JP2004507866A - Backlight with structured surface - Google Patents

Abstract

The backlight device includes an optical waveguide (16), a light source (12) positioned relative to the optical waveguide (16) to introduce light into the optical waveguide (16), and a turning film. An optical structure (40) is formed on one of the output surface (18) and the back surface (20) of the optical waveguide (16). The optical structure (40) is arranged to extract light from the optical waveguide (16). A back reflector (24) is located adjacent to the back surface (20). The optical structure (40) is formed to include a varying pattern arranged to mask non-uniformly at the output of the optical waveguide (16).

Description

[0001]
Background of the Invention
Field of the invention
The present invention relates generally to backlights, and more particularly, to backlights that include an optical waveguide formed with an optical structure on one or more surfaces of the optical waveguide.
[0002]
Description of related technology
Display devices that are illuminated from behind, such as liquid crystal display (LCD) devices, make extensive use of wedge-shaped optical waveguides. A wedge-shaped light guide couples light from a substantially linear source, such as a cold cathode fluorescent lamp (CCFL), to a substantially planar output. And the planar output is used to illuminate the LCD.
[0003]
One of the evaluation criteria of the performance of a display illuminated with light from behind is its uniformity. The user can easily perceive a relatively small difference in brightness of the display between one area of the display and an adjacent area. Even relatively small non-uniformities can be very annoying to display users.
[0004]
Surface diffusers or bulk diffusers, which scatter light entering the light guide, are sometimes used to mask or mitigate unevenly. However, this scattering also results in light being directed away from the preferred viewing axis. The end result is a reduction in the overall brightness of the display along the preferred viewing axis, which is another performance metric of the display device.
[0005]
From a subjective point of view, a relatively small increase or decrease in the overall brightness is not easily perceived by the user of the display as in the case of individual non-uniformities. However, display device designers are discouraged even by a minimal drop in overall brightness, including a very small drop that can only be perceived by subjective measurements. This is because the display brightness of the display and the required power are closely related. If the overall brightness can be increased without increasing the power requirements, the designer can actually allocate less power to the display device, but achieve an acceptable level of brightness. In the case of a battery operated portable device, this translates into a longer continuous operating time.
[0006]
Summary of the Invention
In accordance with the present invention, optical elements, such as optical waveguides, optical films, or lenses, are formed in a predetermined programmed pattern of optical structures. The optical structure may be arranged to selectively correct for non-uniformities in the output of the optical element, or to be otherwise arranged to achieve the performance of the display in a predetermined and planned manner. There is.
[0007]
In a first aspect of the present invention, a plurality of optical structures having a first surface, a second surface, a light-transmitting film having a first edge and a second edge formed on the first surface. Is formed. The plurality of optical structures are arranged in a predetermined pattern on the first surface, each optical structure having at least one feature selected from the group consisting of amplitude, period, and aspect ratio. Each feature has a first value for a first predetermined location on the membrane between the first edge and the second edge, and the characteristic is on the membrane between the first edge and the second edge. Has a second value different from the first value for a second predetermined position different from the first predetermined position.
[0008]
In another aspect of the invention, the structure according to the invention is part of a thick optical element, for example a wedge or slab of an optical waveguide. The structure is realized on a thick element by injection molding, casting, compression molding, or by bonding the structured film to a thick optical element.
[0009]
Many advantages and features of the present invention will become apparent to one skilled in the art from the following detailed description of several preferred embodiments of the invention, with reference to the accompanying drawings, in which like reference numerals refer to like elements.
[0010]
Detailed Description of the Preferred Embodiment
The present invention, according to some preferred embodiments, is used in backlighting devices commonly used in flat panel display devices, such as laptop computer displays or desktop flat panel displays, among others. Described by an optical film or optical waveguide, which is suitable for: However, the invention is not so limited in application, and those of ordinary skill in the art will recognize that the invention can be applied to virtually any optical device, for example, projection screen devices and flat panel televisions. It will further be appreciated that the present invention is applicable to small LCD display devices, such as those found in cell phones, personal digital assistants (PDAs), pagers, and the like. Accordingly, the embodiments described herein are not to be taken as limiting the broad scope of the invention.
[0011]
Referring to FIG. 1, a lighting device 10 includes a light source 12, a light source reflector 14, an optical waveguide 16 having an output surface 18, a back surface 20, an input surface 21 and an end surface 22, and a reflector adjacent to the back surface 20. 24, a first light redirecting element 26, a second light redirecting element 28, and a reflective polarizer 30. Optical waveguide 16 may be a wedge, a variant thereof, or a slab. As is known, the purpose of the light guide is to provide a distribution of light from the light source 12 over a much larger area than the light source 12, and more specifically, substantially over the area formed by the output surface 18. It is. More preferably, optical waveguide 16 performs these tasks in a compact, thin package.
[0012]
The light source 12 may be a CCFL that inputs light to the edge 21 of the light guide 16, and the lamp reflector 14 may be a reflective film wrapping around the light source 12 forming a lamp cavity. The rear reflector 24 is located behind the light guide 16 and adjacent to the back surface 20. The back reflector 24 may be an efficient back reflector, for example, a scattering or specular coating.
[0013]
In the embodiment shown, edge-coupled light travels from input surface 21 toward end surface 22 and is confined by total internal reflection (TIR). Light is extracted from the optical waveguide 16 by frustration of TIR. Light rays confined within the light guide 16 increase their angle of incidence on the top and bottom walls due to the wedge angle due to each TIR bounce. Thus, since the light is no longer confined by the TIR, the light will eventually refract and exit out of the output surface 18 at a glancing angle thereto. Some of the light rays are extracted from the back surface 20. These rays are reflected back by the back reflector 24 through the light guide 16. The first light redirecting element 26 is arranged as a turning film and redirects these rays exiting the output surface 18 in a direction substantially parallel to the preferred viewing direction.
