JP2009086099A - Optical sheet, backlight unit for display, liquid crystal display, and method of manufacturing optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit various optical characteristics without modifying the shape of an optical element. <P>SOLUTION: The optical sheet includes a light reflecting layer provided with a plurality of light reflecting patterns 18 regulating an incident range of light for each unit lens on the other surface of a lenticular lens sheet on whose one surface a plurality of cylindrical lenses are arranged. The width of the light reflecting patterns 18 is expressed as xi, and an average value in which n (n is a plural number) spots of the widths xi of the plurality of light reflecting patterns 18 in a prescribed range are measured is expressed as μ. Then, standard deviation σ of the widths xi expressed by an expression (1) are adjusted so as to satisfy a condition of 2.0<σ<7.0 to modify the optical characteristics. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical sheet used for illumination light path control, for example, and a display backlight unit using the optical sheet and a liquid crystal display for a liquid crystal display element.

A display typified by a liquid crystal display (LCD) incorporates a light source (backlight) necessary for recognizing information such as an image to be provided. The power consumed by this light source occupies a considerable portion of the power consumed by the entire liquid crystal display device. However, in recent years when it is strongly desired to reduce the total power, it is required to improve the utilization efficiency of the light source.
In order to improve the light source utilization efficiency, there are techniques for increasing the light emission conversion efficiency and for enhancing the light utilization efficiency of the emitted light in combination with means for dimming according to the brightness of the surroundings.

As a means for enhancing the light utilization efficiency, an optical film having a brightness enhancement film (BEF (Brightness Enhancement Film: registered trademark of US 3M)) is widely used between a light source or a light guide plate and a liquid crystal panel. .
BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a transparent substrate. This prism is formed in a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” to the viewer or “recycle” " When the display is used (observed), the on-axis brightness can be increased by reducing the off-axis brightness by BEF for the light emitted from the light source.
Note that “on the axis” is a direction that coincides with the visual direction of the viewer, and is generally a normal direction to the display screen.

In BEF, when a repetitive array structure of prisms is arranged in only one direction, only redirection or recycling in the arrangement direction is possible. Therefore, in order to control the luminance of the display light in the horizontal direction on the horizontal plane and in the vertical direction perpendicular thereto, two BEF sheets are used in combination so that the arrangement directions of the prism groups are substantially orthogonal to each other. By adopting BEF, it is possible to achieve a desired on-axis brightness while reducing power consumption.
Many patent documents disclose that a brightness control member having a repetitive array structure of prisms represented by BEF is used for a display such as a liquid crystal display device (see, for example, Patent Documents 1 to 3).

For example, in an edge light type liquid crystal display device provided with an optical sheet using the BEF as a luminance control member, light from the light source is emitted from the inclined surface of the prism, and its refraction action causes the axial direction to be the center of the light. It is possible to control to increase the intensity of light in the visual direction of the viewer.
However, at the same time, the light component reflected from one inclined surface of the prism and refracted by the other inclined surface is unnecessarily emitted laterally without proceeding in the viewer's visual direction. .

In FIG. 8, when the vertical axis represents the light intensity and the horizontal axis represents the viewing angle of the observer centered on the on-axis, the liquid crystal display device or backlight unit provided with the BEF optical sheet described above is used. As shown by the broken line B, the light intensity distribution is highest with respect to the visual direction F (on-axis direction) in the figure although the light intensity at the angle 0 ° of the viewer's visual direction F (corresponding to the on-axis direction) is highest. As the emission angle in the horizontal direction gradually changes in both side (±) directions, the light intensity gradually decreases. At an emission angle near ± 90 ° that coincides with the horizontal axis, sidelobe light deviating from the viewing direction is shown as a small light intensity peak. Since the sidelobe light deviates from the observer's field of view, there is a problem that the amount of light emitted from the lateral direction of the prism is increased.
In general, a usage pattern in which two prism sheets are used in combination so that the other prism is substantially orthogonal to the direction in which one prism is arranged in parallel is widely used. The broken line B in the graph shown in FIG. 8 represents the light intensity distribution when only one BEF optical sheet (prism sheet) is used. Therefore, the luminance distribution having the light intensity peak of the side lobe light indicated by the broken line B in FIG. 8 is not desirable, and there is no light intensity peak due to the side lobe light in the vicinity of ± 90 ° indicated by the solid line A as a substantially normal distribution curve. A smooth luminance distribution is desirable.
On the other hand, when only the on-axis luminance increases excessively, the width of the mountain in the graph becomes extremely narrow, and the viewing area is extremely limited. Therefore, in order to increase the width of the peaks in the graph appropriately, it is necessary to newly use a light diffusion film which is a separate member from the prism sheet. In this case, a phenomenon occurs in which the number of optical members increases and luminance decreases.

