KR101212145B1 - A back-light unit - Google Patents

A back-light unit Download PDF

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Publication number
KR101212145B1
KR101212145B1 KR1020050118873A KR20050118873A KR101212145B1 KR 101212145 B1 KR101212145 B1 KR 101212145B1 KR 1020050118873 A KR1020050118873 A KR 1020050118873A KR 20050118873 A KR20050118873 A KR 20050118873A KR 101212145 B1 KR101212145 B1 KR 101212145B1
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KR
South Korea
Prior art keywords
light
sheet
polarized light
light source
brightness
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Application number
KR1020050118873A
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Korean (ko)
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KR20070059703A (en
Inventor
이성근
김민섭
Original Assignee
엘지디스플레이 주식회사
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Priority to KR1020050118873A priority Critical patent/KR101212145B1/en
Publication of KR20070059703A publication Critical patent/KR20070059703A/en
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Publication of KR101212145B1 publication Critical patent/KR101212145B1/en

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Abstract

The present invention relates to a backlight unit capable of increasing the efficiency of light, comprising: at least one light source for emitting light; An optical sheet for condensing and diffusing light from the light source and having photoelasticity; And a brightness increasing sheet which increases the brightness of the light from the optical sheet and transmits the brightness to the display unit side.
Back light, LCD, Photoelastic, DBEF, Polarized

Description

Back light unit {A back-light unit}

1 is a view showing a conventional backlight unit

FIG. 2 illustrates a path of light passing through the optical sheet and the brightness increasing sheet of FIG. 1. FIG.

3 is a diagram illustrating a backlight unit according to a first embodiment of the present invention;

4 is a view for explaining a method of imparting photoelasticity to the optical sheet of FIG.

5 is a view showing a path of light passing through the optical sheet and the brightness increasing sheet of FIG.

6 illustrates a backlight unit according to a second embodiment of the present invention.

7 illustrates a backlight unit according to a third embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

301: bottom cover 302: optical sheet

302a: diffusion sheet 302b: first light collecting sheet

302c: second condensing sheet 303: luminance increasing sheet

304: liquid crystal panel 305: reflecting plate

333: lamp

The present invention relates to a backlight unit, and more particularly, to a backlight unit capable of increasing light efficiency.

In recent years, research on flat panel display devices has been actively conducted. Among them, liquid crystal display devices (LCDs), field emission display devices (FEDs), electro-luminescence display devices (ELDs), and PDPs (PDPs) Plasma Display Pannels).

Among them, LCD is the most used to replace the CRT (Cathode Ray Tube) for mobile image display because of the excellent image quality, light weight, thinness, and low power consumption, and mobile type such as notebook computer monitor. In addition, it is being developed in various ways such as a monitor of a television and a computer for receiving and displaying broadcast signals.

As described above, although various technical advances have been made in order for the liquid crystal display device to serve as a screen display device in various fields, the task of improving the image quality as the screen display device has many advantages and disadvantages.

Therefore, in order to use a liquid crystal display as a general screen display device in various parts, the key to development is how much high definition images such as high definition, high brightness and large area can be realized while maintaining the characteristics of light weight, thinness and low power consumption. It can be said.

Such a liquid crystal display device may be broadly divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel, wherein the liquid crystal panel includes a first and second substrates having spaces, and It consists of a liquid crystal layer injected between a 1st board | substrate and a 2nd board | substrate.

On the other hand, such a liquid crystal display device itself is non-luminescent, so a separate external light source for irradiating light is required.

In particular, in the case of a transmissive liquid crystal display, a separate dimming device that emits light and guides the back of the liquid crystal panel is necessary.

The back light includes an edge type method and a direct type method.

In the direct type, a light emitting lamp is disposed on a flat surface. Since the shape of the light emitting lamp appears on the liquid crystal panel, the gap between the light emitting lamp and the liquid crystal panel should be maintained, and light scattering means should be disposed for the uniform distribution of light quantity. Therefore, there is a limit to thinning.

In addition, as the liquid crystal panel becomes larger in area, the area of the light exit surface of the backlight is also increased. When the direct backlight is enlarged, the light exit surface is not flat unless the light scattering means secures sufficient thickness. For this reason, the thickness of the light scattering means must be sufficiently secured.

