WO2007100458A1 - Improved light control film composite and lcd device comprising the same - Google Patents

Improved light control film composite and lcd device comprising the same Download PDF

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Publication number
WO2007100458A1
WO2007100458A1 PCT/US2007/003289 US2007003289W WO2007100458A1 WO 2007100458 A1 WO2007100458 A1 WO 2007100458A1 US 2007003289 W US2007003289 W US 2007003289W WO 2007100458 A1 WO2007100458 A1 WO 2007100458A1
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WO
WIPO (PCT)
Prior art keywords
film
louver
light control
light
control film
Prior art date
Application number
PCT/US2007/003289
Other languages
French (fr)
Inventor
Ji-Hyung Kim
Original Assignee
3M Innovative Properties Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2007100458A1 publication Critical patent/WO2007100458A1/en

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Classifications

    • 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
    • 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
    • G02F1/133524—Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
    • 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
    • G02F1/133528—Polarisers
    • 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
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side

Definitions

  • the present invention relates to a light control film comprising louver elements and to an LCD device comprising the same.
  • an LCD device comprises a liquid crystal display panel (also referred to as a "liquid crystal panel”) and a light source, i.e. a backlight, which illuminates the liquid crystal panel from the back surface (i.e. the surface opposite of the display surface).
  • a liquid crystal display panel also referred to as a "liquid crystal panel”
  • a light source i.e. a backlight
  • the typical LCD device also has a pair of first and second polarizers placed on either side of the liquid crystal panel.
  • the polarizers are placed so that the polarization axes of the first polarizer and of the second polarizer (first and second polarization axes, respectively) form a certain angle, for example, a right angle.
  • An example of the backlight is an edge-light type backlight, which comprises a light-guide plate and a light source that supplies light to the light-guide plate from the edge face of the plate.
  • the backlight can be a direct-lit type backlight, wherein one or more light sources are placed behind the back surface of the liquid crystal panel within the output area of the display.
  • the LCD device is an automobile-loaded equipment, such as a car navigation system, the reflection from the panel of the LCD device on the windshield may interfere with the vision of the driver. .
  • the display panel can be equipped with a privacy filter that prevents the unnecessary propagation of light emitted by the liquid crystal panel in directions away from the viewing axis.
  • a privacy filter is a louver film having a plurality of minute louvers (or louver-form elements) inside.
  • the louver film can be attached to the display screen to guard privacy and prevent unwanted reflections on vehicle windows.
  • the plurality of minute louvers built into the louver film can control the propagation directions of the light beams that are transmitted through the louver film and set a specific exiting angle range (direction control effect).
  • Such a louver film is also a light control film.
  • louver films The construction, manufacturing and application of louver films are disclosed in some prior publications.
  • U.S. Patent No. RE 27,617 discloses a method for producing a louver film by skiving a billet consisting of alternating plastic layers having a relatively low optical density (transparent) and a relatively high optical density (colored).
  • the colored layers provide louver-form elements, which collimate the light beam. These elements can extend in the direction perpendicular to the surface of the louver film.
  • U.S. Patent No. 3,707,416 discloses a method for slanting the louver- form elements, which collimate the light beam, relative to the surface of the louver film.
  • U.S. Patent No. 3,919,559 discloses a method for gradually changing the slant angles of the louver elements.
  • the method for producing the louver layer is disclosed in the above prior art.
  • a layer containing the light-shielding material is fixed to one main surface of a polymer film used as the light-transmitting part to form the louver-form elements, resulting in a laminate film consisting of the polymer film and the light-shielding material layer.
  • a plurality of such laminate films are prepared and laminated to form a precursor louver film, in which the polymer film and the light-shielding material layers are alternately arranged and fixed to each other.
  • the precursor louver film is skived at a desired thickness along the direction (lamination direction) perpendicular to the main surface (laminated plane) to obtain the louver layer.
  • U.S. Patent Application No. 2004/130788 discloses an optical filter comprising a louver film and an adhesive layer, which is used to adhere the louver film to a surface.