In view of the above circumstances, the present inventors have proposed the optical sheet disclosed in Patent Document 4 as an alternative product of a prism sheet represented by BEF.
The optical sheet described in Patent Document 4 is provided with a lenticular lens sheet having a lens portion made up of unit lens groups formed substantially on the light incident surface side of the illumination light source and formed on the light exit surface side. This lens sheet is used in a display backlight unit.
This display unit employs, for example, an edge light system, and has a surface light source that irradiates light emitted from an edge light source onto a liquid crystal display element that defines a liquid crystal display image by a light guide plate. The lens sheet disposed in front of the light emitting direction from the light guide plate is in close contact with a light reflecting portion in which an opening for transmitting light and a light reflecting pattern for reflecting light are arranged on the incident surface.
The light that could not pass through the opening of the lens sheet is reflected by the light reflection pattern of the light reflection layer and returned to the light guide plate side. Then, after repeating reflection at the interface with the light guide plate or within the light guide plate, any of the light enters the lens sheet through the opening, and is emitted to the image display element with the emission angle controlled within a predetermined angle.
In the backlight unit using such a lenticular lens sheet, by setting the size and position of the opening of the lens sheet, the ratio of the light emitted from the lens sheet in the front direction while improving the light utilization efficiency Is controlled to increase.

By the way, in a display having a relatively large size screen such as a liquid crystal TV or a personal computer monitor instead of a display having a relatively small size screen such as a mobile phone or a mobile terminal, the luminance distribution in the screen is as uniform as possible. In order to achieve this, it is preferable to adopt a direct type backlight unit in which a light source is housed in a lamp house behind the screen, rather than an edge light type backlight unit.
Such a direct type backlight unit has a configuration in which optical elements are stacked in the axial (vertical) direction. That is, a diffusion plate or a diffusion film, a prism sheet or a lens sheet, a diffusion film or a DBEF are arranged in the stacking direction on a lamp house in which a light source is stored. The light incident surface of the prism sheet or lens sheet is provided with a light reflection layer in which openings and light reflection patterns are alternately arranged.
These backlight units are designed to convert uneven light from the light source into diffused light with a strong diffusion function such as a diffusion plate, and then obtain a desired luminance distribution with a prism sheet or lens sheet. Yes.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2000-284268 A

By the way, in the above-described edge light type or direct type backlight unit, the lens sheet having a high condensing function uses the refraction function of the unit lens, and has an effect of increasing the on-axis luminance by reducing the off-axis luminance. . These lens sheets constitute, for example, lenticular lens sheets, and are usually designed in a shape that exhibits desired optical characteristics and are mass-produced using a mold.
In this case, a lenticular lens sheet having a lens portion having a shape corresponding to the required optical characteristics is manufactured by a mold, but a lenticular lens sheet having a different shape is manufactured according to a slight difference in optical characteristics. However, there are disadvantages in that a plurality of types of molds corresponding to the shape are required, and it takes time and effort to manufacture.

  In view of such circumstances, the present invention provides an optical sheet that can exhibit various optical characteristics without changing the shape of the optical element, a method for manufacturing the same, a backlight unit for a display including the optical sheet, and a liquid crystal display. The purpose is to provide.

で表される幅ｘｉの標準偏差σの値が、下記（２）式
２．０＜σ＜７．０ （２）
なる条件を満たすことを特徴とする。
本発明によれば、光反射層における光反射パターンの幅ｘｉの標準偏差σを調整することで、光反射パターンで反射される光と光学シートを透過する光を調整できるため、光学素子や光学素子シートの形状を変えることなく、出射光全体の分布を制御することができる。特に光反射パターンの幅ｘｉの標準偏差σを（２）式で示す範囲内に収めることで、光学シートを透過する光による画像等にムラを視認することなく、輝度分布や半値角を調整することができる。 An optical sheet according to the present invention regulates an incident range of light with respect to each of a plurality of optical elements on the other surface of the optical element sheet, and an optical element sheet having a plurality of optical elements arranged in an array on one surface. A light reflecting layer provided with a plurality of light reflecting patterns, and the width of the light reflecting layer in the direction perpendicular to the extending direction of each light reflecting pattern in the plurality of light reflecting patterns is xi (where i = 1, 2, 3,..., N), and the width xi at arbitrary positions of the plurality of light reflection patterns within the set range is measured at n locations (where n is a plurality), and the average value of these widths xi is μ Then, the following formula (1)

The value of the standard deviation σ of the width xi expressed by the following equation (2) is expressed by the following formula (2): 2.0 <σ <7.0 (2)
It satisfies the following condition.
According to the present invention, the light reflected by the light reflection pattern and the light transmitted through the optical sheet can be adjusted by adjusting the standard deviation σ of the width xi of the light reflection pattern in the light reflection layer. The distribution of the entire emitted light can be controlled without changing the shape of the element sheet. In particular, by adjusting the standard deviation σ of the width xi of the light reflection pattern within the range shown by the expression (2), the luminance distribution and the half-value angle are adjusted without visually recognizing unevenness in the image or the like due to the light transmitted through the optical sheet. be able to.

The optical element is a cylindrical lens having a substantially semi-cylindrical lens portion, and the optical element sheet is preferably a lenticular lens sheet in which cylindrical lenses are arranged in one direction, without changing the shape of the cylindrical lens. The emission angle of transmitted light can be controlled within a predetermined range, and the luminance distribution and half-value angle can be adjusted.
In addition, when a parallel light beam is incident from each lens unit side of the lenticular lens, the other surface is disposed in the vicinity of the light collecting unit where the incident light beam is collected, and the other surface includes the light collecting unit. It is preferable that an opening is provided in.

