JP6324683B2 - Direct type light source device - Google Patents

Description

  The present disclosure relates to a direct light source device suitable for a surface light source.

  Backlight systems used for liquid crystal display devices include a direct system and an edge light system. In recent years, as these backlights, LEDs (Light Emitting Diodes) are frequently used as light sources. When an LED is used as the light source, for example, there is a method of obtaining white light by mixing blue light and light emitted by the phosphor by sealing the periphery of the blue LED with a resin containing the phosphor. As another method, there is a method of obtaining white light by disposing a phosphor layer as a separate body from the light source (see Patent Document 1).

JP 2011-82590 A

  In these light source devices, it is desired to increase the luminance efficiency. In particular, in a direct type light source device, optical sheets such as DBEF (Dual Brightness Enhancement Film) are disposed opposite to the light source substrate, and return light from the optical sheets is reflected by the light source substrate and used as recycled light. When the brightness is to be improved, the use efficiency of the recycled light affects the brightness efficiency of the entire apparatus. In that case, the reflection efficiency at the light source substrate affects the utilization efficiency of the recycled light.

  An object of the present disclosure is to provide a direct type light source device capable of improving luminance efficiency.

Direct type light source apparatus according to the present disclosure, a substrate, a disposed on the substrate the resist layer, a plurality of light sources each consisting of an LED package mounted on the substrate via the external electrodes, disposed to face the plurality of light sources A wavelength conversion member and a through hole in which a plurality of light sources are arranged are formed, arranged on the substrate via a resist layer, and light emitted from the plurality of light sources is incident on the wavelength conversion member and then to the substrate side. And a reflection member that reflects the return light toward the wavelength conversion member . Then, the ratio of the area occupied by the reflecting member on the outermost surface of the substrate is set to 92% or more and 95% or less, and other regions are displayed around the light source through the plurality of light sources arranged in the punched holes and the punched holes. The exposed resist layer occupies this area.
In addition, the area occupied by the resist layer exposed through the hole in the outermost surface of the substrate is larger than the area occupied by the surface of the LED package, and the surface of the reflective member, the surface of the LED package, and the surface of the resist layer The reflectance for the return light is increased.

  In the direct type light source device according to the present disclosure, since the reflection member is provided on the substrate, when the light from the light source returns to the substrate side, the returned light can be recycled. And since the ratio of the area which a reflection member occupies on the outermost surface of a board | substrate is optimized, the utilization efficiency of the recycle light improves.

According to the direct light source device of the present disclosure, since the ratio of the area occupied by the reflecting member on the outermost surface of the substrate is optimized, the utilization efficiency of recycled light is improved, and the luminance efficiency of the entire device is improved. be able to.
Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

It is sectional drawing which shows the example of 1 structure of the light source device which concerns on one embodiment of this indication. It is a top view which shows an example of in-plane arrangement | positioning of the light source in the light source device which concerns on one Embodiment. It is sectional drawing which shows the light source in the light source device which concerns on one embodiment, and one structural example of the circumference | surroundings. It is sectional drawing which shows one structural example of the wavelength conversion sheet | seat in the light source device which concerns on one Embodiment. It is sectional drawing which shows an example of the advancing state of the light inside the light source device which concerns on one Embodiment. It is explanatory drawing which shows the 1st example of the advancing state of the light from the light source which injects into a wavelength conversion sheet. It is explanatory drawing which shows the 2nd example of the advancing state of the light from the light source which injects into a wavelength conversion sheet. It is sectional drawing which shows the advancing state of the light which injects into a wavelength conversion sheet | seat from a perpendicular direction. It is sectional drawing which shows the advancing state of the light which injects into a wavelength conversion sheet from the diagonal direction. It is sectional drawing which shows the effect | action of the diffusion member in the light source device which concerns on one embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. Configuration 2. Operation 2.1 Operation of the entire light source device 2.2 Operation of the diffusion member 2.3 Operation of downsizing the light source (numerical example)
3. Effect 4. Other embodiments

[1. Constitution]
FIG. 1 illustrates a configuration example of a light source device according to an embodiment of the present disclosure. FIG. 2 shows an example of the in-plane arrangement of the light source 2 in this light source device. FIG. 3 shows a configuration example of the light source 2 and its surroundings. FIG. 4 shows a configuration example of the wavelength conversion sheet 3 in this light source device. This light source device is suitable as a surface light source, and is used, for example, as a direct-type backlight.

