CN103423707A

CN103423707A - Light Guide Panel and back light unit having the same

Info

Publication number: CN103423707A
Application number: CN2013100720968A
Authority: CN
Inventors: 李大熙; 白道铉; 李佶泓; 李迎铁; 郑明烈; 赵虔皓; 曹秉辰; 崔亨植; 邢信旭
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2012-03-14
Filing date: 2013-03-07
Publication date: 2013-12-04
Also published as: KR20130105215A

Abstract

The invention provides a light guide plate (LGP) and back light unit having the same. The light guide plate (LGP) according to a preferred embodiment of the present invention has the front side, the rear surface and four edge plates and comprise the multiple light output patterns for inducing the multiple lenticular patterns formed in any one of front side and rear surface the light coming from light sources is received among edge plates through at least one edge plate and the light which is income from light sources towards the front side. Here, unificational multiple light output patterns are formed in multiple lenticular patterns.

Description

LGP, back light unit and display unit

Technical field

The back light unit that relates to a kind of LGP and have this LGP with consistent panel disclosed herein and unit, more specifically, relate to have the lenticular pattern LGP of (lenticular pattern) and the back light unit with this LGP.

Background technology

Liquid crystal display (LCD) generally includes the display floater that shows image thereon and from the back light unit of the back side supply light of display floater.LCD is widely used in the display unit such as television set, computer monitor etc.

In the middle of various types of back light units, the peripheral type back light unit comprises that a plurality of light sources of being usually placed on side surface (for example, LED) and the LGP (LGP) that will be directed to by the light of light source supply display floater.

LGP generally includes a plurality of light emission patterns for the some form (dot form) towards display floater guiding light.In addition, while implementing in the display unit that three-dimensional (3D) image is being provided, LGP can have at lip-deep a plurality of lenticular patterns to improve the 3D scan efficiency.In the such LGP with lenticular pattern with light emission pattern, light emission pattern is formed on the rear surface of LGP usually, and the lenticular pattern is formed on the front surface of LGP.

Summary of the invention

Therefore, one or more exemplary embodiments have overcome above shortcoming and above other shortcoming of not describing.In addition, do not require that exemplary embodiment overcomes above-mentioned shortcoming, exemplary embodiment can not overcome above-mentioned any problem.

One side according to exemplary embodiment, provide a kind of and improved productivity ratio and reduced the LGP (LGP) of manufacturing cost and the back light unit with this LGP, wherein this LGP provides at least optical efficiency and the 3D scan efficiency with conventional LGP par.

One side according to exemplary embodiment, a kind of LGP used in display unit (LGP) is provided, this LGP can comprise: front surface, rear surface and four edge surfaces, wherein pass through at least one introducing four edge surfaces from the light of light source emission; A plurality of lenticular patterns, be formed on in front surface and rear surface; And a plurality of light emission patterns, the light towards the front surface guiding from the light source emission, wherein a plurality of light emission patterns and a plurality of lenticular pattern form.

Each light emission pattern can have a curved surface.

Light emission pattern can each be formed on the surface of lenticular pattern recessedly or protrudingly.

Light emission pattern can each be formed on the lenticular pattern recessedly, and has two reflectings surface about front surface or rear surface inclination.

Two reflectings surface can be smooth.

Two reflectings surface can tilt 35 ° to 80 ° about rear surface.

Two reflectings surface can become the angle of 70 ° to 110 °.

Spacing between two adjacent light emission patterns can be below 0.5mm.

LGP can receive light by two edge surfaces that are arranged opposite to each other in the middle of four edge surfaces.

According to the one side of another exemplary embodiment, a kind of back light unit used in display unit is provided, this back light unit can comprise: LGP (LGP) comprises front surface, rear surface and four edge surfaces; At least one light source, provide light in LGP by least one in four edge surfaces; Rear optical sheet unit, be arranged in the back of LGP; And front optical sheet unit, be arranged in the front of LGP, wherein LGP can comprise: a plurality of lenticular patterns are formed on in front surface and rear surface protrudingly; And a plurality of light emission patterns, the light towards the front surface guiding from the light source emission.A plurality of light emission patterns can form with a plurality of lenticular patterns.

Light emission pattern can each comprise a curved surface.

Front optical sheet unit can comprise a plurality of optical sheets.