[0014]
Referring to FIG. 1 and FIG. 2 briefly, the first light redirecting element 26 may be a light-transmitting optical film having a first surface 32 and a second surface 34. A first surface 32 is applied to the turning film, arranged as an input surface, and formed with a prism 44, which refracts and reflects light exiting the light guide 16 along a preferred viewing direction. Therefore, the second surface 34 is an output surface. The prisms may have a substantially uniform configuration or are described in commonly assigned U.S. patent application Ser. No. 09 / 415,873, filed Oct. 8, 1999. Such non-uniform features may be present, and the disclosure of this application is expressly incorporated herein by reference.
[0015]
Referring back to FIG. 1, the second light redirecting element 28 may not be required in all configurations of the lighting device 10. When included in lighting device 10, the second light redirecting element may be a diffuser, lenticular spreader or prismatic membrane, such as a 3M brightness enhancement available from Minnesota Mining and Manufacturing Company, St. Paul, Minn. It may be a brightness enhancing film, such as a film product (sold as BEFII or BEFIII). The reflective polarizer 30 may be an inorganic, polymer, or cholesterol liquid crystal polarizing film. Suitable films are scattering reflective polarizing film products (sold as DRPF) or specular reflecting polarizing film products (sold as DBEF), both of which are available from Minnesota Mining and Manufacturing Company. In addition, at least the second light redirecting element 28 and the reflective polarizer 30, and possibly the first light redirecting element 26, may combine to present a single optical element. U.S. patent application Ser. No. 09 / 415,100, filed Oct. 8, 1999, entitled "Display Illumination Devices and Methods for Enhancing Brightness in Display Illumination Devices," filed by the same assignee, is disclosed in US Pat. Optical structures are described and the disclosure of this application is expressly incorporated herein by reference.
[0016]
When an optical waveguide such as the optical waveguide 16 is used for a backlight, the light output from the optical waveguide usually has non-uniformity. These non-uniformities can often be concentrated near the input surface 21. A diffuser over the output surface of the light guide is typically used to mask the non-uniformly, which is usually considered a defect. However, diffusers tend to reduce the overall brightness of the display, and may not properly mask all of the defects.
[0017]
As described above, in the lighting device 10, the first light redirecting element 26 is arranged as a turning film and may have a structure as shown in FIG. Referring again to FIG. 2, the membrane includes a pattern 42 of optical structures 40 (prisms) arranged to have different varying amplitudes in phase. In the case of a turning film application, the pattern 42 is formed on the surface that is the light input surface of the film. However, in other applications, some of which will be described herein, the pattern 42 may be formed on the top and / or bottom of a wedge, slab, or film. In the case of the turning film application shown in FIG. 1, in addition to the prism formed on the first surface of the first light redirecting element 26, the second surface 34 may be formed of an optical structure. is there.
[0018]
2, the first light redirecting 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 a pattern 42. Each optical structure 40 may have a number of characteristics, such as amplitude, duration, and the aspect ratio of vertices 44 and depressions 46. Pattern 42 may also have features, such as, for example, pitch P between optical structures 40. An optical structure 40 having an amplitude change is shown in FIG. In the application of the first light redirecting element 26, the grooves may be arranged such that the change in amplitude is perpendicular to the light source 12 (FIG. 1).
[0019]
With continued reference to FIG. 2, in the pattern 42, it can be seen that the optical structure 40 is formed with a large amount of amplitude change at the first edge 36, which amplitude change decreases toward the second edge 38. The large amplitude changes in the optical structure 40 result in greater optical power along the groove axis due to the greater surface gradient. The light power of this pattern then decreases as a function of the distance from the first edge 36. This arrangement of the optical structure 40 and the pattern 42 is intended. As described above, the non-uniformity in the output of the optical waveguide 16 may be concentrated near the input surface 21, while the non-uniformity may decrease as the distance from the input surface 21 increases. Accordingly, the optical structure 40 and the pattern 42 are arranged such that more scattering occurs near the first edge 36. In an application, the first edge 36 will be located substantially adjacent to the input surface 21 of the light guide 16. The pattern 42 has a pitch P, which may be uniform or variable, and the amplitude of the optical structure 40 may decrease to zero toward the second edge 38. This pattern may be generated in any tool shape, as discussed in detail below.
[0020]
Using ray tracing and other analysis techniques, it is possible to determine a particular arrangement for the optical structure 40 and pattern 42 that best corrects for any observed non-uniformities in the output of the optical waveguide 16. That needs to be appreciated. That is, one or more of the features of optical structure 40 and pattern 42 may be tailored to correct for certain non-uniformities. As described above, in connection with the first light redirecting element 26, the optical structure 40 and the pattern 42 reduce the optical power to mask non-uniformities that may occur near the input surface 21. The output of the optical waveguide 16 was supplied near the input surface 21. As less or less severe non-uniformity is typically observed from the light guide 16 further away from the input surface 21, the light power is supplied less or further away from the input surface 21. is there. In this way, the light power is provided where uneven masking or softening is most needed, whereas less light power is provided where less masking non-uniformity is provided. Is done. In addition, optical power may be applied to virtually any output of an optical waveguide by adding optical structures and / or changing characteristics of the optical structures. Additionally, the addition of optical power need not be uniform. Instead, optical power may be applied to individual areas of the optical waveguide output, as needed, to mask the defect or to generate a particular optical effect, if necessary. There is.
