JP2009258621A - Lens sheet, optical sheet for display, back light unit using the same, and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet having high luminance and a novel shape for reducing side lobes, an optical sheet united with a function film, to provide an optical function sheet which is laminated in one body together with a diffusion plate, and thin and has high strength and high display quality, to provide a back light unit using the optical function sheet, and to provide a display. <P>SOLUTION: In a lens sheet, a translucent base 2 having an incident surface and a projection surface includes unit lenses 3 arrayed on the projection surface at a constant pitch, the unit lenses 3 are each formed by combining prism lenses having curved portions, and a plurality of columnar projections 4 are formed on the incident surface in one stage or two or more stages. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical sheet used for illumination light path control in an optical display device typified by a flat panel display, a backlight unit using the same, and a display device.

  In recent years, liquid crystal display devices using TFT liquid crystal panels and STN liquid crystal panels have been commercialized mainly for color notebook PCs (personal computers) in the OA field.

  In such a liquid crystal display device, a so-called backlight method in which a light source is arranged on the back side (observer side) of the liquid crystal panel and the liquid crystal panel is illuminated with light from the light source is employed.

  The backlight unit employed in this type of backlight system is roughly divided into a light source lamp such as a cold cathode fluorescent lamp (CCFL), and a flat light guide plate made of acrylic resin having excellent light transmittance. There are a “light guide plate light guide method” (so-called edge light method) that makes multiple reflections, and a “direct type method” that does not use a light guide plate.

  As a liquid crystal display device on which a light guide plate light guide type backlight unit is mounted, for example, the one shown in FIG. 10 is generally known.

  This is provided with a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 at the top, and a light guide plate 79 made of a transparent base material such as a substantially rectangular plate-like PMMA (polymethyl methacrylate) or acrylic on the lower surface side. Is installed, and a diffusion film (diffusion layer) 78 is provided on the upper surface (light emission side) of the light guide plate.

  Further, a scattering reflection pattern portion for efficiently scattering and reflecting the light introduced into the light guide plate 79 in the direction of the liquid crystal panel 72 is provided on the lower surface of the light guide plate 79 by printing or the like. A reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion (not shown).

Further, the light guide plate 79 is provided with a light source lamp 76 at the side end, and further covers the back side of the light source lamp 76 so that the light from the light source lamp 76 can be efficiently incident on the light guide plate 79. Thus, a high-reflectance lamp reflector 81 is provided. The scattering reflection pattern portion is formed by printing, drying, and forming a mixture of white titanium dioxide (TiO ₂ ) powder in a solution such as a transparent adhesive in a predetermined pattern, for example, a dot pattern. The light incident on the light plate 79 is imparted with directivity and guided to the light exit surface side, which is a device for increasing the brightness.

  Furthermore, recently, in order to increase the light utilization efficiency and increase the brightness, as shown in FIG. 13, a prism film (prism layer) having a light condensing function between the diffusion film 78 and the liquid crystal panel 72 is used. ) 74 and 75 are proposed. The prism films 74 and 75 are configured to collect light emitted from the light exit surface of the light guide plate 79 and diffused by the diffusion film 78 on the effective display area of the liquid crystal panel 72 with high efficiency.

However, in the apparatus illustrated in FIG. 10, the control of the viewing angle is left only to the diffusibility of the diffusion film 78, which is difficult to control, and the center in the front direction of the display is bright and becomes darker toward the periphery. This characteristic is inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.
Furthermore, in the apparatus using the prism film illustrated in FIG. 11, two prism films are required, which not only greatly reduces the amount of light due to absorption of the film but also increases the cost due to the increase in the number of members. It was also.

  On the other hand, in the direct type, a display device such as a large liquid crystal TV in which the light guide plate is difficult to use is used.

  As a direct type liquid crystal display device, a device illustrated in FIG. 12 is generally known. In this, a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 is provided on the upper side, and is emitted from a light source 51 made of a fluorescent tube or the like on the lower surface side thereof and diffused by an optical sheet such as a diffusion film 82. The light is condensed on the effective display area of the liquid crystal panel 72 with high efficiency. In order to efficiently use the light from the light source 51 as illumination light, a reflector 52 is disposed on the back surface of the light source 51.

