KR20230146660A - Tiled and partially stacked liquid crystal display backlights - 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 disperse light emitted from the first light source and the second light source. An auxiliary connector is located at the connector position between the first light source and the second light source to couple the light guide to the light board, wherein the optical characteristics of the light board or auxiliary connector at the connector position are determined by the auxiliary connector to the viewer of the backlight unit. differ from the optical properties of adjacent locations such that they cannot be detected.

Description

Tiled and partially stacked liquid crystal display backlights

This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application No. 63/152,463, filed February 23, 2021, the contents of which are incorporated herein by reference in their entirety.

This disclosure relates to tiled and partially stacked liquid crystal display (LCD) backlights. More specifically, the present disclosure relates to a backlight that may include tiled light boards and/or tiled light guides stacked together to create robust backlight assemblies with improved mechanical reliability and uniform brightness.

In modern and emerging display technologies, such as those in liquid crystal displays (LCDs), display trends include increasing resolution, higher peak brightness and dynamic range (HDR), higher contrast, thinner set designs, and thinner set designs. Narrow bezels are included. To address these trends, displays may include a direct-lit backlight, which may include an array of two-dimensional light sources located directly behind the LCD panel. The array of two-dimensional light sources may include a light emitting diode (LED) array. Various elements can distribute light from an array of light sources evenly throughout the display panel to meet the brightness, contrast and other requirements of the display.

In some display designs, an array of light sources uses a light guide(s) that can include various elements such as light guide plates, films, patterns, or other optical elements and layers to meet the above requirements of the display. This can be distributed across the display. However, existing designs have several drawbacks. For example, one drawback is that it can be difficult to align the light guide with the array of light sources. Another example drawback is that existing backlight designs may include materials that do not allow for thinner, narrower bezels. Another drawback is that existing backlight designs may suffer from mechanical reliability issues. Another example disadvantage is that existing designs may require complex and/or expensive manufacturing processes. Accordingly, light sources and light guides can be more easily aligned, have designs that allow for thinner display thicknesses and narrower bezels, have improved mechanical reliability, and can be manufactured using less complex and less expensive processes. There is a need for improved backlights.

The present disclosure provides a backlight that can be used in a display that includes auxiliary connectors intermittently positioned between a light guide plate and a light board at predetermined locations between light sources on the light board. The optical properties of the auxiliary connectors can be adjusted so that the auxiliary connector cannot be detected by a viewer of the backlight unit. Additional connectors can not only improve the mechanical reliability of the backlight unit, but also improve the accuracy and repeatability of correctly aligning the light guide to the light board using tiled light plates.

In one aspect, the present disclosure discloses a backlight unit. According to some embodiments, a backlight unit for use in a display device includes a light board including a first light source and a second light source. The backlight unit also includes a light guide positioned adjacent the light board to disperse light emitted from the first light source and the second light source. A connector is located at a connector location between the first light source and the second light source to couple the light guide to the light board, and at the connector location such that the connector is undetectable to a viewer of the backlight unit. The optical properties of the optical board or of the connector are different from the optical properties at adjacent locations.

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

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

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

In another aspect, the optical characteristic may include reflectivity of the light board at the connector location.

In another aspect, the reflectivity of the optical board at the connector location may be less than the reflectivity of the optical board adjacent to the connector location.

In another aspect, the optical board may include a gray coating at the connector location to reduce the reflectivity of the optical board at the connector location.

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

In another aspect, the light guide may include a first light guide tile including a first edge and a second light guide tile including a second edge, and the connector is connected to the first edge and the second edge. Sorted.

In another aspect, the optical board may include an array of light sources, and the connector is positioned between adjacent light sources in the array of light sources.

In another aspect, the light guide may 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 including a plurality of light sources, and a second light guide tile for defining a tile seam between a first light guide tile and a second light guide tile. It may include the first light guide tile and the second light guide tile positioned adjacent to each other and having a first edge of the first light guide tile positioned adjacent to the second edge of . The backlight unit may also include a connector positioned between the light board and the first light guide tile and the second light guide tile at the tile seam, where the connector includes the first light guide tile and the second light guide tile. A light guide tile is coupled to the light board.

In another aspect, a method of assembling a backlight unit is provided. According to some embodiments, the method includes providing an optical board including a first light source and a second light source, and positioning a connector on the optical board at a connector location between the first light source and the second light source. Includes. The method may also include coupling a light guide plate to the light board at the 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 to scale. On the contrary, the dimensions of various features have been arbitrarily expanded or reduced for clarity. Like reference numbers indicate like features throughout the specification and drawings.
1 is a cross-sectional view showing an exemplary backlight unit.
2 is a top view of an example optical board with an array of light sources according to some embodiments.
Figure 3 is a cross-sectional view showing an exemplary backlight unit with a connection between a light board and a light guide plate.
4 is a cross-sectional view illustrating an example backlight unit including an auxiliary connector between a light board and a light guide plate according to some embodiments.
5 is a cross-sectional view illustrating an example backlight unit including a tiled light guide plate according to some embodiments.
FIG. 6 is an exemplary cross-sectional view of an exemplary backlight unit including an auxiliary connection between the light board of FIG. 4 and a tiled light guide plate.
7 is a cross-sectional view illustrating an example backlight unit including auxiliary connections between a light board and another example tiled light guide plate according to some embodiments.
FIG. 8 is an example cross-sectional view of the example backlight unit of FIG. 4 including multiple optical layers in accordance with some embodiments.
9 is a flow chart illustrating an example method of producing a backlight unit including auxiliary connections between a light board and a light guide plate in accordance with some embodiments.