Further, the backlight unit for display according to the present invention is disposed directly in the light emission direction from the direct light source that irradiates the back surface of the image display element that defines the display image, and the light from the direct light source. Or any one of the optical sheets.
The backlight unit for display according to the present invention includes a surface light source including an edge light source and a light guide plate that irradiates light on the back surface of an image display element that defines a display image, and a light emission direction forward from the surface light source. The optical sheet according to any one of claims 1 to 3 is provided.
In addition, a liquid crystal display according to the present invention includes an image display element that defines a display image, and the display backlight unit according to claim 4 or 5.
According to the present invention, it is possible to adjust the luminance distribution and the half-value angle without visually recognizing unevenness in the image transmitted through the image display element of the liquid crystal display.

で表される幅ｘｉの標準偏差σの値が、
２．０＜σ＜７．０ （２）
なる条件を満たすようにしたことを特徴とする。
本発明によれば、光学素子や光学素子シートの形状を変えることなく光反射パターンの幅ｘｉの標準偏差σを（２）式で示す範囲内で調整することによって、光学シートを透過する光による画像等にムラを視認することなく、輝度分布や半値角を調整することができる。 The method for producing an optical sheet according to the present invention includes a layer of an ultraviolet curable resin having adhesiveness on a surface opposite to an optical element in an optical element sheet having a plurality of optical elements arranged in an array on one surface. And a step of irradiating the ultraviolet curable resin layer with ultraviolet rays from the optical element side of the optical element sheet to cure the region facing the optical element to form a cured portion and to make other regions uncured portions And a step of bonding a light reflecting layer that reflects light on the layer of the ultraviolet curable resin, and peeling the light reflecting layer, so that an uncured portion along the interface between the cured portion and the uncured portion of the ultraviolet curable resin. A step of separating the light reflecting layer in the region of the cured part while leaving the light reflecting layer in the region of the cured part, and the light reflecting layer in close contact with the uncured part of the ultraviolet curable resin forms a light reflecting pattern. Along with UV curable resin The region of the hardened portion forms an opening, and the width of the light reflecting pattern in the direction orthogonal to the extending direction of each light reflecting pattern is set as xi (where i = 1, 2, 3,..., N). When the width xi at a given position of the plurality of light reflection patterns within the measured range is measured at n places (where n is a plurality), and the average value of the width xi is μ, the following formula (1)

The value of the standard deviation σ of the width xi represented by
2.0 <σ <7.0 (2)
It is characterized by satisfying the following condition.
According to the present invention, by adjusting the standard deviation σ of the width xi of the light reflection pattern within the range represented by the expression (2) without changing the shape of the optical element or the optical element sheet, the light is transmitted through the optical sheet. The luminance distribution and the half-value angle can be adjusted without visually recognizing unevenness in the image or the like.

The standard deviation σ of the width xi is
(A) UV curable resin adhesive strength,
(B) Diffusion ratio of ultraviolet rays irradiated from the optical element side of the optical element sheet,
(C) the cohesive strength of the material of the light reflecting layer,
It is characterized in that it is set by increasing / decreasing at least one of the above.
By adjusting at least one of the above (A), (B), and (C), the standard deviation σ of the width xi of the light reflection pattern can be adjusted.
Further, after the step of laminating the light reflecting layer on the layer of the ultraviolet curable resin, a step of bonding the support to the light reflecting layer is provided, and the uncured portion of the ultraviolet curable resin is removed by peeling the support. The light reflecting layer of the cured portion was separated leaving the region of the light reflecting layer.
By peeling the support, a region corresponding to the opening of the light reflecting layer can be peeled and removed, leaving a region corresponding to the light reflecting pattern.

According to the optical sheet, the backlight unit for display, and the liquid crystal display according to the present invention, the emission angle of the transmitted light without changing the shape of the optical element sheet having the optical element that collects the light and emits it in a specific direction. Can be controlled within a predetermined range, and the luminance distribution and half-value angle can be adjusted without recognizing unevenness of the emitted light.
In addition, according to the method for manufacturing an optical sheet according to the present invention, the optical characteristics can be adjusted by adjusting the standard deviation σ of the width xi of the light reflection pattern without changing the shape of the optical element sheet. Since it is not necessary to manufacture a mold corresponding to the optical characteristics, the manufacturing is easy and the cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram of a main part of a liquid crystal display device including an optical sheet according to the present embodiment, FIG. 2 is a partially enlarged view of the optical sheet, FIG. 3 is a partially enlarged view of a light reflecting pattern, and FIGS. FIGS. 6A, 6B, and 6C are diagrams showing light reflection patterns having different standard deviations.
A liquid crystal display device 1 as a liquid crystal display shown in FIG. 1 shows an example including an optical sheet and a backlight unit according to the first embodiment. The liquid crystal display device 1 includes a liquid crystal display element (liquid crystal panel) 5 in which a panel body 2 having a substantially rectangular plate shape is sandwiched between polarizing plates 3 and 4, and a liquid crystal display element 5. The backlight unit 6 is disposed on the back side and irradiates the liquid crystal display element 5 with light from the back side.
In addition, in this specification, the back side means the back side of the direction which irradiates the light of the light source with respect to the liquid crystal display element 5, and the front side means the light irradiation direction front side.