  • the louver film generally has a louver layer comprising light- transmitting parts and minute louver elements, which shield the light inside, and a backside and surface side substrate, which are fixed to the louver layer.
  • a conventional light control film containing louver elements is shown in Fig. 1.
  • the two window substrates fixed to the louver layer preferably are made thick enough to suppress warping or curling of the louver layer and the resulting louver film which comprises it. These window substrates also protect the louver layer from damage.
  • using such a louver film in a conventional LCD device can undesirably increase the overall thickness and decrease the light transmittance of the LCD device.
  • the invention includes a light control film composite.
  • the light control film includes a louver film layer and a first substrate layer laminated to a front surface of the louver film layer.
  • a second substrate layer is laminated to a rear surface of the louver film layer.
  • At least one of the first and second substrate layers is an optical conditioning film.
  • FIG. 1 is a schematic view of a conventional light control film comprising louver elements.
  • FIG. 2 is a schematic view representing one embodiment of the light control film composite according to the present invention.
  • FIG. 3 is a schematic view representing the construction of an LCD device without a light control film.
  • FIG. 4 is a schematic view representing the construction of an LCD device with a conventional light control film.
  • FIG. 5 is a schematic view representing the construction of an LCD device with the light control film composite according to the present invention in front of the liquid crystal panel.
  • FIG. 6 is a schematic view representing the construction of an LCD device with the light control film composite according to the present invention in the rear of the liquid crystal panel.
  • a conventional light control film comprising a louver layer essentially contains window substrates to suppress the warp or curl of the louver layer
  • the louver film when used in an LCD device, the overall thickness of the LCD device is increased and the light transmittance of the LCD device is inevitably decreased.
  • Fig. 1 schematically represents a conventional light control film (or louver film) comprising louver elements.
  • the film comprises a louver layer containing louver elements and window substrates fixed to both surfaces of the louver layer by adhesive layers.
  • the louver layer (12) has minute louvers (or louver-form elements) (15) inside the film.
  • the louver layer (12) comprises light-transmitting parts (17) and minute louver elements (15), which shield light.
  • the width of the light-transmitting part (17) is larger than the width of the louver element (the dimension of the louver element in the direction parallel to the surface of the louver layer and perpendicular to the lengthwise direction of the louver element), so that the light transmittance of the light control film (10) as a whole does not significantly decrease.
  • the width of the light-transmitting part is preferably from 50 to 500 ⁇ m, more preferably from 70 to 200 ⁇ m.
  • the width of the louver element may range from 1 to 100 ⁇ m, preferably from 10 to 50 ⁇ m.
  • the angle (13) of the louver element, an angle between the surface of the louver layer and the plane of the louver element, is usually from 40 to 90 degrees. When the louver element lies at a right angle with the surface of the louver layer, the angle (13) of the louver element is 90 degrees.
  • the thickness of the louver layer (12) can be suitably determined according to the application of the light control film (10). As the thickness of the louver layer (12) decreases, the control of the propagation direction of light tends to decrease. However, since increased thickness is undesirable, the desired control and thickness should be balanced in view of the application. As only an exemplary consideration, the thickness of the louver layer (12) is preferably from 10 to 1,000 ⁇ m, and more preferably from 40 to 500 ⁇ m.
  • the light-transmitting parts (17) of the louver layer (12) are preferably made of a polymer having a high transparency. For example, a thermoplastic resin, a thermosetting resin, or a resin curable with an actinic ray such as UV ray may be used.
  • Such resins include cellulose resins (e.g. cellulose acetate butyrate and triacetylcellulose), polyolefin resins (e.g. polyethylene and polypropylene), polyester resins (e.g. polyethylene terephthalate), polystyrene, polyurethane, polyvinyl chloride, acrylic resins, and polycarbonate resins.
