Patent Description:
Currently, a liquid crystal display apparatus, which occupies the largest portion in a display market, uses a liquid crystal panel that cannot emit light itself, and a backlight device is used as a light source of the liquid crystal display apparatus.

When the backlight device irradiates light toward the liquid crystal panel, the liquid crystal panel may display an image.

Such a backlight device may be generally classified into an edge type backlight device and a direct type backlight device depending on the arrangement structure of the light source.

The edge type backlight device has a structure in which one light source is disposed on one side of a light guide plate, or two light sources are disposed on both sides of the light guide plate. A reflective sheet is disposed below the light guide plate to reflect light exiting a bottom surface of the light guide plate toward the liquid crystal panel. A diffusion sheet for diffusing light exiting a top surface of the light guide plate may be provided on an upper side of the light guide plate.

On the other hand, the direct type backlight device has a structure in which a plurality of light sources are disposed under a diffusion plate.

There is a problem in the related art that the productivity of the direct type backlight device and the display apparatus including the direct type backlight device decreases with the increase in the size of the display apparatus.

<CIT> and <CIT> disclose display devices having a direct type backlight device. <CIT> discloses a substrate for mounting optical semiconductor elements.

Provided are a direct type backlight device capable of improving productivity and a display apparatus having the same.

In accordance with aspects of the invention, there is provided a direct type backlight device according to claim <NUM> and a method of manufacturing a direct type backlight device according to claim <NUM>.

These and/or other aspects and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings of which:.

Hereinafter, certain embodiments of a direct type backlight device and a display apparatus having the same according to the disclosure will be described in detail with reference to the accompanying drawings.

Various embodiments will hereinafter be described with reference to the accompanying drawings. The matters defined herein, such as a detailed construction and elements thereof, are provided to assist in a comprehensive understanding of this description. Thus, it is apparent that embodiments may be carried out without those defined matters. Also, well-known functions or constructions are omitted to provide a clear and concise description of embodiments. Further, dimensions of various elements in the accompanying drawings may be arbitrarily increased or decreased for assisting in a comprehensive understanding.

The terms 'first', 'second', etc. may be used to describe diverse components, but the components are not limited by the terms. The terms may only be used to distinguish one component from the others. For example, without departing from the scope of the disclosure, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

The terms used in embodiments of the disclosure may be construed as commonly known to those skilled in the art unless otherwise defined.

Further, the terms 'leading end', 'rear end', 'upper side', 'lower side', 'top end', 'bottom end', etc. used in the disclosure are defined with reference to the drawings. However, the shape and position of each component are not limited by the terms.

In the following description, when an element is referred to as being "above", "over", "on", "connected to" or "coupled to" another element, it may be directly above, over, on, connected to, or coupled to the other element while making contact with the other element or may be above, over, on, connected to, or coupled to the other element without making contact with the other element (that is, intervening element(s) may be present).

<FIG> is a cross-sectional view schematically illustrating a general direct type backlight device that is useful for understanding the invention.

Referring to <FIG>, a general direct type backlight device <NUM> includes a lower chassis <NUM>, a light emitting diode (LED) bar <NUM>, a reflective sheet <NUM>, and a diffusion plate <NUM>. Although only one LED bar <NUM> is shown in <FIG>, the general direct type backlight device <NUM> includes a plurality of LED bars <NUM>.

The plurality of LED bars <NUM> are disposed and spaced apart at predetermined intervals on an upper surface of the lower chassis <NUM>. Each of the plurality of LED bars <NUM> includes a bar-shaped printed circuit board <NUM> and a plurality of LEDs <NUM> disposed on the printed circuit board <NUM>.

The reflective sheet <NUM> having a size corresponding to the diffusion plate <NUM> is disposed on the plurality of LED bars <NUM>. A plurality of through holes <NUM> are formed in the reflective sheet <NUM> so that the plurality of LEDs <NUM> provided on the plurality of LED bars <NUM> may be exposed through the plurality of through holes <NUM>. Accordingly, when the reflective sheet <NUM> is disposed on the plurality of LED bars <NUM> provided on the lower chassis <NUM>, the plurality of LEDs <NUM> protrude from the reflective sheet <NUM>, and the printed circuit boards <NUM> are positioned under the reflective sheet <NUM>. In other words, the printed circuit boards <NUM> of the LED bars <NUM> are covered by the reflective sheet <NUM>.

The diffusion plate <NUM> is provided above the reflective sheet <NUM> and the plurality of LEDs <NUM>.

A liquid crystal panel is provided above the diffusion plate <NUM>, and light emitted from the plurality of LEDs <NUM> moves through the diffusion plate <NUM> toward the light crystal panel. The light exiting a rear surface of the diffusion plate <NUM> is reflected by the reflective sheet <NUM> and again enters the diffusion plate <NUM>.

