KR20220006747A - Ultra-thin Back light unit - Google Patents

Abstract

The present invention relates to an ultrathin backlight unit to efficiently output light with only two optical sheets. According to the present invention, the ultrathin backlight unit comprises: a light guide plate; a light source disposed on one side of the light guide plate; a first optical sheet module disposed on the upper part of the light guide plate; and a second optical sheet module disposed on the upper part of the first optical sheet module. The first optical sheet module includes a first base film of a sheet shape transmitting light and a first light connection part formed on the first base film in which first unit light collection bodies is continuously and repeatedly arranged in a direction in which light is emitted from the light source, wherein the first unit light collection body includes a first light-incident surface inclined to face the light source and a first light-facing surface in contact with the upper part of the first light-incident surface and inclined in an opposite direction to the first light-incident surface. The second optical sheet module includes a second light collection part of a sheet shape transmitted to transmit light and a second light collection part formed on the second base film and in which quadrangular pyramidic second unit light collection bodies are arranged, wherein the second unit light collection body includes a second light-incident surface facing the light source, a second light-facing surface formed at a position facing the second light-incident surface corresponding to the second light incident surface, and two side light-emitting surfaces configured to connect the second light-incident surface and the second light-facing surfaces to form a quadrangular pyramid.

Description

Ultra-thin Back light unit

The present invention relates to a backlight unit, and more particularly, to an ultra-thin backlight unit composed of only two optical sheets.

In recent years, the use of flat panel display panels has been greatly expanded, and a representative one of them is a liquid crystal display (LCD).

In general, the liquid crystal display device (LCD) requires a backlight unit that provides uniform light to the entire screen, unlike the conventional cathode-ray tube method (CRT).

The backlight unit includes a lamp that is a linear light source, a reflector that reflects the light of the lamp, and an optical sheet module, and converts the light from the lamp into a surface light source to project the light onto the screen. In this case, the light source is disposed adjacent to the side of the light guide unit to transmit the light penetrating into the reflection unit upward, and the transmitted light is diffused and condensed by the optical sheet module.

In the conventional backlight unit, as shown in FIGS. 1 and 2 , the light emitted from the light source 1 is transmitted upward through the light guide plate 2 , and the light transmitted to the top is diffused through the diffusion sheet 3 . After that, it is transferred to the liquid crystal panel through a plurality of optical sheets 4 and 4 ′ provided on the upper portion. In some cases, an additional diffusion sheet 3' may be further provided on the light collecting sheets 4 and 4'.

Such a conventional optical sheet module is configured to change a point light source of a lamp to a surface light source by laminating a plurality of diffusing and condensing sheets.

However, the recently developed display panel is gradually getting thinner, and accordingly, the thickness of the backlight module itself is also required to be thin.

As an example of such research, referring to Korean Patent Publication No. 2011-0076373, a light collecting sheet is formed to have a separate bead without a separate diffusion sheet, so that the light transmitted from the lower side is diffused.

However, in this case, there is a problem in that the luminance is not uniform because it is difficult to sufficiently diffuse the light only with the beads included in the light collecting sheet.

That is, when the diffusion sheet is simply removed to reduce the thickness of the optical sheet module, the luminance is not uniform, which causes a reliability problem and a problem in that the viewing angle is narrowed due to insufficient diffusion.

Therefore, it is necessary to develop a structure capable of making the backlight thinner and at the same time sufficiently supplementing the luminance and viewing angle.

The present invention is to solve the problems of the prior art, and to provide an ultra-thin backlight unit composed of only two optical sheets without a separate diffusion sheet.

