Backlight module and optical plate thereof

A backlight module includes a light guide board, at least one light emitting unit, a plurality of first glues, and a first reflection sheet. The light guide board has a light entrance surface, a light exit surface, and at least one reflection surface. The reflection surface is connected to the light entrance surface and the light exit surface respectively. The light emitting unit is disposed at the light entrance surface of the light guide board. The plurality of first glues is alternatively disposed on the reflection surface in a from-sparse-to-dense manner. The first reflection sheet is disposed on the plurality of first glues such that the first reflection sheet can be fixed onto the reflection surface.

BACKGROUND

1. Technical Field

The present disclosure relates to a backlight module and an optical plate thereof, and more specifically, to a backlight module in which glues are alternately disposed between a reflection sheet and a reflection surface of a light guide board in a from-sparse-to-dense manner and an optical plate thereof.

2. Description of the Prior Art

Since liquid crystal molecules do not produce light themselves, a common method for driving an LCD to display images involves utilizing a backlight module to provide light with sufficient brightness and uniform distribution to the LCD. Therefore, a backlight module is one of the major components of an LCD.

A common disposal design of a light source in a backlight module involves disposing a light emitting diode device at a side of a light entrance side-surface of a light guide board. In this design, besides the light exit surface facing the display region of the liquid crystal display device, other light exit surfaces have reflection sheets stuck thereon for light reflection, so as to prevent light loss and increase efficiency of the backlight module in use of light.

However, since light emitted by a light emitting diode device has high directivity and an ear portion is usually formed on the reflection surface for fixing frame components of the backlight module (e.g. a bezel and a plastic frame), light leakage may occur due to reflection of light at a position of the reflection surface corresponding to a bent structure of the ear portion. Furthermore, the brightness of the light exit surface corresponding to a section of the reflection surface close to the light entrance surface could be greater than that corresponding to a section of the reflection surface away from the light entrance surface, so as to influence the image display quality of the liquid crystal display device.

SUMMARY

The embodiment of the present invention provides a backlight module including a light guide board, at least one light emitting unit, a plurality of first glues, and a first reflection sheet. The light guide board has alight entrance surface, alight exit surface, and at least one reflection surface, and the reflection surface is connected to the light entrance surface and the light exit surface respectively. The light emitting unit is disposed on the light entrance surface of the light guide board. The plurality of first glues is alternately disposed on the reflection surface in a from-sparse-to-dense manner. The first reflection sheet is disposed on the plurality of first glues such that the first reflection sheet can be fixed onto the reflection surface.

The embodiment of the present invention further provides an optical plate for a backlight module. The optical plate includes a light guide board, a plurality of first glues, and a first reflection sheet. The light guide board has a light entrance surface, a light exit surface, and a reflection surface connected to the light entrance surface. An area of the reflection surface is less than an area of the light exit surface. The plurality of first glues is alternately disposed on the reflection surface in a from-sparse-to-dense manner. The first reflection sheet is disposed on the plurality of first glues such that the first reflection sheet can be fixed onto the reflection surface.

DETAILED DESCRIPTION

Please refer toFIG. 1, which is a partial diagram of a backlight module10according to an embodiment of the present invention. As shown inFIG. 1, the backlight module10includes an optical plate12and at least one light emitting unit14(three shown inFIG. 1, but not limited thereto). The optical plate12includes alight guide board16, a plurality of first glues18, a plurality of second glues20, a first reflection sheet22, and a second reflection sheet24. The light guide board16has a light entrance surface28, a light exit surface30, and at least one reflection surface32(one shown inFIG. 1). An area of the reflection surface32is less than an area of the light exit surface30and the reflection surface32is connected to the light entrance surface28and the light exit surface30respectively. The reflection surface32has at least one first region34away from the light emitting unit14and at least one second region close to the light emitting unit14(one shown inFIG. 1respectively). The light emitting unit14is preferably an LED (Light Emitting Diode) and disposed on the light entrance surface28of the light guide board16. The light emitting unit14is used for emitting light to the light guide board16via the light entrance surface28.