When manufacturing the direct type backlight device <NUM> as illustrated in <FIG>, in order to dispose the reflective sheet <NUM> on the plurality of LED bars <NUM>, the plurality of LEDs <NUM> of the plurality of LED bars <NUM> need to be manually inserted into the plurality of through holes <NUM> formed in the reflective sheet <NUM>.

As a display apparatus including the backlight device becomes larger, a size of the direct type backlight device <NUM> also increases. When a size of the reflective sheet <NUM> of the direct type backlight device <NUM> also increases, it becomes very difficult to manually insert the plurality of LEDs <NUM> of the plurality of LED bars <NUM> one by one into the plurality of through holes <NUM> formed in the reflective sheet <NUM>.

<FIG> is a cross-sectional view schematically illustrating a display apparatus according to an embodiment that is useful for understanding the invention. <FIG> is a cross-sectional view schematically illustrating a direct type backlight device according to an embodiment of the invention, and <FIG> is a plan view illustrating the direct type backlight device of <FIG>.

Referring to <FIG>, a display apparatus <NUM> may include a liquid crystal panel <NUM> configured to display an image, a direct type backlight device <NUM> configured to supply light to the liquid crystal panel <NUM>, and an optical sheet <NUM> to improve properties of the light being supplied from the direct type backlight device <NUM> to the liquid crystal panel <NUM>.

The liquid crystal panel <NUM> is configured to receive light from the backlight device <NUM>, disposed under the liquid crystal panel <NUM>, and to display an image. The liquid crystal panel <NUM> may include a color filter substrate having a color filter layer and a thin film transistor substrate having a plurality of thin film transistors. A liquid crystal may be accommodated between the color filter substrate and the thin film transistor substrate. Because a liquid crystal panel according to a known technique may be used as the liquid crystal panel <NUM>, a detailed description thereof is omitted.

The liquid crystal panel <NUM> may be coupled to the direct type backlight device <NUM> including an upper chassis <NUM>. The upper chassis <NUM> is provided with an opening 7a through which a top surface of the liquid crystal panel <NUM> is exposed.

The optical sheet <NUM> is used for improving the optical characteristics of light incident from the direct type backlight device <NUM> to the liquid crystal panel <NUM>, and is provided between the liquid crystal panel <NUM> and the direct type backlight device <NUM>.

The direct type backlight device <NUM> (hereinafter, referred to as a backlight device) is configured to supply light to the liquid crystal panel <NUM> and has a rectangular shape when viewed in a plan view as shown in <FIG>.

Referring to <FIG> and <FIG>, the backlight device <NUM> includes a diffusion plate <NUM>, a plurality of light emitting diode (LED) bars <NUM> disposed under the diffusion plate <NUM>, a reflective sheet <NUM> provided on or under the plurality of LED bars <NUM>, and a lower chassis <NUM> provided on or under the reflective sheet <NUM>.

The diffusion plate <NUM> is formed to minimize the loss of light emitted from the plurality of LED bars <NUM> provided thereunder, and to distribute light evenly over an entire surface of the liquid crystal panel <NUM> and at the same time collect light in one direction.

The diffusion plate <NUM> is formed in a rectangular flat plate shape having a size corresponding to the liquid crystal panel and includes a transmissive material capable of transmitting light. For example, the diffusion plate <NUM> may include a transparent plastic such as polymethyl methacrylate (PMMA), polycarbonate (PC), and the like.

A lower surface <NUM> of the diffusion plate <NUM> is an incident surface on which light emitted from the plurality of LED bars <NUM> is incident, and an upper surface <NUM> of the diffusion plate <NUM> is a light exit surface from which the light incident from the plurality of LED bars <NUM> is emitted toward the liquid crystal panel <NUM>. Therefore, the light emitted from the plurality of LED bars <NUM> is incident on the lower surface <NUM> of the diffusion plate <NUM>, passes through the diffusion plate <NUM>, and is discharged toward the liquid crystal panel <NUM> through the upper surface <NUM> of the diffusion plate <NUM>.

The optical sheet <NUM> may be disposed on the upper surface <NUM> of the diffusion plate <NUM>, that is, between the diffusion plate <NUM> and the liquid crystal panel <NUM>. The optical sheet <NUM> may minimize light loss by using refraction and reflection of light to be emitted toward the liquid crystal panel thereby improving brightness of light emitted through the diffusion plate <NUM> toward the liquid crystal panel <NUM> and allowing light to be evenly distributed on the liquid crystal panel <NUM>.

The optical sheet <NUM> 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 the like. The optical sheet <NUM> may be the same as or similar to the general optical sheets used in the related art display apparatus; therefore, a detailed description thereof is omitted.