  The light source device includes a light source substrate 1, a plurality of light sources 2, a wavelength conversion sheet 3 as a wavelength conversion member, a diffusion member 4, an optical sheet 5, a reflection sheet 6 as a reflection member, and a resist layer 7. A rear housing (back chassis) 101 and an intermediate housing (middle chassis) 102 are provided.

  The light source substrate 1 is disposed on the bottom surface of the rear housing 101. The rear housing 101 has a shape in which a peripheral portion is bent upward, and an intermediate housing 102 is attached to an end portion of the peripheral portion. The peripheral part of the back casing 101 is formed with a flat part on the inner side of the attachment part of the intermediate casing 102, and the peripheral part of the diffusion member 4 is supported by the flat part. A wavelength conversion sheet 3 and an optical sheet 5 are disposed on the light emission surface (front surface) side of the diffusing member 4. When this light source device is applied to a display device, a display panel may be disposed on the light emission surface (front surface) side of the optical sheet 5. In that case, the peripheral portion of the display panel may be supported by the intermediate housing 102.

  The wavelength conversion sheet 3 is disposed so as to face the plurality of light sources 2. The diffusing member 4 is disposed between the wavelength conversion sheet 3 and the plurality of light sources 2. The diffusing member 4 is for making the angular distribution of incident light uniform. The diffusion member 4 may be one diffusion plate or one diffusion sheet, or may be two or more diffusion plates or two or more diffusion sheets.

  The optical sheet 5 is disposed on the light emission surface (front surface) side of the wavelength conversion sheet 3. The optical sheet 5 is composed of, for example, a sheet or film for improving luminance. The optical sheet 5 may include, for example, a prism sheet. The optical sheet 5 may also include a reflective polarizing film such as DBEF (Dual Brightness Enhancement Film).

  A wiring pattern (not shown) is formed on the light source substrate 1 so that independent light emission control can be performed for each of one or more light sources 2. Thereby, local light emission control (local dimming) of the plurality of light sources 2 is possible. As the light source substrate 1, what printed the wiring pattern on resin films, such as PET (polyethylene terephthalate), a fluorine, and PEN (polyethylene naphthalate), can be used. In addition, printed wiring pattern made of light-reflective material on the insulating resin layer of a metal base substrate such as aluminum (Al), which has an insulating resin layer such as polyimide or epoxy on the surface. It may be used. Moreover, it is good also as what printed the wiring pattern of the material which has light reflectivity on the film base material which consists of glass containing resin, such as FR4 (glass epoxy resin) and CEM3 (glass composite resin). Examples of the material having light reflectivity include Al, silver (Ag), and alloys thereof.

  On the light source substrate 1, a resist layer 7 and a reflection sheet 6 are arranged in order. The reflection sheet 6 is arranged in an in-plane area different from the in-plane area where the plurality of light sources 2 are arranged on the light source substrate 1.

The resist layer 7 is a white resist layer having a relatively high reflectance with respect to the light from the light source 2 and the light whose wavelength is converted by the wavelength conversion sheet 3. Examples of the white resist include inorganic materials such as titanium oxide (TiO ₂ ) fine particles and barium sulfate (BaSO ₄ ) fine particles, and organic materials such as porous acrylic resin fine particles having numerous holes for light scattering and polycarbonate resin fine particles. Is mentioned.

  The reflection sheet 6 has a high reflectance with respect to the light from the light source 2 and the light subjected to wavelength conversion by the wavelength conversion sheet 3. The reflection sheet 6 may contain Ag as a material having a high reflectance. As shown in FIGS. 2 and 3, the reflection sheet 6 is formed with a hole 61 for placing the light source 2.

