Vehicle lighting

Abstract

A vehicle lamp (1) comprises: a lamp body (2) having an opening in the irradiation direction; a front surface cover (3) covering the opening to divide a lamp chamber (4), and having an anti-fog film (5) with synthetic resin as a main component on the inner surface; a light source (12) arranged in the lamp chamber (4); and a silicone resin component (16) arranged in the lamp chamber (4), wherein the content of cyclic low molecular weight siloxanes of D3 to D20 in the silicone resin component (16) is 0 to 300 ppm by mass conversion.

Description

Technical Field

[0001] The present invention relates to a vehicle lamp, and more particularly to a vehicle lamp having an anti-fog film on the inner surface of a front cover. Background Art

[0002] Conventionally, silicone resin parts have been used in vehicle lamps. In particular, in recent years, silicone resin lenses have been used in view of the complexity of the shape and heat resistance (see Patent Document 1).

[0003] Silicone resin is known to release cyclic low molecular weight siloxane (hereinafter referred to as low molecular weight siloxane) as external gas. The cyclic low molecular weight siloxane is a residue of the silicone resin raw material that remains unreacted during the silicone resin molding. In particular, reducing the residual amount of low molecular weight siloxane D3 to D10 becomes an indicator of the quality standard of silicone resin. In vehicle lamps, generally speaking, a low molecular weight siloxane reduction type (low siloxane management level) silicone resin is used in which the content of low molecular weight siloxane D3 to D10 is reduced to less than or equal to 300 ppm.

[0004] On the other hand, in vehicle lamps, a structure with an anti-fog film on the inner surface of the front cover is mostly adopted (refer to patent document 2). However, in recent years, in vehicle lamps with anti-fog films, the problem of reducing the anti-fog performance caused by water flow marks on the front cover is being studied.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-102389

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-093564 Summary of the invention

[0007] Therefore, the present inventors have conducted studies and found that, in conventional vehicle lamps, although low-molecular-weight siloxane-reduced type silicone resin parts are used, a decrease in anti-fogging performance is sometimes observed.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a decrease in anti-fogging performance in a vehicle lamp using a silicone resin component.

[0009] In order to achieve the above-mentioned purpose, a vehicle lamp involved in one embodiment of the present invention comprises: a lamp body, which has an opening in the irradiation direction; a front surface cover, which covers the opening and divides the lamp chamber, and has an anti-fog film with synthetic resin as the main component on the inner surface; a light source, which is arranged in the lamp chamber; and a silicone resin component, which is arranged in the lamp chamber, and the content of cyclic low molecular weight siloxanes D3 to D20 in the silicone resin component is 0 to 300 ppm by mass conversion.

[0010] In the existing vehicle lamps, silicone resin parts are used, the content of D3 to D10 is managed, but the content of D11 to D20 is not considered. According to the above structure, the content of low molecular weight siloxanes D3 to D20 in the silicone resin parts is suppressed to less than 300 ppm in total, thereby reducing the amount of low molecular weight siloxanes released from the silicone resin parts in the lamp chamber that becomes high temperature when the lamp is lit. As a result, the influence of low molecular weight siloxanes on the anti-fog film formed on the inner surface of the front surface cover can be reduced, and the reduction of anti-fog performance can be prevented.

[0011] In the above aspect, it is preferable that a lens is provided in the lamp chamber, and at least one of the silicone resin members is the lens.

[0012] In the above aspect, it is preferred that the content of the cyclic low-molecular siloxanes D11 to D20 in the silicone resin member is 0 to 290 ppm in terms of mass.

[0013] In the above embodiment, it is preferred that the content of the cyclic low-molecular-weight siloxane in D3 to D20 is 0 to 20 ppm in terms of mass.

[0014] In the above embodiment, it is preferred that the content of the cyclic low-molecular-weight siloxane in D11 to D20 is 0 to 11 ppm in terms of mass.

[0015] The anti-fog film preferably comprises an anti-fog coating, and the anti-fog coating comprises any surfactant of anionic, cationic and nonionic types.

[0016] In this specification, the "low molecular weight siloxane content" (unit: ppm) of the silicone resin component refers to the specific cyclic dimethyl siloxane (molecular formula SiO(CH 3 ) 2 ), and in the case of the low molecular weight siloxane content of D3 (trimer) to D20 (20-mer), it refers to the total content (mass conversion) of D3 to D20.

[0017] Effects of the Invention

[0018] According to the vehicle lamp according to the above aspect, in the vehicle lamp using the silicone resin member, it is possible to prevent a decrease in anti-fog performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic front view of a vehicle lamp according to an embodiment of the present invention.

