KR20100088570A - Optical sheet for liquid crystal display apparatus and backlight unit using the same - Google Patents

Abstract

PURPOSE: An optical sheet for liquid display device and a back light unit using the same are provide to densely arrange micro lens, thereby improving optical functions such as a light concentrating function of the optical sheet for liquid display device, a light diffusing function, and an angel change function and other related functions. CONSTITUTION: A micro lens array(3,4) comprises a plurality of micro lenses(5,6). The plurality of micro lens is formed on a surface and a rear side of a transparent base layer(2). An average radius of each micro lens is over 3μm and below 90μm. The average radius of each micro lens of the rear side is over 2μm and below 24μm. The average radius of each micro lens of the rear side is over 1/12 and below 1 of the average radius of each micro lens of the surface.

Description

Optical sheet for liquid crystal display device and backlight unit using the same {OPTICAL SHEET FOR LIQUID CRYSTAL DISPLAY APPARATUS AND BACKLIGHT UNIT USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical sheet having various functions such as condensing, light diffusion, and refraction of light rays in the normal direction, and particularly suitable for a backlight unit for a liquid crystal display device, and a backlight unit using the same.

Background Art [0002] A liquid crystal display device is widely used with a backlight system that projects a liquid crystal layer from the back side, and a backlight unit such as an edge light type (side light type) or a direct type is provided on the lower surface side of the liquid crystal layer. Such an edge light type backlight unit 40 generally has a rod-shaped lamp 41 as a light source, and a rectangular plate disposed so as to follow an end portion of the lamp 41, as shown in Fig. 9A. A light guide plate 42 having a shape and a plurality of optical sheets 43 stacked on the surface side of the light guide plate 42 are provided. This optical sheet 43 has specific optical functions such as refraction and light diffusion, and specifically, (1) a microlens arranged on the surface side of the light guide plate 42 and mainly having a light diffusion function and a light condensing function. The sheet 44, (2) The prism sheet 45 etc. which are arrange | positioned at the surface side of the micro lens sheet 44 and mainly have a refractive function to a normal line direction side correspond.

Referring to the function of the backlight unit 40, first, the light rays incident on the light guide plate 42 from the lamp 41 are reflected on the reflection dots or reflection sheets (not shown) and the respective side surfaces of the light guide plate 42. It is emitted from the light guide plate 42 surface. Light rays emitted from the light guide plate 42 are incident on the micro lens sheet 44, and are diffused and emitted from the micro lens interface provided on the surface. Thereafter, the light rays emitted from the micro lens sheet 44 enter the prism sheet 45 and are emitted by the prism portion 46 formed on the surface as light rays of a distribution showing peaks in the direction substantially upward. The backlight unit 40 is thus refracted so that the light rays emitted from the lamp 41 are diffused by the optical sheet 43 and exhibit a peak in the direction immediately above, and also the entire liquid crystal layer not shown upward. To illuminate.

In addition, although not shown, in view of the light guide characteristics of the light guide plate 42 described above, the optical function of the optical sheet 43, and the like, a backlight unit in which more optical sheets 43 such as a microlens sheet and a prism sheet are arranged in an arrangement. There is also.

As the conventional microlens sheet 44, as shown in Fig. 9B, a microlens array 47 composed of a plurality of microlenses is generally provided on the surface, and the rear surface has a planar shape. See, for example, Japanese Patent Laid-Open No. 2004-191611 and the like. In this microlens interface provided on the surface of the microlens sheet, the light rays emitted from the lamp are condensed toward the front side, diffused, and inclined toward the normal direction.

However, since optical functions such as light condensing, light diffusion, and angle of incidence of this microlens sheet are determined by the surface shape and the refractive index, there is a certain limit to the function improvement. In particular, in the direct type backlight, there is a problem that when the light diffusion function of the optical sheet is not sufficient, the effect of erasing the lamp image is small and the lamp image appears on the surface of the liquid crystal screen. Therefore, in the conventional backlight unit 40, although it is expensive and difficult to handle, it is necessary to provide a plurality of optical sheets. When a plurality of optical sheets are provided in this manner, there is a problem that the luminance of the liquid crystal display is lowered, and the thickness of the backlight unit is hindered.

Japanese Patent Publication No. 2004-191611

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and an optical sheet for a liquid crystal display device having a particularly high optical function, in particular, a light diffusing function, and a backlight for promoting the improvement of quality such as proper viewing angle, erasure of a lamp image, and thinning using the same The purpose of the unit is to provide.

The invention made to solve the above problems,

A transparent substrate layer,

Micro lens array which consists of several micro lens formed in the surface and back surface of this base material layer

It is an optical sheet for liquid crystal display devices provided with.

Since the optical sheet for liquid crystal display devices includes not only the front surface but also the rear surface, the microlens array can be refracted and diffused from the backlight also at the interface of the rear surface of the optical sheet for liquid crystal display device. Accordingly, the optical sheet for liquid crystal display device can refract and diffuse the light rays from the backlight at the interfaces on both sides of the front and back, and the optical functions such as the light diffusion function are particularly high. Moreover, according to the optical sheet for liquid crystal display devices, since light rays are refracted and diffused by refraction at the interfaces on both sides of the front and back, the loss of the light rays in the optical sheet for liquid crystal display devices can be suppressed to a minimum and the light transmittance can be increased. .

