Patent Application
20070091437
The present invention relates to a liquid crystal display apparatus used as a display of a personal computer or the like, and to an optical member and reflective polarizer which are suitably applicable to such liquid crystal display apparatus.
A liquid crystal display apparatus generally used at present includes a panel of a structure in which a nematic liquid crystal is provided between two transparent substrates to form a liquid crystal cell and in which polarizers are located on both sides of this cell. This panel is combined with an LSI for driving and a backlight to constitute a liquid crystal display apparatus.
Incidentally, the liquid crystal display apparatus of this type does not always have a high efficiency of utilization of light emitted from the backlight because 50% or more of light emitted from the backlight 40 is absorbed by the back polarizer 21. As shown in
The reflective polarizer 45 reflects polarized light of a certain kind of polarization and transmits polarized light of another kind of polarization opposite thereto. The alignment therein is performed such that the light transmitted by the reflective polarizer 45 passes as linearly polarized light through the polarizer (normally, absorptive polarizer) 21. Then the polarizer 21 absorbs polarized light if only the polarizer 21 is used without the reflective polarizer 45, but the reflective polarizer 45 reflects polarized light to return the polarized light toward the backlight 40, as shown in
The following documents for such reflective polarizers are known, which are listed as examples of the reflective polarizers: Japanese Patent Applications Laid-Open No. 6-281814 (Patent Document 1) and Laid-Open No. 8-271731 (Patent Document 2) describe reflective polarizers including a combination of a cholesteric liquid crystal layer with a quarter wave plate; Published Japanese translations of PCT applications No. P9-506837A (WO95/17303, Patent Document 3) and No. P10-511322A (WO96/19347, Patent Document 4) describe reflective polarizers including multilayered films of birefringent layers and isotropic layers; Published Japanese translation of a PCT application No. P2000-506990A (W097/32224, Patent Document 5) describe reflective polarizers including isotropic particle phases are dispersed in a birefringent continuous medium.
A reflective polarizer including a combination of a cholesteric liquid crystal layer with a quarter wave plate reflects left-handed (or right-handed) circularly polarized light, and transmits right-handed (or left-handed) circularly polarized light of a wavelength corresponding to the helical pitch of the cholesteric liquid crystal to convert it into linearly polarized light by use of the quarter wave plate. It is, however, difficult for this reflective polarizer to convert the right-handed (or left-handed) circularly polarized light from the cholesteric liquid crystal layer into linearly polarized light by the quarter wave plate of a single layer over the wavelength range of visible light. In order to overcome this difficultly, it is necessary to arrange a plurality of quarter wave plates to form the stacked quarter wave plates. Production steps for forming a stack of quarter wave plates become complicated and there will arise a problem that delamination of the quarter wave plates can occur.
A reflective polarizer of multilayered films that includes birefringent layers and isotropic layers alternately arranged requires formation of an alternate stack structure of several hundred layers and thus requires large-scale production facilities. The lamination of different materials can also pose a problem that delamination of the layers is likely to occur.
It is relatively easy to produce a reflective polarizer with isotropic particle phases in a birefringent continuous medium and the reflective polarizer is less likely to cause delamination of the layers. However, if the continuous medium is made of a uniaxially oriented substance demonstrating significant birefringence, increase in a volume fraction of the dispersed phases may result in failure in maintaining its film shape because of a reduction of its strength. For this reason, the volume fraction of the dispersed phases needs to be kept low, and it will pose a problem that it is difficult to enhance the polarization split efficiency.
Patent Document 1: Japanese Patent Application Laid-Open No. H06-281814
Patent Document 2: Japanese Patent Application Laid-Open No. H08-271731
Patent Document 3: Published Japanese translation of PCT application No. H09-506837A
Patent Document 4: Published Japanese translation of PCT application No. H10-511322A
Patent Document 5: Published Japanese translation of PCT application No. P2000-506990A
Problem to be Solved by the Invention
In view of the foregoing problems, an object of the present invention is to provide a reflective polarizer capable of enhancing the efficiency of utilization of light in a liquid crystal display apparatus, relatively easy to produce, and unlikely to cause the problems such as the delamination.
Another object of the present invention is to provide an optical member capable of enhancing the efficiency of utilization of light in a liquid crystal display apparatus, based on a configuration wherein the reflective polarizer is laminated with an optical layer having another optical function.
Still another object of the present invention is to provide a liquid crystal display apparatus with an enhanced efficiency of utilization of light from a backlight, using the optical member with this reflective polarizer laminated.
Means for Solving the Problem
According to the present invention, a reflective polarizer comprises plural birefringent bodies of polygonal prisms or circular cylinders a shape of a cross section of which perpendicular to a major axis direction is polygonal or substantially circular, which has an aspect ratio of not less than 2, and which has a refractive index difference of not less than 0.05 between a refractive index component in a major axis direction and a refractive index component in a minor axis direction. The plural birefringent bodies are dispersedly arranged in a support medium substantially in one direction, and where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies is substantially circular, any one of the plural birefringent bodies, when viewed on the cross section, is in contact on a side face of a circular cylinder with each of at least two other birefringent bodies in contact on a side face of a cylinder with each other.
In this reflective polarizer, the birefringent bodies dispersedly arranged in the support medium can be made of fibers a shape of a cross section of which perpendicular to the major axis direction thereof is polygonal. The fibers are preferably those having a sectional shape of a triangle, lengths of at least two sides of which are substantially equal to each other, and the fibers are so arranged that the fibers are substantially parallel in a plane of the reflective polarizer and that apexes of sectional triangles of adjacent fibers are in contact with each other; in a cross section in a thickness direction of the reflective polarizer perpendicular to the long axis of the fibers, the support medium surrounded by fibers of sectional triangles with their apexes in contact with each other is preferably of a hexagonal shape. This hexagonal shape can be substantially a regular hexagon. In this case, the above fibers dispersedly arranged in the support medium have the sectional shape of substantially a regular triangle, they are so arranged that they are substantially parallel in a plane of the reflective polarizer and that apexes of sectional regular triangles of adjacent fibers are in contact with each other, and in a cross section in the thickness direction of the reflective polarizer perpendicular to the long axis of the fibers, the support medium surrounded by fibers of sectional triangles with apexes in contact with each other is in a state of substantially a regular hexagon.
Another effective configuration is as follows: the above fibers dispersedly arranged in the support medium have the sectional shape of a triangle, lengths of at least two sides of which are substantially equal to each other. They are so arranged that they are substantially parallel in a plane of the reflective polarizer and that apexes of sectional triangles of adjacent fibers are in contact with each other, and in a cross section in the thickness direction of the reflective polarizer perpendicular to the long axis of the fibers, the support medium surrounded by fibers of sectional triangles with apexes in contact with each other is of a triangle. Lengths of two sides of the triangle are substantially equal to each other.
Furthermore, another effective configuration is as follows: the foregoing fibers dispersedly arranged in the support medium have a sectional shape of a quadrangle, lengths of four sides of which are substantially equal to each other. They are so arranged that they are substantially parallel in a plane of the reflective polarizer and that apexes of sectional quadrangles of adjacent fibers are in contact with each other, and in a cross section in the thickness direction of the reflective polarizer perpendicular to the long axis of the fibers, the support medium surrounded by fibers of sectional quadrangles with apexes in contact with each other is of a quadrangle. Lengths of four sides of the quadrangle are substantially equal to each other.
In this reflective polarizer, where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies is substantially circular, a triangle defined by connecting centers of three circles in direct contact in the cross section perpendicular to the long axis direction of the birefringent bodies preferably has at least two sides which are substantially equal to each other. Among others, a preferable configuration is as follows: a triangle defined by connecting centers of three circles in direct contact in the cross section perpendicular to the long axis direction of the birefringent bodies has three sides which are substantially equal to each other. In this configuration, when the centers of the respective circles are connected in the cross section perpendicular to the long axis direction of three birefringent bodies in direct contact, the three sides of the triangle are substantially equal to each other, i.e., substantially a regular triangle, and this means that the diameters of the respective circles are substantially equal. Among others, in a preferred structure, circular cylinders, diameters of circles of which are substantially equal to each other, are close-packed. In another expression, the plural birefringent bodies in the preferred configuration are circular cylinders, the diameters of the circles of which are substantially equal to each other in the cross section perpendicular to the long axis direction, and in this cross section some of the birefringent bodies located in the inside of the outermost is in contact on a side face of a circular cylinder with other six birefringent bodies of circular cylinders. Each birefringent body in the reflective polarizer can be made of a fiber.