[0020] Figure 2A yes Figure 1 The schematic cross-sectional view of the vehicle lamp taken along the line IIA-IIA is shown.

[0021] Figure 2B yes Figure 1 An enlarged view of the scanning mechanism of the vehicle lamp is shown.

[0022] Figure 3 It is a schematic diagram showing the outline of a device for carrying out the anti-fog performance test of the above-mentioned vehicle lamp. DETAILED DESCRIPTION

[0023] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these.

[0024] In addition, in the following description, the terms indicating the up, down, left, right, etc. directions related to the vehicle lamp (hereinafter referred to as "lamp") refer to the directions when the lamp is installed on the vehicle and viewed from the front unless otherwise specified. That is, the "front" of the lamp refers to the front of the vehicle, the left of the lamp refers to the right of the vehicle, and the right of the lamp refers to the left of the vehicle. In addition, in the accompanying drawings, arrows U-D indicate the up and down directions when the lamp is viewed from the front, arrows F-B indicate the front and rear directions, and arrows L-R indicate the left and right directions.

[0025] (Implementation Method)

[0026] (The overall structure of the lamp)

[0027] Figure 1 It is a front view schematically showing a general structure of a lamp 1 according to an embodiment of the present invention. Figure 2A It is the edge of lamp 1 Figure 1 The lamp 1 is a sectional view taken along the line IIA-IIA of FIG. 1 . The lamp 1 is a left or right headlamp unit of a vehicle headlamp device having a pair of headlamp units arranged on the left and right sides in front of the vehicle. The pair of headlamp units have substantially the same structure.

[0028] The lamp 1 roughly includes a lamp body 2 , a front cover 3 , a high beam unit HU, a low beam unit LU, and a bracket unit 6 .

[0029] The lamp body 2 is formed of synthetic resin such as polypropylene or acrylonitrile-styrene-acrylate (ASA), and has a box-like shape that opens forward in the irradiation direction. The front cover 3 closes the opening of the lamp body 2 to define a lamp chamber 4 .

[0030] The front cover 3 is made of, for example, a synthetic resin having excellent light transmittance and impact resistance. As a material, for example, polycarbonate (PC), polymethyl methacrylate (PMMA), etc. can be used. The front cover 3 can be made transparent, and a lens cutoff portion (not shown) is formed on a part of the inner surface.

[0031] An anti-fog film 5 is formed on the inner surface of the front cover 3. The anti-fog film 5 can be formed, for example, by using a spray gun, while moving the nozzle of the spray gun along the inner surface of the front cover 3, spraying a light-transmitting anti-fog coating P from the nozzle onto the inner surface, and curing it by heating with warm air or the like.

[0032] As the anti-fog coating P, for example, a known anti-fog coating comprising any of anionic, cationic and nonionic surfactants, a resin such as acrylic resin and a curing agent (catalyst) can be used. For example, it can be a curing type anti-fog coating described in Japanese Patent Application Laid-Open No. 2005-146227.

[0033] The anti-fog performance of the anti-fog coating P containing a surfactant is exerted in the following manner, that is, the hydrophobic group of the surfactant is oriented on the inner surface of the front surface cover 3, and the hydrophilic group is oriented to the outside, thereby reducing the surface tension between the water and the front surface cover 3 at the contact point of the attached water droplet, and reducing the contact angle of the contact point. If the cyclic low molecular weight siloxane has low polarity and adheres to the anti-fog film, it will reduce the surface tension reduction effect of the anti-fog film 5.

[0034] The high-beam unit HU and the low-beam unit LU are arranged in the lamp chamber 4 . The high-beam unit HU and the low-beam unit LU are held by a bracket unit 6 .

[0035] The high beam unit HU is a variable light distribution headlamp (ADB: Adaptive Driving Beam) configured to form a predetermined shape and light distribution with light emitted forward, and can form not only high beam light distribution but also variable light distribution according to the driving condition of the vehicle and the surrounding conditions.

[0036] The high beam unit HU includes a light source 12, a scanning mechanism 14, a condenser lens 16 for condensing the light emitted from the light source 12 and injecting the light into the scanning mechanism 14, a control unit 18 for controlling the scanning mechanism 14 and the light source 12, a projection lens 22, and a lens holder 24. These components are supported by the carriage unit 6 by an appropriate method.

[0037] The light source 12 is a semiconductor light emitting element such as LED (Light Emitting Diode) or EL (Electro Luminescence), but the light source 12 is not limited thereto and may be an LD (Laser Diode) element.

