Direct-type backlight device and display device having the same

Abstract

A direct-type backlight device and a display device having the backlight device are disclosed. According to one embodiment, the direct-type backlight device includes a lower frame, a reflective sheet disposed on the bottom of the lower frame, and a plurality of light-emitting diode (LED) strips disposed on the upper surface of the reflective sheet. Each of the plurality of LED strips includes a strip-shaped printed circuit board disposed on the upper surface of the reflective sheet, a plurality of LEDs disposed on the upper surface of the printed circuit board, and a reflective component disposed on the upper surface of the printed circuit board. The reflectivity of the reflective component is at least 90% of the reflectivity of the reflective sheet.

Description

Technical Field

[0001] The present disclosure relates to a display device, and in particular, to a direct-type backlight device and a display device having the direct-type backlight device. Background Art

[0002] Liquid crystal display devices, which currently occupy the largest share in the display market, use a liquid crystal panel that cannot emit light by itself, and use a backlight device as the light source of its liquid crystal display device.

[0003] When the backlight device irradiates light to the liquid crystal panel, the liquid crystal panel may display an image.

[0004] According to the arrangement structure of the light source, such backlight devices can generally be divided into edge-type backlight devices and direct-type backlight devices.

[0005] The structure of the edge-type backlight device is that one light source is arranged on one side of the light guide plate or two light sources are arranged on both sides of the light guide plate. A reflective sheet is arranged under the light guide plate to reflect the light emitted from the bottom surface of the light guide plate to the liquid crystal panel. A diffusion plate can be arranged on the upper side of the light guide plate to diffuse the light emitted from the top surface of the light guide plate.

[0006] On the other hand, the direct-type backlight device has a structure in which a plurality of light sources are distributed under a diffusion plate.

[0007] There is a problem in the related art that productivity of a direct-type backlight device and a display device including the same decreases as the size of the display device increases. Summary of the invention

[0008] Provided are a direct-type backlight device capable of improving productivity and a display apparatus having the backlight device.

[0009] According to one aspect of the present disclosure, a direct-type backlight device is provided, comprising: a lower frame, a reflective sheet arranged on the bottom of the lower frame; and a plurality of light emitting diode (LED) strips arranged on the upper surface of the reflective sheet, wherein each of the plurality of LED strips may include a strip-shaped printed circuit board arranged on the upper surface of the reflective sheet; a plurality of LEDs arranged on the upper surface of the printed circuit board; and a reflective component arranged on the upper surface of the printed circuit board, the reflectivity of the reflective component may be at least 90% of the reflectivity of the reflective sheet.

[0010] The reflective member may include a photo solder resist (PSR) layer having high reflectivity.

[0011] According to one aspect of the present disclosure, a display device is provided, comprising: a liquid crystal panel; a diffusion plate arranged below the liquid crystal panel; a plurality of light emitting diode (LED) strips arranged below the diffusion plate; a reflective sheet arranged above or below the plurality of LED strips; and a lower frame arranged above or below the reflective sheet and configured to support the reflective sheet, wherein each of the plurality of LED strips may include a strip-shaped printed circuit board arranged above the reflective sheet; a plurality of LEDs arranged on the upper surface of the printed circuit board; and a reflective component arranged on the upper surface of the printed circuit board, wherein a reflectivity of the reflective component may be at least 90% of a reflectivity of the reflective sheet.

[0012] According to one aspect of an embodiment of the present disclosure, a method for manufacturing a direct-type backlight device is provided, the method comprising: setting a reflective sheet on the upper surface of the bottom of a lower frame; after the reflective sheet is set on the lower frame, setting a plurality of light emitting diode (LED) strips on the upper surface of the reflective sheet, each of the plurality of LED strips comprising a printed circuit board, a plurality of LEDs and a reflective component; and providing a diffusion plate above the plurality of LED strips. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] These and / or other aspects and advantages of certain embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a cross-sectional view schematically showing a general direct-type backlight device;

[0015] Figure 2 is a cross-sectional view schematically showing a display device according to an embodiment;

[0016] Figure 3 is a cross-sectional view schematically showing a direct-type backlight device according to an embodiment;

[0017] Figure 4 It shows Figure 3 A plan view of a direct-lit backlight device;

[0018] Figure 5 is a cross-sectional view schematically showing a direct-type backlight device according to an embodiment;

[0019] Figure 6 is a partial cross-sectional view showing an LED bar used in a direct-type backlight device according to an embodiment;

[0020] Figure 7 is a partial cross-sectional view showing an LED bar used in a direct-type backlight device according to an embodiment;

[0021] Figure 8is a partial cross-sectional view showing an LED bar used in a direct-type backlight device according to an embodiment;

[0022] Fig. 9 It shows the settings in Figure 8 A plan view of a reflector cover on an LED strip; and

[0023] Fig.10 is a flow chart showing a method of manufacturing a direct type backlight device according to an embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, some embodiments of a direct-type backlight device and a display device having the backlight device according to the present disclosure will be described in detail with reference to the accompanying drawings according to the present disclosure.