Front optical sheet unit can comprise diffusion disk, prismatic lens and screening glass.

Front optical sheet unit can comprise diffusion disk, prismatic lens and reflecting polarizer.

Light emission pattern can each be formed on the lenticular pattern recessedly, and can each comprise two reflectings surface about front surface or rear surface inclination.

Front optical sheet unit can only have an optical sheet.

Front optical sheet unit can only have diffusion disk.

The accompanying drawing explanation

By describing certain exemplary embodiments with reference to the accompanying drawings, above and/or other aspect will become more obvious, in the accompanying drawings:

Fig. 1 is the plane of the LGP (LGP) according to embodiment;

Fig. 2 is the schematic back perspective view of the LGP of Fig. 1;

Fig. 3 is the local amplification sectional view along the line III-III intercepting of Fig. 2;

Fig. 4 is the schematic partial section according to the back light unit of the LGP with Fig. 1 to Fig. 3 of embodiment;

Fig. 5 is the plane according to the LGP of the second embodiment;

Fig. 6 A is the schematic back perspective view of the LGP of Fig. 5;

Fig. 6 B is the back perspective view of LGP according to an alternative embodiment;

Fig. 7 is the side view of the LGP of Fig. 5;

Fig. 8 is the partial section along the line VIII-VIII intercepting of Fig. 7;

Fig. 9 is the schematic partial section according to the back light unit of the LGP with Fig. 5 to Fig. 8 of embodiment;

Figure 10 A and Figure 10 B are Luminance Distribution image and the corresponding curves obtained from test #1;

Figure 11 A and Figure 11 B are Luminance Distribution image and the corresponding curves obtained from test #2;

Figure 12 A and Figure 12 B are Luminance Distribution image and the corresponding curves obtained from test #3;

Figure 13 A and Figure 13 B are Luminance Distribution image and the corresponding curves obtained from test #4;

Figure 14 A and Figure 14 B are Luminance Distribution image and the corresponding curves obtained from test #5;

Figure 15 A and Figure 15 B are Luminance Distribution image and the corresponding curves obtained from test #6;

Figure 16 A and Figure 16 B are conventional LGP and according to the image of the LGP of embodiment, and each all takes when the 3D scan efficiency is tested; And

Figure 17 presents two curves, is illustrated in the central brightness distribution data on the core of LGP of data of table 3 and table 4.

The specific embodiment

Now with reference to accompanying drawing, some exemplary embodiment is described in more detail.

In the following description, though identical Reference numeral in different accompanying drawings also for identical element, thereby be easy to be understood by those of ordinary skills.The exemplary embodiment that exemplary embodiment can be not limited to set forth here with various forms enforcement.For clear, omitted the description of well-known components, identical Reference numeral means identical element all the time.The content defined in description is provided to help the complete understanding to exemplary embodiment such as concrete structure and element.Therefore, obvious, can exemplifying embodiment embodiment and without the content of those specific definitions.They in addition, are not described in detail known function or structure, because can make the aspect of exemplary embodiment fog with unnecessary details.

Fig. 1 is the plane of the LGP (LGP) according to embodiment, and Fig. 2 is the schematic back perspective view of the LGP of Fig. 1, and Fig. 3 is the local amplification sectional view along the line III-III intercepting of Fig. 2.

Referring to figs. 1 through Fig. 3, can form the essentially rectangular shape according to the LGP (LGP, 110) of embodiment, there are front surface 111, rear surface 112 and four edge surfaces 113,114,115,116.

Front surface 111 can be faced display floater (not shown) relative with rear surface 112.For the convenience illustrated, four edge surfaces can be called as the first edge surface 113, the second edge surface 114, the 3rd edge surface 115 and the 4th edge surface 116, wherein the first and second edge surfaces 113,114 can be arranged relative to one another, and the third and fourth edge surface 115,116 can be arranged relative to one another.

With reference to Fig. 1, from the light L of light source emission, by the first and second edge surfaces 113,114, be introduced in LGP110.Although light enters by two edge surfaces 113,114 in one embodiment, this is the purpose for illustrating only.Therefore, in other embodiments, light can or be introduced by the edge surface more than three by the only edge surface in four edge surfaces.