However, even in the apparatus illustrated in FIG. 12, the control of the viewing angle is left only to the diffusibility of the diffusing film 82, which is difficult to control, and the center in the front direction of the display is brighter and darker toward the peripheral part. This characteristic is inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

Therefore, as one solution, as shown in FIG. 14, a brightness enhancement film (BEF), which is a registered trademark of US 3M, shown in FIG. A method of arranging the light diffusion film 84 is employed. Here, BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a transparent member.
This prism has a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” to the viewer, or “recycle”. To do.

When using the display (when observing), the BEF increases the on-axis brightness by reducing the off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the viewer, and is generally on the normal direction side with respect to the display screen.
When the repetitive array structure of prisms is arranged in only one direction, only the direction change or recycling in the parallel direction is possible, and in order to control the luminance of the display light in the horizontal and vertical directions, the parallel direction of the prism groups Are stacked and used in combination so that they are substantially orthogonal to each other.

The adoption of BEF allows display designers to achieve the desired on-axis brightness while reducing power consumption.
As a patent document disclosing that a brightness control member having a repetitive array structure of prisms represented by BEF is adopted for a display, there are many known as exemplified in Patent Documents 1 to 3. Yes.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 In the optical sheet using the BEF as a brightness control member as described above, light from the light source is finally emitted from the film at a controlled angle by refraction. Thus, it is possible to control to increase the light intensity in the visual direction of the viewer.

However, there are unexpected light rays that are unnecessarily emitted laterally without proceeding in the visual direction of the viewer. For this reason, as shown in FIG. 15, the light intensity distribution emitted from the optical sheet using BEF has the light intensity when the viewer's visual direction, that is, the angle with respect to the visual direction F is 0 ° (corresponding to the axial direction). Although most enhanced, there is a problem that a small light intensity peak occurs in the vicinity of ± 90 ° from the front, that is, light (side lobes) emitted from the lateral direction is increased.
A luminance distribution having such a light intensity peak is not desirable, and a smooth luminance distribution having no light intensity peak around ± 90 ° is more desirable.

  In addition, when only the on-axis luminance is excessively improved, the peak width of the luminance distribution curve is remarkably narrowed, and the viewing area is extremely limited. Therefore, in order to increase the peak width appropriately, the prism sheet and There is a problem that it is necessary to newly use a light diffusing film as a separate member, which increases the number of members.

  As described above, this optical sheet is required not only to improve the light utilization efficiency but also to have various functions such as removing unevenness of the light source and securing the viewing area of the display. It is configured by overlapping sheets. However, if the number of optical sheets is large, the work for assembling the display becomes complicated, and there is a problem that it is affected by dust between the optical sheets and hinders miniaturization and thinning.

By the way, in such a liquid crystal display device, light weight, low power consumption, high luminance, and thinning are strongly demanded as market needs, and accordingly, a backlight unit mounted on the liquid crystal display device is also required. Light weight, low power consumption, and high brightness are required.
In particular, in the color liquid crystal display devices that have made remarkable progress in recent years, the panel transmittance of the liquid crystal panel is much lower than that of a monochrome compatible liquid crystal panel, so that the brightness of the backlight unit can be improved. It is essential to obtain low power consumption of the device itself.

However, as described above, it is difficult to say that the conventional apparatus sufficiently satisfies the demand for high luminance and low power consumption, and the user has low price, high luminance, high display quality, and low power consumption. The development of a backlight unit and a display device capable of realizing a power liquid crystal display device is awaited.

