BACKGROUND

Cross-Reference to Related Applications

[1] This application claims the benefit of priority under 35 U.S.C. § 119 of Korean Patent Application Serial No. 10-2020-0128504 filed on October 6, 2020, the content of which is incorporated herein by reference in its entirety.

Field

[2] The present disclosure relates to a lighting device including at least two light guide substrates and, more particularly, to a lighting device that may obtain various ratios of light emission through one surface to light emission through the other surface while having superior durability and contamination resistance.

Description of Related Art

[3] A lighting device may be provided by disposing a light source on at least one side from among four sides of a light guide substrate. When the light source provides light to the light guide substrate, the light guide substrate may uniformly emit light through both surfaces (i.e. the top surface and the bottom surface) thereof using total internal reflection, thereby serving as a lighting device.

SUMMARY

[4] Various aspects of the present disclosure provide a lighting device, in which a light emission ratio between both surfaces is adjustable.

[5] Also provided is a lighting device that may protect a coating layer from scratches and which has superior contamination resistance.

[6] According to an aspect, a lighting device may include: at least two light guide substrates stacked on each other; and a light source providing light to the at least two light guide substrates. Each of the at least two light guide substrates may include: a substrate having a first surface and a second surface opposite to the first surface; and a light-scattering portion provided on at least one of the first surface and the second surface. At least one light guide substrate of the at least two light guide substrates may include at least one of a reflector pattern and an absorber pattern provided on at least one of the first surface and the second surface.

[7] According to another aspect, a lighting device may include: at least two light guide substrates stacked on each other; and a light source providing light to the at least two light guide substrates. Each of the at least two light guide substrates may include a substrate having a first surface and a second surface opposite the first surface and at least one light guide substrate among the at least two light guide substrates includes an engraved pattern provided in the first surface or the second surface.

[8] According to the present disclosure, the lighting device has a structure by which a light emission ratio between both surfaces may be adjusted. One surface of the lighting device may be brighter than the other surface by a combination of a plurality of light guide substrates, and the ratio may be changed significantly precisely.

[9] In addition, according to the present disclosure, the lighting device may have structure in which a coating layer or the like can be protected from scratches and which may have superior contamination resistance.

[10] The methods and apparatuses of the present disclosure have other features and advantages that will be apparent from or that are set forth in greater detail in the accompanying drawings, the disclosures of which are incorporated herein, and in the following Detailed Description, which together serve to explain certain principles of the present disclosure.

DESCRIPTION OF THE DRAWINGS

[11] FIG. 1 is a diagram illustrating a light guide substrate according to embodiments of the present disclosure;

[12] FIG. 2 is a diagram illustrating another light guide substrate according to embodiments of the present disclosure;

[13] FIG. 3 is a diagram illustrating another light guide substrate according to embodiments of the present disclosure;

[14] FIG. 4 is a diagram illustrating a light emission ratio between both surfaces of the light guide substrates illustrated in FIGS. 1 and 2;

[15] FIG. 5 is a diagram illustrating a lighting device according to embodiments of the present disclosure;

[16] FIG. 6 is a diagram illustrating another lighting device according to embodiments of the present disclosure;

[17] FIGS. 7 and 8 are diagrams illustrating lighting devices according to embodiments of the present disclosure;

[18] FIGS. 9 to 11 are diagrams illustrating lighting devices according to embodiments of the present disclosure;

[19] FIG. 12 is a diagram illustrating a lighting device according to embodiments of the present disclosure.

DETAILED DESCRIPTION

[20] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[21] FIGS. 1 to 3 illustrate light guide substrates according to embodiments of the present disclosure, and FIG. 4 illustrates a light emission ratio between both surfaces of the light guide substrates illustrated in FIGS. 1 and 2.

[22] A lighting device according to an embodiment of the present disclosure includes at least two light guide substrates, and FIGS. 1 to 3 illustrate embodiments of such light guide substrates, respectively.

[23] Light guide substrates 200 and 300 may each include atransparent substrate 101 having a first surface and a second surface opposite the first surface. The transparent substrate 101 may be formed from glass, poly(methyl methacrylate) (PMMS), acrylic resin, polycarbonate, or the like.

[24] In the present disclosure, at least one of a light-scattering material layer 201, a lightscattering pattern and an engraved pattern 203 is formed as a light-scattering portion in order to emit light through both surfaces of the substrate 101.