The plurality of LED bars <NUM> is a light source that supplies light to the liquid crystal panel <NUM> and is disposed under the diffusion plate <NUM>. The plurality of LED bars <NUM> are disposed at regular intervals on an upper surface of the lower chassis <NUM>, that is, on the reflective sheet <NUM>, as illustrated in <FIG> to uniformly supply light to the diffusion plate <NUM>. The structure of the plurality of LED bars <NUM> will be described later.

The reflective sheet <NUM> is disposed on or under the plurality of LED bars <NUM>. In detail, the reflective sheet <NUM> is disposed on an upper surface of a bottom portion <NUM> of the lower chassis <NUM>. The plurality of LED bars <NUM> are disposed on an upper surface of the reflective sheet <NUM>. Accordingly, the reflective sheet <NUM> is positioned on or over the lower chassis <NUM> and the LED bars <NUM> are positioned on or over the reflective sheet <NUM>. In other words, the reflective sheet <NUM> is disposed between the lower chassis <NUM> and the plurality of LED bars <NUM>.

The reflective sheet <NUM> reflects a part of light emitted from the plurality of LED bars <NUM>, and light that is reflected from the optical sheet <NUM> and then exits through a lower surface of the diffusion plate <NUM>, such that the reflected light is guided toward the diffusion plate <NUM>. The light reflected by the reflective sheet <NUM> travels toward the liquid crystal panel <NUM> through the diffusion plate <NUM>.

The reflective sheet <NUM> may be formed in a thin film shape (e.g., a rectangular shape) corresponding to the diffusion plate <NUM>. The reflective sheet <NUM> may include white opaque plastic to reflect light from the lower surface <NUM> of the diffusion plate <NUM>. For example, the reflective sheet <NUM> may include any one of polyester terephthalate (PET), polycarbonate (PC), and polyester.

The lower chassis <NUM> may support the diffusion plate <NUM>, the reflective sheet <NUM>, and the plurality of LED bars <NUM>. The reflective sheet <NUM> is disposed on the upper surface of the bottom portion <NUM> of the lower chassis <NUM>, and the plurality of LED bars <NUM> are disposed on the upper surface of the reflective sheet <NUM>. On an edge of the bottom portion <NUM> of the lower chassis <NUM>, side walls <NUM> extending vertically upward are provided.

The lower chassis <NUM> may include a metal material so that heat generated from the plurality of LED bars <NUM>, a control panel configured to control the liquid crystal panel and the like may be easily dissipated to the outside. In the embodiment shown in <FIG>, the bottom portion <NUM> of the lower chassis <NUM> is formed in a flat plate shape.

<FIG> is a cross-sectional view schematically illustrating another example of a direct type backlight device according to an embodiment. As another example of the lower chassis <NUM>, as illustrated in <FIG>, a bottom portion <NUM>' of the lower chassis <NUM> may include a plurality of beadings <NUM> to increase rigidity while reducing thickness.

The lower chassis <NUM> may be formed to be coupled with the upper chassis <NUM>. For example, the side walls <NUM> of the lower chassis <NUM> may be formed to be coupled with the upper chassis <NUM>. Therefore, the liquid crystal panel <NUM> and the backlight device <NUM> may be fixed by the upper chassis <NUM> and the lower chassis <NUM>.

In addition, a middle mold supporting the liquid crystal panel <NUM> may be disposed between the lower chassis <NUM> and the upper chassis <NUM>.

Further, the display apparatus <NUM> may include a case that forms an external appearance of the display apparatus <NUM> and accommodates the upper chassis <NUM> and the lower chassis <NUM>, and may include a main control panel that is provided inside the case and configured to control the liquid crystal panel <NUM> and the plurality of LED bars <NUM> to display an image.

Hereinafter, the plurality of LED bars <NUM> used in the backlight device <NUM> according to an embodiment will be described in detail with reference to <FIG>, <FIG>, and <FIG>. The plurality of LED bars <NUM> are formed in the same structure; therefore, only one LED bar <NUM> will be described below for brevity of description.

<FIG> is a partial cross-sectional view illustrating an example of an LED bar used in a direct type backlight device according to an embodiment of the invention.

Referring to <FIG>, <FIG>, and <FIG>, the LED bar <NUM> includes a bar-shaped printed circuit board <NUM>, and a plurality of light emitting diodes (LEDs) <NUM> disposed on an upper surface of the printed circuit board <NUM>.

The printed circuit board <NUM> is formed in a bar shape, e.g., a rectangular flat plate having a narrow width and a long length. On the upper surface of the printed circuit board <NUM>, the plurality of LEDs <NUM> are disposed at regular intervals. Also, a power line for supplying power to the plurality of LEDs <NUM> may be formed in the printed circuit board <NUM>.