In the in-plane region where the hole 61 is formed, the resist layer 7 is exposed around the light source 2. Therefore, on the outermost surface of the light source substrate 1, the in-plane region other than the punch hole 61 is the reflection sheet 6, and the in-plane region where the punch hole 61 is formed is mainly the light source 2 and the resist layer 7.
Here, in order to improve the utilization efficiency of recycled light (reflection efficiency of the light source substrate 1), the ratio of the area occupied by the light source 2 and the resist layer 7 on the outermost surface of the light source substrate 1 is reduced, and the reflection sheet 6 occupies. It is preferable to increase the area ratio. Specifically, as shown in numerical examples described later, it is preferable that the ratio of the area occupied by the reflection sheet 6 is 92% or more and 95% or less.

  The light source 2 is two-dimensionally arranged on the light source substrate 1 as shown in FIG. As shown in FIG. 3, the light source 2 includes a light emitting element 21, a package 22, and a sealing material 23. The package 22 has a concave housing portion, and the light emitting element 21 is disposed on the bottom surface of the concave housing portion. The concave accommodating portion is filled with a sealing material 23. The light emitting element 21 is, for example, a point light source, and specifically includes an LED. The package 22 is mounted on the light source substrate 1 by solder or the like via external electrodes made of a lead frame (not shown). It is preferable that the surface of the concave housing portion in the package 22 has a high reflectance with respect to the light from the light emitting element 21. For example, the surface of the concave accommodating portion may contain Ag as a material having a high reflectance. The sealing material 23 is made of a transparent resin such as silicone or acrylic.

  The wavelength conversion sheet 3 includes a wavelength conversion substance 31 as shown in FIG. The wavelength converting material 31 includes, for example, a fluorescent material (fluorescent material) such as a fluorescent pigment or a fluorescent dye, or quantum dots. The wavelength converting material 31 is excited by light from the light source 2 and is emitted from the light source 2 by a principle such as fluorescence emission. The light is converted into light having a wavelength different from the original wavelength and emitted.

  The light source 2 is, for example, a blue light source (for example, a wavelength of 440 nm to 460 nm), and the wavelength conversion material 31 absorbs the blue light of the light source 2 and a part thereof is red light (for example, a wavelength of 620 nm to 750 nm) or green light. (For example, wavelength 495 nm to 570 nm). In this case, when the light from the light source 2 passes through the wavelength conversion material 31, the red, green, and blue lights are combined to generate white light. The wavelength converting substance 31 may also absorb blue light and convert part of it into yellow light. In this case, when the light from the light source 2 passes through the wavelength conversion material 31, the yellow and blue lights are combined to generate white light.

  The wavelength conversion substance 31 preferably includes quantum dots. Quantum dots are particles having a major axis of about 1 nm to 100 nm and have discrete energy levels. Since the energy state of the quantum dot depends on its size, the emission wavelength can be freely selected by changing the size. The light emitted from the quantum dots has a narrow spectral width. The color gamut is expanded by combining such steep peak light. Therefore, the color gamut can be easily expanded by using quantum dots for the wavelength conversion material 31. Furthermore, the quantum dot has high responsiveness, and the light from the light source 2 can be used efficiently. In addition, quantum dots are highly stable. The quantum dot is, for example, a compound of a group 12 element and a group 16 element, a compound of a group 13 element and a group 16 element, or a compound of a group 14 element and a group 16 element. , PbS, PbSe or CdHgTe.

