Patent Application
20130188364
The present invention relates to an optical sheet for a lighting device.
Essential criteria for a lighting device relate to whether energy efficiency of a lighting device can be improved with low power; whether a lighting device can be implemented in a thin structure; and whether a lighting device possesses environment-friendly features.
The above criteria play an important role not only for various lighting devices used for buildings, cars, and street lights but also for lighting devices used for backlight sources in LCDs.
As for a backlight source used for a liquid crystal display, LED (Light Emitting Diode) is replacing CCFL (Cold Cathode Fluorescent Lamp). A need for realizing high brightness as well as reducing production costs is a primary impetus for people to work on complementing light transmittance or optical sheets instead of reducing the number of light sources.
An optical sheet to meet recent trends requires high brightness and thus increases production costs. At the same time, since a plurality of optical sheets are required to satisfy specifications demanded by the recent trends, the overall reliability of a resulting device may deteriorate.
In particular, conventional optical sheets in current use cause optical loss due to total reflection during the process of receiving incoming light. The optical loss becomes severe as the number of optical sheets is increased.
Incident light L1 advances toward a lens pattern L2 formed on the surface of an optical sheet. As shown in the figure, total reflection occurs along the optical path and the reflected light comes out to the outside L3, leading to optical loss.
The present invention has been made in an effort to realize an optical sheet which minimizes total reflection by adjusting SAG of a lens pattern formed on a base member of the optical sheet, thereby providing an optical sheet and an optical unit with which a high brightness optical device can be implemented.
To solve the technical problem, one aspect of the present invention provides an optical sheet comprising a plurality of lens patterns formed on a base member, where the SAG (height H: lens diameter R) of the lens pattern ranges from 0.01 to 0.3.
In particular, the lens pattern can be formed in such a way that a plurality of lenses in the same size or different sizes is distributed in a uniform or in a random fashion.
The structure of the lens can assume a shape from among a circle, an ellipse, a prism, a lenticular shape, or an R-prism.
The diameter of the lens implemented in an optical sheet according to the present invention can range from 1 μm to 500 μm.
In another aspect of the present invention, the lens pattern formed on the base member has a curved part with negative curvature in the space formed between neighboring lenses.
In this case, the curved part can constitute a spherical or an aspheric surface with negative curvature, where the major axis a and the minor axis b of the surface range from 0.1 μm˜1000 μm at the exterior angle of a neighboring lens.
Also, an optical sheet according to the present invention can be formed in such a way that an angle constructed by at least one line connecting the respective centers of the lens patterns and a horizontal axis of LCD pixels formed in an upper part of the base member ranges from 5.5° to 9.5°.
The distance between neighboring lens patterns can range from 5% to 15% of diameter of the lens pattern. In this case, the lens pattern can be implemented by an optical sheet comprising multiple lens patterns of the same size, the diameter of which ranges from 5 μm to 25 μm.
In addition, the area in which the multiple lens patterns are formed according to the present invention can range from 70% to 95% of that of the base member.
The present invention can also provide an optical unit equipped with at least one or more optical sheets, where SAG (height: lens diameter) of multiple lens patterns formed on the base member ranges from 0.01 to 0.3.
It is preferred for the optical unit that the lens diameter of the optical sheet disposed at the top of a structure comprising multiple optical sheets ranges from 1 um to 30 um.
In addition, the lens pattern can be formed in such a way that a plurality of lenses of the same size or different sizes is distributed in a uniform or in a random fashion. As described above, the structure of the lens can assume a shape from among a circle, an ellipse, a prism, a lenticular shape, or an R-prism.
Furthermore, the lens pattern of the individual optical sheet constituting an optical unit according to the present invention can be formed in such a way to have at least one or more optical sheets where a curved part with negative curvature is formed in the space between neighboring lenses.
An optical sheet or an optical unit according to the present invention described above can be applied to a lighting device comprising a light transfer layer which guides incoming light from a light source to the front.
