in Patent Document 1. In addition, Patent Document 1 describes that by fixing the breathable film, it is possible to ensure ventilation while preventing water and dust from entering the inside of the housing, and examples of the breathable film include a fluororesin porous body and a polyolefin porous body.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-318557 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] A fluororesin porous body or a polyolefin porous body generally has a white or near-white color. On the other hand, for vehicle lamps, with the improvement of light sources or according to the requirements of improving visual recognition and design appearance, the situation of promoting high brightness is in progress. The breathable film is usually fixed on a surface of the lamp other than the irradiation surface, in other words, fixed at a position that cannot be seen from the outside of a running vehicle. However, according to the research of the present inventor, when a breathable film having a white or near-white color is used, light from the light source easily passes through the breathable film and leaks from the gap between the lamp and the vehicle body. In order to suppress light leakage, a colored breathable film can be considered. However, in the inspection performed during the assembly of the lamp and the vehicle, it is necessary to prevent the missed inspection of the breathable film fixed to the housing.

[0008] An object of the present invention is to provide a colored breathable film suitable for use in a light-emitting device such as a lamp.

[0009] Means for Solving the Problems

[0010] The present invention provides a breathable film having air permeability in the thickness direction, wherein

[0011] the breathable film is colored,

[0012] the breathable film has a first major surface and a second major surface on the opposite side of the first major surface,

[0013] the second major surface exhibits a higher lightness than the first major surface,

[0014] The absolute value of the difference in lightness between the first major surface and the second major surface is 1.5 or more and 76 or less.

[0015] The lightness of the second major surface is 20 or more and 95 or less.

[0016] The visual transmittance of the transmitted light from the first major surface to the second major surface is 0.015 or less.

[0017] Herein, the lightness is the CIE1976 L in JIS Z8781-4:2013 * , a * , b * Lightness L in the color space * ,

[0018] The visual transmittance is represented by the value of stimulus Y of the CIE tristimulus values defined in JIS Z8781-3:2016.

[0019] According to another aspect, the present invention provides a breathable member, wherein the breathable member includes:

[0020] The breathable film of the present invention as described above; and

[0021] A support member that supports the breathable film.

[0022] According to another aspect, the present invention provides a light-emitting device, wherein the light-emitting device includes:

[0023] A housing having an opening;

[0024] A light source housed in the housing; and

[0025] A breathable film fixed to the housing so as to cover the opening,

[0026] The breathable film is the breathable film of the present invention as described above.

[0027] Advantageous Effects of the Invention

[0028] For the breathable film of the present invention, the coloring is controlled such that the difference in lightness between one major surface (the first major surface) and the other major surface (the second major surface) is within a specified range, and the lightness of the second major surface with a relatively high lightness, and the visual transmittance of the transmitted light from the first major surface with a relatively low lightness to the second major surface are within specified ranges. The breathable film with the controlled coloring is suitable for simultaneously achieving the above-mentioned suppression of light leakage and prevention of missed inspection, and is suitable for use in light-emitting devices such as lamps. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional view schematically showing an example of the breathable film of the present invention.

[0030] Figure 2 It is a cross-sectional view schematically showing an example of the colored state of the breathable film of the present invention.

[0031] Figure 3 It is a top view schematically showing an example of the state of the second main surface of the breathable film of the present invention.

[0032] Figure 4 It is a top view schematically showing an example of the state of the second main surface of the breathable film of the present invention.

[0033] Figure 5 It is a top view schematically showing an example of the state of the second main surface of the breathable film of the present invention.

[0034] Figure 6 It is a top view schematically showing an example of the state of the second main surface of the breathable film of the present invention.

[0035] Figure 7 It is a cross-sectional view schematically showing another example of the breathable film of the present invention.

[0036] Figure 8A It is a top view schematically showing an example of the breathable member of the present invention.

[0037] Figure 8B It shows Figure 8A A cross-sectional view of the cross-section B-B of the breathable member shown.

[0038] Figure 9A It is a perspective view schematically showing an example of the light-emitting device of the present invention.

[0039] Figure 9B It is schematically showing Figure 9A A perspective view of the state of fixation of the breathable film in the light-emitting device shown. Detailed Description

[0040] The breathable film of the first aspect of the present invention is a breathable film having breathability in the thickness direction, wherein,

[0041] The breathable film is colored,

[0042] The breathable film has a first main surface and a second main surface located on the opposite side of the first main surface,

[0043] The second main surface exhibits higher lightness than the first main surface,

[0044] 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,

[0045] The lightness of the second major surface is 20 or more and 95 or less,

[0046] The visual transmittance of the transmitted light from the first major surface to the second major surface is 0.015 or less.

[0047] wherein the lightness is the CIE1976 L * , a * , b * lightness L in the color space * ,

[0048] The visual transmittance is represented by the value of the stimulus value Y of the CIE tristimulus values defined in JIS Z8781-3:2016.

[0049] In the second aspect of the present invention, for example, in the breathable film of the first aspect, the second major surface has a first circular region and a second circular region, both of which are circles with a diameter of 6 mm,

[0050] The first circular region and the second circular region are respectively defined as the region with the maximum lightness and the region with the minimum lightness in the second major surface.

[0051] The absolute value of the difference in lightness between the first circular region and the second circular region is 2.0 or more.