  • the louver elements (15) may be formed from a light-shielding material, which can absorb or reflect light. Examples of such materials include (1) dark pigments or dark dyes, such as black or gray pigments or dyes, (2) metal, such as aluminum, silver, etc., (3) dark metal oxides, and (4) the above-described polymers containing dark pigments or dyes. Other films can be fixed to the louver film by using the adhesive layer (16).
  • the adhesive layer (16) may be formed of a conventional adhesive, such as a pressure-sensitive adhesive, a heat-sensitive adhesive, or a curable adhesive. The thickness of each adhesive layer is usually from 5 to 50 ⁇ m.
  • the two window substrates (14) fixed to the louver layer (12) preferably suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the louver film (10) comprising the louver layer (12), and the surface side substrate also functions as a protective layer to protect the louver layer (12) from damage.
  • louver film (10) in a conventional LCD device increases the overall thickness of the LCD device and inevitably decreases the light transmittance of the LCD device.
  • the present invention provides a light control film composite comprising a louver film, a first substrate layer laminated to a rear surface of the louver film layer and a second substrate layer laminated to a rear surface of the louver film layer, at least one of said first and second substrate layers being an optical conditioning film.
  • the optical conditioning film of the present invention may be an absorbing polarizer, a reflective polarizer, a prismatic film or a diffuser film.
  • Fig. 2 schematically represents a light control film composite (20) according to the present invention, both of a first substrate layer (22) and a second substrate layer (24) being polarizers.
  • polarizers (22 and 24) are attached to a louver layer (12) through adhesive layers (16) and can also function to suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the light control film composite (20).
  • the polarizer films (22 and 24) can be each independently an absorbing polarizer or a reflective polarizer.
  • the absorbing polarizer may be a plane polarizer or a circular polarizer.
  • a plane polarizer absorbs light of one polarization orientation more strongly than the light of the orthogonal polarization orientation.
  • plane polarizers include a dichromic polarizer such as an H-type (iodine) polarizer and a dyestuff polarizer, an intrinsic polarizer such as a K-type polarizer and an improved K-type polarizer (referred to as a KE polarizer as manufactured by 3M Company, Norwood, Mass.), and a thinly cladded or encapsulated polarizer.
  • a circular polarizer blocks one of left-handed (L) or right-handed (R) circularly polarized light and transmits light of the other polarization state, and may be constructed of a plane polarizer and a quarter-wavelength retarder.
  • a reflective polarizer may act as a brightness enhancing component by reflecting light of undesired polarization back into the light chamber for recycling.
  • the reflective polarizer only transmits light of the desired polarization and reflects light of undesired polarization.
  • the reflected light may reenter the light chamber, potentially be converted to the desired polarization, and then later pass through the reflective polarizer. In this manner, light from the light source can be used more efficiently.
  • An example of a suitable reflective polarizer is VikuitiTM brand Dual Brightness Enhancing Film (DBEF) available from 3M Company.
  • DBEF Dual Brightness Enhancing Film
  • any one of the first substrate layer (22) and the second substrate layer (24) may be a protective film, which protects the louver layer from damage.
  • any one of the first substrate layer (22) and the second substrate layer (24) may be an optical conditioning film, such as a polarizer.
  • any one of the first substrate layer (22) and the second substrate layer (24) may be a prismatic film or a diffuser film as described below.
  • a prismatic film or a diffuser film has sufficient strength to suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the light control film composite (20).
  • Fig. 3 is a schematic view representing the construction of a conventional LCD device (30) that does not contain a light control film.
  • This LCD device (30) is illustrated as including a display unit comprising a front polarizer (31), a liquid crystal panel (32) and a rear polarizer (33), and a backlight unit (34).
  • the display unit may comprise a front polarizer (31) and a liquid crystal panel (32) only.
  • the illustrated LCD device (30) may further include a diffuser film (38) and a prismatic film (36) disposed between the display unit and backlight unit.
  • the prismatic film (36) may redirect light exiting the light chamber at particular angles relative to the prismatic film (36).
  • the light redirected by the prismatic film (36) can also be recycled, eventually exiting the light chamber at an angle that will pass through the prismatic film.
