KR20030015378A - Backlight with structured surfaces - Google Patents

Abstract

The backlight includes a waveguide, a light source and a turning film arranged relative to the waveguide for introducing light into the waveguide. The optical structure is formed on one of the rear face and the output face of the waveguide. The optical structure is arranged to emit light from the waveguide. The rear reflector is arranged near the rear face. The optical structure is formed to include a variable pattern arranged to shield non-uniformity at the output of the waveguide.

Description

Backlit with structured surface {BACKLIGHT WITH STRUCTURED SURFACES}

Backlit display devices, such as liquid crystal display (LCD) devices, typically use wedge-shaped waveguides. Wedge waveguides connect light from a substantially linear source, such as a cooling cathode fluorescent lamp (CCFL), to a substantially planar output. The flat output is used to illuminate the LCD.

One measure of performance of a backlight display is its uniformity. The user can easily detect a relatively small difference in brightness of the display from one area of the display to the next. Even relatively small non-uniformities can be very unpleasant for the user of the display.

Surface diffuser or bulk diffuser sheets that scatter light exiting the waveguide are sometimes used to shield or mitigate non-uniformity. However, this diffusion also results in the light being directed away from the good viewing axis. The result can be reduced in the overall brightness of the display along the good viewing axis, which is another measure of performance of the display device.

From a subjective point of view, a relatively small increase or decrease in overall brightness is not easily perceived by the user of the display device, such as discontinuous nonuniformity. However, display device designers are disappointed by even the smallest decrease in overall brightness, including a small decrease that can only be detected by objective lens measurements. This is closely related to the display brightness and the power requirements of the display. If the overall brightness can be increased without increasing the required power, the designer can actually distribute less power to the display device but achieve an appropriate level of brightness. In portable devices with charger power connections, this reproduces longer operating times.

The present invention relates generally to a backlight, and more particularly to a backlight comprising a waveguide formed of an optical structure on the surface of one or more lightguides.

1 is a perspective view of a lighting apparatus formed according to an embodiment of the present invention.

2 is a perspective view of an optical film incorporating a programmed pattern of optical structures in accordance with one embodiment of the present invention.

3 is a perspective view of an optical film incorporating a programmed pattern of optical structures in accordance with another embodiment of the present invention.

4 is a perspective view of an optical film incorporating a programmed pattern of optical structures in accordance with another embodiment of the present invention.

5 is a perspective view of a waveguide wedge incorporating a programmed pattern of optical structures in accordance with another embodiment of the present invention.

6 is a perspective view of a waveguide wedge incorporating an in-phase programmed pattern of optical structures in accordance with another embodiment of the present invention.

FIG. 7 is a sectional view taken along line 7-7 of FIG.

8 is a perspective view of a waveguide wedge incorporating an out-of-phase programmed pattern among optical structures in accordance with another embodiment of the present invention.

9 is a perspective view of a linear lens structure incorporating a programmed pattern of optical structures in accordance with another embodiment of the present invention.

Figure 10 is a schematic plan view showing a circular lens structure incorporating a programmed pattern of optical structures in accordance with another embodiment of the present invention.

FIG. 11 is a schematic perspective view showing the circular lens structure shown in FIG.

12 is a perspective view of an optical film incorporating a programmed pattern of an optical structure in accordance with an alternative preferred embodiment of the present invention.

Figure 13 is a perspective view of an optical film incorporating a programmed pattern of optical structures in accordance with an alternative preferred embodiment of the present invention.

Figure 14 is a perspective view of an optical film incorporating a programmed pattern of optical structures in accordance with an alternative preferred embodiment of the present invention.

Figure 15 is a perspective view of a waveguide incorporating a first programmed pattern of optical structures on the top surface and a second programmed pattern of optical structures on the bottom surface in accordance with a preferred embodiment of the present invention.

FIG. 16 is a side view showing the waveguide shown in FIG. 15. FIG.

Figure 17 is an exploded perspective view of a backlight according to a preferred embodiment of the present invention.

18 is an exploded perspective view of a backlight according to a preferred embodiment of the present invention.

FIG. 19 is a view showing the light output distribution for the backlight shown in FIG.

FIG. 20 is a diagram showing the light output distribution for the backlight shown in FIG.

Figure 21 is a side view of the backlight according to the prior art.

Fig. 22 is a side view showing the backlight according to the preferred embodiment of the present invention.

23 to 28 are side views illustrating various configurations of a backlight according to a preferred embodiment of the present invention.

According to the invention, optical elements such as waveguides, optical films or lenses are formed in a predetermined programmed pattern of the optical structure. The optical structure may be arranged to selectively correct for non-uniformity at the output of the optical element, or may be arranged to otherwise affect the performance of the display in any designed manner.

In a first aspect of the invention, an optically transmissive film having a first face, a second face, a first edge, and a second edge forms a plurality of optical structures formed on the first face. The plurality of optical structures are arranged on the first face in a predetermined pattern, each optical structure having at least one property selected from the group consisting of amplitude, period, and aspect ratio. Each characteristic has a first value for a first predetermined position on the film between the first edge and the second edge, the characteristic being different than the first predetermined position on the film between the first edge and the second edge. It has a 2nd numerical value different from a 1st numerical value with respect to a 2nd predetermined position on a film.

In another aspect of the invention, the structure according to the invention is part of a thick optical element, for example a waveguide wedge or slab. The structure is achieved on a thick element through injection molding, casting, compression molding or by bonding the film with the structure to a thick optical element.