As an optical sheet having a high luminance and a reduced number of parts, an optical sheet is proposed in which a lens sheet and a diffusion layer are laminated and integrated using an adhesive layer or an adhesive layer while maintaining a gap. Examples of the method for maintaining the gap include a method in which an adhesive layer or an adhesive layer is formed on the incident surface of the lens sheet, a protrusion is formed on the diffusion layer, and the lens sheet and the diffusion layer are laminated and integrated through the protrusion. In such a method, as shown in FIG. 7A, if the incident surface of the lens sheet is originally smooth, the lens sheet (approximately 1.5 as the refractive index of a general resin material) and air Incident light condensed at about 90 degrees due to the difference in refractive index from (refractive index 1.0) is incident at an angle exceeding 90 degrees when the surface smoothness of the adhesive layer or adhesive layer is poor, and the brightness is reduced. cause. Further, in order to improve the diffusibility of the optical sheet, the adhesive layer or the adhesive layer may contain diffusing particles. In such a case as well, as shown in FIG. Incident light is diffused, and light exceeding 90 degrees is incident, causing a decrease in luminance. In addition, the shape of the protrusion must be a shape that suppresses a decrease in luminance in consideration of the shapeability and mold releasability at the time of molding.
The present invention has been made in view of such circumstances, and the protrusion shape considering the formability and mold releasability and the adhesion between the adhesive layer or the adhesive layer, and the surface of the adhesive layer or adhesive layer is smooth. It is an object of the present invention to provide an optical sheet, a backlight unit using the optical sheet, and a display device that do not cause a decrease in luminance even when there is no diffusion particle or when diffusing particles are included.

In order to achieve the above object, the present invention takes the following measures.
That is, according to the first aspect of the present invention, in the translucent substrate having an entrance surface and an exit surface, at least one type of unit lens is arranged on the exit surface, and the entrance surface has a substantially flat plane portion. And a plurality of protrusions protruding from the flat surface portion.

  According to a second aspect of the present invention, in the lens sheet according to the first aspect, the protrusion is formed in a cylindrical shape having a central axis extending in a direction parallel to the thickness direction of the base material. To do.

  According to a third aspect of the present invention, in the lens sheet according to the first aspect, the cross-sectional area of the protruding portion decreases as the distance from the planar portion increases.

  According to a fourth aspect of the present invention, in the lens sheet according to the first aspect, the projecting portion is constituted by two or more columns having different widths, and the cross-sectional area decreases as the distance from the flat portion increases. .

の範囲で規定されることを特徴とする。 According to a fifth aspect of the present invention, in the lens sheet according to any one of the first to fourth aspects of the present invention, the unit lens has a pitch P0 prism lens having at least one curved side surface in the pitch direction by Δ. It is a compound lens shape that is compounded by shifting,
The shift amount Δ is the following formula:

It is specified in the range of

の範囲で規定されることを特徴とする。 According to a sixth aspect of the present invention, in the lens sheet according to any one of the first to fourth aspects, the unit lenses have a lenticular shape arranged at a constant pitch, and the protrusions are arranged at a constant pitch. The unit lenticular and the arrangement direction of the protrusions are shifted by an angle β,
The angle β is

It is specified in the range of

で規定され、各ピッチＰｉが基本ピッチＰｍの整数倍でランダムに配列されることを特徴とする。 According to a seventh aspect of the present invention, in the lens sheet according to any one of the first to fourth aspects, the arrangement of the protrusions is as follows when the pitch of each protrusion is Pi and the basic pitch is Pm: formula,

Each pitch Pi is randomly arranged at an integral multiple of the basic pitch Pm.

  According to an eighth aspect of the present invention, in the lens sheet according to any one of the first to fourth aspects, the protrusion is formed at a position facing between the pitches of the adjacent unit lenses. And

で規定され、各ピッチＰｉが単位レンズピッチＰｍの整数倍でランダムに配列されることを特徴とする。 The invention according to claim 9 is the lens sheet according to claim 8, wherein the protrusions are arranged such that the pitch of each protrusion is Pi and the pitch of the unit lenses is PL,

Each pitch Pi is randomly arranged at an integral multiple of the unit lens pitch Pm.

  The invention of claim 10 is the lens sheet according to any one of claims 1 to 9, wherein the substrate has a thickness of 50 μm to 500 μm, and the unit lenses of the lens sheet are arranged. S / M is 7% or more and 15% or less, where M is the average distance between two adjacent protrusions scattered on the back surface of the surface, and S is the height of the protrusions. Characteristic lens sheet.

The invention of claim 11 is a diffusing plate that makes light emitted from a light source incident, diffuses the incident light to reduce unevenness in light quantity, and emits diffused light, and any one of claims 1 to 10. An optical sheet comprising at least the exit surface of the diffuser plate and the protrusion formed on the entrance surface of the lens sheet integrally laminated by an adhesive layer or an adhesive layer. is there.