[0021]
Some light guides include a pattern of scattered dots on the back of the light guide. Light incident on one of the dots is widely scattered by the scattering dots, such that a portion of this reflected light exits the optical waveguide. Despite the scattering properties of this method of extracting light from an optical waveguide, the pattern of dots may itself be visible at the optical waveguide output. Therefore, additional clutter is usually provided to hide the dot pattern.
[0022]
Referring to FIG. 3, a film 50 has a surface 52 formed to include a plurality of optical structures 54 arranged in a pattern 56. The optical structure 54 is arranged to effectively replace the scattered dot pattern to extract light from the optical waveguide. Although shown as an ellipse in FIG. 3, the optical structures 54 are not collectively limited to any particular shape, and they are not limited to any one particular shape in the pattern 56. Thus, optical structure 54 may be prisms, lines, dots, squares, ellipses, circles, diamonds, as well as almost any shape or combination of shapes. Further, the optical structures 54 may be made very small in size, may be located very close within the pattern 56, and may have much more than the dots in the scattering dot pattern. Sometimes. For example, the optical structures may have sizes up to the size typical for those used for scattering dots, but are preferably smaller than the sharpness of the human eye, and are separated from each other by about 50-100 m. It is arranged in. This very small size and close spacing of the optical structure 54 eliminates or reduces the need for scattering at the output of the optical waveguide, which is typically required to hide the pattern of scattering dots.
[0023]
Referring to FIG. 4, an optical film 51 has a surface 53 formed by a plurality of optical structures 55 arranged in a pattern 57. In this embodiment of the invention, optical structure 55 is formed as a circle or dot. FIG. 5 shows an optical waveguide wedge 59 having a back surface 61 formed by an optical structure 63 arranged in a pattern 65. Although the optical structures are again formed as circles or dots, it will be appreciated that the optical structures may exhibit virtually any configuration.
[0024]
The present invention allows and provides for micro-level changes in the slope of an optical waveguide. That is, the slope of the optical waveguide may be locally increased or decreased by the addition of a micro-level optical structure. If a ray strikes a larger positive slope, it will be extracted from the light guide sooner than if it strikes a nominal wedge angle.
[0025]
Although discussed above with respect to optical films, the present invention has application to the optical waveguide wedge itself. Referring to FIGS. 6 and 7, an optical waveguide 60 has an input surface 62, an output surface 64, and a back surface 66. Input surface 62 is arranged to be positioned adjacent a light source (not shown) to provide a source of light incident on input surface 62. Light incident on input surface 62 is extracted from output surface 64 as a result of blocked TIR in optical waveguide 60. As discussed above, light output from optical waveguide 60 typically has non-uniformities, especially near input surface 62.
[0026]
FIG. 7 illustrates the addition of optical power to the back surface 66 of the optical waveguide 60 and the adjustment of the intensity extending away from the input surface 62. As shown in FIG. 6, the back surface 66 is an in-phase optical structure 68 arranged to enhance extraction near the input surface 62 and to taper to zero away from the input surface 62. It is formed. The pattern may also be non-tapered, ie, unchanged over the surface, increasing from zero, randomly varying, or distributed in individual regions. It is also possible that the optical structures have different phases, such as the optical structure 68 'formed on the back surface 66' of the optical waveguide 60 'shown in FIG. It will be appreciated that the pattern of optical structures may also be formed on the output surface 64 either separately or with a pattern formed on the back surface 66. Such an embodiment of the present invention is described more fully below, particularly with reference to FIGS. Returning to this discussion, the purpose of providing an optical structure is to achieve the effect of minimizing optical waveguide output non-uniformities wherever they occur. For example, the optical waveguide 60 shown in FIGS. 6 and 8 may have a non-uniformity that appears primarily adjacent to the input surface 62, which is an optical structure having greater optical power near the input surface 62. Would suggest additional.
[0027]
With particular reference to FIG. 7, an optical structure 68 may be formed on the surface 72 of the optical film 70. The optical film 70 may then be bonded to the wedge structure of the light guide 60 using ultraviolet (UV) curing, pressure sensitivity, or some other adhesive. Alternatively, the wedge may be molded in bulk and include an optical structure 68 on the back surface 66.
[0028]
As will be more generally appreciated from the foregoing discussion, virtually any feature of an optical structure is formed in an optical film that can be coupled to an optical waveguide or other bulk optical element, for example, by bonding. is there. For example, glare reduction, anti-wet-out, Fresnel, and virtually any other structure that may form on the surface of an optical film is easily replicated on the film, and the film is bonded to another optical element Sometimes.
[0029]
Films that incorporate the programmed optical structure may be manufactured using a micro-reproduction process. In such a manufacturing process, a master is made, for example, by cutting patterns into metal rolls, and the master is used to produce a film by extrusion, molding and curing, embossing, and other suitable processes. used. Alternatively, the membrane may be manufactured by compression or injection molding, molding, or roll forming. A preferred apparatus and method for microcopying is described in commonly assigned U.S. patent application Ser. No. 09 / 246,970, filed Feb. 9, 1999, entitled "Optical Film with Defect-Reducing Surfaces and Method of Making Same." No. 54176 USA 9A), the disclosure of which is hereby expressly incorporated by reference.
[0030]
As an example of the above-described features of the present invention, referring to FIG. 9, a linear Fresnel lens or prism 80 has a first surface 82 and a second surface 84 that are substantially planar. The second surface 84 is formed by a lens structure 86, and an additional optical structure 88 is overlaid on the lens structure 86. The optical structure 88 has features such as amplitude, duration, and aspect ratio, which vary from a first edge 90 of the lens 80 to a second edge 92 of the lens 80. The lens 80 may be formed in bulk, or, as shown in FIG. 9, a lens structure 86 including an optical structure 88 may be formed on a film 94 that is bonded to a bulk optical substrate 96. is there. With this application, the first surface 82 may be arranged as an input surface and the second surface 84 may be arranged as an output surface, and vice versa.
