TWI337271B - Light guide plate and backlight module - Google Patents

Description

1337.271 October 13th, 1999, the invention of the invention: [Technical field] [0001] The present invention relates to a light guide plate and a backlight module used in the field of liquid crystal display, and more particularly to a side light type light guide plate and Backlight module. [Prior Art] [0002] Light Guide Plate (LGP) mainly includes light incident surface, reflective surface, exit surface and several side surfaces, which are important components in the liquid crystal display backlight module system. Its function is to guide the light emitted by a scattered point source (such as a light emitting diode) or a line source (such as a cold cathode tube) to exit from a flat surface, and at the same time improve the uniformity of the panel gradation and illuminance. The light guide plate is generally made of a synthetic resin material, and the shape of the substrate is divided into a flat plate type and a wedge type curved surface type. [0003] [0004] The light entering the light guide plate will propagate in the plate according to the principle of full emission. When the light encounters the pattern of the surface of the light guide plate, the full emission condition is destroyed, and the light is emitted from the front surface of the light guide plate. The micro-structure design with different density and size can make the light guide plate emit light uniformly. The manufacturing technology of the light guide plate microstructure can be divided into two categories: printed and non-printed. The former uses a screen printing method to print ink on the light guide plate to produce a microstructure shape and its distribution. In the latter case, the injection molding technology is adopted directly, and the microstructure design is more continuous in the process, and the precision is high, which is the mainstream of the current light guide plate manufacturing technology. Non-printing methods are divided into: chemical engraving method, direct recording method and precision machining method. 093131353 uispiay, LCD) Expansion of the application form such as mobile phone, car display, 81-person digital assistant (Personal Distal Assistant, pda, and TV) Form number A010丨3// „ Page 3 of 26 0993367629- 1337271 October 13 099 'There are higher requirements for backlight technology based on light guides, mainly in: high brightness, low cost, low energy consumption, thin and light.

[0005] Referring to the first figure, in order to make more energy incident on the LGP from the incident angle of the light beam, the incident surface of the LGP is generally made into a groove, and then the light emitting diode (Light Emission Diode, LED) is used as a light source. ) placed in it. The design of this built-in light source will make the LGP thicker, which is not conducive to thin and light design, and due to the built-in LED, poor heat dissipation will affect the normal use of LGP. [0006] Referring to the second figure, U.S. Patent No. 6,421,104 is directly placed behind a light source by a conventional refractive lens, and its design flexibility and compactness are relatively poor. [〇〇〇7] Please refer to the third figure, published in July 31, 998, published in Japanese Patent Application No. 1 0-1 9931 6 Japanese Patent Application, which uses a V-shaped incident surface to process the V-shaped structure to change the incident of the LED. Angle, but its design flexibility is poor, and the coupling efficiency is relatively low. [0008] Referring to the fourth and fifth figures, the U.S. Patent Application Publication No. 20030214818, issued on Nov. 20, 2003, uses a design similar to that of Figure 3, due to its use of a V-shaped groove of a periodic structure, The control ability of the beam is limited, and the efficiency of the private combination is not high. [〇〇〇9] At present, Diffm- ive Optical Elements (DOEs) based on the theory of light wave diffraction have the advantages of small size, light weight, great design freedom, wide material selectivity, etc. The transformation has many excellent functions that are difficult to achieve with traditional optics'. It is widely used in such things as misfocus focusing, fitting, spectral crossing, related 093131353 Form No. A0101 Page 4 / Total 26 Page 0993367629-0 1337271 099 October 13 In the future, it will replace page filtering, beam shaping, wavelength interval multiplexing and signal processing, etc. [0010] Please refer to the sixth picture, US Patent No. 6, 636, 283 of October 21, 2003 The patent proposes a structure in which a diffraction microlens is fabricated on a substrate and then placed between the light source and the LGP to collimate the incident light and then enter the LGP. This design allows for a slim and light design, but because of its separate design, the system has a large lateral dimension and a complex system structure, which is not conducive to improving energy efficiency. [00Π] Therefore, it is necessary to provide a compact light guide plate and a backlight module using the same that can improve energy utilization. SUMMARY OF THE INVENTION [0012] The first technical problem to be solved by the present invention is to provide a light guide plate which can improve energy utilization and has a compact structure. [0013] A second technical problem to be solved by the present invention is to provide a backlight module having the above-mentioned light guide plate' capable of improving energy utilization and compact structure [0014] In order to solve the above first technical problem, the present invention provides The technical solution is a light guide plate comprising an incident surface, an exit surface and a reflective surface provided with a plurality of microstructures, the incident surface being formed with at least one diffraction structure. [0015] wherein the diffraction structure is preferably an aspherical diffraction structure. [0016] The phase delay of the #spherical diffraction structure is further satisfied by the following formula: [0017] 093131353 Form No. A0101 5th Buy/Total 26 Page 0993367629-0 1337271 October 13, 1999 Correction Replacement Page [0018] Where f is the focal length of the aspherical diffraction structure, n2 is the refractive index at the focal point, λ is the incident wavelength in vacuum, seven is the wave number in vacuum, and X is the distance from any point on the surface of the aspherical diffraction structure to its central axis . [0019] The depth y(x) of the aspherical diffraction structure preferably satisfies the following formula: [0020] _^-