The backlight unit 6 is of a direct type, for example, and includes a layered optical member 8 and a light source unit 9 that irradiates the optical member 8 with light.
The optical member 8 is provided with, for example, a lenticular lens sheet 10 as an optical element sheet for controlling the light directivity of light emitted from the light source unit 9, and is further reflected polarized light into which light emitted from the lenticular lens sheet 10 is incident. A separation sheet 11 and a low refractive material layer 12 filled between the lenticular lens sheet 10 and the reflective polarization separation sheet 11 are provided.
The lenticular lens sheet 10 is provided with a lens portion 15 in which a plurality of cylindrical lenses (lenticular lenses) 15a are arranged in parallel as unit lenses on the emission surface side of the base sheet 14. A light reflection layer 17 having an opening 16 corresponding to the focal position of the cylindrical lens 15a is provided on the incident surface side of the base sheet 14 (see FIG. 2). Here, in this embodiment, the lenticular lens sheet 10 and the light reflection layer 17 constitute an optical sheet 22.
As an example of the lens unit 15, in addition to the lenticular lens, a microlens unit in which a plurality of substantially hemispherical microlenses are arranged in a matrix or a plurality of cylindrical lenses are the same so that their length directions cross each other. Examples thereof include a cross wrench lens portion arranged on a plane.

The reflective polarization separation sheet 11 is configured to transmit linearly polarized light in one polarization direction of the light emitted from the lenticular lens sheet 10 and to reflect linearly polarized light in the other polarization direction. In this embodiment, the reflective polarization separation sheet 11 scatters and reflects linearly polarized light in the other polarization direction. As an example of the reflection type polarization separation sheet 11, for example, a birefringent multilayer film, a cholesteric liquid crystal layer, and a retardation plate can be cited.
The light source unit 9 has a substantially rod-like shape such as a cold cathode tube (CCFL) in a reflecting plate 21 having a scattering reflection layer 20 made of, for example, a white PET film in which ultrafine particles of air are dispersed and mixed. A plurality of light sources 19 are arranged at predetermined intervals. A diffusion film 23 for diffusing light from the light source 19 is disposed on the front side of each light source 19,

In the lenticular lens sheet 10 as the optical element sheet shown in FIGS. 1 and 2, the material of the base sheet 14 is PET (polyethylene terephthalate), acrylic sheet, PC (polycarbonate) sheet, which are well known in the art. Etc. are used. The cylindrical lens 15a as an optical element is formed using a thermoplastic or UV curable resin. Alternatively, the cylindrical lens 15a and the base sheet 14 may be simultaneously formed by extrusion or an injection molding method.
The light reflection layer 17 is configured by regularly arranging the light reflection pattern 18 arranged on the incident surface side of the lenticular lens sheet 10 in synchronization with the arrangement of the cylindrical lenses 15 a (lens sheet array) of the lens unit 15. Yes.
As the light reflection pattern 18, it is preferable to use a white pigment, a metal vapor deposition layer, and a pattern having high reflectivity and low light absorption. As the white pigment, titanium dioxide (TiO ₂ ), barium sulfate, and magnesium oxide well known in the art are used, and silver or the like is used as the metal deposition layer.
The light reflection pattern 18 is formed, for example, in a substantially strip shape using a transparent resin in which white titanium oxide fine particles are dispersed and mixed, and is arranged substantially in parallel along the extending direction of the cylindrical lens 15a. In the light reflection layer 17, the opening 16 is disposed to face the central thick portion of the cylindrical lens 15 a, and the light reflection pattern 18 is disposed to face the boundary region between the adjacent cylindrical lenses 15 a and 15 a. ing.

Since the light reflection pattern 18 is manufactured by a light reflection pattern transfer method of the light reflection layer 17 described later, for example, the opening 16 is formed from the light reflection layer 17 that is pressure-bonded to the UV curable adhesive layer 24 laminated on the base sheet 14. The part corresponding to is peeled off and the part that becomes the light reflection pattern 18 is left. Therefore, as shown in FIG. 3, minute irregularities in micron units remain at both ends of each light reflection pattern 18, that is, the edge portion 18a.
The light reflecting layer 17 according to the present embodiment positively utilizes the edge portions 18a of the light reflecting patterns 18 to adjust the size and frequency of occurrence of fine irregularities on the edge portions 18a, thereby opening the light reflecting layer 17. The optical characteristics of the light passing through the section 16 are adjusted.
That is, in FIG. 3, the width in the direction orthogonal to the extending direction of each light reflecting pattern 18, that is, the direction orthogonal to the extending direction of the cylindrical lens 15a is xi (μm) (where i = 1, 2, 3,... , N). The value of the width xi slightly increases or decreases due to minute unevenness in units of microns formed at both edge portions 18 a of the light reflection pattern 18. Then, the width xi at arbitrary positions different from each other in the plurality of light reflection patterns 18 included in a certain fixed range in the light reflection layer 17 is measured at n places (where n is a plurality), and the average value of the widths xi Is μ (μm).
Next, the standard deviation σ of the width xi is obtained by the following formula (1) from each measured value of the width xi, the number of times of measurement n, and the average value μ.