On the other hand, the edge type is to install a light emitting lamp on the outside and to distribute the light to the entire surface using a light guide plate, the light emitting lamp is installed on the side, there is a problem that the brightness is low because the light must pass through the light guide plate. In addition, high optical design and processing techniques for the light guide plate are required for uniform distribution of luminance.

Since the direct type and edge type have their disadvantages, the direct type type backlight is mainly used in the liquid crystal display where brightness is more important than the screen thickness. In an important liquid crystal display device, an edge type backlight is mainly used.

Hereinafter, a conventional backlight unit will be described in detail with reference to the accompanying drawings.

1 is a view showing a conventional backlight unit.

As shown in FIG. 1, the conventional backlight unit includes a plurality of lamps 111 that emit light, a bottom cover for receiving and supporting the lamps 111, and a cover bottom 101. A reflector plate 105 formed on a bottom surface, an optical sheet 102 positioned above the bottom cover to diffuse and condense the light from the lamps 111 and the light reflected from the reflector plate 105, and output the light; And a brightness increasing sheet 103 which increases the brightness of the light from the optical sheet 102 and provides it to the display portion side of the liquid crystal panel 104.

2 is a view showing a path of light passing through the optical sheet 102 and the brightness increasing sheet 103 of FIG. 1, and as shown in the drawing, the light emitted from the lamp 111 is S-polarized. And P polarized light.

The P-polarized light may pass through the brightness increasing sheet 103, but the S polarized light does not pass through the brightness increasing sheet 103 and is reflected. The reflected S-polarized light is broken into polarization components and separated into S-polarized light and P-polarized light. The separated S-polarized light and P-polarized light are reflected from the reflecting plate 105 to reach the brightness increasing sheet 103 again. Then, the P-polarized light passes through the brightness increasing sheet 103 and is provided to the display side of the liquid crystal panel 104, and the S polarized light is reflected from the brightness increasing sheet 103 and separated into S polarized light and P polarized light again. do.

That is, the conventional backlight unit uses the brightness increasing sheet 103 to increase the utilization efficiency of the light emitted from the light source.

However, while the S-polarized light and P-polarized light separated from the S-polarized light pass through the plurality of optical sheets 102, there is a problem that most of the S-polarized light and P-polarized light are absorbed by the optical sheet 102. Accordingly, the conventional backlight unit has a problem that the utilization efficiency of light decreases even though the brightness increasing sheet 103 is provided.

The present invention has been made in order to solve the above problems, an object of the present invention is to provide a back light unit having an optical sheet having a photoelasticity to increase the utilization efficiency of light.

A backlight unit according to the present invention for achieving the above object, at least one light source for emitting light; An optical sheet for condensing and diffusing light from the light source and having photoelasticity; And a brightness increasing sheet which increases the brightness of the light from the optical sheet and transmits the brightness to the display unit side.

Here, the brightness increasing sheet is characterized in that one of the Brightness Enhancement Film (BEF) and Dual Brightness Enhancement Film (DBEF).

A bottom cover for supporting and storing the light source; And a reflecting plate formed on a bottom surface of the bottom cover facing the light source.

The optical sheet includes a diffusion sheet for emitting light from the light source into light having an even luminance distribution; And first and second light collecting sheets for condensing light from the diffusion sheet in different directions to secure a viewing angle.

A light guide plate for changing a path of light from the light source; A lamp housing provided at one side of the light guide plate to surround the light source; And a reflection plate provided on the rear surface of the light guide plate to reflect the leaked light.

The optical sheet may include a diffusion sheet for emitting light passing through the light guide plate as light having an even luminance distribution; And first and second light collecting sheets for condensing light from the diffusion sheet in different directions to secure a viewing angle.

The light source is characterized in that provided on one side of the light guide plate.

The light source may be provided on both sides of the light guide plate.

Hereinafter, a backlight unit according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating a backlight unit according to a first embodiment of the present invention.

The backlight unit according to the first embodiment of the present invention includes a plurality of lamps 333 for emitting light, a bottom cover 301 for receiving and supporting the lamps 333, and an inner surface of the bottom cover. An optical sheet 302 formed on the reflecting plate 305 formed on the bottom cover 301 and having photoelasticity and a brightness increasing sheet provided on the optical sheet 302. 303.