[0038] Scanning mechanism 14 Figure 2BAs shown in the enlarged view in FIG. 1 , the rotating reflector has a reflecting surface 15, which is composed of three reflecting sheets 14a of the same shape arranged around a cylindrical rotating part 14b, and reflects the light emitted from the light source 12 while rotating to form a desired light distribution pattern. The rotating axis r is inclined relative to the optical axis M of the light source and is arranged on a plane including the optical axis M and the light source 12.

[0039] The shape of the reflection sheet 14a is configured so that a secondary light source formed by reflection of the light source 12 is formed near the rear focus of the projection lens 22. Furthermore, the reflection sheet 14a has a shape that is distorted as the angle between the optical axis Ax and the reflection surface 15 changes as it moves toward the circumferential direction centered on the rotation axis r. The scanning mechanism 14 reflects the light reflected by the reflection surface 15 in a manner that changes its direction while rotating around the rotation axis r, thereby causing the light from the light source 12 to scan in the left-right direction.

[0040] The projection lens 22 is made of a light-transmitting resin such as polycarbonate or PMMA, and irradiates the light incident from the reflection sheet 14 a forward.

[0041] As a result, the light from the light source 12 is focused by the focusing lens 16 and incident on the scanning mechanism 14, that is, the rotating reflector. The light incident on the rotating reflector is scanned left and right by the reflecting surface 15. The light from the rotating reflector is incident on the projection lens 22 and irradiated forward. As described above, the high beam unit HU overlaps the incident light at each position of the projection lens 22 to form a predetermined light distribution pattern.

[0042] The low beam unit LU includes a projection type optical unit Lo1 including a light source as a light emitting element, a reflector, and a projection lens. The optical unit Lo1 has the same structure as the low beam unit described in Japanese Patent Application Laid-Open No. 2014-078476, for example, and thus detailed description thereof is omitted.

[0043] The low-beam unit LU includes an optical unit Lo1 and an optical unit Lo2 having the same structure as the optical unit Lo1 , and the low-beam light distribution is formed in front of the vehicle by the two optical units Lo1 and Lo2 .

[0044] The bracket unit 6 has a base plate 6a along the front shape of the lamp 1 and three adjustment screws E provided at three locations vertically. The optical axes of the high beam unit HU and the low beam unit LU are adjusted in the horizontal direction and the vertical direction by rotating the adjustment screws E.

[0045] Reference numeral 8 in the lamp chamber 4 denotes a protruding portion, which surrounds the low beam unit LU and the high beam unit HU so as to cover the periphery thereof.

[0046] (Silicone resin parts)

[0047] Here, the silicone resin component, i.e., the focusing lens 16, in the lamp 1 according to the present embodiment is described. The focusing lens 16 is made of a highly transparent silicone resin for optical components as a base polymer, and a catalyst such as an organic peroxide or a platinum compound is used as a crosslinking agent, and is manufactured by injection molding. The total amount of D3 to D20 of the content of low molecular weight siloxane in the focusing lens 16 is 0 to 300 ppm. In addition, the total amount of D11 to D20 is preferably 0 to 290 ppm. The content of low molecular weight siloxane D3 to D20 is preferably 0 to 20 ppm. The content of D11 to D20 is more preferably 0 to 11 ppm.

[0048] The content of low molecular weight siloxane can be controlled, for example, as follows.

[0049] (1) Use a commercially available low-siloxane management grade silicone resin in which low-molecular-weight siloxane in the material components is removed as much as possible.

[0050] (2) After injection molding, the low molecular weight siloxane is released and removed by heating at a predetermined temperature (e.g., 150°C to 200°C) for a predetermined time (e.g., 2 to 4 hours). The heating process as described above is called secondary vulcanization, and the residual low molecular weight siloxane content can be adjusted by adjusting the heating temperature and heating time.

[0051] (3) The silicone resin component after injection molding is immersed in an organic solvent and left for a predetermined time (e.g., 6 hours) to dissolve the low molecular weight siloxane contained in the silicone resin component, thereby reducing the low molecular weight siloxane content. As the organic solvent, ketone solvents such as acetone, olefin solvents such as n-hexane, alcohols such as methanol, etc. can be used. The residual low molecular weight siloxane content can be adjusted by adjusting the type of organic solvent, the immersion temperature, and the immersion time.