More detailed description for the design of the first glue18is provided as follows. Please refer toFIG. 1andFIG. 2.FIG. 2is a partial diagram of the first glues18inFIG. 1being disposed on the first region34of the reflection surface32. In this embodiment, the first glue18is made of glue material with low absorbance less than 0.5. The aforesaid absorbance can be simply defined by the following equation.
Absorbance=1−(Reflectance+Transmittance)

In brief, when light is incident into an object, reflection, transmission, and absorption of light may occur. On the premise that amount of the incident light is equal to 1, light absorption efficiency of the object is higher if the absorbance approaches 1. On the contrary, if the absorbance is less than 0.5, it means that the object has higher reflectance and transmittance.

As shown inFIG. 1andFIG. 2, the plurality of first glues18made of glue material with low absorbance is substantially perpendicular to a bottom side33of the reflection surface32and is alternately disposed between the first reflection sheet22and the first region34from a position close to the light emitting unit (i.e. a position close to the light entrance surface28) to a position away from the light emitting unit14(i.e. a position away from the light entrance surface28) in a from-sparse-to-dense manner. Each first glue18has an identical width W, and an interval between two adjacent first glues18relatively close to the light emitting unit14is greater than an interval between two adjacent first glues18relatively away from the light emitting unit14(as shown inFIG. 2). In such a manner, as long as the sticking positions of the first glues18are adjusted appropriately, the purpose that this design is suitable to different sticking machines can be achieved. In this embodiment, the first glues18are pressure sensitive adhesive strips for alternately attaching between the first reflection sheet22and the first region34, so as to fix the first reflection sheet22onto the first region34, but not limited thereto. That is, the present invention can also adopt other conventional attaching design (e.g. the first glues18being alternately attached between the first reflection sheet22and the first region34by a screen coating process).

Accordingly, not only can the first glues18fix the first reflection sheet22to the first region34of the reflection surface32, but also provide a brightness enhancing function when light is incident into the first region34since the first glues18made of glue material with low absorbance can frustrate total reflection of light on the first region34to cause diffusion of light. In other words, via the aforesaid design in which the first glues18are alternately disposed on the first region34with gradually reducing intervals, the brightness compensation purpose can be achieved. In other words, the section having the sparsely-arranged first glues18on the first region34(i.e. the brighter section relatively close to the light entrance surface28) can have a relatively-lower brightness enhancing effect, and the section having the densely-arranged first glues18on the first region34(i.e. the darker section relatively away from the light entrance surface28) can have a relatively-higher brightness enhancing effect. Thus, when reflection of light occurs on the first region34, uneven brightness distribution occurring on the light exit surface30of the light guide board16corresponding to the first region34can be avoided by the optical plate12via the aforesaid brightness compensation design. To be noted, since the aforesaid design can provide a brightness enhancing function, the aforesaid design can be preferably applied to the darker section of the light exit surface30corresponding to the reflection surface32.

As for the design of the second glue20, its related description is provided as follows. In this embodiment, the second glue20is made of glue material with high absorbance greater than 0.5. As shown inFIG. 1, the plurality of second glues20is alternately disposed between the second reflection sheet24and the second region36from a position close to the light emitting unit14(i.e. a position close to the light entrance surface28) to a position away from the light emitting unit14(i.e. a position away from the light entrance surface28) in a from-dense-to-sparse manner. Each second glue20has an identical width, and an interval between two adjacent second glues20relatively close to the light emitting unit14is greater than an interval between two adjacent second glues20relatively away from the light emitting unit14. In such a manner, as long as the sticking positions of the second glues18are adjusted appropriately, the purpose that this design is suitable to different sticking machines can be achieved. In this embodiment, the second glues20are pressure sensitive adhesive strips for alternately attaching between the second reflection sheet24and the second region36, so as to fix the second reflection sheet24onto the second region36, but not limited thereto. That is, the present invention can also adopt other conventional attaching design (e.g. the second glues20being alternately attached between the second reflection sheet24and the second region36by a screen coating process).

Accordingly, not only can the second glue20fix the second reflection sheet24to the second region36of the reflection surface32, but also provide a brightness reducing function when light is incident into the second region36since the second glues20can frustrate total reflection of light on the second region36and absorb the incident light. In other words, via the aforesaid design in which the second glues20are alternately disposed on the second region36with gradually reducing intervals, the brightness compensation purpose can be achieved. That is, the section having the densely-arranged second glues20on the second region36(i.e. the brighter section relatively close to the light entrance surface28) can have a relatively-higher light absorption effect, and the section having the sparsely-arranged second glues20on the second region36(i.e. the darker section relatively away from the light entrance surface28) can have a relatively-lower light absorption effect. Thus, when reflection of light occurs on the second region36, uneven brightness distribution occurring on the light exit surface30of the light guide board16corresponding to the second region36can be avoided by the optical plate12via the aforesaid brightness compensation design. To be noted, since the aforesaid design can provide a brightness reducing function, the aforesaid design can be preferably applied to the brighter section of the light exit surface30corresponding to the reflection surface32.

