JP4935992B2 - Optical member and backlight unit and display device using the same - Google Patents

Description

  The present invention relates to an improvement in an optical member used for illumination light path control in a direct backlight unit for a display mainly using a liquid crystal display element.

  In recent years, liquid crystal display devices (LCDs) using liquid crystal panels have been used in image display means for notebook personal computers and personal computer displays in the OA field, information terminal equipment, etc., as well as image display means for information appliances such as large-screen TVs, Has been used in various fields as an image display means for mobile phones and personal digital assistants (PDAs).

In a display represented by a liquid crystal display device (LCD), a type having a built-in light source necessary for recognizing provided information is remarkably widespread.
Such a liquid crystal display device is a transmissive type, and a light source is provided on the back side of the liquid crystal panel, and a surface light source device that irradiates the liquid crystal panel by converting light from the light source into surface light emission, a so-called backlight It has been adopted.

  The backlight system is roughly divided into a cold cathode fluorescent tube (CCFT) and other light sources attached along the side edge of a flat light guide plate made of acrylic resin with excellent light transmission. There are a light guide plate light guide method (edge light method) that multi-reflects light from the light guide plate and a direct type method in which a light source is arranged on the back surface of the liquid crystal panel without using the light guide plate.

Recently, for small liquid crystal display devices with a screen size of 20 inches or less used for notebook personal computers, personal digital assistants, etc., it has become mainstream to adopt an edge light system that can reduce power consumption and can be easily thinned. In medium to large liquid crystal display devices having a screen size of 20 inches or more, the direct type is the mainstream.
In a battery-powered device such as a laptop computer, the power consumed by the light source occupies a substantial portion of the power consumed by the entire battery-powered device.
Thus, reducing the total power required to provide a given brightness increases battery life, which is particularly desirable for battery powered devices.

  Liquid crystal display devices of 20 inches or more are required to be thinner, have a low viewing angle dependency, have high brightness, and have low power consumption. There is a need to deal with realization.

  In a direct type backlight with multiple cold cathode tubes arranged in parallel, a cold cathode tube (CCFT) or an LED (Light Emitting Diode) as a light source passes through a diffusion plate that diffuses the emitted light, and the emitted light source Since the shape can be directly recognized, a resin plate having a very strong light scattering property is used as the diffusion plate. This diffuser plate usually needs to have a thickness of about 1 mm to 3 mm in order to have a strong diffusivity, and because of the thickness, there is a considerable amount of light absorption, and the amount of light from the light source is reduced, resulting in a liquid crystal display. There is a problem of darkening.

  A brightness enhancement film (BEF), which is a registered trademark of 3M Corporation, is widely used as an optical sheet for solving this problem.

  As shown in FIG. 1, BEF is a film in which unit prisms 2 having a triangular cross section are periodically arranged in one direction on a member 1. The prism 2 has a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects it “on-axis” or “recycle” toward the viewer To do.

  When using the display (when observing), BEF increases on-axis brightness by reducing off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the viewer, and is generally the normal direction (direction F shown in FIG. 1) side with respect to the display screen.

  When the repetitive array structure of the prisms 2 is arranged in only one direction, only the direction change or recycling in the parallel direction is possible. In order to control the luminance of the display light in the horizontal and vertical directions, the prism groups are arranged in parallel. Two sheets are stacked and combined so that the directions are substantially orthogonal to each other.

  The adoption of BEF allows display designers to achieve the desired on-axis brightness while reducing power consumption. As patent documents disclosing that a brightness control member having a repetitive array structure of prisms 2 typified by BEF is adopted for a display, many are known as exemplified in Patent Documents 1 to 3. ing.

  In the optical sheet using the BEF as a luminance control member as described above, the light P from the light source 3 is finally emitted at a controlled angle φ by the refraction action x as shown in FIG. Thus, it is possible to control to increase the intensity of light in the visual direction F of the viewer. However, at the same time, the light component due to the reflection / refractive action y is emitted in the horizontal direction without proceeding to the visual direction F of the viewer, and when the angle is set in the horizontal direction, the brightness is rapidly reduced.

  As a means to solve this problem, the incident light from the incident surface side is emitted from the non-incident surface so that the light from the light source can be made uniform and the diffusion range can be controlled and emitted. A light diffusing layer that scatters light, a light reflecting layer that has one surface fixed to the exit surface of the light scattering layer, and reflects light scattered by the light scattering layer toward the light diffusing layer, and the other surface of the light reflecting layer A lens sheet was invented in which the back surface was fixed to the front surface and a plurality of lenses were arranged on the front surface. A part of the light reflecting layer has a refractive index lower than that of the light diffusing layer and the lens sheet, and is penetrated by a plurality of low refractive index regions provided corresponding to each of the plurality of lenses.