Many advantages and features of the present invention will become apparent to one of ordinary skill in the art from the following detailed description of some preferred embodiments of the present invention with reference to the accompanying drawings in which like reference numerals refer to like elements throughout.

The present invention is described in some preferred embodiments, particularly waveguides or optical films suitable for use in backlight systems typically used in flat panel display devices such as laptop computer displays or desktop flat panel displays. However, the present invention is not limited to the application and one of ordinary skill in the art understands that it includes the use for any optical system that is visual, for example, a projection screen device and a flat panel television. It should be further understood that the present invention has application to small LCD display devices as found in cell phones, personal digital assistants (PDAs), pagers and the like. Thus, the embodiments described herein do not limit the broad technical scope of the present invention.

In FIG. 1, the illumination system 10 comprises a waveguide having a light source 12, a light source reflector 14, an output face 18, a rear face 20, an input face 21 and an end face 22. 16), a reflector 24 near the rear face 20, a first light redirecting element 26, a second light redirecting element 28 and a reflective polarizer 30. Waveguide 16 may be a wedge, a variant thereof, or a slab. As is well known, the purpose of the waveguide is to provide for distributing light from the light source 12 for a much larger area than the light source 12, in particular for substantially the entire area formed by the output surface 18. . Waveguide 16 performs this task better in a dense, thin package.

The light source 12 may be a CCFL that inputs light to the edge surface 21 of the waveguide 16, and the lamp reflector 14 may be a reflective film that wraps around the light source 12 forming the lamp cavity. The back reflector 24 is located near the rear face 20 behind the waveguide 16. The back reflector 24 can be an efficient back reflector, for example a diffuse reflective film or a specular reflective film.

In the embodiment shown, the edge-coupled light is transmitted from the input face 21 toward the end face 22 and is defined by total internal reflection (TIR). Light is emitted from the waveguide by the frustration of the TIR. Light rays confined within waveguide 16 have respective TIR bounces, increasing their angle of incidence with respect to the top and bottom wall planes due to the wedge angle. Thus, the light is no longer trapped by the TIR and as a result refracts from the output face 18 at the glancing angle. Some rays are emitted from the rear face 20. This light beam is reflected backwards by the back reflector 24 in and through the waveguide 16. The first light reinducing element 26 is arranged in a turning film that reinduces this light ray exiting the output face 18 along a direction substantially parallel to the preferred viewing direction.

1 and briefly as shown in FIG. 2, the first light redirecting element 26 may be a light transmissive optical film having a first face 32 and a first face 34. In turning film applications, the first face 32 is arranged as an input face and forms a prism 44, which refracts and reflects light exiting the waveguide 16 along a good viewing direction. Thus, the first face 34 is an output face. The prisms are commonly assigned U. S. Patent No. 09, entitled “Optical Film with Variable Angle Prism,” filed Oct. 8, 1999, which is a disclosure having a substantially uniform shape or expressly incorporated herein by reference. It may be a non-uniform shape as described in / 415,873.

Again, with respect to FIG. 1, the second light reinducing element 28 may not be required for all shapes of the lighting system 10. When included in the system 10, the second light reinducing element is a 3M commercially available (sold as BEFII or BEFIII) from a diffuser, a lenticular spreader or a Minnesota Mining and Manufacturing Company, eg, St. Paul, Minnesota. It may be a prism film which is a brightness improving film such as a brightness improving film product. The reflective polarizer 30 may be an inorganic, polymeric or cholesteric liquid crystal polarizer film. Suitable films are diffuse reflective polarizer film products (sold by DRPF) or mirror reflective polarizer film products (sold by DBEF), all of which are commercially available from the Minnesota Mining and Manufacturing Company. Moreover, at least the second light redirecting element 28 and the reflective polarizer 30 and potentially the first light redirecting element 26 may be combined into a single optical element. Jointly assigned US patent application Ser. No. 09 / 415,100, filed Oct. 8, 1999, entitled “Method of Increasing Brightness of Display Lighting and Display Lighting,” the disclosure of which is hereby expressly incorporated by reference. The arc describes some such combined optical structures.

In the case of a waveguide used for a backlight such as the waveguide 16, it is common that there is a non-uniformity of light output from the waveguide. This nonuniformity can often be concentrated near the input face 21. In order to mask the non-uniformity, which is generally regarded as a drawback, a diffuser is typically used that covers the output face of the waveguide. However, diffusers tend to reduce the overall brightness of the display and often cannot shield all drawbacks.

As described above, in the illumination system 10, the first light reinducing element 26 may be arranged in a turning film and have a structure as shown in FIG. 2. Again, for FIG. 2, the film contains a pattern 42 of optical structure 40 (prism) arranged to have a biphasic variable amplitude. In the application of the turning film, the pattern 42 is formed on the side which is the light input surface of the film. However, in some other applications described herein, the pattern 42 may be formed on the top and / or bottom surface of the wedge, slab or film. In the application of the turning film shown in FIG. 1, in addition to the prisms formed on the first face 32 of the first light redirecting element 26, the first face 34 may be formed of an optical structure.