[0025] Various embodiments will be described below with reference to the accompanying drawings. However, it should be understood that the technology mentioned in the present disclosure is not limited to specific embodiments, but includes various modifications, equivalents and / or substitutions according to the embodiments of the present disclosure. The matters defined herein, such as specific structures and elements thereof, are provided to assist in a comprehensive understanding of this description. Therefore, it is apparent that the embodiments can be performed without those defined matters. In addition, in order to provide a clear and concise description of the embodiments, some well-known functions or structures are omitted. In addition, in order to assist in a comprehensive understanding, the sizes of the elements in the accompanying drawings may be increased or decreased arbitrarily.

[0026] The terms "first", "second", etc. may be used to describe different components, but the components are not limited by these terms. These terms may only be used to distinguish one component from other components. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component without departing from the scope of the disclosure.

[0027] Unless otherwise defined, the terms used in the embodiments of the present disclosure may be interpreted as terms well known to those skilled in the art.

[0028] In addition, the terms "front end", "rear end", "upper side", "lower side", "upper end", "lower end" and the like used in the present disclosure are defined with reference to the drawings. However, the shape and position of each member are not limited by the terms.

[0029] In the following description, when an element is referred to as being “on the upper side,” “over,” “on,” or “connected” or “coupled” to another element, it may be located on the “upper side,” “over,” “on,” or “connected” or “coupled” to the other element in contact with the other element, or it may be located on the “upper side,” “over,” “on,” or “connected” or “coupled” to the other element without contact with the other element (i.e., one or more intermediate elements may be present).

[0030] Figure 1 is a cross-sectional view schematically showing a general direct-type backlight device.

[0031] refer to Figure 1 A general direct-type backlight device 100 includes a lower frame 110, a light emitting diode (LED) bar 120, a reflective sheet 130 and a diffusion plate 140. Figure 1 Only one LED bar 120 is shown in FIG. 1 , but the general direct-lit backlight device 100 includes a plurality of LED bars 120 .

[0032] A plurality of LED bars 120 are arranged and spaced apart at predetermined intervals on the upper surface of the lower frame 110 , wherein each LED bar 120 includes a bar-shaped printed circuit board 121 and a plurality of LEDs 122 disposed on the printed circuit board 121 .

[0033] A reflective sheet 130 having a size corresponding to that of the diffuser plate 140 is disposed on the plurality of LED bars 120. A plurality of through holes 131 are formed in the reflective sheet 130 so that the plurality of LEDs 122 disposed on the plurality of LED bars 120 can be exposed through the plurality of through holes 131. Accordingly, when the reflective sheet 130 is disposed on the plurality of LED bars 120 on the lower frame 110, the plurality of LEDs 122 protrude from the reflective sheet 130, and the printed circuit board 121 is located under the reflective sheet 130. In other words, the printed circuit board 121 in the LED bar 120 is covered by the reflective sheet 130.

[0034] The diffusion plate 140 is disposed above the reflection sheet 130 and the plurality of LEDs 122 .

[0035] A liquid crystal panel is disposed above the diffusion plate 140, and light emitted from the plurality of LEDs 122 is irradiated toward the liquid crystal panel through the diffusion plate 140. Light irradiated from the back side of the diffusion plate 140 is reflected by the reflection sheet 130 and enters the diffusion plate 140 again.

[0036] In manufacturing Figure 1 In the process of manufacturing the direct-type backlight device 100 shown in FIG. 1 , in order to place the reflective sheet 130 on the plurality of LED bars 120 , the plurality of LEDs 122 in the plurality of LED bars 120 need to be manually inserted into the plurality of through holes 131 of the reflective sheet 130 .

[0037] As the size of the display device including the backlight device increases, the size of the direct-type backlight device 100 also increases. When the size of the reflective sheet 130 in the direct-type backlight device 100 also increases, it becomes very difficult to manually insert the plurality of LEDs 122 in the plurality of LED bars 120 into the plurality of through holes 131 of the reflective sheet 130 one by one.

[0038] Figure 2 is a cross-sectional view schematically showing a display device according to an embodiment. Figure 3 is a cross-sectional view schematically showing a direct-type backlight device according to an embodiment, Figure 4 It shows Figure 3 A plan view of a direct-lit backlight device.

[0039] refer to Figure 2 According to the embodiment, the display device 1 may include a liquid crystal panel 3 for displaying an image, a direct-type backlight device 10 configured to provide light to the liquid crystal panel 3, and an optical sheet 5 for improving the performance of light provided from the direct-type backlight device 10 to the liquid crystal panel 3.

[0040] The liquid crystal panel 3 is configured to receive light emitted by the backlight device 10 disposed below the liquid crystal panel 3 and display an image. The liquid crystal panel 3 may include a color filter substrate having a color filter layer and a thin film transistor substrate having a plurality of thin film transistors. Liquid crystal may be accommodated between the color filter substrate and the thin film transistor substrate. Since a liquid crystal panel manufactured according to a known technology can be used as the liquid crystal panel 3, a detailed description thereof is omitted.

[0041] The liquid crystal panel 3 may be coupled to a direct-type backlight device 10 including an upper frame 7. An opening 7a is provided on the upper frame 7, and the top surface of the liquid crystal panel 3 may be exposed through the opening 7a.

[0042] The optical sheet 5 is used to improve the optical characteristics of light incident from the direct-type backlight device 10 to the liquid crystal panel 3 , and is located between the liquid crystal panel 3 and the direct-type backlight device 10 .