By using this optical sheet, it is possible to maintain a gradual change in luminance distribution at a wide angle in the horizontal direction as shown in FIG.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500

  The optical sheet shows a gradual change in luminance distribution at a wider angle in the horizontal direction than BEF, but when used as a backlight unit of a liquid crystal display, in addition to the optical sheet, a diffusion sheet is used in addition to the optical sheet. Etc. are necessary, and problems remain such as complexity of the process at the time of assembling the display device and inhibition of cost reduction.

  On the other hand, by integrating the optical sheet and the light diffusing plate, it is possible to reduce the number of members of the backlight unit and simplify the manufacturing process of the display device.

At this time, the properties required by the bonding surface of the optical sheet and the properties required by the bonding surface of the light diffusing plate may conflict with each other as the optimum adhesive property for integrating the optical sheet and the light diffusing plate. .
In the present specification, the adhesive refers to a broad concept including an adhesive.

The present invention has been made in view of the above problems, and the present invention provides a backlight unit member in which an optical sheet having a front luminance improving property and a light diffusing plate are integrally formed by adhesion or adhesion. By making the adhesive layer or the pressure-sensitive adhesive layer into a two-layer structure via a transparent support (hereinafter referred to as a transparent film or a carrier), each of the bonding surface of the optical sheet and the bonding surface of the light diffusion sheet It is characterized in that bonding can be performed under optimum conditions.
That is, the invention described in claim 1 is an optical member used for illumination light path control in a display backlight unit, wherein the first optical sheet and the second optical sheet are bonded together by a composite adhesive layer. The first optical sheet includes a lens sheet having a lens portion made of a convex cylindrical lens group or a hemispherical convex lens group on one surface, and a reflective layer provided on a non-lens portion surface of the lens sheet. And the reflection layer is a light reflection portion provided in a region including a non-light-collecting surface by the lens portion, and a light transmission formed as an opening provided in a region other than the light reflection portion and having air. The second optical sheet is joined to the light reflecting portion via the composite adhesive layer, the composite adhesive layer includes a transparent film, and the transparent film A first adhesive layer provided on a surface facing the reflective portion, the transparent film is characterized in that it comprises a second adhesive layer provided on a surface facing the second optical sheet.
The invention described in claim 2 is characterized in that the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer have different physical properties. Item 10. The optical member according to Item 1.
The invention described in claim 3 is characterized in that the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer have the same physical properties. The optical member according to 1.
The invention of claim 4, wherein is an optical member according to claim 1 Symbol placement, wherein the total light transmittance of the transparent film is 84% or more.
In the invention described in claim 5, the difference between the refractive index of the first adhesive layer and the refractive index of the transparent film, and the difference between the refractive index of the second adhesive layer and the refractive index of the transparent film are all 0. The optical member according to any one of claims 1 to 4 , wherein the optical member is .17 or less.
According to a sixth aspect of the present invention, the first optical sheet is a prism sheet in which a prism is formed on one surface, and the non-prism surface of the first optical sheet is formed by the composite adhesive layer. an optical member of claim 1 Symbol mounting, characterized in that it is joined to the optical sheet.
According to a seventh aspect of the present invention, the first optical sheet is a prism sheet in which a prism is formed on one surface, a reflection layer is provided on a non-prism surface of the first optical sheet, and the reflection is performed. The layer is composed of a light reflecting portion in parallel with the extending direction of the prism, and a light transmitting portion provided as an opening provided in an area other than the light reflecting portion, where the air exists. claim 1, 2, 3, wherein the light reflecting portion of the first optical sheet is characterized in that it is joined to the second optical sheet, an optical member according to any one of the 6.
The invention according to claim 8 is characterized in that the transparent film is a polymer film or sheet made of glass or, for example, polycarbonate (PC), acrylic, polyethylene terephthalate (PET) or the like. 7. The optical member according to any one of items 7 to 7 .
Further, an invention according to claim 9, wherein said the back of the image display element defining a display image, and the direct type light source, comprise at least an optical member according to any one of the claims 1 to 8 Display This is a backlight unit.
According to a tenth aspect of the present invention, the surface light source comprising an edge light type light source and a light guide plate and the optical member according to any one of the first to eighth aspects are provided on the back surface of the image display element that defines a display image. A display backlight unit comprising at least the display backlight unit.
According to the eleventh aspect of the present invention, there is provided an illumination light source disposed on the side opposite to the observer with respect to a display element in which a display pattern is defined in accordance with transmission / non-transmission or transparency / scattering in pixel units. 11. The back according to claim 9 , wherein the display device is configured to irradiate illumination light, pass through the display element, generate display light, and emit the light toward an observer, and is disposed facing the display element. A light unit is provided .