The micro lens on the back surface may be a concave lens. When the microlens on the back surface is a concave lens, when light rays from the backlight enter the back surface of the optical sheet, they are refracted and diffused in the direction in which the light rays are dispersed at the interface. Therefore, according to the said optical sheet for liquid crystal display devices, optical functions, such as a light-diffusion function, become further high.

It is preferable that the microlens array on the back side is made up of a plurality of microlenses having a random diameter. According to the optical sheet for liquid crystal display devices in which the microlenses on the rear surface have a random diameter, the direction and angle at which the light rays from the backlight are refracted and diffused on the rear surface of the optical sheet become random, so that the light diffusion function is more. It becomes further higher, and the uniformity of brightness | luminance and the erasing property of a lamp image are promoted.

The average radius of the microlenses on the surface may be 3 µm or more and 90 µm or less, and the average radius of the microlenses on the rear surface may be 2 µm or more and 60 µm or less. According to the optical sheet for liquid crystal display device, the microlenses on the front and rear surfaces have an average radius in the above range, whereby optical functions such as light diffusion are further enhanced and control of the optical functions can be easily and surely performed. Can be.

The average radius of the microlens on the back surface may be 1/12 or more and 1 or less of the average radius of the microlens on the surface. According to the said optical sheet for liquid crystal display devices whose average radius ratio of a microlens of a back surface and a surface is the said range, the light-diffusion effect can be heightened further by the synergistic effect of the microlens of both surfaces.

The base material layer and the microlens array of the front surface and the back surface of this base material layer should just be formed integrally. Since the optical sheet is integrally formed in this way, the light transmittance and brightness can be increased by minimizing the loss of light without refraction and scattering of light inside the sheet.

It is preferable that the arrangement pattern of microlenses in at least the surface microlens array is an equilateral triangle lattice pattern or a random pattern. Since this equilateral triangle grating pattern can arrange microlenses more densely, the lens filling rate of the optical sheet for liquid crystal display device is easily increased, and optical functions such as condensing and light diffusion are significantly improved. Moreover, by arranging microlenses in a random pattern, the occurrence of moiré is reduced when the optical sheet for liquid crystal display device is superimposed with other optical members.

The liquid crystal display by an extrusion sheet molding method using an embossing roll having an inverted shape of the microlens array on the surface and an embossing roll disposed in parallel with the embossed roll and having an inverted shape of the microlens array on the back surface. The optical sheet for apparatus should just be formed. According to the said means, the optical sheet which has a predetermined | prescribed micro lens array on both surfaces can be shape | molded easily and with high precision, and can also be integrally formed from the same material easily.

Therefore, in the backlight unit for a liquid crystal display device which disperses the light beam emitted from the lamp and guides the light beam leading to the surface side, the optical sheet for the liquid crystal display device having a particularly high optical function, particularly a light diffusion function and its control function is provided. The quality is improved by the unification and enhancement of luminance.

Here, the "surface" and "the back surface" of the optical sheet for liquid crystal display devices are the "surface" and the surface which faces the surface (liquid crystal layer side) normally when the optical unit for liquid crystal display devices is equipped in the backlight unit of a liquid crystal display device. The surface on the opposite side (light guide plate side) is referred to as "back side". "Microlens" is a concept including a convex lens and a concave lens. The term "equilateral triangle lattice pattern" means a pattern in which a surface is divided into equilateral triangles of the same shape, and micro lenses are arranged at each vertex of the equilateral triangle.

As described above, according to the optical sheet for liquid crystal display of the present invention, the optical function, in particular, the light diffusion function is particularly high, and the control of the optical function is easy and reliable. In addition, the backlight using the optical sheet for liquid crystal display device promotes the improvement of the quality of the viewing angle, the elimination of the lamp image, the thinning, and the like, and the reduction of the cost.

1 is a schematic partial cross-sectional view showing an optical sheet for a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a backlight unit including an optical sheet for a liquid crystal display of FIG. 1. FIG.
FIG. 3 is a schematic partial cross-sectional view showing an optical sheet for a liquid crystal display device according to a form different from that of the optical sheet for liquid crystal display device of FIG. 1.
4 is a schematic partial cross-sectional view showing an optical sheet for a liquid crystal display device different from the optical sheet for a liquid crystal display device of FIGS. 1 and 3.
FIG. 5 is a schematic partial cross-sectional view showing an optical sheet for a liquid crystal display device different from the optical sheet for a liquid crystal display device of FIGS. 1, 3, and 4.
6 is a lamp image photograph when the optical sheet for liquid crystal display device of the comparative example is incorporated into the direct type backlight unit;
7 is a lamp image photograph when the optical sheet for liquid crystal display device of Example 2 is incorporated into a direct type backlight unit;
8 is a lamp image photograph when the optical sheet for liquid crystal display device of Example 4 is incorporated in a direct type backlight unit;
9 (a) and 9 (b) are schematic perspective views showing a general backlight unit and a schematic cross-sectional view showing a conventional general micro lens sheet.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings suitably.