[0043] The direct-type backlight device 10 (hereinafter referred to as the backlight device) is configured to provide light to the liquid crystal panel 3 and Figure 4 Shown as a rectangle in the plan view shown.

[0044] refer to Figure 3 and Figure 4 The backlight device 10 may include a diffusion plate 20, a plurality of light emitting diode (LED) bars 30 disposed below the diffusion plate 20, a reflection sheet 40 disposed above or below the plurality of light emitting diode (LED) bars 30, and a lower frame 50 disposed above or below the reflection sheet 40.

[0045] The diffusion plate 20 is formed to minimize the loss of light emitted from the plurality of LED bars 30 disposed therebelow and to uniformly distribute the light over the entire surface of the liquid crystal panel 3 while collecting the light in one direction.

[0046] The diffusion plate 20 is formed in a rectangular flat plate shape, the size of which corresponds to the liquid crystal panel 3, and also includes a transmissive material capable of transmitting light. For example, the diffusion plate 20 may include transparent plastic such as polymethyl methacrylate (PMMA), polycarbonate (PC), and the like.

[0047] The lower surface 21 of the diffuser plate 20 is an incident surface, on which light emitted from the plurality of LED bars 30 is incident, and the upper surface 22 of the diffuser plate 20 is an emitting surface, from which light emitted from the plurality of LED bars 30 is irradiated toward the liquid crystal panel 3. Therefore, light emitted from the plurality of LED bars 30 is incident on the lower surface 21 of the diffuser plate 20, and is irradiated toward the liquid crystal panel 3 through the upper surface 22 of the diffuser plate 20.

[0048] The optical sheet 5 may be disposed on the upper surface 22 of the diffuser plate 20, that is, between the diffuser plate 20 and the liquid crystal panel 3. The optical sheet 5 may reduce light loss by refraction and reflection of light to be emitted to the liquid crystal panel 3, thereby increasing the brightness of light emitted to the liquid crystal panel 3 through the diffuser plate 20, and making the light uniformly distributed on the liquid crystal panel 3.

[0049] The optical sheet 5 may include a prism sheet that improves brightness by refracting light, a dual brightness enhancement film that selectively transmits and reflects light to improve brightness, and other similar materials. The optical sheet 5 may be the same or similar to a general optical sheet used in a display device of a related process; therefore, a detailed description thereof is omitted.

[0050] A plurality of LED strips 30 are disposed below the diffusion plate 20 and are light sources for providing light to the liquid crystal panel 3. Figure 4 As shown, a plurality of LED bars 30 are disposed at fixed intervals on the upper surface of the lower frame 50, ie, on the reflective sheet 40, to uniformly provide light to the diffusion plate 20. The structure of the plurality of LED bars 30 will be described later.

[0051] The reflective sheet 40 is disposed above or below the plurality of LED strips 30. In detail, the reflective sheet 40 is disposed on the upper surface of the bottom 51 of the lower frame 50. The plurality of LED strips 30 are disposed on the upper surface of the reflective sheet 40. Accordingly, the reflective sheet 40 is located above or above the lower frame 50, and the LED strips 30 are located above or above the reflective sheet 40. In other words, the reflective sheet 40 is disposed between the lower frame 50 and the plurality of LED strips 30.

[0052] The reflective sheet 40 reflects part of the light emitted from the plurality of LED strips 30, and the light reflected from the optical sheet 5 is emitted through the lower surface of the diffuser 20, so that the reflected light is guided to the diffuser 20. The light reflected by the reflective sheet 40 is irradiated toward the liquid crystal panel 3 through the diffuser 20.

[0053] The reflective sheet 40 may be formed in a film shape (e.g., a rectangular shape) corresponding to the diffuser plate 20. The reflective sheet 40 may include white opaque plastic for reflecting light from the lower surface 21 of the diffuser plate 20. For example, the reflective sheet 40 may include any one of polyester terephthalate (PET), polycarbonate (PC), and polyester.

[0054] The lower frame 50 can be used to support the diffuser 20, the reflective sheet 40 and the plurality of LED strips 30. The reflective sheet 40 is disposed on the upper surface of the bottom 51 of the lower frame 50, and the plurality of LED strips 30 are disposed on the upper surface of the reflective sheet 40. On the edge of the bottom 51 of the lower frame 50, a side wall 53 extending vertically upward is disposed.

[0055] The lower frame 50 may include a metal material so that heat generated by the plurality of LED bars 30, a control panel controlling the liquid crystal panel 3, and the like can be easily dissipated to the outside. Figure 3 In the illustrated embodiment, the bottom portion 51 of the lower frame 50 is formed in a flat plate shape.

[0056] Figure 5 FIG. 2 is a cross-sectional view schematically showing another example of a direct-type backlight device according to an embodiment. Figure 5 As another example of the lower frame 50 , the bottom 51 ′ of the lower frame 50 may include a plurality of flanges 55 to increase rigidity while reducing thickness.

[0057] The lower frame 50 may be formed to be coupled with the upper frame 7. For example, the side wall 53 of the lower frame 50 may be formed to be coupled with the upper frame 7. Therefore, the liquid crystal panel 3 and the backlight device 10 may be fixed by the upper frame 7 and the lower frame 50.

[0058] In addition, a middle mold for supporting the liquid crystal panel 3 may be disposed between the lower frame 50 and the upper frame 7 .