In summary, the optical plate12utilizes the design in which the first glues18and the second glues20are respectively disposed on the first region34and the second region36in a from-sparse-to dense manner, to prevent uneven brightness distribution occurring on the light exit surface30of the light guide board16corresponding to the reflection surface32. Furthermore, not only can the embodiments of the present invention be performed directly by a conventional glue applying process, but also suitable to the slim light guide board16. In other words, the present invention of the embodiments can solve the problem that a dot patterning process, which is usually applied to a bottom surface of a light guide board, can not be performed on the excessively narrow reflection surface32of the slim light guide board16. In addition, via the design in which the first reflection sheet22and the second reflection sheet24are fixed to the side surface (i.e. the light reflection surface32) of the reflection surface32by the first glues18and the second glues20, the embodiments of the present invention can efficiently prevent light leakage toward the horizontal direction of the light guide board16.

In the embodiments of the present invention, the first region34and the second region36are not limited to have an identical length, meaning that the length of the first region34can also be different from the length of the second region36. Furthermore, in other embodiment, the first region34could be not connected to the second region36. For example, a connection section with no glue stuck thereon can be formed between the first region34and the second region36.

As for the derivative embodiments of changing the optical characteristics of the first glues18and the second glues20, the related description can be reasoned according to the aforementioned embodiment. In brief, if the first glues18are made of glue material with high absorbance instead, the first glues18can be alternately disposed between the first reflection sheet22and the first region34from a position close to the light emitting unit14(i.e. a position close to the light entrance surface28) to a position away from the light emitting unit14(i.e. a position away from the light entrance surface28) in a from-dense-to-sparse manner. On the other hand, if the second glues20are made of glue material with low absorbance instead, the second glues20can be alternately disposed between the second reflection sheet24and the second region36from a position close to the light emitting unit14(i.e. a position close to the light entrance surface28) to a position away from the light emitting unit14(i.e. a position away from the light entrance surface28) in a from-sparse-to-dense manner.

It should be mentioned that the first glues18could be obliquely disposed on the reflection surface32instead of being perpendicular to the bottom side33of the reflection surface32as shown inFIG. 2. For example, please refer toFIG. 3, which is a partial diagram of the first glues18being disposed on the first region34of the reflection surface32according to another embodiment of the present invention. In this embodiment, an inclined angle θ is formed between each first glues18and the bottom side33of the reflection surface32. Accordingly, this design can efficiently prevent regular bright fringes caused by the first glues18being perpendicular to the bottom side33according to the aforementioned embodiment. Furthermore, for preventing overlapping of two adjacent first glues18due to the excessive inclined angle θ, the inclined angle θ is preferably between 45° and 135°. In addition, the embodiments of the present invention can further adopt the design in which the first glues18are disposed on the first region34of the reflection surface32in a mutually-intersecting manner (as shown inFIG. 4). In such a manner, even if the aforesaid regular bright fringes still occur on the light exit surface30of the light guide board16when the first glues18are obliquely disposed on the reflection surface32, the present invention can further adopt this design to improve the aforesaid fringe problem.

Besides, the design for arrangement of the first glues18is not limited to the aforementioned embodiment. For example, please refer toFIG. 5, which is a partial diagram of the first glues18being disposed on the first region34of the reflection surface32according to another embodiment of the present invention. As shown inFIG. 5, the plurality of first glues18is alternately arranged on the first region34with identical intervals I, and a width of the first glue18relatively close to the light emitting unit14is less than a width of the first glue18relatively away from the light emitting unit14. Accordingly, the purpose that the first glues18are alternately disposed on the first region34in a from-sparse-to-dense manner can also be achieved (as shown inFIG. 5). In such a manner, arrangement of the first glues18can be changed easily by appropriately adjusting the width of each first glue18rather than additionally changing the sticking position of each first glue18, so as to make adjustment for arrangement of the first glues18more convenient.