In the reflective polarizer in each of the above-described configurations, it is preferable that either one of the refractive index component of the birefringent bodies in the long axis direction and the refractive index component in the short axis direction is substantially equal to the refractive index of the support medium.
The reflective polarizer in each of these configurations can be provided on an optical layer with another optical function to form a laminated optical member. The optical layer to be laminated is, for example, an absorptive polarizer or a retardation plate. Furthermore, it is also possible to adopt a configuration in which an absorptive polarizer is provided on one surface of the reflective polarizer and a retardation plate is provided on the other surface.
The laminated optical member in each of these configurations can be combined with a liquid crystal cell to form a liquid crystal display apparatus. Therefore, the present invention also provides the liquid crystal display apparatus in which the laminated optical member in any one of the above configurations, which is a laminate of the reflective polarizer and another optical layer, is placed on the liquid crystal cell.
Effect of the Invention
The reflective polarizer of the present invention has a structure in which the birefringent bodies are dispersed and oriented substantially in one direction, by the simple method, and is resistant to delamination because the interface between different materials is not a simple plane. Since the support medium for supporting the birefringent bodies is made of the isotropic substance, the reduction of its strength is relatively small with increase in the volume fraction of the birefringent bodies, and it is thus easy to increase the volume fraction of the birefringent bodies. Furthermore, by locating this reflective polarizer on the opposite side to an observer of the liquid crystal panel with the absorptive polarizer, it becomes feasible to provide the liquid crystal display apparatus capable of achieving high luminance and low power consumption because the efficiency of utilization of light is increased.
10 liquid crystal cell;
11, 12 transparent substrate;
14, 15 transparent electrode;
17 liquid crystal;
21, 22 absorptive polarizer;
25 retardation plate;
30 reflective polarizer;
31, 32 birefringent body;
33 support medium;
35 laminated optical member;
40 backlight device;
45 reflective polarizer (conventional);
50 liquid crystal display apparatus.
For describing the best mode for the present invention, the following embodiments will be separately described a shape of the cross section perpendicular to the long axis direction of the birefringent bodies dispersedly arranged in the support medium is polygonal; and the shape of the section is substantially circular. In subsequent embodiments, the two cases will be described together.
<The case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies dispersedly arranged in the support medium is polygonal>
In an embodiment of the present invention, the birefringent bodies are dispersedly arranged in the support medium to form the reflective polarizer. Each birefringent body has the sectional shape of a polygon and the aspect ratio of not less than 2. Here the aspect ratio is preferably not less than 5 and more preferably not less than 10. The aspect ratio is defined as a ratio of a length to a short-axis diameter, but, since the embodiment of the present invention uses the birefringent bodies each having the sectional shape of the polygon, the short-axis diameter is defined as a diameter of a circumscribed circle to the polygon. When each birefringent body has the cross section of the polygonal shape and is elongate or longitudinal and when the refractive index is properly selected, the polarizer reflects light linearly polarized in the direction parallel to the elongate direction and transmits light linearly polarized in the direction perpendicular to the major direction.
Specific examples of the sectional structure of the reflective polarizer according to the embodiment of the present invention are presented in FIGS. 3 to 6. These examples schematically show the cross section taken in the direction of thickness, parallel to the transmission axis indicated by an outline two-headed arrow, of the reflective polarizer. In the reflective polarizer 30 of the present invention, as shown in these drawings, birefringent bodies 31 with the sectional shape of a polygon (blackened portions) are dispersedly arranged in the support medium 33 (white portions).
In FIGS. 3 to 6, the thickness of the reflective polarizer 30 is indicated by symbol “t”. The examples shown in
In the present specification, the triangle the lengths of at least two sides of which are substantially equal is a conception encompassing substantially isosceles triangles and substantially regular triangles, and the quadrangle the lengths of the four sides of which are substantially equal is a conception encompassing substantially rhomboids and substantially squares. Furthermore, the term “substantially equal” for two sides, three sides, or four sides encompasses cases where the lengths of the sides are completely equal, and also means that some variation is allowed from approximately +10% to approximately −10% (approximately ±10%) of the length of one side to another side. Yet furthermore, the term “substantially” in “substantially isosceles triangles,” “substantially regular triangles,” “substantially regular hexagons,” “substantially rhomboids,” and “substantially squares” means that some variation is allowed from approximately +10° to approximately −10° (approximately ±10°) for angles of apexes primarily in the case of the polygonal shapes (in the case of an isosceles triangle, two angles that should be originally equal). The polygonal shapes are based on the assumption that each side of the relevant polygon is a straight line, but in manufactured fibers, each side become curved to some extent. Therefore, this shade of meaning is expressed by the term “substantially.” In addition, in the cases where the term “substantially” is given for expression of angles, it means that some variation is allowed from approximately +10° to approximately −10° (approximately ±10°) around an angle expressed.
The birefringent bodies 31 can be constructed of fibers. The support medium 33 may be made of material that is transparent and demonstrates good adhesion to the birefringent bodies 31. The birefringent bodies 31 have the sectional shape of a polygon and among others, they preferably have the sectional shape of a triangle with at least two sides thereof substantially equal to each other, a quadrangle with the four sides thereof substantially equal to each other, or substantially a regular polygon and preferably have the sectional shape of substantially a regular triangle. The length of each side of the polygon needs to be larger than the wavelengths of visible light and is preferably not less than 1 micrometer (μm) and more preferably not less than 5 micrometers (μm). If the length of each side of the polygon is less than 1 micrometer (μm), good polarization separation performance will not be achieved. The birefringent bodies 31 need to have the refractive index difference of not less than 0.05 between the refractive index in the long axis direction (the direction of the length of the birefringent bodies) and the refractive index in the short axis direction (the direction of the diameter of the polygon), and this refractive index difference is preferably not less than 0.1 and more preferably not less than 0.2.
In the embodiment of the present invention, the birefringent bodies 31 are dispersedly oriented in the support medium 33 to form the reflective polarizer 30 of a structure and, in one preferable structure of the birefringent bodies 31, are substantially oriented in one direction and in more preferably, the birefringent bodies 31 are closely packed. Among others, in a preferred configuration, the birefringent bodies 31 having the sectional shape of a regular triangle are so arranged that they are substantially parallel in the plane and that apexes of sectional regular triangles of adjacent birefringent bodies 31 are in contact with each other, as shown in
If parallel light is normally incident to the plane of the reflective polarizer 30 and the diameter is at a level that does not need for consideration to scattering factors, relatively high polarization separation performance can be obtained in the flowing cases even when the number of layers of the birefringent bodies 31 in the thickness direction of the reflective polarizer 30 may be one; the birefringent bodies 31 having the sectional shape of an isosceles triangle or a regular triangle are arranged in the thickness direction so as to alternately stack the triangles of two types, one orientation of which is different from the other, such that the birefringent bodies 31 are substantially parallel in the plane and that apexes of sectional triangles of adjacent birefringent bodies 31 are in contact with each other, as shown in
<The case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies dispersedly arranged in the support medium is substantially circular>
In the embodiment of the present invention, the birefringent bodies are dispersedly arranged in the support medium to form the reflective polarizer. The birefringent bodies have longitudinal shapes, the shape of the cross section perpendicular to the long axis direction thereof is substantially a circle, and the aspect ratio is not less than 2. Here the aspect ratio is preferably not less than 5 and more preferably not less than 10. The aspect ratio is represented by a ratio of a length to a short-axis diameter. Since the present invention adopts the birefringent bodies of cylinders having the sectional shape of substantially a circle, the diameter of the circle corresponds to the short-axis diameter. If a polarizer is constructed using the birefringent bodies in the shape of the longitudinal cylinder having the cross section of substantially a circle, the birefringent bodies are closely packed and the refractive index of the birefringent bodies is properly selected, then this polarizer reflects light linearly polarized in the direction parallel to the longitudinal direction and transmits light linearly polarized in the direction perpendicular to the longitudinal direction.