The optical sheet 1 for liquid crystal display device of FIG. 1 has the base material layer 2, the microlens array 3 formed in the surface of this base material layer 2, and the micro | microscope formed in the back surface of the base material layer 2 The lens array 4 is provided.

Since the base material layer 2 needs to transmit light, it is formed with transparent, especially colorless and transparent synthetic resin. It does not specifically limit as a synthetic resin used for this base material layer 2, For example, polyethylene terephthalate, polyethylene naphthalate, an acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather-resistant vinyl chloride, a radiation curable resin Etc. can be mentioned. Among them, radiation curable resins such as ultraviolet curable resins and electron beam curable resins excellent in formability of the microlens arrays 3 and 4, and thermoplastic resins such as polycarbonates and polyolefins are preferable.

Although the thickness (average thickness) of the base material layer 2 is not specifically limited, For example, 10 micrometers or more and 500 micrometers or less, Preferably they are 35 micrometers or more and 250 micrometers or less, Especially preferably, they are 50 micrometers or more and 188 micrometers or less. If the thickness of the base material layer 2 is less than the said range, when it exposes to heat in a backlight unit etc., it will become easy to generate | occur | produce a problem, such as difficulty in handling. On the contrary, when the thickness of the base material layer 2 exceeds the said range, the brightness | luminance of a liquid crystal display device may fall, and also the thickness of a backlight unit may become large, and it is against the request of thickness reduction of a liquid crystal display device.

You may contain a micro inorganic filler in the polymer resin which forms the base material layer 2. Thus, by containing a micro inorganic filler in the base material layer 2, the heat resistance of the base material layer 2 and the optical sheet 1 for liquid crystal display devices improves. Although it does not specifically limit as an inorganic substance which comprises this micro inorganic filler, An inorganic oxide is preferable. This inorganic oxide is defined as various oxygen-containing metal compounds in which metal elements mainly form a three-dimensional network through bonding with oxygen atoms. As the metal element constituting the inorganic oxide, for example, an element selected from Groups 2 to 6 of the Periodic Table of the Elements is preferable, and an element selected from Groups 3 to 5 of the Periodic Table of the Elements is more preferable. In particular, an element selected from Si, Al, Ti, and Zr is preferable, and colloidal silica, in which the metal element is Si, is most preferred as the micro-inorganic filler in terms of heat resistance improvement effect and uniform dispersibility. Moreover, the shape of a micro inorganic filler should just be arbitrary particle shapes, such as spherical shape, needle shape, plate shape, scale shape, and crushing shape, and is not specifically limited.

As a minimum of the average particle diameter of a micro inorganic filler, 5 nm is preferable and 10 nm is especially preferable. On the other hand, as an upper limit of the average particle diameter of a micro inorganic filler, 50 nm is preferable and 25 nm is especially preferable. This is because if the average particle diameter of the micro inorganic filler is less than the above range, the surface energy of the micro inorganic filler becomes high, and aggregation or the like tends to occur. On the contrary, if the average particle diameter exceeds the above range, the base layer is clouded under the influence of short wavelength. It is because transparency of 2) falls and affects a transmittance | permeability.

Moreover, what is necessary is just to contain an antistatic agent in the base material layer 2. Thus, by forming the base material layer 2 from the polymer resin in which the antistatic agent was kneaded, the antistatic effect is exhibited in the said optical sheet 1 for liquid crystal display devices, and it is difficult to suck dust and to superimpose with another optical sheet etc. It is possible to prevent a problem caused by the charging of static electricity such as deterioration. In addition, when the antistatic agent is coated on the surface, stickiness and fouling of the surface are generated. However, by mixing the antistatic agent in the base material layer 2 as described above, such harmful effects are reduced. The antistatic agent is not particularly limited, and for example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycols, and polyoxyethylene sorbitan mono Nonionic antistatic agents, such as stearic acid ester and ethanol amide, polymeric antistatic agents, such as polyacrylic acid, etc. are used. Among them, a cationic antistatic agent having a relatively high antistatic effect is preferable, and the addition of a small amount results in an antistatic effect.

Moreover, what is necessary is just to contain a ultraviolet absorber in the base material layer 2. Thus, by forming the base material layer 2 containing a ultraviolet absorber, an ultraviolet cut function is provided to the said optical sheet 1 for liquid crystal display devices, the trace amount ultraviolet-ray emitted from the lamp of a backlight unit is cut, Destruction of the liquid crystal layer can be prevented.

It is also possible to use an ultraviolet stabilizer (including a base polymer having an ultraviolet stabilizer bonded to the molecular chain) instead of or in combination with the ultraviolet absorbent. This ultraviolet stabilizer deactivates radicals, active oxygen, and the like generated in ultraviolet rays, thereby improving ultraviolet stability, weather resistance, and the like. As this ultraviolet light stabilizer, a hindered amine ultraviolet light stabilizer having high stability against ultraviolet rays is suitably used. Moreover, by using together an ultraviolet absorber and an ultraviolet stabilizer, the prevention of deterioration by ultraviolet rays and weather resistance improve especially.

