JP2003090905A - Optical layered body having controlled diffusing and transmitting characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical layered body having selective light diffusing property and light converging property so as to produce a brighter image in the viewing angle than a conventional one. SOLUTION: The optical layered body comprises the following light diffusing film and a light diffusing layer which diffuses and transmits light. The light diffusing film consists of two phases having different refractive indices to diffuse and transmit light and contains a large number of regions in which the one phase having the higher refractive index is present in the thickness direction of the film to form a columnar structure. An optical film is obtained by laminating the light diffusing film with the light diffusing layer as a pressure sensitive adhesive layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to controlled light scattering
The present invention relates to an optical laminate having a transmission characteristic.

[0002]

2. Description of the Related Art In a reflection type liquid crystal display device or a semi-transmission type liquid crystal display device, generally, incident light is transmitted through a liquid crystal layer, reflected by a reflection film, transmitted through the liquid crystal layer again, and displayed on the eyes of a viewer. When the light enters, an optical film is arranged on the surface of the liquid crystal layer and / or between the liquid crystal layer and the reflection film to scatter light, thereby making it possible to visually recognize an image in a wide viewing angle. Light scattering is also called light diffusion.

Typical methods of obtaining light diffusion include, for example, a method of dispersing transparent fine particles in a plastic film to scatter light, and a method of roughening the surface of the plastic film to scatter light.

Further, there is a method in which a birefringent film is composed of a superposed body of birefringent films in which minute regions having different birefringence characteristics are dispersed and distributed, and light is scattered by utilizing a refractive index difference between the birefringent film and the minute regions. Proposed (JP-A-11-174)
No. 211).

There is also proposed a film in which fine crystal regions are dispersed and distributed in a polymer film, and the fine regions and other portions have different refractive indexes and exhibit light scattering properties (Japanese Patent Laid-Open No. 1-58242).
1-326610, JP 2000-266936.
JP-A-2000-275437, etc.).

Further, there has been proposed a method in which a pressure-sensitive adhesive used when laminating the above-mentioned films contains a filler having a refractive index different from that of the pressure-sensitive adhesive (Japanese Patent Laid-Open No. 1-58242).
No. 1-223712).

[0007]

However, all of the above-mentioned light scattering methods basically scatter light isotropically, so that an image is not displayed on a reflection type liquid crystal screen without a backlight. It has the drawback of darkening.

On the other hand, a light diffusing film having a large number of regions having a high refractive index formed in a polymer film in a columnar shape in the thickness direction of the film is commercially available. According to this light diffusion film, it is said that a selective viewing angle / diffusion performance can be realized depending on the incident angle of light.

Certainly, according to this diffusion film, it is possible to obtain a relatively bright image at a specific viewing angle as compared with a conventional scattering film of isotropic scattering type.

However, in a liquid crystal display device used even in a small amount of incident light such as a mobile phone, especially in a reflective or semi-transmissive liquid crystal display device, both front brightness is improved and visibility in a wide viewing angle is improved. In, a high brightness image is desired.

The present invention is intended to solve the problems of the prior art and has a selective light diffusing property and further a light collecting property so as to provide a brighter image in a wider viewing angle than ever before. It is intended to provide an optical laminate.

[0012]

The present invention provides the following in order to achieve the above object.

(1) A light-diffusing film which is composed of two phases having different refractive indexes which scatter and transmit light and which has a large refractive index and which has a large number of regions having a columnar structure extending in the thickness direction of the film. An optical layered body including a light scattering layer that scatters and transmits light.

(2) The axis of the columnar structure extending in the thickness direction of the light diffusion film is parallel to each other, and the axes are in the normal direction of the film (1).
The optical laminate according to item 1.

(3) The optical laminate according to (1) or (2), wherein the difference in the refractive index of at least two phases having different refractive indexes of the light diffusion film is in the range of 0.005 to 0.2.

(4) The optical layered body according to any one of (1) to (3), wherein the light diffusion film is manufactured from a polymer material having radiation sensitivity.

(5) The optical layered body according to any one of (1) to (4), wherein the light scattering layer contains a matrix resin and a filler.

(6) The difference in refractive index between the matrix resin and the filler of the light scattering layer is 0.05 to 0.5 (5)
The optical laminate according to item 1.

(7) The optical laminate according to (5) or (6), wherein the filler of the light scattering layer is spherical.

(8) The optical laminate as described in (5) to (7), wherein the matrix resin of the light scattering layer is a pressure sensitive adhesive.

(9) The optical laminate according to (8), wherein the light diffusion layer contains an adhesive as the matrix resin, and the light scattering layer is laminated in direct contact with the light diffusion film.

(10) The optical laminate as described in (1) to (7), wherein the light diffusion film and the light scattering layer are attached with an adhesive.

(11) The optical laminate according to any one of (1) to (10), wherein the optical laminate is an optical film in which the light diffusion film and the light scattering layer are integrated.