[0059] In addition, the display device 1 may include a housing, which forms the appearance of the display device and accommodates the upper frame 7 and the lower frame 50. The display device 1 may also include a main control board arranged in the housing to control the liquid crystal panel 3 and the plurality of LED strips 30 to display images.

[0060] The following will refer to Figure 3 , Figure 4 and Figure 6 , a plurality of LED bars 30 used in the backlight device 10 are described in detail according to an embodiment. The plurality of LED bars 30 have the same structure; therefore, for ease of description, only one LED bar 30 is described below.

[0061] Figure 6 is a partial cross-sectional view showing an example of an LED bar used in a direct-type backlight device according to an embodiment.

[0062] refer to Figure 3 , Figure 4 and Figure 6 The LED bar 30 may include a bar-shaped printed circuit board 31 and a plurality of light emitting diodes (LEDs) 33 disposed on an upper surface of the printed circuit board 31 .

[0063] The printed circuit board 31 is in a strip shape, such as a narrow and long rectangular flat plate. On the upper surface of the printed circuit board 31, a plurality of LEDs 33 are arranged at certain intervals. In addition, a power line for supplying power to the plurality of LEDs 33 may also be arranged in the printed circuit board 31.

[0064] The plurality of LEDs 33 are configured to emit light and are disposed at certain intervals on the upper surface of the printed circuit board 31. In addition, the plurality of LEDs 33 are arranged in a straight line on the upper surface of the printed circuit board 31. Light generated by the plurality of LEDs 33 is irradiated toward the liquid crystal panel 3 through the diffusion plate 20. The plurality of LEDs 33 may be disposed on the printed circuit board 31 using a surface mounting technology. Since the plurality of LEDs 33 are the same as or similar to general LEDs, a detailed description thereof is omitted.

[0065] The upper surface of the printed circuit board 31 may be provided with a reflective member 35 capable of reflecting a portion of light emitted from the plurality of LEDs 33 and light emitted from the lower surface of the diffusion plate 20. The reflective member 35 may be provided on a portion of the upper surface of the printed circuit board 31 where the plurality of LEDs 33 are not provided. Accordingly, the reflective member 35 may be provided to cover most or almost all of the upper surface of the printed circuit board 31 except for a portion where the plurality of LEDs 33 are provided.

[0066] The reflective component 35 can be formed to have a certain reflectivity, such as 90% or more of the reflectivity of the reflective sheet 40. To this end, the reflective component 35 can be formed of a photo solder resist (PSR) layer with high reflectivity. In other words, the PSR layer can be formed on the upper surface of the printed circuit board 31 as the reflective component 35. In the following description, the reflectivity can include specular reflectivity and diffuse reflectivity. When not specified, the reflectivity refers to the lower reflectivity of the specular reflectivity and the diffuse reflectivity.

[0067] The process of manufacturing the LED strip 30 may include a photo solder resist (PSR) process for applying PSR ink or PSR paint on the upper surface of the printed circuit board 31 to coat the inactive area; and a reflow process for mounting multiple LEDs 33 on the portion of the upper surface of the printed circuit board 31 coated with the PSR ink or PSR paint.

[0068] In the PSR process, permanent ink may be applied to the upper surface of the printed circuit board 31 to protect the circuits on the upper surface of the printed circuit board 31 and prevent solder bridges from occurring between the circuits in subsequent processes.

[0069] The PSR process may include a pretreatment operation, a printing operation, a PSR exposure operation, a PSR development operation, and a drying operation.

[0070] The pretreatment operation is a process of removing substances such as oxide film and oil that adversely affect the adhesion between the surface (such as the upper surface) of the printed circuit board 31 and the PSR ink, and is a process of increasing the roughness of the surface of the copper foil constituting the circuit. Therefore, in the printing operation, the adhesion between the PSR ink and the copper foil is improved.

[0071] The printing operation is a process of protecting the circuit of the printed circuit board 31 by applying PSR ink to the surface of the printed circuit board 31 where the circuit is formed. The printing operation can be divided into a screen coating method, a spray coating method, and the like according to a method of applying the PSR ink to the surface of the printed circuit board 31.

[0072] The PSR exposure operation is to selectively photo-cure the PSR ink coated on the upper surface of the printed circuit board 31 into a region serving as a resist and a region exposing the copper foil by using a patterned exposure mask and ultraviolet rays.

[0073] The PSR developing operation is a process of exposing the copper foil by removing, with a developer, a portion of the PSR ink on the printed circuit board 31 that is not cured due to not receiving ultraviolet rays after exposure.

[0074] The drying operation refers to a process in which the PSR ink is completely cured by applying hot air to the printed circuit board 31 for a period of time after the PSR development operation is completed.

[0075] When the PSR process is completed as described above, the upper surface of the printed circuit board 31 is in a state where only the copper foils at portions where the plurality of LEDs 33 are to be disposed are exposed, and a PSR layer 35 having high reflectivity is formed on the remaining portions.

[0076] When the PSR process is completed, the plurality of LEDs 33 are mounted on the printed circuit board 31. For example, the plurality of LEDs 33 may be mounted on the plurality of exposed copper foil portions of the printed circuit board 31 using a reflow process.

[0077] Specifically, the reflow process may include a printing process, a mounting process, and a reflow process.