  • VikuitiTM brand Brightness Enhancing Film (BEF) available from 3M Company, could be used as the prismatic film (36).
  • the prismatic film (36) may comprise VikuitiTM brand Transmissive Right Angle Film
  • TRAF Retrigger
  • 3M Company 3M Company.
  • the TRAF redirects light coming in at high angles to exit at different angles.
  • the diffuser film (38) diffuses incoming light so that the intensity of the light is more spatially uniform. Light coming from one or more point sources may be much more intense at particular locations on an incident face of the diffuser film. Light that exits the diffuser film, however, will be more uniform in intensity across the exit surface of the diffuser film.
  • Fig. 4 illustrates a construction with a conventional light control film (40) in front of a display unit of a conventional LCD device (42).
  • a conventional light control film 40
  • a display unit of a conventional LCD device 402.
  • FIG. 5 schematically illustrates a construction of an LCD device (50) with a light control film composite (52) in front of a liquid crystal panel (32).
  • the light control film composite comprises a louver layer and an absorbing polarizer laminated to the rear surface of the louver layer.
  • An LCD device using the light control film composite (52) of the present invention has the same narrow viewing angle as the conventional LCD device (42) with the conventional light control film (40) in front of the display unit, as shown in Fig. 4, and improved light transmittance by 5% or more. Moreover, the overall thickness of the LCD device is reduced by at least 100 ⁇ m, since one or both window substrate(s) used in the conventional light control film (40) is not necessary.
  • the thickness of the conventional light control film (40) is from about 800 to about 850 ⁇ m and the thickness of the conventional absorbing polarizer is from about 100 to about 150 ⁇ m, while the light control film composite (52) of the present invention can carry out both functions of the conventional light control film (40) and the absorbing polarizer and is from about 350 to 400 ⁇ m in thickness. Accordingly, the thickness can be reduced by at least 500 ⁇ m. Therefore, using the light control film composite (52) of the present invention, the overall thickness of the LCD device (50) can be significantly reduced and the light transmittance improved.
  • Fig. 6 schematically illustrates a construction of an LCD device (60) with a light control film composite (62) of the present invention in the rear of a liquid crystal panel.
  • the light control film composite (62) of the present invention comprises a louver layer, and an absorbing polarizer and a reflective polarizer laminated to the front and rear surfaces of the louver layer, respectively.
  • a light control film composite laminated with a prismatic film or a diffuser film may be used instead of a reflective polarizer.
  • the LCD device containing the light control film composite (62) of the present invention has the same narrow viewing angle as obtained in the conventional LCD device with the conventional light control film shown in Fig. 4 in the rear of the liquid crystal panel and improved light transmittance by 10% or more.
  • the overall thickness of the LCD device containing the light control film composite (62) is reduced by at least 100 ⁇ m compared to the LCD device using the conventional light control film.
  • the thickness can be reduced by at least 600 ⁇ m.
  • the present invention provides a light control film composite that can reduce the overall thickness of the display device, without decreasing the light transmittance of the device and while providing desired light control properties. As a result, the performance of the display does not decrease, unnecessary propagation of light from the liquid crystal panel is prevented, and the privacy of a user is guarded.

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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)
  • Optical Elements Other Than Lenses (AREA)
  • Liquid Crystal (AREA)
  • Polarising Elements (AREA)

Abstract

The invention includes a light control film composite. The light control film includes a louver film layer and a first substrate layer laminated to a front surface of the louver film layer. A second substrate layer is laminated to a rear surface of the louver film layer. At least one of the first and second substrate layers is an optical conditioning film.

Description

IMPROVED LIGBtT CONTROL FILM COMPOSITE AND LCD DEVICE COMPRISING THE SAME
Background
The present invention relates to a light control film comprising louver elements and to an LCD device comprising the same.
In general, an LCD device comprises a liquid crystal display panel (also referred to as a "liquid crystal panel") and a light source, i.e. a backlight, which illuminates the liquid crystal panel from the back surface (i.e. the surface opposite of the display surface).