[0052] In the third aspect of the present invention, for example, in the breathable film of the first aspect or the second aspect, the second major surface has a first strip region and a second strip region, the second strip region is adjacent to the first strip region, and the lightness of the second strip region is less than the lightness of the first strip region.

[0053] In the fourth aspect of the present invention, for example, the breathable film of any one of the first aspect to the third aspect includes a polytetrafluoroethylene (PTFE) porous film.

[0054] In the fifth aspect of the present invention, for example, the breathable film of any one of the first aspect to the fourth aspect is composed of a single-layer polytetrafluoroethylene (PTFE) porous film.

[0055] In the sixth aspect of the present invention, for example, the breathable film of any one of the first aspect to the fifth aspect includes a uniaxially stretched film.

[0056] In the seventh aspect of the present invention, for example, for the breathable film of 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.

[0057] In the eighth aspect of the present invention, for example, for the breathable film of any one of the first to seventh aspects, in terms of the air permeability (Gurley air permeability) evaluated by the air permeability measurement method B (Gurley method) specified in JIS L1096:2010, the air permeability in the thickness direction is 200 seconds / 100 mL or less.

[0058] In the ninth aspect of the present invention, for example, the breathable film of any one of the first to eighth aspects has a thickness greater than 100 μm.

[0059] The breathable member of the tenth aspect of the present invention includes:

[0060] The breathable film of any one of the first to ninth aspects; and

[0061] A support member that supports the breathable film.

[0062] The light-emitting device of the eleventh aspect of the present invention includes:

[0063] A housing having an opening;

[0064] A light source housed in the housing; and

[0065] A breathable film fixed to the housing so as to cover the opening,

[0066] The breathable film is the breathable film of any one of the first to ninth aspects.

[0067] In the twelfth aspect of the present invention, for example, in the light-emitting device of the eleventh aspect, the breathable film is fixed to the housing with the first main surface facing the inside of the housing.

[0068] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

[0069] [Breathable film]

[0070] Figure 1 An example of the breathable film of the present embodiment is shown. Figure 1The breathable film 1 has breathability in the thickness direction and is colored. The breathable film 1 has a first main surface 11 and a second main surface 12 located on the opposite side of the first main surface 11. The second main surface 12 has a higher lightness than the first main surface 11. In other words, the first main surface 11 and the second main surface 12 are the main surface with relatively lower lightness and the main surface with relatively higher lightness, respectively. The absolute value d1 of the difference in lightness between the first main surface 11 and the second main surface 12 is 1.5 or more and 76 or less. The lightness of the second main surface 12 is 20 or more and 95 or less. The visual transmittance of the transmitted light from the first main surface 11 to the second main surface 12 is 0.015 or less. Herein, the above lightness is the CIE1976 L specified in Japanese Industrial Standard (hereinafter referred to as JIS) Z8781-4:2013 * , a * , b * Lightness L in the color space * . The above visual transmittance is represented by the value of the stimulus value Y of the CIE tristimulus values specified in JIS Z8781-3:2016. In the breathable film 1, the degree of coloring of the first main surface 11 is generally greater than that of the second main surface 12. Figure 1 The breathable film 1 of * comprises a polytetrafluoroethylene (hereinafter referred to as PTFE) porous film. More specifically, the breathable film 1 is composed of a single-layer PTFE porous film. The lightness L of the main surface of the uncolored PTFE porous film

[0071] is generally about 93 to about 97. * In the measurement of the lightness L * , measuring devices such as a spectrophotometer or a colorimeter based on the above standards can be used. The lightness L * can be obtained by converting the stimulus value Y of the CIE tristimulus values obtained according to the provisions of JIS Z8722:2009 using a conversion formula. As is known to those skilled in the art, between the lightness L * and the stimulus value Y, the formula: L 1 / 3 = 116 (Y / Yn) * - 16 (where Y / Yn > 0.008856) or the formula: L

[0072] · Measure under the geometric condition g (di: 0°).

[0073] · Set the diameter of the integrating sphere to 150 mm.

[0074] · Standardize in such a way that the values of stimulus values X, Y, and Z when measuring the color of a standard white board fall within ±0.03 of the reference value.

[0075] · Use the auxiliary illuminator C for color measurement specified in JIS Z8720:2012 as the light source.

[0076] For obtaining the lightness L of the first main surface 11 and the second main surface 12 * The area of the evaluation region of the measuring device (hereinafter referred to as the evaluation area) is set within the range of 700 mm 2 to 750 mm 2 If the areas of the main surfaces 11 and 12 of the object to be measured are small and an evaluation area of 700 mm 2 cannot be ensured, the evaluation area can also be reduced. However, in this case, the evaluation of the lightness L * is performed on at least 20% of the total area of the main surfaces 11 and 12 of the object to be measured. An evaluation area that can achieve the above ratio of evaluation through the measurement of one part on the main surface can be set, or an evaluation area that can achieve the above ratio of evaluation through the evaluation of multiple randomly selected parts on the main surface can be set. The average value of the measurement values at each part is defined as the lightness L * .