Continuing with the description with reference to FIG. 2, the first light re-guiding element 26 has a first edge 36 and a second edge 38. The optical structure 40 extends from the first edge 36 toward the second edge 38 in the pattern 42. Each optical structure 40 may have a number of properties such as amplitude, period, and aspect ratio of peak 44 and valley 46. The pattern 42 may also have properties such as, for example, pitch, P, between the optical structures 40. The structure of Figure 2 shows that it has an amplitude change. In an application of the first light re-guiding structure 26, the grooves can be arranged such that the change in its amplitude is perpendicular to the light source 12 (FIG. 1).

2, the optical structure 40 is formed with a greater amount of amplitude change at the first edge 36, and this amplitude change decreases in magnitude toward the second edge 38. Observed within). Larger amplitude variations in the optical structure 40 produce more optical power along the groove axis due to the higher plane tilt. The optical power of this pattern is then reduced as a function of distance from the first edge 36. This arrangement of optical structure 40 and pattern is meaningful. As described, non-uniformity at the output of the waveguide 16 can be concentrated near the input surface 21 with less non-uniformity away from the input surface 21. Thus, the optical structure 40 and the pattern 42 are arranged to provide more diffusion near the first edge 36. In an application, the first edge 36 is disposed substantially near the input surface of the waveguide 16. The pattern 42 has a uniform or variable pitch, P, and the amplitude of the optical structure 40 can be reduced to zero towards the second edge 38. As will be described in more detail below, such a pattern can be created in any tool shape.

It should be understood that it is possible to determine the specific arrangement for the optical structure 40 and pattern 42 that best corrects the specific observed nonuniformity of the output of the waveguide 16 using ray tracing and other analysis techniques. . That is, the properties of one or more optical structures 40 and patterns 42 can be tailored to correct for certain nonuniformities. As described above, with respect to the first light re-guiding element 26, the optical structure 40 and the pattern 42 are adapted to shield the non-uniformity that may occur near the input surface 21. The optical power is provided at the output of the waveguide 16 near). The less or less strong non-uniformity is from the input face 21, the less optical power or light power is provided away from the input face 21 as is typically observed from the waveguide 16. In this way, optical power is provided where it is most needed to shield or mitigate non-uniformity, but less optical power is provided where there is less non-uniformity to shield. Moreover, optical power can be added virtually anywhere of the output of the waveguide by adding optical structures and / or changing the properties of the optical structures. Moreover, the addition of optical power need not be uniform. Instead, optical power can be added as needed into the discontinuous region of the waveguide output if it is necessary to shield the defect or to cooperate in producing a particular light effect.

Some waveguides include a pattern of diffuse dots on the back surface of the waveguide. Incident light into one of the dots is diffusely scattered by the diffusing dots and some of the reflected light exits the waveguide. Despite the diffusing nature of this method of emitting light from the waveguide, the pattern of dots can be visualized at the waveguide output by itself. Thus, additional diffusion is typically provided to conceal the dot pattern.

3, the film 50 has a surface 52 formed to include a plurality of optical structures 54 disposed in the pattern 56. The optical structure 54 is essentially arranged to replace the diffuse dot pattern to provide emission of light from the waveguide. Although shown as an ellipse in FIG. 3, the optical structure 54 is not collectively limited to any particular shape or to any particular shape within the pattern 56. Thus, optical structure 54 may be a prism, a line, a dot, a rectangle, an oval, a circle, a diamond, or any general shape or combination of shapes. Moreover, the optical structure 54 can be formed very small in size and even larger than the spaced dot in the diffuse dot pattern and can be spaced very closely within the pattern 56. For example, the optical structure has a typical size of that used for diffused dots, but is preferably less than the auraity of the human eye and can be spaced within approximately 50 to 100 m of each other. This very small size and close spacing of the optical structure 54 eliminates or reduces the need for diffusion at the output of the waveguide that is usually needed to conceal the pattern of diffusion dots.

4, the optical film 51 has a surface 53 on which a plurality of optical structures 55 are arranged in the pattern 57. As shown in FIG. In this embodiment of the present invention, the optical structure 55 is formed as a circle or a dot. FIG. 5 shows a waveguide edge 59 with a rear face 61 forming an optical structure 63 disposed in a pattern 65. FIG. Again, the optical structure is shown as a circle or a dot, but it should be understood that the optical structure can take virtually any shape.

The present invention allows and provides for a change in the slope of the waveguide at the fine level. That is, the slope of the waveguide can be locally increased or decreased by the addition of the optical structure at the fine level. When the beam strikes a larger amount of inclination, it is emitted from the waveguide more quickly than if it hits the nominal wedge angle.

Although the optical film was demonstrated so far, this invention is equipped with an application to a waveguide wedge itself. 6 and 7, the waveguide 60 has an input face 62, an output face 64 and a back face 66. As shown in FIG. Input surface 62 is arranged to be disposed near a light source (not shown) to provide a source of incident light to input surface 62. Incident light on the input face 62 is emitted from the output face 64 as a result of the failed TIR in the waveguide 60. As described above, it is common for non-uniformity in light output from waveguide 60, especially near input surface 62.