(12) The optical laminate as described in (1) to (8), wherein one or more other layers and / or films are interposed between the light diffusion film and the light scattering layer.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The optical layered body of the present invention is an optical layered body including a light diffusion film and a light scattering layer. Since there is an optical film composed of a light diffusion film and a light scattering layer as a particularly preferred embodiment, the present invention will be described below focusing on such an optical film, but a plurality of films may be provided between the light diffusion film and the light scattering layer or outside. It will be apparent from the following description that the same operation and effect can be obtained even if the other film and / or layer of (1) are present.

(Light Diffusing Film) The light diffusing film used in the present invention is composed of two phases having different refractive indexes for scattering and transmitting light, and one phase having a large refractive index has a columnar structure extending in the thickness direction of the film. The light diffusing film includes a large number of regions.

The light diffusion phenomenon in this light diffusion film will be described with reference to the drawings.

FIG. 1A is a cross-sectional view of a light diffusion film 1 having a high refractive index region formed in a cylindrical shape. A cylindrical high refractive index region 3 having a diameter close to the wavelength of light is formed in the polymer film 2 perpendicular to the film surface.
Such a cylindrical high-refractive index region 3 functions as a cylindrical lens, and light incident perpendicularly to the film, that is, parallel to the axis of the cylinder can exhibit scattering of a Gaussian distribution with a half width of about 10 to 20 degrees. . In the light diffusion film 1 of FIG. 1A, when the incident angle on the film 1 becomes large and the light is incident at an angle largely inclined with respect to the axis of the cylinder, the light loses its scattering property and exhibits high transparency. Like For example, light incident on the film surface at an angle of 45 to 60 degrees is hardly scattered and is transmitted.

FIG. 1 (b) shows the intensity of the transmitted light at the exit angle θ when the light incident on the surface of the film at a vertical angle (incident angle of zero degree) passes through the film. The transmitted light intensity has a Gaussian distribution, but this half-width can express the spread of scattering and selectivity. In FIG. 1B, the half width is 10 °.

By having such a selective light scattering transmission characteristic, when used in a reflection type or semi-reflection type liquid crystal display panel or the like, it is possible to have a reflection characteristic in which the brightness in the front visual field is selectively high.

The dimension of the cross-sectional shape of the columnar structure in the light diffusion film of the present invention is not limited, but 1
It is preferably within the range of 0 nm to 100 μm.

The method for forming the columnar structure in the light-diffusing film of the present invention is not particularly limited and can be selected and used from all conventionally known methods. However, a radiation-sensitive polymer film is selectively irradiated with radiation, A method of forming a columnar structure having a high refractive index is preferable. The polymer film may be a prepolymer or a monomer before irradiation with radiation, and may be polymerized by a method such as heating as necessary after irradiation with radiation.
The columnar structure is formed on the radiation-sensitive polymer film by irradiating the radiation-sensitive polymer film with radiation through a mask having a desired pattern formed on the surface of the radiation-sensitive polymer film. You can As a method for forming the mask, a method conventionally known as a photolithography method can be used. Alternatively, the radiation-sensitive polymer film may be scanned and irradiated with radiation to directly form the radiation-sensitive region. Alternatively, a method may be used in which the polymer film is perforated by a laser beam or other method, and the high refractive index material is filled in the holes.

Further, the formation and orientation of the region having the columnar structure is not limited to the circular surface or the direction perpendicular to the film, and the columnar structure having an elliptical shape or other cross-sectional shape may be used, and the shape and size thereof may not be constant. Alternatively, the columnar structures may be parallel to the film at an inclination angle. The degree of parallelism may be substantial.

The material of the radiation-sensitive polymer film that forms a high refractive index region by irradiation with radiation is not particularly limited, but for example, those commercially available from Dupont as OMNIDEX (registered trademark), HRF 150 and HRF 600. Can be used.

The refractive index of the polymer film base material and the high refractive index region is not particularly limited in the present invention and is determined in consideration of matching with other members such as an optical element to be used, but preferably 1. A refractive index within the range of 2 to 1.8, more preferably within the range of 1.35 to 1.8, and particularly around 1.48 is preferably used. The birefringence is not preferable because it causes coloration, but the birefringence may be present if the application allows the birefringence. It is preferable that the polymer film base material and the high refractive index region itself have high light transmittance.
The larger the difference in refractive index between the polymer film base material and the high refractive index region, the more preferable it is, but the difference in refractive index is set within the range of 0.005 to 0.2. If the refractive index difference is less than 0.005, it is not easy to obtain sufficient scattering characteristics.

The refractive index of the polymer film base material and the high refractive index region may change abruptly at the interface between these two phases, but it is preferable that the refractive index changes gradually so that desirable scattering characteristics can be obtained.

The thickness of the light diffusing film of the present invention is not limited, but is generally in the range of about 2 μm to about 100 μm, and is appropriately determined according to the application.

(Light Scattering Layer) Next, the light scattering layer in the present invention will be described in the same manner.