[0077] The visual transmittance Y is represented by the value of the stimulus value Y of the CIE tristimulus values specified in JIS Z8781-3:2016. The stimulus value Y can be obtained according to the provisions of JIS Z8722:2009. In the evaluation of a transmissive object, it is known to those skilled in the art that the stimulus value Y is equivalent to the visual transmittance. The measurement conditions of the stimulus value Y are as described above. The evaluation area when obtaining the visual transmittance Y is set within the range of 165 mm 2 to 185 mm 2 If the areas of the main surfaces 11 and 12 of the object to be measured are small and an evaluation area of 165 mm 2 cannot be ensured, the evaluation area can also be reduced. However, in this case, the evaluation of the visual transmittance Y is performed on at least 20% of the total area of the main surfaces 11 and 12 of the object to be measured. An evaluation area that can achieve the above ratio of evaluation through the measurement of one part on the main surface can be set, or an evaluation area that can achieve the above ratio of evaluation through the evaluation of multiple randomly selected parts on the main surface can be set. The average value of the measurement values at each part is defined as the visual transmittance Y.

[0078] 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 can 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, and further can be 55 or more. The upper limit of the absolute value d1 can be 75 or less, 72 or less, 70 or less, 67 or less, 65 or less, 62 or less, 60 or less, and further can be 57 or less.

[0079] The lightness L of the second main surface 12 * can 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, and further can be 75 or more. The lightness L of the second main surface 12 * can be less than 93, can be 92 or less, 91 or less, 90 or less, 88 or less, and further can be 86 or less. The second main surface 12 can be colored.

[0080] The lightness L of the first main surface 11 * For example, it is less than 50, can 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, and further can be 20 or less. The lightness L of the first main surface 11 * The lower limit of, for example, is 5 or more, can be 7 or more, 10 or more, 12 or more, 15 or more, 17 or more, 20 or more, and further can be 23 or more.

[0081] The visual transmittance Y of the transmitted light from the first main surface 11 to the second main surface 12 can 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, and further can be 0.001 or less. The lower limit of the visual transmittance Y can be 0.000.

[0082] The visual transmittance Y of the transmitted light from the second main surface 12 to the first main surface 11 can be in the same range as the range exemplified in the description of the visual transmittance Y of the transmitted light from the first main surface 11 to the second main surface 12.

[0083] Lightness L * The absolute value d1 of the difference, the lightness L of the second main surface * , the visual transmittance Y of the transmitted light from the first main surface 11 to the second main surface 12, for example, can be changed by the constitution of the breathable film 1 and the coloring method. Examples of the constitution of the breathable film 1 are thickness, material, average pore size, and in the case of including a stretched film, its stretching state and stretching method. The coloring method includes the type of coloring agent.

[0084] As long as the second major surface 12 exhibits a higher lightness L than the first major surface 11 * , the absolute value of the difference in lightness L between the first major surface 11 and the second major surface 12 * is 1.5 or more and 76 or less, the lightness L of the second major surface 12 * is 20 or more and 95 or less, and the visual transmittance Y of the transmitted light from the first major surface 11 to the second major surface 12 is 0.015 or less, then there is no limitation on the coloring state of the breathable film 1. In one example of the breathable film 1, a gradient coloring in which the degree of coloring gradually decreases from the first major surface 11 to the second major surface 12 was implemented when observing the cross-section in the thickness direction (refer to Figure 2 ).

[0085] The second major surface 12 may locally have regions with a large lightness L * and regions with a small lightness L * . This method can help improve the visual recognition of the breathable film 1. In one example of locally having regions with a large lightness L * and regions with a small lightness L * (refer to Figure 3 ), the second major surface 12 has a first circular region 21 and a second circular region 22, and both the first circular region 21 and the second circular region 22 are circles with a diameter of 6 mm. The first circular region 21 is defined as the region with the largest lightness L * in the second major surface 12. The second circular region 22 is defined as the region with the smallest lightness L * in the second major surface 12. The absolute value d2 of the difference in lightness L between the first circular region 21 and the second circular region 22 * can be 2.0 or more, or can be 2.5 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, and further can be 8 or more. The upper limit of the absolute value d2 of the difference in lightness L * is, for example, 76 or less, and can 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, and further can be 25 or less. The area of the evaluation region for measuring the absolute value d2 of the difference in lightness L * can be 1000 mm 2 or less, or can be 800 mm 2 or less, 600 mm 2 or less, 500 mm 2 or less, 400 mm 2 or less, and further can be 300 mm 2 or less. Locally having regions with a large lightness L * and regions with a small lightness L *The second main surface 12 in a small area can be visually recognized as a main surface having, for example, a spotted pattern, a frost-like pattern, a wavy pattern, or a striped pattern.

[0086] like Figure 4 As shown, the first circular area 21 and the second circular area 12 may also be adjacent to each other on the second main surface 12 .

[0087] Locally, it has a lightness L * Large area and lightness L * Another example of a small region (see Figure 5 ), the second main surface 12 has a first band region 31 and a band region adjacent to the first band region 31 and having a brightness L * The second band-shaped area 32 is smaller than the first band-shaped area 31. The first band-shaped area 31 and the second band-shaped area 32 usually have a width and a length that can be visually identified. The width may vary along the direction in which each band-shaped area extends, and the variation may be irregular. Figure 6 As shown, the first band-shaped area 31 may include the first circular area 21. In addition, the second band-shaped area 32 may include the second circular area 22. The first circular area 21 included in the first band-shaped area 31 and the second circular area 22 included in the second band-shaped area 32 may also be adjacent to each other on the second main surface 12. The area where the first band-shaped area 31 and the second band-shaped area 32 may exist in the second main surface 12 is 1000mm 2 Below, 800mm 2 Below, 600mm 2 Below, 500mm 2 Below, 400mm 2 Below, further to 300mm 2 Within the following range.