[2. Action]
(2.1 Operation of the entire light source device)
FIG. 5 shows an example of the state of light traveling inside the light source device. In this light source device, a part of the light LB (for example, blue light) emitted from the light source 2 becomes light LY that has been wavelength-converted (emitted) by the wavelength conversion substance 31 (FIG. 4) in the wavelength conversion sheet 3. The wavelength-converted light LY is, for example, red light, green light, or yellow light. The wavelength-converted light LY is averagely reflected and emitted from the wavelength conversion sheet 3 in all directions. Of the light LB emitted from the light source 2, the light LB <b> 3 that has not been absorbed by the wavelength conversion substance 31 is also emitted from the wavelength conversion sheet 3 evenly in all directions on average. Of the light LB emitted from the light source 2, the light LB 2 that has not hit the wavelength conversion substance 31 is emitted from the wavelength conversion sheet 3 as it is. Of the light LB2 and LB3 that have not been wavelength-converted, the light that travels forward and the light that travels forward of the wavelength-converted light LY are combined to generate white light, which is emitted forward (outside the light source device). The

  Further, part of the light LB2, LB3 that has not undergone wavelength conversion becomes light (downward light LB1) that travels backward (substrate 1 side) from the wavelength conversion sheet 3. Further, of the light LB2 and LB3 that have not been wavelength-converted, part of the light traveling forward becomes regressed light by the optical sheet 5 such as DBEF, and becomes downward light LB1. The downward light LB1 is reflected by the surface of the light source substrate 1 (mainly the reflection sheet 6) and again travels toward the wavelength conversion sheet 3, and a part of the light is converted. Similarly, the downward light LY1 of the wavelength-converted light LY is reflected by the surface of the light source substrate 1 and becomes forward light. As described above, the downward light beams LB1 and LY1 are reflected by the surface of the light source substrate 1 and become recycled light for generating white light. Recycling of the downward light beams LB1 and LY1 may be performed, for example, four or five times. Therefore, the final luminance of the white light emitted from the light source device is composed of the recycled light.

(2.2 Action of diffusion member 4)
The operation of the diffusing member 4 will be described with reference to FIGS. FIG. 6 shows a first example of the traveling state of light from the light source 2 incident on the wavelength conversion sheet 3. FIG. 7 shows a second example of the traveling state of light from the light source 2 incident on the wavelength conversion sheet 3. 6 and 7 show a configuration in which the diffusing member 4 is omitted. FIG. 8 shows a traveling state of light incident on the wavelength conversion sheet 3 from the vertical direction. FIG. 9 shows a traveling state of light incident on the wavelength conversion sheet 3 from an oblique direction. FIG. 10 shows the operation of the diffusing member 4.

  FIG. 6 shows a case where the arrangement interval D of the plurality of light sources 2 is optimized at an appropriate interval and the distance H between the plurality of light sources 2 and the wavelength conversion sheet 3 is optimized to an appropriate value. ing. In this case, in the wavelength conversion sheet 3, for example, in the region 81 immediately above the light source 2, the vertical component L <b> 1 and the oblique component L <b> 2 of light from the light source 2 are evenly mixed to generate white light. In the case where the diffusing member 4 is not arranged, in order to make the vertical component L1 and the oblique component L2 of the light from the light source 2 uniformly mix, it is necessary to reduce the arrangement interval D of the plurality of light sources 2 to some extent. is there. Further, the distance H between the plurality of light sources 2 and the wavelength conversion sheet 3 needs to be increased to some extent.

  On the other hand, FIG. 7 shows a case where the arrangement interval D of the plurality of light sources 2 is larger and the distance H between the plurality of light sources 2 and the wavelength conversion sheet 3 is shorter than the state of FIG. In this case, for example, in the region 82 immediately above the light source 2, the ratio of the vertical component L1 of the light from the light source 2 increases. Further, for example, in the region 83 off from directly above the light source 2, the ratio of the oblique component L2 of the light from the light source 2 increases. Here, as shown in FIGS. 8 and 9, there is an optical path difference between the optical path through which the vertical component L1 passes and the optical path through which the oblique component L2 passes inside the wavelength conversion sheet 3, and the light is converted into the wavelength converting substance 31. There is a difference in the percentage of hits. For this reason, a difference arises in the ratio of the light wavelength-converted by the wavelength conversion substance 31. Since the optical path through which the oblique component L2 passes is longer than the optical path through which the vertical component L1 passes, the ratio of light that is wavelength-converted by the wavelength conversion material 31 increases. As a result, in the region 82 immediately above the light source 2 and the region 83 outside the light source 2, color unevenness having a chromaticity difference occurs.

