WO2016087081A1 - A display device comprising a backlight unit - Google Patents

A display device comprising a backlight unit Download PDF

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Publication number
WO2016087081A1
WO2016087081A1 PCT/EP2015/072517 EP2015072517W WO2016087081A1 WO 2016087081 A1 WO2016087081 A1 WO 2016087081A1 EP 2015072517 W EP2015072517 W EP 2015072517W WO 2016087081 A1 WO2016087081 A1 WO 2016087081A1
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WO
WIPO (PCT)
Prior art keywords
optical element
display device
reflective sheet
light
optical
Prior art date
Application number
PCT/EP2015/072517
Other languages
French (fr)
Inventor
Chiu GOODSPEED
Original Assignee
Arcelik Anonim Sirketi
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Publication date
Application filed by Arcelik Anonim Sirketi filed Critical Arcelik Anonim Sirketi
Publication of WO2016087081A1 publication Critical patent/WO2016087081A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133611—Direct backlight including means for improving the brightness uniformity
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133605—Direct backlight including specially adapted reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133603—Direct backlight with LEDs
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133606—Direct backlight including a specially adapted diffusing, scattering or light controlling members
    • G02F1/133607—Direct backlight including a specially adapted diffusing, scattering or light controlling members the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Definitions

  • the present invention relates to a display device comprising a direct type backlight unit.
  • illumination of the display panel is realized by edge type and direct type backlight units.
  • direct type backlight units light sources like fluorescent or light emitting diodes are arranged at the rear of the display panel.
  • the display panel cannot be illuminated uniformly, the regions aligned with the light source behind the display panel are luminous and the regions between the light sources are relatively dark.
  • optical sheets such as the diffuser are placed between the display panel and the light sources, the intensity difference between the luminous and dark regions is decreased, and nevertheless effective results cannot be obtained. This situation adversely affects the quality of the image generated at the display panel. Arranging the light sources in a dense lattice is not preferred since the cost is high and the energy consumption of the display device increases.
  • a display device having patterns that enable light to be more uniformly spread at a light guide plate disposed above the light sources.
  • the aim of the present invention is the realization of a display device having a backlight unit that uniformly illuminates the display panel.
  • the display device realized in order to attain the aim of the present invention, and explicated in the first claim and the respective claims thereof, comprises more than one optical element that is used in the backlight unit, that is placed between the light sources, that is positioned so as to form protrusions on the reflective sheet and that enables the light to be transmitted to the upper optical sheet so as to be almost parallel to the surface normal direction of the reflective sheet.
  • the display device of the present invention light is transmitted to the dark areas remaining between the light sources and the dark areas are illuminated by means of the optical element.
  • the optical element Acting as a point source, the light source emits light in almost every direction and the light beams that travel in the direction of the reflective sheet surface cannot be utilized since they are not reflected to the optical sheet. Since the optical element forms a protrusion on the reflective sheet, the light beams parallel to the reflective sheet are effectively transmitted to the optical sheet. The optical element transmits the incident light thereon to the optical sheet almost in the surface normal direction, thereby partially functioning as a light source.
  • the optical elements are fabricated so that each remains between two adjacent light sources.
  • the optical element is enabled to receive light from all directions. Thus, no dark area remains.
  • the intensity difference between the dark areas and illuminated areas increase since light cannot be transmitted between two optical elements.
  • the optical element is positioned at equal distances to the two adjacent light sources.
  • the intensity profile of the light falling on the display panel is symmetrical and almost equal. Accordingly, the image generated on the display panel is enabled to be effectively illuminated.
  • the length of the optical element is at most equal to the length of the light source remaining on the reflective sheet.
  • the length of the optical element is determined in direct proportion with the distance between the adjacent light sources.
