JP2019079980A - LED light source - Google Patents

Abstract

To improve the adhesion between a sealing member and a reflective film while securing the light resistance and permeability to ultraviolet light of the sealing member.SOLUTION: An LED light source includes a substrate, an LED chip mounted on the surface of the substrate, a reflective film provided on the surface of the substrate to reflect light emitted from the LED chip, and a sealing member that covers at least a part of the reflective film and seals the LED chip, and the reflective film includes a scaly first filler having a predetermined major axis, and a scaly second filler having a longer major axis than the first filler.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an LED light source.

  Conventionally, as an LED light source, for example, as shown in Patent Document 1, an LED chip, a substrate on which the LED chip is mounted, and a surface of the substrate are formed by applying a white pigment, and light emitted from the LED chip is There is one provided with a reflective film that reflects light and a sealing member that covers the LED chip and the reflective film.

  In addition to protecting the LED chip and the reflective film, the sealing member usually has a refractive index between the LED chip and the external (air) refractive index, and thus between the LED chip and the external (air) Plays a role in reducing the amount of light remaining in the LED chip by reducing the difference in refractive index. This improves the light extraction efficiency of the LED light source.

  However, if the material of the sealing member is excellent in light resistance and transparency to light of short wavelength such as ultraviolet light, generally, it does not contain a functional group which is easily chemically reacted, Since the sealing member and the reflective film are difficult to chemically bond, the adhesion between the two is low. On the other hand, in the case of a material excellent in adhesion to the reflective film, a functional group which is easily chemically reacted is generally contained, and the functional group itself or the sealing member is formed by light energy such as ultraviolet light. Since the chemical bond with the reflective film is broken, the light resistance and transparency to ultraviolet light are low.

WO 2014/103326

  Therefore, the present invention has been made to solve the above-mentioned problems, and the adhesion between the sealing member and the reflective film is ensured while securing the light resistance and the permeability to the light of short wavelength such as ultraviolet light of the sealing member. The main issue is to improve the quality.

  That is, the LED light source according to the present invention includes a substrate, an LED chip mounted on the surface of the substrate, a reflection film provided on the surface of the substrate to reflect light emitted from the LED chip, and the reflection And a sealing member for covering the LED chip while covering at least a part of the film, wherein the reflective film has a major diameter greater than the scaly first filler having a predetermined major diameter and the first filler. It is characterized by having a scaly second filler.

  Although the reflective film containing only the first filler with a short major axis has a large total area on the surface of the filler and is excellent in the light reflection characteristics, its surface roughness tends to be small, while only the second filler having a long major axis Although the total area of the surface of the filler is small and the reflection film including the layer has a small light reflection property, the surface roughness tends to be large. Therefore, as in the present invention, if the reflection film includes the first filler and the second filler having different long diameters, the surface roughness can be increased while maintaining the light reflection characteristics at a certain level or more. The adhesion between the reflective film and the sealing member can be improved by the anchor effect.

  As a result, even if a material having high light resistance and transparency to ultraviolet light is selected as the sealing member, that is, a material from which good adhesion with the reflective film can not be obtained, the sealing member and the reflective film can be used. The adhesion of these can be enhanced by the anchor effect. Then, if the adhesion between the sealing member and the reflective film is increased, the sealing member becomes difficult to peel off, and air is not caught between the reflective film or the LED chip and the sealing member, and the light is emitted from the LED chip Light extraction efficiency can be improved.

  In order to secure the adhesion between the sealing member and the reflective film, the surface roughness of the reflective film is preferably 10 μm or more.

On the other hand, when the surface roughness of the reflective film is increased (when the ratio of the second filler is increased), the reflectance of the reflective film may be reduced.
Therefore, in order to set the reflectance of the reflective film to a certain value or more, the volume ratio of the first filler to the second filler contained in the reflective film is preferably 10% to 40%.

  In order to exert the above-described effects remarkably, the LED chip preferably emits ultraviolet light.

  According to the present invention configured as described above, the adhesion between the sealing member and the reflective film is ensured while securing the light resistance and the permeability to the ultraviolet light of the sealing member and without reducing the reflectance of the reflective film. Can be improved. In addition, by covering the LED chip and the reflective film with a sealing member, the extraction efficiency of the light emitted from the LED chip can be improved.

The figure which shows typically the structure of the LED light source of this embodiment. The figure which shows typically the structure of the reflective film of the embodiment. The figure which shows typically the shape of the filler of the embodiment. The figure which shows the experimental result which evaluated the performance of the reflective film of the embodiment. The figure which shows the experimental result which evaluated the performance of the reflective film of the embodiment.