[0031]
FIGS. 10 and 11 schematically show a circular lens 81 including a first surface 83 and a second surface 85. The second surface 85 is formed to include a lens structure 87, for example, a circular Fresnel lens structure, and an additional optical structure 89 is overlaid on the lens structure 87. Optical structure 89 has features such as amplitude, duration, and aspect ratio, which vary, for example, from the outer periphery of lens 81 to the center of lens 81.
[0032]
Referring to FIG. 12, a film 100 having a varying amplitude pattern 102 of an optical structure 108 formed using a “V” shaped blade is illustrated. The pattern 102 may be formed on the top and / or bottom of the film 100. Similarly, the pattern 102 may be formed in a wedge or slab shape. The membrane 100 has a first edge 104 and a second edge 106. The optical structure 108 extends from the first edge 104 located on the pattern 102 toward the second edge 106. Each optical structure 108 may have several characteristics, such as amplitude, duration, and aspect ratio. Pattern 102 may also have features such as, for example, a pitch P that defines the spacing between optical structures 108. The optical structure 108 of FIG. 12 shows a change in amplitude. In a membrane 100 application, the grooves may be arranged such that the change in amplitude is perpendicular, parallel, or at an angle to the optical waveguide incorporating the membrane 100.
[0033]
With continued reference to FIG. 12, it can be seen that in the pattern 102, the optical structure 108 is formed with a large amplitude at the first edge 104 and decreases in amplitude toward the second edge 106. Larger amplitudes produce more optical power along the groove axis due to larger surface gradients. The light power of this pattern then decreases as a function of the distance from the first edge 104. This arrangement of optical structure 108 and pattern 102 is intentional.
[0034]
Referring to FIGS. 13 and 14, membranes 110 and 112 are shown, respectively. Each membrane 110 and 112 has features similar to membrane 100, and the same reference numerals are used to represent the same elements between them. In contrast to the pattern created by using a “V” shaped tool, the membrane 110 of FIG. 13 has a pattern 114 of optical structures 116 formed using a tool having a curved or arcuate shaped structure. . The membrane 112 of FIG. 14 has a pattern 118 of optical structures 120 formed using a flat nose tool. Patterns 114 and 118 are arranged as described to provide optical power to the surfaces of films 110 and 112. It will be appreciated that virtually any tool feature may be used with the particular tool selected to achieve the desired amount and shape of light power at the surface of the film.
[0035]
In the optical 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 on the upper surface 132 of the wedge 134. For purposes of illustration only, optical structure 124 is shown in FIG. 15 and extends slightly partially across bottom surface 126, and optical structure 130 is shown in FIG. 15 and partially extends across top surface 132. extend. It will be seen that the optical structure 124 and the optical waveguide 130 often extend across the entire bottom surface 126 and optical structure 130, respectively. The first pattern 122 may be arranged to facilitate the extraction of light from the wedge 134, while the second pattern 128 masks the non-uniform light output from the wedge. May be placed. However, it will be appreciated that the pattern implemented at wedge 134 will depend on the desired light output obtained from wedge 134. Further, as described above, the patterns 122 and 128 may be initially formed on an optical film that is later bonded to the wedge, for example, by bonding. In another configuration, surfaces 122 and 128 are formed on the wedge by injection molding or molding.
[0036]
As will be appreciated from the foregoing discussion, in accordance with a preferred embodiment of the present invention, the optical waveguide is an optical waveguide, ie, a "V" shaped groove, formed on either the first surface, the second surface, or both. Sometimes. The input surface, whether the first surface or the second surface, is associated with the orientation of the surface with respect to the light source. The optical structures may be uniformly or randomly spaced, and may have various other features. Therefore, the present invention can be applied to optical waveguides and backlight devices in various fields. One example of an application is a backlight device that extracts light by frustration of total internal reflection, where the light guide is an optical structure formed on either the back surface and / or its output surface. Yet another example is a backlight device that uses a pattern of dots to extract light and has an optical waveguide that includes optical structures formed on either the back or output surface, or both. These and other examples are described in more detail below.
[0037]
Referring to FIG. 17, a backlight 140 is illuminated and includes a light source 142 adjacent an input end 143 of a wedge optical waveguide 144. A rear reflector 146 is disposed adjacent the back surface 154 of the light guide 144 and a turning film 148 is disposed adjacent the output surface 150 of the light guide 144. The back surface 154 is formed by the optical structure 152. Optical structure 152 may be a groove formed in back surface 154, such as that shown in FIG. The grooves shown in FIG. 17 are "V" shaped grooves and have a prism angle of about 90 degrees, although prism angles ranging from 60 degrees to 120 degrees may be used. Shapes other than “V” shaped grooves may also be used for optical structure 152. Further, each optical structure may be formed to have a height that varies from a nominal value along its length. This change may have a wavelength in the range of about 1 m to 1000 m, and preferably less than about 140 m. Such a structure is disclosed and described in commonly assigned US patent application Ser. No. 09 / 025,183 entitled “Optical Film” (filed Feb. 18, 1998, attorney identification number 53772 USA6A), which is hereby incorporated by reference. Is hereby expressly incorporated by reference.
[0038]
Optical structure 152 is shown oriented substantially perpendicular to light source 142. It will be appreciated that the optical structure 152 may be oriented parallel to the light source 142 or at an angle between 0 and 90 degrees relative to the light source 142.
[0039]
Turning film 148 may be any suitable spectral turning film. For example, turning film 148 may be formed as described in the aforementioned U.S. patent application entitled "Optical Film with Variable Angle Prism".