Specific examples of the sectional structure of the reflective polarizer according to the embodiment of the present invention are shown in
In the embodiment of the present invention, the birefringent bodies 31, 32 have substantially circular shapes in the cross section perpendicular to the long axis direction. Here the term “substantially circular shape” means that the foregoing ellipticity can be tolerated within approximately 0.9-1.1 (1±10.1) because the birefringent bodies can be slightly elliptic because of its manufacturing variation, and although the term is thus used in such cases, the tern indicates preferably a perfect circle, i.e., the ellipticity defined by a ratio of a major axis of an ellipse to a minor axis thereof is preferably 1.
The birefringent bodies 31, 32 are dispersedly arranged in a substantially identical direction in the support medium 33. The term “substantially identical direction” means that some variation is allowed in the angular range of approximately −10° to +10° both inclusive (±10°) and preferably the birefringent bodies are arranged in a perfectly identical direction. In addition, the phrase “lengths are substantially equal” means that some variation is allowed from approximately +10% to approximately −10% (±10%), and preferably they are perfectly equal.
Furthermore, in the embodiment of the present invention, a plurality of birefringent bodies having the sectional shape of substantially a circle perpendicular to the long axis direction are dispersedly arranged so that, in a cross section thereof, the side face of the circular cylinder (the circumference in the sectional view) of any one of the birefringent bodies is in contact with those of at least two other birefringent bodies that are in contact on the side face of the circular cylinder thereof (the circumference in the sectional view) with each other. When attention is focused to a certain circle in the cross section perpendicular to the long axis direction of the birefringent bodies, the state in which the circle is in contact on the side face of the circular cylinder (the circumference in the sectional view) with each of at least two other birefringent bodies in contact on the side face of the circular cylinder (the circumference in the sectional view) with each other corresponds to a state in which, concerning the relevant circle and two other circles in contact therewith, a length of a side of a triangle composed of three apexes on the centers of these circles is the sum of radii of respective circles centered on a start point and an end point of the side. This will be described on the basis of
Referring to part (a) in
Referring to part (b) in
It is understood from the above description that a variety of modifications can be made, in addition to the examples shown in
A triangle formed by connecting centers of three circles that are in direct contact with each other in the cross section perpendicular to the long axis direction of the birefringent bodies is preferably a triangle at least two sides of which are substantially equal, and among others, preferably, this triangle has three sides which are substantially equal to each other. The birefringent bodies in the thickness direction of the reflective polarizer is preferably stacked in an arrangement in which a plurality of layers are stacked in contact successively, and more preferably is stacked in an arrangement in which the birefringent bodies constituted by circular cylinders each having a substantially equal diameter are closely packed. In the more preferred configuration, accordingly, the plurality of birefringent bodies 31 are formed as the circular cylinders in which circles in the cross section perpendicular to the long axis direction have diameters substantially equal to each other, and, as shown in
The birefringent bodies 31, 32 as shown in
As shown in
In the reflective polarizer 30 constructed as shown in
In principle, although a variety of substances demonstrating birefringence as the birefringent bodies 31, 32 can be used for the present invention, in terms of stability, endurance, etc. of orientation and sectional shape, the birefringent bodies 31, 32 are preferably solid.
Furthermore, the birefringent bodies 31, 32 can be made of a substance in the sectional shape of a polygon and in an aspect ratio of not less than 2. Among substances meeting this condition, the most preferred is continuous fibers for the birefringent bodies 31, 32 because they can be readily highly oriented in the support medium 33 and effectively demonstrate birefringence.
The fibers used for the birefringent bodies 31, 32 will be described below. Examples of such fibers are listed as follows: polyolefin-vinyl fibers such as polyethylene, polytetrafluoroethylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, polyacrylonitrile, and poly(4-methyl-1-pentene); aliphatic polyamide fibers such as nylon 6, nylon 66, and nylon 46; aromatic polyamide fibers (aramid fibers) such as poly(m-phenylene isophthal amide) and poly(p-phenylene terephthal amide); polyester fibers such as polyethylene terephthalate, polyethylene naphthalate, and poly-ε-caprolactone; aromatic liquid crystal polyester fibers typified by “VECTRA” commercially available from Polyplastics Co., Ltd., and “Sumika Super” commercially available from Sumitomo Chemical Co., Ltd.; heteroatom-containing fibers such as poly(p-phenylene-benzo-bis-oxazole), poly(p-phenylene-benzo-bis-thiazole), polybenzimidazole, polyphenylene sulfide, polysulfone, poly(ether sulfone), and poly(ether ether ketone); polyimide fibers such as polypyromellitic imide; cellulose fibers such as rayon; acrylic fibers such as poly(methyl methacrylate); polycarbonate fibers; urethane fibers, and so on. Among these, it is particularly preferable to use as the birefringent bodies, fibers that have an aromatic ring such as a benzene ring or a naphthalene ring, and that have little or no absorption in the visible light region.
In order to enhance the adhesion to the support medium, the fiber surface may be subjected to any of various adhesion-enhancing treatments such as the corona treatment. Furthermore, useful techniques for enhancing the birefringence of fibers are to add whiskers of low-molecular-weight liquid crystal compounds, fillers with shape anisotropy, or the like, to adopt the SAM fiber (Super-summational, Axially arranged & Mutual-polymers-configuration-type composite fiber) of a multifilament type
Examples of the low-molecular-weight liquid crystal compounds to be added to the fibers in order to enhance the birefringence include compounds having as a mesogen (a core unit to develop the liquid crystal property in a molecular structure) a compound selected from biphenyl-based, phenyl benzoate-based, cyclohexyl benzene-based, azoxybenzene-based, azobenzene-based, azomethine-based, terphenyl-based, biphenyl benzoate-based, cyclohexyl biphenyl-based, phenyl pyrimidine-based, cyclohexyl pyrimidine-based, and cholesterol-based compounds. These low-molecular-weight liquid crystal compounds may be dissolved in the fibers or may exist as domains as long as they are oriented in the long axis direction of the fibers. However, where they exist as domains, the diameter of the domains is preferably not more than 0.2 micrometer (0.2 μm). The diameters of the domains larger than 0.2 micrometer (0.2 μm) are not preferred because they scatter linearly polarized light vibrating in the direction perpendicular to the long axis of fibers.
Examples of the whiskers to be added to the fibers in order to enhance the birefringence include sapphire, silicon carbide, boron carbide, silicon nitride, boron nitride, aluminum borate, graphite, potassium titanate, polyoxymethylene, poly(p-oxybenzoyl), poly(2-oxy-6-naphthoyl), and so on. These whiskers are preferably those having the average diameter of the cross section thereof in the range of 0.05 to 0.2 micrometer (0.05-0.2 μ). The average diameters larger than 0.2 micrometer (0.2 μm) are not preferred because they scatter linearly polarized light vibrating in the direction perpendicular to the long axis of the fibers, just as in the case of the low-molecular-weight liquid crystal compounds, and because the whiskers can form projections on the surface of the fibers.
When the SAM fibers are used as the birefringent bodies 31, 32, the SAM fibers are in a state in which islands are dispersedly arranged in a sea. In this case, either one of the refractive index in the long axis direction and the refractive index in the short axis direction of the islands is preferably made substantially coincident with the refractive index of the sea. In this case, the diameter of the islands is also preferably not more than 0.2 micrometer (0.2 μm). Preferably, two or more islands exist in the sea and, more preferably, four or more islands exist in the sea. A filler with shape anisotropy, such as a low-molecular-weight liquid crystal or a whisker, may be further added to the islands.