[0088] Whether the second main surface 12 has a local brightness L * Large area and lightness L * A small area and a portion of the second main surface 12 having a lightness L * Large area and lightness L * The configuration of each region in the case of a small region can be changed, for example, by the configuration of the gas-permeable film 1 and the coloring method. Examples of the configuration of the gas-permeable film 1 include thickness, material, average pore size, and, in the case of a stretched film, its stretched state and stretching method. The coloring method includes the type of colorant. According to the research of the present inventors, when a coloring method is selected in which a dyeing liquid is applied to one main surface of the original film before coloring, although it also depends on the material of the gas-permeable film 1, the larger the thickness of the gas-permeable film 1, and in the case of the gas-permeable film 1 including a uniaxially stretched film, the second main surface 12 partially has a lightness L * Large area and lightness L* The stronger the tendency of the smaller area.

[0089] Figure 1 The breathable film 1 includes a PTFE porous film. The breathable film 1 may also include a film other than the PTFE porous film. In the present specification, the porous film refers to a film having a plurality of pores that can contribute to breathability in the thickness direction. Examples of other films are porous films made of resins other than PTFE. Examples of other resins are fluororesins other than PTFE such as polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer, and polyolefins such as polyethylene, ultra-high molecular weight polyethylene, polypropylene, poly-4-methyl-1-pentene, and poly-1-butene. The PTFE porous film is particularly suitable for a high balance of breathability and waterproofness of the breathable film 1, and for suppressing the penetration of foreign substances such as water and dust.

[0090] The average pore diameter of the PTFE porous film is, for example, 0.01 μm to 5 μm, may be 2 μm or less, and further may be 1 μm or less. The average pore diameter of the PTFE porous film can be measured according to ASTM (American Society for Testing and Materials) F316-86.

[0091] The porosity of the PTFE porous film is, for example, 50% to 99%. The porosity of the PTFE porous film 1 can be calculated by substituting the mass, thickness, area (area of the main surface), and true density of the film into the following formula. It should be noted that the true density of PTFE is 2.18 g / cm 3 .

[0092] Formula: Porosity (%) = {1 - (mass [g] / (thickness [cm] × area [cm 2 × true density [g / cm 3 )} × 100

[0093] Figure 1 The breathable film 1 is a single layer. The breathable film 1 may also be a multi-layer including two or more layers. The multi-layer breathable film 1 may include one or two or more PTFE porous films, or may be composed of two or more PTFE porous films. Figure 7 Shows an example of the breathable film 1 composed of two or more PTFE porous films. Figure 7The breathable film 1 includes a first PTFE porous film 2 and a second PTFE porous film 3. The main surface of the first PTFE porous film 2 constitutes the first main surface 11, and the main surface of the second PTFE porous film 3 constitutes the second main surface 12. The first PTFE porous film 2 is usually colored. The coloring degrees of the first PTFE porous film 2 and the second PTFE porous film 3 can be different. In other words, the breathable film 1 can include two or more PTFE porous films 2 and PTFE porous films 3 with different coloring degrees. The second PTFE porous film 3 can be colored or not colored.

[0094] The breathable film 1 can include a uniaxially stretched film. The stretched film usually has a unique pore structure that can vary according to the stretching method and stretching conditions. According to the research of the present inventors, the pore structure of the uniaxially stretched film helps the second main surface 12 to locally have regions with a large lightness L * and regions with a small lightness L. *

[0095] The uniaxially stretched film that the breathable film 1 can include can be a PTFE porous film. The PTFE porous film is usually composed of countless fine PTFE fibers (fibrils) and sometimes has PTFE aggregation parts (nodes) formed by connecting multiple fibrils. The fibrils are typically formed by stretching an aggregate of PTFE, that is, a PTFE sheet. Although it also depends on the stretching temperature, the PTFE porous film as a uniaxially stretched film can have a structure in which multiple fibrils connect between nodes with relatively large sizes.

[0096] The breathable film 1 can have a thickness greater than 100 μm. The thickness can be 105 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, 140 μm or more, and further can be 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 examples. It should be noted that according to the research of the present inventors, when the thickness of the breathable film 1 is large, it can help the second main surface 12 to locally have regions with a large lightness L * and regions with a small lightness L. *

[0097] The breathable film 1 can have waterproofness. The water pressure resistance of the breathable film 1 evaluated by the water resistance test specified in JIS L1092:2009 can be 5 kPa or more. The water pressure resistance can 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, and further can be 100 kPa or more. The upper limit of the water pressure resistance can be 400 kPa or less. The water pressure resistance can be the value when the first main surface 11 is used as the water pressure application surface during the test.