The invention of claim 12 comprises an image display element for defining a display image, a light source on the back of the image display element, and the optical sheet according to claim 11, and a backlight unit for display. It is.

  A thirteenth aspect of the present invention is the display backlight unit according to the twelfth aspect of the present invention, which is incident on one surface of the translucent substrate between the image element and the optical sheet according to the eleventh aspect. And an optical film provided with an uneven shape for diffusing and condensing light.

  A fourteenth aspect of the present invention is the display backlight unit according to the twelfth aspect, wherein the optical film is a prism film, a lenticular film, or a microlens film.

  The invention according to claim 15 is the backlight unit for display according to claim 12, wherein the optical film is a diffusion film in which a resin filler is disposed on one surface of a light-transmitting substrate. The light transmittance is 60 to 80%, and the haze value is 85 to 98%.

  According to a sixteenth aspect of the present invention, there is provided an image display element that defines a display image according to transmission / shielding in pixel units, and a display for the display according to any one of the twelfth to fifteenth aspects, A display device comprising a backlight unit.

  As described above, in the optical sheet according to the present invention, and in the backlight unit and display device using these, a lens having excellent formability and mold releasability, and having good adhesion to the adhesive layer or the adhesive layer Provided are a sheet, an optical sheet in which the lens sheet and the diffusion layer are laminated and integrated using an adhesive layer or an adhesive layer, and does not cause a decrease in luminance, a backlight unit using the optical sheet, and a display device Can do.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 8 is a side view showing an example of the backlight unit and the display device according to the embodiment of the present invention.
First, in the backlight unit according to the embodiment of the present invention, a plurality of cylindrical light sources 41 housed in a lamp house 43 and light H from each light source 41 are sandwiched between polarizing plates 31 and 33. An optical sheet 52 to be supplied to the liquid crystal 35 is provided. In the figure, reference numeral 45 denotes a light reflecting plate disposed on the back side of the plurality of light sources 41. In the drawing, only the optical sheet 52 composed of the diffusion plate 25 and the lens sheet 1 is provided between the light source 41 and the polarizing plate 33. You may combine suitably optical sheets, such as a micro lens sheet, a prism sheet, and a polarization separation reflection sheet.
The display device according to the embodiment of the present invention is a device including the light source 41, the optical sheet 52, and the liquid crystal panel 32 thereon. In this case, the display device is a liquid crystal display device. However, the display device is not limited to this, and any display device that displays an image with light, such as a projection screen device, a plasma display, or an EL display, including the optical sheet 52 described above. Any type.

FIG. 1A is a cross-sectional view illustrating a configuration example of the lens sheet 1. In this lens sheet 1, a unit lens 3 which is a compound curved prism lens is formed on one surface of a translucent substrate 2, and a substantially flat plane portion 102 (incident surface) and a cylindrical projection are formed on the other surface. It consists of part 4.
The unit lens is composed of a curved prism lens shifted by Δ. The range of Δ is set to the above equation (1). If it is smaller than the lower limit, the light condensing effect is small, and if it is larger than the upper limit, side lobes are likely to occur, which is not desirable.
The curved side surface is defined as follows.
In other words, in the lens shape defined by Equation 5, the lens shape is defined by the side surface from the lens end to the point where the inclination angle of the curved surface with respect to the substrate surface is 25 degrees or more and 45 degrees or less.

Equation 5 will be described with reference to FIG. z is a function of r, which is a position variable in the width direction of the unit lens 3, and its value represents the height direction of the unit lens 3. The above formula is a general formula for an aspherical lens shape, where k = 0 is a spherical surface, -1 <k <0 is an ellipse, k = -1 is a paraboloid, k <-1 is a hyperboloid, and 1 / R is r is a coefficient relating to r, and A, B, and C are correction term coefficients.
The prism lens that constitutes the unit lens 3 of the present invention is defined by the side surface of the lens defined by Equation 5 from the lens end to the angle range of 25 degrees to 45 degrees with respect to the substrate. Below 25 degrees, the field of view is wide, but the light condensing effect is low. Conversely, when it is above 45 degrees, the field of view is narrow and side lobes are likely to occur.
Also, from the specified ranges of the coefficients 1 / R, A, B, C in the above formula (−10 <1 / R <10, −5 <A <5, −10 <B <10, −30 <C <30). If it falls off, the light collecting effect cannot be obtained or side lobes are likely to occur. That is, by adjusting the curved shape and the inclination angle, a lens sheet that provides a balance between the light collection effect and the visual field range is provided.