Furthermore, in another embodiment, if the optical plate12utilizes the aforementioned screen coating process to dispose the first glues18between the first reflection sheet22and the first region34, the shape design of the first glues18can vary with the practical application of the optical plate12. For example, the first glue18can be strip-shaped, solid circle-shaped, solid square-shaped, solid polygon-shaped, hollow circle-shaped, hollow square-shaped, or solid polygon-shaped.

The aforesaid designs for arrangement of the first glues18can be also applied to the second glues20, and the related description can be reasoned according toFIGS. 3-5. For example, the second glues20could be alternately arranged on the second region36with identical intervals, and a width of the second glue20relatively close to the light emitting unit14is greater than a width of the second glue20relatively away from the light emitting unit14; otherwise, the second glues20could be obliquely disposed on the refection surface32or be disposed on the second region36in a mutually-intersecting manner.

To be noted, the embodiments of the present invention can also adopt the design in which only one single type of glue is disposed on the reflection surface32for simplifying the design of the optical plate12in disposal of glue. For example, if the brightness of the light exit surface30of the light guide board16is high at a position corresponding to the reflection surface32, the optical plate12can just utilize the second glues20made of glue material with high absorbance, to be disposed on the first region34from a position close to the light emitting unit14to a position away from the light emitting unit14in a from-dense-to-sparse manner and disposed on the second region36from a position away from the light emitting unit14to a position close to the light emitting unit14in a from-sparse-to-dense manner. In other words, there is only one type of glue with high absorbance disposed on the reflection surface32from a position away from the light entrance surface28to a position close to the light entrance surface28in a from-sparse-to-dense manner for achieving the light absorption purpose, so as to solve the aforesaid problem that the brightness of the light exit surface30is high at a position corresponding to the reflection surface32. In practical application, the second glues20made of glue material with high absorbance can also be alternately disposed over the entire area or on the partial area of the reflection surface32in a from-sparse-to-dense manner.

On the other hand, if the brightness of the light exit surface30of the light guide board16is low at the position corresponding to the reflection surface32, the optical plate12can just utilize the first glues18made of glue material with low absorbance, to be disposed on the first region34from a position close to the light emitting unit14to a position away from the light emitting unit14in a from-sparse-to-dense manner and disposed on the second region36from a position away from the light emitting unit14to a position close to the light emitting unit14in a from-dense-to-sparse manner. In other words, there is only one type of glue with low absorbance disposed on the reflection surface32from a position close to the light entrance surface28to a position away from the light entrance surface28in a from-sparse-to-dense manner for achieving the brightness enhancing purpose, so as to solve the aforesaid problem that the brightness of the light exit surface30is low at the position corresponding to the reflection surface32. Furthermore, since the first glues18made of glue material with low absorbance have higher reflectance and transmittance to cause reflection or transmission of light, meaning that light can be used repeatedly, this design may also increase efficiency of the optical plate12in use of light so as to make the optical plate12have a preferable brightness. In practical application, the first glues18made of glue material with low absorbance can also be alternately disposed over the entire area or on the partial area of the reflection surface32in a from-sparse-to-dense manner.

In addition, the embodiments of the present invention can also adopt the design in which two different types of glues are disposed on the same region of the reflection surface32. For example, if the first glue18is made of glue material with low absorbance and the second glue20is made of glue material with high absorbance, the optical plate12can utilize the first glues18to be disposed on a section of the first region34relatively away from the light emitting unit14in a from-sparse-to-dense manner (from a position close to the light emitting unit14to a position away from the light emitting unit14), and utilize the second glues20to be disposed on a section of the first region34relatively close to the light emitting unit14in a from-dense-to-sparse manner (from a position close to the light emitting unit14to a position away from the light emitting unit14). That is, there are plural sets of the first glues18and the second glues20alternately disposed on the reflection surface32. Since the light compensation range of the aforesaid design is twice as wide as that of the design in which only one single type of glue is disposed on one region of the reflection surface32, the aforesaid design is preferably applied to solve the problem that excessive brightness variation occurs on one region of the light exit surface30corresponding to the reflection surface32. In other words, the present invention can adopt the aforesaid design in which the glues with low absorbance the glues with high absorbance are respectively disposed on the darker section and the brighter section on the same region of the light exit surface to achieve the brightness compensation purpose. To be noted, in the present invention, the size (e.g. the length) of the first glue18could be equal to or different from that of the second glue20in the same region.

