TWI436102B - An optical unit and a backlight unit using the optical unit - Google Patents

Description

Optical unit and backlight unit using the same

The present invention relates to an optical unit suitable for a liquid crystal display device having excellent surface uniformity and a wide viewing angle, particularly a backlight unit for a liquid crystal display device for a car navigation system, and a backlight unit using the same.

A liquid crystal display device is widely used as a display device for a screen such as a television or a personal computer, and is roughly classified into a direct view type that directly views a display screen and a projection type that views an image displayed on a screen. The direct-view liquid crystal display device has a transmissive type that transmits light of a backlight, a reflection type that does not have a backlight, and uses reflected light such as natural light or an indoor lamp, and a transmissive type that is reflective in a bright place and transmissive in a dark place. formula. On the other hand, in the projection type liquid crystal display device, there is a rear projection type in which a screen is projected on the front surface of the screen, and a screen is incorporated into the display cabinet to reflect the image. Nowadays, a direct-view type, in which a transmissive liquid crystal display device is used as a mainstream, is commonly used.

In the transmissive liquid crystal display device, a backlight method for illuminating the liquid crystal layer from the back surface is popular, and a backlight unit such as an edge illumination type (sidelight type) or a direct type is provided on the lower surface side of the liquid crystal layer. The edge-lit backlight unit 20 is generally provided with a lamp 21 as a light source, a square plate-shaped light guide plate 22 disposed at an end portion along the lamp 21, and laminated on the light guide plate. Optical unit 23 on the surface side of 22. As the light source 21, an LED (Light-Emitting Diode) or a cold cathode tube is used, and LEDs are generally used in terms of miniaturization and energy saving. The optical unit 23 is provided with an optical sheet in which a plurality of sheets are stacked, and has optical functions such as diffusion and refraction for transmitted light. As the optical sheet provided in the optical unit 23, (1) a light-diffusing sheet 24 mainly disposed on the surface side of the light guide plate 22 and having a light diffusing function, or (2) disposed on the light-diffusing sheet can be used. The surface side of 24, the ruthenium sheet 25 having a refractive function toward the normal side, and the like.

Further, although not shown, in consideration of the light guiding characteristics of the light guide plate 22 or the optical function of the optical sheet provided in the optical unit 23, a light diffusion sheet or a ruthenium sheet is more often disposed. An optical unit 23 of an optical sheet.

As a liquid crystal display device having such a backlight unit, there is a user of a car navigation system. The liquid crystal display device for the car navigation system is usually disposed on a center console between the driver's seat and the passenger's seat of the automobile. Therefore, the liquid crystal display device for a car navigation system requires different optical performance from other liquid crystal display devices such as personal computers. That is, the liquid crystal display device for car navigation requires a wide viewing angle so that the liquid crystal screen can be viewed from the driver's seat and the passenger's seat more appropriately from the front side than the front side. In order to cope with such a request, for example, a backlight unit 30 having an optical unit which is orthogonal to the ridges of the two sheets of the optical sheet as shown in FIG. The mirror is disposed inward (light guide plate direction) (for example, refer to Japanese Patent Laid-Open Publication No. 2001-195913, etc.).

The function of the backlight unit 30 will be described. First, the light incident on the light guide plate 32 from the lamp 31 is reflected by the reflection point or the reflection sheet (not shown) on the back surface of the light guide plate 32 and the respective side surfaces, and the self-light guide plate 32 is reflected. The surface is emitted. The light emitted from the light guide plate 32 is incident on the crucible sheet 34, and is refracted to be emitted from the surface. Then, the light emitted from the surface of the sheet 34 is incident on the sheet 35, and is emitted as a light which is widely distributed in the left-right direction by the plurality of protrusions formed on the surface. As described above, in the backlight unit 30 for the liquid crystal display device of the conventional car navigation system, the light emitted from the lamp 31 is diffused by the optical unit 33, and is refracted in the left-right direction so as to exhibit a peak, and the illumination is not shown. The entire surface of the liquid crystal layer.

However, according to the optical unit 33, as shown in the comparative example 1 in the graph of FIG. 4, since the refraction of the two sheets 34 and 35 in the oblique direction is too high, the front luminance is lowered, and if the automobile is viewed from the front, The liquid crystal screen of the navigation system produces a bad condition in which the screen becomes dark.

[Previous Technical Literature] [Patent Literature]

Patent Document 1 Japanese Patent Laid-Open Publication No. 2001-195913

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an optical unit having high optical functions such as refraction toward a normal direction side and wide-angle light diffusion, and which can easily and surely control the optical function, and the use of the optical unit A backlight unit that promotes an increase in quality such as high brightness in the front direction, wide viewing angle, and uniform brightness.

The invention developed to solve the above problems is an optical unit comprising a microlens sheet and a tantalum sheet disposed on a surface side of the microlens sheet, the microlens sheet having a plurality of microlenses on the back surface In the microlens array, the enamel sheet has a protrusion row composed of a plurality of ridge portions on the surface.

In addition to the enamel sheet, the optical unit has a microlens sheet which exhibits an excellent optical function, so that optical functions such as refraction toward the normal direction side and wide-angle light diffusion are particularly enhanced. Further, the microlens sheet has a microlens array on the back surface, whereby the light diffusion function is enhanced, and the surface uniformity of the optical unit is particularly improved.

