JP2012248646A - Flexible printed board and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reflectivity, makes a flexible printed board less noticeable even when the printed board appears in a reflector, and prevent the occurence of cracks resulting from processing.SOLUTION: A flexible printed board 1 has a board body 2 having a base material 3, a conductor circuit 4 formed on a surface of the base material 3, and a cover material 6 laminated on the upper side of the conductor circuit 4 so as to cover the conductor circuit 4. A metallic coating layer 7 having the thickness of 1 to 10 μm is laminated on a surface of the board body 2. The metallic coating layer 7 is formed by adding aluminum particles to a synthetic resin and is provided so as to avoid a light emitting element attachment part 2a of the board body 2.

Description

  The present invention relates to a flexible printed circuit board (FPC) that is applied to various applications such as automobile lighting applications and general lighting applications, and an illumination device including the flexible printed circuit board.

  Conventionally, as this type of flexible printed circuit board 1, as shown in FIG. 10, a base material 3, a conductor circuit 4 formed on the surface of the base material 3, and a conductor circuit 4 above the conductor circuit 4 are provided. What has the board | substrate body 2 containing the cover material 6 laminated | stacked through the contact bonding layer 5 so that it covers may be used widely. Further, in applications where high heat dissipation is required for the flexible printed circuit board 1, as shown in FIG. 11, a structure in which a heat sink layer 12 is laminated on the back surface of the substrate body 2 having the same configuration as described above is used.

  In any flexible printed circuit board 1, a white coating layer 13 is often laminated on the surface of the substrate body 2 for the purpose of increasing the reflectance (see, for example, Patent Document 1).

JP 2010-123768 (paragraphs [0034] [0047] column)

  However, the flexible printed circuit board 1 on which the white coating layer 13 is laminated has the following problems.

  First, as shown in FIG. 12, the light emitted from the light emitting diode 8 is used in the lighting device 14 in which the light emitting diode 8 is mounted on the flexible printed circuit board 1 and attached to the housing 10 of the automobile lamp. The reflector 9 may be installed on the optical axis. In this case, when the light emitting diode 8 is turned off, the flexible printed circuit board 1 is reflected on the reflector 9 and becomes conspicuous.

  Second, in order to conceal the base of the white coating layer 13, that is, the substrate body 2 with the white coating layer 13, so that the color of the substrate body 2 (such as orange) does not appear, It is necessary to increase the thickness to about 20 μm. As a result, when the flexible printed board 1 is subjected to bending or punching, cracks are likely to occur in the white coating layer 13 (particularly, the processed end).

  In view of such circumstances, the present invention provides a flexible printed circuit board that can increase the reflectivity and is inconspicuous even when reflected on a reflector, and can suppress the occurrence of cracks caused by processing. This is the first purpose. A second object is to provide a lighting device including such a flexible printed circuit board.

  In order to achieve such an object, the present inventor has paid attention to imparting a metallic luster to the surface layer portion of the flexible printed circuit board in accordance with the surface attribute of the reflector, and has completed the present invention.

  That is, the invention described in claim 1 is a substrate including a base material, a conductor circuit formed on the surface of the base material, and a cover material laminated on the upper side of the conductor circuit so as to cover the conductor circuit. A flexible printed circuit board having a main body, wherein a metallic coating layer having a thickness of 1 to 10 μm is laminated on a surface of the substrate main body.

  The invention according to claim 2 is characterized in that, in addition to the structure according to claim 1, the metallic coating layer is obtained by adding aluminum particles to a synthetic resin.

  The invention described in claim 3 is characterized in that, in addition to the configuration described in claim 1 or 2, the metallic coating layer is provided avoiding a light emitting element mounting portion of the substrate body.

  According to a fourth aspect of the present invention, in addition to the structure according to any one of the first to third aspects, a heat sink layer is laminated on the back surface of the substrate body.

  The invention according to claim 5 is characterized in that, in addition to the configuration according to claim 4, the heat sink layer is made of copper.

