JP2024506949A - Backlight for tile-type partially laminated LCD display - Google Patents

Abstract

A backlight unit for use in a display device includes a light board having a first light source and a second light source. The backlight unit also includes a light guide positioned adjacent to the light board to distribute the light emitted from the first light source and the second light source. An auxiliary connector is disposed at the connector location between the first light source and the second light source to couple the light guide to the light board, and the optical properties of the light board or the auxiliary connector at the connector location are , unlike the optical properties at adjacent locations, the auxiliary connector becomes undetectable to the viewer of the backlight unit.

Description

Description of priority rights and related applications

This application is a priority under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 63/152,463, filed February 23, 2021, the contents of which are relied upon and incorporated herein by reference in their entirety. It is a claim of the benefits of rights.

The present disclosure relates to backlights for tiled partially laminated liquid crystal displays (LCDs). More particularly, the present disclosure provides tiled light boards and/or tiled light guides stacked together to produce a rugged backlight assembly with improved mechanical reliability and uniform brightness. (light guides).

In modern emerging display technologies, display trends such as trends in liquid crystal displays (LCDs) include increasing resolution, higher peak brightness and dynamic range (HDR), higher contrast, thinner set designs and narrower bezels. . To address these trends, displays may include direct backlighting, which may include a two-dimensional array of light sources placed directly behind the LCD panel. A two-dimensional array of light sources may include an array of light emitting diodes (LEDs). Various members can uniformly distribute light from the array of light sources across the display panel to meet display brightness, contrast and other requirements.

In some display designs, an array of light sources is distributed across the display using a light guide, which can include various components such as light guide plates, films, patterns, or other optical components and layers, to meet the requirements of the display. can be done. However, existing designs have several drawbacks. For example, one drawback is that it may be difficult to align the light guide with the array of light sources. Another example of a drawback is that existing backlight designs may include materials that do not allow for thinner and/or narrower bezels. Another example of a drawback is that existing backlight designs can suffer from mechanical reliability issues. Yet another example of a drawback is that existing designs may require complex and/or expensive manufacturing processes.

Therefore, it is easier to align the light guide with the light source, it is designed to allow for thinner display thicknesses and narrower bezels, it has improved mechanical reliability, and it uses a less complex and less expensive process. What is needed is an improved backlight that can be manufactured using

The present disclosure provides a backlight that can be used in a display with auxiliary connectors intermittently placed between the light guide plate and the light board at predetermined locations between the light sources on the light board. The optical properties of the auxiliary connector can be adjusted such that the auxiliary connector is undetectable to a viewer of the backlight unit. Additional connectors can improve the mechanical reliability of the backlight unit, while tiled light plates can be used to improve the accuracy and repeatability of properly aligning the light guide to the light board.

In one aspect, the present disclosure provides a backlight unit. According to some embodiments, a backlight unit for use in a display device includes a light board having a first light source and a second light source. The backlight unit also includes a light guide positioned adjacent to the light board to distribute the light emitted from the first light source and the second light source. A connector is disposed at the connector location between the first light source and the second light source to couple the light guide to the light board, and the optical properties of the light board or the connector at the connector location are The optical properties at the location make the connector undetectable to the viewer of the backlight unit.

In another aspect, the optical properties may include transparency of the connector.

In another aspect, the auxiliary connector can be colored gray to reduce the transparency of the auxiliary connector.

In another aspect, the auxiliary connector can be colored yellow to reduce blue light transmission.

In another aspect, the optical properties may include reflectance of the light board at the connector location.

In another aspect, the reflectance of the light board at the connector location may be lower than the reflectance of the light board adjacent to the connector location.

In another aspect, the light board can include a gray coating at the connector location to reduce the reflectance of the light board at the connector location.

In another aspect, the light board can include a yellow coating at the connector location to reduce blue light transmission at the connector location.

In another aspect, the light guide can include a first light guide tile including a first edge and a second light guide tile including a second edge, and the connector includes a first edge and a second light guide tile. is aligned to the edge of

In another aspect, the light board may include an array of light sources, with a connector disposed between adjacent light sources in the array of light sources.

In another aspect, a light guide can be coupled to the first light source and the second light source.

According to some embodiments, a backlight unit for use in a display includes a light board with a plurality of light sources and a first light guide tile and a second light guide tile arranged adjacent to each other. the first edge of the first light guide tile is disposed adjacent to the second edge of the second light guide tile, and the first edge of the first light guide tile and the second light guide tile are connected to each other. Define a tile seam between. The backlight unit may also include a connector disposed between the light board and the first light guide tile and the second light guide tile at the tile seam, the connector being arranged between the first light guide tile and the second light guide tile. Bond the second light guide tile to the light board.

In another aspect, a method of assembling a backlight unit is provided. According to some embodiments, the method includes providing a light board including a first light source and a second light source, and a light board at a connector location between the first light source and the second light source. It includes the step of placing the connector on the board. The method may also include applying a light guide plate to the light board and coupling the light guide plate to the light board at a connector location.

The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not necessarily drawn to scale. On the contrary, the dimensions of the various features have been arbitrarily expanded or decreased for clarity. Like reference numbers indicate like features throughout the specification and drawings.
Cross-sectional view of an exemplary backlight unit FIG. 2 is a top view of an example light board with an array of light sources, according to some embodiments. A cross-sectional view showing an exemplary backlight unit connected between a light board and a light guide plate. FIG. 2 is a cross-sectional view of an example backlight unit with an auxiliary connector between a light board and a light guide plate, according to some embodiments. FIG. 2 is a cross-sectional view of an example backlight unit with a tiled light guide plate, according to some embodiments. A cross-sectional view illustrating an exemplary backlight unit with an auxiliary connector between the light board and the tiled light guide plate of FIG. 4. FIG. 2 is a cross-sectional view of an example backlight unit with an auxiliary connector between a light board and another example tiled light guide plate, according to some embodiments. 5 is a cross-sectional view illustrating the example backlight unit of FIG. 4 with multiple optical layers, according to some embodiments. Flowchart illustrating an example method of manufacturing a backlight unit with an auxiliary connector between a light board and a light guide plate, according to some embodiments.