The average diameter of the microlenses in the above microlens sheet is preferably 10 μm or more and 200 μm or less. The microlens sheeting has a microlens having an average diameter in such a range, whereby the optical function can be easily and surely controlled, and the surface uniformity of the optical unit is improved.

The coefficient of variation of the diameter of the microlens in the above microlens sheet is preferably 30% or more and 100% or less. As a result, the diameter of the microlens has a certain range of distribution, whereby the wide-angle light diffusion function is further improved, and the wide viewing angle of the backlight unit can be realized.

The refractive index of the material constituting the microlens array in the microlens sheet is preferably 1.3 or more and 1.8 or less. The material constituting the microlens array has the above refractive index, whereby the refraction and light diffusion of the light in the microlens array in the normal direction can be uniformly performed at a wide angle.

It is preferred to use a polycarbonate resin as a material for forming the above microlens sheet. The microlens sheet has a polycarbonate resin as a forming material, whereby the microlens of the above specific shape can be easily and surely formed, so that the control of the optical function can be easily and surely performed, and since it has an appropriate refractive index and High transmittance, so the front brightness is increased and wide-angle light diffusion can be achieved.

The arrangement pattern of the microlenses in the microlens array of the above microlens sheet is preferably a random pattern. According to the optical unit having such a random pattern, the generation of the moiré can be reduced when the microlens sheet is overlapped with other optical members, and the light diffusibility can be improved.

The above-mentioned ridge portion is preferably triangular prism-shaped and has a vertex shape in a rounded state. The ridge portion of the ridge is triangular in shape, and the apex angle of the ridge is rounded, so that the angle of refraction of the light emerging from the optical unit toward the normal direction is reduced on the surface of the ridge of the ridge, so Increase the amount of light emitted toward the normal to increase the front brightness.

Another invention developed to solve the above problems is a backlight unit for a liquid crystal display device which disperses and guides light emitted from a lamp to a surface side, and the backlight unit for the liquid crystal display device is characterized by a light guide plate, a lamp disposed on a side end surface of the light guide plate, and the optical unit disposed on a surface side of the light guide plate. Since the optical unit has a high optical function such as refraction in the normal direction and light diffusion at a wide angle, it is possible to improve the quality of the front side of the backlight unit, such as high brightness, wide viewing angle, and uniform brightness. In particular, the backlight unit which can realize a wide viewing angle can be suitably used in a liquid crystal display device for a car navigation system which is viewed from a tilt direction in most cases.

Here, the term "microlens" means a microlens having a partial spherical shape, and for example, a hemispherical convex lens, a hemispherical concave lens, or the like corresponds to the microlens. In addition, the cross-sectional shape in the direction perpendicular to the direction of the stripe portion is not particularly limited, and includes, for example, a variety of polygons such as a square or a pentagon, or a waveform, in addition to a triangle such as a right triangle. The "polycarbonate resin" refers to a polymer having a carbonate bond (-O-R-O-CO-) in its main chain. Further, the "surface" of each sheet refers to the side on the side where the light is emitted when the optical unit is provided in the backlight unit. Moreover, the "back surface" of each sheet means the surface on the other side where light rays are incident. The "coefficient of variation" of the diameter of the microlens is defined by dividing the standard deviation of the diameter by the average diameter.

As described above, according to the optical unit of the present invention, optical functions such as refraction toward the normal direction side and wide-angle light diffusion are extremely high, and the optical function can be easily and surely controlled according to the backlight unit using the optical unit. It can improve the brightness of the front direction, the wide viewing angle, and the uniformity of brightness.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The optical unit 1 of FIG. 1 is provided with a microlens sheet 2 and a enamel sheet 3 as an optical sheet, and a enamel sheet 3 is disposed on the surface side of the lenticular sheet 2.

As shown in FIG. 2, the microlens sheet 2 includes a sheet-like base material layer 4 and a microlens array 5 provided on the back surface of the base material layer 4.

Since the base material layer 4 must transmit light, it is formed of a transparent, particularly colorless, transparent synthetic resin. The synthetic resin to be used as a material for forming the base material layer 4 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, and polycarbonate resin. Polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride, active energy ray-curable resin, and the like. In particular, an active energy ray-curable resin such as an ultraviolet curable resin or an electron beam curable resin which is excellent in moldability of the microlens array 5 or a polycarbonate resin excellent in transparency and strength is preferable. Further, it is also preferred to use a polyethylene terephthalate film, a polyethylene naphthalate film or a polycarbonate resin film as the base material layer 4, and to form an ultraviolet curable resin or the like thereon. Microlens 6.

The polycarbonate resin forming the base material layer 4 is preferably a polycarbonate resin containing a linear polycarbonate resin and/or a branched polycarbonate resin. The linear polycarbonate resin and the branched polycarbonate resin used in the present invention are not particularly limited, and those which are generally used can be used. Further, the base layer 4 may be formed only of a linear polycarbonate resin or a branched polycarbonate resin.