7〇)=——-—(V/2 + - / - ^ ^2 ) «1 - «2 < |^| < DI 2) [0021] where λ2~ λ!n2 m=L 〇^ 7··· , the number of rings of the aspherical diffraction structure, the refractive index of the aspherical diffraction structure, and the diameter of the D-system aspherical diffraction structure,

[0022] representing the distance from the end point of each of the aspherical diffraction structures to the central axis of the aspherical diffraction structure, satisfying the formula: [0023] nl/2 〇 [0024] the diffraction The structure may protrude outwardly from the light guide plate or may be recessed inwardly into the light guide plate. [0025] The exit surface is formed with at least one second diffraction structure, which may be an aspherical diffraction structure. 093131353 Form No. Α0101 Page 6 of 26 0993367629-0 1337271 October 13, 2017 Correction Replacement Page [0026] The light guide plate may be a flat plate or a wedge plate. [0027] In order to solve the above second technical problem, the present invention provides a backlight module including a light guide plate and a light source on a side thereof, wherein the light guide plate includes an incident surface and an exit surface. A plurality of microstructured reflective surfaces are formed, the incident surface being formed with at least one diffraction structure. [〇〇28] Compared with the prior art, the present invention draws on the characteristics of large design freedom of the diffractive optical structure and strong controllability of the light beam, and adopts a direct optical structure directly formed on the incident surface of the LGP, so that the entire structure is The compactness is high, and the surface profile of the structure can be flexibly designed according to the size and position of the light source to adjust the incident angle of the incident beam of the conventional LED, thereby improving the coupling efficiency of the beam, thereby improving the utilization of the light energy, and the light guide plate has high brightness and low energy. loss. In addition, it is better to eliminate the shadow effect of uneven energy distribution due to the use of discrete point light sources (LEDs). [0029] In the meantime, the present invention can also design a diffractive optical structure of different structures on the exit surface of the LGP, thereby achieving the control effect on the LGP exit angle and energy distribution, and further improving the energy utilization rate of the backlight system. [Embodiment] The present invention will be further described in detail below with reference to the accompanying drawings. [0031] Please refer to the seventh and eighth figures together. The flat type light guide plate 50 provided by the present invention includes an incident surface 51, a reflecting surface 52, an emitting surface 53, and other sides thereof. Mark). The incident surface 51 is formed on a side of the light guide plate 50 adjacent to the light source 70. The exit surface 53 is formed on the top surface of the light guide plate 50. The reflecting surface 52 is formed on the bottom surface of the light guide plate 50, and is provided with a plurality of microstructures 521. 093131353 Form No. A0101 Page 7 of 26 0993367629-0 H37271 October 13th, 2008, the shuttle replacement page [0032] & In this example, the incident surface 51 is formed with an aspherical diffraction structure. The phase retarder of the mysterious aspherical diffraction structure 512 satisfies the following relation (1): [0033] _ ^ (^) = (/ - ^/72 + ) [0034]

Where f is the focal length of the aspherical diffraction structure 512, and n2 is the refractive index at the focus 'λ Μ Μ airborne wavelength 乂 , which is the number of waves in the vacuum. The focal length range is 2~10mm. According to the situation, the focal length of the light-incident surface is relatively short, and the focal length of the light-emitting surface is relatively long, which requires design. χ is the distance from any point on the surface of the aspherical diffraction structure 512 to its central axis (such as X!, x2 ' x3), and its value depends on the size of the LGP, which is generally -1 5mm~+ 1 5mm. [0035] At the same time, the depth y of the aspherical diffraction structure 512, that is, the distance from any point on the surface of the aspherical surface structure 512 to the base surface of the aspherical diffraction structure 512 is generally a few micrometers. A few hundred micrometers or so, which satisfies the following relation (2): [0036] __ y(x) = ~ J2 + - f - m λ2) <|^|<min(^+1>Z)/2) y _ where,;= ;!/% ' w = 0,1,.··,* aspherical diffractive knot 093131353 Form No. A0101 Page 8 of 26 0993367629-0 1337271 Correction replacement on October 13, 099 page