In the embodiments of the present invention, the structural design of the light guide board16is not limited to the aforesaid embodiments. For example, please refer toFIG. 6, which is a partial diagram of a backlight module10′ according to another embodiment of the present invention. Components mentioned in this embodiment and the aforementioned embodiment represent component with similar functions or structures, and the related description is omitted herein. The major difference between the backlight module10′ and the backlight module10is disposal of an ear portion38.

As shown inFIG. 6, the ear portion38protrudes from the reflection surface32. In this embodiment, the ear portion38is located between the first region34and the second region36, meaning that the first region34is located at a side of the ear portion38relatively away from the light emitting unit14and the second region36is located at a side of the ear portion38relatively close to the light emitting unit14. The ear portion38is used for assembling with frame components (e.g. a bezel or a plastic frame) in the backlight module10′ so as to fix the light guide board16in the backlight module10′. In this embodiment, the ear portion38can be, for example, a rectangle-shaped structure, and the optical plate12can further include a third reflection sheet26attached (e.g. utilizing a glue sticking method) to a side surface39of the ear portion38parallel to the reflection surface32for light reflection, so as to prevent light leakage occurring on the side surface39. The structural design of the ear portion38is not limited toFIG. 6, meaning that the ear portion38can be other common protruding structure, such as a trapezoid-shaped structure or a triangle-shaped structure.

As for the derivative designs of the first glues18and the second glues20in this embodiment, they can be reasoned according to the aforementioned embodiments andFIGS. 2-5, For example, as shown inFIG. 6, the plurality of first glues18could be alternately disposed between the first reflection sheet22and the first region34from a position close to the light emitting unit14(i.e. a position close to the ear portion38) to a position away from the light emitting unit14(i.e. a position away from the ear portion38) in a from-sparse-to-dense manner, so as to fix the first reflection sheet22onto the first region34of the reflection surface32.

Accordingly, the section having the sparsely-arranged first glues18on the first region34(i.e. the section relatively close to the light entrance surface28and close to the ear portion38) can have a relatively-lower brightness enhancing effect, and the section having the densely-arranged first glues18on the first region34(i.e. the section relatively away from the light entrance surface28and away from the ear portion38) can have a relatively-higher brightness enhancing effect. Thus, when reflection of light occurs on the first region34, not only can uneven brightness distribution occurring on the light exit surface30of the light guide board16corresponding to the first region34be avoided by the optical plate12via the aforesaid brightness compensation design, but also prevent light leakage caused by reflection of light occurring on the reflection surface32corresponding to the bent structure of the ear portion38.

On the other hand, the plurality of second glues20could be alternately disposed between the second reflection sheet24and the second region36from a position close to the light emitting unit14(i.e. a position away from the ear portion38) to a position away from the light emitting unit14(i.e. a position close to the ear portion38) in a from-dense-to-sparse manner, so as to fix the second reflection sheet24onto the second region36of the reflection surface32.

Accordingly, the section having the densely-arranged second glues20on the second region36(i.e. the section relatively close to the light entrance surface28and away from the ear portion38) can have a relatively-higher light absorption effect, and the section having the sparsely-arranged second glues20on the second region36(i.e. the section relatively away from the light entrance surface28and close to the ear portion38) can have a relatively-higher light absorption effect. Thus, when reflection of light occurs on the second region36, not only can uneven brightness distribution occurring on the light exit surface30of the light guide board16corresponding to the second region36be avoided by the optical plate12via the aforesaid brightness compensation design, but also prevent light leakage caused by reflection of light occurring on the reflection surface32corresponding to the bent structure of the ear portion38.

Since reflection of light may easily occur on the bent structure of the ear portion38inFIG. 6so as to cause excessive brightness variation at a position of the light exit surface30corresponding to the reflection surface32, this embodiment may preferably adopt the aforesaid design in which the glues with low absorbance and the glues with high absorbance are respectively disposed on the darker section and the brighter section on the same region of the light exit surface for the brightness compensation purpose.

Compared with the prior art, the present invention utilizes the design in which the glues are disposed between the reflection sheet and the reflection surface in a from-sparse-to-dense manner. In such a manner, not only can the present invention prevent light leakage caused by reflection of light occurring on the reflection surface corresponding to the bent structure of the ear portion, but also avoid uneven brightness distribution occurring on the light exit surface of the light guide board corresponding to the sections close to and away from the light entrance surface, so as to improve the image display quality of the liquid crystal display device.