The object of the present invention is not limited thereto, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

The ultra-thin backlight unit for achieving the object of the present invention as described above includes a light guide plate, a light source provided on one side of the light guide plate, a first optical sheet module provided on the light guide plate, and a first optical sheet module provided on the first optical sheet module It is composed of two optical sheet modules, wherein the first optical sheet module is formed on a first base film in the form of a sheet that transmits light and the first base film, and faces the light source and is inclined to face the light source. A first light collecting unit in which a first unit light collecting body, which is in contact with an upper portion of the first light incident surface, and is composed of a first light receiving surface inclined in the opposite direction to the first light incident surface, is continuously and repeatedly arranged in a direction in which light is emitted from the light source The second optical sheet module includes a second base film in the form of a sheet that transmits light and a second light collecting part in which a second unit light collecting body in the shape of a quadrangular pyramid formed on the second base film is arranged, The two-unit light collector includes a second light incident surface facing the light source, a second light incident surface opposite the second light incident surface and a second light incident surface configured at a position facing the second light incident surface, and the second light incident surface and the second light incident surface It may be composed of two photometric surfaces configured to connect to form a quadrangular pyramid.

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

First, there is an advantage in that the thickness of the backlight unit is very thin by configuring the backlight unit only with two optical sheets.

Second, by configuring one optical sheet as a unit concentrator in the shape of a quadrangular pyramid, it is possible to control light incident from a plurality of directions to an emission angle within a desired range.

Through this, it is possible to configure a backlight unit that effectively outputs light without a decrease in luminance using only two optical sheets.

Third, partial light control is possible.

In the ultra-thin backlight unit according to the present invention, different light control is possible according to the position of the optical sheet module by differently forming the shape of the quadrangular pyramid of the unit concentrator according to the position. Through this, effective light output is possible by controlling the light emission angles differently from the corners and the center.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is an exploded perspective view showing a backlight unit equipped with a conventional optical sheet module.
Figure 2 is an exploded perspective view showing a conventional backlight unit equipped with an optical sheet module.
3 is an exploded perspective view showing a backlight unit provided with an optical sheet module according to the present invention.
4 is an enlarged view of a backlight unit and a second optical sheet module according to the present invention.
5 is a cross-sectional view and a graph illustrating a light emission angle of a backlight unit according to the present invention.

An embodiment will be described with reference to the accompanying drawings. In describing the present embodiment, the same names and the same reference numerals are used for the same components, and an additional description thereof will be omitted.

In addition, in describing the embodiment of the present invention, the same names and reference numerals are used for components having the same function, and it is substantially not completely the same as in the prior art.

In addition, terms used in the embodiments of the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In addition, in the embodiments of the present invention, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one It should be understood that it does not preclude the possibility of the presence or addition of or more other features or numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 3 to 5 .

3 is an exploded perspective view illustrating an ultra-thin backlight unit according to the present invention.

Hereinafter, a backlight unit according to the present invention will be described in detail with reference to FIG. 3 .

A liquid crystal display device must be provided with a backlight unit (BLU: Back Light Unit) that provides light to the liquid crystal panel. The backlight unit according to the present invention is largely composed of a light source 100 , a light guide plate 200 , a first optical sheet module 300 , and a second optical sheet module 400 .

The light source 100 is generally composed of a light emitting body that emits light and emits light from one side of the light guide plate 200, and the emitted light is reflected by the light guide plate 200 to the first optical sheet module ( 300) direction.

And the first optical sheet module 300 condenses the light emitted from the light source 100 and transmits it in the direction of the second optical sheet module 400 .

Here, the first optical sheet module 300 is formed in the form of a triangular prism sheet protruding in one direction, reflects the transmitted light and refracts it upward.

In addition, the second optical sheet module 400 is formed in the form of a prism sheet in which a plurality of quadrangular pyramids protrude, and additionally refracts the light transmitted from the first optical sheet module 300 to transmit it upward.

The backlight unit according to the present invention as described above has a luminance even without a separate diffusion layer due to the configuration of the first optical sheet module 300 in the shape of a triangular prism and the second optical sheet module 400 having the protrusion in the shape of a quadrangular pyramid. It can spread the light evenly without degradation of

Referring to FIG. 4 in more detail with respect to the first optical sheet module 300, the first optical sheet module 300 largely includes a first base film 310 and a first light collecting part 320, and , the first base film 310 is formed of a flat film that transmits light.