FIG. 7 shows the addition of optical power to the rear face 66 of the waveguide 60 and the adjustment of the intensity extending from the input face 62. As shown in FIG. 6, the rear face 66 forms an in-phase optical structure 68 which is arranged near the input face 62 to improve exit and tapered to zero from the input face 62. do. The pattern may also not be tapered, that is, it may change randomly and increase from zero to be constant over the entire surface or may be distributed in discrete areas. It is possible for the optical structure to be out of phase, such as the optical structure 68 'formed on the rear face 66' of the waveguide 60 'shown in FIG. The pattern of the optical structure may also be formed on the output face 64 separately or in connection with the pattern formed on the rear face 66, and this embodiment of the invention is described below in particular with reference to FIGS. 15 and 16. It should be understood that this is described in detail. Returning to this description, the purpose of providing optical structures is to perform the effect of minimizing non-uniformity of waveguide output wherever they occur. For example, the waveguide 60 shown in FIGS. 6 and 8 has a non-uniformity that appears mainly near the input face 62, which is an optical structure having more optical power near the input face 62. Suggest to add.

In particular with respect to FIG. 7, optical structure 68 may be formed on surface 72 of optical film 70. The optical film 70 may then be connected to the wedge structure of the waveguide 60 using ultraviolet (UV) curing, pressure sensitive or any other suitable adhesive. Alternatively, the wedge may be molded in bulk to include the optical structure 68 on the rear face 66.

As is generally better understood from the foregoing, in practice any shape of the optical structure can be formed in the optical film, which is connected to the waveguide or other bulk optical element, for example by bonding. For example, glare reduction, anti-wetout, Fresnels, and virtually any other structure that can be formed on the surface of the optical film can be easily replicated in the film and then the film can be Is connected to the optical element.

Film merged programmed optical structures can be fabricated using microreplication processes. In this manufacturing process, a master is formed, for example by cutting a pattern into a metal roll, which is used to produce a film by drawing, casting and curing, embossing and other suitable processes. . Alternatively, the film can be made by compression or injection molding, casting or roll forming. Preferred devices and methods for microreplication are described in commonly assigned US patent application Ser. No. 09 / 246,970, filed Feb. 9, 1999 under the name "Optical Film with Defect Reducing Surface and Method for Making the Same". The disclosure of which is hereby expressly incorporated by reference.

As an example of the above-described features of the present invention, with respect to FIG. 9, the linear Fresnel lens or prism 80 has a first surface 82 and a second surface 84 that are substantially flat. The second face 84 forms the lens structure 86 and an additional optical structure 88 is superimposed on the lens structure 86. Optical structure 88 has characteristics such as amplitude, period, and aspect ratio, which vary from the first edge 90 of lens 80 to the second edge of lens 80. Lens 80 may be formed in bulk or as shown in FIG. 9, lens structure 86 including optical structure 88 may be formed on film 94 connected to bulk optical substrate 96. . Depending on the application, the first face 82 may be arranged as an input face and the second face 84 may be arranged as an output face and vice versa.

10 and 11 show a schematic circular lens 81 comprising a first face 83 and a second face 85. The second face 85 is formed to include a lens structure 87, for example a circular Fresnel lens structure and an additional optical structure 89 is superimposed over the lens structure 87. Optical structure 89 has characteristics such as amplitude, period, and aspect ratio, which may vary, for example, from the outer circumference of lens 81 to the center of lens 81.

In FIG. 12, a film 100 containing a variable amplitude pattern 102 of an optical structure 108 formed using a “V” shaped cutting tool is shown schematically. Pattern 102 may be formed on the top and / or bottom surface of the film. As such, the pattern 102 may be formed in a wedge or slab. The film 100 has a first edge 104 and a second edge 106. The optical structure 108 is directed from the first edge 104 toward the second edge 106 disposed in the pattern 102. Is extended. Each optical structure 108 may have a number of characteristics such as amplitude, period, and aspect ratio. Pattern 102 may also have properties such as pitch, p, that define, for example, the spacing between optical structures 108. The optical structure 108 of FIG. 12 is shown with an amplitude change. In an application of the film 100, the grooves may be arranged such that the change in amplitude is perpendicular, parallel or at an angle with the light source of the waveguide merging film 100.

In FIG. 12, the optical structure 108 in the pattern 102 is formed with a larger amplitude at the first edge and decreases in amplitude towards the second edge 106. Larger amplitudes result in more optical power along the groove axis due to higher surface slopes. Next, the optical power of this pattern is reduced as a function of distance from the first edge 104. This arrangement of the optical structure 108 and the pattern 102 is important.

13 and 14, films 110 and 112 are shown, respectively. Each film 110, 112 has similar properties to film 100, and like reference numerals are used to describe similar elements therebetween. In contrast to the pattern formed by using an “V” shaped tool, the film 110 in FIG. 13 has a pattern of optical structure 116 formed using a tool having a curved or arc shaped shape. In FIG. 14, film 112 has a pattern 118 of optical structure 120 formed using a flat protrusion tool. Patterns 114 and 118 are arranged as described to provide optical power to the face or faces of film 110 and 112. It should be understood that virtually any tool shape may be used with a particular tool selected to achieve the desired amount and shape of optical power in the surface or surfaces of the film.

In the waveguide 121 shown in FIGS. 15 and 16, the first pattern 122 of the optical structure 124 is formed on the bottom surface 126 and the second pattern 128 of the optical structure 130 is formed of a wedge ( 134 is formed on the upper surface 132. For illustrative purposes only, the optical structure 124 is shown in FIG. 15 so that it only partially extends across the bottom surface 126, and the optical structure 130 extends only partially across the top surface 132. 15 is shown. It should be understood that optical structure 124 and optical structure 130 in most cases extend across entire bottom surface 126 and top surface 132, respectively. The first pattern 122 can be arranged to facilitate the extraction of light from the wedge 134 while the second pattern 128 can be arranged to shield non-uniformity in light output from the wedge. However, it should be understood that the pattern executed on the wedge 134 depends on the desired light output from the wedge 134. Moreover, as described above, patterns 122 and 128 may be first formed in an optical film that is later connected to the wedge, for example by bonding. In other structures, surfaces 122 and 128 are formed in the wedge by injection molding or casting.