[0052] (experiment)

[0053] Next, in order to evaluate the anti-fog performance related to the lamp 1 involved in this embodiment, condenser lenses 16 with different low-molecular siloxane contents were produced. In addition, the concentration of low-molecular siloxane in the produced condenser lenses 16 was measured, and an anti-fog performance test was performed using an oil bath. The anti-fog performance test using an oil bath is a test in which a test piece of a silicone resin component is covered with a plate applied with an anti-fog coating, sealed in a glass beaker, and heated to a temperature equivalent to the lighting state of the lamp, so that a state equivalent to when the vehicle lamp is lit can be observed.

[0054] (Production of silicone resin parts (condenser lens))

[0055] The focusing lens 16 as a silicone resin component is manufactured by injection molding using a silicone elastomer having a material grade as described in Table 1 and post-processing under the conditions shown in Table 1 for each lamp of Examples 1, 2 and Comparative Examples 1, 2 described in Table 1.

[0056] (Determination of Low-Molecular-Weight Siloxane Content)

[0057] The content of low molecular weight siloxane in the produced silicone resin member was measured in the following manner.

[0058] (1) First, each silicone resin member is cut into square pieces of 1 to 2 mm.

[0059] (2) Measure the quality of the fragment.

[0060] (3) Extraction is performed with a specified amount of n-hexane.

[0061] (4) The entire amount of the extraction solvent was separated by a gas chromatograph (Gas Chromatograph System 7980B manufactured by Agilent Technologies Inc.) using a capillary column at an injection temperature of 280°C and helium as a carrier gas (mobile phase), and detected by a FID (Flame Ionization Detector).

[0062] (5) Based on the results, the low molecular weight siloxanes in each of D3 to D10 and D11 to D20 were quantitatively determined, and the total amount of each was calculated. The low molecular weight siloxane content (ppm) was calculated based on the mass determined in (2).

[0063] (Anti-fog performance test)

[0064] The anti-fog performance test was carried out using the following equipment and according to the following method. Figure 3 1 is a schematic diagram showing an outline of the anti-fog performance test equipment 30 .

[0065] equipment:

[0066] Oil bath 31 (capacity 38L, manufactured by Thomas Scientific Instruments Co., Ltd.)

[0067] Glass beaker 32 (volume 1L, outer diameter φ95mm×height 160mm, glass plate thickness t2.1mm)

[0068] Perforated glass plate 33 (a hole with a diameter of 40 mm is opened in the center of a square glass plate of 100 mm × 100 mm × thickness t1.9 mm)

[0069] PC board 34 with anti-fog coating 34a (a square PC board of 100 mm×100 mm×t3 mm is coated with an acrylic anti-fog coating P containing an anionic surfactant)

[0070] method:

[0071] (1) The silicone resin member is cut into square pieces of 1 to 2 mm to prepare test pieces 35 .

[0072] (2) A test piece 35 weighing 0.8 g is placed in the glass beaker 32 .

[0073] (3) A perforated glass plate on which the PC plate 34 with anti-fog coating is attached is placed in the glass beaker 32 .

[0074] (4) The glass beaker 32 was heated at 130° C. for 20 hours in an oil bath 31 having a depth of 64 mm from the bottom surface thereof.

[0075] (5) After heating, the anti-fog coated PC board 34 was removed, steam at about 40° C. was blown for 20 seconds, and the state of the anti-fog film was visually observed.

[0076] (6) The state of the antifogging film was classified into the following five levels and evaluated. In addition, a level 4 or higher was regarded as passing.

[0077] Level 1: produces fog, unclear.

[0078] Level 2: Mist is generated but becomes a water film.

[0079] Level 3: The whole area produces mist for a moment, but immediately turns into a water film.

[0080] Level 4: A portion of the mist is generated, but it immediately turns into a water film.

[0081] Level 5: No fog.

[0082] The above experimental results are summarized in Table 1.

[0083]

Table 1

[0084] Table 1 Anti-fog performance test results

[0085]

[0086] *General lens level: D3-D10 less than or equal to 1770ppm, low siloxane management level D3-D10 less than or equal to 300ppm

[0087] As is clear from Table 1, no effect on the anti-fog performance was found in the reference examples that did not use silicone resin components. In addition, in Examples 1 and 2 where the low molecular weight siloxane concentration of D3 to D20 was less than or equal to 300 ppm, no fog was generated in the anti-fog performance test, or even if fog was generated in a part, it immediately became a water film, and the anti-fog performance did not decrease. On the other hand, as shown in Comparative Example 2, in the so-called conventional low molecular weight siloxane content of D3 to D10 of 17 ppm, D3 to D20 was less than or equal to 300 ppm.