This description of example embodiments is intended to be read in conjunction with the accompanying drawings, which are to be considered a part of the entire written description. In the description, the words "lower", "above", "horizontal", "vertical", "above", "below", "above", "lower", "top" and "bottom" and their derivatives (e.g. Relative terms such as , "horizontally," "downward," "above," etc.) should be considered to refer to orientation as shown or described in the drawings under discussion. These relative terms are for convenience of explanation and do not require that the device be configured or operated in any particular orientation. Attachment, coupling, etc. terms, such as "connected" and "interconnected," refer to attachment, coupling, etc. Both in terms of rigid or rigid attachment or relationship, referring to a relationship that is fixed or attached to one another.

Hereinafter, for purposes of explanation, it is to be understood that alternative variations and embodiments of the embodiments described below are possible. It is also to be understood that the particular articles, compositions, and/or processes described herein are illustrative and should not be considered limiting. All documents mentioned in this disclosure are incorporated herein by reference.

In this disclosure, nouns include plural referents, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. It will be understood that when values are expressed as approximations, by use of the antecedent "about," the particular value forms another embodiment. As used herein, "about X" (where X is a numerical value) preferably refers, inclusively, to ±10% of the recited value. For example, the phrase "about 8" preferably refers to values from 7.2 to 8.8 inclusive. All ranges, where present, are inclusive and combinable. For example, if the range "1 to 5" is listed, the listed ranges are "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5". , "1-3 and 5", "2-5" and the like. In addition, where a list of options is positively given, such list should be interpreted to mean that any of the options may be excluded, for example by a negative limitation in the claim. Can be done. For example, if a range "1 to 5" is listed, the listed range is intended to include situations whereby any of 1, 2, 3, 4, or 5 is negatively excluded. Therefore, the enumeration "1 to 5" may be interpreted as "1 and 3 to 5, but not 2," or simply "2 not included." be. Any component, element, attribute, or step that is actively listed herein does not apply to any component, element, attribute, or step, whether or not such component, element, attribute, or step is listed as an option or if it is listed in isolation. It is intended that such exclusions may be expressly excluded in the claims, whether or not included.

The present disclosure provides a backlight unit with one or more auxiliary connectors between a light board and a light guide plate. This auxiliary connector can provide increased mechanical durability and can improve dimensional alignment between the light board and the light guide plate. Improved mechanical durability can reduce the backlight unit's propensity for mechanical failure over existing designs and can improve the efficiency and dimensional accuracy of the backlight unit. This, in turn, can reduce costs and improve the backlight unit's ability to provide uniform brightness in displays incorporating the backlight unit.

In some embodiments, the light guide plate of the backlight unit may include a panel made from glass. Unless the context clearly indicates otherwise, the terms "glass article" or "glass" as used herein shall be understood to include any article made in whole or in part from glass. Ru. Glass articles include monolithic substrates or laminates of glass and glass, glass and non-glass materials, glass and crystalline materials, and glass and glass ceramics (including amorphous and crystalline phases).

Glass articles, such as glass light guide plates, can be flat or curved, and transparent or substantially transparent. As used herein, the term "transparent" is intended to indicate that the article has a transmittance of greater than about 85% in the visible region of the spectrum (400-700 nm) at a thickness of about 1 mm. There is. For example, exemplary transparent glass panels have a transmittance of greater than about 85% in the visible light range, such as greater than about 90%, greater than about 95%, or greater than about 99% transmission, including all ranges and subranges therebetween. It may have transmittance. According to various embodiments, the glass article is less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, including all ranges and subranges therebetween. , or less than about 50% transmission in the visible region, such as less than about 20%. In certain embodiments, exemplary glass panels include greater than about 55%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, including all ranges and subranges therebetween. having a transmittance of greater than about 50% in the ultraviolet (UV) region (100-400 nm), such as a transmittance of greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95%, or greater than about 99%; Sometimes.

Exemplary glasses include, but are not limited to, aluminosilicate, alkali aluminosilicate, borosilicate, alkali borosilicate, aluminoborosilicate, alkali aluminoborosilicate, and other suitable glasses. It will be done. Non-limiting examples of available glasses suitable for use as light guides include, for example, IRIS(TM) from Corning Incorporated, and GORILLA(R) glass. The glass article may be toughened, if desired. In some embodiments, the glass article is mechanically engineered by exploiting the mismatch in coefficients of thermal expansion between parts of the article to create a region of compressive stress and a central region exhibiting tensile stress. May be strengthened. In some embodiments, the glass article may be thermally strengthened by heating the glass above its glass transition temperature and then rapidly cooling. In some other embodiments, the glass article may be chemically strengthened by ion exchange.

Referring to FIG. 1, an exemplary backlight unit 100 is shown. The backlight unit 100 can be used for, for example, a liquid crystal display (LCD). Some LCDs have brightness, contrast, and other requirements that can be met using direct backlight units. Direct backlight units often include a two-dimensional array of light sources. A two-dimensional array of light sources can be arranged as a number of light emitting diodes (LEDs) placed on a printed circuit board (PCB). Such a PCB or light board delivers light towards the viewer of the display and is located behind the panel of the display. The light emitted from the light board can be evenly distributed using a light guide. In this way, the display can be illuminated according to various requirements of the display such as brightness, contrast, etc.