As is understood from the above, according to a preferred embodiment of the present invention, the waveguide may be formed of an optical structure, for example a "V" groove, on one or both of the first side and the second side. In the case of the first side or the second side, the input face relates to the direction of the surface with respect to the light source. The optical structures can be spaced uniformly or randomly and can have a variety of other properties. Thus, the present invention has application to waveguides and backlight systems for various applications. One example of one application is a backlight system in which the waveguide emits light by failure of total internal reflection to form optical structures on the rear face and / or its output face. Another example is a backlight system with a waveguide that uses a dot pattern to emit light including an optical structure formed on one or both of the rear and output surfaces. These other examples are described in more detail below.

In FIG. 17, the backlight 140 is shown and includes a light source 142 near the input edge 143 of the wedge waveguide 144. The back reflector 146 is disposed near the rear surface 154 of the waveguide 144 and the turning film 148 is disposed near the input surface 150 of the waveguide 144. The back surface 154 is formed of the optical structure 152. The optical structure 152 may be a groove formed in the rear surface 154 and is shown as in FIG. The groove shown in Fig. 17 is a "V" type groove and has a prism angle of approximately 90 degrees, but prism angles in the range of 60 to 120 degrees can be used. Other shapes than the “V” shaped grooves may also be used for the optical structure 152. Moreover, each optical structure can be formed to have a height that varies from its nominal value along its length. This change has a wavelength that may be in the range of about 1 m to 1000 m, preferably about 140 m or less. Such a structure is disclosed and described in US patent application Ser. No. 09 / 025,183, filed Feb. 18, 1998 and co-assigned under the name "Optical Film", the disclosure of which is hereby expressly incorporated by reference. .

The optical structure 152 is shown in a direction substantially perpendicular to the light source 142. Optical structure 152 may be oriented horizontally to light source 142 or at an angle between 0 degrees and 90 degrees to light source 142.

Turning film 148 can be any suitable spectroscopic turning film. For example, turning film 148 may be formed as described in the US patent application described above under the name “Optical Film with Variable Angle Prism”.

The back surface 154 is formed to include the optical structure 152. This results in some additional light emitted from waveguide 144 through output surface 150 as compared to light emitted from rear surface 154. Some of the light exiting the back surface 154 meets the back reflector 146 and is reflected back through the waveguide 144 and the output surface 150.

In FIG. 18, backlight 140 'is shown similarly in structure to backlight 140 and like reference numerals are used to denote like elements. Reference numerals in the accent signs are used to indicate elements changed from the backlight structure shown in FIG. The backlight 140 'includes a light source 142 near the input edge 143 of the wedge waveguide 144'. The rear reflector 146 'is disposed near the rear surface 154' of the waveguide 144 'and the turning film 148 is disposed near the output surface 150' of the waveguide 144 '. The output surface 150 'is formed with an optical structure 152'. Optical structure 152 ′ may be a groove formed in output surface 150 ′ and is shown as in FIG. 17. The groove shown in Fig. 18 is a "V" type groove and has a prism angle of approximately 90 degrees, but prism angles in the range of 60 to 120 degrees can be used. Shapes other than "V" shaped grooves may also be used in the optical structure 152 '. Furthermore, each optical structure 152 ′ may be formed to have a height that varies from its nominal value along its length. This change in height has a wavelength that may be in the range of about 1 m to 1000 m, but for waveguide applications it is preferably about 140 m or less. Such a structure is disclosed and described in the aforementioned US patent application Ser. No. 09 / 025,183, entitled "Optical Film."

Optical structure 152 ′ is shown in a direction substantially perpendicular to light source 142 ′. The optical structure 152 ′ may be oriented parallel to the light source 142 ′ or at an angle between 0 degrees and 90 degrees to the light source 142.

Forming the output surface 150 'to include the optical structure 152' results in additional light emitted from the waveguide 144 through the rear surface 154 'as compared to the output surface 150'. Some light is also emitted from the output surface 150 '. Some of the light exiting the back surface 154 'meets the back reflector 146' and is reflected back through the waveguide 144 'and the output surface 150. Thus, it may be desirable to have a backlight 140 'to fix the back reflector 146' directly to the back surface 154 '. This can be done by stacking the back reflector 146 'to the back surface 154'. This arrangement for the back reflector 146 'is commonly assigned US patent application Ser. No. 09 / 414,124, filed Oct. 8, 1999, entitled "Waveguide with Directly Fixed Reflector and Method of Forming It". As disclosed and described in, these disclosures are expressly incorporated herein by reference. Alternatively, the back reflector can be formed on the back side using a deposition process. In embodiments where the reflector is fixed directly to the backside of the waveguide, it should be understood that the reflector should be highly efficient with a mirror and very low absorption.

As described above, the change is to reduce the characteristics of the optical structures 152, 152 'formed on each of the output or rear surfaces of the waveguide, for example, non-uniformity at the output of each of the backlights 140, 140'. It is added to the change in the amplitude of the optical structure. It is possible to provide a similar change to the optical structure by other methods such as bead blasting the optical structure, but forming a groove with the above-described change in prism height is controllable and predictable, It provides a preferred method of reducing nonuniformity in output.