The linear polycarbonate resin is a linear aromatic polycarbonate resin produced by a known phosgene method or a melting method, and is formed of a carbonate component and a bisphenol component. Examples of the precursor for introducing the carbonate component include phosgene and diphenyl carbonate. Further, examples of the bisphenol include 4,4'-dihydroxy-2,2'-diphenylpropane, 2,2-bis(4-hydroxyphenyl)propane, and 2,2-bis (3, 5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl) Cyclohexane, 1,1-bis(4-hydroxyphenyl)decane, 1,4-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclodecane, 1 , 1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclododecane, 4,4-dihydroxydiphenyl ether, 4,4-thiobisphenol, 4,4-dihydroxy -3,3-dichlorodiphenyl ether, 4,4-dihydroxy-2,5-dihydroxydiphenyl ether, and the like. These may be used alone or in combination of two or more.

The branched polycarbonate resin is a polycarbonate resin produced by using a branching agent, and examples of the branching agent include fluoroglycine, trimellitic acid, and 1,1,1-tris(4-hydroxyphenyl)B. Alkane, 1,1,2-tris(4-hydroxyphenyl)ethane, 1,1,2-tris(4-hydroxyphenyl)propane, 1,1,1-tris(4-hydroxyphenyl)methane 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,1-tris(4-hydroxyphenyl)propane, 1,1,1-tris(2-methyl-4-hydroxyl Phenyl)methane, 1,1,1-tris(2-methyl-4-hydroxyphenyl)ethane, 1,1,1-tris(3-methyl-4-hydroxyphenyl)methane, 1, 1,1-tris(3-methyl-4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dimethyl-4-hydroxyphenyl)methane, 1,1,1- Tris(3,5-dimethyl-4-hydroxyphenyl)ethane, 1,1,1-tris(3-chloro-4-hydroxyphenyl)methane, 1,1,1-tris(3-chloro 4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)methane, 1,1,1-tris(3,5-dichloro-4- Hydroxyphenyl)ethane, 1,1,1-tris(3-bromo-4-hydroxyphenyl)methane, 1,1,1-tris(3-bromo-4-hydroxyphenyl)ethane, 1, 1,1-tris(3,5-dibromo-4-hydroxyphenyl)methane, 1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)ethane, and the like.

Such a branched polycarbonate-based resin can be produced, for example, by the following method, as described in Japanese Patent Application No. Hei 1-321552: for aromatic bisphenols, the above-mentioned branching agents, and phosgene-derived poly The carbonate oligomer, the aromatic bisphenol, and the terminal terminator are reacted while stirring in such a manner that the reaction mixture containing the compounds is turbulent, and an alkaline aqueous solution is added at the time when the viscosity of the reaction mixture rises. Further, the reaction mixture was subjected to laminar flow and reacted. The branched polycarbonate resin of the resin composition of the present invention is contained in the polycarbonate resin in an amount of from 5 to 80% by mass, preferably from 10 to 60% by mass. When the branched polycarbonate resin is less than 10% by mass, the elongational viscosity is lowered and the molding at the time of extrusion molding becomes difficult. When the amount is more than 80% by mass, the shear viscosity of the resin is increased and the moldability is lowered.

The thickness (average thickness) of the base material layer 4 is not particularly limited, and is, for example, 10 μm or more and 500 μm or less, preferably 35 μm or more and 250 μm or less, and particularly preferably 50 μm or more and 188 μm or less. When the thickness of the base material layer 4 is less than the above range, it may occur when the backlight unit or the like is exposed to heat, and warpage is likely to occur, and the use becomes difficult. On the other hand, if the thickness of the base material layer 4 exceeds the above range, In some cases, the brightness of the liquid crystal display device is lowered, and the thickness of the backlight unit is increased to deviate from the requirement for thinning of the liquid crystal display device.

The microlens array 5 is composed of a plurality of microlenses 6. The microlens 6 is formed into a hemispherical shape (including a shape similar to a hemisphere) such as an optical curved shape body that refracts light to be diverged or focused, and is provided on the back surface of the base material layer 4. Since the microlens 6 is required to transmit light, it is formed of a transparent, in particular, colorless and transparent synthetic resin. Specifically, the same synthetic resin as the above-mentioned base material layer 4 is used. Among them, a polycarbonate resin which is excellent in transparency, strength, and has a suitable refractive index is particularly preferable.

Further, the microlens 6 is not limited to the above-described hemispherical convex lens, and may be a microlens of a hemispherical concave lens. The microlens of the hemispherical concave lens also has an excellent optical function similarly to the above-described microlens 6. Further, the microlenses 6 constituting the microlens array 5 are not limited to the same shape and size. Further, the microlens array 5 is not limited to a hemispherical convex lens alone or a hemispherical concave lens, and may be composed of a plurality of microlenses such as a hemispherical convex lens and a hemispherical concave lens.

In addition to the above synthetic resin, the base material layer 4 and the microlens 6 may be, for example, a filler, a plasticizer, a stabilizer, an anti-deterioration agent, a dispersant or the like.

The microlenses 6 are relatively densely and randomly disposed on the back surface of the substrate layer 4. According to the random pattern, the generation of the moiré can be reduced when the lenticular sheet 2 is overlapped with other optical members, and the light diffusibility can be improved, so that the uniform light can be emitted at a wide angle.