The typical LCD device also has a pair of first and second polarizers placed on either side of the liquid crystal panel. The polarizers are placed so that the polarization axes of the first polarizer and of the second polarizer (first and second polarization axes, respectively) form a certain angle, for example, a right angle. An example of the backlight is an edge-light type backlight, which comprises a light-guide plate and a light source that supplies light to the light-guide plate from the edge face of the plate. Instead of an edge- light type backlight, the backlight can be a direct-lit type backlight, wherein one or more light sources are placed behind the back surface of the liquid crystal panel within the output area of the display.
However, in the case of illumination by the above backlights, since the light beam is directly transmitted through the liquid crystal panel toward a viewer of the display and the display can be seen by a person standing at an angle apart from the viewer, guarding the privacy of the display is difficult, e.g., with an automated teller machine (ATM), the user's PIN number may be viewable by another person. Furthermore, when the LCD device is an automobile-loaded equipment, such as a car navigation system, the reflection from the panel of the LCD device on the windshield may interfere with the vision of the driver. .
To solve these problems, the display panel can be equipped with a privacy filter that prevents the unnecessary propagation of light emitted by the liquid crystal panel in directions away from the viewing axis. One such privacy filter is a louver film having a plurality of minute louvers (or louver-form elements) inside. The louver film can be attached to the display screen to guard privacy and prevent unwanted reflections on vehicle windows. The plurality of minute louvers built into the louver film can control the propagation directions of the light beams that are transmitted through the louver film and set a specific exiting angle range (direction control effect). Thus, the emission of light beams that are transmitted through the liquid crystal panel in off-axis directions can be effectively prevented. Such a louver film is also a light control film.
The construction, manufacturing and application of louver films are disclosed in some prior publications.
U.S. Patent No. RE 27,617 (Olsen) discloses a method for producing a louver film by skiving a billet consisting of alternating plastic layers having a relatively low optical density (transparent) and a relatively high optical density (colored). When the billet is skived, the colored layers provide louver-form elements, which collimate the light beam. These elements can extend in the direction perpendicular to the surface of the louver film.
U.S. Patent No. 3,707,416 (Stevens) discloses a method for slanting the louver- form elements, which collimate the light beam, relative to the surface of the louver film. U.S. Patent No. 3,919,559 (Stevens) discloses a method for gradually changing the slant angles of the louver elements.
The method for producing the louver layer is disclosed in the above prior art. A layer containing the light-shielding material is fixed to one main surface of a polymer film used as the light-transmitting part to form the louver-form elements, resulting in a laminate film consisting of the polymer film and the light-shielding material layer. A plurality of such laminate films are prepared and laminated to form a precursor louver film, in which the polymer film and the light-shielding material layers are alternately arranged and fixed to each other. The precursor louver film is skived at a desired thickness along the direction (lamination direction) perpendicular to the main surface (laminated plane) to obtain the louver layer.
Further, U.S. Patent Application No. 2004/130788 (Minami) discloses an optical filter comprising a louver film and an adhesive layer, which is used to adhere the louver film to a surface. The louver film generally has a louver layer comprising light- transmitting parts and minute louver elements, which shield the light inside, and a backside and surface side substrate, which are fixed to the louver layer. A conventional light control film containing louver elements is shown in Fig. 1. The two window substrates fixed to the louver layer preferably are made thick enough to suppress warping or curling of the louver layer and the resulting louver film which comprises it. These window substrates also protect the louver layer from damage. However, using such a louver film in a conventional LCD device can undesirably increase the overall thickness and decrease the light transmittance of the LCD device.
Summary
The invention includes a light control film composite. The light control film includes a louver film layer and a first substrate layer laminated to a front surface of the louver film layer. A second substrate layer is laminated to a rear surface of the louver film layer. At least one of the first and second substrate layers is an optical conditioning film.
Brief Description of the Drawings
FIG. 1 is a schematic view of a conventional light control film comprising louver elements.