FIG. 19 shows light output at the viewing cone disposed above the output of the backlight 140, ie light exiting the backlight 140 from the output surface of the turning film 148. What can be determined from the light output shown is on-axis brightness, maximum brightness, integration intensity, horizontal distribution or horizontal half angle and vertical distribution or vertical half angle. 20 provides a similar distribution for backlight 140 '. It can be clearly seen that the output of the backlight 140 'has a reduced horizontal distribution and a somewhat increased vertical distribution. Although the overall integrated intensity or total amount of output light from the backlights 140 and 140 'is approximately the same, the on-axis brightness and the maximum brightness are substantially increased for the backlight 140' compared to the backlight 140. As understood from FIGS. 19 and 20, the arrangement of the optical structures in each of the waveguides 140, 140 ′ affects the output of the backlight system. In the waveguide 144 'with the backlight 140', the optical structure 152 'formed on its top surface, further aiming of the light output of the backlight 140' is performed in comparison with the backlight 140. Moreover, because the optical structure 152 'can be formed with variable characteristics, the light output from the backlight 140' can be formed uniformly without other devices, such as optical films or diffusers, as described above.

There is an additional advantage associated with providing the optical structure 152 'including variable characteristics at the output surface 150' of the waveguide 140 '. One such advantage relates to the interface of the output face 150 ′ with the turning film 148. An optical structure 152 'is formed at the output surface 150' such that there are relatively fewer contact points between the prism of the turning film 148 and the output surface 150 '. This results in a reduction in optical defects, commonly referred to as wet-out. As discussed above, providing a change in the formation of the optical structure 152 'cooperates to shield defects in the output of the backlight that form the light output more uniformly. Thus, another advantage of providing the optical structure 152 'at the output surface 150' may be the removal of the diffuser film in the entire backlight system. As observed in FIG. 20, it is possible in accordance with the present invention to provide a backlight system that requires fewer sheets of optical film as compared to typical backlight systems, as the optical structure 152 ′ provides light aiming.

21 shows a waveguide 151, turning film 153, LCD display 154 and back reflector 155. FIG. Light is emitted from the waveguide 151 on both the upper surface 161 and the rear surface 157. It is possible that a strong Fresnel reflection 156 between the back reflector 155 and the back surface 157 captures a substantial portion of the light emitted from the back surface 157. This light eventually loses guidance inefficiently. To improve this situation, as shown in FIG. 22, the reflecting surface 158 of the back reflector 155 'is formed of the optical structure 159. As shown in FIG. The optical structure 159 may be a polyhedron, groove or other shaped structure. Optical structure 159 increases the efficiency by cooperating to reduce the specular element of reflection from back reflector 155 ′ and direct more light upward through waveguide 151. Suitable back reflectors including optical structures are the enhanced diffuse reflector (EDR) film products sold by 3M. One skilled in the art understands that the principles taught in FIG. 22 can be applied to virtually any backlight, without being limited to the backlight 140 and the backlight system according to the further preferred embodiments described herein.

Several modifications, improvements and modifications of the backlight system have been described above. Others are contemplated and are within the scope of the present invention. It should be understood that the particular device of the backlight system depends on the intended use thereof. To illustrate the adaptability of the present invention, several examples are shown and described in connection with FIGS.

Groove on the rear face of the waveguide

In FIG. 23, backlight 160 includes light source 162, wedge waveguide 164, back reflector 166, turning film 168, and optional additional optical film 170. Waveguide 164 has an output surface 165 and a rear surface 152 that form an optical structure similar to the optical structure 152 shown with respect to waveguide 144 of FIG. The optical structure may be formed directly into the waveguide 164 by injection molding or casting. Alternatively, the optical structure may be formed on a light transmitting film laminated to the rear surface 172 of the waveguide 164.

With additional optical structure formed on the rear surface 172 of the waveguide 164 additional light exits the waveguide 164 through the output surface 165 as compared to the rear surface 172. However, light exiting back surface 172 meets back reflector 166 and is reflected back through waveguide 164. Suitable reflectors including optical structures are grooved diffuse reflectors.

According to a further aspect of the backlight 160, the turning film 168 may be formed to include a diffusion structure on its output surface 176. Optional optical film 170 may be a brightness enhancing film such as the BEFIII optical film described above, a diffuse reflective polarizing film product (sold as DRPF) or a mirror reflective polarizing film product (sold as DBEF), all of which are Minnesota mining Available from N & Manufacturing Company.

Groove on the output surface of the waveguide

In FIG. 24, the backlight 180 includes a light source 182, a wedge waveguide 184, a back reflector 186, a turning film 188, and an optional optical film 190. Waveguide 184 has an output surface 192 formed of an optical structure similar to optical structure 152 'shown in relation to waveguide 144' shown in FIG. Waveguide 184 may be formed by injection molding or casting to include an optical structure on output surface 192. Alternatively, the optical structure may be formed on a light transmitting film laminated to the output surface 192 of the waveguide 184. Such a device potentially increases manufacturing flexibility and reduces manufacturing costs by simplifying mold design for waveguide 184. Instead of having one mold for each waveguide, the waveguide can be employed in accordance with the present invention by laminating the surface of the waveguide on an optical film formed of an optical structure.