The ring number ′ of the structure 512 is the refractive index of the aspherical diffraction structure 51 2 , and the aperture of the D-system aspherical diffraction structure 51 2 , that is, D = x , * max [0038] represents the aspherical diffraction structure 51 2 per One of the ring ends to the point

The distance of the central axis of the iW aspherical diffraction structure 512 satisfies the following relationship (3 [0039]

2 ] 1/2 ° [0040] The depth y of the aspherical diffraction structure 512 and the size of the edge are generally

The X3H should be selected based on processing capabilities. [0041] The aspherical diffraction structure 512 protrudes outward from the light guide plate 50. It should be pointed out that for the convenience of actual processing, the aspherical diffraction structure 512 of the curved surface type can be replaced by a straight surface type, which is more convenient to process without affecting performance.

[0042] In the present embodiment, in order to comprehensively utilize the functions of the discrete light sources 70, an aspherical diffraction structure 512 is formed on the entire incident surface 51. Of course, a plurality of independent diffraction structures respectively corresponding to the respective light sources 70 may be formed on the incident surface 51 according to the number of the light sources 70, and are not necessarily limited to this embodiment. [0043] Please refer to the ninth figure, which is a distribution value of the intensity field of the LGP exiting light when an LED is placed at the center of the light incident surface of the LGP, wherein the ninth A is a diffraction-free structure of the incident surface. Figure IXB shows the case where the incident surface has the diffraction structure of the present invention. Among them, the exit surface of the LGP used in the experiment has no diffraction structure, and its specific parameters are: f = 3mm, X is 3mm~+ 3mm, 093131353 Form No. A0101 Page 9 / Total 26 Page 0993367629-0 1337271 099 October 13 The maximum value of the depth of the replacement page is 〇.41mm ' 1^ = 1.49 ' n2=l, and the wavelength is visible light. The experimental results show that the diffraction structure of the incident surface has a significant effect on the modulation of the light field. In addition, in the embodiment, a second aspherical diffraction structure 532 is also formed on the exit surface 53 of the light guide plate 50, and the phase delay of the diffraction surface pattern also satisfies the above relationship (1). The specific parameters should be designed according to the actual situation, and generally different from the parameters of the aspherical diffraction structure 512 of the incident surface 51. Both have the same depth and can be designed to be different _ depth depending on the situation. In addition, the second aspherical diffraction structure 532 has a one-dimensional cylindrical shape extending from one end of the near-incident surface to the other end opposite thereto. It is also worth noting that it can also be designed as a two-dimensional curved shape r. The second aspherical diffraction structure 532 protrudes outwardly from the light guide plate 50. A system can be selected which can also be recessed inwardly into the light guide plate 50. [0046] The light guide plate 50 of the present invention is a flat type structure made of a synthetic resin material, and the reflective surface thereof may be a V-shaped structure or a micro structure such as a conventional circular dot [0047] The light source 70 is a point light source, such as led. Of course, a line source such as a cold cathode tube can also be used. [0048] Referring to the tenth figure, in order to verify the effect of the diffraction structure on eliminating the shadow phenomenon, the light field distribution of the light guide plates having the diffraction structure and the non-diffraction structure is calculated, and the light source is three identical LEDs. Among them, there is a diffractive structure light guide plate, and the specific parameters of the diffraction structure are: [0049] (1) light entrance surface, f = 3mm, X is at 1 5mm~+1 5mm, depth y is the most 093131353 Form No. A0101 10 pages/total 26 pages 0993367629-0 1.337271 The large value is 884.8841πππ, η =1.49, rig: 〇.55um; the corrected wavelength is visible light on October 13, 099 [0050] [0052] [0053] 2) The light-emitting surface 'f = l〇mm, X is -15mm~+ 15mm, the maximum depth y is 0·6316_, η = 1.49, n = l, and the wavelength is visible light 1 ^ 〇 .55um. [0054] 093131353 The results show that the diffraction structure has a significant ability to modulate the light field. Referring to FIG. 11 'the other flat type light guide plate 6 provided by the present invention is different from the flat type light guide plate 50 of the previous embodiment, and the main difference is that the aspherical diffraction structure formed by the incident surface 61 The 612 is recessed inwardly into the light guide plate 60. Referring to FIG. 12, a backlight module 8A using a light guide plate 5b includes a light guide plate 50, a light source 70 on a side thereof, a reflection plate 82 located therebelow, and a diffusion sheet 84 sequentially positioned thereon. Optical film such as sequins 86. The