The micro lens array 3 is composed of a plurality of micro lenses 5 having approximately the same diameter.

The microlens array 4 is composed of a plurality of microlenses 6 having a random diameter. In the microlens array 4, many microlenses 6 are formed relatively densely in a random pattern.

The micro lens arrays 3 and 4 may be integrally molded with the base material layer 2 or may be molded separately from the base material layer 2. Since the microlens arrays 3 and 4 need to transmit light, they are formed of a transparent resin, in particular a colorless transparent synthetic resin, and specifically, the same synthetic resin as that of the substrate layer 2 is used. As the base material layer 2, a polyethylene terephthalate film, a polyethylene naphthalate film or a polycarbonate film may be used, and microlenses 5 and 6 may be formed thereon with an ultraviolet curable resin or the like.

Moreover, a filler, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersing agent, etc. may be mix | blended with the base material layer 2 and the microlenses 5 and 6 besides the above-mentioned synthetic resin.

The microlens 5 is a so-called convex lens having a convex, partially spherical shape. As an average radius of the microlens 5, 3 micrometers or more and 90 micrometers or less, especially 10 micrometers or more and 75 micrometers or less are preferable. If the average radius of the microlenses 5 is less than the above range, diffraction may occur in relation to the wavelength of light emitted by the light. On the contrary, if the average radius of the microlens 5 exceeds the above range, there is no sufficient light diffusibility at the interface.

The microlenses 5 are arranged relatively densely and geometrically on the surface of the base layer 2. The microlenses 5 are arranged in an equilateral triangle lattice pattern on the surface of the substrate layer 2. Therefore, both the pitch and the distance between the lenses of the microlens 5 are constant. This array installation pattern can arrange the microlenses 5 most densely, and can improve optical functions such as a light condensing function, a light diffusing function, and a variable function of the optical sheet 1 for a liquid crystal display device.

As a minimum of the filling rate of the microlens 5, 40%, especially 60%, and especially 70% are preferable. Thus, by making the filling rate of the microlens 5 more than the said minimum, the area | region occupied by the microlens 5 in the surface of the optical sheet 1 for liquid crystal display devices is raised, and the optical sheet 1 for this liquid crystal display device is carried out. Optical functions such as light condensing, light diffusion, and the like are significantly improved.

As a minimum of height ratio H / R with respect to the curvature radius R of the lens height H of the microlens 5, 5/8 is preferable and 3/4 is especially preferable. In addition, 1 is preferable as an upper limit of this height ratio (H / R). Here, "lens height" means the vertical distance from the base surface of the micro lens 5 to the outermost part. Thus, by setting the height ratio H / R of the microlens 5 to the above range, the lenticular refraction in the microlens 5 appears effectively, condensing and light of the optical sheet 1 for the liquid crystal display device. Optical functions such as diffusion are significantly improved.

As an upper limit of the spacing ratio S / D with respect to the diameter D of the distance between lenses S; P-D of the microlens 5, 1/2 is preferable and 1/5 is especially preferable. Here, "the distance between lenses" means the shortest distance between adjacent pairs of micro lenses 5. Thus, by making the distance S between lenses of the microlenses 5 below the upper limit, the flat portion which does not contribute to the optical function is reduced, and optical functions such as light condensing and light diffusion of the optical sheet 1 for the liquid crystal display device. This is greatly improved.

It is preferable to make the average of the individual light beam exit angles of the microlens 5 into ± 25 degrees or more with respect to the normal to the optical sheet 1 plane for liquid crystal display devices, and it is especially preferable to set it as ± 40 degrees. By forming the microlens array 3 from the microlens 5 which has such a light emission angle, the viewing angle characteristic required as an optical sheet for liquid crystal display devices can be acquired.

The micro lens 6 is a so-called concave lens having a partially approximately spherical inverted shape. Thus, the microlens 6 of the microlens array 4 provided in the back surface of the base material layer 2 is a concave lens, and the light diffusivity of the said optical sheet 1 for liquid crystal display devices improves especially. That is, according to the optical sheet 1 for liquid crystal display devices, when the light ray from a backlight enters the back surface of the optical sheet 1, the direction in which light rays are dispersed by the concave interface of the microlens 6 Since light is refracted in the direction in which light spreads, light diffusivity is improved.

By forming the microlens arrays 3 and 4 on both surfaces of the optical sheet 1 for the liquid crystal display device as described above, light is diffused by the concave microlens 6 on the back surface where light is incident, thereby providing a wide viewing angle. The front luminance can be maintained by standing the light in the normal direction by the convex micro lens 5 on the surface from which light is emitted. In particular, when the base material layer 2 and the microlens arrays 3 and 4 are integrally formed from the same material, these refractions are performed only at the interface between the front and back of the optical sheet 1 for liquid crystal display device, that is, the liquid crystal. Since the refraction, scattering, etc. of the light inside the optical sheet 1 for a display device do not occur, the loss of the light inside the optical sheet 1 for a liquid crystal display device can be made very small, and the light transmittance and the front luminance can be increased. have.