This description of exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are considered part of the entire written description. Descriptions should include relative terms such as "lower", "top", "horizontal", "vertical", "above", "bottom", "up", "down", "top" and "bottom". Derivatives of (e.g., “horizontally,” “downward,” “upward,” etc.) should be construed as referring to the direction shown in the drawings then described or discussed. These relative terms are for convenience of explanation and do not require that the device be configured or operated in a particular orientation. Terms related to attachment, bonding, etc., such as "connected" and "interconnected," refer to relationships in which structures are fixed or attached to each other directly or indirectly through intermediate structures, as well as movable or fixed structures, unless explicitly stated otherwise. It means attachment or relationship.

For purposes of the description below, it should be understood that the embodiments described below may assume alternative variations and embodiments. It is also to be understood that the specific articles, compositions, and/or processes described herein are illustrative and should not be regarded as limiting.

In this disclosure, the singular forms “a,” “an,” and “the” include plural references, and references to a specific numerical value include at least that specific value, unless the context clearly dictates otherwise. When values are expressed as approximations using the antecedent “about,” it will be understood that the specific value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably means ±10% of the recited value. For example, the phrase “about 8” preferably means a value between 7.2 and 8.8. When present, all scopes are inclusive and combinable. For example, when referring to a range of “1 to 5,” the ranges referred to are “1 to 4,” “1 to 3,” “1 to 2,” “1 to 2 and 4 to 5,” and “1 to 2.” It should be interpreted as including the range of “to 3 and 5”, “2 to 5”, etc. Additionally, where a list of alternatives is provided in the affirmative, such list may be interpreted to mean that any of the alternatives may be excluded, for example, by negative limitations of the claims. For example, when a range of “1 to 5” is mentioned, the stated range may be interpreted to include situations where any of 1, 2, 3, 4, or 5 is negatively excluded; Accordingly, reference to “1 through 5” may be interpreted as “1 and 3 through 5 but not 2,” or simply as “2 is not included.” Any component, element, attribute or step positively recited herein is expressly excluded from the scope of the claims, regardless of whether such component, element, property or step is alternatively listed or they are separately recited. It is intended that it can be done.

The present disclosure provides a backlight unit including one or more auxiliary connections between a light board and a light guide plate. The auxiliary connections can provide increased mechanical robustness and allow for improved dimensional alignment between the light board and the light guide plate. Improved mechanical robustness can reduce the likelihood of mechanical failure of the backlight unit compared to existing designs and improve the efficiency and dimensional accuracy of the backlight unit. This can ultimately reduce costs and improve the ability of the backlight unit to provide uniform luminance in a display including the backlight unit.

In some embodiments, the light guide plate of the backlight unit may include a panel made of glass. Unless explicitly indicated otherwise, the terms “glass article” or “glass” as used herein are understood to include any object made in whole or in part of glass. Glass articles include monolithic substrates or stacks of glass and glass, glass and non-glass materials, glass and crystalline materials, glass and glass-ceramics (including amorphous and crystalline phases).

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

Exemplary glasses may include, but are not limited to, aluminosilicates, alkali-aluminosilicates, borosilicates, alkali-borosilicates, aluminoborosilicates, alkali-aluminoborosilicates, and other suitable glasses. Non-limiting examples of available glasses suitable for use as light guides include eyeglasses, such as IRIS™ and GORILLA® glasses from Corning Incorporated. Glass products can optionally be strengthened. In some embodiments, a glass article can be mechanically strengthened by exploiting a mismatch in the coefficient of thermal expansion between portions of the article to create a compressive stress zone and a central zone representing tensile stress. In some embodiments, glass articles can be thermally strengthened by heating the glass to a temperature above its glass transition point and then quickly quenching it. In some other embodiments, the glass article may be chemically strengthened by ion exchange.