reflection sheet 82 re-introduces the unscattered light into the light guide plate 5, and the diffusion sheet 84 diffuses the light to uniformly diffuse, eliminating the bright region formed by the microstructure 521 on the light guide plate 50, and the brightness enhancement sheet 86 converges. Light, the effect of increasing brightness. Please refer to the thirteenth diagram. The above diffraction structure can also be applied to a chess type light guide plate. In the present invention, the present invention provides a light guide plate 90 including an entrance surface 91, a reflection surface 92, an exit surface 93, and other sides thereof (not shown). Among them, the human face 91 is formed with an aspherical diffraction structure 912 which also satisfies the above relations (1) to (3). It is to be noted that the present invention can also employ other shapes of diffraction structures, and is not limited to aspherical diffraction structures. Form No. 1010101 Page 11/Total 26 Page 0993367629-0 [0055] 1337271 Modified on October 13, 099 [0056] The present invention draws on the design of the diffractive optical structure with a large degree of freedom in design and strong control of the light beam. The feature is that the diffractive optical structure is directly formed on the incident surface of the LGP, so that the whole structure is compact, and the surface contour of the structure can be flexibly designed according to the size and position of the light source to adjust the incident angle of the incident beam of the conventional LED, thereby improving the coupling of the beam. Efficiency, thereby increasing the utilization of light energy, makes the light guide plate have high brightness and low energy loss. In addition, it is better to eliminate the shadow effect of uneven energy distribution due to the use of discrete point sources (LEDs) close to the source. [0057] At the same time, the invention can also design a diffractive optical structure of different structures on the exit surface of the LGP, thereby achieving the control effect on the LGP emission angle and the energy distribution, and further improving the energy utilization rate of the backlight system. In addition, those skilled in the art can also make other changes in the spirit of the present invention, such as providing an anti-reflection film on the reflective surface of the light guide plate instead of the reflective plate in the backlight module. Of course, these changes in accordance with the spirit of the invention are intended to be included within the scope of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS [0059] The first figure is a structural diagram of a combination of a conventional light source and a light guide plate; [0060] The second figure is a structure of a backlight system disclosed in U.S. Patent No. 6,421,104. BRIEF DESCRIPTION OF THE DRAWINGS [0061] FIG. 3 is a schematic view showing the structure of a backlight system disclosed in the present patent application; [0062] FIG. 4 is a prior art US Patent Application No. 2003021 481 8 Schematic diagram of the disclosed backlight system; 0993367629-0 [0063] The fifth figure is a partial enlarged view of the V portion in the fourth figure; 093131353 Form No. A0101 Page 12 of 26 1337271 r_ October 13, 1999 amendment [0064] FIG. 6 is a schematic view showing the structure of a backlight system disclosed in US Pat. No. 6,636,283; [0065] FIG. 7 is a perspective view of a flat type light guide plate provided by the present invention; 0〇66] FIG. 8 is a plan view of a flat-type light guide plate provided by the present invention; [0067] FIG. 9A is a light field intensity distribution diagram of a light guide plate having an incident surface without a diffraction structure, and 'Nineth B diagram The incident surface has a diffraction structure The light field intensity distribution of the light guide plate TSI · circumference, [0068] The tenth A picture is the light field distribution diagram of the light guide plate with no diffraction structure on the incident surface, and the tenth B picture is the light guide plate with the diffraction structure on the incident surface Light field distribution map; [0069] FIG. 11 is a schematic structural diagram of another flat type light guide plate provided by the present invention. [0070] FIG. 12 is a schematic structural view of a backlight module using the flat type light guide plate provided by the present invention. [00Ή] FIG. 13 is a perspective view of a wedge-shaped light guide plate provided by the present invention. [Main component symbol description] [0072] Light guide plate 50 incident surface 51 [0073] Aspherical diffraction structure 512 reflective surface 52 [0074] Microstructure 521 exit surface 53 [0075] Second aspherical diffraction structure 532 light guide plate 60 Injecting surface 61 aspherical diffraction structure 612 [0077] Light source 70 backlight module 80 0993367629-0 093131353 Form No. A0101 Page 13 / Total 26 pages 13327271 [0078] Reflector 82 Diffuser 84 [0079] Brightening sheet 86 Wedge Light Guide 90 ' [0080] Incidence Surface 91 Aspherical Diffraction Structure 912 [0081] Reflecting Surface 92 Exit Surface 9 3 093131353 Form No. A0101 Page 14 of 26 October 13th, 9999 Pressing the Replacement Page 0993367629-0