In the present invention, the light-scattering layer generally means a light-transmitting layer having an isotropic light-scattering property. Such a light scattering layer can be produced by various methods described in the prior art,
Generally, it can be constituted by containing a filler in a light transmissive resin matrix, and in particular, a resin having a matrix resin as an adhesive is preferable because it can be easily adhered and laminated with a light diffusion film. However, in the present invention, it is not an essential requirement that the light-scattering layer itself has tackiness, and a light-diffusing film and a light-scattering layer (that is, a light-scattering film) are separately provided with a pressure-sensitive adhesive (adhesion other than the pressure-sensitive adhesive as necessary). Agent) may be used for adhesive lamination, or a resin composition for forming a light-scattering layer may be formed (eg, extrusion molding, coating) on a light-diffusing film, or an adhesive layer may be formed. It is also possible to simply laminate the light diffusion film and the light scattering layer (that is, the light scattering film) without using.

The optical layered body of the present invention is not limited to a layer in which the light diffusion film and the light scattering layer are in direct contact with each other, and as described above, one or more layers may be provided in the middle or outside. And / or a film may be interposed.

FIG. 2 (a) is a schematic cross-sectional view of a light-scattering layer containing a filler in an adhesive or a matrix resin.
FIG. 2B shows the same scattering intensity of the transmitted light as in FIG. 1B. Here, comparing FIG. 1B and FIG. 2B,
It is shown that, unlike the selective scattering characteristic (scattering within a specific width) in the light diffusion film 1 of FIG. 1A, a gentle scattering characteristic is exhibited over almost the entire incident angle.

The light-scattering layer of the present invention is not particularly limited as long as it has a characteristic of transmitted light intensity as shown in FIG. 2 (b), and it is a plastic film containing transparent fine particles dispersed therein, and a minute film having different birefringence characteristics. A birefringent film having dispersed regions or a polymer film made of the same polymer in which fine crystal regions made of a superposed body or a polymer thereof are dispersed and distributed can be adopted. It is preferable to employ different layers. If it is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive may be used to intervene between the light-scattering layer and a layer or film laminated in contact with the other optical element (between the light-scattering layer and the light-diffusing film, and Since it is easy to prevent a decrease in the light transmission efficiency due to a space generated in a film or a layer other than the scattering layer and the light diffusion film (including, for example, between the reflection plate), the image contrast in the liquid crystal display device. It is also preferable from the viewpoint of improving visibility.

Since this type of light scattering layer can scatter incident light from a wide angle at a wide angle, it has the effect of utilizing light from a wide range and improving the visibility on a wide viewing surface.

Examples of the adhesive constituting the light scattering layer include:
Examples thereof include polyester resins, epoxy resins, polyurethane resins, silicone resins, acrylic resins and the like. You may use these individually or in mixture of 2 or more types. In particular, acrylic resins are excellent in reliability such as water resistance, heat resistance, light resistance, and have good adhesive strength and transparency,
Further, it is preferable because the refractive index can be easily adjusted to suit the liquid crystal display. As the acrylic pressure-sensitive adhesive, acrylic acid and its esters, methacrylic acid and its esters, acrylamide, homopolymers of acrylic monomers such as acrylonitrile or their copolymers, further, at least one of the acrylic monomers,
Examples thereof include copolymers with aromatic vinyl monomers such as vinyl acetate, maleic anhydride and styrene. In particular, main monomers such as ethylene acrylate, butyl acrylate, and 2-ethylhexyl acrylate that exhibit tackiness, vinyl acetate that serves as a cohesive force component, acrylonitrile,
Monomers such as acrylamide, styrene, methacrylate, and methyl acrylate, methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, and methylol acrylamide, which further improve adhesion and provide a starting point for crosslinking. A polymer composed of a functional group-containing monomer such as glycidyl methacrylate and maleic anhydride, having a Tg (glass transition point) in the range of -60 ° C to -15 ° C and a weight average molecular weight of 2
Those in the range of 0,000 to 1,000,000 are preferable.

As a curing agent for the pressure-sensitive adhesive, for example, a metal chelate-based, isocyanate-based, or epoxy-based cross-linking agent may be used alone or in combination of two or more. It is preferable that such an acrylic pressure-sensitive adhesive is blended so as to have a pressure-sensitive adhesive force in a range of 100 to 2,000 g / 25 mm in a state of containing a filler described later. Adhesion is 10
If it is less than 0 g / 25 mm, the environment resistance is poor, and peeling may occur especially at high temperature and high humidity.
If it exceeds mm, there is a problem that it cannot be re-attached, or even if it is formed, the adhesive remains. The refractive index of the acrylic pressure-sensitive adhesive is in the range of 1.45 to 1.70, particularly 1.5 to 1.
A range of 65 is preferred.

Typical examples of fillers for scattering light constituting the light-scattering layer include inorganic white pigments such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc and titanium dioxide. Examples include organic transparent or white pigments such as acrylic resin, polystyrene resin, epoxy resin, and silicone resin. When an acrylic pressure-sensitive adhesive is selected, silicon beads having a difference in refractive index specified in the present invention and epoxy resin beads have excellent dispersibility in the acrylic pressure-sensitive adhesive, and uniform and good light scattering properties can be obtained. preferable. Also,
The shape of the filler is preferably a spherical filler with uniform light scattering.