Referring to Figure 1, an example backlight unit 100 is shown. The backlight unit 100 may be used, for example, in a liquid crystal display (LCD). Some LCDs have brightness, contrast and other requirements that can be met using direct-illuminated backlight devices. Direct-illuminated backlight devices can often include an array of two-dimensional light sources. An array of two-dimensional light sources may be arranged as a plurality of light emitting diodes (LEDs) placed on a printed circuit board (PCB). These PCBs or optical boards direct light towards the viewer of the display and are located behind the display panel. Light emitted from the light board can be uniformly distributed using a light guide. In this way the display can be illuminated according to various requirements for 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 . Light board 102 may include a number of light sources 106 located on a surface of light board 102 that faces a viewer when backlight unit 100 is used in a display. Light source 106 may be LEDs, for example. Light source 106 may be mounted on mounting board 108. Mounting board 108 may be, for example, a printed circuit board (PCB) capable of delivering power to light sources 106 . Light board 102 may also include a back reflector 110 located on the same surface of mounting board 108 as light sources 106. Light guide 104 may be positioned adjacent to light source 106. Light guide 104 may include various features and/or layers that can disperse light emitted from light source 106. The light guide 104 may disperse the light emitted from the light source 106 so that the light is distributed uniformly across the light guide 104 so that the positions of the light sources cannot be detected by the human eye when viewing the display. The light guide 104 may include, for example, a printed reflector 118 positioned opposite the light sources 106 on the surface of the light guide 104. Printed reflectors 118 can reflect light emitted from light sources 106 so that local bright spots do not appear over the respective locations of the light sources. Light guide 104 may also include various light extractors 120 that may be positioned on the surface of light guide 104. Light extractors 120 may be dots, dimples or other features that may be printed, etched or otherwise deposited or formed in the light guide. The light extractors 120 may be distributed along the light guide 104 to uniformly distribute light throughout the light guide.

As shown in FIG. 1, light emitted from light source 106 (indicated by arrow 122) travels in light guide 104 to distribute the light from light source 106 throughout light guide 104. It may be refracted, reflected or otherwise guided. Light guide 104 includes a light guide plate 124 that can be made of a material suitable for guiding light emitted from light sources. In some examples, light guide plate 124 may be made of a glass material. The dimensional and reliability requirements of modern displays make glass a desirable material for light guide plates. The thermal and mechanical properties of glass allow the backlight unit 100 to be designed and manufactured to be thinner and have increased dimensional stability compared to having the light guide plate 124 made of other materials, such as polymers or other suitable plastic materials. Additionally, using a glass light guide plate allows the LCD's bezel to have a smaller overall width than an LCD that integrates a backlight unit with light guide plates made of a material other than glass.

The backlight unit 100 shown in FIG. 1 may represent a portion of a backlight unit. As can be appreciated, the backlight unit 100 may be reproduced in various profiles such that the backlight unit may include multiple light sources 106 . An example of this is shown in Figure 2. In the above example, optical board 200 may include a mounting board 202, such as a PCB, that can transfer power to LEDs 204. As shown, light board 200 may include multiple LEDs 204, which may be arranged in an array of multiple rows and columns of LEDs. Light board 200 may be of any suitable size needed to illuminate the LCD. As shown, light board 200 may include 20 LEDs 204. In other examples, light board 200 may include more or less than 20 LEDs. In some displays, it is not uncommon for the light board 200 to include hundreds of LEDs. For example, the optical board 200 can be used in a display having a diagonal size of 80 inches or more. In such an example, light board 200 may include more than 900 LEDs. The backlight unit in each LED may include the structure shown in FIG. 1 with a light guide disposed on 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 appreciated, the reflector 118 needs to be positioned relative to the light sources 106 to ensure that management of the light in the light guide creates a uniform light distribution in the light guide 104. If there is excessive mismatch between the reflector 118 and the light source 106, the backlight unit 100 may have bright spots called Mura or other irregularities. To minimize the Mura effect, the alignment of light guide 104 with respect to light board 102 must be carefully controlled during fabrication of backlight unit 100. As the number of light sources 106 increases, it becomes more difficult to ensure proper alignment between the light guide 104 and the light board 102.

To make the assembly and alignment of the light guide 104 relative to the light board 102 more easily controlled and repeatable within appropriate tolerances, one possible solution is to use either the light guide 104 and the light board 102 or The idea is to separate both into tiles. In such example designs, instead of having a single light guide 104 that includes a single light guide plate 124 the size of the entire display screen, the light guide 104 may be separated into individual tiles located adjacent to each other. You can. The light guide tiles, when assembled together, can take on the full size of the entire display screen. Such designs may also include an optical board 102 created from multiple tiled optical boards assembled together. This tiled structure allows individual tiles to be adjusted in relation to each other to ensure proper alignment between the light guide tiles and/or light board tiles. In various examples, light guide 104 may be created from multiple light guide tiles assembled into an integrated light board. In another example, a single light guide plate can be assembled to a light board made of multiple light board tiles. In another example, the light guide and light board may be made of multiple light guide tiles and light board tiles, respectively. These tiled designs are further described in U.S. Application No. 63/017,078, filed April 29, 2020, the contents of which are incorporated herein in their entirety.