With an optical structure formed on the output surface 192 of the waveguide 184, an additional amount of light exits the waveguide 184 from the output surface 192 compared to the amount of light exiting the waveguide from the rear surface 193. However, light exiting the rear surface 193 meets the rear reflector 186 and is reflected back through the waveguide 184. In order to ensure that a high percentage of light exiting the back surface 193 is reflected back through the waveguide 184, the back reflector 186 is preferably secured directly to the back surface 193. This can be done by laminating a mirror or mirror film on the back side 193 or by vapor coating the back side 193. The back reflector is reflective and has high efficiency when fixed directly to the back surface 193.

According to a further aspect of the backlight 180, the turning film 188 may be formed to include a diffuser structure at its output surface 196. Optical film 190 may be a brightness enhancing film such as the BEFIII optical film described above, a diffusely reflective polarizing film product (sold as DRPF) or a mirrored reflective polarizing film product (sold as DBEF), all of which are Minnesota mining and Commercially available from Manufacturing Company.

In FIG. 25, the backlight 220 includes a light source 222, a wedge waveguide 224, a back reflector 226 and a turning film 228. Waveguide 224 has an output surface 230 formed of an optical structure (not shown). The optical structure may have a variable pattern as described in the above-mentioned US patent application under the name "optical film" formed using a cutting tool of any suitable shape. The optical structure may be formed directly on the waveguide 224 by injection molding or casting, or alternatively, the optical structure may be formed on a light transmitting film laminated to the output surface 230 of the waveguide 224.

With an optical structure formed on the output surface 230 of the waveguide 224, an additional amount of light exits the waveguide 224 through the rear surface 232 compared to the amount of light exiting through the output surface 230. This light meets the back reflector 226 and is reflected back through the waveguide 224. Suitable reflectors may be grooved diffuse reflectors. Optical structures can also be provided to shield non-uniformity, thus eliminating the need for diffusers in the backlight system.

In addition, since the optical structure can provide aiming of light exiting the waveguide (see FIG. 20), it is possible to provide a backlight system that requires fewer sheets of optical film in accordance with the present invention as compared to typical backlight systems. In the embodiment shown in Figure 25, a single selective optical film that can be a diffuse reflective polarizing film product (sold as DRPF) or a mirror reflective polarizing film product (sold as DBEF) commercially available from the Minnesota Mining and Manufacturing Company. (238).

Regenerative backlight system

In FIG. 26, the backlight 200 includes a light source 202, a wedge waveguide 204, a rear reflector 206 and one or more additional optional optical films 210, 212. Waveguide 204 has a rear face 214 formed of an optical structure similar to optical structure 152 shown in relation to waveguide 144 of FIG. Optional structures may be formed directly in the waveguide 204 by injection molding or casting. Alternatively, the optional structure may be formed in a light transmitting film laminated to the back surface 214 of the waveguide 204.

An optional structure formed on the back surface 214 of the waveguide 204 facilitates the extraction of light from the waveguide 204. Thus, optional structures may allow removal of the diffuse dot pattern typically used to emit light from the waveguide. Some light exits the back surface 214 which meets the back reflector 206 and is reflected back through the waveguide 204. Suitable back reflectors are enhanced diffuse reflector (EDR) film products sold by 3M.

Removal of the dot pattern for emitting light from the waveguide 204 may reduce the need to add diffusion to shield the generation of the dot pattern at the output of the backlight 200. Optional optical films 210 and 212 may be the aforementioned BEFIII optical film product, a diffusely reflective polarizing film product (sold as DRPF) or a specularly reflective polarizing film product (sold as DBEF) and / or various It may be a brightness enhancing film such as a combination, and all are commercially available from Minnesota Mining and Manufacturing Company.

In FIG. 27, the backlight 240 includes a light source 242, a wedge waveguide 244, a back reflector 246, a diffuser 248, and first and second optional additional optical films 250, 252. The back reflector 246 is preferably applied to the rear face 254 of the waveguide 214 using a dot pattern adhesive as described in the above-mentioned US patent application under the name "waveguide with a directly fixed reflector". It is fixed. Thus, the adhesive is arranged in a typical dot pattern of the outgoing dot pattern.

Waveguide 244 has an output surface 255 formed of an optical structure (not shown). The optical structure may have a variable pattern as described above. The optical structure may be formed directly on the waveguide 244 by injection molding or casting or alternatively the optical structure may be formed on a light transmitting film laminated to the output surface 255 of the waveguide 244.

As described above, optical structures comprising variable patterns can eliminate the need for diffusers such as diffuser 248 to shield the dot pattern as well as other non-uniformities at the output of backlight 240. As such, diffuser 248 is optional. When used, the optional optical films 250 and 252 may comprise the aforementioned BEFIII optical film products, a diffusely reflective polarizing film product (sold as DRPF) or a specularly reflective polarizing film product (sold as DBEF) and / or arranged in a cross arrangement. Brightness enhancing films, such as various combinations thereof, may be commercially available from Minnesota Mining and Manufacturing Company.

Imitation-Wedge Backlight System

In FIG. 28, the backlight 260 includes a light source 262 and a pseudo-edge waveguide 264. Imitation-edge waveguide 264 includes a first side 266 and a second side 9268. The first face may be formed of an optical structure 270, such as the optical structure 152 described with reference to FIG. 17. The second face is formed of a multi-faceted groove structure 272 arranged parallel to the light source 262. The multi-sided groove structure 272 facilitates the emission of light from the waveguide by enhancing the failure of total internal reflection. Although not shown, the backlight 260 also includes a back reflector disposed near the second face 268.