  In the optical member for the backlight unit of the liquid crystal display according to the present invention, the optical sheet having the front luminance improvement property and the light diffusion sheet are bonded through an adhesive layer or an adhesive layer having two layers sandwiched between transparent films. The optical sheet and the light diffusion plate can be integrated with the optimum adhesion strength required.

  When using an optical sheet with a striped light reflection layer mainly composed of a white pigment in order to maintain a gradual change in luminance distribution at a wider angle in the horizontal direction, the optical sheet side and light diffusion through a transparent film By making the bonding environment different from the plate side, it is possible to ensure the adhesion between the optical sheet and the light diffusing plate while maintaining the air layer essential for the optical sheet to function effectively. Become.

  By using a transparent film whose total light transmittance, refractive index, and the like fall within a predetermined range as a carrier, it has the same performance as when integrated through a single adhesive layer or adhesive layer.

  By realizing an optical sheet-light diffusion plate integrated backlight member that does not require an auxiliary member, advantages such as reduction in the manufacturing process of the liquid crystal display device itself, reduction in thickness, and cost reduction can be expected.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 4 is an explanatory view showing an embodiment in which the present invention is applied to a liquid crystal display device including a direct type backlight unit 40, and the scale of each part does not match the actual scale.
A backlight unit 40 is provided facing the liquid crystal panel 42.
The backlight unit 40 is configured to include a light source 21 including a reflection plate 27 and a cold cathode tube 23, and a plurality of optical sheets.
Examples of the optical sheet include a prism sheet or a lens sheet formed of a thermoplastic or UV curable resin on a substrate made of PC, acrylic, PET, or the like.
In the present embodiment, the plurality of optical sheets are disposed on the diffusion plate 4 disposed immediately above the light source, the first optical sheet 13 disposed on the diffusion plate 4, and the first optical sheet 13. This is the polarizing plate 49 to be used.

In the present embodiment, the first optical sheet 13 and the diffusion plate 4 are joined by the composite adhesive layer 14. In the present embodiment, the diffusion plate 4 corresponds to the second optical sheet in the claims.
As a base material to be bonded to the optical sheet, a light diffusing plate or light made of polycarbonate, cycloolefin polymer, acrylic, polystyrene, or a mixture of these materials in an arbitrary ratio well known in the field. Examples include a fine diffusion plate and a transparent plate.
That is, in the optical member according to this embodiment, the first optical sheet 13 and the diffusion plate 4 are integrated with each other through a composite adhesive layer 14 made of the adhesives 5 and 7 and the transparent film 6 well known in the art. It is a structured.

The first optical sheet 13 includes a sheet-like or thin plate-like transparent base material 11, a lens unit 12, and a reflective layer 8.
The lens unit 12 is provided on one surface in the thickness direction of the transparent base material 11 and is configured by a convex cylindrical lens group or a hemispherical convex lens group. The lens unit 12 guides the light traveling in the optical member 13 to the liquid crystal panel 42. In the present embodiment, the lens unit 12 is configured by providing cylindrical lenses (unit optical elements) 12A in parallel.