The particle size of such a filler is from 0.1 to
The range of 20.0 μm, preferably 0.5 to 10.0 μm is desirable. Particularly, the range of 1.0 to 10.0 μm is preferable. When the particle size is less than 0.1 μm, the effect of containing the filler becomes difficult to be exhibited, the light scattering property is deteriorated, and an aluminum color is likely to be generated on the background of the image. On the other hand, in order to obtain paper whiteness, it is necessary to finely disperse the light, but if the particle size exceeds 20.0 μm, the particles are too coarse and the background of the screen tends to be satin-like and the paper whiteness deteriorates. , The image contrast becomes poor.

The refractive index of the filler in the present invention needs to have a difference of 0.05 to 0.5 with respect to the refractive index of the pressure-sensitive adhesive, and preferably 0.05 to 0.3.
When the difference in refractive index is less than 0.05, the light scattering property cannot be obtained and good paper whiteness cannot be obtained. On the other hand, when the difference in refractive index is larger than 0.5, the internal scattering becomes too large and the total light transmittance deteriorates, so that paper whiteness cannot be obtained. Further, the refractive index of the filler is preferably lower than that of the pressure-sensitive adhesive because it is easy to adjust and the productivity is good.

The content of the filler with respect to the pressure-sensitive adhesive in the light-scattering layer of the present invention is preferably 1.0 to 40.0% by weight, and particularly preferably 3.0 to 20% by weight. When the content of the filler is less than 1.0%, the effect of light scattering due to the inclusion of the filler is difficult to be exhibited, and the light scattering property is reduced, which is the effect of the present invention, that is, the improvement of the front luminance and the visual recognition of a wide viewing angle. It becomes difficult to obtain the property. On the other hand, the content of filler is 4
If it exceeds 0.0% by weight, the adhesive strength of the light-scattering layer is reduced, peeling easily occurs, and durability may be impaired.
It becomes difficult to exhibit the function as the light scattering layer.

Further, a preferable example of the light scattering layer (light scattering film) formed by containing a filler in the resin matrix of the present invention is, for example, a planar film-like light scattering film made of a cellulose resin. In the film, the difference in refractive index from the resin is 0.05 or more and 0.5 or less, preferably 0.05 or more and 0.3 or less,
Further, there is a light scattering film containing a filler composed of organic or inorganic fine particles having a particle size of 5 nm or more and 50 μm or less. The reason why the cellulosic resin is used as the translucent resin is that birefringence is small and the film can be oxidized together with the polarizing plate to improve the adhesion. Further, the difference in refractive index of 0.05 or more is 0.
This is because if it is less than 05, a substantial scattering effect cannot be obtained, and in order to scatter, it is necessary to add a very large amount of filler. The difference in refractive index is 0.5 or less, preferably 0.3
The reason for setting the value below is that if it is larger than 0.5, it is necessary to reduce the content of the filler in the translucent resin, and a uniform light scattering layer cannot be obtained. The particle size is 5n
The reason for setting m is that if it is less than 5 nm, it becomes difficult to disperse it in the resin layer, and the available uniform fine particle material is limited to 5 nm. Further, the particle size of 50 μm or less means that when the particle size is larger than 50 μm, the filler protrudes and becomes uneven on the surface of the resin layer, the surface becomes white and the visibility of the screen is deteriorated, and the film becomes thick and a filler or a resin that can be molded. This is because there are restrictions on

As the filler to be contained in the light-scattering film, plastic beads are preferable, and those having a particularly high transparency and having a difference in the refractive index with the matrix resin as described above are preferable. As such plastic beads, melamine beads (refractive index: 1.57),
Acrylic beads (refractive index; 1.49), acrylic-styrene beads (refractive index; 1.54), polycarbonate beads, polyethylene beads, vinyl chloride beads and the like are used. In addition, cerium oxide (CeO ₂ refractive index: 1.6
It may be an inorganic filler such as 3). In the case of cerium oxide, fine particles up to about 5 nm are available. The particle size of these fillers is 5 nm as described above.
Those having a thickness of up to 50 μm are appropriately selected and used.

When a translucent filler is added as the organic filler as shown in the upper part, the organic filler easily precipitates in the resin composition, so an inorganic filler such as silica may be added to prevent precipitation. . It should be noted that the more the inorganic filler is added, the more effective it is in preventing the sedimentation of the organic filler, but it adversely affects the transparency of the coating film. Preferably, an inorganic filler having a particle size of 0.5 μm or less is used, for example, 0.1% by weight.
If the content is less than 10% by weight, sedimentation can be prevented.

The refractive index of the cellulosic resin is approximately 1.
Although it is in the range of 46 to 1.54, in comparison with the refractive index of the filler, when the resin used has a low refractive index, the light scattering film contains inorganic fine particles having a high refractive index, T
iO ₂ (refractive index: 2.3 to 2.7) Y ₂ O ₃ (refractive index;
1.87), La ₂ O ₃ (refractive index; 1.95), ZrO ₂ (refractive index; 2.05), etc., to the extent that the scattering property of the film can be maintained, and the refractive index is increased to adjust. You can

(Optical Film and Laminate Containing Light Diffusing Film and Light Scattering Layer) First, the optical film which is a preferred embodiment of the present invention will be explained.