  • the length of the optical element between diagonally adjacent light sources is longer than the length of the optical element between oppositely adjacent light sources.
  • the optical element is designed as a ring and the incident rays on the optical element are refracted inside the optical element to be transmitted in a direction parallel to the normal direction of the reflective sheet surface.
  • the optical element is in form of a hemisphere.
  • the incident rays on the hemispherical optical element are reflected so as to be parallel to the normal direction of the reflective sheet surface to a large extent.
  • the optical element is fabricated in simple geometric shapes such as ring, cylinder, and quadrangular prism or in complex geometric shapes such as triangular prism, truncated cylinder, quadrangular prism, or spherical cap.
  • the geometry that provides the most effective function is selected depending on the fabrication method and the fabrication material of the optical element.
  • the optical element is preferably shaped as a hemisphere or spherical cap.
  • the optical element is adhered on the reflective sheet.
  • This embodiment is preferably used in the fabrication of optical elements manufactured from different materials or in complex geometries.
  • the optical element is manufactured by punching embossing on the reflective sheet.
  • the optical element is fabricated with paint material comprising metal particles with high reflective features.
  • metals such as aluminum, silver or gold the optical element is enabled to have 98% or higher reflective character.
  • the optical element is fabricated from plastic material or similarly functional material, such that the surfaces receiving light from the light source are translucent and the surfaces facing the optical sheet are transparent.
  • the rays transmitted from the light source is refracted into the optical element and guided inside the optical element and enabled to be reflected almost perpendicularly to the optical sheet.
  • the light supplied by the backlight unit is enabled to have almost equal intensity profile.
  • the optical elements used in the solution using additional optical sheets is not required and thus the display device can be designed thinner and furthermore cost advantage is provided.
  • Figure 1 – is the schematic view of a display device.
  • Figure 2 – is the schematic view of a display panel and a backlight unit.
  • Figure 3 – is the schematic view of light sources and optical elements positioned on a reflective sheet.
  • Figure 4 – is the schematic perspective view of the light sources and the optical elements positioned on the reflective sheet related to another embodiment of the present invention.
  • Figure 5 — is the perspective view of the light sources and the optical elements positioned on the reflective sheet related to yet another embodiment of the present invention.
  • the display device (1) comprises a body (2), a display panel (3) that is disposed inside the body (2) and that generates the images and a backlight unit (4) disposed inside the body (2) and behind the display panel (3).
  • the backlight unit (4) comprises
  • the display panel (3), the optical sheet (8) and the reflective sheet (5) are positioned at planes almost parallel to one another.
  • the optical sheet (8) functions as the diffuser or the light guide.
  • the light sources (7) are placed into the holes (6) that are disposed in two-dimensional matrix arrangement on the reflective sheet (5).
  • the rays emitted from the light sources (7) are partially and uniformly diffused on the optical sheet (8) and the display panel (3) is illuminated.
  • the rays that reflect back from the optical sheet (8) are regained by being reflected towards the optical sheet (8) depending on the angle of incidence by means of the reflective sheet (5).
  • the light sources (7) are preferably light emitting diodes with a point source feature and the reflective sheet (5) has preferably a 90% or higher reflectivity.
  • the display device (1) of the present invention comprises at least one optical element (9) that is disposed between the holes (6) so as to form protrusions on the reflective sheet (5) and that prevents the dark areas between the light sources (7) by transmitting the light originating from the light source (7) and falling thereon almost perpendicularly to the surface of the reflective sheet (5) and towards the optical sheet (8).
  • the optical element (9) is positioned on the reflective sheet (5) between the holes (6) so as to have a certain height over the reflective sheet (5).
  • the optical element (9) reflects or refracts the rays coming directly thereon from the light source (7) or the rays reflected back from the optical sheet (8) almost perpendicularly to the reflective sheet (5) surface partially regardless of the angle of incidence.
  • the distance that light travels is shortened by means of the optical element (9) having a higher refractive index than air.
  • the optical element (9) is protuberant with respect to the surface of the reflective sheet (5), the rays from the light source (7) that travel almost parallel to the surface of the reflective sheet (5) and fade before being utilized effectively are directed to the optical sheet (8).