[0098] The water pressure resistance of the breathable film 1 can be measured as follows using a measuring jig and in accordance with the above water resistance test method. An example of the measuring jig is a stainless steel circular plate with a diameter of 47 mm having a through-hole with a diameter of 2 mm (with a circular cross-section) provided at the center. This circular plate has a thickness that will not deform due to the water pressure applied during the measurement of the water pressure resistance. The measurement of the water pressure resistance using this measuring jig can be carried out as follows.

[0099] Fix the breathable film 1 to be evaluated on one surface of the measuring jig so as to cover the opening of the through-hole of the measuring jig. The fixing is carried out in such a manner that water does not leak from the fixed portion of the film during the measurement of the water pressure resistance. The breathable film 1 can be fixed using a double-sided adhesive tape with a water passage punched out at the center portion having a shape consistent with the shape of the opening. The double-sided adhesive tape only needs to be arranged between the measuring jig and the breathable film 1 such that the outer periphery of the water passage coincides with the outer periphery of the opening. Next, place the measuring jig with the breathable film 1 fixed therein in the test apparatus such that the surface of the breathable film 1 opposite to the fixed surface becomes the water pressure application surface during the measurement, and measure the water pressure resistance according to the water resistance test A method (low water pressure method) or B method (high water pressure method) specified in JIS L1092:2009. Among them, the water pressure resistance is measured based on the water pressure when water flows out from a part of the film surface of the breathable film 1. The measured water pressure resistance can be taken as the water pressure resistance of the breathable film 1. As the test apparatus, an apparatus having the same structure as the water resistance test apparatus exemplified in JIS L1092:2009 and having a test piece mounting structure capable of setting the above measuring jig can be used.

[0100] In terms of the air permeability (Gurley air permeability) obtained according to the air permeability measurement B method (Gurley method) specified in JIS L1096:2010, the air permeability in the thickness direction of the breathable film 1 is, for example, 200 seconds / 100 mL or less, and can be 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, and further can be 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 can 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, and further can be 10 seconds / 100 mL or more. The Gurley air permeability can be the value when the first main surface 11 is the pressure application surface during the test.

[0101] It should be noted that when the size of the breathable film 1 does not meet the recommended size of the test piece in Gurley's method (about 50 mm × 120 mm), the Gurley air permeability can also be evaluated by using a measuring fixture. An example of the measuring fixture is a polycarbonate circular plate with a thickness of 2 mm and a diameter of 47 mm, having a through hole (with a circular cross-section of 1 mm or 2 mm in diameter) in the center. The measurement of the Gurley air permeability using this measuring fixture can be carried out as follows.

[0102] Fix the breathable film 1 to be evaluated on one surface of the measuring fixture so as to cover the opening of the through hole of the measuring fixture. The fixing is carried out in such a way that in the measurement of Gurley air permeability, air only passes through the opening and the effective test part of the breathable film 1 to be evaluated (the part that overlaps the opening when observed from a direction perpendicular to the main surface of the fixed breathable film 1), and the fixed part does not hinder the passage of air in the effective test part of the breathable film 1. The breathable film 1 can be fixed using a double-sided adhesive tape with a vent hole punched in the center part, having a shape consistent with the shape of the opening. The double-sided adhesive tape only needs to be arranged between the measuring fixture and the breathable film 1 in such a way that the outer periphery of the vent hole coincides with the outer periphery of the opening. Then, place the measuring fixture with the breathable film 1 fixed therein in the Gurley air permeability tester with the fixed surface of the breathable film 1 being the downstream side of the air flow during measurement, and measure the time t1 for 100 mL of air to pass through the breathable film 1. Then, convert the measured time t1 using the formula t = { (t1) × (area of the effective test part of the breathable film [mm 2 ) / 642 [mm 2} into the value t specified in Method B (Gurley method) for measuring air permeability in JIS L1096:2010 per unit effective test area of 642 [mm 2 , and take the obtained converted value t as the Gurley air permeability of the breathable film 1. When using the above circular plate as the measuring fixture, the area of the effective test part of the breathable film 1 is the cross-sectional area of the through hole. It should be noted that it has been confirmed that the Gurley air permeability measured for the breathable film 1 that meets the above test piece size without using the measuring fixture is in good agreement with the Gurley air permeability measured after making small pieces of this breathable film 1 and using the measuring fixture, that is, the use of the measuring fixture does not substantially affect the measured value of the Gurley air permeability.

[0103] The breathable film 1 is typically colored black or gray. However, the coloring color is not limited to the above examples.

[0104] The colorant can be a dye or a pigment, but from the viewpoint of preventing detachment from the breathable film 1, a dye is preferred. Detachment from the breathable film 1 sometimes causes color bleeding, and in the case where the colorant is conductive, it can cause damage to circuits, electronic components, etc. located near the breathable film 1. In addition, in the case where the colorant is a dye or an insulating pigment, although it also depends on the material of the breathable film 1, an insulating breathable film 1 can be produced. The insulation is represented by a surface resistivity of, for example, 1 × 10 14 Ω / square or more on at least one of the first main surface 11 and the second main surface 12. The surface resistivity can be 1 × 10 15 Ω / square or more, 1 × 10 16 Ω / square or more, and further can be 1 × 10 17 Ω / square or more.

[0105] Examples of dyes are azo dyes and oil-soluble dyes. Examples of pigments are carbon black and metal oxides. However, dyes and pigments are not limited to the above examples.