Another problem that may arise in the assembly of a direct-illuminated backlight unit is the mechanical robustness and reliability of the backlight unit. In some designs, the backlight unit is required to be very thin in order to be assembled into a thin or ultra-thin backlight unit for assembly into a thin or ultra-thin LCD device. Such thin or ultra-thin backlight units may have an overall thickness t (see Figure 1) between about 1 mm and about 5 mm. In the example of Figure 1 the thickness t is shown without additional optical diffusers, layers and films such as BEFs, DBEFs. The additional thickness of these optical diffusers, layers and/or films can add about 0.5 mm to about 3 mm of thickness to the overall thickness of the backlight unit. In these thin 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 the light guide plate 124 and/or mounting board 108 may have a thickness of less than about 0.5 mm.

Referring now to Figure 3, another example backlight unit 300 is shown. The backlight unit 300 is similar in many respects to the backlight unit 100 described above. As shown, 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. OCA 302 may be applied to light source 106 because light source 106 may extend above the surface of the light board. In such examples, light guide 104 is bonded to the light board at each location of light source 106. OCA can be applied to the opposing surface of the light source facing the light guide 104. Additionally, OCAs exist around each light source 106 such that the OCA's footprint can be larger than the footprint of the light source 106.

Light guide 104 and light board 102 may each be assembled using a variety of suitable methods and processes. In some examples, light guide 104 and light board 102 are laminated together using an optically clear adhesive. Light guide 104 and light board 102 may be manufactured to have substantially planar surfaces, but neither light guide 104 nor light board 102 is perfectly flat. The light guide 104 and light board 102 may be flexible so that the light guide 104 and light board 102 can be aligned with each other when the light guide 104 and light board 102 are applied to each other. In some example processes, light guide 104 and light board may be pressed or pulled together to match each other after light guide 104 is applied to light board 102. Light guide 104 and light board 102 may be applied to each other by drawing a vacuum or providing hydrostatic pressure over the surface of light guide 104 or light board 102. 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 in between, the light guide 104 will be fixed to the light board 102. The strength of the bond between the light guide 104 and the light board can be compromised due to a variety of factors. However, this bond needs to be sufficient to withstand normal use of the backlight unit and normal shipping and processing processes that may occur to the backlight unit when it is assembled into a display device. The integrity of the bond between the light guide 104 and the light board 102 may be compromised due to normal stresses, vibrations and impacts that occur, for example. Temperature changes and thermal expansion can also stress the bond and compromise its integrity. Additionally, because the bonding surface is very small, the bonding strength may be insufficient. In some designs the light sources can 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 OCA is applied to an LED chip, the OCA footprint may have the footprint of a disk about 3 mm in diameter encapsulating the LED, as shown in Figure 3. In this footprint, the amount of surface area per LED chip is approximately 7 mm ² . Even with a large number of LEDs per light board, the amount of adhesive surface can be approximately 0.5% of the total area of the light guide. This amount of surface area may be insufficient to securely couple the light guide 104 to the light board 102.

In some embodiments of the present disclosure, auxiliary connectors may be located between light sources 106 to add auxiliary couplings between light guide 104 and light board. An example of such a backlight unit 400 is shown in FIG. 4 . In this example, auxiliary connector 410 may be located between light sources 106. In this example, auxiliary connector 410 may provide additional coupling force between light guide 104 and light board 102. Any number of auxiliary connectors may be located between light sources 106. In the example shown, one auxiliary connector 410 is located between light sources 106. In other examples, more than one auxiliary connector may be added between light sources. In the example shown, auxiliary connectors 410 are added to the backlight where the top surface of each light source 106 is bonded to the light guide 104 by a layer 404 of optically clear adhesive (OCA). Auxiliary connectors 410 may also be added to backlight units containing light sources encapsulated in OCA (see Figure 3).

Any suitable mating element may be used in auxiliary connector 410. Auxiliary connector 410 may be, for example, a quantity of optically clear adhesive (OCA). OCA may be UV, catalytic or thermoset OCA. In other examples, auxiliary connector 410 may be a pressure-sensitive adhesive (PSA), commonly known as mounting tape. These mounting tapes may be double-sided such that the mounting tape is adhered to the light board 102 on one side and to the light guide 104 on the opposite side. The mounting tape may be selected to have a thickness suitable to support the light board 102 at a distance from the light board 102 to maintain consistent spacing as determined by the height of the light source 106.