  • the said problem is solved without using more light sources (7).
  • one optical element (9) is positioned between each two light sources (7).
  • light is enabled to fall on each optical element (9).
  • the optical elements (9) are prevented from keeping one another in the dark.
  • the optical element (9) is positioned so as to be at equal distances to each two light sources (7).
  • the light reflected to the optical sheet (8) is enabled to homogeneously illuminate the surface of the optical sheet (8).
  • the height of the optical element (9) remaining on the reflective sheet (5) is at most equal to the height of the light source (7) remaining on the reflective sheet (5).
  • the optical elements (9) are prevented from blocking the light of the light source (7).
  • the height of the optical element (9) remaining on the reflective sheet (5) is directly proportional to the distance between two adjacent light sources (7) on the same direction.
  • longer optical elements (9) can be positioned therebetween.
  • the beam of light emitted from the light source (7) with different angles of incidence is perceived by the optical element (9) as parallel beams of light and the said beam of light is enabled to be reflected over the optical element (9) by increasing the height of the optical element (9) and the beams of light that are almost parallel to the surface of the reflective sheet (5) are prevented from fading without being reflected from any surface.
  • the optical element (9) is in the form of a hemisphere.
  • the hemispherical optical element (9) is fabricated such that the flat portion thereof is on the reflective sheet (5).
  • the optical element (9) is hemispherical, most of the beams of light falling thereon are reflected perpendicularly to the surface of the reflective sheet (5) and thus an effect is created that as if there is a light source (7) at a point where there is no light source (7).
  • the optical element (9) is shaped as a ring.
  • the beams of light falling on the optical element (9) are enabled to fall on the optical element (9) perpendicularly to the surface normal direction.
  • the beams of light refracted from the optical element (9) are enabled to be reflected to the surface of the ring-shaped optical element (9) at almost a right angle.
  • the optical element (9) has different geometries such as ring, quadrangular prism, truncated quadrangular prism, hemisphere, spherical cap, cylinder, truncated cylinder and triangular prism.
  • the optical element (9) is fabricated by printing pattern methods.
  • the optical elements (9) are easily fabricated on the reflective sheet (5) used especially in the display devices (1) comprising large display panels (3) by means of the printing pattern method that enables fast and precise fabrication for mass production.
  • the print patterning method the state of the art gravure printing, photolithography and similar methods are used.
  • the optical element (9) is fabricated by being adhered onto the reflective sheet (5).
  • the optical element (9) that is fabricated separately from the reflective sheet (5) is fixed on the reflective sheet (5) by adhesion.
  • This embodiment is used preferably in the positioning of the optical element (9) on the reflective sheet (5) that has complex geometrical shapes or that is hard to fabricate or costly with other manufacturing methods.
  • the optical element (9) is fabricated by the punching embossing method on the reflective sheet (5).
  • the optical element (9) is fabricated by punching embossing on the reflective sheet (5) so as to remain between the holes (6).
  • the optical element (9) is fabricated from paint comprising a metal ingredient having high reflectivity property preferably such as aluminum or silver.
  • the optical element (9) enables the light falling thereon to be almost completely reflected without absorbing.
  • the optical element (9) used in this embodiment is fabricated by punching embossing or adhesion methods.
  • the optical element (9) is fabricated from plastic, the upper surface of which is transparent and the side surface of which is translucent. In this embodiment, some of the light falling on the optical element (9) is reflected from the optical element (9) and some portion is refracted and passed to the optical element (9) and coupled inside the optical element (9) and is passed to the optical sheet (8) refracting from the transparent upper surface by making total internal reflection inside the optical element (9).
  • the optical elements (9) by enabling the optical elements (9) to act as light sources (7) by the effect of optical principles like reflection, refraction, total internal reflection of the light emitted from the light sources (7) on the optical elements (9) positioned on the reflective sheet (5), the dark areas formed between the light sources (7) are eliminated and thus the backlight unit (4) is enabled to be an almost planar light source (7).