Specifically, as for the first base film 310 according to the present invention, a light-transmitting film that can easily transmit light transmitted from the bottom is generally used, and the upper surface of the first base film 310 refracts light. The first light collecting part 320 for condensing light is formed so as to be integrated with the first base film 310 .

Here, the first light collecting part 320 is a pattern formed by a plurality of first unit light collecting bodies 320a for refracting light transmitted from the lower part, and the first unit collecting body 320a is transversed toward the upper part. The area decreases and is continuously repeated and arranged along the upper surface of the first base film 310 .

In addition, the first light collecting unit 320 condenses and transmits the light transmitted through the light guide plate 200 in an upward direction. At this time, the first base film 310 simply transmits the light and serves to transmit it upward.

Specifically, the first light collecting part 320 is composed of a plurality of first light collecting units 320a continuously formed on the upper portion of the first base film 310 , and the first unit collecting units 320a are A first light incident surface 322 facing toward the light source 100 and a first light incident surface 324 facing the first light incident surface 322 and positioned in the opposite direction of the first light incident surface 322 includes

The first light incident surface 322 is formed to face the light source 100 along a lateral direction in the first unit light collecting body 320a.

At this time, the first unit light collecting body 320a is formed in the form of a prism protruding upward on the first base film 310 as shown in FIG. 4 , and the first light incident surface 322 is described later. It has an inclination in an upward direction together with the first light facing surface 324, and is formed so as to be in contact with the uppermost part.

In the present embodiment, the first light collecting unit 320 is provided with a plurality of first unit light collecting bodies 320a on the first base film 310 as shown, and the light source ( 100) in a direction away from it.

At this time, the lateral direction means a direction perpendicular to the vertical direction and the vertical direction away from the light source as shown in FIG. 4 , and the vertical direction is the first light collecting part 320 is stacked on the light guide plate 200 . means direction.

As described above, the first unit light collecting body 320a is formed to have a reduced cross-sectional area toward the top, and the first light incident surface 322 has an inclination and is disposed in a direction facing the light source 100 .

Here, the first light-facing surface 324 is disposed to have an inclination in the opposite direction to the above-described first light-incident surface 322 , and an uppermost portion is formed to meet the first light-incident surface 322 .

Of course, it is also possible that the first light incident surface 322 and the first light facing surface 324 are arranged parallel to the longitudinal direction according to the type and arrangement of the light source 100 .

Next, the second optical sheet module 400 disposed on the first optical sheet module 300 will be described in detail.

The second optical sheet module 400 largely includes a second base film 410 and a second light collecting part 420 , and the second base film 410 is formed of a flat film that transmits light.

Specifically, as the second base film 410 of the second optical sheet module 400 according to the present invention, a light-transmitting film that can easily transmit light transmitted from the bottom is generally used, and the second base film A second light collecting part 420 for refracting and condensing light is formed on the upper surface of the 410 to be integrated with the second base film 410 .

Here, the second light collecting part 420 is a pattern formed by a plurality of second unit collecting bodies 420a for refracting the light transmitted from the first optical sheet module 300, and the second unit collecting body ( 420a) is arranged along the upper surface of the second base film 410 while continuously repeating and decreasing in cross-sectional area toward the top.

In addition, the second light collecting unit 420 condenses and transmits the light transmitted through the first optical sheet module 300 in an upward direction. At this time, the second base film 410 simply transmits the light and serves to transmit it upward.

Specifically, the second light collecting part 420 is composed of the second unit light collecting body 420a which is continuously formed in plurality on the second base film 410, and the second unit light collecting body 420a. is configured in a quadrangular pyramid shape, the second light incident surface 421 facing the light source 100 and the second light incident surface 421 facing the second light incident surface 421 opposite to the second light incident surface 421 and a light-facing surface 422 . In addition, as shown in FIG. 4 , two light-facing surfaces 423a and 423b are included to form a quadrangular pyramid by connecting the second light-incident surface 421 and the second light-facing surface 422 .