In the embodiment of the present invention as described above, the birefringent bodies 31 having the polygonal cross section and the aspect ratio of not less than 2 or the birefringent bodies 31, 32 having the sectional shape of substantially a circle and the aspect ratio of not less than 2, e.g., fibers, are dispersedly arranged in the support medium 33. The support medium 33 functions to fix the birefringent bodies 31, 32. The support medium may be any material that has little absorption or no absorption in the visible light region and that demonstrates good adhesion to the fibers. For example, the support medium can be a transparent resin. Specific examples of the transparent resin include acrylic resins such as poly (methyl methacrylate); polyolefins such as polyethylene; polyesters such as polyethylene terephthalate; polyethers such as polyphenylene oxide; vinyl resins such as polyvinyl alcohol; polyurethane; polyamide; polyimide; epoxy resin; copolymers using two or more monomers constituting the foregoing polymers; non-birefringent polymer blends such as a mixture of poly(methyl methacrylate) and polyvinyl chloride at a weight ratio of 82:18, a mixture of poly(methyl methacrylate) and polyphenylene oxide at a weight ratio of 65:35, a mixture of polystyrene and polyphenylene oxide at a weight ratio of 71:29, and a mixture of a styrene-maleic anhydride copolymer and polycarbonate at a weight ratio of 77:23; and so on, but the support medium is not limited to these examples. These support media may contain an additive such as an antioxidant, light stabilizer, heat stabilizer, lubricant, dispersant, ultraviolet absorber, white pigment, or fluorescent whitener as long as the aforementioned properties are not adversely affected.
The birefringent bodies 31, 32 described above are dispersedly arranged in the support medium 33 to form the reflective polarizer 30. The difference between the refractive index in the long axis direction or in the short axis direction of the birefringent bodies 31, 32 and the refractive index of the support medium 33 is preferably not less than 0.05, more preferably not less than 0.1, and particularly preferably not less than 0.2. As this refractive index difference becomes larger, incident light can be efficiently reflected backward and the thickness of the polarizer can be made smaller. In the case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies is polygonal, proportions of the fibers constituting the birefringent bodies 31, 32 and the substance constituting the support medium 33 is determined such that the fibers can be effectively fixed in the support medium. In the case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies is substantially circular, the proportions defined above may be determined if the fibers are effectively fixed in the support medium and if the birefringent bodies satisfy the condition that any one birefringent body, when viewed on the cross section perpendicular to the long axis direction of the birefringent body, is in contact on the side face of the circular cylinder with each of at least two other birefringent bodies in contact on the side face of the circular cylinder with each other. However, as shown in
(where symbol “sqrt” is a square root).
There are no particular restrictions on the thickness “t” of the reflective polarizer 30 in the embodiment of the present invention. However, if the reflective polarizer is too thin, it will fail to achieve the polarization separation performance. On the other hand, if the reflective polarizer is too thick, it will increase the quantity of light absorbed thereby though it is reflective type and increase of material cost. Therefore, the thickness is normally in the appropriate range of 1 to 1000 micrometers (μm), preferably not less than 5 micrometers (μm), more preferably not less than 10 micrometers (μm), and preferably not more than 500 micrometers (μm), more preferably not more than 200 micrometers (μm).
The reflective polarizer of the embodiment of the present invention can be produced, for example, through three steps of: spinning and drawing fibers as birefringent bodies; preparing a nonwoven fabric in which these fibers are arranged in one direction; and impregnating this nonwoven fabric with the support medium to fix it. There are no particular restrictions on the spinning-drawing step of fibers as birefringent bodies and the production step of the nonwoven fabric, and they can be performed by well-known methods. The step of impregnating the nonwoven fabric with the support medium to fix it can be implemented by the following: a method of immersing the nonwoven fabric in a monomer and/or an oligomer as a precursor of the support medium and thereafter polymerizing the precursor of the support medium by light and/or heat; a method of immersing the nonwoven fabric in a polymer solution of the support medium and thereafter eliminating a solvent; a method of preparing the support medium in the form of fine powder, impregnating the nonwoven fabric with the fine powder, and thereafter melting the fine powder; and so on.
Furthermore, an effective alternative is a method of producing the reflective polarizer of the embodiment of the present invention by the melt extrusion method. Specifically, in the case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies dispersedly arranged in the support medium is polygonal, it is possible to adopt a profile extrusion method of extruding the resin for the birefringent bodies in the polygonal shape, by use of an extruder discharge port partitioned to form a number of dies, from every other die thereof, and extruding the resin for the support medium from other dies provided between the dies for the birefringent bodies. In the case where the shape of the cross section perpendicular to the long axis direction of the birefringent bodies dispersedly arranged in the support medium is substantially circular, it is possible to adopt a profile extrusion method of extruding the resin for the birefringent bodies in a round rod shape, by use of an extruder discharge port partitioned to form a number of dies continuous in the cross section, from a part of the dies thereof, and extruding the resin forming the support medium, from other dies provided between the dies for the birefringent bodies. In these cases, the extruder and dies can be designed so as to form the aforementioned dispersedly arranged structure by extruding the different types of molten resins alternately in the predetermined shapes from the dies of the extruder.
In use of the reflective polarizer of the embodiment according to the present invention, an optical layer with another optical function can be formed on at least one surface of the reflective polarizer to form a laminated optical member. For the purpose of forming the laminated optical member, the optical layer to be formed on the reflective polarizer of the embodiment of the present invention can be, for example, an absorptive polarizer, a retardation plate, or the like.
Particularly, when an absorptive polarizer is laminated on the reflective polarizer of the embodiment of the present invention, the laminated optical member can be used as a luminance-improving film intended for improving the luminance in the liquid crystal display apparatus or the like. Specifically, when the absorptive polarizer and the reflective polarizer of the embodiment of the present invention are so arranged that the transmission axes of them are substantially parallel and that the reflective polarizer is located on the backlight side while the absorptive polarizer on the liquid crystal cell side, linearly polarized light is transmitted by the reflective polarizer and the transmitted light is emitted toward the liquid crystal cell while its direction is aligned in the absorptive polarizer; on the other hand, linearly polarized light is reflected on the reflective polarizer and the reflected light returns to the backlight side to be reused. An example of the absorptive polarizer is one formed as follows: a dichroic dye such as iodine or a dyestuff is made to be adsorbed on uniaxially oriented polyvinyl alcohol, it is cross-linked with boric acid to form a polarizer, and a transparent film of triacetylcellulose or the like is bonded to at least one surface of the polarizer.
Further effective utilization of reflected light can be achieved by a retardation plate laminated on the reflective polarizer of the embodiment of the present invention. Specifically, the reflective polarizer reflects linearly polarized light and the reflected light is converted into circularly polarized light by the retardation plate and the circularly polarized light is fed back to the backlight. Polarization inversion occurs upon reflection on a reflecting plate of the backlight to produce light of the other circularly polarization reverse to that of light before reflection. After this light passes again through the retardation plate, it turns into light linearly polarized in the direction perpendicular to the linearly polarized original light, and the resultant light linearly polarized passes through the reflective polarizer. This achieves effective utilization of light. In this case, a quarter wave plate is advantageously used as the retardation plate. When the quarter wave plate is laminated on the reflective polarizer, they may be arranged so that the transmission axis of the reflective polarizer intersects at the angle of 45° or at the angle of 135° with the retardation axis of the quarter wave plate. Examples of the retardation plate are listed below: a birefringent film constituted by a drawn film of various plastics such as polycarbonate and cyclic polyolefins; a film in which a discotic liquid crystal or nematic liquid crystal is oriented and fixed; a plate in which the foregoing liquid crystal layer is formed a film base; and so on.
As shown in
For producing the laminated optical member, an adhesive is used to integrate the reflective polarizer with the optical layer such as the absorptive polarizer or the retardation plate, and there are no particular restrictions on the adhesive used for that purpose as long as an adhesive layer is formed well. In terms of simplicity of the bonding or prevention of occurrence of optical distortion, it is preferable to use a tackiness agent (also referred to as “a pressure-sensitive adhesive”). The tackiness agent can contain a base polymer such as an acrylic polymer, silicone polymer, polyester, polyurethane, or polyether.