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Planar Illumination Modules (AREA)

Abstract

The present invention relates to a display device (1) comprising a body (2), a display panel (3) that is disposed inside the body (2) and that generates the images, and a backlight unit (4) that is disposed inside the body (2) and behind the display panel (3) and that has a reflective sheet (5) having more than one hole (6) arranged along its surface, more than one light source (7) that is seated into the holes (6) and that provides the illumination of the display panel (3) and at least one optical sheet (8) that is disposed between the display panel (3) and the reflective sheet (5) and that enables the light to be propagated or diffused. The backlight further comprises optical elements (9) that are disposed between the holes (6) so as to form protrusions on the reflective sheet (5) and that prevents the dark areas between the light sources (7) by reflecting or refracting the light originating from the light source (7) towards the optical sheet (8).

Description

A DISPLAY DEVICE COMPRISING A BACKLIGHT UNIT
The present invention relates to a display device comprising a direct type backlight unit.
In display devices using liquid crystal display panels, illumination of the display panel is realized by edge type and direct type backlight units. In direct type backlight units, light sources like fluorescent or light emitting diodes are arranged at the rear of the display panel. However, as a result of the optical effects such as the destructive interference between the beams emitted from the light sources and the light intensity being inversely proportional with the square of the distance the light travels, the display panel cannot be illuminated uniformly, the regions aligned with the light source behind the display panel are luminous and the regions between the light sources are relatively dark. In order to solve this problem, optical sheets such as the diffuser are placed between the display panel and the light sources, the intensity difference between the luminous and dark regions is decreased, and nevertheless effective results cannot be obtained. This situation adversely affects the quality of the image generated at the display panel. Arranging the light sources in a dense lattice is not preferred since the cost is high and the energy consumption of the display device increases.
In the state of the art United States Patent Application No. US2014321157, a display device is disclosed, having patterns that enable light to be more uniformly spread at a light guide plate disposed above the light sources.
In the state of the art Chinese Patent Application No. CN202546506, a display device is disclosed, wherein the light sources are disposed within the cavities formed by bending the reflective sheet.
In the state of the art Korean Patent Application No. KR20080055316, a display device is disclosed, having partition walls that enable the light sources to be separated into groups and contact the upper optical sheet.
The aim of the present invention is the realization of a display device having a backlight unit that uniformly illuminates the display panel.
The display device realized in order to attain the aim of the present invention, and explicated in the first claim and the respective claims thereof, comprises more than one optical element that is used in the backlight unit, that is placed between the light sources, that is positioned so as to form protrusions on the reflective sheet and that enables the light to be transmitted to the upper optical sheet so as to be almost parallel to the surface normal direction of the reflective sheet.
In the display device of the present invention, light is transmitted to the dark areas remaining between the light sources and the dark areas are illuminated by means of the optical element. Acting as a point source, the light source emits light in almost every direction and the light beams that travel in the direction of the reflective sheet surface cannot be utilized since they are not reflected to the optical sheet. Since the optical element forms a protrusion on the reflective sheet, the light beams parallel to the reflective sheet are effectively transmitted to the optical sheet. The optical element transmits the incident light thereon to the optical sheet almost in the surface normal direction, thereby partially functioning as a light source.
In an embodiment of the present invention, the optical elements are fabricated so that each remains between two adjacent light sources. By means of this embodiment, the optical element is enabled to receive light from all directions. Thus, no dark area remains. When the optical element is fabricated so that there is more than one between the light sources, the intensity difference between the dark areas and illuminated areas increase since light cannot be transmitted between two optical elements.
In another embodiment of the present invention, the optical element is positioned at equal distances to the two adjacent light sources. Thus, the intensity profile of the light falling on the display panel is symmetrical and almost equal. Accordingly, the image generated on the display panel is enabled to be effectively illuminated.
In another embodiment of the present invention, the length of the optical element is at most equal to the length of the light source remaining on the reflective sheet. By adjusting the length of the optical element thusly, the light delivered by means of the light sources and the optical elements to the optical sheet is enabled to act as a planar source. When the length of the optical element is higher than the light source, the optical element may block the light of the light source. By means of this embodiment, contribution in obtaining light intensity having an almost linear profile along the display panel is provided.
In another embodiment of the present invention, the length of the optical element is determined in direct proportion with the distance between the adjacent light sources. For example, the length of the optical element between diagonally adjacent light sources is longer than the length of the optical element between oppositely adjacent light sources. Thus, an equal light intensity profile is provided by the arrangement of the optical elements of different lengths and the lights sources, the distances therebetween being different in different directions.