Then, the standard deviation σ of the light reflection pattern 18 is selected within a range in which the value of the standard deviation σ of the obtained width xi satisfies the condition that the following expression (2) is satisfied, and its optical characteristics are set.
2.0 <σ <7.0 (2)
Here, if the standard deviation σ is within the above range, the luminance ratio decreases as the standard deviation σ increases, the half-value angle increases, and the image of the liquid crystal display element 5 does not become uneven. Therefore, the optical characteristic can be adjusted without changing the shape of the lenticular lens sheet 10 by changing the standard deviation σ of the light reflection pattern 18 within the above range.
On the other hand, if the standard deviation σ is 2.0 or less, the observed image is not uneven, but the luminance ratio of light passing through the optical sheet 22 and the V half-value angle are hardly changed, so that the optical characteristics cannot be adjusted. Further, when the standard deviation σ is 7.0 or more, such a problem that unevenness occurs in the image of the liquid crystal display element 5 is not preferable.
In addition, when the unevenness | corrugation in the edge part 18a of the both sides of the light reflection pattern 18 is large so that visual confirmation is possible, since a shadow arises in a transmitted image, it cannot employ | adopt for the liquid crystal display device 1. FIG.

In order to adjust the standard deviation σ of the width xi of the light reflection pattern 18 within the range of the expression (2), for example, (A) increase or decrease adjustment of the adhesive force of the ultraviolet curable resin that is the material of the light reflection pattern 18;
(B) When the light reflection pattern 18 is manufactured, the diffusion ratio of ultraviolet rays irradiated from the cylindrical lens 15a side of the lenticular lens sheet 10 is increased or decreased.
(C) Increase / decrease the cohesive force of the ultraviolet curable resin that is the material of the light reflecting pattern 18;
Any one of the above may be performed. Therefore, the adjustment means (A) to (C) may be performed in advance, and the relationship between the increase / decrease ratio and the standard deviation σ of the width xi of the light reflection pattern 18 may be set as data.

Next, a manufacturing method by transferring the light reflection pattern 18 according to the present embodiment will be described with reference to FIGS. As a method for transferring the light reflection pattern 18, a method disclosed in Japanese Patent Application Laid-Open No. 2005-37694 can be basically used.
First, in FIG. 4, in the previously manufactured lenticular lens sheet 10, for example, a UV curable adhesive material is bonded to the surface of the substrate sheet 14 opposite to the surface on which the cylindrical lenses 15a are arranged. Layer 24 is laminated. Then, the portion corresponding to the cylindrical lens 15a of the UV curable adhesive material layer 24 is cured by irradiating ultraviolet rays UV from the cylindrical lens 15a side to form a cured portion 24a and an uncured portion 24b.
Here, the UV curable adhesive material constituting the UV curable adhesive material layer 24 is not particularly limited as long as it is a UV photosensitive resin material having a property that the adhesiveness disappears when exposed to light. For example, a monomer, oligomer and / or prepolymer photopolymerizable compound, if necessary a non-photopolymerizable thermoplastic resin, a photopolymerization initiator activated by actinic rays, and if necessary a thermal polymerization inhibitor contains. As a commercial product of such a photosensitive resin, a chromalin (registered trademark: DuPont) film and the like can be mentioned.

Next, a white layer 17 </ b> A made of, for example, a white pigment is bonded to the surface of the UV curable adhesive material layer 24 as the light reflecting layer 17. A support film (support) 25 made of, for example, a thin layer of synthetic resin is pressed and bonded onto the white layer 17A.
Then, when the support film 25 is peeled off as shown in FIG. 5, the white layer 17A is peeled off at the cured portion 24a of the UV curable adhesive layer 24 and the white layer 17A is peeled off at the uncured portion 24b by the adhesive force. Is maintained in an adhesive state with the UV curable pressure-sensitive adhesive layer 24, and thus the white layer 17A is divided by the extended surface 17b along the interface 26 between the cured portion 24a and the uncured portion 24b. At this time, fine irregularities due to peeling occur on the white layer 17a remaining in the uncured portion 24b in an adhesive state, that is, the edge portions 18a at both ends of the light reflecting pattern 18.
In this way, the light reflection pattern 18 composed of the white layer 17A can be transferred to the uncured portion 24b of the UV curable adhesive material layer 24, and the white layer 17A on the cured portion 24a is peeled off to open the opening portion. 16 is formed. A pattern of the light reflection layer 17 in which the light reflection patterns 18 and the openings 16 are alternately arranged can be formed. Thereafter, the uncured portion 24b of the UV curable adhesive layer 24 is cured.
With this method, it is possible to easily form the light reflection layer 17 in which the cylindrical lenses 15a and the light reflection patterns 18 are arranged in correspondence with each other.