[0106] When viewed from a direction perpendicular to the first main surface 11 and the second main surface 12, the shape of the breathable film 1 is, for example, a polygon including a square and a rectangle, a circle, an ellipse, an irregular shape, and a strip shape. However, the shape of the breathable film 1 is not limited to the above examples.

[0107] A liquid repellent treatment can be applied to the breathable film 1. The liquid repellent treatment can be carried out by a known method. The liquid repellent treatment includes a water repellent treatment and an oil repellent treatment. The breathable film 1 can also be a film without the liquid repellent treatment.

[0108] The breathable film 1 can be used, for example, as a film that allows gas to pass through while blocking foreign substances such as water and dust. Examples of the breathable film are a waterproof film disposed at an opening of a housing of a light-emitting device such as a lamp to allow gas to pass through while preventing water from entering through the opening, and a dustproof film disposed at the opening to allow gas to pass through while preventing dust from entering through the opening. The light-emitting device is not limited to a lamp. In addition, the housing in which the breathable film 1 is disposed can also be a housing of an electronic device or an electronic component other than the light-emitting device. The use of the breathable film 1 is not limited to the above examples. The breathable film 1 can be arranged at the opening in such a way that the first main surface 12 with a relatively small lightness L * faces the inside of the housing. This arrangement is particularly suitable for suppressing light leakage from the light-emitting device through the breathable film 1.

[0109] The breathable film 1 can be manufactured, for example, by applying a coloring solution containing a colorant onto one major surface of the original film before coloring, and then removing the solvent or dispersion medium (hereinafter, the solvent and the dispersion medium are collectively referred to as "solvent") contained in the coloring solution by drying or the like. The application can be carried out by a known coating method. However, the manufacturing method of the breathable film 1 is not limited to the above example. The major surface (coating surface) onto which the coloring solution is applied can become the first major surface 11 with a relatively small lightness L * relatively small first major surface 11.

[0110] The coloring solution may not contain a liquid repellent agent. Although it also depends on the material of the breathable film 1, when the coloring solution contains a liquid repellent agent, sometimes the wettability of the coloring solution to the original film is improved, making it difficult to increase the difference in lightness L * between the first major surface 11 and the second major surface 12.

[0111] When the colorant is a dye, the concentration of the dye in the coloring solution (dyeing solution) is, for example, 1% by weight or more, and can be 2% by weight or more, 3% by weight or more, 4% by weight or more, and further can be 4.5% by weight or more.

[0112] When the coloring solution contains a liquid repellent agent, the compounding amount of the liquid repellent agent is, for example, less than 20 parts by weight with respect to 100 parts by weight of the colorant, and can be 18 parts by weight or less, and further can be 16 parts by weight or less.

[0113] The original film can be formed by a known method. As an example, the original film, which is a PTFE porous film, can be formed, for example, by making a kneaded product of PTFE fine powder and a molding aid into a sheet by extrusion molding and calendering, removing the molding aid, and then further performing stretching. The stretching can be uniaxial stretching. The stretching can be carried out at a temperature exceeding the melting point of PTFE.

[0114] [Breathable member]

[0115] Figure 8A and Figure 8B show an example of the breathable member of the present embodiment. Figure 8B show Figure 8A the cross-section B - B of the breathable member 4. Figure 8A and Figure 8B The breathable member 4 shown in and includes the breathable film 1 and a support member 5 that supports the breathable film 1. In Figure 8A and Figure 8BIn the example, when viewed from a direction perpendicular to the first main surface 11 and the second main surface 12, the shape of the breathable film 1 is rectangular. When viewed from the above direction, the shape of the support member 5 is a shape corresponding to the shape of the peripheral portion of the breathable film 1, specifically, a frame shape. However, as long as the breathable film 1 can be supported by the support member 5, the shapes of the breathable film 1 and the support member 5 are not limited to the above example. For the breathable member 4 provided with the support member 5, the breathable film 1 can be strengthened and the operability can be improved. In addition, the support member 5 can be used as the mounting portion of the breathable film 1.

[0116] Typically, the material of the support member 5 is resin, metal, or a composite material thereof. The support member 5 can also be a double-sided adhesive tape.

[0117] In the lamination of the breathable film 1 and the support member 5, various joining methods such as thermal lamination, heat welding, ultrasonic welding, and joining using an adhesive or binder can be used, for example.

[0118] In Figure 8A and Figure 8B of the breathable member 4, the support member 5 is disposed on one side of the breathable film 1. The support member 5 can also be disposed on both sides of the breathable film 1.

[0119] The breathable member 4 can be a waterproof member having the breathable film 1 as a waterproof film. The breathable member 4 can also be a dustproof member having the breathable film 1 as a dustproof film.

[0120] [Light-emitting device]

[0121] Figure 9A and Figure 9B show an example of the light-emitting device of the present embodiment. Figure 9A and Figure 9B The light-emitting device shown is a vehicle lamp 41. Figure 9A shows the lamp 41 when viewed from the irradiation surface 42 side. Figure 9B shows the lamp 41 when viewed from the side opposite to the irradiation surface 42. Two openings 44 are provided in the housing 43 of the lamp 41, and the breathable film 1 is fixed so as to cover each opening 44. The breathable film 1 is fixed to the housing 43 in such a manner that the first main surface 11 with a relatively small lightness L * faces the inside of the housing 43. In addition, the breathable film 1 covers the opening 44 from the outside of the housing 43. In the lamp 41, by fixing the breathable film 1, the light from the light source 45 is suppressed from passing through the opening 44. In addition, since the second main surface 12 of the breathable film 1 faces the outside of the housing 43, it is also suitable for visual recognition when inspecting the lamp 41.