As an average radius of the microlens 6, 2 micrometers or more and 60 micrometers or less are preferable, especially 6 micrometers or more and 40 micrometers or less. By setting the average radius of the microlenses 6 to the above range, on the microlens array 4 on the rear side of the optical sheet 1 for liquid crystal display device, the direction in which the light rays from the backlight for entering light are dispersed (the direction in which the light spreads). By effectively refracting, light diffusivity is improved. If the average radius of the microlens 6 is less than the above range, diffraction may occur in relation to the wavelength of light emitted by the light. If the average radius of the microlens 6 exceeds the above range, the light diffusing property is not sufficient.

It is preferable that the average radius of the microlens 6 is 1/12 or more and 1 or less of the average radius of the microlens 5. By providing the average radius ratio of the microlens 6 on the back surface and the microlens 5 on the surface in this manner, the light diffusivity can be improved while securing a constant frontal luminance. If the average radius of the microlens 6 is less than 1/12 of the average radius of the microlens 5, the front luminance greatly decreases due to scattering and diffraction phenomena. On the contrary, if the average radius of the microlens 6 exceeds 1, sufficient light diffusivity cannot be obtained. Uniformity is reduced.

As a minimum of the filling rate of the micro lens 6, 50%, especially 70%, and especially 80% are preferable. Thus, by making the filling rate of the microlens 6 more than the said minimum, the occupied area of the microlens 6 on the surface of the said optical sheet 1 is raised, light diffusion of the optical sheet 1 for this liquid crystal display device, etc. The optical function of is greatly improved.

As a manufacturing method of the optical sheet 1 for liquid crystal displays, if the thing of the said structure can be formed, it will not specifically limit, Various methods are employ | adopted. As a manufacturing method of the optical sheet 1 for liquid crystal display devices, after forming the base material layer 2, the method of forming the micro lens array 3 and the micro lens array 4 separately, and the base material layer 2 and the micro lens A method of integrally forming the array 3 and the micro lens array 4 is possible, specifically,

(a) a method of forming the optical sheet 1 for a liquid crystal display device by laminating a synthetic resin in a sheet form having an inverted shape of the surfaces of the micro lens arrays 3 and 4 and peeling the sheet form;

(b) an injection molding method in which molten resin is injected into a mold having an inverted shape of the surfaces of the micro lens arrays 3 and 4,

(c) a method of transferring the shape by reheating the sheeted resin and sandwiching it between the metal mold and the metal plate as described above;

(d) an extrusion sheet molding method in which a resin in a molten state is passed between two roll shapes having an inverted shape of the surfaces of the micro lens arrays 3 and 4 on the circumferential surface, and the shape is transferred;

(e) Method of apply | coating UV curable resin to a base material layer, pressing on the sheet | seat type | mold, metal mold | die, or roll shape which has a reverse shape similar to the above, and transferring a shape to uncured ultraviolet curable resin, and irradiating an ultraviolet-ray and hardening an ultraviolet curable resin. ,

(f) a method of filling and applying an uncured ultraviolet curable resin to a mold or roll type having the same reverse shape as described above, pressing the substrate layer to make it uniform, and curing ultraviolet ray curable resin by shooting ultraviolet rays;

(g) Method of using electron beam curable resin instead of ultraviolet curable resin

Etc.

The method of using the roll type in said (d)-(f) is demonstrated below. An embossing roll having an inverted shape of the microlens array 3 on the surface, and an embossing roll arranged in parallel with the embossed roll at a predetermined interval and having an inverted shape of the microlens array 4 on the surface are used. By passing the film-like resin between these two emboss rolls, the microlens array 3 is formed on the surface and the microlens array 4 is integrally formed on the back surface. According to this method, the sheet having the predetermined micro lens arrays 3 and 4 can be molded easily and with high precision, and can also be integrally formed from the same material. Moreover, since it is shape | molded by the emboss roll, the discontinuous joint part does not arise in the micro lens arrays 3 and 4, and a seamless optical sheet can be manufactured.

The film resin passed between the two emboss rolls may be a molten resin, or an uncured resin may be laminated on both sides of the sheet-like resin, but the molten thermoplastic resin is extruded from the T die into a film. desirable. Thus, by manufacturing by the so-called extrusion sheet molding method, since the resin extruded in the molten state can be molded into an emboss roll, it is possible to simultaneously perform film molding and the micro lens arrays 3 and 4 on the front and back surfaces. Therefore, this optical sheet can be manufactured easily and efficiently.

As a method for producing a mold (mold, mold, etc.) having the inverted shape of the micro lens arrays 3 and 4, for example, a three-dimensional pattern of spot shapes is formed on a substrate by a photoresist material, and the three-dimensional pattern is formed. It can manufacture by making a microlens array model by curvature by heat fluidization, laminating | stacking a metal layer by the electroplating method on the surface of this microlens array model, and peeling this metal layer.

According to the above production method, the micro lens arrays 3 and 4 of arbitrary shapes are easily and reliably formed. Therefore, the size, filling rate, array installation pattern, and the like of the micro lenses 5 and 6 constituting the micro lens arrays 3 and 4 can be easily and surely adjusted, and as a result, the optical sheet 1 for the liquid crystal display device. The optical function of is easily and surely controlled.