In the example shown in FIG. 1, backlight unit 100 may include a light board 102 and a light guide 104. The light board 102 may include a number of light sources 106 arranged on the surface of the light board 102 facing the viewer when the backlight unit 100 is used for a display. Light source 106 may be, for example, an LED. Light source 106 can be attached to mounting board 108. Mounting board 108 can be, for example, a printed circuit board (PCB) that can deliver power to light source 106. Light board 102 may also include a back reflector 110 located on the same surface of mounting board 108 as light source 106 . Light guide 104 may be positioned adjacent light source 106. Light guide 104 may include various features and/or layers that can distribute light emitted from light source 106. The light guide 104 distributes the light emitted from the light source 106 such that the light is evenly distributed across the light guide 104 such that the position of the light source is undetectable to the human eye when the display is viewed. can be done. Light guide 104 may include, for example, a printed reflector 118 positioned opposite light source 106 on a surface of light guide 104. The printed reflector 118 can reflect the light emitted from the light source 106 such that no localized bright spots appear over each location of the light source. Light guide 104 may also include various light extractors 120 that can be placed on the surface of light guide 104. Light extractor 120 may be a dot, indentation, or other feature that can be printed, etched, or otherwise deposited or formed on the light guide. Light extractors 120 can be distributed along light guide 104 to evenly distribute light across the light guide.

As shown in FIG. 1, light emitted from light source 106 (as indicated by arrow 122) is refracted, reflected, or otherwise guided within light guide 104 to exit light source 106. of light can be distributed across the light guide 104. The light guide 104 may include a light guide plate 124 that may be made of a suitable material to guide light emitted from the light source. In some examples, light guide plate 124 can be made from a glass material. The size and reliability requirements of modern displays have made glass the preferred material for light guide plates. The thermal and mechanical properties of glass allow the backlight unit 100 to be thinner and larger than those with light guide plates 124 made from other materials, such as polymers or other suitable plastic materials. It can be designed and manufactured to be dimensionally stable. A glass light guide plate allows the bezel of an LCD to have a smaller overall width than an LCD incorporating a backlight unit with a light guide made from a non-glass material.

The backlight unit 100 shown in FIG. 1 may represent a part of a backlight unit. As can be seen, the backlight unit 100 can be reproduced in different profiles, such that the backlight unit 100 can include multiple light sources 106. One such example is shown in FIG. In that example, light board 200 may include a mounting board 202, such as a PCB, that can deliver power to LEDs 204. As can be seen, the light board 200 may include a number of LEDs 204 that can be arranged into an array of LEDs in multiple rows and columns. Light board 200 can be any suitable size needed to illuminate the LCD. As can be seen from the figure, the light board 200 includes 20 LEDs 204. In other examples, light board 200 may include more or fewer than 20 LEDs. In some displays, it is not uncommon for light board 200 to include hundreds of LEDs. For example, the light board 200 can be used for displays having a diagonal size of 80 inches (approximately 200 cm) or more. In such examples, light board 200 may include 900 or more LEDs. For each LED, the backlight unit may have the structure shown in FIG. 1, where the light guide is placed on top of the light board 200.

In designs with multiple light sources 106, the light guide plate 104 needs to be carefully positioned and secured relative to the light board 102. As can be seen, the reflector 118 needs to be positioned relative to the light source 106 to ensure that the management of the light in the light guide produces a uniform light distribution in the light guide 104. If there is excessive misalignment between the reflector 118 and the light source 106, there may be bright spots or other non-uniformities in the backlight unit 100 called mura. To minimize mura effects, the alignment of the light guide 104 with respect to the light board 102 should be carefully controlled during manufacturing of the backlight unit 100. As the number of light sources 106 increases, it becomes more difficult to ensure proper alignment between light guide 104 and light board 102.

One potential solution for making the assembly and alignment of the light guide 104 relative to the light board 102 easier to control and repeatably achieved within proper tolerances is to may be divided into tiles. In such an exemplary design, rather than having one light guide 104 with one light guide plate 124 having the size of the entire display screen, the light guides 104 are arranged in separate tiles that are placed adjacent to each other. Can be divided. The light guide tiles can have the external dimensions of the entire display screen when assembled together. Such designs may also include a light board 102 made from multiple tiled light boards assembled together. Such a tiled structure allows individual tiles to be adjusted relative to each other to ensure proper alignment between the light guide tiles and/or light board tiles. In various examples, light guide 104 can be made from multiple light guide tiles assembled into a one-piece light board. In another example, one light guide plate can be attached to a light board made from multiple light board tiles. In yet other examples, each of the light guide and light board can be made from multiple light guide tiles and multiple light board tiles, respectively. Such tiled designs are further described in US Provisional Patent Application No. 63/017,078, filed April 29, 2020, the contents of which are incorporated herein in their entirety.

Another problem that can arise in the assembly of direct backlight units is the mechanical durability and reliability of the backlight unit. In some designs, the backlight unit needs to be very thin to be assembled into a thin or ultra-thin backlight unit for assembly into a thin or ultra-thin LCD device. Such a thin or ultra-thin backlight unit may have a total thickness t (see FIG. 1) of about 1 mm to about 5 mm. The total thickness t in the example of FIG. 1 is shown without additional light diffusers, layers, and membranes such as BEF, DBEF. The additional thickness of these light diffusers, layers and/or films may add about 0.5 mm to about 3 mm to the total thickness of the backlight unit. In such low-profile and/or ultra-thin designs, light guide plate 124 and/or mounting board 108 may have a thickness of less than about 1 mm. In other designs, light guide plate 124 and/or mounting board 108 may have a thickness of less than about 0.5 mm.

Referring now to FIG. 3, another example backlight unit 300 is shown. Backlight unit 300 is similar in many respects to backlight unit 100 described above. As shown, the backlight unit 300 includes a light board 102, a light source 106, and a light guide 104. As shown in this example, light guide 104 may be secured to light board 102 using a quantity of optically clear adhesive (OCA) 302. Since the light source 106 can extend above the surface of the light board, the OCA 302 can be applied to the light source 106. In such an example, light guide 104 is coupled to a light board at each location of light source 106. The OCA can be applied to the surface of the light source that faces the light guide 104. In addition, the OCA may be present around each light source 106 such that the application area of the OCA may be larger than the footprint of the light source 106.