With reference to Fig. 2 and Fig. 3, a plurality of lenticular patterns 117 can be formed on rear surface 112 to improve the 3D scan efficiency protrudingly.Lenticular pattern 117 can be formed uniformly between the first and second edge surfaces 113,114 and be arranged parallel to each other, and wherein light enters at the first and second edge surface 113,114 places.Each lenticular pattern 117 can have roughly semi-circular cross-section, but this can change according to embodiment.

Lenticular pattern 117 minimizes the light expansion of (that is, on Y-direction) on the width of LGP110 entered by the first and second edge surfaces 113,114.Namely, due to lenticular pattern 117, the light entered by the first and second edge surfaces 113,114 extends along the length direction (that is, on directions X) of LGP110.Namely, because incident light is due to lenticular pattern 117, the length direction (that is, on directions X) along LGP extends, so obtained higher 3D scan efficiency.

In one embodiment, lenticular pattern 117 can be formed on the rear surface 112 of LGP110.Alternatively, lenticular pattern 117 can be formed on the front surface 111 of LGP110.

With reference to Fig. 2 and Fig. 3, a plurality of light emission patterns 118 can form with lenticular pattern 117.Light emission pattern 118 scattered light on several directions, thus the direction of light towards display floater caused.

Light emission pattern 118 can have and the corresponding curved shape of the part of spherical surface.In alternative, light emission pattern 118 can have other curved shape except spherical surface.Light emission pattern 118 can be formed on the surperficial 117a of lenticular pattern 117 recessedly.In alternative, light emission pattern 118 can be formed on the surperficial 117a of lenticular pattern 117 protrudingly.

The shape of light emission pattern 118 can be commonly called ' point '.More specifically, when light emission pattern 118 has basically circular cross section along X-Y plane, light emission pattern 118 is called as ' point '.In alternative, light emission pattern 118 can be bar (bar) rather than point.Namely, replace having the circular cross-section about X-Y plane, light emission pattern 118 can have length at LGP110 (that is, X) direction or width (that is, the Y) cross section of extending more on direction.

Due to light emission pattern 118 and lenticular pattern 117 one, so lenticular pattern 117 and light emission pattern 118 can form simultaneously.Namely, lenticular pattern 117 can be stamped together with light is launched pattern 118, mold pressing or injection moulding to be to be shaped simultaneously.

In one example, LGP110 can manufacture as follows by impression.At first, by pressing on the paste PMMA that contains therein sclerosis initator (hardening initiator) and launching the corresponding mould of lenticular pattern 117 of pattern 118 one with light, the shape of launching the lenticular pattern 117 of pattern 118 one with light (for example is formed on the LGP material, polymethyl methacrylate, PMMA) on.Then, by making PMMA, under ultraviolet ray, harden, prepare the LGP110 of final form.

As above illustrate, lenticular pattern 117 and light emission pattern 118 can for example be shaped by the processing (that is, side by side) during preparation LGP110.Thereby the manufacture of LGP110 becomes simpler, and manufacturing cost reduces.

In addition, conventional LGP requires lenticular pattern and light emission pattern to be respectively formed on two different surfaces usually, rather than one each other.For example, the lenticular pattern is formed on front surface, and light emission pattern is formed on the rear surface of LGP.In so conventional LGP, at first the lenticular pattern is formed on circular LGP dish, and then light emission pattern forms thereon by Laser Processing or printing in rear processing.

Not the conventional LGP formed each other in order to prepare wherein lenticular pattern and light emission pattern, need the processing separated to be formed separately lenticular pattern and light emission pattern.Therefore, with exemplary embodiment, compare the manufacture very complex of conventional LGP and there is higher cost.

Fig. 4 is the schematic partial section according to the back light unit of the LGP with Fig. 1 to Fig. 3 of embodiment.

With reference to Fig. 4, back light unit 110 can comprise LGP110, light source cell 120, rear optical sheet unit 130 and front optical sheet unit 140.

As described above, LGP110 can have a plurality of lenticular patterns 117 that are formed on its rear surface 112, and light emission pattern 118 can form with lenticular pattern 117.

Light source cell 120 can relatively be arranged with the first edge surface 113 of LGP110.Light source cell 120 can comprise circuit board 121 and be arranged on a plurality of light sources 122 on circuit board 121.For example, light source 122 can comprise LED.From the light of a plurality of light source 122 emissions, can be incorporated into LGP110 by the first edge surface 113.Although do not illustrate, have with another light source cell of light source cell 120 same structures of Fig. 4 and can relatively arrange with the second edge surface 114 of LGP110.