Referring to FIG. 3 (a), in the present invention, two phases having the above-mentioned light diffusion characteristics and having different refractive indexes for scattering and transmitting light and having a large refractive index are formed in the film thickness direction. A schematic cross section of an optical film 13 in which a light-diffusing film 11 including a large number of regions having an extending columnar structure and a light-scattering pressure-sensitive adhesive layer 12 having the above-mentioned scattering property are laminated is shown. 3B shows the same light diffusion film 11 and non-adhesive light scattering film 14 as in FIG.
A schematic cross section of the optical film 16 adhered using the adhesive (preferably adhesive) 15 is shown. In FIG. 3 (C),
The transmitted light intensity similar to FIG.1 (b) and FIG.2 (b) of the optical film of FIG.3 (a) (b) is shown. In the optical films 13 and 16 of the present invention, the transmitted light intensity shown in FIG. 1B obtained by the light diffusion film 11 and the transmitted light intensity shown in FIG. 2B obtained by the light scattering adhesive 12 or the scattering film 14.
The transmitted light intensity as a sum of and is obtained as shown in FIG. As a result, it is possible to obtain both the improvement of the frontal luminance which can be obtained by the selective scattering characteristic and the visibility of the wide viewing angle which can be obtained by the gentle scattering characteristic.

As described above, in the optical layered body of the present invention, the light diffusing film and the light scattering layer do not necessarily have to be in direct contact with each other, and one or more other structures may be provided in the middle or outside. Layers or films may intervene.
The intermediate or outer layer or film is, for example, a polarizing film, an antireflection film, a retardation film, or λ / 2.
It may be a film, a λ / 4 film, a filter, a protective layer, a liquid crystal layer, a light emitting layer, an electrode layer, or any other light transmissive layer or film having or not having an optical function. Further, a light-impermeable or light-reflective layer or film may be included outside the light diffusion film and the light scattering layer. Further, the light diffusion film and the light scattering layer do not have to be one layer each, and may include two or more layers.

And, these plural layers or films do not necessarily have to be adhered to each other. It may be laminated in the optical device.

However, the most preferable embodiment of the present invention is an optical film in which a light diffusion film and a light scattering layer are laminated and integrated.

In the case of an optical film in which a light diffusing film and a light scattering adhesive layer are laminated and integrated, a release film is laminated on the light scattering adhesive layer for commercialization, and the release film is used when used in an optical device. Can be peeled off and used.

The optical film or laminate of the present invention comprises
Preferably, it is useful as an optical film or a laminate of a liquid crystal display device, particularly a reflective or semi-transmissive liquid crystal display device.

4 and 5 show an example of a liquid crystal display device. Glass substrates 21 and 22 on which electrodes (not shown) are formed
There is a liquid crystal layer 23 in between, and an optical film 24, which is a laminate of a light diffusion film and a light scattering layer, is generally disposed on the light incident side glass substrate 22 (FIG. 4), or It is arranged on the surface of the reflection film 25 under the glass substrate 21 on the reflection side (FIG. 5). When the retardation film 26 and the polarizing film 27 are used, they are generally placed outside the optical film 24 if they are present. The optical films 24 may be arranged on both sides, and the configuration of the liquid crystal display device is not limited to the illustrated example. A retardation plate 26 constituting such a liquid crystal display device,
For the polarizing film 27, the electrode layer, and the liquid crystal layer,
Even in a laminate in which the light diffusion film and the light scattering layer are combined in any order, both the front selective light diffusion property of the light diffusion film provided by the present invention and the isotropic scattering transmission property of the light scattering layer can be obtained. It is obvious that

As an example of the liquid crystal display device, a mobile phone will be described. An optical film as shown in FIG. 3 is used, and an optical film 33 is installed on a display screen 32 of the mobile phone 31 as shown in FIG. It is preferable that the optimum scattering characteristics can be obtained. In such a mobile phone, when the viewer 34 looks at the mobile phone 31, the light 35 incident from a wide range from the upper back of the viewer to the upper front thereof can be used and is reflected by the liquid crystal display element. At this time, the light can be mainly scattered and condensed and reflected mainly in the direction of the viewer 34. Such scattering / reflection characteristics improve the brightness of an image in the most frequently used mode when viewing a display screen of a mobile phone or the like.

[0063]

EXAMPLES Example 1 Referring to FIG. 50 μm thick coated on polyethylene terephthalate film 41 as a photosensitive polymer
OMPNIDEX, HRF6042 manufactured by DuPont, was used to adhere a mask 43 having a circular hole pattern to the surface of the photosensitive polymer layer 42 by a hard contact method. However, the circular hole pattern of the mask has a size of 500
The average was 2 μm in the range of nm to 30 μm.

Ultraviolet rays 44 obtained from a mercury lamp were condensed into parallel light by a lens system, and were irradiated from above the mask 43 at an irradiation angle of 90 degrees with respect to the normal line. The irradiation time was several seconds to several minutes. Then, it heat-processed at 120 degreeC for 1 hour.