Here, the above-described means (A), (B), and (C) for adjusting the standard deviation σ of the light reflection pattern width will be described.
In the means (A), the type of white pigment used for the light reflection pattern 18 is arbitrarily selected. Then, in the above-described transfer method, the white layer 17A breaks down at the interface 26 between the cured portion 24a and the uncured portion 24b of the UV curable adhesive material layer 24, and only the portion of the white layer 17A laminated on the cured portion 24a. Is peeled off to form the light reflection pattern 18.
The layer destruction of the white layer 17A greatly affects the shape change of the edge portion 18a of the light reflection pattern 18, and the standard deviation σ of the width xi of the light reflection pattern 18 is changed. The stronger the cohesive force (between layers) of the white layer 17A, the more severe the layer destruction occurs, and the standard deviation σ of the width xi of the light reflection pattern 18 is increased.
Therefore, the standard deviation σ of the width xi of the light reflection pattern 18 can be adjusted by selecting white pigments having different cohesive forces and laminating them as the white layer 17A. Further, the white layer 17A has a two-layer structure in which the support film 25 is provided with the white layer 17A. However, the separation of the white layer 17A from the support film 25 and the film thickness of the white layer 17A are also different from the light reflection pattern width. Can be a parameter that varies the standard deviation σ.

The means (B) performs pattern transfer by changing the degree of diffusion of ultraviolet rays UV for forming the cured portion 24a and arbitrarily changing the degree of cure of the UV curable adhesive layer 24. For example, if the degree of cure of the UV curable adhesive material is lowered, the adhesive strength is weakened, so that the white layer 17A is severely broken and the standard deviation σ of the light reflection pattern width is increased.
(C) The means uses a UV curable adhesive material having various adhesive forces to perform light reflection pattern transfer. Also in this method, the standard deviation σ of the width xi of the light reflection pattern 18 can be adjusted by changing the transferability of the white layer 17A by the strength of the adhesive force.

FIGS. 6A, 6B, and 6C show the state of the edge portion 18a of the light reflection pattern 18 that changes by adjusting the standard deviation σ of the width xi of the light reflection pattern 18, respectively. In the drawing, the light reflection pattern 18 shown in (a) has a relatively small standard deviation σ of the width xi, and the standard deviation σ of the width xi of the light reflection pattern 18 shown in (c) is relatively large, as shown in (b). The standard deviation σ of the width xi of the light reflecting pattern 18 is in the middle.
The standard deviation σ of the width xi of the light reflection pattern 18 is 2.0 <σ <using the above-described means (A), (B), or (C), or a combination of two or more means. Adjust to meet 7.0.

  According to the liquid crystal display device 1 according to the present embodiment, the light emitted from the light source 19 travels to the optical sheet 22. In the optical sheet 22, a part of the light is controlled to fall within a predetermined range by the cylindrical lens 15 a of the lenticular lens sheet 10 through the opening 16 and passes through the liquid crystal display element 5 through the diffusion plate 32. The other part of the light is reflected by the light reflecting pattern 18 and returned to the reflecting plate 21 side. Then, after repeating reflection with the reflecting plate 21, any of the light passes through the opening 16 and enters the optical sheet 22.

As described above, according to the optical sheet 22 according to the present embodiment, the standard deviation σ of the width xi of the light reflection pattern 18 is in the range of 2.0 <σ <7.0 without changing the shape of the lenticular lens sheet 10. By controlling at, the luminance ratio and the half-value angle can be changed and the different optical characteristics can be exhibited without visually recognizing unevenness in transmitted light such as an image of the liquid crystal display element 5 or the like. In addition, when the optical sheet 22 is employed in the backlight unit 6 or the liquid crystal display device 1, the different optical characteristics described above can be obtained.
Therefore, it is possible to control so that different optical performances can be exhibited using the lenticular lens sheet 10 having the same shape without manufacturing a plurality of shapes of optical sheets corresponding to the optical characteristics using a mold.

Examples of the present invention will be described below.
As the optical sheet 22, three types of lenticular lens sheets 10 in which the lens pitch of the semi-cylindrical cylindrical lens 15 a is 140 μm, 180 μm, and 216 μm using a UV curable acrylic resin on a base material sheet 14 made of PET, respectively. It was created.
A UV curable adhesive layer 24 was laminated by applying a photosensitive acrylic resin adhesive as a UV curable adhesive on the surface of each lenticular lens sheet 10 opposite to the cylindrical lens 15a.
Then, the portion corresponding to the cylindrical lens 15a of the UV curable adhesive material layer 24 is cured by irradiating ultraviolet rays from the cylindrical lens 15a side to form a cured portion 24a, and other regions are left as uncured portions 24b.
Next, a transparent resin in which titanium dioxide (TiO ₂ ) fine particles, which are white pigments, are dispersed and mixed is applied as a white layer 17A on the UV curable adhesive layer 24. The transparent resin was produced by mixing a styrene resin (Sanyo Kasei, trade name Haimer ST120), a dispersant (BYK Chemical, trade name Disper Bike 163) and a solvent (methyl ethyl ketone).
A polyethylene terephthalate film (manufactured by Toray Industries, Inc., Lumirror 25 μm thick) was pressure bonded as a support film 25 on the white layer 17A.
Then, by peeling the support film 25, the white layer 17A is peeled off at the cured portion 24a of the UV curable adhesive layer 24, and the white layer 17A portion on the uncured portion 24b is the same as the white layer 17A of the cured portion 24a. It is divided along the extended surface 17b of the interface 26 by the layer breakage with the part.
In this manner, an optical sheet 22 in which the light reflection patterns 18 and the openings 16 were alternately arranged on the light incident surface of the lenticular lens sheet 10 was manufactured.
With respect to the optical sheet 22 manufactured as described above, the optical sheet 22 having different optical characteristics by varying the standard deviation σ of the width xi of the light reflecting pattern 18 by the above-described means (A) to (C). Created.