The plurality of LEDs <NUM> are configured to generate light, and disposed at regular intervals on the upper surface of the printed circuit board <NUM>. Further, the plurality of LEDs <NUM> are arranged in a straight line on the upper surface of the printed circuit board <NUM>. The light generated from the plurality of LEDs <NUM> moves toward the liquid crystal panel <NUM> through the diffusion plate <NUM>. The plurality of LEDs <NUM> may be disposed on the printed circuit board <NUM> by using surface mounting technology. The plurality of LEDs <NUM> are the same as or similar to general LEDs; therefore, a detailed description thereof is omitted.

The upper surface of the printed circuit board <NUM> is provided with a reflective member <NUM> capable of reflecting a part of the light emitted from the plurality of LEDs <NUM> and the light emitted from the lower surface of the diffusion plate <NUM>. The reflective member <NUM> is provided on a portion of the upper surface of the printed circuit board <NUM> where the plurality of LEDs <NUM> are not disposed. Accordingly, the reflective member <NUM> is disposed to cover a majority of or nearly all of the upper surface of the printed circuit board <NUM> except for portions where the plurality of LEDs <NUM> are disposed.

The reflective member <NUM> is formed such that a reflectance of the reflective member <NUM> is a certain degree (e.g., <NUM>%) or more of the reflectance of the reflective sheet <NUM>. To this end, the reflective member <NUM> is formed in a photo solder resist (PSR) layer having a high reflectance. In other words, the PSR layer is formed on the upper surface of the printed circuit board <NUM> as the reflective member <NUM>. In the following description, the reflectance may include specular reflectance and diffuse reflectance. When not specified, the reflectance means a lower reflectance of the specular reflectance and the diffuse reflectance.

A process of manufacturing the LED bar <NUM> includes a photo solder resist (PSR) process for coating an inactive area by applying PSR ink or PSR paint on the upper surface of the printed circuit board <NUM> and a reflow process for mounting the plurality of LEDs <NUM> on the upper surface of the printed circuit board <NUM> to which the PSR ink or the PSR paint is applied.

In the PSR process, a permanent ink is coated on the upper surface of the printed circuit board <NUM> to protect circuits formed on the upper surface of the printed circuit board <NUM> and to prevent the occurrence of a solder bridge phenomenon between the circuits in the next process.

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

The pretreatment operation is a process of removing an oxide film, oil, and the like which adversely affects an adhesion between a surface (e.g., an upper surface) of the printed circuit board <NUM> and the PSR ink and a process of providing roughness to a surface of a copper foil that form the circuits. Accordingly, the adhesion between the PSR ink and the copper foil in the printing operation may be improved.

The printing operation is a process of protecting the circuits of the printed circuit board <NUM> by applying the PSR ink to the surface of the printed circuit board <NUM> on which the circuits are formed. The printing operation may include 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 <NUM>.

The PSR exposure operation is a process of selectively photocuring the PSR ink coated on the upper surface of the printed circuit board <NUM> as an area to act as a resist and an area to expose the copper foil by using a patterned exposure mask and ultraviolet.

The PSR development operation is a process of exposing the copper foil by removing a portion of the PSR ink of the printed circuit board <NUM> that is not cured because the portion of the PSR ink does not receive ultraviolet rays with a developing solution after exposure.

The drying operation is a process of completely curing the PSR ink by applying hot air to the printed circuit board <NUM> for a period of time after the PSR development operation is completed.

When the PSR process as described above is completed, the upper surface of the printed circuit board <NUM> is in a state in which the copper foil is exposed only in a plurality of portions where the plurality of LEDs <NUM> are to be disposed, and the PSR layer <NUM> having a high reflectance is formed on the remaining portions.

After the PSR process is completed, the plurality of LEDs <NUM> are mounted on the printed circuit board <NUM>. For example, the plurality of LEDs <NUM> may be mounted on the plurality of exposed portions of the copper foil of the printed circuit board <NUM> using the reflow process.

In detail, the reflow process may include a printing process, a mounting process, and a reflow soldering process.

In the printing process, a solder paste is applied to the portions of the printed circuit board <NUM> where the copper foil is exposed.

The mounting process is performed after the printing process is completed. In the mounting process, the plurality of LEDs <NUM> are placed on the portions of the printed circuit board <NUM> where the copper foil is exposed, that is, the portions where the solder paste is applied by using a surface mounting technology (SMT) machine.

Thereafter, the reflow soldering process is performed. In the reflow soldering process, when heat is applied by using a reflow soldering machine, the plurality of LEDs <NUM> are fixed to the printed circuit board <NUM> while the solder paste melts. The reflow soldering process may be performed two or more times as needed.

The LED bar <NUM> used in the backlight device <NUM> according to the embodiment of the disclosure may be manufactured through the PSR process and the reflow process as described above.

In an embodiment of the invention, in order to form the PSR layer <NUM> having a high reflectance in the PSR process, a PSR ink having a high reflectance is used or in an embodiment useful for understanding the invention a PSR paint having a high reflectance may be used.