の範囲であることが望ましい。
そして本発明の単位レンズ３と隣り合う単位レンズ３の湾曲側面の接合点、及びプリズムレンズと隣り合うプリズムレンズとの谷間が丸みを帯びることもあり得る。この場合、視野範囲が拡大するとともに、谷部の線が見えづらくなることでモアレ干渉縞のコントラストを低減させる効果が得られる。
本発明におけるレンズシート１は、上記の形状に限定されるものではない。例えば、前記単位レンズ３の湾曲側面が左右非対称である場合や、異なる形状の単位レンズ３が複数配列されてなるレンズシート１もあり得る。更には図４（ａ）に示されるように凸レンズ頂点にＶ溝が形成されたレンズや、図４（ｂ）に示されるように、凸球面（非球面）シリンドリカルレンズ、図４（ｃ）に示されるように三角プリズム等を用いる場合も、本発明の主旨を逸脱するものではない。 It is desirable that the prism lens constituting the unit lens 3 of the present invention has the curved side surface defined above, and its shape is symmetrical. In this case, since the unit lens 3 is bilaterally symmetric, the lens sheet 1 is free of bias in the visual field range.
The tip of the prism lens constituting the unit lens 3 of the present invention may be a straight line instead of a curve. By making it a straight line, the visual field range can be narrowed and the light collection effect can be enhanced.
Further, the prism lens tip may be rounded. By rounding, the field of view is widened and the household budget at the tip can be prevented. However, if the radius of curvature at the tip of the prism lens is too large, the brightness is lowered. Therefore, the radius of curvature R is calculated when the prism lens pitch is P0.

It is desirable to be in the range.
And the junction point of the curved side surface of the unit lens 3 adjacent to the unit lens 3 of the present invention and the valley between the prism lens and the adjacent prism lens may be rounded. In this case, an effect of reducing the contrast of the moire interference fringes can be obtained by expanding the visual field range and making the valley lines difficult to see.
The lens sheet 1 in the present invention is not limited to the above shape. For example, there may be a lens sheet 1 in which the curved side surface of the unit lens 3 is asymmetrical in the left-right direction or a plurality of unit lenses 3 having different shapes are arranged. Furthermore, as shown in FIG. 4A, a lens having a V-groove formed at the apex of the convex lens, as shown in FIG. 4B, a convex spherical (aspheric) cylindrical lens, and in FIG. Even when a triangular prism or the like is used as shown, it does not depart from the gist of the present invention.

As shown in FIG. 7C, the incident surface side of the lens sheet 1 includes a substantially flat plane portion 102 and a projection portion 4 composed of one or a plurality of cylinders. The protrusion 4 is formed in a columnar shape having a central axis extending in a direction parallel to the thickness direction of the lens sheet 1. The protrusion 4 is not limited to a cylinder as shown in FIG. 3 (a), but as shown in FIG. 3 (b), the tip of the cylinder is thin, or as shown in FIG. 3 (c). As shown in FIG. 3 (d), the tip of the cylinder is rounded, as shown in FIG. 3 (d), as shown in FIG. 3 (e), as shown in FIG. 3 (e), as shown in FIG. f) a polygonal shape as shown in FIG. 3 (g), a cylinder composed of two stages as shown in FIG. 3 (g), and a cylinder with a thin tip as shown in FIG. 3 (h). A combination of two stages, as shown in FIG. 3 (i), may be a combination of a cylinder and a microlens. Among these, a shape with a smaller cross-sectional area as the distance from the flat portion 102 decreases is more desirable. When forming the protrusion part 4, since the shaping property and the peelability from a metal mold | die improve, productivity improves.
Further, it is more desirable that the protrusion 4 is formed of a plurality of columns having two or more steps. In this case, when the diffusion layer 25 and the adhesive layer or the adhesive layer 50 are laminated, it is desirable that the second and subsequent columns are integrated in such a manner that they are buried in the adhesive layer or the adhesive layer 50. The peel strength is improved by increasing the bonding area (area where the adhesive layer or adhesive layer 50 and the protrusion 4 are bonded).
As described above, the pressure-sensitive adhesive layer or the adhesive layer 50 is formed by forming the protrusion 4 on the incident surface of the lens sheet 1 that has good shapeability and mold releasability and has good adhesion to the pressure-sensitive adhesive layer or the adhesive layer 50. Even when the surface smoothness and diffusing particles are contained therein, it is possible to provide the optical sheet 52 that does not cause a decrease in luminance.