FIG. 2 is a schematic view representing one embodiment of the light control film composite according to the present invention.
FIG. 3 is a schematic view representing the construction of an LCD device without a light control film. FIG. 4 is a schematic view representing the construction of an LCD device with a conventional light control film.
FIG. 5 is a schematic view representing the construction of an LCD device with the light control film composite according to the present invention in front of the liquid crystal panel. FIG. 6 is a schematic view representing the construction of an LCD device with the light control film composite according to the present invention in the rear of the liquid crystal panel.
In the figures, like reference numerals designate like elements.
Detailed Description
As described above, since a conventional light control film comprising a louver layer essentially contains window substrates to suppress the warp or curl of the louver layer, when the louver film is used in an LCD device, the overall thickness of the LCD device is increased and the light transmittance of the LCD device is inevitably decreased.
Therefore, what is necessary is a light control film that does not adversely affect the overall thickness of the display device nor decrease the light transmittance, but can sufficiently provide the required light control properties.
Fig. 1 schematically represents a conventional light control film (or louver film) comprising louver elements. The film comprises a louver layer containing louver elements and window substrates fixed to both surfaces of the louver layer by adhesive layers. The louver layer (12) has minute louvers (or louver-form elements) (15) inside the film. In general, the louver layer (12) comprises light-transmitting parts (17) and minute louver elements (15), which shield light.
Preferably, the width of the light-transmitting part (17) is larger than the width of the louver element (the dimension of the louver element in the direction parallel to the surface of the louver layer and perpendicular to the lengthwise direction of the louver element), so that the light transmittance of the light control film (10) as a whole does not significantly decrease. The width of the light-transmitting part is preferably from 50 to 500 μm, more preferably from 70 to 200 μm. The width of the louver element may range from 1 to 100 μm, preferably from 10 to 50 μm. The angle (13) of the louver element, an angle between the surface of the louver layer and the plane of the louver element, is usually from 40 to 90 degrees. When the louver element lies at a right angle with the surface of the louver layer, the angle (13) of the louver element is 90 degrees.
The thickness of the louver layer (12) can be suitably determined according to the application of the light control film (10). As the thickness of the louver layer (12) decreases, the control of the propagation direction of light tends to decrease. However, since increased thickness is undesirable, the desired control and thickness should be balanced in view of the application. As only an exemplary consideration, the thickness of the louver layer (12) is preferably from 10 to 1,000 μm, and more preferably from 40 to 500 μm. The light-transmitting parts (17) of the louver layer (12) are preferably made of a polymer having a high transparency. For example, a thermoplastic resin, a thermosetting resin, or a resin curable with an actinic ray such as UV ray may be used. Examples of such resins include cellulose resins (e.g. cellulose acetate butyrate and triacetylcellulose), polyolefin resins (e.g. polyethylene and polypropylene), polyester resins (e.g. polyethylene terephthalate), polystyrene, polyurethane, polyvinyl chloride, acrylic resins, and polycarbonate resins.
The louver elements (15) may be formed from a light-shielding material, which can absorb or reflect light. Examples of such materials include (1) dark pigments or dark dyes, such as black or gray pigments or dyes, (2) metal, such as aluminum, silver, etc., (3) dark metal oxides, and (4) the above-described polymers containing dark pigments or dyes. Other films can be fixed to the louver film by using the adhesive layer (16). The adhesive layer (16) may be formed of a conventional adhesive, such as a pressure-sensitive adhesive, a heat-sensitive adhesive, or a curable adhesive. The thickness of each adhesive layer is usually from 5 to 50 μm.
The two window substrates (14) fixed to the louver layer (12) preferably suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the louver film (10) comprising the louver layer (12), and the surface side substrate also functions as a protective layer to protect the louver layer (12) from damage.
Using a louver film (10) in a conventional LCD device increases the overall thickness of the LCD device and inevitably decreases the light transmittance of the LCD device.