To ensure that the auxiliary connectors 410 do not affect the uniform light distribution caused by the light guide and other optical films (not shown in Figure 4) that may be placed over the light guide 104, the auxiliary connectors 410 It is at least partially transparent. Because the auxiliary connectors 410 are in optical contact with the light guide plate 104, the auxiliary connectors 410 can be expected to allow some additional light to be extracted at the connector location. Therefore, if the auxiliary connectors 410 are included in the backlight unit 400 without any additional measures, the viewer viewing the backlight unit 400 will be able to determine the location of the connectors (i.e., where the auxiliary connector 410 is located in the backlight unit 400). You will see a bright spot at the location. Several steps can be taken to prevent this non-uniformity, known in the art as mura. A first measure may be to position the auxiliary connectors 410 in locations where the light extraction caused by the auxiliary connectors 410 is less noticeable. These locations may be at locations below areas of the light guide 104 that have the highest density of light extractors 120. Other suitable locations may be at the edges of the dimming zones of the light guide 104. Still other suitable locations may be equally spaced positions among the light sources 106 of an array of light sources 106 that may be included in the light board 102. In a hexagonal array, the auxiliary connectors may be located centrally between the three light sources 106. In a rectangular array, the auxiliary connectors may be located at the corners of the dimming area at equal distances from the four light sources.

Another measure that can be taken to make the auxiliary connectors 410 undetectable to the viewer is to change at least one optical characteristic of the auxiliary connector with respect to adjacent areas of the backlight unit or of the light board at the location of the connector. It includes By placing the auxiliary connector at an advantageous connector location and changing the optical properties of the auxiliary connector or of the optical board at the connector location, when the auxiliary connector 410 is assembled into the display device, the viewer looking at the backlight will be able to see the auxiliary connector 410. It can make its existence undetectable. For the purposes of this disclosure, undetectable to the viewer means that the viewer cannot see localized areas of non-uniformity in the backlight unit without the aid of an optical sensing device such as a camera, light detector, or other light sensor.

Various optical characteristics may be changed at the connector location so that the viewer cannot detect the auxiliary connector 410. In some examples, the reflectivity of light board 102 at the connector location can be adjusted so that less light is reflected. For example, the reflectivity of back reflector 110 can be adjusted at the connector location. The reflectivity of the light board 102 may be changed, for example, by printing a suitable color (e.g., gray color) ink on the light board 102 at the connector location(s).

In other examples, the optical properties of auxiliary connector 410 may be changed to adjust the transparency of auxiliary connector 410. For example, an appropriate color (eg, gray color) ink can be printed on the top surface of the mounting tape. In another example, a suitable color ink may be printed on the bottom surface of the mounting tape. In another example, suitable color pigments may be added to the bonding material, such as an optically clear adhesive (OCA). Any of the foregoing or other inserts or color pigments may be added to auxiliary connector 410 to adjust the transparency of auxiliary connector 410. As can be appreciated, experimentation can be used to determine the desired optical properties to be changed or adjusted so that a viewer of the backlight unit cannot detect the auxiliary connector.

In one experiment, a 1.1 mm thick light guide was coupled to the light board. The test light board contained 1.4mm square LED light sources positioned approximately 38mm apart in one direction and approximately 39mm apart in a second direction. Auxiliary connectors for testing were placed at equal intervals between the light sources. Auxiliary connectors for testing were constructed using a layer of optically clear adhesive (OCA) on both sides of 6 mm diameter white paper disks. The reflectivity of the paper disks was adjusted by printing various shades of gray on the upward surface of the disks using a laser printer. A backlight unit for testing was assembled by applying a light guide to the optical board with auxiliary connectors for testing in between. A typical back reflector used in a backlight assembly is approximately 97% reflective. Experimental results showed that when printing 1% density gray on a paper disk, the auxiliary test connectors were adjusted to be undetectable, reducing the reflectance to approximately 80%. Reflectance for the purposes of this disclosure describes an optical property of a material or surface that describes its ability to reflect light directed at or toward the material or surface. Reflectance can be described using a percentage that measures the amount of light that is reflected compared to the light directed at or towards a material or surface. Therefore, a surface that is approximately 97% reflective can reflect approximately 97% of the light directed towards or away from the surface. The reflectance of the diffusely reflective surfaces discussed in this disclosure can be measured using any suitable technique known in the art. In the experiments described herein, the reflectance of diffusely reflective surfaces was measured using a diffuse reflectance measurement device comprising a spectrometer and an integrating sphere.

In light of the experimental results, it was determined that the reflectivity of the back reflector on the optical board at the connector locations could be adjusted so that the viewer would not be able to detect the auxiliary connectors. In some examples, the back reflector (i.e., the area of the light board adjacent to the connector locations) may have a reflectivity ranging from about 90% to about 98%. To render the auxiliary connector undetectable, the optical properties of the light board (or back reflector) at the connector locations can be adjusted to have a reflectivity of about 50% to about 90%. In other examples, the light board or back reflector may have a reflectivity of about 90% to about 98% in areas adjacent to the connector locations, and the light board or back reflector may have a reflectivity of about 50% to about 85%. You can. In another example, the light board or back reflector may have a reflectivity of about 90% to about 98% in areas adjacent to the connector locations, and the light board or back reflector may have a reflectivity of about 50% to about 80%. You can. Reflectance can be adjusted using appropriate techniques, such as printing a low-density gray color ink on a light board or back reflector. Low-density gray color ink (or other coating) may be deposited or printed using any suitable printing method (e.g., inkjet printing, screen printing, microprinting, etc.). The term low density, in relation to the previously described low density gray color, can be characterized by, for example, printing or imaging software that can be used to print a gray color onto a substrate. For example, such software can characterize the density of gray color using percentages. In the example described above, the low density gray color was 1% density gray. In other examples and depending on the specific configuration of the backlight unit, other low density gray colors may be used, such as low density gray in the 1% to 5% density gray range. Other densities may be used in still other examples.