In order to increase the reflectance of the PSR layer <NUM>, a PSR ink having a general reflectance, for example, a PSR ink having a reflectance of about <NUM>% to about <NUM>%, is applied twice or more to form the PSR layer <NUM>. <FIG> shows a case where the PSR layer <NUM> is formed by applying the PSR ink twice. When the PSR layer <NUM> is formed by applying the PSR ink twice, the thickness of the PSR layer <NUM> is approximately doubled, and the reflectance of the PSR layer <NUM> may be increased.

As another example, the reflectance of the PSR layer <NUM> may be improved by surface-treating the upper surface of the PSR layer <NUM> including a PSR ink having a general reflectance.

On the other hand, the LED bar <NUM> (see <FIG>) included in the general direct type backlight device <NUM> has a reflectance (e.g., diffuse reflectance, specular component excluded (SCE)) of the upper surface of the printed circuit board <NUM> of about <NUM>% to about <NUM>%. On the other hand, the reflectance (e.g., diffuse reflectance) of the reflective sheet <NUM> is about <NUM>%.

Therefore, when the LED bar <NUM> of the general direct type backlight device is disposed on the reflective sheet <NUM>, the difference in luminance appears on a screen formed by the liquid crystal panel due to the difference between the reflectance of the upper surface of the printed circuit board <NUM> and the reflectance of the reflective sheet <NUM>.

For example, a dark horizontal line corresponding to the LED bar <NUM> in the related art may appear on the liquid crystal panel. In other words, when the LED bar <NUM> in the related art is used, the LED bar <NUM> may be recognized or visible through the liquid crystal panel. In other words, there is a problem that the user may recognize the LED bar <NUM> through the liquid crystal panel.

In order to solve this problem, according to embodiments of the disclosure, the PSR layer <NUM> is formed on the upper surface of the printed circuit board <NUM> and the reflectance of the PSR layer <NUM> of the printed circuit board <NUM> of the LED bars <NUM> is about <NUM>% of the reflectance of the reflective sheet <NUM>. In other words, when the reflectance of the reflective sheet <NUM> is <NUM>%, the PSR layer <NUM> is formed to have the reflectance of <NUM>% or more. For example, when the reflectance of the reflective sheet <NUM> is <NUM>%, the PSR layer <NUM> is formed to have the reflectance of about <NUM>% or more.

In the above, the reflectance of the PSR layer <NUM> is described as about <NUM>% of the reflectance of the reflective sheet <NUM>. A ratio of the reflectance of the PSR layer <NUM> to the reflectance of the reflective sheet <NUM> may be determined as appropriate depending on an embodiment. Hereinafter, for illustrative purposes, an example in which the reflectance of the reflective sheet <NUM> is <NUM>% and the PSR layer <NUM> is formed to have the reflectance of about <NUM>% or more is described.

Because the upper surface of the PSR layer <NUM> is positioned above the upper surface of the reflective sheet <NUM> by the thickness of the printed circuit board <NUM>, when the reflectance of the PSR layer <NUM> is about <NUM>% or more of the reflectance of the reflective sheet <NUM>, the LED bars <NUM> are not viewable through the liquid crystal panel <NUM>.

As described above, because the printed circuit board <NUM> in which the plurality of LEDs <NUM> are disposed passes the reflow soldering process at least one time during the manufacturing process of the LED bar <NUM>, the reflectance of the PSR layer <NUM> formed on the printed circuit board <NUM> is changed.

Therefore, a PSR ink that allows the reflectance of the PSR layer <NUM> of the printed circuit board <NUM> to be <NUM>% or more of the reflectance of the reflective sheet <NUM> after the reflow soldering process is completed is used. In other words, the PSR layer <NUM> is formed by using a PSR ink that allows the reflectance of the PSR layer <NUM> to be about <NUM>% or more.

On the other hand, when the printed circuit board <NUM> performs the reflow soldering process twice to form the LED bar <NUM>, the reflectance of the PSR layer <NUM> needs to be <NUM>% or more of the reflectance of the reflective sheet <NUM> after the reflow soldering process is completed twice. In other words, a PSR ink that allows the reflectance of the PSR layer <NUM> of the printed circuit board <NUM> to be about <NUM>% or more after the reflow soldering process is completed twice is used.

Alternatively, according to the claimed invention, the PSR layer <NUM> is formed by applying a PSR ink having a general reflectance to the printed circuit board <NUM> two or more times, such that the reflectance of the PSR layer <NUM> is about <NUM>% or more.

For example, referring to <FIG>, the PSR ink having a general reflectance is applied to the upper surface of the printed circuit board <NUM> and dried to form a lower PSR layer 35a having a thickness of approximately <NUM> to <NUM>. Subsequently, the same PSR ink is applied to the lower PSR layer 35a and dried to form an upper PSR layer 35b. Thus, a PSR layer <NUM> is formed to include the lower PSR layer 35a and the upper PSR layer 35b and to have a thickness of about <NUM> to about <NUM>. Thus, the reflectance of the upper surface of the PSR layer <NUM>, that is, the upper surface of the upper PSR layer 35b is improved, so that the reflectance of the PSR layer <NUM> of the printed circuit board <NUM> after performing the reflow process is <NUM>% or more.