Among others, it is preferable to use an agent that satisfied the following: it is excellent in optical transparency; it has moderate wettability and cohesion; it is also excellent in adhesion to the base, that has satisfactory weather resistance and heat resistance; and it is free of the delamination problem such as a rise or peeling under heat and humidity conditions, like acrylic tackiness agents. A useful base polymer for the acrylic tackiness agents is, for example, an acrylic copolymer with the weight-average molecular weight of not less than 100,000 obtained by blending an alkyl ester of (meth)acrylic acid having an alkyl group with 20 or less carbons, such as a methyl group, an ethyl group, or a butyl group, and a functionalized acrylic monomer such as (meth)acrylic acid or hydroxyethyl (meth)acrylate so as to achieve the glass transition temperature, preferably, of not more than 25° C., more preferably not more than 0° C., and polymerizing them.
The tackiness agent layer can be formed on the polarizer, for example, by the following methods: a method of dissolving or dispersing a tackiness agent composition in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10-40% by weight and directly applying it onto the polarizer to form the tackiness agent layer; a method of preliminarily forming the tackiness agent layer on a protect film and transferring it onto the polarizer to form the tackiness agent layer thereon; and so on. The thickness of the tackiness agent layer is optionally determined according to the adhesion thereof or the like, and is normally in the range of 1 to 50 micrometers (μm).
The tackiness agent layer may contain filler such as glass fiber, glass beads, resin beads, metal powder, or other inorganic powder, a pigment, a colorant, an antioxidant, or an ultraviolet absorber. Examples of the ultraviolet absorber include salicylic ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and so on.
The laminated optical member, in the form similar to that shown in
The liquid crystal cell to be used in the liquid crystal display apparatus can be any liquid crystal cell; for example, the liquid crystal display apparatus can be formed by using a variety of liquid crystal cells such as active matrix drive type cells typified by the thin film transistor type and simple matrix drive type cells typified by the super-twisted nematic type.
The reflective polarizer of the embodiment of the present invention, and the laminated optical member provided therewith can be suitably applied to display screens using the liquid crystal cell, such as personal computers, word processors, engineering workstations, personal digital assistants, navigation systems, liquid crystal TV monitors, and video players, and realize an improvement in luminance and a reduction in power consumption.
Calculation examples by simulation will be shown below: a case where triangular prisms with the sectional shape of a regular triangle are uniformly dispersed in the support medium; a case where triangular prisms with the sectional shape of an isosceles triangle are uniformly dispersed in the support medium; a case where rectangular prisms with the sectional shape of a square are uniformly dispersed in the support medium; a case where circular cylinders with the sectional shape of a circle are closely dispersed in the support medium; and a case where circular cylinders with the sectional shape of a circle are relatively sparsely dispersed in the support medium. The calculation for the degree of polarization hereinafter was performed using ray-tracing software “Trace Pro 2.3.4” (available from Lambda Research Corp.).
This example shows optical characteristics in the case where six triangular prisms with the sectional shape of a regular triangle are in contact with each other at the apexes of the respective sectional regular triangles to form a regular hexagonal prism, i.e., where triangular prisms are uniformly dispersed in the support medium in the form of the Star of David. The orthogonal coordinate system of the right hand system to express positions in the simulation space is defined as (x,y,z) and the schematic view of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the range of coordinate x of −1 micrometer to 1 micrometer both inclusive, the range of coordinate y of −10 micrometers to 10 micrometers both inclusive, and the range of coordinate z of 0 micrometer to 216 micrometers both inclusive. That is, as shown in part (a) in
−1 μm≦x≦1 μm,
−10 μm≦y≦10 μm, and
0≦z≦216 μm.
Two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be both perfectly reflecting surfaces. On the other hand, a light source is defined as a line segment at x=z=0 and in parallel to the y-axis in the range of −10 micrometers (μm) to 10 micrometers (μm) both inclusive, and generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the range of z-coordinate of 0 micrometer to 10 micrometers both inclusive (0≦z≦10 μm) and in the range of z-coordinate of 210 micrometers to 216 micrometers both inclusive (210 μm≦z≦216 μm) are defined as air layers (refractive index 1), and a plane at z=214 micrometers (μm) parallel to the x-y plane is defined as an observation plane. A region in the calculation domain in the range of z-coordinate of 10 micrometers to 210 micrometers both inclusive (10 μm≦z≦210 μm) is defined as a region of the polarizer, and the refractive index thereof is assumed to be 1.5, except for the regions of the triangular prisms described below.
The triangular prisms are assumed to be regular triangular prisms having the refractive index of 1.8, the axis in the x-axis direction, the bottom faces of 10 micrometers (μm) on each side, and the height of 2 micrometers (μm). One bottom face thereof is set so as to be included in the plane at x=−1 micrometer (μm) parallel to the y-z plane. Thirty two triangular prisms are set and the positions of the respective triangular prisms are defined below by regular triangles of cross sections of the triangular prisms taken at x=0 and on the y-z plane. In the expression below, symbol “*” represents multiplication.
Namely, the triangular prisms constituted by those defined as follows:
triangular prisms defined by regular triangles each having one apex at the y-coordinate and the z-coordinate defined below;
(y,z)=(−10,23+5*sqrt(3)),
(−10,23+25*sqrt(3)),
(−10,23+45*sqrt(3)),
(−10,23+65*sqrt(3)),
(−10,23+85*sqrt(3)),
(−10,23+105*sqrt(3)),
(10,23+5*sqrt(3)),
(10,23+25*sqrt(3)),
(10,23+45*sqrt(3)),
(10,23+65*sqrt(3)),
(10,23+85*sqrt(3)),
(10,23+105*sqrt(3)),
(0,23+15*sqrt(3)),
(0,23+35*sqrt(3)),
(0,23+55*sqrt(3)),
(0,23+75*sqrt(3)),
(0,23+95*sqrt(3)),
and the opposite side to the apex being parallel to the y-axis and having the z-coordinate defined below;
z 23,
23+20*sqrt(3),
23+40*sqrt(3),
23+60*sqrt(3),
23+80*sqrt(3),
23+100*sqrt(3),
23,
23+20*sqrt(3),
23+40*sqrt(3),
23+60*sqrt(3),
23+80*sqrt(3),
23+100*sqrt(3),
23+10*sqrt(3),
23+30*sqrt(3),
23+50*sqrt(3),
23+70*sqrt(3),
23+90*sqrt(3),
(which are upwardly pointed regular triangles in part (b) in
triangular prisms defined by regular triangles each having one apex at the y-coordinate and the z-coordinate defined below;
(y,z)=(−10,23+5*sqrt(3)),
(−10,23+25*sqrt(3)),
(−10,23+45*sqrt(3)),
(−10,23+65*sqrt(3)),
(−10,23+85*sqrt(3)),
(10,23+5*sqrt(3)),
(10,23+25*sqrt(3)),
(10,23+45*sqrt(3)),
(10,23+65*sqrt(3)),
(10,23+85*sqrt(3)),
(0,23+15*sqrt(3)),
(0,23+35*sqrt(3)),
(0,23+55*sqrt(3)),
(0,23+75*sqrt(3)),
(0,23+95*sqrt(3)),
and the opposite side to the apex being parallel to the y-axis and having the z-coordinate defined below;
z=23+10sqrt(3),
23+30*sqrt(3),
23+50*sqrt(3),
23+70*sqrt(3),
23+90*sqrt(3),
23+10*sqrt(3),
23+30*sqrt(3),
23+50*sqrt(3),
23+70*sqrt(3),
23+90*sqrt(3),
23+20*sqrt(3),
23+40*sqrt(3),
23+60*sqrt(3),
23+80*sqrt(3),
23+100*sqrt(3),
(which are downwardly pointed regular triangles in part (b) in
With the above-described calculation system, polarized light with the electric field vector parallel to the x-axis is used as incident light, the energy of rays passing through the observation plane is calculated and referred to ass Ex.
Next, with a system obtained by substituting 1.5 for the refractive index of the triangular prisms in the above-described calculation system, similar calculation is performed using polarized light with the electric field vector parallel to the y-axis as incident light, and the energy of rays passing through the observation plane is defined as Ey. This calculation with the substitution for the refractive index of triangular prisms is conducted as simulation in the case where the birefringent bodies are dispersed.
Furthermore, assuming that the total energy of rays emitted from the light source is E0, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis can be defined respectively as follows:
Tx=Ex/E0, and
Ty=Ey/E0,
and the polarization degree P can be calculated as:
P=(Ty−Tx)/(Ty+Tx).