In this case, the optical sheet or the optical unit incorporating the light transfer layer can make more than half of the incident light have an incident angle ranging from 65 to 115 degrees within a lens pattern.
Still more, a lighting device according to the present invention can be made in such a way that an upper or a lower part of the optical sheet or the optical unit can comprises at least one or more reinforced films. The reinforced film exhibits at least one or more features among enhanced transparency, translucency, refraction, diffraction, diffusion, and brightness.
The present invention provides an optical sheet which minimizes total reflection by adjusting SAG of a lens pattern formed on a base member, thereby realizing a high-brightness lighting device.
In particular, an optical sheet or an optical unit according to the present invention not only minimizes total reflection but also realizes high brightness, thereby reducing the number of light sources and improving reliability.
The implementation of this document will be described in detail with reference to the following drawings in which like numerals refer to like elements.
The present invention provides an optical sheet which minimizes total reflection of incident light from a light source and enhances brightness by controlling a lens pattern formed on a surface of the optical sheet used for various lighting devices.
To this end, the present invention provides an optical sheet equipped with a plurality of lens patterns formed on a base member, where the SAG (height H: lens diameter R) of the lens pattern ranges from 0.01 to 0.3.
In what follows, a structure and an effect according to the present invention will be described in detail with reference to appended drawings. In referring to appended drawings, identical elements use the same reference number irrespective of a figure number in which the elements appear and description for the same element is omitted. The terminologies of first, second, and so on can be used to describe various elements but should not confine the elements. The terminologies are introduced only for identifying one element from the others.
(a) illustrates a cross section of an aspheric lens. (b) illustrates a cross section of a prism-shaped lens. (c) illustrates a cross section of a spherical lens. The lens shape is not limited to those listed above.
An optical sheet according to the present invention is equipped with a plurality of lens patterns 20 formed on a base member 10, where SAG (height H: lens diameter R) of the lens pattern ranges from 0.01 to 0.3.
A lens in this document indicates a lens, the shape of which is partially spherical, namely a spherically convex and concave lens—a concept including a three-dimensional shape such as a lenticular lens and a prism-shaped lens. In case of a convex pattern, the height denotes a normal distance from a bottom surface of a lens to the top of the lens. In case of a concave pattern, the height equals the normal distance from the aperture of a lens to the bottom part of the lens. A lens diameter R denotes a horizontal diameter of a bottom surface or an aperture of the lens.
The base member 10 can use such a material which can provide light transparency. The surface of the base member 10 is equipped with a plurality of lens patterns 20 carrying out light concentration, refraction in a tangential direction, diffusion, and so on. To this end, the lens pattern 20 can be formed either by processing the surface of the base member itself or by processing a separate lens pattern and disposing the lens pattern on the base member.
To be specific, since incoming light should penetrate the base member 10, the base member 10 can be formed by colorless and transparent synthetic resin. Although it is not particularly limited to the following, synthetic resin relevant to the base member 10 can include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather-proof polyvinyl chloride, active energy curable resin, and so on. Among others, active energy curable resin with excellent formability for a lens pattern such as ultraviolet curable resin and electron beam curable resin; or polyethylene terephthalate with excellent transparency and strength can be used. In addition, polyethylene terephthalate film, polyethylene naphthalate film, or polycarbonate film can be employed, on which a micro lens can be formed with ultraviolet curable resin.
In particular, the cross section of the lens pattern 20 formed on the top surface of the base member 10 according to the present invention can assume a shape from among a circle, an ellipse, a prism, a lenticular shape, or an R-prism, although it is not limited to those listed above. In addition, individual lenses comprising the lens pattern disposed on the top surface of the base member 10 can be formed in such a way that a plurality of lenses of the same size or different sizes is distributed in a uniform or in a random fashion. In other words, the lenses can be fabricated to be of the same size or to have a different size with each other. Furthermore, the spatial pattern of the lenses disposed on the surface of the base member can assume a polygonal grid pattern of the same shape. A polygonal grid pattern indicates that the cross sectional shape of a micro lens in a horizontal direction assumes a grid pattern such as a triangle, a rectangle, and so on. Each pattern can be composed of the same shapes or a combination of the same shapes and different shapes.