[25] In some embodiments, each of the light guide substrates 200 and 300 may include the light-scattering material layer 201 formed on the first surface. In some embodiments, the light- scatering material layer 201 may include a matrix forming a layer on the first surface and a plurality of light-scattering particles distributed in the matrix. In some embodiments, the matrix may include at least one from among polydimethylsiloxane (PDMS), silsesquioxane (SSQ), siloxane, acrylic resin, SiCh sol-gel, and water glass. In some embodiments, the light-scattering particles may include at least one from among SiCh, TiCh, BaTiCh. ZnO, ZrCX and SnCh, and may be in the form of powder or millbase.

[26] In some embodiments, each of the light guide substrates 200 and 300 may include the light-scattering patern (not shown) formed from a light-scatering material (e.g. TiCf. SiCh, ZnO, or BaTiCh), and formed on the first surface. The light-scatering material patern may be formed on the first surface in a variety of shapes, such as a dot patern (when viewed from above in the normal direction of the light guide substrate). In these embodiments, the cross-section of each of dots of the dot patern may have a variety of shapes, such as an oblong, a semiellipse, or a semicircle (when cut in the thickness direction of the light guide substrate).

[27] In some embodiments, the engraved patern 203 may be formed on the first surface of the substrate 101. The engraved pattern 203 may be formed on the first surface in a variety of shapes, such as a dot patern (when viewed from above in the normal direction of the light guide substrate). In these embodiments, the cross-section of each of dots of the dot pattern may have a variety of shapes, such as an oblong, a semiellipse, or a semicircle (when cut in the thickness direction of the light guide substrate). In some embodiments, the Ra value of the engraved patern may be 10 nm or more in a measurement range of lOpmxlOpm.

[28] In some embodiments, the light-scatering material layer 201 or the light-scattering material patern may be formed by mixing light-scatering particles (e.g. TiCh, SiCh, ZnO, or BaTiO?) with a matrix and applying to the entirety or a portion of the surface of the substrate 101 by spray coating, inkjet coating, slot die coating, screen-printing, or the like.

[29] In some embodiments, the engraved patern may be formed in the entirety or a portion of the surface of the substrate 101 using sandblasting. In some embodiments, an engraved patern was formed in Iris glass available from Coming Inc. using sandblasting. The following results may be obtained depending on the sizes of particles used in sandblasting. As will be apparent from Table 1 below, surface roughness may be adjusted significantly variously by adjusting the coarseness of particles and the time of sandblasting applied.

[30] Table 1

[31] All of the light-scattering material layer 201, the light-scattering material partem, and the engraved partem 203 described above may scatter light so that light may be uniformly emitted through each surface of the substrate 101. However, the characteristic of the engraved partem 203 is slightly different from those of the light-scatering material layer 201 and the light-scatering material patern. While the light-scatering material layer 201 and the light-scatering material partem allow similar amounts of light quantities to be emited through both surfaces of the substrate 101, the engraved pattern 203 allows a greater quantity of light to be emitted through the surface in which the engraved patern 203 is formed. Thus, the engraved patern 203 allows a light emission ratio between both surfaces to be adjusted even without a light reflector partem and a light absorber patern.

[32] In some embodiments, each of the light-scatering material layer 201, the light-scatering material pattern, and the engraved partem 203 may be used alone, or a combination of two or more thereof may be used. In some embodiments, the light-scatering material layer 201, the lightscatering material partem, and the engraved partem 203 may be formed on the second surface, in addition to the first surface. In addition, in some embodiments, the shape, distribution, or the like of those formed on the first surface may be the same as or different from the shape, distribution, or the like of those to be formed on the second surface.

[33] In some embodiments, as illustrated in FIG. 2, a light reflector patern or light absorber patern. 301 may be formed so that a light guide substrate 300 allows light emission through one surface to be different from light emission through the other surface.

[34] In some embodiments, the light guide substrate 300 may include a combination 304 of the light-scatering material layer 201 and the light reflector patern or light absorber pattern. 301 formed on the light-scattering material layer 201. The light reflector patern 301 may be formed from a light-reflecting material. In some embodiments, the light absorber patern. 301 may include a material having a reflectivity range from 1% to 40%, more particularly, from 1% to 30%. In some embodiments, the light reflector pattern 301 may include a material having a reflectivity range from 50% to 99.999%, more particularly, from 60% to 99.999%. Lambda950 available from PerkinElmer, Inc. was used in order to measure the reflectivity and absorptivity. The reflectivity and absorptivity of the first surface were measured separately from the reflectivity and absorptivity of the second surface, and the surfaces to be measured were disposed to be directed toward a light source. A measurement wavelength is within a visible light range of from 380nm to 780nm, and absorptivity A is calculated by measuring transmissivity T and reflectivity R (A=l-T-R). Here, a result may be corrected using a luminous efficiency function according to the wavelength. The absorptivity and the reflectivity described herein may be selectively measured with a wavelength according to a specific object, and may be measured with an average over the entire visible light range.