[0078] During the printing process, solder paste is applied to the exposed portions of the copper foil in the printed circuit board 31 .

[0079] The mounting process is performed after the printing process is completed. In the mounting process, a plurality of LEDs 33 are placed on the portion of the printed circuit board 31 where the copper foil is exposed, that is, on the portion where solder paste is applied using a surface mount technology (SMT) machine.

[0080] Thereafter, a reflow process is performed. In the reflow process, when the solder paste is melted by heating using a reflow machine, the plurality of LEDs 33 are fixed on the printed circuit board 31. The reflow process may be performed two or more times as required.

[0081] The LED bar 30 used in the backlight device 10 according to the embodiment of the present disclosure may be manufactured through the above-mentioned PSR process and reflow process.

[0082] In an embodiment, in order to form the PSR layer 35 having high reflectivity in the PSR process, a PSR ink or a PSR paint having high reflectivity may be used.

[0083] As another example, in order to increase the reflectivity of the PSR layer 35 , a PSR ink having a general reflectivity, for example, a PSR ink having a reflectivity of about 81% to 83%, may be applied twice or more to form the PSR layer 35 . Figure 6 The case where the PSR layer 35 is formed by applying the PSR ink twice is shown. When the PSR layer 35 is formed by applying the PSR ink twice, the thickness of the PSR layer 35 is approximately doubled, and the reflectivity of the PSR layer 35 can be increased.

[0084] As another example, the reflectivity of the PSR layer 35 may be increased by surface-treating the upper surface of the PSR layer 35 including the PSR ink having a general reflectivity.

[0085] On the other hand, the LED bar 120 (see FIG. Figure 1 ), the reflectivity (such as diffuse reflection, specular reflection excluded (SCE)) of the upper surface of the printed circuit board 121 is about 81% to 83%. On the other hand, the reflectivity (such as diffuse reflection) of the reflective sheet 130 is about 97%.

[0086] Therefore, when the LED bar 120 of the general direct-type backlight device is disposed on the reflective sheet 40 , a difference in brightness may occur on the screen of the liquid crystal panel due to the difference in reflectivity between the upper surface of the printed circuit board 121 and the reflective sheet 130 .

[0087] For example, a dark horizontal line corresponding to the LED bar 120 in the prior art may appear on the liquid crystal panel. In other words, when the LED bar 120 in the prior art is used, the LED bar 120 can be identified or seen through the liquid crystal panel. That is, there is a problem that the user may recognize the LED bar 120 through the liquid crystal panel.

[0088] To solve this problem, according to the embodiment of the present disclosure, a PSR layer 35 may be formed on the upper surface of the printed circuit board 31, and the reflectivity of the PSR layer 35 of the printed circuit board 31 of the LED bar 30 may be about 90% of the reflectivity of the reflective sheet 40. In other words, when the reflectivity of the reflective sheet 40 is 100%, the reflectivity of the formed PSR layer 35 is 90% or more. When the reflectivity of the reflective sheet 40 is 97%, the reflectivity of the formed PSR layer 35 is about 87% or more.

[0089] In the above, the reflectivity of the PSR layer 35 is described as being approximately 90% of the reflectivity of the reflective sheet 40; however, this is merely an example and is not limiting. According to the embodiment, the ratio of the reflectivity of the PSR layer 35 to the reflectivity of the reflective sheet 40 may be determined as appropriate. For illustrative purposes, the following describes an example in which the reflectivity of the reflective sheet 40 is 97%, and the reflectivity of the PSR layer 35 is formed to be approximately 87% or more.

[0090] Because the upper surface of the PSR layer 35 is located above the upper surface of the reflective sheet 40 by the thickness of the printed circuit board 31 , when the reflectivity of the PSR layer 35 is approximately 90% or more of the reflectivity of the reflective sheet 40 , the LED strip 30 cannot be seen through the liquid crystal panel 3 .

[0091] As described above, since the printed circuit board 31 provided with the plurality of LEDs 33 passes through the reflow process at least once in the process of manufacturing the LED bar 30 , the reflectivity of the PSR layer 35 formed on the printed circuit board 31 may be changed.

[0092] Therefore, PSR ink that allows the reflectivity of the PSR layer 35 of the printed circuit board 31 to reach 90% or more of the reflectivity of the reflective sheet 40 after the reflow process is completed can be used. In other words, the PSR layer 35 can be formed using PSR ink that allows the reflectivity of the PSR layer 35 to be approximately 87% or more.

[0093] On the other hand, when the printed circuit board 31 is subjected to two reflow processes to form the LED bar 30, the reflectivity of the PSR layer 35 needs to reach 90% or more of the reflectivity of the reflective sheet 40 after the reflow process is completed twice. In other words, a PSR ink that makes the reflectivity of the PSR layer 35 of the printed circuit board 31 about 87% or more after the reflow process is completed twice can be used.

[0094] Alternatively, the PSR layer 35 may be formed by applying PSR ink having a general reflectivity on the printed circuit board 31 twice or more, so that the reflectivity of the PSR layer 35 is about 87% or more.