Light guide 104 and light board 102 may be attached to each other using a variety of suitable methods and processes. In one example, light guide 104 and light board 102 are laminated together using an optically clear adhesive. Although the light guide 104 and light board 102 can be manufactured to have substantially flat surfaces, neither the light guide 104 nor the light board 102 are completely flat. The light guide 104 and the light board 102 may be flexible so that the light guide 104 and the light board 102 can conform to each other when the light guide 104 and the light board 102 are applied to each other. In one example process, light guide 104 and light board 102 may be pressed or pulled together to match each other after light guide 104 is applied to light board 102. The light guide 104 and light board 102 can be applied to each other by applying hydrostatic pressure to the surface of the light guide 104 or light board 102 or by drawing a vacuum. In other examples, other processes may be used.

After the light guide 104 and the light board 102 are applied to each other with the OCA placed between them, the light guide 104 will be fixed to the light board 102. The strength of the bond between light guide 104 and light board 102 may be compromised due to various factors. However, such bonding is sufficient to withstand normal use of the backlight unit during normal shipping and processing that may be performed on the backlight unit when it is incorporated into a display device. It must be. The integrity of the bond between light guide 104 and light board 102 may be compromised due to, for example, normal stresses, vibrations, and shocks that occur. In addition, temperature changes and thermal expansion can also stress the bond and compromise its integrity. Furthermore, the strength of the bond may be insufficient as the surface area of the bond may be very small. In some designs, the light source may be very small. In one example, the light board 102 may include LED chips with a surface area of approximately 1.4 mm x 1.4 mm, and the distance between the LED chips may be 38 mm. In this example, when the OCA is applied to the LED chip, the OCA may have an applied area of a disk of about 3 mm in diameter encapsulating the LED, as shown in FIG. With this application area, the amount of surface area per LED chip is approximately 7 mm ² . Even in examples with a high number of LEDs per light board, the amount of bonding surface can be about 0.5% of the total area of the light guide. This amount of surface may be insufficient to securely couple the light guide 104 to the light board 102.

In some embodiments of the present disclosure, an auxiliary connector may be placed between the light sources 106 to add an auxiliary coupling between the light guide 104 and the light board 102. An example of such a backlight unit 400 is shown in FIG. In this example, auxiliary connector 410 may be placed between light sources 106. In this example, auxiliary connector 410 may provide additional coupling strength between light guide 104 and light board 102. Any number of auxiliary connectors may be placed between light sources 106. In the illustrated example, one auxiliary connector 410 is disposed between the light sources 106. In other examples, multiple auxiliary connectors can be added between the light sources. In the illustrated example, an auxiliary connector 410 is added to the backlight where the top surface of each light source 106 is coupled to the light guide 104 with a layer 404 of optically clear adhesive (OCA). Auxiliary connectors 410 can also be added to backlight units with OCA-encapsulated light sources (see FIG. 3).

Any suitable coupling element may be used for the auxiliary connector 410. Auxiliary connector 410 may be, for example, a quantity of optically clear adhesive (OCA). The OCA can be a UV, catalytic, or thermoset OCA. In other examples, the auxiliary connector 410 may be an adhesive (PSA) commonly known as mounting tape. Such mounting tape may be double-sided tape such that the mounting tape couples to the light board 102 on one side and the light guide 104 on the opposite side. The mounting tape is selected to have an appropriate thickness to support the light board 102 at a distance from the light board 102 to maintain a constant clearance as determined by the height of the light source 106. be able to.

The auxiliary connector 410 is designed so that the auxiliary connector 410 does not affect the uniform light distribution caused by the light guide and other optical films (not shown in FIG. 4) that may be placed over the light guide 104. is at least partially transparent. Since the auxiliary connector 410 is in optical contact with the light guide 104, it can be expected that some additional light will be extracted at the connector location by the auxiliary connector 410. Therefore, if auxiliary connector 410 is included in backlight unit 400 without any additional measures being taken, a viewer viewing that backlight unit 400 will have no idea where the connector is located (i.e., if auxiliary connector 410 is A bright spot will be visible at the position where the unit 400 is placed. Several measures can be taken to prevent this non-uniformity, known in the art as mura. A first strategy may be to place the auxiliary connector 410 in a location where the light extraction that occurs at the auxiliary connector 410 is less noticeable. Such a location may be a location under the area of light guide 104 that has the highest density of light extractors 120. Other suitable locations may be at the edge of the dimming area of the light guide 104. Still other suitable locations may be equally spaced locations between light sources 106 in an array of light sources 106 that may be included in light board 102. In a hexagonal arrangement, the auxiliary connector can be placed midway between the three light sources 106. In a rectangular array, the auxiliary connectors can be placed at the corners of the dimming area equidistant from the four light sources.

Another measure that can be taken to make the auxiliary connector 410 undetectable to the viewer is to change at least one optical property of the auxiliary connector relative to the adjacent area of the light board or backlight unit at the connector location. By placing the auxiliary connector at an advantageous connector location and changing the optical properties of the light board at the connector location or the optical properties of the auxiliary connector, the backlight unit can be The presence of the auxiliary connector 410 can be made undetectable to the viewing viewer. For purposes of this disclosure, undetectable to a viewer means that the viewer cannot detect the localization of non-uniformities in the backlight unit without the use of a light detection device such as a camera, photodetector or other light sensor. This means that the area cannot be seen.

Various optical properties can be changed at the connector location to make the auxiliary connector 410 undetectable to the viewer. In some examples, the reflectance of the light board 102 at the connector location can be adjusted to reflect less light. For example, the reflectance of the back reflector 110 can be adjusted at the connector location. The reflectivity of the light board 102 can be varied, for example, by printing an appropriate color (eg, gray) ink on the light board 102 at the connector location.