Referring now to Figure 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 may be coupled to light board 102. This type of configuration can be 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 likelihood of mura occurring in the light sources 106. One challenge that may arise in the context of a tiled light guide such as that shown in Figure 5 is the alignment of the first edge 508 of the first light guide tile 504 and the second edge of the second light guide tile 506 ( 510) is the possibility of light extraction between them. The first edge 508 and the second edge 510 may define a tile gap 512 through which light passes. The tile gap 512 may appear as a bright spot or bright line when viewed by the user.

Even in cases where the first light guide tile 504 and the second light guide tile 506 are adjacent to each other and the tile gap 512 can be ignored, the surfaces of the first edge 508 and the second edge 510 and edge quality can cause light to be extracted from each tile. For example, a seam between first edge 508 and second edge 510 may be noticeable to the viewer due to scratches, dents, and other defects in the edge surfaces.

One or more measures may be taken to reduce the likelihood of light extraction in the tile gap 512 and make the tile gap 512 undetectable to a viewer of the backlight unit 500. A first example is shown in Figure 5. As shown, light extractors 120, which are typically printed, etched, or otherwise formed on light guide 502, may be removed or unetched, printed, or otherwise formed in seam area 514. Seam area 514 may extend away from first edge 508 and second edge 510 along first light guide tile 504 and second light guide tile 506, respectively. The width of the seam area 514 may be determined through experiment and may vary depending on the structure and size of the light guide tiles. Experimental results indicated that the seam area could have a width of approximately 3 mm on the top surface of each light guide tile. In other examples, seam area 514 may have a width measured along the top surface of each light guide tile from about 0.5 mm to about 5 mm. In other examples, the seam area may have different widths.

Another step that can be taken to make the tile gap 512 (or tile seam) undetectable to the viewer is to add an auxiliary connector to the tile gap 512. The exemplary backlight unit 600 shows a configuration in which the auxiliary connector 610 is located between the light board 102 and the light guide 502. In the depicted configuration, auxiliary connector 610 is positioned at connector location 612 aligned with tile gap 512. When 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.

The auxiliary connector 610 may be similar to the auxiliary connector 410 described previously. Auxiliary connector 610 may be made of OCA or mounting tape, for example. However, supplemental connector 610 may extend along the entire gap or seam between adjacent light guide tiles, such as between first light guide tile 504 and second light guide tile 506. As shown, auxiliary connector 610 may be positioned between light sources 106 and aligned along first edge 508 and/or 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 gap 512). seams) and the auxiliary connector 610 may not be detected by the viewer of the backlight unit 600.

The optical properties of the auxiliary connector 610 or 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 so that the auxiliary connector and tile gap or seam is not connected to the backlight unit 600. It can be prevented from being detected by viewers. In some examples, the transparency or reflectivity of the auxiliary connector 610 may be adjusted such that the auxiliary connector and tile gap or seam are not detected by a viewer of the backlight unit 600. In other examples, the reflectivity of back reflector 110 may be adjusted so that a viewer of backlight unit 600 cannot detect auxiliary connectors and tile gaps or seams. For example, colored ink or other coating may be printed on the auxiliary connector 610 or the back reflector 110 at the connector location 612 to enable a viewer of the backlight unit 600 to detect the auxiliary connector and tile gaps or seams. You can make it so that it doesn't happen.

The experimental results verified that the structure of the backlight unit 600 shown in FIG. 6 was successfully implemented. In one experiment, a 5 mm wide polyester (PET) film strip was used as an auxiliary connector. The auxiliary connector was disposed between the light board and the edges of the first light guide tile and the second light guide tile. Before adding OCA to both sides of the PET film, a layer of yellow ink was printed on the PET film using a laser printer. The density of the yellow ink varied during testing. In one test, the density of yellow ink printed on PET film corresponded to an opacity of 10% as set in the image creation software. Measurements show that adding this density of yellow ink to PET film reduces film transmission to about 75% at blue wavelengths (450 nm), while PET film remains mostly transparent at green wavelengths (550 nm) and red wavelengths (650 nm). (measured at 92% due to reflection on both sides).