A characteristic feature of the present invention lies in minimizing total reflection of light which passes an optical sheet by manufacturing a lens in such a way that SAG (height H: lens diameter R) of the lens pattern ranges from 0.01 to 0.3. In particular, the diameter of the lens 10 described above can range from 1 μm to 500 μm.
In particular, an optical unit can be constructed by stacking up at least two or more optical sheets; or by disposing the optical sheets separately from each other. In order to minimize optical loss due to the conventional stacking of optical sheets, the diameter of the optical sheet disposed at the uppermost part of the optical unit is made to range from 1 μm to 30 μm, thereby minimizing a moire effect.
Also,
With reference to the figure, if light penetrates an optical sheet or an optical unit according to the present invention, total reflection is kept to a minimum and the SEG interval (X) providing high brightness ranges from 0.01 to 0.3. In other words, through the arrangement of a lens pattern formed on the base member, total reflection is minimized and high brightness can be realized.
As shown in the figure, implementing a plurality of lens patterns 20, 30 on the base member 10 is carried out in the same way as the embodiment described in
If the lens patterns 20, 30 formed on the base member 10 are taken into consideration, as shown in
To be specific, if the space between neighboring lenses 20, 30 is so formed that a virtual ellipse with a major axis in a vertical direction ‘a’ and a minor axis in a horizontal direction ‘b’ inscribes the space, the virtual ellipse meets the space at a lens first tangent point T1, a lens second tangent point T2, and a bottom part tangent point T3. Next, by filling the space except for the lens 20, the virtual ellipse, and the bottom part, a curved part 40 with negative curvature which passes the lens first tangent point, the lens second tangent point, and the bottom part tangent point can be formed.
By adjusting the lengths of the major axis ‘a’ and the minor axis ‘b’ of the virtual ellipse, a spherical shape can be obtained. The lengths of the major and the minor axis should be adjusted within a range of 0.1 μm˜1000 μm. If the length leaves the range above, brightness required for a lens cannot be achieved and Haze according thereto cannot be met.
c) illustrates a cross sectional view of a concave part of an optical sheet according to the present invention; an ellipse forms a virtual sphere by adjusting a major axis ‘a’ and a minor axis ‘b’ thereof; and a curved part 40 with negative curvature which passes the lens first tangent point, the lens second tangent point, and the bottom part tangent point is formed. The negative curvature formed between neighboring lenses provides an effect of diffusing light on the contrary to a lens with positive curvature collecting light. Therefore, distribution of light diffusion and improvement of light uniformity can be obtained, providing the same function carried out by a plurality of conventional films with a single optical sheet.
The curved part with negative curvature has been introduced only to illustrate the embodiment; a concave pattern can also be obtained from a method of applying pressure to the space between neighboring lenses by using a mask with a protruding pattern.
As described in the embodiment above, the third embodiment can also be implemented to minimize a moire effect by arranging a lens pattern for the SAG (height H: lens diameter R) of the lens pattern to range from 0.01 to 0.3.
An optical sheet 200 of the present embodiment comprises a base member 210 and a plurality of lens patterns 220 of the same size formed regularly on the base member.
When a lens pattern is arranged in a regular fashion, a moire effect occurs due to LCD pixels (not shown) formed in an upper part of an optical sheet and periodicity of the regular pattern shape. The moire effect refers to a visual experience where repetition of bright and dark patterns generated by light diffused through an optical sheet appears in the form of waves due to destructive and constructive interference determined by periodicity of a pattern formed regularly on the optical sheet and LCD pixel size.
A regular pattern shape according to the present invention removes the moire effect in three different ways.
As described in the first embodiment, it is preferred that the diameter of a lens pattern is determined within a range of 1˜500 μm while the SAG remains in the range of 0.01˜0.3 according to the present invention. More specifically, the moire pattern can be avoided with a dramatic effect by preparing the following specifications.