[0095] For example, refer to Figure 6 , a PSR ink with a general reflectivity is applied to the upper surface of the printed circuit board 31, and after drying, a PSR lower layer 35a with a thickness of about 20 to 25 μm is formed. Subsequently, the same PSR ink is applied to the PSR lower layer 35a, and after drying, a PSR upper layer 35b is formed. In this way, a PSR layer 35 is formed, including a PSR lower layer 35a and a PSR upper layer 35b, and the thickness thereof is about 40 μm-50 μm. Thereby, the reflectivity of the upper surface of the PSR layer 35 (i.e., the upper surface of the PSR upper layer 35b) is improved, so that the reflectivity of the PSR layer 35 of the printed circuit board 31 after the reflow process reaches 87% or higher.

[0096] On the other hand, when the printed circuit board 31 undergoes two reflow processes to form the LED bar 30 , the reflectivity of the PSR layer 35 including the PSR lower layer 35 a and the PSR upper layer 35 b is 90% or more of the reflectivity of the reflective sheet 40 after the two reflow processes are completed.

[0097] Table 1 below shows how the reflectivity of the PSR layer 35 changes with the reflow process.

[0098] Table 1

[0099]

[0100] In Table 1, "reference" in the column of the number of reflow times indicates the reflectivity of the PSR layer 35 formed on the printed circuit board 31 before the reflow process is performed. "once" indicates that the reflow process is performed once on the printed circuit board 31 on which the PSR layer 35 is formed, and "twice" indicates that the reflow process is performed twice on the printed circuit board 31 on which the PSR layer 35 is formed. Table 1 includes two reflectivities of the PSR layer 35, one is the reflectivity including the specular component (SCI) and the other is the reflectivity excluding the specular component (SCE). The SCI reflectivity is the specular reflectivity of the PSR layer 35, and the SCE reflectivity is the diffuse reflectivity of the PSR layer 35.

[0101] As can be seen from Table 1 above, the reflectivity of the PSR layer 35 of the printed circuit board 31 exceeds 87% for both the specular reflectivity (SCI) and the diffuse reflectivity (SCE). In particular, it can be seen that even after two reflows, the SCI reflectivity and the SCE reflectivity of the PSR layer 35 still exceed 87%. Therefore, the reflectivity of the LED strip 30 having the above-mentioned PSR layer 35 according to the embodiment is also greater than 87%.

[0102] The following will refer to Figure 7 An LED strip according to another embodiment is described in detail.

[0103] Figure 7 is a partial cross-sectional view showing another example of an LED bar used in the direct-type backlight device according to the embodiment.

[0104] refer to Figure 7 According to an embodiment, the LED bar 30 ′ may include a printed circuit board 31 , a plurality of LEDs 33 , and a reflective member 37 .

[0105] The printed circuit board 31 and the plurality of LEDs 33 may be the same as or similar to those of the above-described embodiment; therefore, a detailed description thereof is omitted.

[0106] The reflective component 37 can be used as a reflective layer and is formed on the PSR protective layer 36 of the printed circuit board 31. Figure 6 In the embodiment of the present invention, the PSR layer 35 has the function of reflecting light, but in Figure 7 In the embodiment of the present invention, a separate reflective layer 37 may be formed on the PSR protective layer 36. Therefore, unlike the above-mentioned PSR layer 35, the PSR protective layer 36 formed on the printed circuit board 31 does not need to have a high reflectivity.

[0107] After forming the PSR protective layer 36 on the printed circuit board 31, the reflective layer 37 may be formed using a reflective ink or a reflective paint different from the PSR ink or the PSR paint used to form the PSR protective layer 36. For example, after forming the PSR protective layer 36 on the printed circuit board 31, the reflective ink is applied to the upper surface of the PSR protective layer 36 with a predetermined thickness, thereby forming the reflective layer 37.

[0108] The reflective layer 37 may be formed to have a reflectivity of about 90% of the reflectivity of the reflective sheet 40. In other words, when the reflectivity of the reflective sheet 40 is 100%, the reflective layer 37 is formed to have a reflectivity of 90% or more. For example, when the reflectivity of the reflective sheet 40 is 97%, the reflective layer 37 is formed to have a reflectivity of 87% or more.

[0109] As described above, since the printed circuit board 31 on which the plurality of LEDs 33 are disposed undergoes at least one reflow process during the manufacturing process of the LED bar 30 ′, the reflectivity of the reflective layer 37 formed on the printed circuit board 31 may be changed.

[0110] Therefore, the reflective layer 37 can be formed by using a reflective ink or a reflective paint that can make the reflectivity of the reflective layer 37 of the printed circuit board 31 reach 90% or more of the reflective sheet 40 after the reflow process is completed. In other words, when the reflectivity of the reflective sheet 40 is 97%, the reflective layer 37 is formed by using a reflective ink or a reflective paint that makes the reflectivity of the reflective layer 37 about 87% or more.

[0111] On the other hand, when the printed circuit board 31 is subjected to two reflow processes to form the LED strip 30', after the reflow processes are completed twice, the reflectivity of the reflective layer 37 needs to reach 90% or more of the reflectivity of the reflective sheet 40. In other words, when the reflectivity of the reflective sheet 40 is 97%, a reflective ink or a reflective paint is used that makes the reflectivity of the reflective layer 37 about 87% or more after the reflow processes are completed twice.

[0112] In the above description, the reflective ink or reflective paint forming the reflective layer 37 is an ink or paint having a different composition from the PSR ink or PSR paint, and makes the reflective layer 37 have a high reflectivity when it is applied on the upper surface of the PSR protective layer 36 of the printed circuit board 31.