Based on the above experiments, it was confirmed that by adjusting the transmittance of the blue wavelength, the viewer of the backlight unit could not detect tile gaps and/or tile seams as well as auxiliary connectors. In instances where the transparency of the auxiliary connector (e.g. mounting tape) is adjusted, the transmittance of the auxiliary connector may need to be reduced to approximately 50% to 90% at blue wavelengths. In examples where the back reflector is adjusted and the auxiliary connector is substantially transparent or remains transparent, the reflectivity of the back reflector at the connector location can be reduced to 25% to 80% in blue wavelengths. Various embodiments may be used to implement changes in the optical properties of the auxiliary connector or back reflector. For example, low-density yellow ink can be printed on the top surface of an auxiliary connector (e.g., mounting tape). In another example, low density yellow ink may be printed on the bottom surface of an auxiliary connector (eg, mounting tape). In another example, low-density ink may be printed on the rear reflector surface at the connector location below a transparent auxiliary connector (e.g., mounting tape). In another example, a low-density yellow pigment can be added to the material of the auxiliary connector to color the auxiliary connector.

In the above experiments and the above recommended transmittance changes for auxiliary connectors and/or back reflectors, a light board containing LEDs emitting blue light was used. This often happens with the state-of-the-art backlight devices in modern displays. The backlight unit includes various optical films and other layers positioned over the light guide and/or light board tiles. A more complete backlight unit is shown in Figure 7. In this example, the previously described backlight unit 600 is shown having various optical layers and films 704 positioned adjacent to a bulk diffuser plate 702 and a light guide 502. Optical layers and films 704 may include, for example, Brightness Enhancement Film (BEF), Dual Brightness Enhancement Film (DBEF), reflective polarizer, diffusion film, quantum dot (QD) color May include a conversion layer. Quantum dot (QD) color conversion layers can be used to add red and green light to the backlight output. It should be noted that the optical layers and films 704 also serve to wash away any remaining local brightness changes that may be present in the backlight unit 600. Additionally, because the LEDs of the light board 102 included LEDs that emit blue light, attenuation by the auxiliary connector 610 at the edges of the first light guide tile 504 and the second light guide tile 506 There is an excess of blue light that needs to be turned off.

If other light boards are used, including light sources or LEDs that emit light of a different color or that emit white light, the optical properties of the auxiliary connector and/or back reflector may vary depending on whether the viewer of the backlight is exposed to the auxiliary connector and/or the tile gap or It can be adjusted to attenuate the required colors of light as needed so that tile seams cannot be detected. For example, if the light board includes light sources that emit white light and there is no quantum dot (QD) color conversion layer, at the edges of the first light guide tile 504 and the second light guide tile 504 The auxiliary connector used may have a medium gray color printed at the connector location to attenuate all colors by approximately the same amount as previously described for auxiliary connector 410 of Figure 4.

Another example backlight unit 800 is shown in FIG. 7 . 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. The backlight unit 800 is similar to the backlight unit described above. The backlight unit 800 allows light guide tiles 802, 804 to be coupled to the light board 806 using auxiliary connectors located both between the light sources 106 on a single light guide tile and at the edges of the light guide tiles. A possible embodiment is shown. As shown, the backlight unit 800 may include a first auxiliary connector 810 and a second auxiliary connector 820. The first auxiliary connector 810 may be located between the light sources 106 to add additional mechanical coupling strength for securing the second light guide tile 806 to the light board 806. The first auxiliary connector 810 may be similar to the previously described auxiliary connector 410. The transparency or reflectivity of the back reflector 110 of the first auxiliary connector 810 or at the first connector location 812 can be adjusted such that the first auxiliary connector 810 is not detected by the viewer of the backlight unit 800. there is.

The second auxiliary connector 820 has a second connector location 822 that can extend along the edge 814 of the first light guide tile 802 and along the edge 816 of the second light guide tile 804. It can be located in . The second auxiliary connector 820 is similar to the auxiliary connector 610 described above. The transparency or reflectivity of the rear reflector 110 of the second auxiliary connector 820 or at the second connector location 822 determines whether the second auxiliary connector 820 and the tile gap or tile seam are visible to the viewer of the backlight unit 800. can be adjusted to be undetectable.

As can be seen, the structure of backlight unit 800 can be reproduced in backlight units configured for use in large display units. Accordingly, auxiliary connectors, such as first auxiliary connector 810, may be included between each light source on the optical board including the array of light sources as described above. Additionally, auxiliary connectors, such as the second auxiliary connector 820, may be used in the seams between each light guide tile that can be used to build a large backlight unit. The second auxiliary connector 820 may extend in any direction along the edges of the light guide tiles.

Referring now to Figure 9, a method 900 of assembling a backlight unit is shown. The method 900 may be used, for example, to assemble one of the previously described backlight units. For simplicity, the backlight unit 800 shown in Figure 8 is used to describe the method 900. However, it should be understood that the above method (or variations thereof) may also be used to assemble the backlight units 400 and 600.

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

At step 904, auxiliary connectors may be positioned between the light sources. In the example backlight unit 800, first auxiliary connectors 810 may be located between light sources 106. The first auxiliary connectors 810 may be positioned at approximately the same distance from each light source 106. First auxiliary connectors 810 may be positioned on optical board 806 using adhesive or other connecting means. The first auxiliary connectors 810 may have optical properties that are different from the optical properties of the optical board in the area adjacent to the first connector location 812. As such, the first auxiliary connectors 810 may not be detected by a viewer of the backlight when the backlight unit is used in a display device.