  By arranging the diffusing member 4 on the light incident side of the wavelength conversion sheet 3, it is possible to suppress the occurrence of the color unevenness described above. For example, as shown in FIG. 10, when the oblique component L2 is incident on the diffusing member 4, the light is diffused and the angular distribution of the light is made uniform to some extent. Thereby, the ratio of the oblique component L2 is reduced, and the occurrence of color unevenness is suppressed.

(2.3 Effects of downsizing the light source (numerical example))
When the arrangement interval D of the plurality of light sources 2 is too wide, in the wavelength conversion sheet 3, there is a difference in luminance between the region directly above the light source 2 and the region between the adjacent light sources 2, and uneven luminance occurs. Hereinafter, such luminance unevenness is referred to as “grain unevenness”. In order to eliminate this grain unevenness, it is necessary to increase the number of the light sources 2 to some extent. On the other hand, if the number of light sources 2 is increased too much, the number of punch holes 61 (see FIGS. 2 and 3) provided in the reflection sheet 6 increases accordingly, so that the area of the reflection sheet 6 is reduced and recycled. Light utilization efficiency decreases. For this reason, a decrease in luminance occurs as a whole. To increase the number of light sources 2 and not reduce the utilization efficiency of recycled light (the reflection efficiency of the light source substrate 1), it is conceivable to reduce the size of the light source 2 itself. However, reducing the size of the light source 2 itself leads to reducing the size of the light emitting element 21. If the size of the light emitting element 21 is reduced, the value of current flowing through the light emitting element 21 in order to obtain a predetermined luminance increases, and the light emitting element 21 is used in a region where the light emitting efficiency is poor. Therefore, it is required to reduce the size of the light source 2 within a range where the luminous efficiency is not lowered.

  [Table 1] and [Table 2] show the results of concrete simulation of the difference in luminance efficiency when the size of the light source 2 is changed.

(Calculation condition)

The package size (PKG size) of the LED as the light source 2 was calculated as follows.
Normal size: 3.2mm x 2.85mm
Small size 1 (small size 1): 4mm x 2mm
Small size 2 (small size 2): 3mm x 1.4mm

The overall size of the light source device was 55 inches, and the number of light sources 2 necessary to eliminate the unevenness of the grains was calculated as follows.
Number of light sources 2 (LEDs): 1360

  As a configuration common to each size, in addition to the diffusing member 4, two crossed prism sheets and DBEF are arranged as the optical sheet 5. The optical distance between the light source 2 and the wavelength conversion sheet 3 is 16 mm.

The following numerical values were used as other conditions.
Reflectivity of reflection sheet 6: 98%
Reflectivity of resist layer 7: 70%
LED package reflectance: 90%

  As described above, the reflection sheet 6 is formed with a punched hole 61 for placing the light source 2. Therefore, the exposed surface of the resist layer 7 exists around the light source 2 in the region of the punched hole 61. [Table 1] shows the results of calculating the respective area ratios occupied by the LED package, the exposed surface of the resist layer 7 and the reflection sheet 6 on the outermost surface of the light source substrate 1 for each size.

  [Table 2] shows the total reflectance of the entire region of the outermost surface on the light source substrate 1 as a total (TTL) reflectance. Further, as described above, light is recycled between the light source substrate 1 and the wavelength conversion sheet 3 and the optical sheet 5 by reflection on the light source substrate 1. The inventor of the present application has confirmed through experiments that the luminance as the light source device is established by recycling four times. That is, since there are four reflections on the light source substrate 1, the fourth power of the TTL reflectance is calculated. This fourth power TTL reflectance value corresponds to the final luminance. [Table 2] shows the result of comparing and calculating the fourth power TTL reflectance for each size of the LED packages in order to compare the final luminance difference.