[35] In some embodiments, the light reflector patern 301 may be formed by the coating and curing of silver nano-ink. The light absorber patern. 301 may be formed from a light-absorbing material. In some embodiments, the light absorber patern. 301 may be formed by coating carbon black ink or silver nano-ink, followed by low temperature curing. The silver nano-ink may be used as a light reflector or a light absorber depending on curing conditions.

[36] In some embodiments, the light reflector patern or light absorber patern. 301 may be formed to have a variety of shapes, such as a dot pattern, on the light-scatering material layer 201 (when viewed from above in the normal direction of the light guide substrate). In these embodiments, the cross-section of each of the dots of the dot patern may have a variety of shapes, such as an oblong, a semiellipse, or a semicircle (when cut in the thickness direction of the light guide substrate). [37] In some embodiments, each of the light guide substrates 200 and 300 may include a light reflector pattern or a light absorber pattern, formed on the first surface on which the lightscattering material pattern is formed.

[38] In some embodiments, each of the light guide substrates 200 and 300 may include a light reflector pattern or a light absorber pattern, formed on the first surface in which the engraved pattern 203 is formed.

[39] In some embodiments, each of the light guide substrates 200 and 300 may include a light reflector pattern or a light absorber pattern, formed on the second surface.

[40] In some embodiments, each of the light reflector pattern and the light absorber pattern, may be formed alone or in a combination with the other. In some embodiments, the light reflector pattern may be formed on one surface of the light guide substrate, while the light absorber pattern, may be formed on the other surface of the light guide substrate.

[41] In some embodiments, the light reflector pattern and the light absorber pattern, may be arranged randomly or regularly.

[42] As illustrated in FIG. 4, when only the light-scattering material layer 201 is formed without the light reflector pattern and the light absorber pattern., the lighting device emits substantially the same quantities of light through both surfaces. However, when at least one of the light reflector pattern and the light absorber pattern. 301 is formed, the quantity of light emitted through one surface opposite the other surface on which at least one of the light reflector pattern 301 and the light absorber pattern. 301 is formed is greater than the quantity of light emitted through the other surface. (In FIG. 4, 3L, 2L, and 4L are illustrative only.) Accordingly, in the present disclosure, a light emission ratio between both surfaces of the lighting device may be adjusted using this feature. This feature will be described in detail with reference to FIGS. 5 and 6.

[43] FIG. 5 is a diagram illustrating a lighting device according to embodiments of the present disclosure.

[44] As illustrated in FIG. 5, the lighting device may include at least two light guide substrates 200 and 300 stacked on each other and light sources 401 providing light to the at least two light guide substrates 200 and 300.

[45] Since the lighting device including a plurality of light guide substrates includes a combination of the at least two light guide substrates 200 and 300, the strength thereof is increased. When the lighting device is used as a decorative shelf or a shelf inside a refrigerator on which goods are placed, the possibility of fracture of the lighting device may be significantly lowered, due to the increased strength thereof.

[46] In some embodiments, the light sources 401 may include at least two light sources 401 providing light to the at least two light guide substrates 200 and 300, respectively. In some of such embodiments, the at least two light sources 401 may be configured to be turned on or off independently of each other. In some embodiments, the light sources 401 may be light-emitting diodes (LEDs), but the present disclosure is not limited thereto.

[47] In some embodiments, each of the light guide substrates 200 and 300 may be disposed such that the light-scattering material layer 201, the light-scattering material pattern, the engraved pattern, the light reflector pattern 301, or the light absorber pattern. 301 faces an adjacent light guide substrate of the light guide substrates 200 and 300. That is, since the light-scattering material layer 201, the light-scattering material pattern, the engraved pattern, the light reflector pattern 301, or the light absorber pattern. 301 is located inside and protected by an adjacent light guide substrate of the light guide substrates 200 and 300, instead of being exposed externally, the lightscattering material layer 201, the light-scattering material pattern, the engraved pattern, the light reflector pattern 301, or the light absorber pattern. 301 may be prevented from being contaminated or damaged by a scratch. A typical material usable for the transparent substrate 101 is glass. Compared to a glass substrate, a coating layer has significantly low surface hardness, scratch resistance, or the like. The transparent substrate, such as a glass substrate, has a significantly high degree of surface hardness (9H or higher). However, in the case of the coating layer, the surface hardness of a scattering particle coating layer is usually lower than about 1H, except for a special inoiganic material coating layer. Even in a hard coating film, such as PMMA coating film, for protecting a transparent substrate, the surface hardness thereof ranges from 3Hto 4H in most cases. When the coating surface are directed to face each other using the plurality of light guide substrates 200 and 300, the coating surface is not exposed externally, and thus such a problem may be solved.