The second unit light collecting body 420a is configured in the shape of a quadrangular pyramid, and preferably, the two opposing photometric surfaces 423a and 423b are symmetrically and identically formed, and the second light incident surface 421 and the second light receiving surface 421 The second light plane 422 is preferably formed in an isosceles triangle.

In addition, it is preferable that the equilateral length of the triangle forming the second light incident surface 421 is shorter than the equilateral length of the triangle forming the second light facing surface 422 .

Accordingly, the vertices where the four faces of the quadrangular pyramid-shaped second unit light collecting body 420a meet are disposed close to the light source 100 along the longitudinal direction with respect to the center of the quadrangle constituting the bottom surface of the quadrangular pyramid.

A plurality of second unit light collectors 420a in the shape of a quadrangular pyramid configured as described above are disposed in an area corresponding to the light guide plate 200 to constitute the second optical sheet module 400 . Meanwhile, the second unit light collecting body 420a is preferably arranged to share one side with the adjacent second unit light collecting bodies 420a.

The second optical sheet module 400 may change the shape of the second unit light collecting body 420a to change the refractive index of the light transmitted from the first optical sheet module 300 .

As described above, the quadrangular pyramid of the second unit light collecting body 420a of the second optical sheet module 400 has a second light incident surface 421 composed of an isosceles triangle and two light metering surfaces 423a and 423b composed of a triangle. and a second light-facing surface 422 composed of an isosceles triangle.

At this time, passing through the vertex C where the four faces of the quadrangular pyramid-shaped second unit light collecting body 420a meet, parallel to the base of the second light incident face 421, and perpendicular to the bottom surface of the second unit light collecting body 420a A triangle formed by the phosphor surface is referred to as a second light incident surface projection triangle 421'. In addition, passing through the vertex C where the four sides of the quadrangular pyramid-shaped second unit light collector 420a meet, parallel to the base of the photometric surfaces 423a and 423b, and perpendicular to the bottom surface of the second unit light collecting body 420a A triangle formed by the phosphor surface is referred to as a photometric projection triangle 423a'.

A quadrangular pyramid shape of the second unit light collecting body 420a may be defined using the second light incident surface projection triangle 421 ′ and the light side projection triangle 423a ′ defined as described above.

Specifically, among the apex angles B and height h of the second light incident surface projection triangle 421', and the base angles of the photometric surface projection triangle 423a', the first base angle A further away from the light source 100, a quadrangular pyramid It can be defined by the longitudinal length (a) and the transverse length (b) of the rectangular base constituting the .

In general, the amount of refraction that can be refracted by the first optical sheet module 300 configured in the form of a triangular prism sheet by the light emitted from the light source 100 located on one side is transmitted upward by the light guide plate 200 is in the display area. It is insufficient to generate sufficient luminance and light diffusion.

Accordingly, in the related art, a backlight unit is constructed by stacking a plurality of triangular prism sheets and a plurality of light diffusion sheets to increase luminance and perform optical calculation.

However, the present invention can effectively increase the refractive index of light passing through one triangular prism sheet using the quadrangular pyramid-shaped optical sheet module as described above, thereby minimizing the decrease in luminance and generating sufficient light diffusion at the same time. do it with

The quadrangular pyramid-shaped optical sheet module has the effect of refracting light incident from multiple directions onto the optical path within a predetermined area using four surfaces and emitting it, so that one triangular prism sheet and one quadrangular pyramid-shaped optical sheet The module alone can diffuse the light effectively without lowering the luminance and output it to the screen.

In addition, in the prior art, since a separate diffusion sheet must be additionally provided, the luminance is reduced. In the present invention, the light can be diffused using a quadrangular pyramid-shaped optical sheet without a separate diffusion sheet. there is

The second unit light collecting body 420a of the second optical sheet module 400 has been described as having the same shape, but since the characteristics of the emitted light are different depending on the position of the light guide plate, the quadrangular pyramid shape of the second unit light collecting body 420a In addition, it goes without saying that the configuration can be changed to various shapes depending on the position corresponding to the light guide plate.