The multi-sided groove structure 272 may have variable angular characteristics. Each individual polyhedron has a polyhedron angle. When the polyhedral groove structure 272 includes variable angular properties, the individual polyhedral angles vary from polyhedron to polyhedron. This arrangement of the multi-sided groove structure 272 can reduce the occurrence of non-uniformity at the output of the backlight 260.

Although waveguide 264 is shown as a slab structure, waveguide 264 may be a wedge. Moreover, the multi-sided groove structure 272 can be formed directly in the waveguide 264 by, for example, molding or casting, or the multi-sided groove structure can be formed in an optical film laminated to the slab or wedge waveguide. The multi-faceted groove structure can also vary in density as a function of distance from light source 262.

Other variations and other embodiments of the invention will be apparent to those skilled in the art in view of the foregoing. This description is described by way of example only for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The detailed structure and method may vary substantially within the spirit of the invention and the exclusive use of all changes coming within the scope of the appended claims is preserved.

Claims (35)

With waveguide, A light source disposed relative to the waveguide to direct light into the waveguide, An optical structure formed on one of an output face and a rear face of the waveguide and arranged to emit light from the waveguide, Turning film disposed near the output surface, A rear reflector disposed near the rear face, And the optical structure comprises a variable characteristic arranged to shield non-uniformity at the output of the waveguide. The backlight of claim 1, wherein the optical structure comprises a groove. The backlight of claim 2, wherein the grooves are arranged substantially parallel to the light source. The backlight of claim 2, wherein the grooves are arranged substantially perpendicular to the light source. The backlight of claim 2, wherein the grooves are arranged at an angle between about 0 degrees and about 90 degrees to the light source. The backlight of claim 2, wherein the groove has a shape selected from the group of shapes consisting of a V-shaped groove, a flat groove and an arc shape. The backlight of claim 1, wherein the back reflector is fixed directly to the back surface. The backlight of claim 1, wherein the back reflector is adhesively coupled to the back surface. The backlight of claim 1, wherein the back reflector is fixed to the rear surface by a dot bonding pattern. The backlight of claim 1, wherein the back reflector is formed to include an optical structure arranged to enhance reflection of light backward through the waveguide. The backlight of claim 1, wherein the waveguide is one of a wedge waveguide, a slab waveguide, and a dummy-wedge waveguide. The backlight of claim 1, wherein the optical structure is formed on an optical film laminated to the waveguide. The backlight of claim 1, wherein the waveguide forms an optical structure on each of the output surface and the rear surface. The backlight of claim 1, wherein the variable characteristic varies as a function of position on one of the output and rear surfaces. The backlight of claim 1, wherein the variable characteristic decreases linearly in magnitude from the first edge of the waveguide to the second edge of the waveguide. A light transmitting film having a first side and a second side; An optical structure formed on the first side and comprising variable characteristics arranged to shield non-uniformity in the output of the optical film, the variable characteristics varying as a function of the position of the variable characteristics on the first side Optical film. The optical film of claim 16, wherein the optical structure comprises a groove. The optical film of claim 16, wherein the grooves are arranged substantially parallel to the edge of the optical film. 17. The optical film of claim 16, wherein the grooves are arranged at an angle between about 0 degrees and about 90 degrees at the edge of the optical film. The optical film of claim 16, wherein the second surface of the film is formed to be fixed to one of an output surface and a rear surface of the optical film. 17. The optical film of claim 16, wherein the groove has a shape selected from the group of shapes consisting of a V-shaped groove, a flat groove and an arc shape. 17. The optical film of claim 16, wherein the variable characteristic decreases linearly in size from the first edge of the optical film to the second edge of the optical film. The first and second sides, An optical structure formed on one of the first and second surfaces, the optical structure including variable characteristics arranged to shield non-uniformity at the output of the lens, the characteristics varying as a function of the position of the optical structure on the surface; Lens characterized in that. 24. The lens of claim 23, wherein the lens comprises a Fresnel lens structure and the optical structure is formed in the Fresnel lens structure. The lens of claim 23, wherein the lens comprises one of a linear lens structure and a circular lens structure. Input, rear and output surfaces, An optical structure formed on one of the input surface, the rear surface, and the output surface, the optical structure including a variable characteristic arranged to shield non-uniformity at the output of the waveguide, the characteristic being a function of the position of the optical structure on the surface; Waveguide characterized by changing. 27. The waveguide of claim 26 wherein the optical structure is formed in a film and the film is secured to the face. 28. The waveguide of claim 27 wherein the film is secured to the face by bonding. 27. The waveguide of claim 26 wherein the optical structure comprises one of a V-shaped groove, a flat groove and an arc shape. 27. The waveguide of claim 26 wherein the optical structure comprises grooves arranged perpendicular to the input edge. 27. The waveguide of claim 26 wherein the optical structure comprises grooves arranged at an angle between 0 and 90 degrees on the input surface. 27. The waveguide of claim 26 wherein the optical structure comprises discrete optical structures dispersed in a pattern. 27. The waveguide of claim 26 wherein the optical structure is formed on each of the rear surface and the output surface. 27. The waveguide of claim 26 wherein the rear face is formed of a polyhedron and the optical structure is formed on the output face. 27. The waveguide of claim 26 wherein the variable characteristic varies as a function of the position of the variable characteristic on the face.