Next, a method for calculating the standard deviation σ of the width xi of the light reflection pattern 18 will be described.
In order to calculate the standard deviation σ of the width xi, a method for measuring the width xi of the manufactured light reflection pattern 18 will be described. For the measurement of the width xi, a large liquid crystal panel inspection microscope MHL100 (manufactured by Olympus Corporation) and an image analysis device LUZEX (manufactured by Nireco Corporation) were used.
First, the magnification was set to 20 times using a microscope, and the surface state of the light reflection pattern 18 on the light reflection layer 17 side was displayed. Next, using an image analysis apparatus, the grayscale image of the light reflection pattern 18 obtained from the microscope is binarized by providing an appropriate threshold value (1 for pixels having brightness higher than the threshold value, 0 for dark pixels). )
By utilizing the difference in brightness between the light reflection pattern 18 and other portions, the binary data in the direction orthogonal to the extending direction of the light reflection pattern 18 is processed to obtain the width xi (μm) of the light reflection pattern 18. Calculated. Then, for example, the width xi of the plurality of light reflection patterns 18 was measured at n positions in an arbitrary pixel range set to 100 μm × 100 μm. For the width xi, the average value μ (μm) was calculated from the measured values at n locations, and the standard deviation σ was calculated from the dimensional distribution by Equation (1).

At each lens pitch of the lenticular lens sheet 10 described above, the optical sheet 22 created by varying the standard deviation σ of the light reflection pattern width xi by the means (A) to (C) is incorporated in the liquid crystal display device 1. , Brightness, V half-value angle (half-value angle with respect to the horizontal direction), and the display state of the image were confirmed.
The luminance was measured by incorporating the prepared optical sheet 22. The luminance was measured by arranging the light receiver of the luminance measuring device in a direction perpendicular to the surface of the liquid crystal display element 5 of the liquid crystal display device 1.
Table 1 below shows the determination result of the optical sheet 22 using the lenticular lens sheet 10 with a pitch of 140 μm. For the liquid crystal display device 1 employed in the example as a reference, the luminance when 3M BEFIII was used instead of the optical sheet 22 was measured, and the ratio of the luminance when the value was 1 was expressed as the luminance ratio. .

In the results shown in Table 1, high brightness can be ensured for any of the standard deviations σ of the light reflection pattern width xi satisfying σ ≦ 2.0. However, within this range, there is almost no change in luminance and half-value angle, and no optical characteristic adjustment function is recognized. Further, with respect to the case where σ ≧ 7.0, there was a problem that the randomness of the width xi of the light reflection pattern 18 was too large, and unevenness could be visually recognized in the image passed through the liquid crystal display element 5.
On the other hand, the standard deviation σ of the light reflection pattern width xi is the following formula (2):
2.0 <σ <7.0 (2)
As for those satisfying the conditions shown in (2), the luminance ratio changed within the range of 0.874 to 0.901 and the half-value angle within the range of 28.0 ° to 29.5 °, depending on the conditions. Changes in brightness and half-value angle within this range can greatly contribute to fine adjustment of optical characteristics corresponding to demands.

Similar results were obtained for the other optical sheets 22 in which the lens pitch of the lenticular lens sheet 10 was 180 μm and 216 μm, so that the standard deviation σ of the light reflection pattern width xi was 2. It was found that comprehensive optical characteristics can be adjusted by satisfying the condition of 0 <σ <7.0.
In the optical sheet 22 used in this example, the ratio of the width of the opening 16 to the pitch width of the light reflection pattern 18 was 36 ± 1% at any lens pitch described above, and was optimized.

In the above-described embodiment, the configuration in which the optical sheet 22 according to the present embodiment is employed in the direct liquid crystal display device 1 has been described. However, the present invention is not limited to such a configuration, and other configurations, For example, as shown in FIG. 7, it may be adopted in an edge light type liquid crystal display device 30.
The liquid crystal display device 30 shown in FIG. 7 will be described using the same reference numerals for the same or similar parts and members as those of the first embodiment.
In the liquid crystal display device 30, the light from the light source 19 disposed on the side is reflected by the light guide plate 31 and emitted toward the optical sheet 22. The liquid crystal display element 5 is disposed on the front side of the optical sheet 22 via a diffusion plate 32.
A part of the light traveling from the light source 19 to the optical sheet 22 through the light guide plate 31 is controlled to have an emission angle within a predetermined range by the cylindrical lens 15 a through the opening portion 16. To Penetrate. The other part of the light is reflected by the light reflection pattern 18 and returned to the light guide plate 31 side. Then, after repeating reflection at the interface with the light guide plate 31 or within the light guide plate 31, either passes through the opening 16 and enters the optical sheet 22.

In the above-described embodiment and modification, a cold cathode tube light source lamp is used as the light source 19, but a fluorescent lamp, LED, EL, or the like can be used instead. The light source 19 is a rod-like cold cathode tube, but it may be a spot-like or planar light source.
The optical sheet according to the present invention is not limited to a lenticular lens sheet, and can be applied to a prism sheet or other unit lenses arranged in an array. The optical sheet according to the present invention is not limited to a backlight unit or a liquid crystal display device, and can be used for various light irradiation devices such as a solar cell and a screen.