  According to a sixth aspect of the present invention, there is provided a lighting device in which a light emitting element is attached to the light emitting element attaching portion of the flexible printed board according to any one of the first to fifth aspects.

  The invention described in claim 7 is characterized in that, in addition to the configuration described in claim 6, a reflector is provided on the optical axis of the light emitted from the light emitting element.

  According to an eighth aspect of the invention, in addition to the configuration of the sixth or seventh aspect, when the flexible printed circuit board is bent, the light emitted from the light emitting element is reflected on the surface of the metallic coating layer. The light is condensed in a specific direction.

  According to a ninth aspect of the invention, in addition to the configuration of the eighth aspect, the flexible printed circuit board is formed in a concave shape with the metallic coating layer as an inner surface side, and the light emission on the inner surface side of the flexible printed circuit board. An element is arranged.

  The invention described in claim 10 is characterized in that, in addition to the structure described in any one of claims 6 to 9, the light emitting element is a light emitting diode.

  According to the flexible printed circuit board and the lighting device according to the present invention, the metallic coating layer in the surface layer portion of the flexible printed circuit board exhibits a metallic luster, so that the reflectance of the flexible printed circuit board can be increased.

  Moreover, since the surface attribute of the metallic coating layer in the surface layer part of a flexible printed circuit board approximates the surface attribute of the reflective surface of a reflector, even if a flexible printed circuit board is reflected in a reflector, it can be made not conspicuous.

  Furthermore, since the metallic coating layer in the surface layer portion of the flexible printed board exhibits a high hiding power, the metallic coating layer can be made thin while hiding the base of the metallic coating layer. Therefore, it is possible to suppress the occurrence of a situation in which the metallic coating layer is cracked as the flexible printed circuit board is processed.

1 is a cross-sectional view of a flexible printed board according to Embodiment 1 of the present invention. FIG. 6 is another cross-sectional view of the flexible printed board according to the first embodiment. It is a schematic diagram which shows the use condition of the illuminating device using the flexible printed circuit board concerning Embodiment 1. FIG. It is a graph which shows the influence which the incident angle of incident light (S polarized light and P polarized light) with a wavelength of 400 nm exerts on the reflectance. It is a graph which shows the influence which the incident angle of incident light (S polarized light and P polarized light) with a wavelength of 500 nm exerts on the reflectance. It is a graph which shows the influence which the incident angle of incident light (S polarized light and P polarized light) with a wavelength of 600 nm exerts on the reflectance. It is a graph which shows the influence which the incident angle of incident light (S polarized light and P polarized light) with a wavelength of 700 nm exerts on the reflectance. It is sectional drawing of the flexible printed circuit board concerning Embodiment 2 of this invention. It is a schematic diagram which shows the use condition of the illuminating device using the flexible printed circuit board concerning Embodiment 3 of this invention, Comprising: (a) is a figure at the time of mounting a light emitting diode in the center part of a flexible printed circuit board, (b) ) Is a view when a light emitting diode is mounted in the vicinity of the end of the flexible printed circuit board. It is sectional drawing which shows an example of the conventional flexible printed circuit board. It is sectional drawing which shows another example of the conventional flexible printed circuit board. It is a schematic diagram which shows the use condition of the illuminating device using the conventional flexible printed circuit board.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

  1 to 7 show a first embodiment of the present invention. In the first embodiment, the light emitting diode 8 is used as an example of the light emitting element. In FIG. 1 and FIG. 2, the dimensional ratio of each component is not necessarily accurate because it is illustrated with emphasis on ease of understanding.