The lower limit of the average diameter (D) of the microlens 6 is preferably 10 μm, particularly preferably 30 μm, and particularly preferably 40 μm. On the other hand, the upper limit of the average diameter (D) of the microlens 6 is preferably 200 μm, particularly preferably 150 μm, and particularly preferably 100 μm. When the average diameter (D) of the microlens 6 is less than 10 μm, the influence of diffraction becomes large, and it is easy to cause deterioration in optical performance or color separation, resulting in deterioration in quality. On the other hand, when the average diameter (D) of the microlens 6 exceeds 200 μm, an increase in thickness or unevenness in brightness is likely to occur, resulting in deterioration in quality.

The lower limit of the coefficient of variation of the diameter (D) of the microlens 6 is preferably 30%, particularly preferably 40%, and the upper limit is preferably 100%, particularly preferably 80%. The diameter (D) of the microlens 6 has a specific coefficient of variation of the above range, that is, has a certain distribution, whereby the light incident on the lenticular sheet can be diffused at a wide angle, thereby making the surface of the optical unit uniform. Sexual improvement. Further, if the coefficient of variation of the diameter (D) of the microlens 6 exceeds the above upper limit, the smoothness of the back surface of the microlens sheet 2 may be lost, resulting in a decrease in total light transmittance. Here, the "coefficient of variation" of the diameter (D) is defined by dividing the standard deviation of the diameter by the average diameter.

The lower limit of the surface roughness (Ra) of the microlens 6 is preferably 0.01 μm, particularly preferably 0.03 μm. On the other hand, the upper limit of the surface roughness (Ra) of the microlens 6 is preferably 0.1 μm, particularly preferably 0.07 μm. By setting the surface roughness (Ra) of the microlens 6 to the above lower limit or more, the formability of the microlens array 5 of the microlens sheet 2 becomes relatively easy, and the technical burden on manufacturing is reduced. Cost burden. On the other hand, by setting the surface roughness (Ra) of the microlens 6 to be smaller than the above upper limit, the scattering of light on the surface of the microlens 6 is reduced, and as a result, the refractive function or light toward the normal side of the microlens 6 can be improved. The diffusion function can achieve high brightness in the front direction and uniformization of the emitted light due to the good optical function.

The lower limit of the height ratio (H/R) of the average height (H) of the microlens 6 with respect to the average radius of curvature (R) is preferably 5/8, particularly preferably 3/4. On the other hand, the upper limit of the height ratio (H/R) is preferably 1.3. By setting the height ratio (H/R) of the microlens 6 to the above range as described above, the lens refraction of the microlens 6 can be effectively exhibited, and the optical function such as condensing of the microlens sheet 2 can be particularly enhanced.

The upper limit of the ratio (S/D) of the average inter-lens distance (S; P-D) to the average diameter (D) of the microlens 6 is preferably 1/2, particularly preferably 1/5. By setting the average inter-lens distance (S) of the microlens 6 to the above-described upper limit or less, the flat portion that does not contribute to the optical function is reduced, and the optical function such as the condensing of the microlens sheet 2 is particularly enhanced.

The lower limit of the filling ratio of the microlens 6 is preferably 40%, particularly preferably 60%. By setting the filling ratio of the microlens 6 to the above lower limit or more, the area occupied by the microlens 6 is increased, and the optical function such as the light diffusion function of the microlens sheet 2 is particularly enhanced. Furthermore, the filling rate of the microlens refers to the ratio of all the microlenses per specific unit area.

The lower limit of the refractive index of the material constituting the microlens array 5 is preferably 1.3, particularly preferably 1.45. On the other hand, the upper limit of the refractive index of the material is preferably 1.8, and particularly preferably 1.6. In this range, the refractive index of the material constituting the microlens array 5 is preferably 1.5. By setting the refractive index of the material constituting the microlens array 5 to the above range, the lens refraction of the microlens 6 is effectively exerted, and the optical function such as light diffusion of the microlens sheet 2 is further improved.

The method for producing the microlens sheet 2 is not particularly limited as long as the above-described structure can be formed, and various methods can be employed. As a method of manufacturing the microlens sheet 2, a method of forming the base layer 4 and then forming the microlens array 5, and a method of integrally forming the base layer 4 and the microlens array 5 may be employed. Specifically, there are:

(a) a method of laminating a synthetic resin on a sheet mold having an inverted shape of the microlens array 5, and peeling the sheet mold to form the microlens sheet 2;

(b) an injection molding method in which a molten resin is injected into a metal mold having an inverted shape of the microlens array 5;

(c) a method of reheating the sheet-formed resin and sandwiching it between the same metal mold and the metal plate as described above, and pressing to transfer the shape;

(d) a sheet forming method in which a roll mold having a reverse shape of the microlens array 5 on the circumferential surface and a nip of another roll are passed through a resin in a molten state, and the shape is transferred and pressed;

(e) applying an ultraviolet curable resin to the base material layer, pressing against a sheet mold, a metal mold or a roll mold having the same reverse shape as described above, and irradiating the uncured ultraviolet curable resin to a shape a method of hardening an ultraviolet curable resin by ultraviolet rays;

(f) a method of applying a uncured ultraviolet curable resin to a metal mold or a roll mold having a reversed shape as described above, and laminating and flattening the base material, and irradiating the ultraviolet ray to cure the ultraviolet curable resin ;

(g) a method of ejecting or ejecting an uncured (liquid) ultraviolet curable resin from a fine nozzle toward a sheet substrate; and

(h) A method of using an electron beam curing resin instead of the ultraviolet curable resin.