On the other hand, when the printed circuit board <NUM> performs the reflow soldering process twice to form the LED bar <NUM>, after the reflow soldering process is completed twice, the reflectance of the PSR layer <NUM> including the lower PSR layer 35a and the upper PSR layer 35b is formed to be <NUM>% or more of the reflectance of the reflective sheet <NUM>.

Table <NUM> below shows the change in reflectance of the PSR layer <NUM> according to the reflow soldering process.

In Table <NUM>, "Reference" in a column of the reflow times indicates a reflectance of the PSR layer <NUM> formed on the printed circuit board <NUM> before performing the reflow soldering process. "Once" indicates that the reflow soldering process is performed once on the printed circuit board <NUM> on which the PSR layer <NUM> is formed, and "Twice" indicates that the reflow soldering process is performed twice on the printed circuit board <NUM> on which the PSR layer <NUM> is formed. Table <NUM> includes a specular component included (SCI) reflectance and a specular component excluded (SCE) reflectance of the PSR layer <NUM>. The SCI reflectance represents the specular reflectance of the PSR layer <NUM> and the SCE reflectance represents the diffuse reflectance of the PSR layer <NUM>.

As shown in Table <NUM> above, it can be seen that the reflectance of the PSR layer <NUM> of the printed circuit board <NUM> exceeds <NUM>% for both the specular reflectance (SCI) and the diffuse reflectance (SCE). In particular, it can be seen that even after performing the reflow soldering process twice, the SCI reflectance and the SCE reflectance of the PSR layer <NUM> exceed <NUM>%. Therefore, the reflectance of the LED bar <NUM> according to an embodiment having the PSR layer <NUM> as described above is also greater than <NUM>%.

Hereinafter, an LED bar according to another embodiment that is useful for understanding the invention will be described in detail with reference to <FIG>.

<FIG> is a partial cross-sectional view illustrating another example of an LED bar used in a direct type backlight device.

Referring to <FIG>, an LED bar <NUM>' may include a printed circuit board <NUM>, a plurality of LEDs <NUM>, and a reflective member <NUM>.

The printed circuit board <NUM> and the plurality of LEDs <NUM> may be the same as or similar to those of the above-described embodiment(s); therefore, detailed descriptions thereof are omitted.

The reflective member <NUM> may be formed as a reflective layer on a protective PSR layer <NUM> of the printed circuit board <NUM>. In the embodiment of <FIG>, the PSR layer <NUM> functions to reflect light, but in the embodiment of <FIG>, a separate reflective layer <NUM> may be formed on a protective PSR layer <NUM>. Therefore, the protective PSR layer <NUM> formed on the printed circuit board <NUM> does not need to have a high reflectance, unlike the above-described PSR layer <NUM>.

After the protective PSR layer <NUM> is formed on the printed circuit board <NUM>, the reflective layer <NUM> may be formed by using a reflective ink or a reflective paint different from the PSR ink or PSR paint forming the protective PSR layer <NUM>. For example, after forming the protective PSR layer <NUM> on the printed circuit board <NUM>, the reflective ink is applied to the upper surface of the protective PSR layer <NUM> with a predetermined thickness to form the reflective layer <NUM>.

The reflective layer <NUM> may be formed such that the reflectance of the reflective layer <NUM> is about <NUM>% of the reflectance of the reflective sheet <NUM>. In other words, when the reflectance of the reflective sheet <NUM> is <NUM>%, the reflective layer <NUM> is formed to have the reflectance of <NUM>% or more. For example, when the reflectance of the reflective sheet <NUM> is <NUM>%, the reflective layer <NUM> is formed to have the reflectance of <NUM>% or more.

As described above, because the printed circuit board <NUM> on which the plurality of LEDs <NUM> are disposed passes the reflow soldering process at least one time during the manufacturing process of the LED bar <NUM>', the reflectance of the reflective layer <NUM> formed on the printed circuit board <NUM> may be changed.

Therefore, the reflective layer <NUM> may be formed by using a reflective ink or a reflective paint that allows the reflectance of the reflective layer <NUM> of the printed circuit board <NUM> to be <NUM>% or more of the reflectance of the reflective sheet <NUM> after the reflow soldering process is completed. In other words, when the reflectance of the reflective sheet <NUM> is <NUM>%, the reflective layer <NUM> is formed using a reflective ink or a reflective paint that allows the reflectance of the reflective layer <NUM> to be about <NUM>% or more.