  As shown in FIG. 3, the lighting device 14 includes a flexible printed circuit board 1 that is attached to a housing 10 of a lamp for an automobile (specifically, a headlight or the like), and the flexible printed circuit board 1 includes a light emitting diode. 8 is implemented. Further, a reflector 9 is installed on the optical axis of the light emitted from the light emitting diode 8, and when the light emitting diode 8 is turned on, the light is reflected by the reflecting surface 9a of the reflector 9 to be in a specific direction (left in FIG. 3). It is configured to proceed to

  Here, the flexible printed circuit board 1 has a board body 2 as shown in FIG. The substrate body 2 has a base material 3 made of a polyimide film having a predetermined thickness (for example, 25 μm), and a predetermined thickness (for example, 35 μm) formed on the surface of the base material 3 (upper surface in FIG. 1). A conductor circuit 4 made of copper foil, and a cover material 6 made of a polyimide film having a predetermined thickness (for example, 13 μm) laminated on the upper side of the conductor circuit 4 via an adhesive layer 5 so as to cover the conductor circuit 4; It is composed of

  Further, as shown in FIG. 2, a metallic coating layer 7 having a predetermined thickness (1 to 10 μm, preferably 2 to 4 μm) is attached to the surface of the substrate body 2 (upper surface in FIG. 1). Therefore, the light emitting element mounting portion 2a of the substrate body 2 is stacked so as to avoid it. The metallic coating layer 7 is obtained by adding aluminum particles to a synthetic resin (for example, acrylic resin, epoxy resin, urethane resin, etc.). If the metallic coating layer 7 is too thin, the underlying hiding power is reduced as will be described later, so that the color of the substrate body 2 is easily revealed. On the contrary, if the metallic coating layer 7 is too thick, cracks are likely to occur with bending of the flexible printed circuit board 1 as will be described later.

  As described above, the flexible printed circuit board 1 is provided with the metallic coating layer 7 on the surface portion thereof, and the metallic coating layer 7 exhibits metallic luster. Therefore, when the light emitting diode 8 is turned on, the light emitting diode 8 is turned on. The reflectance of the flexible printed circuit board 1 can be increased by reflecting the light at the metallic coating layer 7.

  Further, the flexible printed circuit board 1 is provided with a metallic coating layer 7, that is, a layer approximating the surface attribute of the reflecting surface 9a of the reflector 9, on the surface layer portion. Even if the printed circuit board 1 is reflected on the reflecting surface 9a of the reflector 9, it can be made inconspicuous.

  Further, the metallic coating layer 7 has a transmittance lower than that of white, and even if it is a thin film, it is considered that light does not reach the substrate, so that the hiding power is larger than that of the conventional white coating layer 13. Therefore, even if the metallic coating layer 7 is not made too thick, the base, that is, the substrate body 2 can be concealed by the metallic coating layer 7 so that the color (such as orange) of the substrate body 2 does not appear. . As a result, even when bending or punching is performed on the flexible printed circuit board 1, it is possible to suppress the occurrence of a situation in which the metallic coating layer 7 is cracked due to its thickness.

  In addition, the metallic coating layer 7 is laminated so as to avoid the light emitting element mounting portion 2a of the substrate body 2 as described above, even though it exhibits conductivity due to the aluminum particles that are its components. There is no fear of short circuiting with the conductor circuit 8 or the conductor circuit 4.

  In order to confirm the above-described first effect (improvement of the reflectance of the flexible printed circuit board 1), a flexible printed circuit board 1 (hereinafter referred to as Example 1) in which a metallic coating layer 7 is laminated on the surface of the substrate body 2; A prototype of a flexible printed circuit board 1 (hereinafter referred to as “Comparative Example 1”) in which a white coating layer 13 is laminated on the surface of the substrate body 2 was measured, and the reflectance was measured for each of Example 1 and Comparative Example 1. At this time, with respect to four types of wavelengths (400 nm, 500 nm, 600 nm, and 700 nm), the incident angle of each of incident light (S-polarized light and P-polarized light) is changed in four steps (15 °, 30 °, 45 °, and 60 °). The reflectance was measured.