  Hereinafter, an embodiment of an LED light source according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the LED light source 100 according to this embodiment includes a substrate 10, an LED chip 20 mounted on the surface of the substrate 10, a sealing member 30 for sealing the LED chip 20, and the substrate 10. And a reflective film 40 provided on the surface.

  The substrate 10 is made of, for example, ceramic or resin, and a wiring conductor (not shown) formed of a metal pattern or the like for electrically connecting the LED chip 20 is formed on the surface.

The LED chip 20 is mounted on the surface of the substrate 10 via a bonding member 50 such as solder or gold bump, and emits, for example, ultraviolet light (including deep ultraviolet light) having a radiation peak at 200 nm to 400 nm. . An example of such an LED chip 20 is one having a radiation peak at 250 nm to 350 nm, and specifically one having a radiation peak at around 265 nm.
Moreover, although the aspect by which one LED chip 20 was mounted in the board | substrate 10 is shown in FIG. 1, the number of LED chips 20 may be suitably changed according to the objective and the application, etc. according to the objective.

  The sealing member 30 is for sealing the LED chip 20. Here, in order to efficiently extract the ultraviolet light from the LED chip 20 to the sealing member 30, the sealing member 30 is excellent in the transparency to ultraviolet light and to the ultraviolet light. It consists of transparent resin provided with light resistance. As a material of such a sealing member 30, a fluorine resin is mentioned, for example. This is because some fluorine-based resins have excellent light resistance and transparency, and such fluorine-based resins do not contain a functional group that is chemically reactive, and the reflective film 40 Although the adhesion to the reflective film 40 is low because it is difficult to chemically bond with it, the chemical bond with the functional group itself or the reflective film 40 is not broken by the light energy of the ultraviolet light, so that it has the above characteristics.

  Further, the sealing member 30 is, for example, a curved surface whose surface bulges in the light emission direction, and is disposed such that the optical axis of the sealing member 30 and the optical axis of the LED chip 20 are coaxial. ing.

  The reflective film 40 is provided on the surface of the substrate 10 to reflect the light emitted from the LED chip 20, and is formed, for example, by applying a ceramic paint on the surface of the substrate 10. The reflective film 40 is formed so as to surround the LED chip 20, and at least a portion near the LED chip 20 is covered by the sealing member 30 described above.

Therefore, as shown in FIG. 2, the reflective film 40 according to the present embodiment includes a scaly first filler 41 having a predetermined major diameter and a scaly second filler 42 having a major diameter larger than the first filler 41. Have.
In addition, as shown in FIG. 3, in the “scale-like shape”, the major axis is larger than the thickness (preferably, the major axis is twice or more of the thickness, more preferably, the major axis is five or more of the thickness ) Means a long shape, which can be observed using, for example, an electron microscope or the like.

  As shown in FIG. 3, the first filler 41 and the second filler 42 of the present embodiment have a layered structure in which thin films are stacked, and have a crystal structure in which only one crystal plane is a cleavage plane. Contains the provided material. Examples of such a substance include hexagonal boron nitride (h-BN), graphite, mica and the like, and the first filler 41 and the second filler 42 in the present embodiment are both hexagonal boron nitride (h- BN).

  As described above, if the first filler 41 or the second filler 42 is a substance having a crystal structure in which only one crystal face is a cleavage plane, the first filler 41 or the second filler 42 on the surface of the substrate 10 When the substrate 10 is subjected to thermal expansion or thermal contraction after applying the material including the above to form the reflective film 40, the crystal is easily slid from the cleavage plane, so that the reflective film 40 is not easily cracked or broken. can do.

As shown in FIG. 2, the reflective film 40 of the present embodiment is formed by applying on the surface of the substrate 10 a mixture of the first filler 41 and the second filler 42 described above mixed and dispersed in the binder 43. The Fresnel reflection occurs at the interface between the binder 43 and the first filler 41 and the second filler 42.
As the binder 43, the refractive index difference between the first filler 41 and the second filler 42 is large so as to increase the Fresnel reflection so as to improve the reflectivity of the reflective film 40, and the light emitted from the LED chip 20 The thing which does not absorb the wavelength of (here, the wavelength of an ultraviolet region) is preferable. In the present embodiment, a glass-based binder 43 obtained by dehydration polymerization of a silanol solution was used.