[48] In some embodiments, each of the light guide substrates 200 and 300 may be disposed to be spaced apart from the adjacent light guide substrates 200 and 300 using, for example, a spacer. In contrast, each of the light guide substrates 200 and 300 may be bonded to adhered or bonded to the adjacent light guide substrates 200 and 300 using an optically clear adhesive (OCA) film.

[49] In the lighting device illustrated in FIG. 5, light emitted through both surfaces may be adjusted to a variety of ratios, for example, 2L:4L, 3L:3L, and 5L:7L, depending on the turning on or off of the light sources 401 corresponding to the light guide substrate 200 or 300. When a greater number of light guide substrates 200 and 300 are combined, a light emission ratio between both surfaces may be adjusted more variously. In addition, even in the case in which the same total number of light guide substrates 200 and 300 are combined, the ratio may be adjusted by changing each of the number of light guide substrates 200 in FIG. 1 and the number of light guide substrates 300 in FIG. 2. In addition, even in the case that the light guide substrates 200 and 300 are combined in the same total number, the ratio may be adjusted by arranging the light guide substrates 200 and 300 to face in different directions.

[50] FIG. 6 is a diagram illustrating another lighting device according to embodiments of the present disclosure.

[51] An embodiment in which the lighting device includes four light guide substrates 300a, 300b, 300c, and 300d including a light-scattering material pattern or a light absorber pattern, is illustrated in FIG. 6. Here, a light emission ratio between both surfaces may be adjusted by changing the turning on or off of respective light sources 401 as in Table 2.

[52] Table 2

[53] In some embodiments, the light guide substrate having the engraved pattern formed on the first surface and the light guide substrate including at least one of the light reflector pattern and the light absorber pattern. 301, in which light emission intensity through one surface is different from light emission intensity through the other surface, may be flippably or rotatably assembled such that the directions in which the first surface and the second surface face are reversible. In this regard, in some embodiments, a process of detaching the light guide substrate to be flipped or rotated from the lighting device, flipping or rotating the detached light guide substrate, and then reattaching the light guide substrate to the lighting device may be necessary. As in following FIGS. 7 to 12, other embodiments may have a structure in which the light guide substrate is foldably coupled using a hinge.

[54] Accordingly, a light emission ratio between both surfaces in a lighting device may be adjusted as required. For example, the ratio may be changed by detaching a light guide substrate attached such that a first surface faces upwardly and a second surface faces downwardly, flipping or rotating the light guide substrate so that the first surface faces downwardly and the second surface faces upwardly, and then reattaching the light guide substrate.

[55] FIGS. 7 and 8 are diagrams illustrating lighting devices according to embodiments of the present disclosure.

[56] In some embodiments, at least one light guide substrate may be designed to be foldable using a hinge H, a latch E, or the like. Here, the number of hinges H and the number of latches E are not limited. A folding angle or a folding type is not limited. [57] When the light guide substrates are connected, the light guide substrates may be unfolded or folded using the hinge H (FIG. 7), or the light guide substrates may be fixed using the latch E (FIG. 8). This feature is applicable to a combination of a greater number of the light guide substrates, and the hinges H and the latches E may be added or removed as required.

[58] FIGS. 9 to 11 are diagrams illustrating lighting devices according to embodiments of the present disclosure.

[59] In some embodiments, a lighting device includes at least three light guide substrates, which are connected in series. Here, the at least three light guide substrates may be connected in series in a straight line as illustrated in FIG. 11, or may be connected in series along a non-straight line as illustrated in FIG. 12. A first light guide substrate among the at least three light guide substrates may be foldably connected to second and third light guide substrates, i.e. two other light guide substrates among the at least three light guide substrates, the second light guide substrate may be foldable to face the first surface of the first light guide substrate, and the third light guide substrate may be foldable to face the second surface of the first light guide substrate.

[60] As illustrated in the drawings, when four light guide substrates are connected, some of the hinges may be unfolded (FIG. 10) or all of the hinges may be unfolded (FIG. 11).

[61] FIG. 12 is a diagram illustrating a lighting device according to embodiments of the present disclosure.

[62] As illustrated in FIG. 12, the hinges and the latches may be disposed in intended positions, such that the lighting device may be freely unfolded or folded in a variety of manners.

[63] Although the specific exemplary embodiments of the present disclosure have been described hereinabove, the scope of the present disclosure shall be defined by the Claims appended hereto. Although the appended dependent claims are rendered to only refer to independent claims, embodiments in which the features of any dependent claim are combined or united with the features of other dependent claims shall fall within the scope of the present disclosure, unless inhibited in the context of the present disclosure.