A first method for removing a moire effect is to adjust the size of a lens pattern 220 shown in
With reference to
Line 20 represents brightness of a regular lens pattern with a diameter of 25 μm or less while line 10 represents brightness of a conventional, irregular lens pattern. The horizontal axis represents a viewing angle. With reference to
A second method for removing a moire effect is to arrange the lens pattern to have lens frequency different from the spatial frequency of LCD pixels.
In the present invention, LCD pixels 510 of IPS type are illustrated but are not limited thereto. It is preferred that the internal angle θ of the LCD pixel 510 of IPS type is 149°. In this case, by inclining at least one line (40; hereinafter, it is called a reference line) among those lines connecting the respective centers of the lens patterns 530 by 7.5°±2° with respect to the horizontal axis 30 of the LCD pixel 510 (namely, 5.5° or more and 9.5° or less), the moire pattern can be removed.
As shown in
To increase the packing factor of the lens pattern 530, as shown in
A third method for removing a moire pattern is to maintain the separation between lens patterns at a predetermined distance.
With reference to
In addition, common to the three aforementioned methods for removing a moire pattern, by adjusting the packing factor and SAG of a lens pattern, controlling brightness and diffusion is made possible, which is not allowed for an optical sheet of conventional irregular patterns.
For example, by making the packing factor range from 70% to 95% for the respective methods, in other words, by making the area in which a lens pattern is formed range 70% to 95% of the area of the body part, brightness can be enhanced. Also, by keeping the SAG of a lens to range from 0.3 to 0.6, more preferably from 0.01 to 0.3 corresponding to the SAG range of a lens pattern of the present invention, brightness can be improved; by adjusting the packing factor and the SAG at the same time, the brightness can also be improved.
An optical sheet or an optical unit disposing two or more optical sheets according to the present invention can be used for various types of lighting devices. For example, the optical sheet or the optical unit of the present invention can be applied to lighting devices used in a car, a building, and public places; and backlight units used for liquid crystal display devices.
As shown in the figure, a lighting device can be equipped with a light transfer layer 120 which guides the light incoming from a light source 110 to the front. The lighting device can comprise an optical sheet 130 which is disposed in an upper part of the light transfer layer and can assume a structure of various types according to the present invention; and an optical unit which is a structure comprising a plurality of optical sheets.
To be specific, the light source 110 comprises an LED, a fluorescent lamp, an incandescent lamp, an electroluminescent light, and other similar light sources. The light source 110 can further comprise an arbitrary solid state lighting source not limited to the above.
In other words, the lighting device can comprise a light transfer layer 120 transferring light incoming from a light source 110 in a particular direction; and an optical sheet or an optical unit according to the present invention receiving the light incoming from the light transfer layer through reflection, refraction, diffusion, and diffraction and transferring the received light to the front. The lighting device can further comprise one or more reinforced films in an upper or a lower part of the optical sheet or the optical unit; and by doing so, possess at least one feature from among enhanced transparency, translucency, refraction, diffraction, diffusion, and brightness.
Put differently, if it is assumed that the structure shown in
If a lighting device comprising a light source, a light transfer layer, and an optical sheet according to the present invention are taken into account besides the structure shown in
In other words, the lighting device has a wide application, including dome lighting devices on the ceiling in a building, glove box lighting devices, floor lighting devices, map lighting devices, mirror lighting devices, decoration lighting devices, brake lighting devices in a rear window, and lighting devices in a car.
Specific embodiments have been described in the detailed description of the present invention. However, various modifications are also possible if the modifications belong to the scope of the present invention. The technical principles and the spirit of the present invention should not be limited to the embodiments of the present invention described above and should be understood by those as defined not only by the appended claims but also by the equivalent of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2010-0092299 | Sep 2010 | KR | national |
| 10-2010-0126494 | Dec 2010 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR11/01503 | 3/4/2011 | WO | 00 | 4/9/2013 |