The reflective layer 8 is provided on the other surface in the thickness direction of the transparent substrate 11 via the photosensitive material 10.
The reflective layer 8 is provided in a region other than the light reflecting portion 8A and in the region other than the light reflecting portion 8A, in other words, in the vicinity of the focal plane of the lens portion 12. The light transmission portion (opening portion) 8B is formed as a stripe pattern.
The light reflecting portion 8A is formed by printing an ink in which titanium dioxide (TiO ₂ ) powder, which is a white pigment, is dispersed in a transparent mixed solution of a resin and a solvent in a predetermined pattern, for example, a dot pattern. The reflective layer 8 including the light reflecting portion 8A can also be formed by transfer (UV bonding or thermocompression bonding). When UV bonding is performed, the photosensitive material 10 is bonded to the non-lens surface of the lens sheet. Then, by performing UV irradiation from the lens surface side, a pattern for adhering the white foil made of the white ink is formed.
More specifically, the optical sheet according to the present embodiment includes the lens sheet 13 and the light diffusing plate 4 laminated and integrated through the composite adhesive layer 14.
The lens sheet 13 has a lens portion 12 formed on one side (upper side in the drawing) of the lens base material 11 (transparent base material 11), and the lens portion on the other surface (on the opposite lens side) of the lens base material 11. The light reflecting layer 8 is formed in a pattern shape in the non-light condensing part corresponding to the 12 light condensing characteristics, and becomes a non-opening part.
The lens sheet 13 may have a monolithic configuration such as melt extrusion molding or press molding, or a configuration in which the lens base 11 and the lens portion 12 which are separate members are integrated. In the latter case, the lens portion 12 made of a cured product of a radiation curable resin material is polymerized and bonded to the surface of the thermoplastic resin substrate 11 (so-called molded product by the 2P method). Effective above.
The adhesive layer 14 has a configuration in which an adhesive is formed on the upper and lower sides of the carrier 6 (transparent film 6) which is a core agent in FIG.
In forming the light reflecting layer 8, generally, various methods such as printing (coating), transfer, and photolithography are appropriately selected. When the parallel pitch of the unit lenses of the lens sheet is fine, the unit is used. Since alignment accuracy for forming a stripe shape having an opening corresponding to each lens is required, as one method of the photolithography method, the reflective layer (opening) It is effective to adopt a so-called “self-alignment method” that defines the formation part of the part).
As an example of the self-alignment method, a photopolymer layer 10 having a characteristic that adhesiveness disappears due to light exposure is formed on the entire surface on the anti-lens portion side flat surface, and each unit lens is collected by exposure from the lens portion side. Of the condensing part (the part where the photopolymer adhesiveness disappears) / non-condensing part (the part where the photopolymer adhesiveness remains) defined according to the light action, only the part corresponding to the non-condensing part A technique for transferring and forming the white transfer layer 8 is effective.

In the present embodiment, only the light that has passed through the light transmission portion 8B out of the light emitted from the diffusion plate 4 enters the cylindrical lens 12A, and is emitted after being condensed in a certain direction by the cylindrical lens 12A. .
Then, the light enters the polarizing plate 49 and only light having a predetermined polarization component is guided to the liquid crystal panel 42.
On the other hand, the light that could not pass through the light transmitting portion 8B is reflected by the light reflecting portion 8A, returned to the diffusion plate 4 side, and guided to the reflecting plate 27. Then, after being incident on the diffusion plate 4 again by being reflected by the reflection plate 27 and being diffused on the diffusion plate 4, the incident light is narrowed, and then the light passes through the light transmitting portion 8 </ b> B to form a cylindrical lens. The light enters the lens 12A and is emitted within a predetermined angle by the cylindrical lens 12A.

The composite adhesive layer 14 includes a transparent film 6, a first adhesive layer 5 provided on the surface where the transparent film 6 faces the first optical sheet 13, and a first film provided on the surface where the transparent film 6 faces the diffusion plate 4. 2 adhesive layers 7.
The transparent film 6 is made of, for example, glass having a total light transmittance (Tt) of 84% or more and a refractive index difference (Δn) of 0.17 or less, such as PC, acrylic, PET, or the like. A polymer film or sheet is used.
The transparent film 6 having a thickness of 50 μm can be used.

The adhesive constituting the first adhesive layer 5 and the adhesive constituting the second adhesive layer 7 may have different physical properties or may have the same physical properties. Yes, and appropriately selected according to the first optical sheet 13 and the second optical sheet 4 to be joined.
(Example)

As an example of the structure according to the present invention, the first optical sheet 13, the adhesive constituting the first adhesive layer 5, the transparent film 6, the adhesive constituting the second adhesive layer 7, the second optical sheet (base material) ) 4 combinations are shown in FIG.
FIG. 6 shows the measurement result of Example (1) as a representative of the luminance distribution of the optical member according to the present embodiment.

  From the comparison between FIG. 3 and FIG. 6, when the same light diffusing plate and optical sheet are used, the light diffusing plate-optical sheet integrated structure is a conventional structure in which a light diffusing plate, an optical sheet, and an auxiliary optical sheet are laminated. It was shown to have the same performance as that of the structure.