A specific embodiment will be described with reference to FIG. 5 .

5( a ) shows a light source 100 , a light guide plate 200 , a first optical sheet module 300 on the light guide plate 200 , and a second optical sheet module 400 on the first optical sheet module 300 . ) represents a backlight unit composed of

At this time, in configuring the second unit light collecting body 420a of the second optical sheet module 400 having a quadrangular pyramid shape, the apex angle B of the second light incident surface projection triangle 421 ′ is 90°, and the second light incident surface The height h of the projection triangle 421' is 10 μm, the size of the first base angle A further away from the light source 100 among the base angles of the photometric plane projection triangle 423a' is 45°, the longitudinal direction of the base The length (a) and the transverse length (b) were each configured to be 20 μm. In addition, the refractive indices of the first optical sheet module and the second optical sheet module were set to 1.6.

5(b) shows a simulation result of the emission angle size of the backlight unit configured as described above. Here, the horizontal axis represents the refraction angle theta_i, and the vertical axis represents the refraction angle theta(Prism) of the first optical sheet module and the refraction angle theta(Prism+MLAS) of the second optical sheet module.

As shown in FIG. 5(b), the backlight unit according to the above configuration forms a refraction angle theta_i by the light guide plate 200 between 65° and 85°, so that the refraction angle theta(Prism+) of the second optical sheet module is formed. MLAS) can be controlled within ±5°.

Specifically, with reference to FIG. 5A , the refraction angle Theta(prism) of the first optical sheet module according to the refraction angle theta_i by the light guide plate is calculated as follows.

Theta(prism) = 45°- β

β=sin ^-1 (n _p * sin(α))

α= 45°- θ’

θ'=sin ^-1 (sin(θ _i )/n _p )

(However, n _p = Prism refractive index)

In addition, referring to FIG. 5A , the refraction angle Theta(prism+MLAS) of the second optical sheet module according to the refraction angle theta_prism of the first optical sheet module is calculated as follows.

Theta(prism+MLAS) = A-β’

β'=sin ^-1 (n _m * sin(α'))

α' = A-θ _o '

θ _o '=sin ^-1 (sin(θ _prism )/n _m )

(However, A is the size of the first base angle further away from the light source 100 among the base angles of the photometric projection triangle 423a', n _m = MLAS refractive index)

In the above formula, n _p and n _m represent the refractive indices of the first optical sheet module 300 and the second optical sheet module 400, respectively, and n _p is the thickness of the first base film, the first light incident surface, and the first large light surface. may vary depending on the shape and size of the

In addition, as described above, n _m can be changed by changing the thickness of the second base film, the shapes of the second light-incoming surface, the second light-facing surface, and the light-metering surface constituting the second light collecting part, and their materials.

In the case of using the second optical sheet module 400 having the quadrangular pyramid-shaped protrusion as described above, a backlight unit having excellent performance can be configured with only two optical sheet modules.

As described above, the backlight unit according to the present invention is composed of only two optical sheets, and thus has an advantage in that it can be configured to have a very thin thickness. Those skilled in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof.

Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention.

1, 100: light source
2, 200: light guide plate
3: diffusion sheet
300: first optical sheet module
310: first base film
320: first light collecting unit
322: first light incident surface
324: first large-gwang surface
4: light collecting sheet
400: second optical sheet module
410: second base film
420: second light collecting unit
421: second light incident surface
422: the second great light
423a, 423b: metering surface
421': 2nd light incident surface projection triangle
423a': metering plane projection triangle