[0088] The structure of D20 having a low molecular weight siloxane concentration exceeding 300 ppm generates fog in the anti-fog performance test, which is regarded as a decrease in the anti-fog performance.

[0089] Therefore, in the anti-fog performance test, it can be known that the reason for failure is the low molecular weight siloxane released from the silicone resin component, that is, the focusing lens 16. In addition, in order to ensure the anti-fog performance after long-term lighting, as shown in Examples 1 and 2, it can be known that the low molecular weight siloxane content of D3 to D20 of the silicone resin component is preferably less than or equal to 300ppm (the low molecular weight siloxane concentration of D11 to D20 is less than or equal to 290ppm). In addition, as shown in Example 2, it can be known that the low molecular weight siloxane content of D3 to D20 is preferably less than or equal to 20ppm (the low molecular weight siloxane concentration of D11 to D20 is less than or equal to 11ppm).

[0090] The following is the reason why the silicone resin parts are preferably managed with attention paid to the content of low molecular weight siloxanes D3 to D20, especially D11 to D20. The distribution of low molecular weight siloxanes released from silicone resin products varies depending on the heating temperature. At a heating temperature of 50°C, a large amount of D3 to D10 is released, centered on D5, but as the heating temperature becomes higher, the amount of low molecular weight siloxanes with large molecular weights increases, and at 300°C, D14 to D20 are dominant. The temperature in the lamp chamber 4 of the vehicle lamp 1 is relatively high, especially around the light source, sometimes reaching 100 to 150°C, and it is conceivable that the amount of D11 to D20 released is large. Therefore, by paying attention to the content of D11 to D20 siloxanes released and managing the content of D3 to D20 low molecular weight siloxanes contained in the silicone resin parts, the total amount of released low molecular weight siloxanes can be indirectly managed.

[0091] In addition, in the present embodiment, the content of low molecular weight siloxane contained in the silicone resin component is managed to prevent the reduction of anti-fog performance. The reduction of anti-fog performance of the anti-fog film is directly related to the concentration of low molecular weight siloxane in the air in the lamp chamber, but it is difficult to manage it. On the other hand, in the present embodiment, by managing the content of low molecular weight siloxane, the total amount of low molecular weight siloxane released into the lamp chamber can be indirectly managed. Therefore, even if the number and size of the silicone resin components or the capacity of the lamp chamber change, the structure of the silicone resin component can be reliably designed so as not to hinder the anti-fog performance.

[0092] In addition, in this embodiment, the surface tension reduction effect between water droplets and the anti-fog film can be reduced by reducing the low molecular weight siloxane, so that the reduction in anti-fog performance can be suppressed, especially when an anti-fog coating containing a surfactant is used as the anti-fog coating.

[0093] In the above description, the condenser lens 16 is cited as an example of the silicone resin member, but the silicone resin member in the present invention is not limited thereto and naturally includes various silicone resin members used in vehicle lamps.

[0094] Although preferred embodiments of the present invention have been described above, the above embodiments are merely examples of the present invention, and the present invention can be combined based on the knowledge of those skilled in the art, and the combined embodiments are also included in the scope of the present invention.

[0095] This application is based on Japanese patent application (Japanese Patent Application No. 2020-81466) filed on May 1, 2020, the contents of which are incorporated herein by reference.

Claims

1. A vehicle lamp, comprising: A lamp body having an opening in the irradiation direction; A front cover, which covers the opening to divide the lamp chamber, and has an anti-fog film with synthetic resin as the main component on the inner surface; a light source disposed in the lamp chamber; and An organic silicon resin component is disposed in the lamp chamber, The content of the cyclic low molecular weight siloxanes D3 to D20 in the silicone resin component is 0 to 300 ppm by mass conversion. The content of the cyclic low-molecular siloxanes D11 to D20 in the silicone resin member is 0 to 290 ppm in terms of mass.

2. The vehicle lamp according to claim 1, in, A lens is disposed in the lamp chamber, At least one of the silicone resin members is the lens.

3. The vehicle lamp according to claim 1 or 2, in, The content of the cyclic low molecular weight siloxane in D3 to D20 is 0 to 20 ppm in terms of mass.

4. The vehicle lamp according to claim 1 or 2, in, The cyclic low-molecular-weight siloxane content of D11 to D20 is 0 to 11 ppm in terms of mass.

5. The vehicle lamp according to claim 1 or 2, in, The anti-fog film includes an anti-fog coating, and the anti-fog coating includes any surfactant of anionic, cationic and nonionic types.

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