In an embodiment of the present invention, the optical element is designed as a ring and the incident rays on the optical element are refracted inside the optical element to be transmitted in a direction parallel to the normal direction of the reflective sheet surface.
In an embodiment of the present invention, the optical element is in form of a hemisphere. The incident rays on the hemispherical optical element are reflected so as to be parallel to the normal direction of the reflective sheet surface to a large extent.
In another embodiment of the present invention, the optical element is fabricated in simple geometric shapes such as ring, cylinder, and quadrangular prism or in complex geometric shapes such as triangular prism, truncated cylinder, quadrangular prism, or spherical cap. In this embodiment, the geometry that provides the most effective function is selected depending on the fabrication method and the fabrication material of the optical element. For example, in the embodiment of half-transparent plastic optical element fabricated by adhesion method on the reflective sheet, the optical element is preferably shaped as a hemisphere or spherical cap.
In another embodiment of the present invention, in the fabrication of the optical element printing pattern methods are used, that enable fast, precise and low cost printing on wide surfaces.
In another embodiment of the present invention, the optical element is adhered on the reflective sheet. This embodiment is preferably used in the fabrication of optical elements manufactured from different materials or in complex geometries.
In another embodiment of the present invention, the optical element is manufactured by punching embossing on the reflective sheet. By means of this embodiment, the said problem is solved in a low cost manner without using additional materials.
In another embodiment of the present invention, the optical element is fabricated with paint material comprising metal particles with high reflective features. By using metals such as aluminum, silver or gold the optical element is enabled to have 98% or higher reflective character.
In another embodiment of the present invention, the optical element is fabricated from plastic material or similarly functional material, such that the surfaces receiving light from the light source are translucent and the surfaces facing the optical sheet are transparent. In this embodiment, the rays transmitted from the light source is refracted into the optical element and guided inside the optical element and enabled to be reflected almost perpendicularly to the optical sheet.
By means of the present invention, the light supplied by the backlight unit is enabled to have almost equal intensity profile. By means of the optical elements used in the solution, using additional optical sheets is not required and thus the display device can be designed thinner and furthermore cost advantage is provided.
The display device realized in order to attain the aim of the present invention is illustrated in the attached figures, where:
Figure 1 – is the schematic view of a display device.
Figure 2 – is the schematic view of a display panel and a backlight unit.
Figure 3 – is the schematic view of light sources and optical elements positioned on a reflective sheet.
Figure 4 – is the schematic perspective view of the light sources and the optical elements positioned on the reflective sheet related to another embodiment of the present invention.
Figure 5 – is the perspective view of the light sources and the optical elements positioned on the reflective sheet related to yet another embodiment of the present invention.
The elements illustrated in the figures are numbered as follows:
1. Display device
2. Body
3. Display panel
4. Backlight unit
5. Reflective sheet
6. Hole
7. Light source
8. Optical sheet
9. Optical element
The display device (1) comprises a body (2), a display panel (3) that is disposed inside the body (2) and that generates the images and a backlight unit (4) disposed inside the body (2) and behind the display panel (3).
The backlight unit (4) comprises
  • a reflective sheet (5) having more than one hole (6) arranged in a grid-like manner along its surface,
  • more than one light source (7) that is seated into the holes (6) and that provides the illumination of the display panel (3), and
  • at least one optical sheet (8) that is disposed between the display panel (3) and the reflective sheet (5) and that enables the light to be propagated or diffused.
In the display device (1), the display panel (3), the optical sheet (8) and the reflective sheet (5) are positioned at planes almost parallel to one another. The optical sheet (8) functions as the diffuser or the light guide. The light sources (7) are placed into the holes (6) that are disposed in two-dimensional matrix arrangement on the reflective sheet (5). The rays emitted from the light sources (7) are partially and uniformly diffused on the optical sheet (8) and the display panel (3) is illuminated. The rays that reflect back from the optical sheet (8) are regained by being reflected towards the optical sheet (8) depending on the angle of incidence by means of the reflective sheet (5). In the display device (1) of the present invention, the light sources (7) are preferably light emitting diodes with a point source feature and the reflective sheet (5) has preferably a 90% or higher reflectivity.
The display device (1) of the present invention comprises at least one optical element (9) that is disposed between the holes (6) so as to form protrusions on the reflective sheet (5) and that prevents the dark areas between the light sources (7) by transmitting the light originating from the light source (7) and falling thereon almost perpendicularly to the surface of the reflective sheet (5) and towards the optical sheet (8).
The optical element (9) is positioned on the reflective sheet (5) between the holes (6) so as to have a certain height over the reflective sheet (5). The optical element (9) reflects or refracts the rays coming directly thereon from the light source (7) or the rays reflected back from the optical sheet (8) almost perpendicularly to the reflective sheet (5) surface partially regardless of the angle of incidence. In the refraction of light, the distance that light travels is shortened by means of the optical element (9) having a higher refractive index than air. As the optical element (9) is protuberant with respect to the surface of the reflective sheet (5), the rays from the light source (7) that travel almost parallel to the surface of the reflective sheet (5) and fade before being utilized effectively are directed to the optical sheet (8). Thus, the said problem is solved without using more light sources (7).