As a result, a light diffusing film having a high refractive index region having a cross-sectional structure according to the hole pattern of the mask and having a columnar structure in the film normal direction was obtained. The polymer matrix of the light diffusion film had a refractive index of 1.47, and the high refractive index region had a refractive index of 1.52.

Acrylic adhesive 10 having a refractive index of 1.50
A filler was added to a base paint in which 1.5 parts of an isocyanate-based curing agent (D-90 Soken Chemical Co., Ltd.) was added to 0 parts, and the mixture was stirred with an azitase for 1 hour. The prepared pressure-sensitive adhesive was applied to a 38 μm release sheet (PET3801, manufactured by Lintec Co., Ltd.) so that the thickness after drying would be 25 μm.
38 μm on the light-scattering layer after drying to form the light-scattering layer
The release sheet (K-14, manufactured by Teijin Ltd.) was adhered to obtain a light-scattering pressure-sensitive adhesive sheet. Here, as the filler, silicon resin beads, a refractive index of 1.43, and an average particle diameter of 1.
The content was 0 μm, the content was 3%, and the HAZE value of the light scattering layer was 25. The light-scattering pressure-sensitive adhesive was attached to the light-diffusing film to obtain the optical film of the present invention.

The transmission and scattering characteristics of the optical film thus obtained were measured as follows. As shown in FIG. 8, the light emitted from the light source 53 is incident on the optical film 51 on which the reflection plate 52 is arranged, and the light reflected and emitted from the film 51 is measured by changing the position of the light detector 54, and the reflected light The relation between the direction and angle of the incident light (direction and angle with respect to the traveling direction of the incident light) and the scattered reflected light intensity was obtained. Also,
By changing the angle of the optical film 51 with respect to the light source 53, the incident direction and the angle of the incident light are changed, and the direction and angle of the reflected light (emitted light) (direction and angle with respect to the traveling direction of the incident light) are similarly changed. The relationship between scattered reflected light intensity was obtained. The directions and angles of the incident light and the reflected light are similar to those described above with reference to FIGS. 1 to 3, but the reflected light intensity at the reflection angle 0 is the intensity of the light entering the eyes of the viewer. So it is important.

FIG. 9A shows the scattered reflection light intensity when light is incident at a low angle with respect to the perpendicular direction of the optical film 51, and FIG. 9B shows the perpendicular direction of the optical film 51. The scattered reflection light intensity when the light is incident at a high angle is shown. In all cases, the intensity of scattered reflected light in front of the film is high, and it is excellent at a relatively wide angle, and a generally high intensity of scattered reflected light is observed over a wide angle in front of the film. Is recognized. The reflected light is efficiently condensed on the front surface, and not only the front brightness is improved, but also the moderate brightness, that is, the visibility with a wide viewing angle is obtained even in a portion at an angle to the normal direction of the film. I was able to.

Example 2 In addition, the content of silicone resin beads as a filler was 2
The HAZE value is 15 in the same manner as in Example 1 except that the percentage is
To obtain a light-scattering adhesive. This light-scattering pressure-sensitive adhesive was attached to the light-diffusing film using a release sheet to obtain the optical film of the present invention.

The reflection and scattering characteristics were evaluated in the same manner as in Example 1.

As in Example 1, the reflected light is efficiently condensed on the front surface to improve the front brightness, and also to obtain a suitable brightness in the portion at an angle with respect to the normal direction of the film. That is, visibility with a wide viewing angle could be obtained.

Example 3 For 100 parts of an acrylic adhesive having a refractive index of 1.50,
A filler was added to a base coating material to which 1.5 parts of an isocyanate curing agent (D-90 Soken Chemical Co., Ltd.) was added, and the coating material was prepared by stirring for 1 hour with azitase. Each coating material was applied to a 38 μm release sheet (PET3801, manufactured by Lintec Co., Ltd.) with a comma coater to give a thickness of 25 μm.
And then dried to form a light-scattering layer,
A 38 μm release sheet (K-14, manufactured by Teijin Ltd.) was attached onto the light scattering layer to obtain a light scattering pressure-sensitive adhesive sheet. Here, the filler was an epoxy resin filler, the refractive index was 1.59, the average particle size was 5.5 μm, and the content was 3%, and the haze value of the light scattering layer was 30. This sheet was attached to a light diffusion film to obtain the optical film of the present invention.

The reflection and scattering characteristics were evaluated in the same manner as in Example 1.

Similar to the first embodiment, the reflected light is efficiently condensed on the front surface to improve the front brightness, and also to obtain a suitable brightness at the portion at an angle with respect to the normal direction of the film. That is, visibility with a wide viewing angle could be obtained.

Example 4 Further, the content of epoxy resin beads as a filler was 2
A HAZE value of 19 was obtained in the same manner as in Example 3 except that the percentage was changed to%.
To obtain a light-scattering adhesive. This light-scattering pressure-sensitive adhesive was attached to the light-diffusing film using a release sheet to obtain the optical film of the present invention.