[0122] Examples of the light-emitting device are a lamp, a signal lamp, and a backlight for electronic devices such as a camera and a display. The light-emitting device can be used in a vehicle. However, the light-emitting device is not limited to the above examples.

[0123] Example

[0124] Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[0125] [Evaluation Method]

[0126] The evaluation method of the breathable film produced in this example is shown.

[0127] (Brightness L * )

[0128] The brightness L of the main surface * By using a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., SE6000) capable of performing evaluation according to the provisions of JIS Z8722:2009, the stimulus value Y of the CIE tristimulus values is measured, and it is converted into L using the conversion formula * =116(Y / Yn) 1 / 3 -16 to obtain L * The evaluation of the brightness L was performed on the first main surface 11 and the second main surface 12, respectively. The measurement conditions are as described above. The evaluation area for obtaining the brightness L * is set as a circle with a diameter of 30 mm (area 706.5 mm * ). 2 )

[0129] Regarding the brightness L * of the first circular region 21 and the second circular region 22 in the second main surface 12, except that each evaluation area is set as a circle with a diameter of 6 mm (area 28.3 mm 2 ), it is obtained in the same manner as the brightness L * of the main surface.

[0130] (Visual light transmittance Y)

[0131] Regarding the visual light transmittance Y, a spectrophotometer (manufactured by Murakami Color Technology Research Institute, integrating sphere type spectral transmittance measuring instrument DOT-3C) capable of performing evaluation according to the provisions of JIS Z8722:2009 is used to measure the stimulus value Y of the CIE tristimulus values, and it is defined as the visual light transmittance Y. The transmitted light from the first main surface 11 to the second main surface 12 and the transmitted light from the second main surface 12 to the first main surface 11 were evaluated respectively. The measurement conditions are as described above. The evaluation area for obtaining the visual light transmittance Y is set as a circle with a diameter of 15 mm (area 176.6 mm 2 ).

[0132] (Water pressure resistance)

[0133] The water pressure resistance (ultimate water pressure resistance) was evaluated by the above method. It should be noted that the evaluation was carried out with the first major surface 11 as the water pressure application surface.

[0134] (Air permeability in the thickness direction)

[0135] The air permeability in the thickness direction was evaluated as Gurley air permeability by the above method. It should be noted that the evaluation was carried out with the first major surface 11 as the pressure application surface.

[0136] [Fabrication of the original film]

[0137] (Original film A)

[0138] 100 parts by weight of PTFE fine powder (manufactured by AGC Inc., CD123E) and 20 parts by weight of ISOPAR M as a molding aid (manufactured by Andoh Parachemie Co., Ltd.) were uniformly mixed. The resulting mixture was compressed using a cylinder and then subjected to plunger extrusion molding to form a sheet. Subsequently, the sheet-like mixture was passed through a pair of metal rollers to be rolled into a thickness of 0.24 mm, and then dried by heating at 170 °C to remove the molding aid, thereby forming a sheet-shaped body. Then, the sheet-shaped body was stretched in the length direction (rolling direction) under the conditions of a stretching temperature of 380 °C and a stretching ratio of 4.2 times to obtain a PTFE porous membrane as the original film A. The obtained porous membrane was a uniaxially stretched film.

[0139] (Original film B)

[0140] 100 parts by weight of PTFE fine powder (manufactured by Daikin Industries, Ltd., F104) and 20 parts by weight of n-dodecane as a molding aid (manufactured by Japan Energy Corporation) were uniformly mixed. The resulting mixture was compressed using a cylinder and then subjected to plunger extrusion molding to form a sheet. Subsequently, the sheet-like mixture was passed through a pair of metal rollers to be rolled into a thickness of 0.2 mm, and then stretched in the width direction at a ratio of 4.5 times, and then dried by heating at 150 °C to remove the molding aid, thereby forming a sheet-shaped body. Then, the sheet-shaped body was stretched in the length direction (rolling direction) under the conditions of a stretching temperature of 300 °C and a stretching ratio of 4 times, then stretched in the width direction under the conditions of a stretching temperature of 150 °C and a stretching ratio of 25 times, and then fired at 400 °C to obtain a PTFE porous membrane as the original film B. The obtained porous membrane was a biaxially stretched film.

[0141] (Examples 1 to 5, Examples 7 to 8, Comparative Examples 2 to 4)

[0142] A mixture of a black dye (manufactured by Orient Chemical Industries, Ltd., SP BLACK 91L, dye concentration: 25% by weight) and a solvent was prepared as a staining solution. The solvent was added in such a way that the concentration of the dye in the staining solution (solid component concentration; the same applies hereinafter) reached the values shown in Table 1 below. The solvent was methyl ethyl ketone (MEK). Then, the prepared staining solution was coated on one major surface of the original film A, and then naturally dried in an atmosphere of 20°C and 50% relative humidity, thereby obtaining the breathable membranes of Examples 1 to 5, Examples 7 to 8, and Comparative Examples 2 to 4 that were colored with the above dye. The coating of the staining solution was carried out using a spreader so as to achieve the coating thickness shown in Table 1.