On the other hand, when the printed circuit board <NUM> performs the reflow soldering process twice to form the LED bar <NUM>, the reflectance of the reflective layer <NUM> needs to be <NUM>% or more of the reflectance of the reflective sheet <NUM> after the reflow soldering process is completed twice. In other words, when the reflectance of the reflective sheet <NUM> is <NUM>%, a reflective ink or a reflective paint that allows the reflectance of the reflective layer <NUM> to be about <NUM>% or more after the reflow soldering process is completed twice is used.

In the above description, the reflective ink or the reflective paint that forms the reflective layer <NUM> refers to an ink or a paint that has a different component from that of the PSR ink or the PSR paint and allows the reflective layer <NUM> to have a high reflectance when the reflective layer <NUM> is coated on the upper surface of the PSR layer <NUM> of the printed circuit board <NUM>.

Hereinafter, an LED bar according to another embodiment that is useful for understanding the invention will be described in detail with reference to <FIG> and <FIG>.

<FIG> is a partial cross-sectional view illustrating another example of an LED bar used in a direct type backlight device. <FIG> is a plan view illustrating a reflective cover disposed on the LED bar of <FIG>.

Referring to <FIG>, an LED bar <NUM>" may include a printed circuit board <NUM>, a plurality of LEDs <NUM>, and a reflective member <NUM>.

The printed circuit board <NUM> and the plurality of LEDs <NUM> are the same as or similar to those of the LED bar <NUM> of the above-described embodiment(s); therefore, detailed descriptions thereof are omitted.

The reflective member <NUM> may be formed as a reflective cover disposed on the protective PSR layer <NUM> of the printed circuit board <NUM>. In the embodiment of <FIG>, the PSR layer <NUM> of the printed circuit board <NUM> functions to reflect light, but in the embodiment of <FIG>, a separate reflective cover <NUM> is disposed on the protective PSR layer <NUM> to reflect light.

As illustrated in <FIG>, the reflective cover <NUM> is formed in a shape corresponding to the printed circuit board <NUM>, and includes a plurality of through holes <NUM> into which the plurality of LEDs <NUM> are inserted.

In detail, the reflective cover <NUM> includes a film of a rectangular shape having a narrow width and a long length, and the plurality of through holes <NUM> in which the plurality of LEDs <NUM> are inserted are formed in a straight line. For example, the reflective cover <NUM> is formed in the same size and shape as the printed circuit board <NUM>, and includes the plurality of through holes <NUM> corresponding to the plurality of LEDs <NUM> disposed on the printed circuit board <NUM>.

Therefore, when the reflective cover <NUM> is disposed on the upper surface of the printed circuit board <NUM>, the plurality of LEDs <NUM> protrude from the reflective cover <NUM> through the plurality of through holes <NUM>, and the upper surface of the printed circuit board <NUM> is covered by the reflective cover <NUM>, so that the upper surface of the printed circuit board <NUM> is not exposed to the outside.

The reflective cover <NUM> may include the same material as the reflective sheet <NUM> disposed on the lower chassis <NUM>. As another example, the reflective cover <NUM> may include a material having a reflectance of about <NUM>% or more of the reflectance of the reflective sheet <NUM> and having a different component from that the reflective sheet <NUM>.

The reflective cover <NUM> may be disposed on the upper surface of the printed circuit board <NUM> after the LED bar <NUM>" including components other than the reflective cover <NUM> is manufactured, and before the LED bar <NUM>" including the reflective cover <NUM> is disposed on the lower chassis <NUM>.

As another example, a plurality of openings in which the plurality of LED bars <NUM>" are disposed may be formed in the reflective sheet <NUM>. The plurality of openings are formed in sizes corresponding to the plurality of LED bars <NUM>". Accordingly, when the plurality of LED bars <NUM>" are disposed in the plurality of openings of the reflective sheet <NUM>, the printed circuit board <NUM> is positioned on the bottom portion <NUM> of the lower chassis <NUM>, and the bottom portion <NUM> of the lower chassis <NUM> on which the reflective sheet <NUM> is disposed is not exposed.

In this example, the above-described reflective cover <NUM> may be formed by using a rectangular piece of the reflective sheet <NUM> that is cut when forming the plurality of openings in the reflective sheet <NUM>. When the reflective cover <NUM> includes the portion cut from the reflective sheet <NUM> as described above, material cost may be reduced.

Hereinafter, a method of manufacturing a direct type backlight device according to an embodiment of the invention will be described with reference to <FIG>.

<FIG> is a flowchart illustrating a method of manufacturing a direct type backlight device.

To manufacture the direct type backlight device <NUM>, first, the lower chassis <NUM> and the reflective sheet <NUM> are prepared. A plurality of through holes corresponding to the plurality of LEDs <NUM> of the plurality of LED bars <NUM> are not formed in the reflective sheet <NUM>. Therefore, because a process of forming the plurality of through holes in the reflective sheet <NUM> is not necessary, the manufacturing cost of the reflective sheet <NUM> may be reduced.