Rear optical sheet unit 130 can be arranged in the back side of LGP110, and can comprise reflector plate 131.The light that reflector plate 131 will leak from the rear surface 112 of LGP110 is reflected back LGP110.

Front optical sheet 140 can be arranged in the front of LGP110, and can comprise diffusion disk 141, prismatic lens 142 and screening glass 143.Diffusion disk 141 diffusions are from the light of LGP110 emission, and prismatic lens 142 is gathered in the light of diffusion disk 141 places diffusion, screening glass 143 protection prismatic lenses 142 and raising optical uniformity.In alternative embodiment, in order to improve the purpose of optical efficiency, can replace screening glass 143 with reflecting polarizer.Reflecting polarizer can be collection, polarization and radiative reflection multilayer devating prism sheet, such as the two brightness enhancement films of the DBEFTM(produced by 3M).

With reference to Fig. 4, the light L produced at light source 122 places launches on the frontal at LGP110 due to LGP110 and reflector plate 131, because light through three front optical sheets 141,142,143 then light L enter on the display floater (not shown), so the brightness uniformity of the light of launching and visual angle are improved.

Fig. 5 is the plane according to the LGP of the second embodiment, Fig. 6 A is the schematic back perspective view of the LGP of Fig. 5, Fig. 6 B is the back perspective view of LGP according to an alternative embodiment, and Fig. 7 is the side view of the LGP of Fig. 5, and Fig. 8 is the partial section along the line VIII-VIII intercepting of Fig. 7.

With reference to Fig. 5 to Fig. 8, can form the essentially rectangular shape according to the LGP210 of the second embodiment, and can comprise front surface 211, rear surface 212 and four edge surfaces 213,214,215,216.For the convenience illustrated, four edge surfaces can be called as the first edge surface 213, the second edge surface 214, the 3rd edge surface 215 and the 4th edge surface 216.

From the light L of light source emission, by the first and second edge surfaces 213,214, be incorporated into LGP210.Although light enters by two edge surfaces 213,214 in one embodiment, this is the purpose for illustrating only.Therefore, in another embodiment, light can or be introduced by plural edge surface by the only edge surface in four edge surfaces.

Can there is the similar structure with LGP110 described above according to the LGP210 of the second embodiment.Therefore, as LGP110 described above, according to the LGP210 of the second embodiment, can have a plurality of lenticular patterns 217 that are formed on its rear surface 212, light emission pattern 218 can be integrally formed with lenticular pattern 217.With reference to Fig. 6 A, the light emission pattern 218 be formed on LGP210 can the well-regulated arrangement of tool.Alternatively, with reference to Fig. 6 B, in another embodiment, light emission pattern 218 can have irregular pattern.

The difference of the second embodiment is the shape of the light emission pattern 218 of LGP210, and it is different from the light emission pattern 118 of the LGP110 of embodiment described above.This will describe in detail below.

With reference to Fig. 6 A and Fig. 8, light emission pattern 218 can form from the surface of lenticular pattern 217 recessedly.Each light emission pattern 218 can have two reflecting

surface

218a, 218b, therefore has and the similar shape of prism.Reflecting surface 218a, the 218b of light emission pattern 218 can be smooth, and this spheroform surface (see figure 3) from light emission pattern 118 described above is different.

With reference to Fig. 8, this is to the angled α of reflecting

surface

218a, 218b, and can arrange with being mutually symmetrical.Angle between two reflecting

surface

218a, 218b can be between 70 ° to 110 ° scope.In addition, each reflecting

surface

218a, 218b with respect to the front surface 211 of LGP210 or rear surface 212(, with respect to X-axis) tilt, the angle beta of inclination is the scope between 35 ° to 80 ° preferably.

In addition, the spacing between two adjacent light emission patterns 218 can be preferably 0.5mm or following.For illustrated convenience, a lenticular pattern 217 is shown as and only is formed with three light emission patterns 218, but will understand, and the actual quantity of light emission pattern 218 can advantageously be greater than the quantity shown in accompanying drawing.