  The measurement results are collectively shown in graphs in FIGS. 4 is a graph when the wavelength of incident light is 400 nm, FIG. 5 is a graph when the wavelength of incident light is 500 nm, and FIG. 6 is a graph when the wavelength of incident light is 600 nm. FIG. 7 is a graph when the wavelength of incident light is 700 nm. In these graphs, the horizontal axis represents the incident angle (unit: °), and the vertical axis represents the reflectance (unit:%). “Metallic coating_S-polarized light” represents data of S-polarized light (vibration component perpendicular to the incident surface) with respect to Example 1, and “Metallic coating_P-polarized light” represents P-polarized light with respect to Example 1 (parallel to the incident surface). “Metallic coating_average” represents the simple average of the S-polarized and P-polarized data for Example 1. “White coating_S-polarized light” represents S-polarized data for Comparative Example 1, “White coating_P-polarized” represents P-polarized data for Comparative Example 1, and “White coating_average” represents Comparative Example. 1 represents a simple average of S-polarized and P-polarized data for 1.

  As is clear from FIG. 4, when the wavelength of the incident light is 400 nm, the reflectance in Example 1 is significantly improved as compared with Comparative Example 1 regardless of the incident angle. As is clear from FIGS. 5 to 7, the same tendency as in the case where the wavelength of the incident light is 400 nm was also observed when the wavelength of the incident light was 500 nm, 600 nm, and 700 nm.

From the above, it was demonstrated that the flexible printed circuit board 1 can obtain a higher reflectance by providing the metallic coating layer 7 in the surface layer portion than when the white coating layer 13 is provided in the surface layer portion.
[Embodiment 2 of the Invention]

  FIG. 8 shows a second embodiment of the present invention. In FIG. 8, the dimensional ratio of each component is not necessarily accurate because it is illustrated with emphasis on ease of understanding.

  In the second embodiment, as shown in FIG. 8, a heat sink layer 12 having a predetermined thickness (for example, 150 μm) is laminated on the back surface of the substrate body 2 via a heat conductive adhesive layer 11. About another structure, it has the same structure as Embodiment 1 mentioned above. In addition, about the member same as Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  Therefore, the second embodiment has the same effects as the first embodiment described above.

In addition, in the second embodiment, the heat generated in the light-emitting diode 8 can be released through the heat conductive adhesive layer 11 and the heat sink layer 12, so that the heat dissipation of the flexible printed circuit board 1 can be improved. .
Embodiment 3 of the Invention

  FIG. 9 shows a third embodiment of the present invention. In FIG. 9, the dimensional ratio of each component is not necessarily accurate because it is illustrated with emphasis on ease of understanding.

  In the third embodiment, as shown in FIG. 9, the flexible print is performed so that the light emitted from the light emitting diode 8 is reflected on the surface of the metallic coating layer 7 and condensed in a specific direction (upward in FIG. 9). The substrate 1 is formed in a concave shape in such a manner that the metallic coating layer 7 is bent at a predetermined angle at four bent portions F1, F2, F3, and F4 with the inner surface 1a side, and the inner surface of the concave flexible printed substrate 1 is formed. A light emitting diode 8 is arranged on the 1a side. About another structure, it has the same structure as Embodiment 1 mentioned above. In addition, about the member same as Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  Therefore, the third embodiment has the same effects as the first embodiment described above.

In addition, in the third embodiment, the metallic coating layer 7 of the concave flexible printed board 1 can function as a reflector. Accordingly, the mounting position of the light-emitting diode 8 on the flexible printed circuit board 1 can be changed as shown in FIGS. Design flexibility is increased. Alternatively, by appropriately arranging a plurality of light emitting diodes 8 on the concave flexible printed circuit board 1, it is possible to complement the lack of illuminance in a complementary manner to make the entire screen brighter.
[Other Embodiments of the Invention]

  In the first embodiment described above, the flexible printed circuit board 1 (one-sided FPC) in which the conductor circuit 4 is formed only on the surface of the base material 3 has been described. However, the present invention can be similarly applied to the flexible printed circuit board 1 (double-sided FPC) in which the conductor circuits 4 are respectively formed on both the front and back surfaces of the base material 3. Furthermore, the present invention can be similarly applied to a flexible printed circuit board 1 (multilayer FPC) in which a plurality of conductor circuits 4 are laminated via an insulating layer and these conductor circuits 4 are connected by through holes.