At step 906, auxiliary connectors may be positioned at edge locations. In the example backlight 800, the second auxiliary connectors 820 are connected to 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. It can be located in a position aligned with . The second auxiliary connector 820 may be, for example, a length of mounting tape. The second auxiliary connector 820 may have optical properties that are different from the optical properties of the optical board in the area adjacent to the second connector location 822. In this way, the second auxiliary connector 820 and the edges 814, 816 may not be detected by a viewer of the backlight unit when the backlight unit is used in a display device.

At step 908, primary connectors may be applied to the light sources. In the example backlight unit 800, a layer of adhesive, such as an optically clear adhesive (OCA) or a mounting tape, is applied to the light sources 106 facing the first light guide tile 802 and/or the second light guide tile 804. Can be applied to surfaces.

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 the light guide tiles 802 and 804 of the light source 106, the first auxiliary connectors 810, and the second auxiliary connectors 820. A force may be applied to the light board 806 such that a force is applied to each location in contact with anything. For example, by pulling a vacuum to pull the light guide tiles 802, 804 and the light board 806 together, or by applying hydrostatic pressure to the light guide tiles 802, 804 and/or the light board 806. The applied force can be applied by doing so. In other examples, the applied force may be applied using other methods. As can be appreciated, 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 is connected to the light guide tiles 802, 804 and the light board ( 806) is aligned with the optical board to ensure that proper alignment is maintained between them.

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

The invention has been described in terms of exemplary embodiments, but is not limited thereto. Rather, the appended claims should be interpreted broadly to encompass other modifications and embodiments that may occur to those skilled in the art.

Claims (20)

As a backlight unit,
A light board including a first light source and a second light source;
a light guide positioned adjacent the light board to disperse light emitted from the first light source and the second light source; and
A connector positioned at a connector position between the first light source and the second light source to couple the light guide to the light board,
A backlight unit wherein the optical properties of the light board or of the connector at the connector location differ from the optical properties at adjacent locations such that the connector is not detectable by a viewer of the backlight unit. In claim 1,
A backlight unit, wherein the optical characteristics include transparency of the connector. In claim 1,
The backlight unit, wherein the connector is colored gray to reduce the transparency of the auxiliary connector. In claim 1,
A backlight unit, characterized in that the connector is colored yellow. In claim 1,
The backlight unit of claim 1, wherein the optical characteristics include a reflectance of the optical board at the connector location. In claim 1,
A backlight unit, characterized in that the reflectance of the optical board at the connector location is smaller than the reflectance of the optical board adjacent to the connector location. In claim 1,
The backlight unit, wherein the optical board includes a gray coating at the connector location. In claim 1,
The backlight unit, wherein the optical board includes a yellow coating at the connector location. In claim 1,
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. Backlight unit. In claim 1,
The backlight unit, wherein the light board includes an array of light sources, and the connector is located between adjacent light sources in the array of light sources. In claim 1,
The backlight unit is characterized in that the light guide is coupled to the first light source and the second light source. A backlight unit for use in a display, said backlight unit comprising:
An optical board including a plurality of light sources;
adjacent to each other and having a first edge of the first light guide tile positioned adjacent to a second edge of the second light guide tile to define a tile seam between the first light guide tile and the second light guide tile. positioned, the first light guide tile and the second light guide tile; and
A connector positioned between the light board and the first light guide tile and the second light guide tile at the tile seam, wherein the connector couples the first light guide tile and the second light guide tile to the light board. A backlight unit including the connector. In claim 12,
The portion of the optical board at the connection location of the connector has a lower reflectivity than adjacent portions of the optical board such that the connector and the first edge and the second edge are undetectable by a viewer of the backlight. A backlight unit characterized in that. In claim 13,
and wherein the reflectance of the portion of the light board at the connection position is reduced to have a reflectance of blue light in the range of about 25% to about 80%. In claim 12,
and the connector is colored to reduce light transmittance at the connector location of the connector such that the auxiliary connector and the first edge and the second edge cannot be detected by a viewer of the backlight. In claim 15,
A backlight unit, wherein the transmittance of blue light with a wavelength of about 450 nm is reduced to a range of about 50% to about 90% by the connector. A method of assembling a backlight unit, said method comprising:
positioning a connector on the optical board at a connector location between a first light source and a second light source; and
A method comprising: coupling a light guide plate to the light board at the connector location. In claim 17,
wherein the connector is colored to reduce light transmission at the connector location. In claim 17,
and wherein the portion of the optical board at the connector location has a lower reflectivity compared to adjacent portions of the optical board. In claim 17,
The method further comprising positioning the connector to align with an edge of the light guide plate.

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