Subsequently, the reflective sheet <NUM> is disposed on the upper surface of the bottom portion <NUM> of the lower chassis <NUM> (S10). The reflective sheet <NUM> may be fixed to the lower chassis <NUM> with an adhesive, a double-sided tape or the like. Alternatively, the reflective sheet <NUM> may be fixed to the lower chassis <NUM> by using the plurality of LED bars <NUM> without being fixed to the lower chassis <NUM> with an adhesive or a double-sided tape.

After the reflective sheet <NUM> is disposed on the lower chassis <NUM>, the plurality of LED bars <NUM> are disposed on the upper surface of the reflective sheet <NUM> (S20). The plurality of LED bars <NUM> are spaced apart from each other by a predetermined distance and disposed on the upper surface of the reflective sheet <NUM> in parallel with each other as illustrated in <FIG>.

The plurality of LED bars <NUM> may be fixed to the lower chassis <NUM> by using fastening members such as bolts and screws. In other words, the fastening member penetrates the reflective sheet <NUM> to fix the plurality of LED bars <NUM> to the lower chassis <NUM>.

As another example, the lower chassis <NUM> may be provided with a plurality of fixing parts capable of fixing the plurality of LED bars <NUM>, so that each of the plurality of LED bars <NUM> is coupled to each of the plurality of fixing parts in one time operation (e.g., one touch operation).

Finally, the diffusion plate <NUM> is disposed above the plurality of LED bars <NUM> (S30). The diffusion plate <NUM> may be supported by a plurality of support members provided on the lower chassis <NUM>. The plurality of support members may be disposed on the reflective sheet <NUM>. Alternatively, the plurality of support members may be disposed on the printed circuit boards <NUM> of the LED bars <NUM> provided on the reflective sheet <NUM>.

As described above, in the direct type backlight device <NUM> according to an embodiment, after disposing the reflective sheet <NUM> on the lower chassis <NUM>, the plurality of LED bars <NUM>, <NUM>' and/or <NUM>" are disposed on or over the reflective sheet <NUM>. Therefore, it is not necessary to form the through holes in the reflective sheet <NUM>.

Therefore, when assembling the direct type backlight device <NUM>, there is no operation of inserting the plurality of LEDs into the through holes of the reflective sheet <NUM>. Accordingly, the assembly of the direct type backlight device <NUM> may be simple.

Therefore, the productivity of the direct type backlight device according to an embodiment is improved compared to the related art direct type backlight device, and the manufacturing cost of the direct type backlight device and a display apparatus having the same may be reduced.

In the direct type backlight device according to an embodiment having the above-described structure, because the plurality of LED bars are disposed on or over the reflective sheet, there is no need for a process in which a plurality of LEDs are inserted into a plurality of through holes of the reflective sheet, as is required in the related art direct type backlight device. Therefore, because the assembly of the direct type backlight device is simple, the direct type backlight device according to an embodiment and a display apparatus having the same are improved in productivity and manufacturing cost.

Claim 1:
A direct type backlight device comprising:
a lower chassis (<NUM>);
a reflective sheet (<NUM>) disposed on a bottom portion (<NUM>') of the lower chassis (<NUM>); and
a plurality of light emitting diode (LED) bars (<NUM>') disposed on an upper surface of the reflective sheet (<NUM>),
wherein each LED bar of the plurality of LED bars (<NUM>') comprises:
a bar-shaped printed circuit board (<NUM>) disposed on the upper surface of the reflective sheet (<NUM>);
a plurality of LEDs (<NUM>) disposed on an upper surface of the printed circuit board (<NUM>); and
a reflective member (<NUM>) provided on the upper surface of the printed circuit board (<NUM>),
wherein the reflective member (<NUM>) comprises a photo solder resist (PSR) layer having a high reflectance, the PSR layer (<NUM>) formed by applying a PSR ink on the printed circuit board (<NUM>) twice,
wherein the PSR layer is formed to include a lower PSR layer (35a) , and an upper PSR layer (35b) and the PSR layer has a thickness of about <NUM> to about <NUM>,
wherein the plurality of LEDs (<NUM>) are fixed to the printed circuit board (<NUM>), on which the PSR layer (<NUM>) has been provided, via a reflow soldering process performed twice on the printed circuit board (<NUM>) and the plurality of LEDs (<NUM>),
wherein a reflectance of the PSR layer (<NUM>) reduces each time after the reflow soldering process is performed on the PSR layer (<NUM>), and
wherein the reflectance of the PSR layer (<NUM>), after the reflow soldering process has been performed twice, is at least <NUM>% of a reflectance of the reflective sheet (<NUM>) and is less than the reflectance of the reflective sheet (<NUM>).