In an embodiment of the present invention, one optical element (9) is positioned between each two light sources (7). By means this embodiment, light is enabled to fall on each optical element (9). Thus, the optical elements (9) are prevented from keeping one another in the dark.
In another embodiment of the present invention, the optical element (9) is positioned so as to be at equal distances to each two light sources (7). By means this embodiment, the light reflected to the optical sheet (8) is enabled to homogeneously illuminate the surface of the optical sheet (8).
In another embodiment of the present invention, the height of the optical element (9) remaining on the reflective sheet (5) is at most equal to the height of the light source (7) remaining on the reflective sheet (5). By means of this embodiment, the optical elements (9) are prevented from blocking the light of the light source (7).
In another embodiment of the present invention, the height of the optical element (9) remaining on the reflective sheet (5) is directly proportional to the distance between two adjacent light sources (7) on the same direction. In this embodiment, as the distance between the light sources (7) increases, longer optical elements (9) can be positioned therebetween. When two light sources (7) are very close to each other, the light is enabled to fall on the optical element (9) with more than one angle of incidence by placing a relatively shorter optical element (9) therebetween and the reflected beam of light is enabled to illuminate a larger area. When two light sources (7) are relatively farther away from each other, the beam of light emitted from the light source (7) with different angles of incidence is perceived by the optical element (9) as parallel beams of light and the said beam of light is enabled to be reflected over the optical element (9) by increasing the height of the optical element (9) and the beams of light that are almost parallel to the surface of the reflective sheet (5) are prevented from fading without being reflected from any surface.
In an embodiment of the present invention, the optical element (9) is in the form of a hemisphere. The hemispherical optical element (9) is fabricated such that the flat portion thereof is on the reflective sheet (5). When the optical element (9) is hemispherical, most of the beams of light falling thereon are reflected perpendicularly to the surface of the reflective sheet (5) and thus an effect is created that as if there is a light source (7) at a point where there is no light source (7).
In another embodiment of the present invention, the optical element (9) is shaped as a ring. By means of the ring-shaped optical element (9), the beams of light falling on the optical element (9) are enabled to fall on the optical element (9) perpendicularly to the surface normal direction. The beams of light refracted from the optical element (9) are enabled to be reflected to the surface of the ring-shaped optical element (9) at almost a right angle.
In another embodiment of the present invention, the optical element (9) has different geometries such as ring, quadrangular prism, truncated quadrangular prism, hemisphere, spherical cap, cylinder, truncated cylinder and triangular prism.
In another embodiment of the present invention, the optical element (9) is fabricated by printing pattern methods. In this embodiment, the optical elements (9) are easily fabricated on the reflective sheet (5) used especially in the display devices (1) comprising large display panels (3) by means of the printing pattern method that enables fast and precise fabrication for mass production. As the print patterning method, the state of the art gravure printing, photolithography and similar methods are used.
In another embodiment of the present invention, the optical element (9) is fabricated by being adhered onto the reflective sheet (5). In this embodiment, the optical element (9) that is fabricated separately from the reflective sheet (5) is fixed on the reflective sheet (5) by adhesion. This embodiment is used preferably in the positioning of the optical element (9) on the reflective sheet (5) that has complex geometrical shapes or that is hard to fabricate or costly with other manufacturing methods.
In another embodiment of the present invention, the optical element (9) is fabricated by the punching embossing method on the reflective sheet (5). In this embodiment, the optical element (9) is fabricated by punching embossing on the reflective sheet (5) so as to remain between the holes (6). By forming a protrusion on the reflective sheet (5) with punching embossing, the beam of light from the light source (7) is reflected parallel to the reflective sheet (5) surface by maintaining the cost advantage.
In another embodiment of the present invention, the optical element (9) is fabricated from paint comprising a metal ingredient having high reflectivity property preferably such as aluminum or silver. In this embodiment, the optical element (9) enables the light falling thereon to be almost completely reflected without absorbing. The optical element (9) used in this embodiment is fabricated by punching embossing or adhesion methods.
In another embodiment of the present invention, the optical element (9) is fabricated from plastic, the upper surface of which is transparent and the side surface of which is translucent. In this embodiment, some of the light falling on the optical element (9) is reflected from the optical element (9) and some portion is refracted and passed to the optical element (9) and coupled inside the optical element (9) and is passed to the optical sheet (8) refracting from the transparent upper surface by making total internal reflection inside the optical element (9).
In the display device (1) of the present invention, by enabling the optical elements (9) to act as light sources (7) by the effect of optical principles like reflection, refraction, total internal reflection of the light emitted from the light sources (7) on the optical elements (9) positioned on the reflective sheet (5), the dark areas formed between the light sources (7) are eliminated and thus the backlight unit (4) is enabled to be an almost planar light source (7).