The method for producing the mold having the inverted shape of the microlens array 5 can be manufactured, for example, by forming a speckled three-dimensional pattern on a substrate by a photoresist material to make the three-dimensional pattern. A microlens array model was produced by heating and fluidizing to form a curved surface, and a metal layer was laminated on the surface of the microlens array model by electroforming to peel off the metal layer. Further, as the method of producing the microlens array model, the method described in the above (g) may be employed.

As another manufacturing method of the above-described mold (sheet mold or the like) having the inverted shape of the microlens array 5, it can be manufactured by using an optical sheet original having a microlens array shape on the surface by extrusion The synthetic resin layer for the surface layer mold of the optical sheet original is laminated, and the optical sheet original is peeled off from the synthetic resin layer for the mold. In the extrusion lamination method, it is particularly preferable to laminate a synthetic resin layer for a mold between an optical sheet original sheet and a substrate sheet for a mold by interlayer extrusion lamination.

According to the above manufacturing method, the surface shape of the optical sheet original having the shape of the microlens array on the surface can be faithfully transferred by extrusion lamination, so that an optical sheet having high optical properties such as a light diffusion function can be manufactured with good productivity. material. In particular, according to the interlayer extrusion lamination method, the strength of the optical sheet forming mold is ensured by the substrate sheet for the mold, and the transfer property or heat resistance of the surface shape of the optical sheet original sheet or the synthetic resin layer for the mold can be emphasized. The synthetic resin constituting the synthetic resin layer for a mold is selected from the peeling property of the synthetic resin layer for an optical layer, etc., and contributes to the precise shape of the surface shape of the produced optical sheet or the long life of the optical sheet forming mold. .

Further, according to the above-described manufacturing method using the extrusion layer method, the mold having the reverse shape of the microlens array 5 having the back surface formed by the plurality of microlenses 6 having a random diameter can be easily obtained, for example, by the following means. Manufacture: A light-diffusing sheet formed by coating beads having various diameters is used as a master and transferred or the like.

According to the above manufacturing method, the microlens array 5 of any shape can be easily and surely formed. Therefore, the diameter (D), the height ratio (H/R), the interval ratio (S/D), the filling ratio, and the like of the microlens 6 constituting the microlens array 5 can be easily and surely adjusted, and as a result, it can be easily and surely obtained. The optical function of the lenticular sheet 2 is controlled.

The microlens sheet 2 has an optical function such as high light diffusion by the microlens array 5, and the optical function can be easily and surely controlled. Therefore, the lenticular sheet 2 can control the peak direction of the incident light toward the 稜鏡 sheet 3 to be the inclination angle most suitable for the refracting toward the normal direction side.

Further, the microlens sheet 2 may have an anti-adhesion layer on the surface (the side in contact with the crucible sheet 3). By providing the anti-adhesion layer, adhesion of the microlens sheet 2 to the enamel sheet 3 can be prevented.

The anti-adhesion layer is composed of a binder and beads dispersed in the binder. The binder is formed by hardening a polymer composition containing a base polymer. The beads are disposed at substantially equal density on the surface of the substrate layer by the binder. In addition, the thickness of the anti-adhesion layer (the thickness of the binder portion excluding the beads) is not particularly limited, and may be, for example, 1 μm or more and 10 μm or less.

The base polymer is not particularly limited, and examples thereof include an acrylic resin, a polyurethane, a polyester, a fluorine resin, a polyoxyn resin, a polyamidimide, an epoxy resin, and an ultraviolet ray. A curable resin or the like may be used alone or in combination of two or more. In particular, as the base polymer, a polyol having a high workability and being easily formed into an anti-adhesion layer by a method such as coating is preferable. Further, since the base polymer used for the adhesive is required to transmit light, it is set to be transparent, and particularly preferably colorless and transparent.

The above polyol is preferably, for example, (a) a polyester polyol obtained under conditions in which a hydroxyl group is excessive, (b) a monomer component obtained by containing a hydroxyl group-containing unsaturated monomer, and having a (meth) acrylonitrile group. An acrylic polyol such as a unit. The polyester polyol or the acrylic polyol is used as a binder of the base polymer, and the weather resistance is high, and yellowing of the anti-adhesion layer can be suppressed. Further, the polyester polyol and the acrylic polyol may be used alone or in combination.

Further, in addition to the base polymer, the polymer composition for forming the binder may be, for example, a fine inorganic filler, a hardener, a plasticizer, a dispersant, various homogenizers, an antistatic agent, and ultraviolet rays. Absorbents, antioxidants, viscous modifiers, lubricants, light stabilizers, etc.