It is principal part sectional drawing of the liquid crystal display device containing the optical sheet by embodiment of this invention. It is the elements on larger scale of the optical sheet shown in FIG. It is the elements on larger scale of a light reflection pattern. It is a figure which shows the manufacturing process of a light reflection pattern, Comprising: It is a longitudinal cross-sectional view which shows the state which laminated | stacked the UV hardening type adhesive material layer, the white layer, and the support film on the base material sheet | seat of a lenticular lens sheet. It is a longitudinal cross-sectional view which shows the state which peeled the support film from the state shown in FIG. 4, and divided the white layer. (A), (b), (c) is the elements on larger scale of the light reflection pattern from which a standard deviation differs. It is principal part sectional drawing of the liquid crystal display device of the edge light system by a modification. It is a figure which shows the luminance distribution with respect to the viewing angle in a liquid crystal display device.

Explanation of symbols

1, 30 Liquid crystal display device (liquid crystal display)
5 Liquid crystal display element 6 Backlight unit 10 Lenticular lens sheet 15a Lenticular lens (optical element)
DESCRIPTION OF SYMBOLS 15 Lens part 16 Opening part 17 Light reflection layer 17A White layer 18 Light reflection pattern 18a Edge part 22 Optical sheet 24 UV curable resin layer 24a Curing part 24b Uncured part 25 Support film

Claims (9)

An optical element sheet having a plurality of optical elements arranged in an array on one surface;
A light reflection layer provided with a plurality of light reflection patterns for restricting an incident range of light on each of the plurality of optical elements on the other surface of the optical element sheet;
The width in the direction orthogonal to the extending direction of each light reflecting pattern in the plurality of light reflecting patterns of the light reflecting layer is set as xi (where i = 1, 2, 3,..., N), and within the set range. When the width xi at an arbitrary position of the plurality of light reflection patterns is measured at n places (where n is a plurality), and the average value of the widths xi is μ, the following formula (1)

The value of the standard deviation σ of the width xi expressed by the following equation (2) is expressed by the following formula (2): 2.0 <σ <7.0 (2)
An optical sheet characterized by satisfying the following condition.   The optical element according to claim 1, wherein the optical element is a cylindrical lens having a substantially semi-cylindrical lens portion, and the optical element sheet is a lenticular lens sheet in which the cylindrical lenses are arranged in one direction. Sheet.   When a parallel light beam is incident from each lens unit side of the lenticular lens, the other surface is disposed in the vicinity of the light collecting unit where the incident light beam is collected, and the other surface includes the light collecting unit. The optical sheet according to claim 2, wherein an opening is provided in the region. A direct light source that irradiates light on the back of the image display element that defines a display image;
A display backlight unit comprising: the optical sheet according to any one of claims 1 to 3, which is disposed in front of the light emitting direction from the direct light source. A surface light source including an edge light source and a light guide plate that irradiates light to the back surface of the image display element that defines a display image;
A display backlight unit comprising: the optical sheet according to any one of claims 1 to 3 disposed in front of a light emission direction from the surface light source. An image display element for defining a display image;
A liquid crystal display comprising: the display backlight unit according to claim 4. Laminating a UV curable resin layer having adhesiveness on the surface opposite to the optical element in the optical element sheet having a plurality of optical elements arranged in an array on one surface;
Irradiating the ultraviolet curable resin layer with ultraviolet rays from the optical element side of the optical element sheet to cure a region facing the optical element to form a cured portion and making the other region an uncured portion; ,
Bonding a light reflecting layer that reflects light on the ultraviolet curable resin layer;
The light reflection layer in the region of the cured portion is left by separating the light reflection layer, leaving the light reflection layer in the region of the uncured portion along the interface between the cured portion and the uncured portion of the ultraviolet curable resin. And a step of separating the
The light reflecting layer in close contact with the uncured portion of the ultraviolet curable resin forms a light reflecting pattern, and the region of the cured portion of the ultraviolet curable resin forms an opening,
A width in a direction orthogonal to the extending direction of each light reflection pattern in the light reflection pattern is set as xi (where i = 1, 2, 3,..., N), and a plurality of the light reflection patterns within a set range. When the width xi at an arbitrary position is measured at n locations (where n is a plurality), and the average value of the width xi is μ, the following formula (1)

The value of the standard deviation σ of the width xi represented by
2.0 <σ <7.0 (2)
An optical sheet manufacturing method characterized by satisfying the following condition. The standard deviation σ of the width xi is
(A) Adhesive strength of the ultraviolet curable resin,
(B) The diffusion ratio of ultraviolet rays irradiated from the optical element side of the optical element sheet,
(C) Cohesive force of the material of the light reflecting layer,
The method for producing an optical sheet according to claim 7, wherein at least one of the above is set by adjusting to increase or decrease. Next to the step of laminating the light reflecting layer on the ultraviolet curable resin layer, a step of bonding a support to the light reflecting layer is provided.
9. The light reflecting layer of the cured part is separated by leaving the support so as to leave a region of the light reflecting layer of the uncured part of the ultraviolet curable resin. The manufacturing method of the optical sheet of description.

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