As another manufacturing method of the type | mold (sheet-type etc.) which has the inverted shape of the said microlens array 3 and the microlens array 4, the surface of an optical sheet original is used, using the optical sheet original which has a microlens array shape on the surface. It can manufacture by laminating | stacking a synthetic resin layer for mold | die by the extrusion lamination method in this, and peeling an optical sheet original plate from a synthetic resin layer for mold | die. What is necessary is just to laminate | stack a mold synthetic resin layer between an optical sheet original plate and a mold base material sheet by the sandwich extrusion lamination method also in an extrusion lamination method.

According to the above production method, since the surface shape of the optical sheet original plate having the microlens array shape on the surface can be faithfully transferred by the extrusion laminating method, an optical sheet having high optical performance such as a light diffusion function can be produced with high productivity. have. In particular, according to the sandwich extrusion lamination method, since the strength of the optical sheet forming mold is ensured by the mold base sheet, the synthetic resin constituting the mold synthetic resin layer is used for transferring the surface shape of the optical sheet disc, heat resistance, and the optical layer. It can select by focusing on peelability with a synthetic resin layer, etc., and contributes to the precision part formation of the surface shape of the produced optical sheet material, and the long life of an optical sheet formation type | mold.

Moreover, according to the manufacturing method by the said extrusion lamination method, the shape which has the reverse shape of the microlens array 4 of the back surface which consists of several microlenses 6 which have a random diameter is also coated by coating the beads which have several diameters. It can manufacture easily by making the formed light-diffusion sheet into a base plate, and transferring.

The edge light type backlight unit shown in FIG. 2 is arranged so as to overlap the light guide plate 7, a pair of linear lamps 8 arranged on the right side of the light guide plate 7, and a surface side of the light guide plate 7. The optical sheet 1 for liquid crystal display devices provided is provided. The light rays emitted from the lamp 8 and emitted from the light guide plate 7 surface have a relatively strong peak inclined at a predetermined angle with respect to the normal direction, but according to the backlight unit, the light condensing function toward the front side and the angle of change to the normal direction direction In the function, the liquid crystal display device optical sheet 1 having a conventionally high function and a particularly high light diffusing function achieves uniformity in luminance and is converted into light having a wide viewing angle. Therefore, the backlight unit can reduce the number of equipment required for the optical sheet (bead coating sheet or the like) which has been required in the past, thereby facilitating thinning, high quality and low cost. In addition, the improvement of the luminance is promoted by the reduction in the number of optical sheet equipment. In addition, the edge light type backlight unit may be equipped with four or six lamps 8.

The optical sheet 11 for liquid crystal display device of FIG. 3 is formed in the base material layer 2, the microlens array 3 formed in the surface of this base material layer 2, and the back surface of this base material layer 2. The micro lens array 12 is provided. Since this base material layer and the microlens array 3 are the same as that of the optical sheet 1 for liquid crystal display devices of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The micro lens array 12 is composed of a plurality of micro lenses 13 having approximately the same diameter.

The micro lens 13 is a concave lens. Moreover, it is preferable that the diameter of the micro lens 13 is the same diameter or less than the micro lens 5 which comprises the micro lens array 3 of the surface.

The microlens 13 is arranged relatively densely and geometrically on the back surface of the base layer 2. The microlenses 13 are arranged in an equilateral triangle lattice pattern on the back surface of the base layer 2. Therefore, both the pitch and the distance between the lenses of the microlens 13 are constant. This arrangement pattern can arrange the microlenses 13 most densely, and can improve optical functions such as the light diffusion function of the optical sheet 1 for the liquid crystal display device. In particular, the center of each triangle of the equilateral triangle lattice pattern which arranges so that the center of the micro lens 13 of the back surface may be located on the center of the micro lens 5 of the surface, or comprises the micro lens array 3 of the surface is arranged. By arrange | positioning so that the center of the micro lens 13 of the back surface may be located on top, the synergistic effect of the micro lens array of both front and back sides can be heightened, and optical functions, such as a light-diffusion function, can be improved significantly.

The optical sheet 21 for liquid crystal display devices of FIG. 4 is formed in the base material layer 2, the microlens array 3 formed in the surface of this base material layer 2, and the back surface of this base material layer 2. The micro lens array 22 is provided. Since this base material layer and the microlens array 3 are the same as that of the optical sheet 1 for liquid crystal display devices of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The micro lens array 22 is composed of a plurality of micro lenses 23 having random diameters.

The micro lens 23 is a convex lens. As the average radius of the microlens 23, 2 micrometers or more and 24 micrometers or less, especially 6 micrometers or more and 18 micrometers or less are preferable like the micro lens 6 of the optical sheet 1 for liquid crystal display devices, and the microlens 5 provided in the surface It is preferable that they are 1/12 or more of an average radius, and 1 or less. Moreover, as a minimum of the filling rate of the micro lens 23, 50%, especially 70%, and especially 80% are preferable.