As a material of the beads, it is roughly classified into an inorganic filler and an organic filler. As the inorganic filler, specifically, cerium oxide, aluminum hydroxide, aluminum oxide, zinc oxide, cerium sulfide, magnesium citrate or a mixture thereof may be used. As a specific material of the organic filler, an acrylic resin, an acrylonitrile resin, a polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamine or the like can be used. Among them, an acrylic resin having high transparency and preventing transmission of light is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

The lower limit of the average particle diameter of the beads is preferably 1 μm, particularly preferably 2 μm, and more preferably 5 μm, and the upper limit of the average particle diameter is preferably 50 μm, particularly preferably 20 μm, and particularly preferably 15 μm. If the average particle diameter of the beads is less than the above lower limit, the convex portion of the surface of the anti-adhesion layer formed by the beads may become small, and a sufficient anti-adhesion effect may not be obtained, and if the average particle diameter of the beads exceeds the above At the upper limit, the thickness of the microlens sheet may increase, and there may be damage to other optical members that overlap on the back side.

If the amount of the beads is set to a relatively small amount, the beads are dispersed away from each other and dispersed in the binder, and most of the beads are protruded from the binder in a very small amount at the lower end. Therefore, when the microlens sheet is laminated with the light guide plate, the lower end of the protruding bead is in contact with the surface of the light guide plate or the like, and the entire surface of the back surface of the microlens sheet is not in contact with the light guide plate or the like. Thereby, adhesion of the microlens sheet to the light guide plate or the like is prevented, and unevenness in brightness of the screen of the liquid crystal display device is suppressed.

The method for forming the anti-adhesion layer includes, for example, the steps of: (a) producing a coating liquid for an anti-adhesion layer by mixing beads in a polymer composition constituting the binder; and (b) The anti-adhesive layer coating liquid is applied to the back surface of the base material layer 4 to laminate an anti-adhesion layer.

Further, the anti-adhesion layer is not limited to the above-described constitution (composed of a binder and beads dispersed in the binder) and a forming method, and may be roughened by using a surface formed with one of the substrate layers 4. Set for surface processing. By forming such an anti-adhesion layer by such integral molding, the manufacturing steps can be shortened, and mass production can be performed industrially.

The enamel sheet 3 includes a sheet-like base material layer 7 and a projection row composed of a plurality of ridge portions 8 on the surface of the base material layer 7. In order to prevent the embossing generated when the plurality of sheets are overlapped, the projections formed by the plurality of ridges 8 are preferably not formed completely parallel and equally spaced, but are formed at staggered intervals. The spurs are 8 The enamel sheet 3 has a high refractive function toward the normal side and a wide angle light diffusing function by a projection row composed of a plurality of ridge portions 8 provided on the surface. Further, the base material layer 7 is the same as the base material layer 4 of the above-described microlens sheet 2.

Since the ridge portion 8 is required to transmit light, it is formed of a transparent, particularly colorless, transparent synthetic resin. Specifically, the same synthetic resin as the above-mentioned base material layer 4 is used. Further, similarly to the above-described microlens array 5, the lower limit of the refractive index of the material constituting the ridge portion 8 is preferably 1.3, particularly preferably 1.45, and the upper limit is preferably 1.8, and particularly preferably 1.6.

The ridge portion 8 is a triangular column in which one side faces the surface of the substrate layer 7. The cross-sectional shape in the direction perpendicular to the strip direction of the ridge portion 8 is preferably a right-angled isosceles triangle having an apex angle α of 90° and a bottom angle β of 45°, and the apex angle 9 is in a pan-round state. By thus causing the apex angle 9 of the ridge portion 8 to be in a pan-round state, the angle of refraction of the light emitted from the optical unit 1 toward the normal direction is reduced, so that the amount of light emitted toward the front direction can be increased. , so that the front brightness is increased. On the other hand, the light that is incident on the stencil sheet 3 non-perpendicularly is diffused at a wide angle by the ridge portion 8, so that the brightness in the oblique direction can be improved.

The lower limit of the width (W) of the bottom surface of the ridge portion 8 is preferably 10 μm, particularly preferably 30 μm. On the other hand, the upper limit of the width (W) is preferably 1000 μm, particularly preferably 400 μm. The reason for this is that if the width (W) of the bottom surface of the ridge portion 8 is smaller than the lower limit, the formation of the ridge portion 8 is difficult, and if the width (W) of the bottom surface of the ridge portion 8 is exceeded, The above upper limit may cause glare, uneven brightness, and the like.

The lower limit of the ratio of the radius of curvature of the apex angle 9 to the width (W) of the bottom surface of the ridge portion 8 (the radius of curvature ratio) is preferably 1/100, particularly preferably 1/30. On the other hand, the radius of curvature is preferably 1/2, and particularly preferably 1/6. The reason is that if the radius of curvature ratio of the vertex angle 9 is less than the lower limit, the decrease in the refraction angle of the light emitted toward the normal direction is small, and the front luminance is decreased. Conversely, if the curvature radius ratio is greater than the upper limit, the edge may be edged. The optical function of the lens material, in particular, the light diffusion function is lowered, and the light diffusibility toward a wide angle is lowered.