In other examples, the optical properties of the auxiliary connector 410 can be varied to adjust the transparency of the auxiliary connector 410. For example, the top surface of the mounting tape can be printed with a suitable color (eg, gray) ink. In another example, a suitable colored ink can be printed on the bottom of the mounting tape. In yet another example, a suitable colored pigment can be added to a bonding material such as an optically clear adhesive (OCA). Any of the above-mentioned or other inserts or colored pigments may be added to the auxiliary connector 410 to adjust the transparency of the auxiliary connector 410. As can be seen from the above, experiments can be performed to determine the preferred optical properties to be changed or adjusted in order to make the auxiliary connector undetectable to the viewer of the backlight unit.

In one experiment, a 1.1 mm thick light guide was coupled to a light board. The test light board included 1.4 square mm LED light sources spaced approximately 38 mm apart in a first direction and approximately 39 mm apart in a second direction. Auxiliary test connectors were placed equidistantly between the light sources. The test auxiliary connector was constructed using a layer of optically clear adhesive (OCA) on both sides of a 6 mm diameter blank paper disk. The reflectance of the blank discs was adjusted by printing various shades of gray on the upward facing side of the disc using a laser printer. A test backlight unit was assembled by placing the test auxiliary connector therebetween and applying the light guide to the light board. A typical back reflector used in a backlight assembly has a reflectance of about 97%. Experimental results revealed that the test auxiliary connector could be undetectably adjusted when a 1% density gray was printed on a blank disc and the reflectance was reduced to approximately 80%. Reflectance for purposes of this disclosure describes an optical property of a material or surface that describes the ability of a material or surface to reflect light directed at it. Reflectance can be described using a percentage that measures the amount of light reflected relative to the light directed at a material or surface. Therefore, a surface that is approximately 97% reflective can reflect approximately 97% of the light directed at that surface. The reflectance of the diffusely reflective surfaces discussed in this disclosure may be measured using any suitable technique known in the art. In the experiments described herein, the reflectance of a diffusely reflective surface was measured using a diffuse reflectance measurement device equipped with a spectrometer and an integrating sphere.

Based on the experimental results, it was determined that the reflectivity of the back reflector on the light board at the connector location could be adjusted to make the auxiliary connector undetectable to the viewer. In some examples, the back reflector (ie, the area of the light board adjacent the connector location) may have a reflectance in the range of about 90% to about 98%. To make the auxiliary connector undetectable, the optical properties of the light board (or back reflector) at the connector location can be adjusted to have a reflectance of about 50% to about 90%. In another example, the light board or back reflector may have a reflectivity of about 90% to about 98% in the area adjacent the connector location, and the light board or back reflector may have a reflectivity of about 50% to about 85%. can have a reflectance of In yet another example, the light board or back reflector may have a reflectivity of about 90% to about 98% in the area adjacent the connector location, and the light board or back reflector may have a reflectivity of about 50% to about 80%. % reflectance. Reflectance may be adjusted using any suitable technique, such as printing low density gray ink on a light board or on a back reflector. The low density gray ink (or other coating) can be deposited or printed using any suitable printing method (eg, inkjet printing, screen printing, microprinting, etc.). The term low density in the context of the low density gray described above can be characterized, for example, by printing or imaging software that can be used to print the gray on a substrate. Such software can, for example, use percentages to characterize gray density. In the example described above, the low density gray was a 1% density gray. In other examples, other low density grays may be used, such as low density grays with grays ranging from 1% to 5% density, depending on the particular configuration of the backlight unit. In still other examples, other densities can be used.

Referring now to FIG. 5, another example backlight unit 500 is shown. In this example, light guide 502 may include a first light guide tile 504 and a second light guide tile 506. Backlight unit 500 may include two or more light guide tiles that can be coupled to light board 102. This type of configuration is used to improve the ability of the light guide tiles to be adjusted relative to the light board 102 to ensure proper alignment is maintained to reduce the tendency for unevenness at the light source 106. be able to. One of the challenges that can arise in a tiled light guide situation such as the one shown in FIG. The tendency of light extraction between edges 510. First edge 508 and second edge 510 may define a tile gap 512 from which light may leak. Tile gaps 512 may appear as bright spots or bright lines when viewed by a user.

Even in instances where the first light guide tile 504 and the second light guide tile 506 are adjacent to each other such that the tile gap 512 can be negligibly small, the surfaces of the first edge 508 and the second edge 510 and edge quality, light can be extracted from each tile. For example, scratches, dents, and other imperfections in the edge surface may make the seam between the first edge 508 and the second edge 510 perceptible to the viewer.

One or more measures may be taken to reduce the tendency for light extraction in tile gaps 512 and to render tile gaps 512 undetectable to a viewer of backlight unit 500. A first example is shown in FIG. As can be seen, the light extractor 120 that is typically printed, etched, or otherwise formed on the light guide 502 may be removed or etched at the seam area 514. , printed or otherwise formed. Seam region 514 may extend away from first edge 508 and away from second edge 510 along first light guide tile 504 and second light guide tile 506, respectively. The width of the seam region 514 can be determined experimentally and may depend on the structure and size of the light guide tile. Experimental results show that the seam area can have a width of about 3 mm on the top surface of each light guide tile. In other examples, seam region 514 may have a width of about 0.5 mm to about 5 mm, measured along the top surface of each light guide tile. In other examples, the seam region may have other widths.

Another measure that can be taken to make tile gaps 512 (or tile seams) undetectable to the viewer is to add auxiliary connectors to tile gaps 512. The exemplary backlight unit 600 shows a configuration in which an auxiliary connector 610 is disposed between the light board 102 and the light guide 502. In the illustrated configuration, auxiliary connector 610 is positioned at connector location 612 aligned with tile gap 512. In examples where the first light guide tile 504 is adjacent to the second light guide tile 506, the connector location 612 can be aligned with the first edge 508 and the second edge 510.