According to the present embodiment, when the first optical sheet 13 and the second optical sheet (diffusion plate 4) are bonded together, the composite adhesive layer 14 is the transparent film 6, and the transparent film 6 is the first optical sheet. 13 is composed of a first adhesive layer 5 provided on the surface facing 13 and a second adhesive layer 7 provided on the surface where the transparent film 6 faces the second optical sheet (diffusion plate 4). It becomes possible to perform bonding on each of the first and second optical sheets 13 and 4 under optimum conditions, and to exhibit optical performance similar to that of a conventional structure that is simply laminated.
For this reason, the number of constituent members of the backlight unit is reduced, the complexity of the assembly process of the display device is eliminated, and the cost of the display device is reduced.

Schematic diagram showing an example of BEF configuration Diagram for explaining the optical action of BEF Luminance distribution (horizontal direction) of RBEF and optical sheet according to the present invention Sectional drawing which showed the structural example of the form which concerns on implementation of this invention Configuration example of embodiment according to the present invention Luminance distribution (horizontal direction) of an optical member (Example 1) having a structure according to an embodiment of the present invention

Explanation of symbols

  F ... Visual direction, 1 ... Member, 2 ... Prism, 3 ... Light source, 4 ... Light diffusion plate, 5 ... First adhesive layer, 7 ... Second adhesive layer, 6 ... Transparent film, 8 ... Reflective layer, 8A ... Light Reflecting portion, 8B ... light transmitting portion, 10 ... sensitive material, 11 ... transparent substrate, 12 ... lens portion, 13 ... first optical sheet, 14 ... composite adhesive layer.

Claims (11)

In an optical member used for illumination light path control in a backlight unit for display,
The optical member is configured by bonding a first optical sheet and a second optical sheet with a composite adhesive layer,
The first optical sheet is
A lens sheet having a lens portion consisting of a convex cylindrical lens group or a hemispherical convex lens group on one surface;
A reflective layer provided on a non-lens portion surface of the lens sheet,
The reflective layer is composed of a light reflecting portion provided in a region including a non-light-collecting surface by the lens portion, and a light transmitting portion formed as an opening provided in a region other than the light reflecting portion. And
The second optical sheet is bonded to the light reflecting portion via the composite adhesive layer,
The composite adhesive layer includes a transparent film, a first adhesive layer provided on the surface where the transparent film faces the light reflecting portion, and a second provided on the surface where the transparent film faces the second optical sheet. An adhesive layer,
An optical member. The adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer have different physical properties from each other.
The optical member according to claim 1. The adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer have the same physical properties.
The optical member according to claim 1. The total light transmittance of the transparent film is 84% or more,
Claim 1 Symbol placement of the optical member, characterized in that. The difference between the refractive index of the first adhesive layer and the refractive index of the transparent film, and the difference between the refractive index of the second adhesive layer and the refractive index of the transparent film are both 0.17 or less.
The optical member according to any one of claims 1 to 4 , wherein the optical member is any one of the above. The first optical sheet is a prism sheet in which a prism is formed on one surface,
The non-prism surface of the first optical sheet is bonded to the second optical sheet by the composite adhesive layer.
Claim 1 Symbol placement of the optical member, characterized in that. The first optical sheet is a prism sheet in which a prism is formed on one surface,
A reflective layer is provided on the non-prism surface of the first optical sheet;
The reflective layer includes a light reflecting portion in parallel with the extending direction of the prism, and a light transmitting portion formed as an opening that is provided in a region other than the light reflecting portion and has air,
The light reflecting portion of the first optical sheet is bonded to the second optical sheet by the composite adhesive layer.
The optical member according to any one of claims 1, 2, 3, and 6. The transparent film is a polymer film or sheet made of glass or, for example, polycarbonate (PC), acrylic, polyethylene terephthalate (PET), etc.,
The optical member according to claim 1, wherein the optical member is any one of claims 1 to 7 . On the back of the image display element that defines the display image,
A direct light source, and at least the optical member according to any one of claims 1 to 8 ,
A backlight unit for displays. On the back of the image display element that defines the display image,
An edge light type light source and a surface light source comprising a light guide plate; and at least the optical member according to any one of claims 1 to 8 ,
A backlight unit for displays. Illumination light is emitted from an illumination light source disposed on the opposite side of the observer to a display element whose display pattern is defined according to transmission / non-transmission or transparency / scattering state in pixel units, In a display device configured to pass through to generate display light and emit it to the viewer side,
The backlight unit according to claim 9 or 10, which is disposed facing the display element.
A display device characterized by that.

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