In the calculation system of this example, the calculation results were as follows: Tx=0, Ty=0.922, and P=1.00.
In this example, the calculation is conducted using the regular triangular prisms having the height of 2 micrometers (μm) and the cross section of the regular triangle of sides of 10 micrometers (μm), and therefore the aspect ratio, if calculated literally therefrom, is smaller than 1. However, the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0, and the two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are perfectly reflecting surfaces, which provides the same effect as in the case where a periodic boundary condition in the y-axis direction is imposed on the system used in the calculation. Therefore, it is the same as the case where the triangular prisms have the height of infinity and the aspect ratio of infinity.
This example shows optical characteristics in the case where the triangular prisms are uniformly dispersed in the support medium so that three triangular prisms with the sectional shape of a regular triangle are in contact at respective apexes of sectional regular triangles to form a regular triangular prism. The orthogonal coordinate system of the right hand system to express positions in the space is defined by (x,y,z) and the schematic view of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −5 micrometers to 5 micrometers both inclusive, the y-coordinate range of −10 micrometers to 10 micrometers both inclusive, and the z-coordinate range of 0 micrometer to 748 micrometers both inclusive, and is thus inside the rectangular parallelepiped defined below, as shown in part (a) in
−5 μm≦x≦5 μm,
−10 μm≦y≦10 μm, and
0≦z≦748 μm.
Two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −10 micrometers (μm) to 10 micrometers (μm) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-coordinate range of 0 to 15 micrometers both inclusive (0≦z≦15 μm) and in the z-coordinate range of 718 to 748 micrometers both inclusive (718 μm≦z ≦748 μm) are defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z=733 micrometers (μm) is defined as an observation plane. A region in the calculation domain in the z-coordinate range of 15 to 718 micrometers both inclusive (15 μm≦z≦718 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.3, except for the regions of the triangular prisms described below.
The triangular prisms are assumed to be regular triangular prisms having the refractive index of 1.9, the axis along the x-axis direction, the bottom faces of 20 micrometers (μm) on each side, and the height of 10×sqrt3 (10√{square root over (3)}μm). One bottom face thereof is set so as to be included in the plane at x=−5 micrometers (μm) parallel to the y-z plane. Thirty two triangular prisms are set and the positions of the respective triangular prisms are defined below by regular triangles of cross sections of the triangular prisms taken at x=0 and on the y-z plane.
Namely, the triangular prisms are constituted by those defined as follows:
triangular prisms defined by regular triangles each having one apex at the y-coordinate and the z-coordinate defined below;
(y,z)=(−10,42+10*sqrt(3)),
(−10,42+30*sqrt(3)),
(−10,42+50*sqrt(3)),
(−10,42+70*sqrt(3)),
(−10,42+90*sqrt(3)),
(−10,42+100*sqrt(3)),
(−10,42+130*sqrt(3)),
(−10,42+150*sqrt(3)),
(−10,42+170*sqrt(3)),
(−10,42+190*sqrt(3)),
(−10,42+210*sqrt(3)),
(10,42+10*sqrt(3)),
(10,42+30*sqrt(3)),
(10,42+50*sqrt(3)),
(10,42+70*sqrt(3)),
(10,42+90*sqrt(3)),
(10,42+110*sqrt(3)),
(10,42+130*sqrt(3)),
(10,42+150*sqrt(3)),
(10,42+170*sqrt(3)),
(10,42+190*sqrt(3)),
(10,42+210*sqrt(3)),
(0,42+20*sqrt(3)),
(0,42+40*sqrt(3)),
(0,42+60*sqrt(3)),
(0,42+80*sqrt(3)),
(0,42+100*sqrt(3)),
(0,42+120*sqrt(3)),
(0,42+140*sqrt(3)),
(0,42+160*sqrt(3)),
(0,42+180*sqrt(3)),
(0,42+200*sqrt(3)),
and the opposite side to the apex being parallel to the y-axis and having the z-coordinate defined below;
z=42,
42+20*sqrt(3),
42+40*sqrt(3),
42+60*sqrt(3),
42+80*sqrt(3),
42+100*sqrt(3),
42+120*sqrt(3),
42+140*sqrt(3),
42+160*sqrt(3),
42+180*sqrt(3),
42+200*sqrt(3),
42,
42+20*sqrt(3),
42+40*sqrt(3),
42+60*sqrt(3),
42+80*sqrt(3),
42+100*sqrt(3),
42+120*sqrt(3),
42+140*sqrt(3),
42+160*sqrt(3),
42+180*sqrt(3),
42+200*sqrt(3),
42+10*sqrt(3),
42+30*sqrt(3),
42+50*sqrt(3),
42+70*sqrt(3),
42+90*sqrt(3),
42+110*sqrt(3),
42+130*sqrt(3),
42+150*sqrt(3),
42+170*sqrt(3),
42+190*sqrt(3),
(which are blackened upwardly pointed regular triangles in part (b) of
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are: the transmittance Tx=0, Ty=0.966, and the polarization degree P=1.00.
In this example the calculation is conducted using the regular triangular prisms the height of 10 micrometers (μm) and having the cross section of the regular triangle having sides of 20 micrometers (μm), and, because the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0, and the two planes at y=−10 micrometers (μm) and at y=0 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes, the same assumption can be made as in the case where the triangular prisms have the height of infinity and the aspect ratio of infinity, which is the same as in Example 1.
This example shows optical characteristics in the case where triangular prisms are uniformly dispersed in the support medium so that three triangular prisms having the sectional shape of an isosceles triangle are in contact with apexes of bottoms of the other isosceles triangles at an apex of an apex angle in each sectional isosceles triangle so as to form an isosceles triangular prism. The orthogonal coordinate system of the right hand system to express positions in the region is defined by (x,y,z) and the schematic view of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −5 micrometers (μm) to 5 micrometers (μm) both inclusive, the y-coordinate range of −10 (μm) micrometers to 10 (μm) micrometers both inclusive, and the z-coordinate range of 0 micrometer to 959 micrometers (μm) both inclusive, and the domain is thus inside the rectangular parallelepiped defined below as shown in part (a) in
−5 μm≦x≦5 μm,
−10 μm≦y≦10 μm, and
0≦z≦959 μm.
Two planes at y=−0 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −10 micrometers (μm) to 10 micrometers (μ) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-coordinate range of 0 to 15 micrometers both inclusive (0≦z≦15 μm) and in the z-coordinate range of 929 micrometers to 959 micrometers both inclusive (929 μm≦z≦959 μm) are defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z=944 micrometers (μm) is defined as an observation plane. A region in the calculation domain in the z-coordinate range of 15 micrometers to 929 micrometers both inclusive (15 μm≦z≦929 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.3, except for the regions of the triangular prisms described below.
The triangular prisms have the refractive index of 1.8, the axis extending in the x-axis direction, and the isosceles triangle having the bottom faces of the bottom of 20 micrometers (μm), the height of 20+10×sqrt(3) micrometers (μm) and the apex angle of 30°, and one bottom face thereof is set so as to be included in the plane parallel to the y-z plane at x=−5 micrometers (μm). Thirty two triangular prisms are set and the positions of the respective triangular prisms are defined below by isosceles triangles of cross sections of the triangular prisms at x0 and on the y-z plane.