Claims (10)

light guide plate;
a light source provided on one side of the light guide plate;
a first optical sheet module provided on the light guide plate; and
a second optical sheet module provided on an upper portion of the first optical sheet module;
The first optical sheet module,
a first base film in the form of a sheet that transmits light; and
A first light-incident surface formed on the first base film to face the light source and inclinedly formed, and a first light-receiving surface in contact with an upper portion of the first light-incident surface and inclined in the opposite direction to the first light incident surface. Consisting of a;
The second optical sheet module,
a second base film in the form of a sheet that transmits light; and
A second light collecting unit in which the second unit light collecting body in the shape of a quadrangular pyramid formed on the second base film is arranged;
The second unit light collecting body may include a second light incident surface facing the light source;
a second light-facing surface configured to face the second light-incident surface and to face the second light-incident surface; and
An ultra-thin backlight unit comprising two light-facing surfaces configured to form a quadrangular pyramid by connecting the second light-receiving surface and the second light-facing surface.
According to claim 1,
The second light incident surface and the second large light surface are isosceles triangles,
The two photometric surfaces are triangles of the same shape,
An equilateral length of a triangle forming the second light incident surface is shorter than an equilateral length of a triangle forming the second light incident surface.
3. The method of claim 2,
An ultra-thin backlight unit, wherein a vertex where four surfaces of the quadrangular pyramid-shaped second unit light collector meet is disposed closer to the light source than a central point of a bottom surface of the quadrangular pyramid.
3. The method of claim 2,
A triangle formed by a plane passing through the vertex C where the four faces of the second unit light collecting body meet, parallel to the base of the second light incident face, and perpendicular to the bottom surface of the second unit light collecting body 420a is a second light incident surface projection triangle;
A light metering surface projection triangle passing through the vertex C where the four sides of the second unit light collector meet, parallel to the base of the two light metering surfaces, and forming a triangle formed by a surface perpendicular to the bottom surface of the second unit light collector; When you say
The vertex angle of the second light incident surface projection triangle is 90°,
An ultra-thin backlight unit having a size of 45° among the two base angles of the photometric projection triangle further away from the light source.
5. The method of claim 4,
The height (h) of the second unit light collector is 10㎛ ultra-thin backlight unit.
6. The method of claim 5,
An ultra-thin backlight unit having a bottom surface of the second unit light collecting body formed in a square shape and having a side length of 20 μm.
3. The method of claim 2,
The second light incident surface and the second large light surface are isosceles triangles,
In addition, in a partial region of the second light collecting part, an equilateral length of a triangle forming the second light incident surface is formed to be shorter than an equilateral length of a triangle forming the second light receiving surface,
In another region, an equilateral length of a triangle forming the second light incident surface is longer than an equilateral length of a triangle forming the second light incident surface.
3. The method of claim 2,
An ultra-thin backlight unit configured to have different vertex positions where the four surfaces of the quadrangular pyramid-shaped second unit light collecting body meet depending on the position of the second unit light collecting unit on the second light collecting unit.
9. The method according to any one of claims 1 to 8,
A refraction angle (Theta(prism)) of light by the first optical sheet module satisfies the following (Equation 1) to (Equation 4) for an ultra-thin backlight unit.
Theta(prism) = 45°- β, (Equation 1)
β=sin ^-1 (n _p *sin(α)), (Equation 2)
α = 45°- θ', (Equation 3)
θ'=sin ^-1 (sin(θ _i )/n _p ), (Equation 4)
(However, n _p = refractive index of the first optical sheet module, θ _i is the angle of refraction by the light guide plate)
9. The method according to any one of claims 1 to 8,
The refraction angle (Theta(prism+MLAS)) of light by the second optical sheet module satisfies the following (Equation 1) to (Equation 4) for an ultra-thin backlight unit.
Theta(prism+MLAS) = A-β', (Equation 1)
β'=sin ^-1 (n _m *sin(θ')), (Equation 2)
α' = A-θ _o ', (Equation 3)
θ _o '=sin ^-1 (sin(θ _prism )/n _m ), (Equation 4)
(However, A is a triangle formed by a plane passing through the vertex (C) where the four sides of the second unit light collector meet, parallel to the base of the two photometric surfaces, and perpendicular to the bottom surface of the second unit light collector. metering surface projection triangle; refractive index of for instance, the metering surface projected two mitgak of mitgak further away from the light source size, n _m = the second optical sheet module of the triangle as, θ _prism is first according to the first optical sheet module angle of refraction)

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