In order to solve such problems, the present invention provides a light control film composite comprising a louver film, a first substrate layer laminated to a rear surface of the louver film layer and a second substrate layer laminated to a rear surface of the louver film layer, at least one of said first and second substrate layers being an optical conditioning film. The optical conditioning film of the present invention may be an absorbing polarizer, a reflective polarizer, a prismatic film or a diffuser film.
Fig. 2 schematically represents a light control film composite (20) according to the present invention, both of a first substrate layer (22) and a second substrate layer (24) being polarizers. In this embodiment, polarizers (22 and 24) are attached to a louver layer (12) through adhesive layers (16) and can also function to suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the light control film composite (20). The polarizer films (22 and 24) can be each independently an absorbing polarizer or a reflective polarizer.
The absorbing polarizer may be a plane polarizer or a circular polarizer. A plane polarizer absorbs light of one polarization orientation more strongly than the light of the orthogonal polarization orientation. Examples of plane polarizers include a dichromic polarizer such as an H-type (iodine) polarizer and a dyestuff polarizer, an intrinsic polarizer such as a K-type polarizer and an improved K-type polarizer (referred to as a KE polarizer as manufactured by 3M Company, Norwood, Mass.), and a thinly cladded or encapsulated polarizer. A circular polarizer blocks one of left-handed (L) or right-handed (R) circularly polarized light and transmits light of the other polarization state, and may be constructed of a plane polarizer and a quarter-wavelength retarder.
A reflective polarizer may act as a brightness enhancing component by reflecting light of undesired polarization back into the light chamber for recycling. The reflective polarizer only transmits light of the desired polarization and reflects light of undesired polarization. The reflected light may reenter the light chamber, potentially be converted to the desired polarization, and then later pass through the reflective polarizer. In this manner, light from the light source can be used more efficiently. An example of a suitable reflective polarizer is Vikuiti™ brand Dual Brightness Enhancing Film (DBEF) available from 3M Company.
In another embodiment, any one of the first substrate layer (22) and the second substrate layer (24) may be a protective film, which protects the louver layer from damage.
In yet another embodiment, any one of the first substrate layer (22) and the second substrate layer (24) may be an optical conditioning film, such as a polarizer. In another embodiment, any one of the first substrate layer (22) and the second substrate layer (24) may be a prismatic film or a diffuser film as described below. A prismatic film or a diffuser film has sufficient strength to suppress the warp or curl of the louver layer (12) and in turn the warp or curl of the light control film composite (20).
Fig. 3 is a schematic view representing the construction of a conventional LCD device (30) that does not contain a light control film. This LCD device (30) is illustrated as including a display unit comprising a front polarizer (31), a liquid crystal panel (32) and a rear polarizer (33), and a backlight unit (34). The display unit may comprise a front polarizer (31) and a liquid crystal panel (32) only. The illustrated LCD device (30) may further include a diffuser film (38) and a prismatic film (36) disposed between the display unit and backlight unit. The prismatic film (36) may redirect light exiting the light chamber at particular angles relative to the prismatic film (36). The light redirected by the prismatic film (36) can also be recycled, eventually exiting the light chamber at an angle that will pass through the prismatic film. For example, Vikuiti™ brand Brightness Enhancing Film (BEF), available from 3M Company, could be used as the prismatic film (36). Alternatively, the prismatic film (36) may comprise Vikuiti™ brand Transmissive Right Angle Film
(TRAF)3 also available from 3M Company. The TRAF redirects light coming in at high angles to exit at different angles.
The diffuser film (38) diffuses incoming light so that the intensity of the light is more spatially uniform. Light coming from one or more point sources may be much more intense at particular locations on an incident face of the diffuser film. Light that exits the diffuser film, however, will be more uniform in intensity across the exit surface of the diffuser film.
Fig. 4 illustrates a construction with a conventional light control film (40) in front of a display unit of a conventional LCD device (42). In an aspect of viewing angles that a user can see through the LCD device (42) and the light control film (42) as shown in Fig.