Auxiliary connector 610 may be similar to auxiliary connector 410 described above. Auxiliary connector 610 can be made from OCA or mounting tape, for example. However, the auxiliary connector 610 may extend along the entire gap or seam between adjacent light guide tiles, such as between the first light guide tile 504 and the second light guide tile 506. As can be seen, the auxiliary connector 610 can be positioned between the light sources 106 and can be aligned with the first edge and/or the second edge 510. In this position, the auxiliary connector 610 can not only couple the first light guide tile 504 and the second light guide tile 506 to the light board 102, but also connect the tile gap 512 (or tile seam) and the auxiliary connector 610 to the backlight unit. 600 viewers can be made undetectable.

The optical properties of the auxiliary connector 610 or the optical properties of the light board 102 at the connector location 612 are made different from the optical properties of the light guide adjacent to the connector location 612 to connect the auxiliary connector and the tile gap or seam to the backlight unit 600. can be made undetectable to viewers. In some examples, the transparency or reflectance of the auxiliary connector 610 can be adjusted to make the auxiliary connector and tile gaps or seams undetectable to a viewer of the backlight unit 600. In other examples, the reflectance of the back reflector 110 can be adjusted to make auxiliary connectors and tile gaps or seams undetectable to a viewer of the backlight unit 600. For example, a colored ink or other coating can be printed on the back reflector 110 of the auxiliary connector 610 or connector location 612 to make the auxiliary connector and tile gap or seam undetectable to a viewer of the backlight unit 600.

Experimental results demonstrate the successful implementation of the structure of the backlight unit 600 shown in FIG. In one experiment, a 5 mm wide piece of polyester (PET) film was used as an auxiliary connector. An auxiliary connector was placed between the light board and the edges of the first and second light guide tiles. A yellow ink layer was printed on the PET film using a laser printer before adding OCA to both sides of the PET film. During the test, the density of the yellow ink was varied. In one test, the density of yellow ink printed on PET film corresponded to 10% opacity, as set in the image generation software. According to measurements, adding yellow ink of this density to PET film reduces the transmittance of the film for blue wavelength (450 nm) to about 75%, while for green wavelength (550 nm) and red wavelength (650 nm) , the PET film was almost transparent (measured at 92% due to reflection on both sides).

Based on the experiments described above, it has been determined that tile gaps and/or tile seams as well as auxiliary connectors can be made undetectable to the viewer of the backlight unit by adjusting the transmittance of blue wavelengths. In examples where the transmission of the auxiliary connector (eg, mounting tape) is adjusted, the transmission of the auxiliary connector needs to be reduced from approximately 50% to 90% at blue wavelengths. In instances where the back reflector is adjusted and the auxiliary connector remains substantially transparent or transparent, the reflectance of the back reflector at the connector location can be reduced from 25% to 80% at blue wavelengths. Various embodiments can be used to change the optical properties of the auxiliary connector or back reflector. For example, the top surface of the auxiliary connector (eg, the mounting tape) can be printed with low density yellow ink. In another example, the underside of the auxiliary connector (eg, mounting tape) can be printed with low density yellow ink. In another example, a low density ink can be printed on the surface of the back reflector at the connector location below the transparent auxiliary connector (eg, mounting tape). In yet another example, a low density yellow pigment can be added to the auxiliary connector material to impart a light color to the auxiliary connector.

In the experiments described above, a light board with blue light emitting LEDs was used in varying the transmittance previously recommended for the auxiliary connector and/or the back reflector. This applies to state-of-the-art backlight units in modern displays. The backlight unit comprises various optical films and other layers disposed over the light guide and/or light guide tiles. A more complete backlight unit is shown in FIG. In this example, the previously described backlight unit 600 is shown with a bulk diffuser 702 and various optical layers and films 704 positioned adjacent to the light guide 502. Examples of optical layers and films 704 include brightness enhancement films (BEF), dual brightness enhancement films (DBEF), reflective polarizers, diffusion films, and quantum dot (QD) color temperature conversion layers. A quantum dot (QD) color temperature conversion layer can be used to add red and green light to the backlight output. It should be noted that the optical layer and film 704 also serve to eliminate any remaining local brightness variations that may be present in the backlight unit 600. In addition, since the LEDs on the light board 102 include LEDs that emit blue light, the excess blue color must be attenuated by the auxiliary connector 610 at the edges of the first light guide tile 504 and the second light guide tile 506. There is light.

When using other light boards with light sources or LEDs that emit light of other colors or emit white light, adjust the optical properties of the auxiliary connector and/or the optical properties of the back reflector to The light of the desired color can be attenuated as necessary to render the auxiliary connectors and/or tile gaps or tile seams undetectable to a backlight viewer. For example, in an example where the light board includes a light source that emits white light and a quantum dot (QD) color temperature conversion layer is not present, the The auxiliary connector may have a mid-gray printed at the connector location to attenuate all colors by approximately the same amount as described above with respect to auxiliary connector 410 of FIG.

Another example backlight 800 is shown in FIG. In this example, backlight unit 800 may include a first light guide tile 802, a second light guide tile 804, and a light board 806. Backlight unit 800 is similar to the backlight units previously described. The backlight unit 800 connects the light guide tiles 802, 804 to an auxiliary connector located between the light sources 106 on one light guide tile and between the light sources 106 at the edge of the light guide tile. 8 shows an embodiment that can be coupled to a light board 806 using both auxiliary connectors. As shown in the figure, the backlight unit 800 can include a first auxiliary connector 810 and a second auxiliary connector 820. A first auxiliary connector 810 can be placed between the light sources 106 to add additional mechanical bonding strength to secure the second light guide tile 804 to the light board 806. First auxiliary connector 810 may be similar to auxiliary connector 410 previously described. The transparency or reflectivity of the back reflector 110 at the first auxiliary connector 810 or the first connector location 812 may be adjusted to make the first auxiliary connector 810 undetectable to a viewer of the backlight unit 800. can.