[0143] [Table 1]

[0144]

[0145] (Example 6)

[0146] A load was applied in the thickness direction to the breathable membrane formed by overlapping the breathable membrane of Comparative Example 4 and the original film A by making a 2-kg roller reciprocate once, thereby obtaining the breathable membrane of Example 6 composed of two layers of PTFE porous membranes.

[0147] (Comparative Example 1)

[0148] A mixture of a black dye (manufactured by Orient Chemical Industries, Ltd., SP BLACK 91L, dye concentration: 25% by weight) and a solvent was prepared as a staining solution. The solvent was added in such a way that the concentration of the dye in the staining solution reached 2.1% by weight. The solvent was a mixed solution of toluene and methyl ethyl ketone (MEK). The mixing ratio was set to toluene:MEK = 75:25 by volume. Then, the prepared staining solution was coated on one major surface of the original film B, and then naturally dried in an atmosphere of 20°C and 50% relative humidity, thereby obtaining the breathable membrane of Comparative Example 1 that was colored with the above dye. The coating of the staining solution was carried out using a spreader with a coating thickness of 17 μm.

[0149] (Comparative Example 5)

[0150] The original film A was used as Comparative Example 5.

[0151] The evaluation results of the breathable membranes of the examples and comparative examples are shown in Tables 2A and 2B below.

[0152] [Table 2A]

[0153]

[0154] [Table 2B]

[0155]

[0156] Next, for the breathable films of Example 1, Example 7, Example 8, and Comparative Example 1, the lightness L of the first circular region and the second circular region in the second major surface was evaluated. * The results are shown in Table 3 below. In addition, when evaluating the lightness L of the first circular region and the second circular region, * two more circular regions (a third circular region and a fourth circular region; both are circles with a diameter of 6 mm) were randomly set, and the lightness L of each was evaluated. * The lightness L of the further circular regions is also shown in Table 3. *

[0157] [Table 3]

[0158] (Example 1)

[0159]

[0160] ※ The absolute value d2 of the difference in lightness L ＊ is 9.38

[0161] (Example 7)

[0162]

[0163] ※ The absolute value d2 of the difference in lightness L ＊ is 22.69

[0164] (Example 8)

[0165]

[0166] ※ The absolute value d2 of the difference in lightness L ＊ is 8.22

[0167] (Comparative Example 1)

[0168]

[0169] ※ The absolute value d2 of the difference in lightness L ＊ is 1.78

[0170] Industrial Applicability

[0171] The breathable film of the present invention can be used for the same applications as conventional breathable films.​

Claims

1. A breathable film, the breathable film having breathability in the thickness direction, wherein, the breathable film is colored, the breathable film has a first major surface and a second major surface located on the opposite side of the first major surface, the second major surface exhibits a higher lightness than the first major surface, the absolute value of the difference in lightness between the first major surface and the second major surface is 1.5 or more and 76 or less, the lightness of the second major surface is 20 or more and 95 or less, the visual transmittance of the transmitted light from the first major surface to the second major surface is 0.015 or less, Among them, the lightness is the CIE1976 L specified in JIS Z8781-4:2013 * , a * , b * the lightness L of the color space * , the visual transmittance is represented by the value of the stimulus value Y of the CIE tristimulus values specified in JIS Z8781-3:2016.

2. The breathable film according to claim 1, wherein, The second major surface has a first circular region and a second circular region, both the first circular region and the second circular region being circles with a diameter of 6 mm, the first circular region and the second circular region are respectively defined as the region with the highest lightness and the region with the lowest lightness on the second major surface, the absolute value of the difference in lightness between the first circular region and the second circular region is 2.0 or more.

3. The breathable film according to claim 1, wherein The second major surface has a first strip region and a second strip region, the second strip region is adjacent to the first strip region, and the lightness of the second strip region is less than the lightness of the first strip region.

4. The breathable film according to claim 1, wherein, The breathable film comprises a polytetrafluoroethylene (PTFE) porous film.

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

6. The breathable film according to claim 1, wherein, The breathable film comprises a uniaxially stretched film.

7. The breathable film according to claim 1, wherein, The water pressure resistance of the breathable film evaluated by the water resistance test specified in JIS L1092:2009 is 5 kPa or more.

8. The breathable film according to claim 1, wherein, In terms of the air permeability (Gurley air permeability) evaluated by the air permeability measurement method B (Gurley method) specified in JIS L1096:2010, the breathability in the thickness direction is 200 seconds / 100 mL or less.

9. The breathable film according to claim 1, wherein, The breathable film has a thickness greater than 100 μm.

10. A breathable member, wherein, The breathable member comprises: the breathable film according to any one of claims 1 to 9; and a support member that supports the breathable film.

11. A light-emitting device, wherein, The light-emitting device comprises: a housing having an opening; a light source housed in the housing; and a breathable film fixed to the housing so as to cover the opening, the breathable film being the breathable film according to any one of claims 1 to 9.

12. The light-emitting device according to claim 11, wherein, The breathable film is fixed to the housing with the first major surface facing the inside of the housing.

Images