As described above, the LGP110 of embodiment is the same, can be by manufacturing with impression, mold pressing or injection moulding according to the LGP210 of the second embodiment, by applying these technique, lenticular pattern 217 and light emission pattern 218 can only form by a processing (that is, simultaneously) or be shaped.Therefore, with the emission of light wherein pattern, by the conventional LGP such as being processed to form after Laser Processing or printing, compare, according to the manufacture of the LGP of the second embodiment cost simpler and need to be lower that becomes.

Fig. 9 is the schematic partial section according to the back light unit of the LGP with Fig. 5 to Fig. 8 of embodiment.

With reference to Fig. 9, back light unit 200 can comprise LGP210, light source cell 220, rear optical sheet unit 230 and front optical sheet unit 240.

As described above, LGP210 can have a plurality of lenticular patterns 217 that are formed on its rear surface 212, and light emission pattern 218 can form with lenticular pattern 217.Each light emission pattern 218 can have two reflecting

surface

218a, 218b, therefore has and the similar cross section of prism.

Light source cell 220 and rear optical sheet unit 230 are identical with rear optical sheet 130 with the above light source cell 120 with reference to Fig. 4 explanation.

Front optical sheet unit 240 can only have a diffusion disk 241, and these are different from front optical sheet described above unit 140.

Although back light unit 200 only has a diffusion disk 241 in the LGP210 front, but the light emission pattern 218 that there are two smooth reflecting

surface

218a, 218b by enforcement, back light unit 200 can at least keep the optical property (such as luminous efficiency, visual angle, 3D scan efficiency etc.) with the back light unit with a plurality of front optical sheets (such as, back light unit 100) par.

The inventor has carried out test to confirm the optical property according to the LGP210 of the second embodiment.Therefore, the inventor uses the LGP210 described above according to an embodiment, and by its with conventional LGP(wherein the lenticular pattern be formed on front surface and the light of some form is launched pattern and is formed on rear surface) compare.

With reference to following table 1; about independent conventional LGP, be added with the conventional LGP of diffusion disk on it; the conventional LGP that is added with diffusion disk and prismatic lens on it with and on be added with diffusion disk, prismatic lens and screening glass conventional LGP carried out four tests, carried out twice test about the LGP210 according to embodiment and the LGP210 according to embodiment that is added with diffusion disk.

Table 1

As the result of being tested under six kinds of situations based on routine techniques and embodiment, obtain Luminance Distribution image and the corresponding curve thereof taken from the front surface of LGP, as shown in Figure 10 A to Figure 15 B.

Namely, Figure 10 A and Figure 10 B are Luminance Distribution image and the corresponding curves obtained from test #1, Figure 11 A and Figure 11 B are Luminance Distribution image and the corresponding curves obtained from test #2, Figure 12 A and Figure 12 B are Luminance Distribution image and the corresponding curves obtained from test #3, Figure 13 A and Figure 13 B are Luminance Distribution image and the corresponding curves obtained from test #4, Figure 14 A and Figure 14 B are Luminance Distribution image and the corresponding curves obtained from test #5, and Figure 15 A and Figure 15 B are Luminance Distribution image and the corresponding curves obtained from test #6.

With reference to Figure 10 A to Figure 13 B relevant to routine techniques, routine techniques only shows 0 °, good Luminance Distribution and visual angle in three optical sheets (that is, diffusion disk, prismatic lens, screening glass) are arranged in the test #4 of LGP front.

On the contrary, with reference to Figure 14 A to Figure 15 B relevant to embodiment, embodiment shows 0 °, good Luminance Distribution and visual angle at optical sheet only in being arranged in the test #6 of LGP front.

As follows from center brightness, median brightness (median brightness) and the brightness uniformity of test #4 and test #6 calculating:

Table 2

With reference to table 2, can provide the brightness uniformity with the routine techniques par according to the LGP210 of embodiment, and need to be more than the diffusion disk of.In addition, can provide and be enhanced approximately 10% center brightness and median brightness according to the LGP210 of embodiment.

In addition, compare the test according to LGP210 and the 3D scan performance between conventional LGP of embodiment, wherein test #1 and be used as conventional LGP to the LGP that tests #4, the LGP of test #5 and test #6 is used as the LGP according to embodiment.

Test is carried out as follows: the brightness by measuring the light entering part and with the brightness of the core of the corresponding LGP of light source, only keep being arranged in a light source in the middle of a plurality of light sources (LED) of LGP mono-side in conducting state simultaneously, and make other light source in off-state.