The method for producing the enamel sheet 3 is not particularly limited as long as the above-described structure can be formed, and a method of forming the ridge portion 8 after the base layer 7 is formed, and the base layer 7 and the ridge portion can be used. 8 integrated method, specifically:

(a) a method of laminating a synthetic resin on a sheet mold having an inverted shape of the surface of the enamel sheet 3, and peeling the sheet mold to form the enamel sheet 3;

(b) an injection molding method in which a molten resin is injected into a metal mold having an inverted shape of the surface of the tantalum sheet 3;

(c) a method of reheating the sheet-formed resin and sandwiching it between the same metal mold and the metal plate as described above, and pressing to transfer the shape;

(d) a sheet forming method in which a roll mold having a reversed shape of the surface of the enamel sheet 3 and a nip of the other rolls are passed through a molten state on the circumferential surface, and the shape is transferred and extruded;

(e) applying an ultraviolet curable resin to the base material layer, pressing against a sheet mold, a metal mold or a roll mold having the same reverse shape as described above, and irradiating the uncured ultraviolet curable resin to a shape a method of hardening an ultraviolet curable resin by ultraviolet rays;

(f) A method of applying a uncured ultraviolet curable resin to a metal mold or a roll mold having the same reverse shape as described above, and laminating the base material, and smoothing the ultraviolet curable resin by irradiating ultraviolet rays ;and

(g) A method of using an electron beam curable resin instead of the ultraviolet curable resin.

The optical unit 1 enhances the optical function such as light diffusion at a wide angle by the microlens sheet 2 having the microlens array 5 on the back surface, and the ruthenium sheet 3 lifts the refraction toward the normal side, thereby The sheet combination of the sheets enables an optical unit having a high front luminance and a wide viewing angle. Further, by adjusting the coefficient of variation of the average diameter or diameter of the microlenses, the optical function can be easily and surely controlled, so that the front luminance of the optical unit and the light diffusibility toward the wide angle can be further improved.

The edge-lit backlight unit 10 shown in FIG. 3 includes a light guide plate 11 and a lamp 12 disposed on a side end surface of the light guide plate 11, and the optical unit 1 is disposed to overlap the surface side of the light guide plate 11. At this time, the side end surface of the light guide plate 11 on which the lamp 12 is disposed is disposed in parallel with the ridge portion 8 of the optical unit 1.

As the light guide plate 11, a known one can be used. The thickness (average thickness) of the light guide plate 11 is not particularly limited, and is, for example, 100 μm or more and 10 mm or less, and preferably 1 mm or more and 8 mm or less. If the thickness of the light guide plate 11 is smaller than the above range, problems such as a decrease in brightness of the backlight unit may occur, and environmental conditions such as use in the automobile may not be tolerated. On the other hand, when the thickness of the light guide plate 11 exceeds the above range, the brightness of the liquid crystal display device may be lowered in the same manner, and the thickness of the backlight unit 10 may be increased to deviate from the requirement for thinning of the liquid crystal display device.

As the lamp 12, a known one used in a usual backlight unit can be used, and an LED (Light Emitting Diode) is preferably used. By using the LED as the lamp 12, high luminance can be obtained with high efficiency and energy, and the backlight unit 10 can be made thinner.

The light emitted from the lamp 12 and emitted from the surface of the light guide plate 11 has a relatively strong peak inclined at a specific angle with respect to the normal direction, but the backlight unit 10 has a higher light diffusion function, etc., and is particularly high. The optical unit 1 such as a variable angle function on the normal direction side can increase the front luminance and diffuse the emitted light at a wide angle. Therefore, according to the backlight unit 10, a high front luminance can be ensured and the high luminance can be ensured at a wide angle, so that a uniform viewing angle with a wide viewing angle and a high luminance can be obtained.

Specifically, according to the backlight unit 10, the luminance in the left and right directions in the direction of the normal direction (front luminance) is 90% or more, suitably 95% or more, and 40 degrees from the front side. When the luminance difference (the difference between the maximum value and the minimum value of the luminance) of 80°) is 10% or less, and suitably 5% or less, the surface uniformity of the emitted light is extremely high.

Further, as the edge-lit backlight unit, not only the side end surface of the light guide plate 11 on which the lamp 12 is disposed is disposed in parallel with the ridge portion 8 of the optical unit 1, but also The case of vertical arrangement. Further, a plurality of lamps 12 may be disposed on two or more side end faces of the light guide plate 11.

[Examples]

Hereinafter, the present invention will be described in detail based on the examples, but the present invention is not limited by the description of the examples.

<Formation of microlens sheet>

A molten polycarbonate resin is laminated on a sheet mold having an inverted shape of the microlens array, and the sheet mold is peeled off, thereby forming a microlens sheet. The microlens sheet formed was formed by an average thickness of 100 μm, an average diameter of the microlenses of 60 μm, and a coefficient of variation of the diameter of the microlens of 50%.

<Formation of sheet metal>

A molten polycarbonate resin was laminated on a sheet mold having an inverted shape of a sheet of sheet material, and the sheet mold was peeled off, thereby forming a sheet of the sheet. The formed ruthenium sheet was formed to have an average thickness of 100 μm and a width of the bottom surface of the ridge portion of the ridge portion of 100 μm.

[Examples]

A light-emitting diode is disposed as a light source on a side end surface of the light guide plate having a thickness of 3 mm. The microlens sheeting is disposed on the surface of the light guide plate such that the microlens array is on the back side (light guide plate side). The enamel sheet is placed on the surface of the lenticular sheet so that the ridge portion becomes the front side and the ridge portion is arranged in parallel with the arrangement side of the light emitting diode. A diffusion sheet (light guide plate/back microlens sheet/surface tantalum sheet) of the example was prepared by disposing a diffusion sheet on the surface of the sheet.