A second auxiliary connector 820 may be positioned at a second connector location 822 along an edge 814 of the first light guide tile 802 and along an edge 816 of the second light guide tile 804. Second auxiliary connector 820 may be similar to auxiliary connector 610 previously described. Adjusting the transparency or reflectance of the back reflector 110 at the second auxiliary connector 820 or the second connector location 822 to back up the tile gap or tile seam between the second auxiliary connector 820 and the edges 814, 816. The light unit 800 can be made undetectable to the viewer.

As appreciated from the above, the structure of backlight unit 800 can be reproduced in a backlight unit constructed to be used in a large display unit. Therefore, an auxiliary connector, such as the first auxiliary connector 810, may be provided between each of the light sources on a light board with an array of light sources as described above. In addition, auxiliary connectors, such as second auxiliary connector 820, can be used at the seams between each of the light guide tiles that may be used to construct a large backlight unit. The second auxiliary connector 820 can extend in any direction along the edge of the light guide tile.

Referring now to FIG. 9, a method 900 of assembling a backlight unit is shown. Method 900 can be used, for example, to assemble one of the backlight units described above. For brevity, the method 900 will be described using the backlight unit 800 shown in FIG. However, it should be recognized that the method (or variations thereof) can be used to similarly assemble backlight units 400, 600.

At step 902, a light board is provided. This light board may be, for example, light board 806. The light board can include a number of light sources 106 that can be arranged along the light board or in other patterns. The light source 106 may protrude away from the mounting board of the light board 806 such that the light source 106 can extend above the mounting board when the light board is oriented horizontally.

At step 904, an auxiliary connector may be placed between the light sources. In the exemplary backlight unit 800, a first auxiliary connector 810 may be disposed between the light sources 106. The first auxiliary connector 810 may be positioned approximately equidistant from each of the light sources 106. A first auxiliary connector 810 can be placed on the light board 806 using adhesive or other connection means. The first auxiliary connector 810 may have different optical properties than the optical properties of the light board in the area adjacent the first connector location 812. In this way, the first auxiliary connector 810 can be made undetectable to a viewer of the backlight unit when this backlight unit is used in a display device.

At step 906, the auxiliary connector may be placed at the edge location. In the example backlight unit 800, a second auxiliary connector 820 is aligned with the first edge 814 and/or the second edge 816 of the first light guide tile 802 and the second light guide tile 804, respectively. can be placed. Second auxiliary connector 820 may be, for example, a length of mounting tape. The second auxiliary connector 820 may have different optical properties than the optical properties of the light board in the area adjacent the second connector location 822. In this way, the second auxiliary connector 820 and the edges 814, 816 can be made undetectable to a viewer of the backlight unit when the backlight unit is used in a display device.

At step 908, a primary connector may be applied to the light source. In the example backlight unit 800, a layer of adhesive, such as an optically clear adhesive (OCA), is applied to the surface of the light source 106 facing the first light guide tile 802 and/or the second light guide tile 804. Or you can apply mounting tape.

At step 910, a light guide may be applied to the light board. The first light guide tile 802 and the second light guide tile 804 are located at each location where the light guide tile 802, 804 contacts one of the light source 106, the first auxiliary connector 810, and the second auxiliary connector 820. A force can be applied to the light board 806. The applied force can be applied, for example, by pulling a vacuum on the light guide tiles 802, 804 and the light board 806, or by applying hydrostatic pressure to the light guide tiles 802, 804 and/or the light board 806. can. In other examples, the application force can be applied using other methods. As can be appreciated from the foregoing, when the first light guide tile 802 and/or the second light guide tile 804 are applied to the light board, the light guide tile will be attached to the light guide tiles 802, 804 and the light board. 806 to ensure proper alignment is maintained with the light board.

The methods and systems described herein may be embodied, at least in part, in the form of computer-implemented processes and apparatus for implementing the processes. The disclosed method may also be embodied, at least in part, in the form of a tangible, non-transitory, machine-readable storage medium encoded with computer program code. Examples of such media include RAM, ROM, CD-ROM, DVD-ROM, BD-ROM, hard disk drive, flash memory, or any other non-transitory machine-readable storage medium, or any combination of these media. where the computer program code becomes a device for performing the method when the computer program code is loaded onto a computer and executed. The method may also be at least partially embodied in the form of a computer on which the computer program code is loaded and/or executed, thus making the computer an apparatus for performing the method. . When executed on a general purpose processor, the computer program code segments configure the processor to create specific logic circuits. The method may alternatively be at least partially embodied in a digital signal processor formed from an application specific integrated circuit for implementing the method.

Although the subject matter has been described with respect to exemplary embodiments, the subject matter is not limited thereto. Rather, the appended claims are to be broadly construed to include other modifications and embodiments that would occur to those skilled in the art.

Preferred embodiments of the present invention will be described below.

Embodiment 1
In the backlight unit,
a light board having a first light source and a second light source;
a light guide disposed adjacent to the light board for distributing light emitted from the first light source and the second light source; and a light guide between the first light source and the second light source. a connector positioned at a connector location to couple the light guide to the light board;
Equipped with
The optical properties of the light board or of the connector at the connector location are different from the optical properties at adjacent locations in order to make the connector undetectable to a viewer of the backlight unit. unit.

Embodiment 2
The backlight unit of embodiment 1, wherein the optical property includes transparency of the connector.

Embodiment 3
The backlight unit of embodiment 1, wherein the connector is colored gray to reduce transparency of the connector.

Embodiment 4
The backlight unit according to embodiment 1, wherein the connector is colored yellow.

Embodiment 5
The backlight unit of embodiment 1, wherein the optical property includes a reflectance of the light board at the connector location.

Embodiment 6
The backlight unit according to embodiment 1, wherein a reflectance of the light board at the connector location is lower than a reflectance of the light board adjacent to the connector location.