The reflection and scattering characteristics were evaluated in the same manner as in Example 1.

Similar to the first embodiment, the reflected light is efficiently focused in the center to improve the frontal brightness, and also the moderate brightness is obtained in the portion at an angle to the normal direction of the film. That is, visibility with a wide viewing angle could be obtained.

Comparative Example The reflection and scattering characteristics of a conventional simple light-scattering film (not laminated with the light-diffusing film of the present invention) were examined in the same manner as in the examples.

The results are shown in FIG. FIG. 10A shows the low-angle incident scattered light reflection intensity, and FIG. 10B shows the high-angle incident scattered light reflection intensity. Compared with FIG. 9, the scattered reflection intensity of the low-angle incident light is reflected at a very narrow angle, and the intensity at the reflection angle of 0 °, that is, the intensity in the viewer direction is lower than that of the embodiment, and the high-angle incident light is high. It is recognized that the scattered reflection light intensity of is generally low.

[0080]

According to the present invention, a light diffusing film having a high refractive index region having a columnar structure extending in the thickness direction of the film in a polymer film, and a light scattering layer for diffusing and transmitting light are provided. By stacking the layers, it is possible to improve the frontal luminance which can be obtained by the selective scattering characteristic and the visibility of a wide viewing angle which is obtained by the gentle scattering characteristic.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a light diffusing film having a high refractive index region having a cylindrical structure in a polymer film and a transmission / scattering characteristic diagram of vertically incident light.

FIG. 2 is a cross-sectional view of a light-scattering layer in which a polymer film is filled with a filler and a transmission-scattering characteristic diagram of vertically incident light.

FIG. 3 is a polymer film in which a light-diffusing film having a high refractive index region having a cylindrical structure, a light-scattering layer in which a filler is filled and a light-scattering pressure-sensitive adhesive layer in which a pressure-sensitive adhesive contains a filler are laminated. FIG. 3 is a cross-sectional view of an optical film and a transmission / scattering characteristic diagram of vertically incident light.

FIG. 4 is a schematic cross-sectional view of a liquid crystal display device.

FIG. 5 is a schematic cross-sectional view of another liquid crystal display device.

6A and 6B are a front view and a partial side view showing an example in which an optical film is used in a mobile phone.

FIG. 7 is a diagram illustrating a method of exposing a photosensitive polymer in Examples.

FIG. 8 is a diagram illustrating a method of evaluating reflection / scattering characteristics of an optical film in an example.

FIG. 9 is a diagram showing reflection-scattering characteristics of optical films in examples.

FIG. 10 is a diagram showing reflection-scattering characteristics of a diffusion film in a comparative example.

[Explanation of symbols]

1 ... Light diffusion film 2 ... Polymer film 3 ... Cylindrical high refractive index region 11 ... Light diffusion film 12, 14 ... Light scattering layer 13, 16 ... Optical film 15 ... Adhesive 21, 22 ... Glass substrate 23 ... Liquid crystal layer 24 ... Optical film 25 ... Reflector 26 ... Retardation plate 27 ... Polarizing film 31 ... Mobile phone 32 ... Display screen 33 ... Optical film 34 ... Viewer (eye) 35 ... Incident light 41 ... PET film 42 ... Photosensitive polymer layer 43 ... Mask 44 ... UV 51 ... Optical film 52 ... Reflector 53 ... Light source 54 ... Optical detector

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[Procedure amendment]

[Submission date] September 11, 2002 (2002.9.1)
1)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

(3) The optical laminate according to (1) or (2), wherein the difference in refractive index between the two phases having different refractive indexes of the light diffusion film is in the range of 0.005 to 0.2.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

(9) The optical laminate according to (8), wherein the light-scattering layer contains an adhesive as the matrix resin, and the light-scattering layer is laminated in direct contact with the light-diffusing film.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

As a curing agent for the pressure-sensitive adhesive, for example, a metal chelate-based, isocyanate-based, or epoxy-based cross-linking agent may be used alone or in combination of two or more. It is preferable that such an acrylic pressure-sensitive adhesive is blended so as to have a pressure-sensitive adhesive force in a range of 100 to 2,000 g / 25 mm in a state of containing a filler described later. Adhesion is 10
Poor environmental resistance is less than 0 g / 25 mm, in particular, there is a likelihood of delamination when high temperature and high humidity, on the contrary, 2,000 g /
If it exceeds 25 mm , there is a problem in that it cannot be reattached, or even if it is formed, the adhesive remains. The refractive index of the acrylic adhesive is in the range of 1.45 to 1.70, particularly 1.5 to 1.
A range of 1.65 is preferred.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