[0113] The following will refer to Figure 8 and Fig. 9 , an LED strip according to another embodiment is described in detail.

[0114] Figure 8 is a partial cross-sectional view of another example of an LED bar used in a direct-type backlight device according to an embodiment. Fig. 9 Shows the settings in Figure 8 Plan view of the reflector cover on the LED strip.

[0115] refer to Figure 8 According to the embodiment, the LED bar 30 ″ may include a printed circuit board 31 , a plurality of LEDs 33 , and a reflective member 38 .

[0116] The printed circuit board 31 and the plurality of LEDs 33 are the same as or similar to those of the LED bar 30 of the above-described embodiment; therefore, a detailed description thereof is omitted.

[0117] The reflective member 38 may be formed as a reflective cover disposed on the PSR protective layer 36 of the printed circuit board 31. Figure 6 In the embodiment, the PSR layer 35 of the printed circuit board 31 has the function of reflecting light, and Figure 8 In the embodiment, a separate reflective cover 38 is disposed on the PSR protective layer 36 .

[0118] like Fig. 9As shown, the reflector 38 is formed in a shape corresponding to the printed circuit board 31 and includes a plurality of through holes 39 into which the plurality of LEDs 33 are inserted.

[0119] In more detail, the reflector 38 includes a long and narrow rectangular film, and a plurality of through holes 39 into which the plurality of LEDs 33 are inserted are formed in a straight line. For example, the reflector 38 is formed to have the same size and shape as the printed circuit board 31, and includes a plurality of through holes 39 corresponding to the plurality of LEDs 33 disposed on the printed circuit board 31.

[0120] Therefore, when the reflector 38 is disposed on the upper surface of the printed circuit board 31, the plurality of LEDs 33 extend from the plurality of through holes 39 of the reflector 38, and the upper surface of the printed circuit board 31 is covered by the reflector 38 so that the upper surface of the printed circuit board 31 is not exposed.

[0121] The reflective cover 38 may include the same material as the reflective sheet 40 disposed on the lower frame 50. As another example, the reflective cover 38 may include a material different from the reflective sheet 40, and its reflectivity is about 90% or more of that of the reflective sheet 40.

[0122] The reflection cover 38 may be disposed on the upper surface of the printed circuit board 31 after the LED bar 30 ″ including components other than the reflection cover 38 is manufactured and before the LED bar 30 ″ including the reflection cover 38 is disposed on the lower frame 50 .

[0123] As another example, a plurality of openings may be provided in the reflective sheet 40 for placing a plurality of LED strips 30". The sizes of the plurality of openings correspond to the plurality of LED strips 30". Therefore, when the plurality of LED strips 30" are placed in the plurality of openings of the reflective sheet 40, the printed circuit board 31 is located on the bottom 51 of the lower frame 50, and the bottom 51 of the lower frame 50 on which the reflective sheet 40 is placed is not exposed.

[0124] In this example, the reflective cover 38 can be manufactured by using rectangular pieces of the reflective sheet 40 cut when forming the plurality of openings of the reflective sheet 40. When the reflective cover 38 includes the portions cut from the reflective sheet 40 as described above, material costs can be reduced.

[0125] The following will refer to Fig.10 A method of manufacturing a direct type backlight device according to an embodiment is described.

[0126] Fig.10 is a flow chart showing a method of manufacturing a direct type backlight device according to an embodiment.

[0127] To manufacture the direct-type backlight device 10, first, the lower frame 50 and the reflective sheet 40 are prepared. A plurality of through holes corresponding to the plurality of LEDs 33 of the plurality of LED bars 30 are not formed in the reflective sheet 40. Since a process of forming a plurality of through holes on the reflective sheet 40 is not necessary, the manufacturing cost of the reflective sheet 40 can be reduced.

[0128] Subsequently, the reflective sheet 40 is disposed on the upper surface of the bottom 51 of the lower frame 50 (S10). The reflective sheet 40 may be fixed to the lower frame 50 using an adhesive, a double-sided tape, or the like. Alternatively, the reflective sheet 40 may be fixed to the lower frame 50 using a plurality of LED bars 30 without using an adhesive or a double-sided tape.

[0129] After the reflective sheet 40 is disposed on the lower frame 50, a plurality of LED bars 30 are disposed on the upper surface of the reflective sheet 40 (S20). The plurality of LED bars 30 are spaced apart from each other by a predetermined distance and are disposed parallel to each other on the upper surface of the reflective sheet 40, such as Figure 4 shown.

[0130] The plurality of LED bars 30 may be fixed to the lower frame 50 by using a fastening member such as a bolt and a screw. In other words, the fastening member penetrates the reflective sheet 40 to fix the plurality of LED bars 30 to the lower frame 50.

[0131] As another example, the lower frame 50 may have a plurality of fixing members capable of fixing the plurality of LED bars 30 , such that each of the plurality of LED bars 30 is coupled to each of the plurality of fixing members in one operation (eg, a one-touch operation).

[0132] Finally, the diffusion plate 20 is disposed above the plurality of LED bars 30 (S30). The diffusion plate 20 may be supported by a plurality of support members disposed on the lower frame 50. The plurality of support members may be disposed on the reflective sheet 40. Alternatively, the plurality of support members may be disposed on the printed circuit board 31 of the LED bar 30 on the reflective sheet 40.