[0040]
Rear surface 154 is formed to include optical structure 152. This results in some additional light being extracted from the light guide 144 through the output surface 150 in light of the light extracted from the back surface 154. Some of the light exiting the back surface 154 will strike the rear reflector 146 and will be reflected back through the light guide 144 and the output surface 150.
[0041]
Referring now to FIG. 18, a backlight 140 'is shown, similar in configuration to the backlight 140, wherein the same reference numerals are used to indicate the same elements. Dashed reference numbers are used to indicate elements that are modified from the backlight configuration shown in FIG. The backlight 140 'includes a light source 142 adjacent the input end 143 of the wedge optical waveguide 144'. A rear reflector 146 'is disposed adjacent the back surface 154' of the light guide 144 ', and a turning film 148 is disposed adjacent the output surface 150' of the light guide 144 '. The output surface 150 'is formed by the optical structure 152'. Optical structure 152 'may be a groove formed in output surface 150', as shown in FIG. The grooves shown in FIG. 18 are "V" shaped grooves and have a prism angle of about 90 degrees, although prism angles ranging from 60 to 120 degrees may be used. Shapes other than "V" shaped grooves may also be used for optical structure 152 '. Further, each optical structure 152 'may be formed to have a height that varies from a nominal value along its length. This height change may range from about 1 m to 1000 m, but may have a wavelength that is preferably less than about 140 m for optical waveguide applications. Such a structure is disclosed and described in the aforementioned US patent application Ser. No. 09 / 025,183 entitled “Optical Film”.
[0042]
Optical structure 152 'is shown oriented substantially perpendicular to light source 142'. It will be appreciated that the optical structure 152 'may be oriented parallel to the light source 142' or at an angle between 0 and 90 degrees relative to the light source 142.
[0043]
Forming the output surface 150 'and including the optical structure 152' results in additional light being extracted from the light guide 144 through the back surface 154 'in the light of the output surface 150'. Some light is also extracted from output surface 150 '. Some of the light exiting the back surface 154 'will strike the rear reflector 146' and will be reflected back through the light guide 144 'and the output surface 150. Thus, with respect to the backlight 140 ', it may be desirable to attach the rear reflector 146' directly to the back surface 154 '. This may be achieved by attaching a back reflector 146 'to the back surface 154'. Such an arrangement for the rear reflector 146 'is described in commonly assigned US patent application Ser. No. 09 / 414,124 entitled "Optical Waveguides with Directly Attached Reflectors and Method of Making Same" (October 1999). 8th Application), the disclosure of which is hereby expressly incorporated by reference. On the other hand, the back reflector may be formed on the back surface using a vapor deposition process. In embodiments where the reflector is mounted directly to the back of the light guide, it will be appreciated that the reflector needs to be mirror-like and have very low absorption and very high efficiency.
[0044]
As described above, changes in the amplitude of the optical structure, for example, reducing variations, eg, non-uniformities in the output of the backlights 140 and 140 ', respectively, are produced by the optical structures 152 and 152' formed on the back or output surface of the optical waveguide, respectively. In addition to the features. By other methods, such as bead blasting the optical structure, it is possible to give a similar change in the optical structure, but to form the groove with the described change in prism height is controllable, It provides a predictable, and thus preferred, method of reducing non-uniformity in backlight output.
[0045]
FIG. 19 shows the light output at the viewing cone located above the output of the backlight 140, ie, the light exiting the backlight 140 from the output surface of the turning film 148. What may be determined from the illustrated light output is on-axis brightness, maximum brightness, integrated intensity, horizontal distribution or half-width, and vertical distribution or half-width. FIG. 20 gives a similar distribution of the backlight 140 '. It can clearly be seen that the output of the backlight 140 'has a reduced horizontal distribution and a slightly increased vertical distribution. The on-axis brightness and the maximum brightness are increased for the backlight 140 ′ compared to the backlight 140, but the overall integrated intensity, ie, the total amount of output light from the backlights 140 and 140 ′ is approximately the same. is there. It can be seen from FIGS. 19 and 20 that the arrangement of the optical structures within the light guides 140 and 140 ′ will each affect the output of the backlight device. In the backlight 140 ′, the optical structure 152 ′ is formed on the upper surface of the light guide 144 ′, and additional collimation of the light output of the backlight 140 ′ is achieved in the light of the backlight 140. Further, since the optical structure 152 'may be formed with varying features, as described above, the light output from the backlight 140' may be coupled to other elements, such as additional optical films or diffusers. May be evened without.
[0046]
There are further advantages associated with providing an optical structure 152 ', including varying features, at the output surface 150' of the optical waveguide 140 '. One such advantage relates to the interface of the output surface 150 'with the turning film 148. Since the optical structure 152 'is formed on the output surface 150', relatively few points of contact will be between the prism of the turning film 148 and the output surface 150 '. This can result in a reduction in optical defects commonly referred to as wet out. As mentioned above, providing a change in the formation of the optical structure 152 'also helps mask defects in the output of the backlight, making the light output more uniform. Thus, another advantage of providing the optical structure 152 'on the output surface 150' may be the removal of the scattering film throughout the backlight device. The optical structure 152 'provides light collimation, as can be seen from FIG. 20, so that in accordance with the present invention provides a backlight device that requires less sheets of optical film in light of a typical backlight device. It is possible to do.