  Moreover, Embodiment 1-3 mentioned above demonstrated the case where the metallic coating layer 7 by which the aluminum particle was added to the synthetic resin is employ | adopted. However, the metallic coating layer 7 has a configuration other than this (for example, a synthetic resin to which silver particles, palladium particles, nickel particles, chromium particles, titanium particles, copper particles, or alloy particles thereof are added). The metallic coating layer 7 can be substituted or used in combination.

  Moreover, in Embodiment 1-3 mentioned above, the case where the light emitting diode 8 was used as a light emitting element was demonstrated. However, as long as it is attached to the light emitting element attaching portion 2a of the substrate body 2, a light emitting element other than the light emitting diode 8 can be substituted or used in combination.

  Moreover, although Embodiment 1-3 mentioned above demonstrated the flexible printed circuit board 1 which has the base material 3 which consists of polyimide films, the material of the base material 3 is not necessarily restricted to a polyimide film.

  Moreover, although Embodiment 1-3 mentioned above demonstrated the flexible printed circuit board 1 which has the conductor circuit 4 which consists of copper foil, the material of the conductor circuit 4 is not necessarily restricted to copper foil.

  Moreover, although Embodiment 1-3 mentioned above demonstrated the flexible printed circuit board 1 which has the cover material 6 which consists of polyimide films, the material of the cover material 6 is not necessarily restricted to a polyimide film.

  Furthermore, in Embodiment 3 mentioned above, the case where the flexible printed circuit board 1 was formed in concave shape by bending the flexible printed circuit board 1 was demonstrated. However, the flexible printed circuit board 1 may be formed in a concave shape by curving the flexible printed circuit board 1 into a bow shape or a curved surface shape.

  The present invention is not limited to automotive lighting applications, and can be widely applied to general lighting applications, backlight illumination of display devices, and other applications.

DESCRIPTION OF SYMBOLS 1 ... Flexible printed circuit board 1a ...... Inner surface 2 ... Board body 2a ... Light emitting element attachment part 3 ... Base material 4 ... Conductor circuit 6 ... Cover material 7 ... Metallic coating layer 8 ... Light emitting diode (light emission) element)
9 …… Reflector 12 …… Heat sink layer 14 …… Lighting device

Claims (10)

A flexible printed circuit board having a substrate body including a base material, a conductor circuit formed on the surface of the base material, and a cover material laminated on the upper side of the conductor circuit so as to cover the conductor circuit,
A flexible printed circuit board, wherein a metallic coating layer having a thickness of 1 to 10 μm is laminated on a surface of the substrate body.   The flexible printed circuit board according to claim 1, wherein the metallic coating layer is obtained by adding aluminum particles to a synthetic resin.   The flexible printed circuit board according to claim 1, wherein the metallic coating layer is provided to avoid a light emitting element mounting portion of the substrate body.   The flexible printed circuit board according to any one of claims 1 to 3, wherein a heat sink layer is laminated on a back surface of the substrate body.   The flexible printed circuit board according to claim 4, wherein the heat sink layer is made of copper.   A lighting device, wherein a light emitting element is attached to the light emitting element attaching portion of the flexible printed circuit board according to claim 1.   The illumination device according to claim 6, wherein a reflector is installed on an optical axis of light emitted from the light emitting element.   The light emitted from the light emitting element is reflected on the surface of the metallic coating layer and condensed in a specific direction by bending the flexible printed circuit board. Or the illuminating device of 7.   The lighting device according to claim 8, wherein the flexible printed circuit board is formed in a concave shape with the metallic coating layer as an inner surface side, and the light emitting element is disposed on the inner surface side of the flexible printed circuit board.   The lighting device according to claim 6, wherein the light emitting element is a light emitting diode.