Here, the components listed above will be described in more detail as follows.

The lamp 333 mainly uses a cold cathode fluorescent lamp 333. The lamp 333 is turned on at the driving voltage of the lamp 333 from an inverter (not shown) and irradiates light toward the optical sheet 302.

The brightness increasing sheet 303 has a characteristic of passing almost any polarization of the vertical polarization (P polarization) and horizontal polarization (S polarization), but substantially reflects the other polarization of the linear reflection type polarizing material, For example, Brightness Enhancement Film (BEF) or Dual Brightness Enhancement Film (DBEF) may be used.

The optical sheet 302 condenses the light from the light source into light having a uniform luminance distribution and condenses the light passing through the diffusion sheet 302a in different directions to secure a viewing angle. First and second light collecting sheets 302b and 302c.

Here, the diffusion sheet 302a, the first light collecting sheet 302b, and the second light collecting sheet 302c have photoelasticity.

The photoelasticity refers to a phenomenon in which the elastic body deforms due to external force and causes birefringence. The optical sheet 302 having the photoelasticity passes P-polarized light as it is, and separates S-polarized light into S-polarized light and P-polarized light.

4 is a view for explaining a method of imparting photoelasticity to the optical sheet 302 of FIG. 3. As shown in the drawing, the optical sheet 302 is stretched in the X-axis and Y-axis directions. Photoelasticity can be provided to the sheet 302.

In this case, the larger the size difference between the tensile force applied in the X-axis direction and the tensile force applied in the Y-axis direction, the more the photoelasticity increases. That is, the larger the difference between the peripheral mold force in the X-axis direction and the peripheral mold force in the Y-axis direction, the more the photoelasticity increases.

In the backlight unit according to the first embodiment of the present invention configured as described above, the path of the light passing through the optical sheet 302 and the brightness increasing sheet 303 will be described in detail as follows.

5 is a view illustrating a path of light passing through the optical sheet and the brightness increasing sheet of FIG. 3.

First, light emitted from the lamp 333 is composed of S-polarized light and P-polarized light, and the P-polarized light passes through the diffusion sheet 302a, the first light collecting sheet 302b, and the second light collecting sheet 302c in order. Diffused and condensed, the diffused and condensed P-polarized light passes through the brightness increasing sheet 303 and is provided on the display portion side of the liquid crystal panel 304.

On the other hand, S-polarized light of the light emitted from the lamp 333 is separated into S-polarized light and P-polarized light while passing through the diffusion sheet 302a, the first light collecting sheet 302b, and the second light collecting sheet 302c. The separated P-polarized light passes through the luminance increasing sheet 303 and is provided on the display portion side of the liquid crystal panel 304. The separated S-polarized light is reflected without passing through the luminance increasing sheet 303, and the reflected S-polarized light is reflected by the second light collecting sheet 302c, the first light collecting sheet 302b, and the diffusion sheet 302a. Will pass in turn. At this time, the S-polarized light is separated into S-polarized light and P-polarized light again while passing through the second light collecting sheet 302c, the first light collecting sheet 302b, and the diffusion sheet 302a.

Thereafter, the separated S-polarized light and P-polarized light reach and reflect the reflection plate 305, and the reflected P-polarized light is diffused sheet 302a, first light collecting sheet 302b, second light collecting sheet 302c, and The luminance increasing sheet 303 is sequentially passed to the display unit side of the liquid crystal panel 304. On the other hand, the reflected S-polarized light is separated into S-polarized light and P-polarized light again while passing through the diffusion sheet 302a, the first light collecting sheet 302b, and the second light collecting sheet 302c. The separated P-polarized light passes through the brightness increasing sheet 303 and is provided to the display side of the liquid crystal panel 304. The separated S polarized light is reflected from the brightness increasing sheet 303 and is again reflected in the S-polarized light and P. Separated by polarized light.

As described above, the S-polarized light has more S-polarized light than the prior art through the diffusion sheet 302a having the photoelasticity, the first light collecting sheet 302b, and the second light collecting sheet 302c, and the brightness increasing sheet 303. It is separated by P polarization.