Embodiment 7
The backlight unit of embodiment 1, wherein the light board comprises a gray coating at the connector location.

Embodiment 8
The backlight unit of embodiment 1, wherein the light board comprises a yellow coating at the connector location.

Embodiment 9
the light guide includes a first light guide tile including a first edge and a second light guide tile including a second edge, and the connector is aligned with the first edge and the second edge. The backlight unit according to Embodiment 1.

Embodiment 10
The backlight unit of embodiment 1, wherein the light board includes an array of light sources, and the connector is disposed between adjacent light sources in the array of light sources.

Embodiment 11
The backlight unit of embodiment 1, wherein the light guide is coupled to the first light source and the second light source.

Embodiment 12
In backlight units for use in displays,
light board with multiple light sources,
a first light guide tile and a second light guide tile arranged adjacent to each other, a first edge of the first light guide tile meeting a second edge of the second light guide tile; a first light guide tile and a second light guide tile arranged adjacently to define a tile seam between the first light guide tile and the second light guide tile; and the tile seam. and a connector disposed between the light board and the first light guide tile and the second light guide tile, the connector being arranged between the first light guide tile and the second light guide tile. a connector that couples to the light board;
Backlight unit with.

Embodiment 13
Adjacent portions of the light board such that the portion of the light board at the connector location of the connector makes the connector and the first and second edges undetectable to a viewer of the backlight unit. 13. The backlight unit of embodiment 12, wherein the backlight unit has a lower reflectance than the rest of the backlight unit.

Embodiment 14
14. The backlight unit of embodiment 13, wherein the reflectance of the portion of the light board at the connector location is reduced to have a blue light reflectance in the range of about 25% to about 80%.

Embodiment 15
the connector is colored to reduce light transmission at a connector location of the connector to render the connector and the first edge and the second edge undetectable to a viewer of the backlight unit; The backlight unit according to Embodiment 12.

Embodiment 16
16. The backlight unit of embodiment 15, wherein the transmittance of blue light having a wavelength of about 450 nm by the connector is reduced to be in the range of about 50% to about 90%.

Embodiment 17
A method of assembling a backlight unit, the method comprising:
placing a connector on a light board at a connector location between a first light source and a second light source; and coupling a light guide plate to the light board at the connector location;
How to have.

Embodiment 18
18. The method of embodiment 17, wherein the connector is colored to reduce light transmission at the connector location.

Embodiment 19
18. The method of embodiment 17, wherein a portion of the light board at the connector location has a low reflectivity relative to an adjacent portion of the light board.

Embodiment 20
18. The method of embodiment 17, further comprising aligning the connector with an edge of the light guide plate.

100, 300, 400, 500, 600, 800 Backlight unit 102, 200, 806 Light board 104, 502 Light guide 106 Light source 108, 202 Mounting board 110 Back reflector 118 Print reflector 120 Light extractor 124 Light guide plate 204 LED
302 Optically Clear Adhesive (OCA)
404 layer of optically clear adhesive (OCA) 410, 610 auxiliary connector 504, 802 first light guide tile 506, 804 second light guide tile 508 first edge 510 second edge 512 tile gap 514 seam area 612 connector location 702 bulk diffuser 704 optical layer and membrane 810 first auxiliary connector 812 first connector location 814, 816 edge 820 second auxiliary connector 822 second connector location

Claims (14)

In the backlight unit,
a light board having a first light source and a second light source;
a light guide disposed adjacent to the light board for distributing light emitted from the first light source and the second light source; and a light guide between the first light source and the second light source. a connector positioned at a connector location to couple the light guide to the light board;
Equipped with
The optical properties of the light board or of the connector at the connector location are different from the optical properties at adjacent locations in order to make the connector undetectable to a viewer of the backlight unit. unit. The backlight unit of claim 1, wherein the optical property includes transparency of the connector. The backlight unit according to claim 1, wherein the connector is colored gray or yellow to reduce transparency of the connector. The backlight unit of claim 1, wherein the optical properties include reflectance of the light board at the connector location. The backlight unit according to claim 1, wherein a reflectance of the light board at the connector location is lower than a reflectance of the light board adjacent to the connector location. The backlight unit according to claim 1, wherein the light board comprises a gray coating or a yellow coating at the connector location. the light guide includes a first light guide tile including a first edge and a second light guide tile including a second edge, and the connector is aligned with the first edge and the second edge. The backlight unit according to claim 1, wherein: The backlight unit of claim 1, wherein the light board includes an array of light sources, and the connector is disposed between adjacent light sources in the array of light sources. The backlight unit of claim 1, wherein the light guide is coupled to the first light source and the second light source. In backlight units for use in displays,
light board with multiple light sources,
a first light guide tile and a second light guide tile arranged adjacent to each other, a first edge of the first light guide tile meeting a second edge of the second light guide tile; a first light guide tile and a second light guide tile arranged adjacently to define a tile seam between the first light guide tile and the second light guide tile; and the tile seam. and a connector disposed between the light board and the first light guide tile and the second light guide tile, the connector being arranged between the first light guide tile and the second light guide tile. a connector that couples to the light board;
Backlight unit with. Adjacent portions of the light board such that the portion of the light board at the connector location of the connector makes the connector and the first and second edges undetectable to a viewer of the backlight unit. 11. The backlight unit according to claim 10, having a lower reflectance than the rest of the backlight unit. 12. The backlight unit of claim 11, wherein the reflectance of the portion of the light board at the connector location is reduced to have a blue light reflectance in the range of about 25% to about 80%. the connector is colored to reduce light transmission at a connector location of the connector to render the connector and the first edge and the second edge undetectable to a viewer of the backlight unit; The backlight unit according to claim 10. 14. The backlight unit of claim 13, wherein the transmittance of blue light having a wavelength of about 450 nm by the connector is reduced to be in the range of about 50% to about 90%.

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