Moreover, what is necessary is just the average focal length of the micro lens 23 to be 1/2 or less of the average thickness of the base material layer 2. According to the microlens 23 having such a focal length, the microlens array formed on the surface after the light rays incident from the rear surface of the optical sheet 21 for liquid crystal display device are refracted at the interface of the microlens array 22 on the rear surface. Since it disperses until it reaches the interface of (3), the light-diffusion function of the optical sheet 21 for liquid crystal display devices can be improved.

The optical sheet 31 for liquid crystal display device of FIG. 5 is formed in the base material layer 2, the microlens array 3 formed in the surface of this base material layer 2, and the back surface of this base material layer 2. The micro lens array 32 is provided. Since this base material layer and the microlens array 3 are the same as that of the optical sheet 1 for liquid crystal display devices of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The micro lens array 32 is composed of a plurality of micro lenses 33 having approximately the same diameter.

The micro lens 33 is a convex lens. The diameter of the microlens 33 is preferably equal to or smaller than the microlens 5 constituting the surface microlens array 3. By setting the diameter of the microlens 33 to a size different from that of the microlens 5 on the front side, the focal length according to the object can be adjusted, and the light diffusion and surface uniformity are achieved by the combination of the microlenses on the front and back surfaces. You can make the sex even higher.

The microlens 33 is arranged relatively densely and geometrically on the back surface of the base layer 2. The microlens 33 is arranged in an equilateral triangle lattice pattern on the back surface of the base layer 2. Therefore, both the pitch of the microlens 33 and the distance between the lenses are constant. This array installation pattern can arrange the micro lenses 33 most densely, and can improve optical functions such as the light diffusion function of the optical sheet 1 for the liquid crystal display device. In particular, the center of each triangle of the equilateral triangle lattice pattern which arranges so that the center of the micro lens 33 of the back surface may be located on the center of the micro lens 5 of the surface, or comprises the surface micro lens array 3 is arranged. By arrange | positioning so that the center of the micro lens 33 of the back surface may be located on top, the synergistic effect of the micro lens array of both front and back sides can be heightened, and optical functions, such as a light-diffusion function, can be improved significantly.

Moreover, the average focal length of the microlens 33 should just be 1/2 or less of the average thickness of the base material layer 2. According to the microlens 33 having such a focal length, the light incident from the rear surface of the optical sheet 21 for liquid crystal display device is refracted at the interface of the microlens array 32 on the rear surface, and then the microlens array on the surface ( Since it disperses until it reaches the interface of 3), the light-diffusion function of the optical sheet 31 for liquid crystal display devices can be improved.

In any of the optical sheets 11, 21, and 31 for the liquid crystal display device, microlens arrays are formed on both surfaces of the optical sheet for liquid crystal display device, and the microlenses 13, 23 are provided on the back surface on which light is incident. Or 33), light can be diffused to obtain uniform luminance and a wide viewing angle, and high front brightness can be maintained by standing the light in the normal direction by the convex micro lens 5 on the surface from which the light is emitted. have.

In addition, the optical sheet for liquid crystal display devices of this invention is not limited to the said embodiment, For example, as an arrangement | positioning pattern of the micro lens of the surface, it is not limited to the said equilateral triangle grating pattern which can be densely charged, and it is a square grating pattern and random Patterns are also possible. According to the random pattern, generation of moiré is reduced when the optical sheet for liquid crystal display device is overlaid with other optical members. It is also possible to provide a microlens array consisting of microlenses of concave lenses on the surface. In the case where the microlens array of the concave lens is provided on the surface, similarly to the case where the microlens array of the convex lens is provided, it has an optical function such as excellent light diffusivity. The microlenses on the front surface and the microlenses on the back surface may be made of materials having different refractive indices, respectively. By forming the microlens made of the refractive index material which differs in surface and back surface in this way, since light refraction arises also in the interface between materials, the light diffusivity and surface uniformity of this optical sheet for liquid crystal displays can be improved.

(Example)

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is described in detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

[Comparative Example]

The optical sheet for liquid crystal display devices in which the microlens array which consists of microlenses of a convex lens was provided on the surface of the transparent polyethylene terephthalate film of thickness 100micrometer was used. The average diameter of the microlenses of the microlens sheet of the comparative example was 60 µm, and the filling rate was 70%.

[Examples 1-4]

On the surface of the 100-micrometer-thick transparent polyethylene terephthalate film, the microlens array which consists of microlenses of a convex lens was provided, and the microlens array of the following shapes was respectively provided in the back surface. The optical sheet for liquid crystal display devices of Example 1 was obtained by providing the microlens array which consists of microlenses which are concave lenses which have a random diameter on the back surface. The optical sheet for liquid crystal display devices of Example 2 was obtained by providing the microlens array which consists of microlenses which are concave lenses which have substantially the same diameter on the back surface. The optical sheet for liquid crystal display devices of Example 3 was obtained by providing the microlens array which consists of microlenses which are convex lenses which have a random diameter on the back surface. The optical sheet for liquid crystal display devices of Example 4 was obtained by providing the microlens array which consists of microlenses which are convex lenses which have substantially the same diameter on the back surface.

In the rear microlens array, the average diameter of microlenses having approximately the same diameter was 60 µm, the average diameter of the microlenses having random diameters was 12 µm, and the filling rate was all 70%.