Accordingly, the backlight unit according to the first embodiment of the present invention having such a structure exhibits better light efficiency than the conventional backlight unit.

Hereinafter, a backlight unit according to a second embodiment of the present invention will be described.

6 is a diagram illustrating a backlight unit according to a second embodiment of the present invention.

In the backlight unit according to the second exemplary embodiment of the present invention, as shown in FIG. 6, a lamp 666 for generating light and a path of light emitted from the lamp 666 may be changed to convert the light into liquid crystal. The light guide plate 601 for guiding to the display portion side of the panel 604, the optical sheet 602 which diffuses and condenses the light from the light guide plate 601 and has photoelasticity, and the brightness of the light from the optical sheet 602. A luminance increasing sheet 603 provided on the display unit side of the liquid crystal panel 604 and provided below the light guide plate 601 to reflect the light leaked from the light guide plate 601 to the light guide plate 601 to provide light. It includes a lamp housing 607 to form a U-shape to have a reflecting plate 605 and an opening opening toward the light guide plate 601 to increase efficiency, and surround the lamps 666.

In detail, the lamp housing 607 is coupled to one side of the light guide plate 601 while surrounding the lamp 666, and blocks light emitted from the lamps 666 from leaking. That is, since the light emitted from the lamp 666 is emitted radially, the light that is not directly directed to the light guide plate 601 is reflected by the inner surface of the lamp housing 607 and transmitted to the light guide plate 601.

On the other hand, the optical sheet 602 is a diffusion sheet 602a for emitting the light passing through the light guide plate 601 as light having an even luminance distribution, and the light passing through the diffusion sheet 602a in different directions. And first and second light collecting sheets 602b and 602c for condensing to secure a viewing angle.

Here, the diffusion sheet 602a, the first light collecting sheet 602b, and the second light collecting sheet 602c have photoelasticity as described above.

In the backlight unit according to the second embodiment of the present invention having such a configuration, a path of light passing through the optical sheet 602 and the brightness increasing sheet 603 will be described in detail as follows.

First, light emitted from the lamp 666 is composed of S-polarized light and P-polarized light, and the P-polarized light is a light guide plate 601, a diffusion sheet 602a, a first light collecting sheet 602b, and a second light collecting sheet 602c. Diffused and condensed while passing through sequentially, and the diffused and condensed P-polarized light passes through the brightness increasing sheet 603 and is provided on the display portion side of the liquid crystal panel 604.

On the other hand, the S-polarized light of the light emitted from the lamp 666 passes through the light guide plate 601, the diffusion sheet 602a, the first light collecting sheet 602b, and the second light collecting sheet 602c, and the S polarized light and P polarized light. Separated by. The separated P-polarized light passes through the luminance increasing sheet 603 and is provided on the display portion side of the liquid crystal panel 604. The separated S-polarized light does not pass through the luminance increasing sheet 603 and is reflected, and the reflected S-polarized light is reflected by the second light collecting sheet 602c, the first light collecting sheet 602b, the diffusion sheet 602a, And the light guide plate 601 in order. At this time, the S-polarized light is separated into S-polarized light and P-polarized light again while passing through the second light collecting sheet 602c, the first light collecting sheet 602b, and the diffusion sheet 602a.

Thereafter, the separated S-polarized light and P-polarized light are reflected by reaching the reflecting plate 605 via the light guide plate 601, and the reflected P polarized light is reflected by the light guide plate 601, the diffusion sheet 602a, and the first light collecting sheet ( 602b), the second light collecting sheet 602c, and the luminance increasing sheet 603, in turn, are provided on the display portion side of the liquid crystal panel 604. On the other hand, the reflected S-polarized light is separated into S-polarized light and P-polarized light again while passing through the diffusion sheet 602a, the first light collecting sheet 602b, and the second light collecting sheet 602c via the light guide plate 601. . The separated P-polarized light passes through the brightness increasing sheet 603 and is provided to the display side of the liquid crystal panel 604. The separated S polarized light is reflected from the brightness increasing sheet 603 and is again reflected by the S-polarized light and P. Separated by polarized light.