[Comparative Example 1]

In the same manner as in the example, a comparative example was produced except that the gusset material was placed so that the ridge portion was the back side and the other gusset was perpendicular to the ridge portion. 1 backlight unit (light guide plate / back sheet / surface sheet).

[Comparative Example 2]

A comparative example was produced in the same manner as in the example except that the gusset material was placed on the surface side and the other gusset material and the ridge portion were arranged to be orthogonal to the lenticular sheet. 1 backlight unit (light guide plate / surface 稜鏡 sheet / surface 稜鏡 sheet).

[Evaluation]

The luminance of the light emitted from the backlight units of the examples and the comparative examples 1 and 2 was measured in the range of -80 to 80 with respect to the normal direction of the surface side of the backlight unit. The measurement results are shown in Fig. 4 . As shown in FIG. 4, the backlight unit of the embodiment showed uniform brightness in a viewing angle of about 80° of -40° to 40°, and it was found that the brightness was high and the surface uniformity was excellent. On the other hand, the backlight unit of Comparative Example 1 has a relatively wide viewing angle, but includes a decrease in overall luminance including front luminance. Further, in the backlight units of Comparative Example 1 and Comparative Example 2, although the front luminance was high, the luminance was greatly lowered when the viewing angle was shifted from the front.

[Industrial availability]

As described above, the optical unit of the present invention and the backlight unit using the same can disperse light emitted from the lamp and perform high-brightness illumination with a high uniformity of wide viewing angle, and can be applied to a liquid crystal display device. In particular, a direct-view liquid crystal display device, and more particularly a transmissive liquid crystal display device. Moreover, as a use thereof, it is particularly suitable for use in a liquid crystal display device for a car navigation system requiring a wide viewing angle.

1. . . Optical unit

2. . . Microlens sheet

3. . .稜鏡 sheet

4. . . Substrate layer

5. . . Microlens array

6. . . Microlens

7. . . Substrate layer

8. . . Burst

9. . . Top angle

10. . . Backlight unit

11. . . Light guide

12. . . light

20. . . Backlight unit

twenty one. . . light

twenty two. . . Light guide

twenty three. . . Optical unit

twenty four. . . Light diffusing sheet

25. . .稜鏡 sheet

30. . . Backlight unit

31. . . light

32. . . Light guide

33. . . Optical unit

34. . .稜鏡 sheet

35. . .稜鏡 sheet

D. . . diameter

H. . . height

R. . . Radius of curvature

S. . . Inter-lens distance

W. . . width

α. . . Top angle

β. . . Bottom angle

Fig. 1 is a schematic cross-sectional view showing an optical unit according to an embodiment of the present invention.

Fig. 2 is a partial bottom plan view showing a microlens sheeting of the optical unit of Fig. 1.

3 is a schematic perspective view showing a backlight unit including the optical unit of FIG. 1.

Figure 4 is a graph showing the brightness of a backlight relative to a viewing angle.

Fig. 5 is a schematic perspective view showing a conventional conventional edge-lit backlight unit.

Fig. 6 is a schematic perspective view showing a prior backlight unit used in a liquid crystal display device for a car navigation system.

1. . . Optical unit

2. . . Microlens sheet

3. . .稜鏡 sheet

4. . . Substrate layer

5. . . Microlens array

6. . . Microlens

7. . . Substrate layer

8. . . Burst

9. . . Top angle

D. . . diameter

H. . . height

R. . . Radius of curvature

S. . . Inter-lens distance

W. . . width

α. . . Top angle

β. . . Bottom angle

Claims (9)

An optical unit comprising a microlens sheet and a tantalum sheet disposed on a surface side of the microlens sheet, wherein the optical unit is disposed on a surface side of a light guide plate of a backlight unit of the liquid crystal display device, the microlens The sheet has a microlens array composed of a plurality of microlenses on the back surface, and the enamel sheet has a protrusion row composed of a plurality of ridges on the surface. The optical unit according to claim 1, wherein the microlens in the microlens sheet has an average diameter of 10 μm or more and 200 μm or less. The optical unit according to claim 1, wherein a coefficient of variation of a diameter of the microlens in the microlens sheet is 30% or more and 100% or less. The optical unit according to claim 1, wherein the material constituting the microlens array in the microlens sheet has a refractive index of 1.3 or more and 1.8 or less. An optical unit according to claim 1, wherein a polycarbonate resin is used as a material for forming the microlens sheet. The optical unit of claim 1, wherein the arrangement pattern of the microlenses in the microlens array of the microlens sheet is a random pattern. The optical unit of claim 1, wherein the ridge portion has a triangular column shape and the apex angle is a pan-round state. A backlight unit for a liquid crystal display device, wherein a light emitted from a lamp is dispersed and guided to a surface side, and is characterized in that: a light guide plate, a lamp disposed on a side end surface of the light guide plate, and The optical unit of claim 1 of the surface side of the light guide plate. The backlight unit of claim 8 is used for a liquid crystal display device for a car navigation system.