Claims (1)

Seven, the scope of application for patents: 099 January 1st, 13th kind of light guide plate, including - human face exit surface and - with a number of microstructured reflective surface, the improvement is that the person's face is formed with at least - aspheric The diffraction structure, the depth of the aspherical diffraction structure, that is, the distance between the abutment surface of the aspherical diffraction structure and the base surface of the aspherical diffraction structure, which satisfies the following formula: y( ^) ± = Ϊ / is 2, W = 0, 1, ... is the number of rings of the aspherical diffraction structure, 11 丨 is the refractive index of the aspherical diffraction structure, and the diameter of the D-type aspherical diffraction structure, X is The end point of each aspherical diffraction structure to the center axis of the bean w', The light guide plate of claim 1, wherein the phase retardation of the aspherical diffraction structure satisfies the following formula: 093131353 where f is the non-availability: 2mf^ + {m\) 2 1/2 The focal length of the spherical diffraction structure, η2 is the refractive index at the focus of the table. 0101 Page 15 of 26 Page 0993367629-0 1337271 October 13th, 1999, the replacement page, λ is the incident wavelength in vacuum = 2πί λ Is the wave number in the vacuum, and X is the distance from any point on the surface of the aspherical diffraction structure to the central axis of the aspherical diffraction structure. The light guide plate of claim 1, wherein the diffraction structure protrudes outward from the light guide plate. The light guide plate of claim 1, wherein the diffraction structure is recessed inwardly of the light guide plate. The light guide plate of claim 1, wherein the exit surface is formed with at least one second diffraction structure. The light guide plate of claim 5, wherein the second diffraction structure is an aspherical diffraction structure. The light guide plate of claim 1, wherein the light guide plate is a flat plate or a wedge plate. A backlight module includes a light guide plate and a light source on a side thereof, wherein the light guide plate includes an incident surface, an exit surface, and a reflective surface provided with a plurality of microstructures, wherein the incident surface is formed with at least An aspherical diffraction structure, the depth y(x) of the aspherical diffraction structure, that is, the distance from any point on the surface of the annulus structure of the aspherical diffraction structure to the base surface of the aspherical diffraction structure, which satisfies The following formula: yM = ———(V/2 + - f ~mA2) «ι - < |χ| < min(^+1, D / 2) where is the aspherical diffraction knot 093131353 Form No. A0101 Page 16 of 26 0993367629-0 1337271 The number of rings in the normal page after October 13, 099, \ is the refractive index of the aspherical diffraction structure, the aperture of the aspherical diffraction structure, and the aspheric surface The distance from the end of each ring of the diffraction structure to its center sleeve is satisfied: ~=[2 imitation/name+ 〇«々) 2]1/2. 9. The backlight module of claim 8, wherein the phase retarder of the aspherical diffraction structure satisfies the following formula: 屮())=allow 〇«2(/ -, / where f is The focal length of the aspherical diffraction structure is the refractive index at the focus, λ is the incident wavelength in vacuum, **...丄 is the wave number in the vacuum' X is the surface of the aspherical diffraction structure & point to aspherical diffraction The distance from the center axis of the structure. 10. The backlight module of claim 8, wherein the diffraction structure protrudes outwardly from the light guide plate. The backlight module of claim 8, wherein the diffraction structure is recessed inwardly of the light guide plate. The backlight module of claim 8, wherein the exit surface is formed with at least one second diffraction structure. The backlight module of claim 12, wherein the first ray diffraction structure is an aspherical diffraction structure. 093131353 The backlight module according to claim 8 of the patent application, wherein the form number Α0101, page 17 / total 26 pages, the light guide 0993367629-0 14 1337271, October 13, 1999, the shuttle is replacing the page board as a flat plate or Wedge plate. 093131353 Form No. A0101 Page 18 of 26 0993367629-0