As such, the S-polarized light has more S-polarized light than before through the photoelastic diffusion sheet 602a, the first light collecting sheet 602b, and the second light collecting sheet 602c, and the brightness increasing sheet 603. It is separated by P polarization.

Hereinafter, a backlight unit according to a third embodiment of the present invention will be described.

7 is a diagram illustrating a backlight unit according to a third embodiment of the present invention.

The backlight unit according to the third embodiment of the present invention is the same as that of the above-described second embodiment, except that the lamps 777a and 777b and the lamp housings are provided on both sides of the light guide plate 601. 707a and 707b are provided.

In the backlight unit according to the second embodiment of the present invention having such a configuration, the path of the light passing through the optical sheet 602 and the brightness increasing sheet 603 is the optical sheet 602 provided in it in the above-described second embodiment. ) And the path of light passing through the luminance increasing sheet 603, and thus description thereof will be omitted.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The backlight unit according to the present invention as described above has the following effects.

The backlight unit which concerns on this invention is equipped with the optical sheet which has photoelasticity. Therefore, S-polarized light passing through the optical sheet is separated into more S-polarized light and P-polarized light than before. Accordingly, the backlight unit of the present invention can maximize the utilization efficiency of light.

Claims (8)

  1. At least one light source for emitting light;
    An optical sheet for condensing and diffusing light from the light source and having photoelasticity; And
    A brightness increasing sheet which increases the brightness of the light from the optical sheet and transmits the brightness to the display portion side;
    The light emitted from the light source is composed of P polarized light and S polarized light;
    P-polarized light emitted from the light source is sequentially passed through the optical sheet and the luminance increasing sheet to the display portion side;
    S-polarized light emitted from the light source is separated into P-polarized light and S-polarized light while passing through the optical sheet;
    P-polarized light separated while passing through the optical sheet is transmitted to the display portion side through the brightness increasing sheet;
    And the S-polarized light separated while passing through the optical sheet is separated into P-polarized light and S-polarized light while being reflected by the brightness increasing sheet.
  2. The method of claim 1,
    The brightness increasing sheet is a backlight unit, characterized in that one of the Brightness Enhancement Film (BEF) and Dual Brightness Enhancement Film (DBEF).
  3. The method of claim 1,
    A bottom cover for supporting and storing the light source; And
    And a reflector formed on a bottom surface of the bottom cover facing the light source.
  4. The method of claim 3, wherein
    The optical sheet,
    A diffusion sheet for emitting light from the light source into light having an even luminance distribution; And,
    First and second light collecting sheets for condensing light from the diffusion sheet in different directions to secure a viewing angle;
    And said diffusion sheet, first condensing sheet and second condensing sheet all have photoelasticity.
  5. The method of claim 1,
    A light guide plate for changing a path of light from the light source;
    A lamp housing provided at one side of the light guide plate to surround the light source; And
    And a reflector provided on a rear surface of the light guide plate to reflect the leaked light.
  6. 6. The method of claim 5,
    The optical sheet,
    A diffusion sheet for emitting the light passing through the light guide plate into light having an even luminance distribution; And,
    First and second light collecting sheets for condensing light from the diffusion sheet in different directions to secure a viewing angle;
    And said diffusion sheet, first condensing sheet and second condensing sheet all have photoelasticity.
  7. 6. The method of claim 5,
    The light source is a backlight unit, characterized in that provided on one side of the light guide plate.
  8. 6. The method of claim 5,
    The light source is a backlight unit, characterized in that provided on both sides of the light guide plate.
KR1020050118873A 2005-12-07 2005-12-07 A back-light unit KR101212145B1 (en)

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KR1020050118873A KR101212145B1 (en) 2005-12-07 2005-12-07 A back-light unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020050118873A KR101212145B1 (en) 2005-12-07 2005-12-07 A back-light unit

Publications (2)

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KR20070059703A KR20070059703A (en) 2007-06-12
KR101212145B1 true KR101212145B1 (en) 2012-12-14

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004272256A (en) * 2003-03-05 2004-09-30 Samsung Electronics Co Ltd Optical sheet and liquid crystal display device using same

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004272256A (en) * 2003-03-05 2004-09-30 Samsung Electronics Co Ltd Optical sheet and liquid crystal display device using same

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