FIG. 1B is a view of the lens sheet 1 viewed from the exit surface side, and FIG. 1C is a view of the lens sheet 1 viewed from the entrance surface side. Here, the longitudinal direction of the unit lens 3 of the optical sheet 1 is X (hereinafter referred to as the horizontal direction), and the direction orthogonal to the horizontal direction X is V.

The lens sheet 1 described above is incident from the incident surface 102 on which the light transmitted from the light source 41 through the diffusion layer 25 and the gap (air layer) 200 is incident as shown in FIG. The light is emitted as light K having an optical gain of 1 or more.

Here, the optical gain is one of indexes indicating the diffusibility of the optical diffusing member, and is expressed as a ratio to the luminance of the light, assuming that the luminance of the diffuser that completely diffuses is 1. When the diffusivity of the diffusing member to be measured is biased depending on the direction, the diffusion characteristic of the diffusing member can be shown by obtaining the optical gain for each direction.
Also, complete diffusion refers to an ideal diffuser that has zero absorption and a constant intensity in any direction. That is, an optical gain of 1 or more indicates that there is an effect of collecting light in the measurement direction, and that the larger the value, the stronger the light collection effect.

The thickness of the lens sheet 1 is determined by the manufacturing process or the required physical characteristics of the lens sheet 1 rather than the influence on the optical characteristics.
For example, when the unit lens 3 and the protrusion 4 are formed by UV molding, the base material thickness T of the supporting base film is wrinkled when it is 50 μm or less, and thus it is necessary that 50 μm <T.
Furthermore, the thickness of the substrate varies depending on the size of the backlight unit or display device used. For example, in a display device having a diagonal size of 37 inches or more, the substrate thickness T is desirably 0.05 mm to 3 mm.

When the lens sheet 1 of the present invention is used in the form of a film, the substrate thickness T is desirably in the range of 50 um to 500 um.
S / M is preferably 7% or more and 15% or less, where S is the height of the protrusions 4 and M is the average distance of the scattered protrusions 4. Thereby, it is possible to prevent the flat portion 102 of the base material 4 from being rubbed. Therefore, it is possible to wind up with a roll without a protective film, and to stack films after punching, and not only the cost but also the work of peeling off the protective film when assembling the backlight can be omitted. Is greatly improved.
Here, when the S / M is less than 7%, the average distance M of each protrusion 4 is too long with respect to the height S of the protrusion 4, so that the flat portion 102 of the substrate 4 is deformed by the sheet bending. Rub. If the S / M exceeds 15%, too many protrusions 4 are present, so that light leaking from the protrusions increases as will be described later with reference to FIG. .
In addition, you may form such a projection part 4 in the surface where the unit lens of a lens sheet is arranged. That is, the unit lens can be protected by making the height S of the protrusion 4 higher than the height TL of the unit lens.

  The protrusions 4 may be arranged at a pitch Pi. In this case, moire interference fringes may occur between the unit lenses 3 and the pitch PL. Therefore, as shown in FIG. 2A, it is desirable to form the unit lens 3 and the array of the protrusions 4 so as to be shifted by an angle β. The range of β is defined by Equation 2. That is, when the arrangement of the unit lenses 3 and the arrangement of the projections 4 are parallel or perpendicular to each other, the unit lens 3 and the arrangement of the projections 4 are shifted by ± 30 degrees to thereby change the unit lens. Moire interference fringes generated by the arrangement of 3 and the arrangement of the protrusions 4 can be suppressed. Here, when β exceeds 30 degrees, another moire interference fringe is generated in an oblique direction, which is not desirable.