[Evaluation of characteristic]

These haze values were measured using the optical sheet for liquid crystal display devices of the said Examples 1-4, and the optical sheet for liquid crystal display devices of a comparative example. Such haze value was measured with the haze meter by the Sugashi Kenki Co., Ltd. according to the measuring method prescribed | regulated to JIS-K7136. Moreover, these brightness | luminance half value angles were measured using the optical sheets for liquid crystal display devices of the said Example 2, 4 and a comparative example. Moreover, these sheets were actually integrated in the direct type backlight unit using the optical sheets for liquid crystal display devices of the said Example 2, 4 and a comparative example, and the light diffusivity was evaluated. Evaluation of light diffusivity visually confirms the degree of elimination of the lamp image from the surface side when the backlight is irradiated,

(a) When the lamp image is almost invisible

(b) The lamp image is difficult to see.

(c) When the lamp image is slightly visible

(d) If the lamp image is clearly visible ×

It evaluated as. The results are shown in Table 1 below. Moreover, the lamp image photograph when the optical sheet for liquid crystal display devices of a comparative example is incorporated into a direct backlight unit in FIG. 6, and the lamp when the optical sheet for liquid crystal display devices of Example 2 is incorporated into a direct backlight unit in FIG. An image photograph and a lamp image photograph when the optical sheet for liquid crystal display device of Example 4 is incorporated in the direct type backlight unit are shown in FIG. 8, respectively.

As shown in Table 1, the optical sheets for liquid crystal display devices of Examples 1 to 4 exhibit higher haze values than the optical sheets for liquid crystal display devices of Comparative Examples, which do not include a microlens array on the back surface, that is, high light diffusion. It is shown to have a gender and a wide viewing angle. In comparison with Examples 1 to 4, it is shown that the microlenses on the rear face have a random diameter and have a concave lens shape, which shows a high haze value, that is, a high light diffusivity and a wide viewing angle.

Moreover, as shown in Table 1, the optical sheets for liquid crystal display devices of Examples 2 and 4 have a brightness | luminance half value angle larger than the optical sheet for liquid crystal display devices of the comparative example which does not have a microlens array on the back surface.

In addition, as shown in Table 1 and FIGS. 7 to 9, the optical sheets for liquid crystal displays of Examples 2 and 4 also have high degree of erasure of lamp images. That is, it is shown that the optical sheets for liquid crystal display devices of Examples 2 and 4 have high light diffusivity and wide viewing angle. Further, from the degree of erasure of the lamp image (comparison of Figs. 8 and 9), it is shown that the optical sheet for liquid crystal display device having the concave lens-shaped microlens on the back side has higher light diffusivity and wide viewing angle.

As described above, the optical sheet for liquid crystal display device of the present invention is useful as a component of a backlight unit of a liquid crystal display device, and is particularly suitable for use in a transmissive liquid crystal display device.

1, 11, 21, 31... Optical sheet for liquid crystal display device 2. Substrate layer
3, 4, 12, 22, 32, 47... Micro lens array
5, 6, 13, 23, 33... Microlenses 7, 42... Light guide plate
8, 41... Lamp 40.. Backlight unit
43 ... Optical sheet 44... Micro lens sheet
45... Prism sheet 46... Prism part

Claims (10)

A transparent substrate layer,
Micro lens array which consists of several micro lens formed in the surface and back surface of this base material layer
It is provided, The optical sheet for liquid crystal display devices characterized by the above-mentioned. The optical sheet for liquid crystal display device according to claim 1, wherein the microlens on the rear surface is a concave lens. The optical sheet for liquid crystal display device according to claim 1, wherein the microlens array on the back side is made of a plurality of microlenses having a random diameter. The optical sheet for liquid crystal display device according to claim 1, wherein an average radius of the microlenses on the surface is 3 µm or more and 90 µm or less. The optical sheet for liquid crystal display device according to claim 1, wherein the average radius of the microlenses on the rear surface is 2 µm or more and 60 µm or less. The optical sheet for liquid crystal display device according to claim 1, wherein the average radius of the microlenses on the rear surface is 1/12 or more and 1 or less of the average radius of the microlenses on the surface. The optical sheet for liquid crystal display device according to claim 1, wherein the substrate layer and the microlens arrays on the front surface and the rear surface of the substrate layer are integrally formed. The optical sheet for liquid crystal display device according to claim 1, wherein the arrangement pattern of the microlenses in at least the surface microlens array is an equilateral triangle lattice pattern or a random pattern. The extruded sheet according to claim 1, wherein an embossing roll having an inverted shape of the microlens array on the surface and an embossed roll disposed in parallel with the embossing roll and having an inverted shape of the microlens array on the back surface. It is formed by the shaping | molding method, The optical sheet for liquid crystal display devices characterized by the above-mentioned. In the backlight unit for a liquid crystal display device which disperse | distributes the light beam emitted from a lamp and leads to a surface side,
The optical sheet for liquid crystal display devices of Claim 1 is provided, The backlight unit for liquid crystal display devices characterized by the above-mentioned.

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