Claims (12)

  1. A display device (1) comprising a body (2), a display panel (3) disposed inside the body (2), and a backlight unit (4) that is disposed inside the body (2) and behind the display panel (3) and that has
    - a reflective sheet (5) having more than one hole (6) arranged grid-like along its surface,
    more than one light source (7) that is seated into the holes (6) and that provides the illumination of the display panel (3), and
    - at least one optical sheet (8) that is disposed between the display panel (3) and the reflective sheet (5) and that enables the light to be propagated or diffused
    characterized by at least one optical element (9) that is disposed between the holes (6) so as to form protrusions on the reflective sheet (5) and that prevents the dark areas between the light sources (7) by transmitting the light originating from the light source (7) and falling thereon almost perpendicularly to the surface of the reflective sheet (5) and towards the optical sheet (8).
  2. A display device (1) as in Claim 1, characterized by the optical elements (9) positioned so that each remains between each two light sources (7).
  3. A display device (1) as in Claim 1, characterized by the optical element (9) positioned so as to be equidistant to each two light sources (7).
  4. A display device (1) as in any one of the above claims, characterized by the optical element (9), the height of which remaining on the reflective sheet (5) is at most equal to the height of the light source (7) remaining on the reflective sheet (5).
  5. A display device (1) as in any one of the above claims, characterized by the optical element (9), the height of which remaining on the reflective sheet (5) is directly proportional to the distance between two adjacent light sources (7).
  6. A display device (1) as in any one of the above claims, characterized by the hemispherical optical element (9).
  7. A display device (1) as in any one of the above claims, characterized by the ring-shaped optical element (9).
  8. A display device (1) as in any one of the above claims, characterized by the optical element (9) that is fabricated by printing pattern methods .
  9. A display device (1) as in any one of the above claims, characterized by the optical element (9) that is fabricated by being adhered on the reflective sheet (5) .
  10. A display device (1) as in any one of the above claims, characterized by the optical element (9) that is fabricated by punching embossing method on the reflective sheet (5) .
  11. A display device (1) as in any one of the above claims, characterized by the optical element (9) that is fabricated from paint comprising a metal ingredient having high reflectivity property preferably such as aluminum or silver.
  12. A display device (1) as in any one of the above claims, characterized by the optical element (9) that is fabricated from plastic, the upper surface of which is transparent and the side surface of which is translucent.
PCT/EP2015/072517 2014-12-03 2015-09-30 A display device comprising a backlight unit WO2016087081A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TRA2014/14610 2014-12-03
TR201414610 2014-12-03

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WO2018224450A1 (en) * 2017-06-05 2018-12-13 Lumileds Holding B.V. Optical lens for extremely thin direct-lit backlight
US11242977B2 (en) 2017-07-26 2022-02-08 Lumileds Llc Illumination device with element having annular coating

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KR20080055316A (en) 2006-12-15 2008-06-19 엘지디스플레이 주식회사 Back light unit and liquid crystal display device using the same
US20130070165A1 (en) * 2010-06-15 2013-03-21 Takaharu Shimizu Lighting device, display device and television device
US20130148036A1 (en) * 2010-08-31 2013-06-13 Sharp Kabushiki Kaisha Lighting device, display device and television device
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Publication number Priority date Publication date Assignee Title
WO2018224450A1 (en) * 2017-06-05 2018-12-13 Lumileds Holding B.V. Optical lens for extremely thin direct-lit backlight
US10578278B2 (en) 2017-06-05 2020-03-03 Lumileds Holding B.V. Optical lens for extremely thin direct-lit backlight
US11242977B2 (en) 2017-07-26 2022-02-08 Lumileds Llc Illumination device with element having annular coating

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