[0047]
FIG. 21 shows an optical waveguide 151, a turning film 153, an LCD display 154, and a rear reflector 155. Light is extracted from both the upper surface 161 and the rear surface 157 of the optical waveguide 151. A strong Fresnel reflection 156 between the back reflector 155 and the back 157 can capture a significant portion of the light extracted from the back 157. This light is eventually lost, leading to inefficiency. To remedy this situation, the reflective surface 158 of the rear reflector 155 'may be formed with an optical structure 159, as shown in FIG. Optical structure 159 may be a surface, groove, or other molded structure. Optical structure 159 reduces the specular component of the reflection from back reflector 155 'and helps to direct more light upward through light guide 151, thus increasing its efficiency. A suitable back reflector that includes an optical structure is the Enhanced Scattering Reflector (EDR) film product sold by 3M. The principles taught in FIG. 22 apply to virtually any backlight, including but not limited to backlights 140 and backlight devices according to additional preferred embodiments described herein. Those skilled in the art will recognize that there are times.
[0048]
Several adaptations, enhancements, and changes to the backlight arrangement have been described above. Still others can be appreciated and are within the scope of the present invention. It will be appreciated that the particular arrangement of the backlight device will depend on the application for which it is intended. Some examples are shown and described in connection with FIGS. 23-28 to illustrate the applicability of the present invention.
[0049]
Groove on back of optical waveguide
In FIG. 23, a backlight 160 includes a light source 162, a wedge optical waveguide 164, a back reflector 166, a turning film 168, and an optional additional optical film 170. The light guide 164 has an output surface 165 and a back surface 172 formed of an optical structure similar to the light structure 152 shown in connection with the light guide 144 of FIG. The optical structure may be formed directly on the optical waveguide 164 by injection molding or molding. On the other hand, the optical structure may be formed on a light-transmitting film attached to the back surface 172 of the optical waveguide 164.
[0050]
As the optical structure is formed on the back surface 172 of the light guide 164, additional light exits the light guide 164 through the output surface 165 against the back surface 172. However, light exiting from the back surface 172 strikes the rear reflector 166 and is reflected back through the light guide 164. A suitable reflector containing an optical structure is a grooved scattering reflector.
[0051]
According to another aspect of the backlight 160, the turning film 168 may be formed to include a scattering structure on the output surface 176. The optional optical film 170 is a brightness enhancement film, such as the BEF III optical film described above, a scattering reflective polarizing film product (sold as DRPF), or a spherical reflective polarizing film product (sold as DBEF). Sometimes, all of these are available from Minnesota Mining and Manufacturing Company.
[0052]
Groove on output surface of optical waveguide
In FIG. 24, a backlight 180 includes a light source 182, a wedge optical waveguide 184, a back reflector 186, a turning film 188, and an optional other optical film 190. Optical waveguide 184 has an output surface 192 formed with an optical structure similar to optical structure 152 'shown in connection with optical waveguide 144' shown in FIG. Optical waveguide 184 may be formed by injection molding or molding to include an optical structure on output surface 192. On the other hand, the optical structure may be formed on a light transmitting film attached to the output surface 192 of the optical waveguide 184. Such an arrangement potentially increases manufacturing flexibility and reduces manufacturing costs by simplifying mold design for optical waveguide 184. Instead of having a unique mold for each light guide, the light guide may be adapted according to the present invention by laminating the surface of the light guide with an optical film formed by the optical structure.
[0053]
Since the optical structure is formed on the output surface 192 of the light guide 184, additional light exits the light guide 184 from the output surface 192 in light of the light exiting the light guide from the back surface 193. However, light exiting the back 193 strikes the rear reflector 186 and is reflected back through the light guide 184. The rear reflector 186 is preferably mounted directly to the back surface 193 to ensure that most of the light exiting the back surface 193 is reflected back through the light guide 184. This may be achieved by applying a mirror or specular film to the back surface 193, or by vapor deposition over the back surface 193. When mounted directly on the back 193, the back reflector needs to be specular and highly efficient.
[0054]
According to another aspect of the backlight 180, the turning film 188 may be formed to include a scattering structure on the output surface 196. The optical film 190 is a brightness enhancement film, such as the BEFIII optical film, the scattering reflective polarizing film product (sold as DRPF), or the spherical reflective polarizing film product (sold as DBEF). All of which are available from Minnesota Mining and Manufacturing Company.
[0055]
In FIG. 25, the backlight 220 includes a light source 222, a wedge optical waveguide 224, a back reflector 226, and a turning film 228. Optical waveguide 224 has an output surface 230 formed by an optical structure (not shown). The optical structure may have a varying pattern, such as described in the aforementioned U.S. patent application entitled "Optical Film", formed using any suitably shaped blade. The optical structure may be formed directly on the light guide 224 by injection molding or molding, or the optical structure may be formed on a light transmissive film that is affixed to the output surface 230 of the light guide 224.
[0056]
Since the optical structure is formed at the output surface 230 of the light guide 224, additional light exits the light guide 224 through the back surface 232 in light of the light exiting through the output surface 230. This light strikes the rear reflector 226 and is reflected back through the light guide 224. A suitable reflector may be a grooved scattering reflector. The optical structure also provides non-uniform masking, thus eliminating the need for a diffuser in the backlight device.
[0057]
Also, because the optical structure may also provide collimation of the light exiting the light guide (see FIG. 20), a backlight device that requires less optical films than a typical backlight device in accordance with the present invention. It is possible to provide. In the embodiment shown in FIG. 25, there is a single optional optical film 238, which is a scattering reflective polarizing film product (sold as DRPF), available from Minnesota Mining and Manufacturing Company, or spherical reflective polarizing film. It may be a membrane product (sold as DBEF).
[0058]
Reuse of backlight device
In FIG. 26, a backlight 200 includes a light source 202, a wedge optical waveguide 204, a back reflector 206, and one or more other optional optical films 210 and 212. Optical waveguide 204 has a back surface 214 formed with an optical structure similar to optical structure 152 shown in connection with optical waveguide 144 of FIG. The optical structure may be formed directly on the optical waveguide 204 by injection molding or molding. On the other hand, the optical structure may be formed on a light transmitting film attached to the back surface 214 of the optical waveguide 204.