  From the simulation results, it can be seen that the luminance is improved when a small-sized LED package is used. When a small-sized LED package is used, as shown in [Table 1], the ratio of the area occupied by the reflection sheet 6 to the entire area of the light source substrate 1 is 92% or more and 95% or less. In this case, the area of the reflective sheet 6 can be increased and the use efficiency of the recycled light can be increased as compared with the case where a normal size LED package is used. For this reason, the brightness | luminance as the whole light source device can be improved.

[3. effect]
As described above, according to the present embodiment, since the ratio of the area occupied by the reflection sheet 6 on the outermost surface of the light source substrate 1 is optimized, the utilization efficiency of recycled light is improved, and the entire apparatus is improved. Luminance efficiency can be improved.
Note that the effects described in the present specification are merely examples and are not limited, and other effects may be obtained.

<4. Other Embodiments>
The technology according to the present disclosure is not limited to the description of the above embodiment, and various modifications can be made.

For example, the present technology can take the following configurations.
(1)
A substrate,
A plurality of light sources disposed on the substrate;
A wavelength conversion member disposed opposite to the plurality of light sources;
A reflective member disposed on a region different from the plurality of light sources on the substrate,
The direct light source device in which the ratio of the area of the outermost surface of the substrate occupied by the reflecting member is 92% or more and 95% or less.
(2)
The said light source contains LED as a light emitting element. The direct type light source device as described in said (1).
(3)
The light source emits blue light,
The said wavelength conversion member is a direct type light source device as described in said (1) or (2) which converts a part of blue light emitted from the said light source into red light and green light.
(4)
The light source emits blue light,
The said wavelength conversion member is a direct type light source device as described in said (1) or (2) which converts a part of blue light emitted from the said light source into yellow light.
(5)
The direct light source device according to any one of (1) to (4), wherein the plurality of light sources are two-dimensionally arranged on the substrate.

  DESCRIPTION OF SYMBOLS 1 ... Light source substrate, 2 ... Light source, 3 ... Wavelength conversion sheet, 4 ... Diffusing member, 5 ... Optical sheet, 6 ... Reflective sheet, 7 ... Resist layer, 21 ... Light emitting element, 22 ... Package, 23 ... Sealing material, DESCRIPTION OF SYMBOLS 31 ... Wavelength converting substance, 61 ... Open hole, 81 ... Area | region, 82 ... Area | region, 83 ... area | region, 101 ... Back housing | casing (back chassis), 102 ... Middle housing | casing (middle chassis), L1 ... Vertical component, L2 ... Diagonal component, LB ... light, LB1 ... downward light, LB2 ... light, LY ... wavelength converted light, LY1 ... downward light, D ... arrangement interval, H ... distance.

Claims (4)

A substrate,
A resist layer disposed on the substrate;
A plurality of light sources each consisting of an LED package mounted on the substrate via external electrodes;
A wavelength conversion member disposed opposite to the plurality of light sources;
A punch hole is formed in which the plurality of light sources are disposed, and is disposed on the substrate through the resist layer. After light emitted from the plurality of light sources is incident on the wavelength conversion member, the substrate is moved to the substrate side. A reflective member that reflects the return light directed to the wavelength conversion member ,
In the outermost surface of the substrate, the ratio of the area occupied by the reflecting member is 92% or more and 95% or less, and the other regions are formed through the plurality of light sources arranged in the punched holes and the punched holes. The resist layer exposed around the light source occupies ,
In the outermost surface of the substrate, the area occupied by the resist layer exposed through the hole is larger than the area occupied by the surface of the LED package,
The direct type light source device in which the reflectance with respect to the return light increases in the order of the surface of the reflecting member, the surface of the LED package, and the surface of the resist layer . The light source emits blue light,
The direct type light source device according to claim 1 , wherein the wavelength conversion member converts a part of blue light emitted from the light source into red light and green light. The light source emits blue light,
The direct type light source device according to claim 1 , wherein the wavelength conversion member converts part of blue light emitted from the light source into yellow light. The direct light source device according to any one of claims 1 to 3 , wherein the plurality of light sources are two-dimensionally arranged on the substrate.

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