  The film thickness of the reflective film 40 is preferably 20 μm or more, more preferably 30 μm or more. The film thickness of the reflective film 40 is an important element that defines the amount of filler present in the film thickness direction, and the area of the interface between the binder 43 and the fillers 41 and 42 decreases as the film thickness decreases. The reflectance decreases. From that point of view, the film thickness is preferably 20 μm or more (more preferably 30 μm or more). On the other hand, since it is the surface layer from the surface to a certain depth that contributes to light reflection in the reflective film 40, no improvement in reflectance is seen when the film thickness exceeds a certain value, and the upper limit of the film thickness is particularly limited. It is not a thing.

  As described above, the first filler 41 and the second filler 42 have different major axes, and here, the average particle size (major axis) of the first filler 41 is, for example, 2 μm, and the average particle size (major axis) of the second filler 42 Is 8 μm, for example. Thus, in the present embodiment, the fillers 41 and 42 having different sizes are mixed in the binder 43. This is because if only the first filler 41 is used, the area of the interface between the binder 43 and the filler 41 is large and good reflection characteristics can be obtained, but the surface roughness of the reflective film 40 is small, and If only the second filler 42 is used, although the surface roughness of the reflective film 40 is increased, the area of the interface between the binder 43 and the filler 42 is small, and good reflection characteristics can not be obtained.

  Therefore, by mixing the fillers 41 and 42 of different sizes, it is possible to obtain a surface roughness suitable for obtaining an anchor effect while keeping the light reflection characteristics at a certain level or more, and the anchor effect causes the reflective film 40 to be obtained. The adhesion between the and the sealing member 30 is improved.

  Then, the experimental result which evaluated performance, such as adhesiveness with respect to the sealing member 30 of the reflecting film 40 mentioned above and the reflectance of the reflecting film 40, is demonstrated.

  First, a method of producing a sample used in the experiment will be described.

  First, the first filler 41 and the second filler 42 are mixed and dispersed in a silanol solution, respectively, to prepare a paint in which two types of fillers 41 and 42 are mixed at various volume ratios. Here, the paint in which the volume ratio of the first filler 41 to the second filler 42 is 100%, 75%, 50%, 25%, 0% was produced. The volume ratio is a value after the coating is cured, and the ratio of the filler to the entire coating after curing is about 50% by volume.

  Then, each paint is applied to a metal plate such as an aluminum plate, for example. At the time of application, the coating is applied to a metal plate while extending the coating with a squeegee or a roller, whereby the cleavage surfaces of the first filler 41 and the second filler 42 dispersed in the coating approximately correspond to the surface of the coating. Make it parallel.

  Thereafter, heat treatment is performed, for example, at 260 to 300 ° C. for several hours to dehydrate and polymerize the silanol solution, and solidify the first filler 41 and the second filler 42 in a dispersed state on the metal plate to form a metal plate. A sample on which a reflective film for evaluation having a thickness of about 50 μm is formed is produced.

  Next, the experimental result which evaluated the adhesiveness between the reflective film 40 and the sealing member 30 is demonstrated using the sample mentioned above. In the present embodiment, the adhesion between the reflective film 40 and the sealing member 30 was evaluated by a method called a cross cut method.

  In order to check the correlation between the surface roughness of the reflective film 40 and the adhesion, first, the surface roughness of the reflective film for evaluation was measured for each of the samples described above. Specifically, with respect to the evaluation reflective film formed on each sample, the maximum height of the surface in an area of about 80 μm was measured as the surface roughness.

  Next, a liquid sealing resin (the above-mentioned fluorine-based resin) is dropped onto the evaluation reflection film, and heat treatment is performed, for example, at 200 ° C. for 1 hour to cure the sealing resin. Form a sealing resin thin film.

  Then, incisions were made in the sealing resin thin film to form a grid of 25 squares at intervals of 1 mm, and a transparent adhesive tape was attached to these squares and peeled off to conduct a tape peeling test.

  The test results are shown in FIG. In FIG. 4, triangle marks indicate the number of masses of the sealing resin thin film peeled from the evaluation reflection film before peeling the transparent adhesive tape (that is, when the cut is made), and the square marks indicate the transparent The mass number of the sealing resin thin film peeled from the reflection film for evaluation after peeling off the adhesion tape is shown.

From this test result, it is understood that the number of squares of the sealing resin thin film peeled off at the boundary of 10 μm of the surface roughness of the reflection film for evaluation is largely changed.
That is, from the experimental results, in order to secure the adhesion between the reflective film 40 and the sealing member 30, the surface roughness of the reflective film 40 is preferably 10 μm or more, more preferably 11 μm or more. I understand.

  In addition, as a result of performing a thermal shock test for 30 minutes and 100 cycles at -40 ° C to 100 ° C for each of the samples described above, there is no change in the appearance, and evaluation is also performed between the metal plate and the reflective film for evaluation No peeling was observed between the reflective film and the sealing resin film.