Namely, the triangular prisms are constituted by those defined as follows:
triangular prisms defined by isosceles triangles each having one apex at the y-coordinate and the z-coordinate defined below;
(y,z)=(−10,153+10*sqrt(3)),
(−10,193+30*sqrt(3)),
(−10,233+50*sqrt(3)),
(−10,273+70*sqrt(3)),
(−10,313+90*sqrt(3)),
(−10,353+110*sqrt(3)),
(−10,393+130*sqrt(3)),
(−10,433+150*sqrt(3)),
(−10,473+170*sqrt(3)),
(−10,513+190*sqrt(3)),
(−10,553+210*sqrt(3)),
(10,153+10*sqrt(3)),
(10,193+30*sqrt(3)),
(10,233+50*sqrt(3)),
(10,273+70*sqrt(3)),
(10,313+90*sqrt(3)),
(10,353+110*sqrt(3)),
(10,393+130*sqrt(3)),
(10,433+150*sqrt(3)),
(10,473+170*sqrt(3)),
(10,513+190*sqrt(3)),
(10,553+210*sqrt(3)),
(0,173+20*sqrt(3)),
(0,213+40*sqrt(3)),
(0,253+60*sqrt(3)),
(0,293+80*sqrt(3)),
(0,333+100*sqrt(3)),
(0,373+120*sqrt(3)),
(0,413+140*sqrt(3)),
(0,453+160*sqrt(3)),
(0,493+180*sqrt(3)),
(0,533+200*sqrt(3)),
and the opposite side to the apex being parallel to the y-axis and having the z-coordinate defined below;
z=133,
173+20*sqrt(3),
213+40*sqrt(3),
253+60*sqrt(3),
293+80*sqrt(3),
333+100*sqrt(3),
373+120*sqrt(3),
413+140*sqrt(3),
453+160*sqrt(3),
493+180*sqrt(3),
533+200*sqrt(3),
133,
173+20*sqrt(3),
213+40*sqrt(3),
253+60*sqrt(3),
293+80*sqrt(3),
333+100*sqrt(3),
373+120*sqrt(3),
413+140*sqrt(3),
453+160*sqrt(3),
493+180*sqrt(3),
533+200*sqrt(3),
153+10*sqrt(3),
193+30*sqrt(3),
233+50*sqrt(3),
273+70*sqrt(3),
313+90*sqrt(3),
353+110*sqrt(3),
393+130*sqrt(3),
433+150*sqrt(3),
473+170*sqrt(3),
513+190*sqrt(3),
(which are blackened upwardly pointed regular triangles in part (b) of
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are as follows: Tx=0, Ty=0.966, and the polarization degree P=100.
In this example, the calculation is conducted using the isosceles triangular prisms having the height of 10 micrometers (μm) and the cross section of the isosceles triangle with the bottom of 20 micrometers (μm), the height of 20+10×sqrt(3) micrometers (μm), and the apex angle of 30°, and, because the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0 and the two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes, the same assumption can be made as in the case where the triangular prisms have the height of infinity and the aspect ratio of infinity, which is the same as in Example 1.
This example shows optical characteristics in the case where rectangular prisms are uniformly dispersed in the support medium so that four rectangular prisms having the sectional shape of a square are in contact at apexes of respective sectional squares to form a square. The orthogonal coordinate system of the right hand system to express positions in the region is defined by (x,y,z) and the schematic view of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −5 micrometers to 5 micrometers both inclusive, the y-coordinate range of −10 micrometers to 10 micrometers both inclusive, and the z-coordinate range of 0 micrometer to 748 micrometers both inclusive, and is thus inside the rectangular parallelepiped defined below as shown in part (a) in
−5 μm≦x≦5 μm,
−10 μm≦y≦10 μm, and
0≦z≦748 μm.
Two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −10 micrometers to 10 micrometers (−10 μm≦y≦10 μm) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-coordinate range of 0 to 15 micrometers both inclusive (0≦z≦15 μm) and in the z-coordinate range of 718 micrometers to 748 micrometers both inclusive (718 μm≦z≦748 μm) are defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z=733 micrometers (μm) is defined as an observation plane. A region in the calculation domain in the z-coordinate range of 15 micrometers (μm) to 718 micrometers (μm) both inclusive (15 μm≦z≦718 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.7, except for the regions of the rectangular prisms described below.
The rectangular prisms are square prisms having the refractive index of 1.2, the axis extending in the x-axis direction, and each side of the bottom faces of 10×sqrt(2) micrometers (10√{square root over (2)}μm), and one bottom face thereof is included in the plane parallel to the y-z plane at x=−5 micrometers (μm). Forty two rectangular prisms are set, and the positions of the respective rectangular prisms are defined below by squares of cross sections of the rectangular prisms on the y-z plane at x=0.
Namely, the rectangular prisms are constituted by the total of forty two prisms (in 21 layers in the z-axis direction) each of which is surrounded by four apexes at the y-coordinates and z-coordinates in a square defined as follows.
However, portions that are off the domain used in the calculation are ignored.
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are as follows: Tx=0, Ty=0.870, and the polarization degree P=1.00.
In this example, the calculation is conducted using the rectangular prisms having the cross section of the square of 10×sqrt(2) micrometers (10√{square root over (2)}μm) on each side and the height of 10 micrometers (μm), and, because the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0 and the two planes at y=−10 micrometers (μ) and at y=10 micrometers (μm) parallel to the z-x plane are perfectly reflecting planes, the same assumption can be made as in the case where the rectangular prisms have the height of infinity and the aspect ratio of infinity, which is the same as in Example 1.
This example shows optical characteristics in the case where circular cylinders with the sectional shape of a circle are closely packed in a total of 21 layers in the thickness direction. The orthogonal coordinate system of the right hand system to express positions in the region is defined by (x,y,z) and the schematic view of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −5 micrometers to 5 micrometers both inclusive, the y-coordinate range of −10 micrometers to 10 micrometers both inclusive, and the z-coordinate range of 0 micrometer to 748 micrometers both inclusive, and is thus inside the rectangular parallelepiped defined below as shown in part (a) in
−5 μm≦x≦5 μm,
−10 μm≦y≦10 μm, and
0≦z≦748 μm.
Two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −10 micrometers to 10 micrometers (−10 μm≦y≦10 μm) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-coordinate range of 0 to 15 micrometers both inclusive (0≦z≦15 μm) and in the z-coordinate range of 718 micrometers to 748 micrometers both inclusive (718 μm≦z≦748 μm) are defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z=733 micrometers (μm) is defined as an observation plane. A ewrion in the calculation domain in the z-coordinate range of 15 micrometers to 718 micrometers both inclusive (15 μm≦z≦718 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.4, except for the regions of the circular cylinders described below.
The circular cylinders are those having the refractive index of 1.9, the axis extending in the x-axis direction, the diameter of the bottom faces of 20 micrometers (μm), and the height of 10 micrometers (μm), and one bottom face thereof is set so as to be included in the plane parallel to the y-z plane at x=−5 micrometers (μm). Thirty two circular cylinders are set, and the positions of the respective circular cylinders are defined below by centers of circles in the cross section of each circular cylinder on the y-z plane at x=0.
Namely, the y-coordinates and z-coordinates of the centers of the circles are defined as follows:
(y,z)=(−10,201),
(−10,201+20*sqrt(3)),
(−10,201+40*sqrt(3)),
(−10,201+60sqrt(3),
(−10,201+80*sqrt(3)),
(−10,201+100*sqrt(3)),
(−10,201+120*sqrt(3)),
(−10,201+140*sqrt(3)),
(−10,201+160*sqrt(3)),
(−10,201+180*sqrt(3)),
(−10,201+200*sqrt(3)),
(10,201),
(10,201+20*sqrt(3)),
(10,201+40*sqrt(3)),
(10,201+60*sqrt(3)),
(10,201+80*sqrt(3)),
(10,201+100*sqrt(3)),
(10,201+120*sqrt(3)),
(10,201+140*sqrt(3)),
(10,201+160*sqrt(3)),
(10,201+180*sqrt(3)),
(10,201+200*sqrt(3)),
(0,201+10*sqrt(3)),
(0,201+30*sqrt(3)),
(0,201+50*sqrt(3)),
(0,201+70*sqrt(3)),
(0,201+90*sqrt(3)),
(0,201+110*sqrt(3)),
(0,201+130*sqrt(3)),
(0,201+150*sqrt(3)),
(0,201+170*sqrt(3)),
(0,201+190*sqrt(3)).
However, the above numerals are calculated to six places of decimals, and portions that are off the domain used in the calculation are ignored.
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are obtained as follows: Tx=0.00048, Ty=0.944, and the polarization degree P=0.999.