[0059]
The optical structure formed on the back surface 214 of the light guide 204 facilitates the extraction of light from the light guide 204. Thus, the optical structure allows for the removal of the scattered dot pattern typically used to extract light from the light guide. Some light exits the back surface 214, which strikes the rear reflector 206 and is reflected back through the light guide 204. A suitable back reflector is the Enhanced Scattered Reflection (EDR) film product sold by 3M.
[0060]
Removing the dot pattern to extract light from the light guide 204 may reduce the need to add scattering to mask the appearance of the dot pattern at the output of the backlight 200. Optional optical films 210 and 212 are sold as the aforementioned BEFIII optical film products arranged in a crossed configuration, namely a scattering reflective polarizing film product (sold as DRPF), a spherical reflective polarizing film product (sold as DBEF). ), And / or various combinations thereof, all of which are available from the Minnesota Mining and Manufacturing Company.
[0061]
In FIG. 27, a backlight 240 includes a light source 242, a wedge optical waveguide 244, a back reflector 246, a diffuser 248, and first and second optional additional optical films 250 and 252. The back reflector 246 is attached to the back surface 254 of the light guide 214 using a dot-patterned adhesive, as described in the aforementioned U.S. patent application entitled "Light guide with directly mounted reflector". Is preferred. Accordingly, the adhesive is arranged in a dot pattern typical of a take-out dot pattern.
[0062]
Optical waveguide 244 has an output surface 255 formed by an optical structure (not shown). The optical structure may have a changing pattern, as described above. The optical structure may be formed directly on the light guide 244 by injection molding or molding, while the optical structure may be formed on a light transmissive film affixed to the output surface 255 of the light guide 244.
[0063]
The optical structure, including the changing pattern, eliminates the need for a diffuser, such as the diffuser 248, which masks not only the dot pattern, but also other non-uniformities in the output of the backlight 240, as described. There is. Therefore, the diffuser 248 is optional. When used, optional optical films 250 and 252 may include the aforementioned BEF III optical film products arranged in a crossed configuration, ie, scattering reflective polarizing film products (sold as DRPF), spherical reflective polarizing film products (DBEF). And / or various combinations thereof, all of which are available from the Minnesota Mining and Manufacturing Company.
[0064]
Simulated wedge backlight device
Now, referring to FIG. 28, the backlight 260 includes a light source 262 and a pseudo wedge optical waveguide 264. The pseudo wedge optical waveguide 264 includes a first surface 266 and a second surface 268. The first surface may be formed with an optical structure 270, such as the optical structure 152 described in connection with FIG. The second surface may be formed with a faceted groove structure 272 that is arranged to be parallel to the light source 262, such as the optical structure 152 described in connection with FIG. The faceted groove structures 272 facilitate extraction of light from the optical waveguide by enhancing total reflection frustration. Although not shown, backlight 260 will also include a back reflector positioned adjacent second surface 268.
[0065]
The faceted groove structure 272 may have variable angle features. Each individual facet has a facet angle. If the faceted groove structure 272 includes variable angle features, the individual facet angles will vary from facet to facet. This arrangement of the faceted groove structures 272 may reduce the appearance of non-uniformities in the output of the backlight 260.
[0066]
While optical waveguide 264 is shown as a slab structure, optical waveguide 264 may be wedge. Further, the faceted groove structure 272 may be formed directly in the optical waveguide 264, for example, by injection molding or molding, or the faceted groove structure 272 may be formed in an optical film affixed to a slab or wedge optical waveguide. May be formed. The faceted groove structure may also vary in density as a function of distance from the light source 262.
[0067]
Still other modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. This description is to be regarded as illustrative only and is intended to teach those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications falling within the scope of the appended claims is reserved.
[Brief description of the drawings]
FIG.
1 is a perspective view of a lighting device configured according to an embodiment of the present invention.
FIG. 2
FIG. 3 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to an embodiment of the present invention.
FIG. 3
FIG. 4 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 4
FIG. 4 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 5
FIG. 9 is a perspective view of a wedge of an optical waveguide incorporating a programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 6
FIG. 9 is a perspective view of a wedge of an optical waveguide incorporating an in-phase programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 7
FIG. 7 is a cross-sectional view taken along line 7-7 of FIG.
FIG. 8
FIG. 9 is a perspective view of a wedge of an optical waveguide incorporating a different phase programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 9
FIG. 4 is a perspective view of a linear lens structure incorporating a programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 10
FIG. 3 is a plan view of a circular lens structure incorporating a programmed pattern of an optical structure according to another embodiment of the present invention.
FIG. 11
11 is a schematic perspective view of the circular lens structure shown in FIG.
FIG.
FIG. 4 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to an alternative preferred embodiment of the present invention.
FIG. 13
FIG. 4 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to an alternative preferred embodiment of the present invention.
FIG. 14
FIG. 4 is a perspective view of an optical film incorporating a programmed pattern of an optical structure according to an alternative preferred embodiment of the present invention.
FIG.
FIG. 3 is a perspective view of an optical waveguide incorporating a first programmed pattern of optical structures on a top surface and a second programmed pattern of optical structures on a bottom surface, according to a preferred embodiment of the present invention.
FIG.
FIG. 16 is a side view of the optical waveguide shown in FIG. 15.
FIG.
1 is an exploded perspective view of a backlight according to a preferred embodiment of the present invention;
FIG.
1 is an exploded perspective view of a backlight according to a preferred embodiment of the present invention;
FIG.
FIG. 18 is a diagram showing a light output distribution of the backlight shown in FIG. 17.
FIG.
FIG. 19 is a diagram showing a light output distribution of the backlight shown in FIG. 18.