By the way, when the surface roughness of the reflective film 40 is increased (when the ratio of the second filler 42 is increased), the reflectance may be reduced.
On the other hand, as a result of experiments conducted by the inventor of the present invention, it is possible to maintain the reflectance of the reflective film 40 at a high level without deteriorating the adhesion between the reflective film 40 and the sealing member 30. It was found that there was a mixing ratio with the second filler 42.
The experimental results will be described below.

  First, the surface roughness of the evaluation reflective film was measured for each of the samples described above. As the measurement method, as described above, the maximum height of the surface in the area of about 80 μm square was measured as the surface roughness.

  Next, the reflectance of the evaluation reflective film formed on each sample was measured. The reflectance here is a value obtained by measuring a combination of the specular reflection component and the diffuse reflection component of the ultraviolet light reflected by applying the ultraviolet light of 265 nm to the reflection film for evaluation.

The results of plotting these measurement results are shown in FIG. In FIG. 5, triangular marks indicate the results of measuring the reflectance of the evaluation reflective film, and square marks indicate the results of measuring the surface roughness of the evaluation reflective film.
From this experimental result, in order to maintain the reflectance of the reflective film 40 high and to make the surface roughness such that the adhesion between the reflective film 40 and the sealing member 30 is not impaired, ie, 10 μm or more, It is understood that the volume ratio of the first filler 41 to the second filler 42 is preferably 10% or more and 40% or less, and more preferably 25%.

According to the LED light source 100 of the present embodiment configured as described above, since the reflective film 40 includes the scaly first fillers 41 and scaly second fillers 42 having different major axes, the reflective film 40 is formed. The surface of the film can be made rough enough to bring the reflective film 40 and the sealing member 30 into close contact with each other, and the adhesion between the two can be improved by the anchor effect.
Thus, as in the present embodiment, even if the sealing member 30 is formed of a fluorine-based resin that does not have a functional group that easily reacts with ultraviolet light, such as an OH group, which has high light resistance and transparency. The adhesion between the sealing member 30 and the reflective film 40 can be improved, and if the adhesion is increased and the sealing member 30 is difficult to peel off, the reflective film 40 or the LED chip 20 and the sealing member 30 can be used. Thus, air does not get caught between them, and the extraction efficiency of the ultraviolet light emitted from the LED chip 20 can be improved.

  Furthermore, as shown in FIG. 5, the reflectance of the reflective film 40 is set by setting the volume ratio of the first filler 41 to the second filler 42 contained in the reflective film 40 to 10% or more and 40% or less, preferably 25%. The adhesion between the reflective film 40 and the sealing member 30 can be secured while maintaining the

  The present invention is not limited to the above embodiment.

  For example, although the case where the average particle diameter (long diameter) of the first filler 41 is 2 μm and the average particle diameter (long diameter) of the second filler 42 is 8 μm has been described in the embodiment, the first filler 41 or the first As the 2 filler 42, one having an average particle diameter (long diameter) of, for example, 1 μm or less or one having several tens of μm may be used.

  Moreover, although the 1st filler 41 and the 2nd filler 42 of the said embodiment had a layered structure which piled up the thin film, they may not have a layered structure. Furthermore, the first filler 41 and the second filler 42 may be a mixture of a plurality of substances. Moreover, the reflective film 40 may have three or more types of fillers.

  Although the sealing member 30 is made of a fluorine-based resin in the above embodiment, it may be made of, for example, silicon resin, glass, or the like.

  The LED chip 20 emits ultraviolet light in the above embodiment, but may emit visible light of short wavelength, for example.

  In addition, the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the scope of the invention.

100 ... LED light source 10 ... Substrate 20 ... LED chip 30 ... Sealing member 40 ... Reflective film 41 ... First filler 42 ... Second filler

Claims (4)

A substrate,
An LED chip mounted on the surface of the substrate;
A reflective film provided on the surface of the substrate to reflect light emitted from the LED chip;
A sealing member that covers at least a part of the reflective film and seals the LED chip;
An LED light source, comprising: a scaly first filler having a predetermined major axis; and a scaly second filler having a major axis greater than the first filler.   The LED light source according to claim 1, wherein the surface roughness of the reflective film is 10 μm or more.   The LED light source according to claim 1 or 2, wherein a volume ratio of the first filler to the second filler contained in the reflective film is 10% or more and 40% or less.   The LED light source according to any one of claims 1 to 3, wherein the LED chip emits ultraviolet light.