In this example, the calculation is conducted using the circular cylinders having the height of 10 micrometers (μm) and the cross section of the circle with the radius of 10 micrometers (μm) (i.e., the diameter of 20 μm), and the aspect ratio, when calculated literally therefrom, is smaller than 1. However, the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0 and the two planes parallel to the z-x plane at y=−10 micrometers (μm) and at y=10 micrometers (μm) are perfectly reflecting surfaces, which allows the same assumption as in the case where the periodic boundary condition in the y-axis direction is imposed on the system used in the calculation. Therefore, it is the same as the case where the circular cylinders have the height of infinity and the aspect ratio of infinity.
This example shows optical characteristics in the case where circular cylinders with the sectional shape of a circle are closely packed in a total of 10 layers in the thickness direction. The orthogonal coordinate system of the right hand system to express positions in the region is defined by (x,y,z) and the schematic picture of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −5 micrometers to 5 micrometers both inclusive, the y-coordinate range of −10 micrometers to 10 micrometers both inclusive, and the z-coordinate range of 0 micrometer to 748 micrometers both inclusive, and is thus inside the rectangular parallelepiped defined below as shown in part (a) in
−5 μm≦x≦5 μm,
−10 μm≦y≦10 μm,and
0≦z≦748 μm.
Two planes at y=−10 micrometers (μm) and at y=10 micrometers (μm) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −10 micrometers to 10 micrometers (−10 μm≦y≦10 μm) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-range of 0 to 15 micrometers both inclusive (0≦z≦15 μm) and in the z-range of 718 micrometers to 748 micrometers both inclusive (718 μm≦z≦748 μm) were defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z-733 micrometers (μm) is defied as an observation plane. A region in the calculation domain in the z-coordinate range of 15 micrometers to 718 micrometers both inclusive (15 μm≦z≦718 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.6, except for the regions of the circular cylinders described below.
The circular cylinders are those having the refractive index of 2.3, the axis extending in the x-axis direction, the diameter of the bottom faces of 20 micrometers (μm), and the height of 10 micrometers (μm), and one bottom face thereof is set so as to be included in the plane parallel to the y-z plane at x=−5 micrometers (μm). Fifteen circular cylinders are set, and the positions of the respective circular cylinders are defined below by centers of circles in the cross section of each circular cylinder on the y-z plane at x=0.
Namely, the y-coordinates and z-coordinates of the centers of the circles are defined as follows:
(y,z)=(−10,270),
(−10,270+20*sqrt(3)),
(−10,270+40*sqrt(3)),
(−10,270+60*sqrt(3)),
(−10,270+80*sqrt(3)),
(10,270),
(10,270+20*sqrt(3)),
(10,270+40*sqrt(3)),
(10,270+60*sqrt(3)),
(10,270+80*sqrt(3)),
(0,270+10*sqrt(3)),
(0,270+30*sqrt(3)),
(0,270+50*sqrt(3)),
(0,270+70*sqrt(3)),
(0,270+90*sqrt(3)).
However, the above numerals are calculated to six places of decimals, and portions of the numerals that are off the domain used in the calculation are ignored.
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are obtained as follows: Tx=0.049, Ty=0.895, and the polarization degree P=0.896.
In this example, the calculation is also conducted using the circular cylinders having the cross section of the circle with the radius of 10 micrometers (μm) (i.e., the diameter of 20 μm) and the height of 10 micrometers (μm), and, because the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0 and the two planes parallel to the z-x plane at y=−10 micrometers (μm) and at y=10 micrometers (μm) are perfectly reflecting planes, the same assumption can be made as in the case where the circular cylinders have the height of infinity and the aspect ratio of infinity, as in Example 1.
This example shows optical characteristics in the case where circular cylinders are uniformly dispersed in the same direction in the support medium. The orthogonal coordinate system of the right hand system to express positions in the region is defined by (x,y,z) and the schematic picture of the system used in the calculation in this example is presented in
The domain used in the calculation is defined by the x-coordinate range of −1 micrometer to 1 micrometer both inclusive, the y-coordinate range of −15 micrometers to 15 micrometers both inclusive, and the z-coordinate range of 0 micrometer to 300 micrometers both inclusive, and is thus inside the rectangular parallelepiped defined below as shown in part (a) in
−1 μm≦x≦1 μm,
−15 μm≦y≦15 μm, and
0≦z≦300 μm.
Two planes at y=−15 micrometers (μm) and at y=15 micrometers (μm ) parallel to the z-x plane are assumed to be perfectly reflecting planes. On the other hand, a light source is defined as a line segment parallel to the y-axis at x=z=0 and in the y-coordinate range of −15 micrometers to 15 micrometers (−15 μm≦y≦15 μm) both inclusive, and the light source generates 5001 rays in the positive direction of the z-axis.
Regions in the calculation domain in the z-coordinate range of 0 to 10 micrometers both inclusive (0≦z≦10 μm) and in the z-coordinate range of 290 micrometers to 300 micrometers both inclusive (290 μm≦z≦300 μm) are defined as air layers (refractive index 1) and a plane parallel to the x-y plane at z=295 micrometers (μm) is defined as an observation plane. A region in the calculation domain in the z-coordinate range of 10 micrometers to 290 micrometers both inclusive (10 μm≦z≦290 μm) is defined as a region of the polarizer and the refractive index thereof is assumed to be 1.6, except for the regions of the circular cylinders described below.
The circular cylinders are those having the refractive index of 2.3, the axis extending in the x-axis direction, the radius of the bottom faces of 10 micrometers (μm), and the height of 2 micrometers (μm), and one bottom face thereof is set so as to be included in the plane parallel to the y-z plane at x=−1 micrometer (μm). Fifteen circular cylinders are set, and the positions of the respective circular cylinders are defined below by centers of circles in the cross section of each circular cylinder on the y-z plane at x=0.
Namely, the y-coordinates and z-coordinates of the centers of the circles are defined as follows:
(y,z)=(0,23+5*sqrt(3)),
(−15,23+20*sqrt(3)),
(15,23+20*sqrt(3)),
(0,23+35*sqrt(3)),
(−15,23+50*sqrt(3)),
(15,23+50*sqrt(3)),
(0,23+65*sqrt(3)),
(−15,23+80*sqrt(3)),
(15,23+80*sqrt(3)),
(0,23+95*sqrt(3)),
(−15,23+110*sqrt(3)),
(15,23+110*sqrt(3)),
(0,23+125*sqrt(3)),
(−15,23+140*sqrt(3)),
(15,23+140*sqrt(3)),
However, the above numerals are calculated to six places of decimals, and portions of the numerals that are off the domain used in the calculation are ignored.
With the above-described calculation system, the transmittance Tx for the polarized light with the electric field vector parallel to the x-axis, and the transmittance Ty for the polarized light with the electric field vector parallel to the y-axis are calculated in the same manner as in Example 1, and the results are obtained as follows: Tx=0.390, Ty=0.896, and the polarization degree P=0.393.
In this example, the calculation is also conducted using the circular cylinders having the cross section of the circle with the radius of 10 micrometers (μm) (i.e., the diameter of 20 μm) and the height of 2 micrometers (μm), and, because the system used in the calculation is in plane symmetry with respect to the z-x plane at y=0 and the two planes parallel to the z-x plane at y=−15 micrometers (μm) and at y=15 micrometers (μm) are assumed to be perfectly reflecting planes, the same assumption can be made as in the case where the circular cylinders have the height of infinity and the aspect ratio of infinity, as in Example 1.
Industrial Applicability
The reflective polarizer of the present invention can form the structure in which the birefringent bodies are dispersed and oriented substantially in one direction by a simple method and is unlikely to cause delamination, by virtue of the configuration wherein the interfaces between different materials are not simple planes. In addition, the support medium for fixing the birefringent bodies is constructed of the isotropic substance, and the reduction of strength is relatively small with increase in the volume fraction of the birefringent bodies, whereby it is easy to increase the volume fraction of the birefringent bodies. Furthermore, when this reflective polarizer is located on the other side than the observer side of the liquid crystal panel where the absorptive polarizer is provided, the efficiency of utilization of light is so high as to enable provision of the liquid crystal display apparatus with high luminance and low power consumption.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-199655 | Jul 2003 | JP | national |
| 2004-186036 | Jun 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/10403 | 7/22/2004 | WO | 8/15/2006 |