FIG. 21
FIG. 2 is a side view of a conventional backlight.
FIG.
FIG. 2 is a side view of a backlight according to a preferred embodiment of the present invention.
FIG. 23
FIG. 3 is a side view of various configurations of a backlight according to a preferred embodiment of the present invention.
FIG. 24
FIG. 2 is a side view of a configuration of a backlight according to a preferred embodiment of the present invention.
FIG. 25
FIG. 2 is a side view of a configuration of a backlight according to a preferred embodiment of the present invention.
FIG. 26
FIG. 2 is a side view of a configuration of a backlight according to a preferred embodiment of the present invention.
FIG. 27
FIG. 2 is a side view of a configuration of a backlight according to a preferred embodiment of the present invention.
FIG. 28
FIG. 2 is a side view of a configuration of a backlight according to a preferred embodiment of the present invention.

Claims (35)

An optical waveguide;
A light source disposed with respect to the optical waveguide, for introducing light into the optical waveguide;
A plurality of optical structures formed on one of the output surface and the back surface of the optical waveguide and arranged to extract light from the optical waveguide;
A turning film arranged adjacent to the output surface,
A rear reflector disposed adjacent to the back surface,
The plurality of optical structures have varying features arranged to mask the non-uniformity of the output of the optical waveguide.
Backlight. The backlight of claim 1, wherein the plurality of optical structures comprises a plurality of grooves. 3. The backlight according to claim 2, wherein the plurality of grooves are arranged substantially parallel to the light source. 3. The backlight according to claim 2, wherein the plurality of grooves are arranged substantially perpendicular to the light source. The backlight of claim 2, wherein the plurality of grooves are disposed at an angle between about 0 degrees and about 90 degrees with respect to the light source. The backlight according to claim 2, wherein the plurality of grooves have a shape selected from a group of shapes consisting of a "V" groove, a flat groove, and an arc. The backlight of claim 1, wherein the back reflector is mounted directly on 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 attached to the back by a sticky dot pattern. The backlight of claim 1, wherein the back reflector is formed to include a plurality of optical structures, the optical structures being arranged to enhance reflection of light returning through the optical waveguide. The backlight according to claim 1, wherein the optical waveguide is one of a wedge optical waveguide, a slab optical waveguide, and a pseudo wedge optical waveguide. The backlight according to claim 1, wherein the plurality of optical structures are formed on an optical film, and the optical film is stacked on the optical waveguide. The backlight according to claim 1, wherein the optical waveguide is formed with a plurality of optical structures on each of the output surface and the back surface. The backlight of claim 1, wherein the changing feature changes as a function of a position of one of the output surface and the back surface. The backlight of claim 1, wherein the amplitude of the changing feature decreases linearly from a first end of the optical waveguide to a second end of the optical waveguide. An optical film,
A light-transmitting film having a first surface and a second surface;
A changing feature formed on the first surface and arranged to mask a non-uniformity of the output of the optical film, wherein the changing feature is a feature of the changing feature on the first surface. A plurality of optical structures configured to vary as a function of position;
An optical film comprising: 17. The optical film of claim 16, wherein said plurality of optical structures comprises a plurality of grooves. 17. The optical film of claim 16, wherein the plurality of grooves are arranged to be substantially parallel to an edge of the optical film. 17. The optical film of claim 16, wherein the plurality of grooves are disposed at an angle between about 0 degrees and about 90 degrees with respect to an edge of the optical film. 17. The optical film of claim 16, wherein the second surface of the film is adapted to be attached to one of a back surface and an output surface of the optical film. 17. The optical film according to claim 16, wherein the groove has a shape selected from a group of shapes consisting of a "V" groove, a flat groove, and an arc. 17. The optical film of claim 16, wherein the amplitude of the changing feature decreases linearly from a first edge of the optical film to a second edge of the optical film. A lens,
A first surface and a second surface;
A variable feature formed on one of the first surface and the second surface and positioned to mask the non-uniformity of the output of the lens, the feature comprising an optical feature on the surface; A plurality of optical structures configured to vary as a function of the position of the structure;
A lens comprising: 24. The lens of claim 23, wherein the lens has a Fresnel lens structure, and wherein the plurality of optical structures are formed in the Fresnel lens structure. 24. The lens of claim 23, wherein the lens comprises one of a linear lens configuration and a circular lens configuration. An optical waveguide,
Input surface, rear and output surfaces,
A variable feature formed on one of the input surface, the back surface, and the output surface and arranged to mask a non-uniform output of the optical waveguide, the feature comprising: A plurality of optical structures configured to vary as a function of the position of the optical structure above;
An optical waveguide comprising: 27. The optical waveguide of claim 26, wherein said plurality of optical structures are formed in a film, said film being attached to said surface. 28. The optical waveguide of claim 27, wherein said film is attached to said surface by bonding. 27. The optical waveguide of claim 26, wherein the plurality of optical structures comprises one of a "V" groove, a flat groove, and an arc. 27. The optical waveguide of claim 26, wherein the plurality of optical structures comprises a plurality of grooves disposed perpendicular to the input edge. 27. The optical waveguide of claim 26, wherein the plurality of optical structures comprises a plurality of grooves disposed at an angle between 0 and 90 degrees with respect to the input surface. 27. The optical waveguide of claim 26, wherein the plurality of optical structures comprises a plurality of discrete optical structures dispersed in a pattern. 27. The optical waveguide of claim 26, wherein said plurality of optical structures are formed on each of said back surface and said output surface. 27. The optical waveguide of claim 26, wherein the back surface is formed with a plurality of facets, and wherein the plurality of optical structures are formed on the output surface. 27. The optical waveguide of claim 26, wherein the changing feature changes as a function of a position of the changing feature on the surface.