Further, a preferable example of the light scattering layer (light scattering film) formed by containing a filler in the resin matrix of the present invention is, for example, a planar film-like light scattering film made of a cellulose resin. In the film, the difference in refractive index from the resin is 0.05 or more and 0.5 or less, preferably 0.05 or more and 0.3 or less,
Further, there is a light scattering film containing a filler composed of organic or inorganic fine particles having a particle size of 5 nm or more and 50 μm or less. The reason why the cellulosic resin is used as the translucent resin is that birefringence is small and the film can be oxidized together with the polarizing plate to improve the adhesion. Further, the difference in refractive index of 0.05 or more is 0.
This is because if it is less than 05, a substantial scattering effect cannot be obtained, and in order to scatter, it is necessary to add a very large amount of filler. The difference in refractive index is 0.5 or less, preferably 0.3
The reason for setting the value below is that if it is larger than 0.5, it is necessary to reduce the content of the filler in the translucent resin, and a uniform light scattering layer cannot be obtained. The particle size is 5n
to m or more, as well as dispersion of the resin layer becomes difficult is less than 5 nm, homogeneous particulate material available is 5n
This is also because m is the limit. Further, the particle size of 50 μm or less means that when the particle size is larger than 50 μm, the filler protrudes and becomes uneven on the resin layer surface, the surface becomes white and the visibility of the screen is deteriorated, and the film becomes thick and a filler or resin which can be molded. This is because there are restrictions on

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0066

[Correction method] Change

[Correction content]

Acrylic adhesive 10 having a refractive index of 1.50
A filler was added to a base paint in which 1.5 parts of an isocyanate curing agent (D-90 Soken Chemical Co., Ltd.) was added to 0 parts, and the mixture was stirred with an agitator for 1 hour. The prepared pressure-sensitive adhesive was applied to a 38 μm release sheet (PET3801, manufactured by Lintec Co., Ltd.) so that the thickness after drying would be 25 μm.
38 μm on the light-scattering layer after drying to form the light-scattering layer
The release sheet (K-14, manufactured by Teijin Ltd.) was adhered to obtain a light-scattering pressure-sensitive adhesive sheet. Here, as the filler, silicon resin beads, a refractive index of 1.43, and an average particle diameter of 1.
The content was 0 μm, the content was 3%, and the HAZE value of the light scattering layer was 25. The light-scattering pressure-sensitive adhesive was attached to the light-diffusing film to obtain the optical film of the present invention.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0072

[Correction method] Change

[Correction content]

Example 3 For 100 parts of an acrylic adhesive having a refractive index of 1.50,
Isocyanate curing agent (D-90 manufactured by Soken Chemical Co., Ltd.) 1.5 parts the added base coating, a filler, A
A paint was prepared by stirring for 1 hour with a jetter . Each coating material was applied to a 38 μm release sheet (PET3801, manufactured by Lintec Co., Ltd.) with a comma coater to give a thickness of 25 μm.
And then dried to form a light-scattering layer,
A 38 μm release sheet (K-14, manufactured by Teijin Ltd.) was attached onto the light scattering layer to obtain a light scattering pressure-sensitive adhesive sheet. Here, the filler was an epoxy resin filler, the refractive index was 1.59, the average particle size was 5.5 μm, and the content was 3%, and the haze value of the light scattering layer was 30. This sheet was attached to a light diffusion film to obtain the optical film of the present invention.

Continued front page    F-term (reference) 2H042 BA02 BA04 BA10 BA12 BA20                 2H091 FA31X FB02 FB12 FD06                       GA17 LA17 LA19                 2K009 AA12 CC03 CC09 DD01                 4F100 AK25A AK42C AK52A AR00A                       AR00B BA03 BA07 BA10A                       DD40B DE04A EJ54B GB41                       HB40B JN08A JN30 JN30B

Claims (12)

[Claims] 1. A light-diffusing film comprising two regions having different refractive indexes for scattering and transmitting light, one phase having a large refractive index having a columnar structure extending in the thickness direction of the film, and a light-diffusing film. And a light-scattering layer that scatters and transmits. 2. The optical laminate according to claim 1, wherein the axes of the columnar structures extending in the thickness direction of the light diffusion film are parallel to each other, and the axes are in the normal direction of the film. body. 3. The optical layered body according to claim 1, wherein the refractive index difference of at least two phases having different refractive indexes of the light diffusion film is in the range of 0.005 to 0.2. 4. The optical laminate according to claim 1, wherein the light diffusion film is manufactured from a polymer material having radiation sensitivity. 5. The optical layered body according to claim 1, wherein the light scattering layer contains a matrix resin and a filler. 6. The optical layered body according to claim 5, wherein the difference in refractive index between the matrix resin and the filler of the light scattering layer is 0.05 to 0.5. 7. The optical laminate according to claim 5, wherein the filler of the light scattering layer is spherical. 8. The optical layered body according to claim 5, wherein the matrix resin of the light scattering layer is an adhesive. 9. The optical laminate according to claim 8, wherein the light diffusion layer contains an adhesive as the matrix resin, and the light scattering layer is laminated in contact with the light diffusion film. 10. The optical laminate according to claim 1, wherein the light diffusion film and the light scattering layer are attached with an adhesive. 11. The optical layered body according to claim 1, wherein the optical layered body is an optical film in which the light diffusion film and the light scattering layer are integrated. 12. The optical layered body according to claim 1, wherein one or more other layers and / or films are interposed between the light diffusion film and the light scattering layer.