3, narrower viewing angles can be achieved compared to the case that the light control film (40) is not used. However, due to the use of the light control film, the overall thickness of the LCD device is increased while the light transmittance of the LCD device is significantly decreased. Fig. 5 schematically illustrates a construction of an LCD device (50) with a light control film composite (52) in front of a liquid crystal panel (32). The light control film composite comprises a louver layer and an absorbing polarizer laminated to the rear surface of the louver layer. When the light control film composite (52) is used, a separate polarizer in front of the liquid crystal panel is unnecessary. An LCD device using the light control film composite (52) of the present invention has the same narrow viewing angle as the conventional LCD device (42) with the conventional light control film (40) in front of the display unit, as shown in Fig. 4, and improved light transmittance by 5% or more. Moreover, the overall thickness of the LCD device is reduced by at least 100 μm, since one or both window substrate(s) used in the conventional light control film (40) is not necessary. Specifically, the thickness of the conventional light control film (40) is from about 800 to about 850 μm and the thickness of the conventional absorbing polarizer is from about 100 to about 150 μm, while the light control film composite (52) of the present invention can carry out both functions of the conventional light control film (40) and the absorbing polarizer and is from about 350 to 400 μm in thickness. Accordingly, the thickness can be reduced by at least 500 μm. Therefore, using the light control film composite (52) of the present invention, the overall thickness of the LCD device (50) can be significantly reduced and the light transmittance improved.
Fig. 6 schematically illustrates a construction of an LCD device (60) with a light control film composite (62) of the present invention in the rear of a liquid crystal panel. The light control film composite (62) of the present invention comprises a louver layer, and an absorbing polarizer and a reflective polarizer laminated to the front and rear surfaces of the louver layer, respectively. As needed, a light control film composite laminated with a prismatic film or a diffuser film may be used instead of a reflective polarizer. The LCD device containing the light control film composite (62) of the present invention has the same narrow viewing angle as obtained in the conventional LCD device with the conventional light control film shown in Fig. 4 in the rear of the liquid crystal panel and improved light transmittance by 10% or more. Moreover, the overall thickness of the LCD device containing the light control film composite (62) is reduced by at least 100 μm compared to the LCD device using the conventional light control film.
Specifically, if the conventional absorbing polarizer, light control film (4) and reflective polarizer are used, their overall thickness is from about 1100 to about 1200 μm, while the light control film composite (62) of the present invention comprising the absorbing and reflective polarizer is only from about 450 to 550 μm in thickness. Accordingly, the thickness can be reduced by at least 600 μm.
While the invention has been described with respect to illustrative examples above, various modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims.
Effect of the Invention
The present invention provides a light control film composite that can reduce the overall thickness of the display device, without decreasing the light transmittance of the device and while providing desired light control properties. As a result, the performance of the display does not decrease, unnecessary propagation of light from the liquid crystal panel is prevented, and the privacy of a user is guarded.

Claims

What is claimed is:
1. A light control film composite comprising: a louver film layer; a first substrate layer laminated to a front surface of the louver film layer; and a second substrate layer laminated to a rear surface of the louver film layer, wherein at least one of the first and second substrate layers is an optical conditioning film.
2. The light control film composite as recited in claim 1, wherein the optical conditioning film is an absorbing polarizer, reflective polarizer, prismatic film, or diffuser film.
3. The light control film composite as recited in claim 1, wherein the first substrate layer is an absorbing polarizer.
4. The light control film composite as recited in claim 3, wherein the second substrate layer is one of a reflective polarizer, prismatic film, or diffuser film.
5. The light control film composite as recited in claim 1, wherein the second substrate layer is an absorbing polarizer.
6. An LCD device comprising the light control film composite as recited in claims 1-5.
7. The LCD device as recited in claim 6, wherein the light control film composite is placed in front of the liquid crystal panel.
8. The LCD device as recited in claim 6, wherein the light control film composite is placed in the rear of the liquid crystal panel.
PCT/US2007/003289 2006-03-03 2007-02-07 Improved light control film composite and lcd device comprising the same WO2007100458A1 (en)

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