Figure 16 A and Figure 16 B are presented on the image captured in test described above.In addition, from the numeric data of measuring and calculation, be listed in table 3 and table 4, the curve corresponding with the data in table is provided in Figure 17.

Figure 16 A and Figure 16 B are conventional LGP and according to the image of the LGP of embodiment, and each takes when the 3D scan efficiency is tested.Table 3 and table 4 have been listed to conventional LGP with according to the data of the 3D scan efficiency measuring and calculation of the LGP of embodiment.Figure 17 presents two curves, is illustrated in the central brightness distribution data on the core of LGP of data of table 3 and table 4.

Table 3

Table 4

With reference to table 3 and table 4, about the brightness of the core of secondary light source with about the ratio between the brightness of the core of the 5th light source, equal 3%.Thus, show that the 3D scan efficiency is not degenerated from the 3D scan efficiency of conventional LGP when the LGP210 that uses according to embodiment.The curve of Figure 17 has also been confirmed the above.Namely, the transverse axis of the curve of Figure 17 means LED quantity, and the longitudinal axis is illustrated in the brightness of the central part office of LGP.Curve with mark (link) ' ■ ' means conventional LGP, with the curve of mark ' * ', means the LGP according to embodiment.

Previous embodiment and advantage are only exemplary, and should not be interpreted as limiting the present invention's design.This instruction can easily be applied to the device of other type.In addition, the description of the exemplary embodiment of the present invention's design is intended to describe, and is not intended to limit the scope of claim, and many replacements, modification and variation will be obvious for those skilled in the art.

The application requires the U.S. Provisional Application No.61/610736 that submits in United States Patent (USP) trademark office on March 14th, 2012 and the priority of the korean patent application No.10-2012-0049468 that submits in Korea S Department of Intellectual Property on May 10th, 2012, and its disclosure integral body by reference is incorporated into this.

Claims

1. the LGP used in display unit, described LGP comprises:

Front surface, rear surface and four edge surfaces, the light of wherein launching from light source is by least one introducing described four edge surfaces;

A plurality of lenticular patterns, be formed on in the described front surface of described LGP and described rear surface; And

A plurality of light emission patterns, the described light of launching from described light source towards the described front surface guiding of described LGP,

Wherein said a plurality of light emission patterns and described a plurality of lenticular pattern form.

2. LGP according to claim 1, wherein each described light emission pattern has a curved surface.

3. LGP according to claim 2, each recessed ground of wherein said light emission pattern or protruding being formed on the surface of described lenticular pattern.

4. LGP according to claim 1, each is formed on wherein said light emission pattern on described lenticular pattern recessedly, and has two reflectings surface about described front surface or the inclination of described rear surface.

5. LGP according to claim 4, wherein said two reflectings surface are smooth.

6. LGP according to claim 5, wherein said two reflectings surface tilt 35 ° to 80 ° about described rear surface.

7. LGP according to claim 5, wherein said two reflectings surface become the angle of 70 ° to 110 °.

8. LGP according to claim 4, wherein the spacing between two adjacent light emission patterns is below 0.5mm.

9. LGP according to claim 1, wherein said LGP receives described light by two edge surfaces arranging relative to one another in the middle of described four edge surfaces.

10. the back light unit used in display unit comprises:

LGP, comprise front surface, rear surface and four edge surfaces;

At least one light source, provide light in described LGP by least one in described four edge surfaces;

Rear optical sheet unit, be arranged in the back of described LGP; And

Front optical sheet unit, be arranged in the front of described LGP,

Wherein said LGP comprises:

A plurality of lenticular patterns are formed on in the described front surface of described LGP and described rear surface protrudingly; And

A plurality of light emission patterns, the described light of launching from described at least one light source towards the described front surface guiding of described LGP,

11. back light unit according to claim 10, each comprises a curved surface wherein said light emission pattern.

12. back light unit according to claim 11, wherein said front optical sheet unit comprises a plurality of optical sheets.

13. back light unit according to claim 10, each is formed on wherein said light emission pattern on described lenticular pattern recessedly, and each comprises two reflectings surface about described front surface or the inclination of described rear surface.

14. back light unit according to claim 13, wherein said front optical sheet unit only consists of diffusion disk.

15. a display unit, comprise the described back light unit of any one in claim 10 to 14.