[0133] As described above, in the direct type backlight device 10 according to the embodiment, after the reflective sheet 40 is disposed on the lower frame 50, the plurality of LED bars 30, 30' and / or 30" are disposed on or above the reflective sheet 40. Therefore, it is not necessary to make through holes in the reflective sheet 40.

[0134] Therefore, when assembling the direct type backlight device 10, there is no operation of inserting the plurality of LEDs into the through holes of the reflection sheet 40. Therefore, the assembly of the direct type backlight device 10 can be simple.

[0135] Therefore, compared with the related art direct-type backlight device, the productivity of the direct-type backlight device according to the embodiment is improved, and the manufacturing cost of the direct-type backlight device and the display device having the same can be reduced.

[0136] In the direct-type backlight device according to the embodiment having the above structure, since the plurality of LED bars are arranged on or above the reflective sheet, there is no need for an operation of inserting the plurality of LEDs into the plurality of through holes of the reflective sheet, which is required in the direct-type backlight device of the prior art. Therefore, since the assembly of the direct-type backlight device is simple, the direct-type backlight device according to the embodiment and the display device having the direct-type backlight device are improved in productivity and manufacturing cost.

[0137] While several embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made to the embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.

Claims

1. A direct-type backlight device, comprising: Lower frame; A reflective sheet disposed on the bottom of the lower frame; as well as A plurality of light emitting diode (LED) strips are arranged on the upper surface of the reflective sheet, Wherein, each LED strip of the plurality of LED strips comprises: A strip-shaped printed circuit board disposed on the upper surface of the reflective sheet; a plurality of LEDs disposed on an upper surface of the printed circuit board; a reflective member disposed on the upper surface of the printed circuit board, and The reflective component includes a photo solder resist PSR layer, wherein the photo solder resist PSR layer includes a PSR lower layer and a PSR upper layer formed of the same PSR ink, wherein the plurality of LEDs are fixed to the printed circuit board on which the PSR layer is disposed by disposing the plurality of LEDs on the printed circuit board including the PSR layer and performing a reflow process twice on the printed circuit board on which the plurality of LEDs are disposed, and Wherein, after each time the reflow process is performed on the PSR layer, the reflectivity of the PSR layer decreases, and the PSR ink has a reflectivity such that the reflectivity of the PSR layer on which the reflow process has been performed twice is at least 90% of the reflectivity of the reflective sheet and less than the reflectivity of the reflective sheet.

2. The direct type backlight device as claimed in claim 1, wherein the PSR layer is formed by applying PSR ink on the printed circuit board twice. 3 . The direct-type backlight device as claimed in claim 1 , wherein a reflectivity of the PSR layer is 87% or higher.

4. A display device, comprising: LCD panel; a diffusion plate disposed below the liquid crystal panel; A plurality of light emitting diode (LED) strips are arranged below the diffusion plate; A reflective sheet disposed below the plurality of LED strips; as well as A lower frame disposed below the reflective sheet, the lower frame being configured to support the reflective sheet; Wherein, each LED strip of the plurality of LED strips comprises: A strip-shaped printed circuit board disposed on or above the reflective sheet; a plurality of LEDs disposed on an upper surface of the printed circuit board; and a reflective member disposed on the upper surface of the printed circuit board, and The reflective component includes a photo solder resist PSR layer, wherein the photo solder resist PSR layer includes a PSR lower layer and a PSR upper layer formed of the same PSR ink, wherein the plurality of LEDs are fixed to the printed circuit board on which the PSR layer is disposed by disposing the plurality of LEDs on the printed circuit board including the PSR layer and performing a reflow process twice on the printed circuit board on which the plurality of LEDs are disposed, and Wherein, after each time the reflow process is performed on the PSR layer, the reflectivity of the PSR layer decreases, and the PSR ink has a reflectivity such that the reflectivity of the PSR layer on which the reflow process has been performed twice is at least 90% of the reflectivity of the reflective sheet and less than the reflectivity of the reflective sheet. 5 . The display device of claim 4 , wherein the PSR layer is formed by applying PSR ink twice on the printed circuit board.

6. A method for manufacturing a direct-type backlight device, the method comprising: providing a reflective sheet on an upper surface of the bottom of the lower frame; After the reflective sheet is arranged on the lower frame, a plurality of light emitting diode (LED) strips are arranged on the upper surface of the reflective sheet, each of the plurality of LED strips comprising a printed circuit board, a plurality of LEDs and a reflective component; as well as providing a diffusion plate above the plurality of LED strips, The reflective component includes a photo solder resist PSR layer, wherein the photo solder resist PSR layer includes a PSR lower layer and a PSR upper layer formed of the same PSR ink, wherein the plurality of LEDs are fixed to the printed circuit board on which the PSR layer is disposed by disposing the plurality of LEDs on the printed circuit board including the PSR layer and performing a reflow process twice on the printed circuit board on which the plurality of LEDs are disposed, and Wherein, after each time the reflow process is performed on the PSR layer, the reflectivity of the PSR layer decreases, and the PSR ink has a reflectivity such that the reflectivity of the PSR layer on which the reflow process has been performed twice is at least 90% of the reflectivity of the reflective sheet and less than the reflectivity of the reflective sheet.

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