  The arranged protrusions 4 are arranged at a pitch Pi, but as shown in FIG. 2B, this Pi may be changed randomly. For a certain basic pitch Pm, it is defined by Equation 3. That is, a pitch that is an integral multiple of the basic pitch Pm is randomly determined. As a result, the protrusions 4 are arranged in a pseudo-random manner in the space while being arranged, and it is possible to avoid moire interference fringes with the unit lens 3.

As shown in FIGS. 2C and 5, the arranged protrusions 4 may be aligned at positions facing each other between the pitches of adjacent unit lenses 3. As a result, since the pitches of the unit lens 3 and the arrangement of the protrusions 4 are completely the same, moire interference fringes do not occur. Alternatively, the protrusion 4 may be disposed at a position facing the center of the unit lens 3 for the same reason.
The protrusions 4 aligned and aligned with the unit lens 3 in this way are defined by Equation 4. That is, as shown in FIG. 2D, a pitch Pi that is an integral multiple of the unit lens pitch PL may be determined randomly.

Also, in general, many displays have a periodic pixel structure, and as a result, high-order moire such as moire between the respective periodic structures and secondary moire generated in three or more periodic structures is generated and the appearance is impaired. Arise. Therefore, the lenticular direction of the lens sheet 1 may be shifted from the direction of the periodic structure of the display by the angle β shown in Formula 2. Thereby, it is possible to prevent moiré between the horizontal and vertical structures of the periodic pixel structure of the display.

As a method of preventing the above moire, the above moire can be prevented by meandering the unit lens 3.
As another method for preventing moire, there is a method in which the lens pitch of the unit lenses 3 is random. In this case, there are a method of changing the lens height and pitch to be random, a method of making the pitch only random without changing the lens height, and a method of making the shift amount Δ of the prism lens random. From the viewpoint of unevenness in the above, a method of randomizing without changing the height of the lens is desirable, and in that case, the random ratio (pitch increase / decrease ratio with respect to the standard pitch) is desirably 20% or less, and more desirably 10% or less. .

The optical action of the optical sheet 52 of the present invention will be described with reference to FIG. In the figure, the dotted line arrow L1 represents the light incident on the protrusion 4 out of the diffused light emitted from the diffusion layer 25, and the solid line arrow L0 represents the plane part of the diffused light emitted from the diffusion layer 25. Represents light incident on 102. The light L0 incident from the flat portion 102 is deflected by the refractive index difference between the air and the substrate 2 and enters the lens sheet 1. The unit lens 3 is refracted or reflected and deflected by the refractive index difference between the air layer and the unit lens 3 to increase the amount of light in the front direction of the screen. Here, an important point for condensing light in the front direction of the screen is that incident light is deflected by a difference in refractive index between air and the lens sheet 1. Thereby, for example, when the refractive index of the lens sheet 1 is 1.5 as a general resin material value, the diffused light spreading in the direction of 180 degrees is deflected to a range of about 90 degrees. The light deflected in the 90-degree range is further deflected by the unit lens 3 and condensed in the front direction.
A part of the light L1 incident on the protrusion 4 is emitted from the side surface of the protrusion 4 and reenters from the flat surface 102. And a part is totally reflected by the refractive index difference of the side surface of the projection part 4, and air. Due to this effect, the light L1 incident from the protrusion 4 is also deflected to a range of about 90 degrees, further deflected by the unit lens 3, and condensed in the front direction. In general, when the lens sheet 1 and the diffusion layer 25 are laminated and integrated with the adhesive layer or the adhesive layer 50 using ribs or the like, leakage light from the ribs causes a decrease in luminance. Such a decrease in luminance hardly occurs.

The unit lens 3 and the protrusion 4 as described above are molded on the translucent substrate 2 using UV or radiation curable resin, or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl). Methacrylate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc. It is formed by hot press molding.
A light reflecting layer made of, for example, a white pigment may be provided on the surface of the protrusion 4 of the lens sheet 1 thus manufactured. Here, examples of the white pigment include titanium oxide, aluminum oxide, barium sulfate, and the like, which are formed by a printing method or the like.

The diffusion layer 25 includes a transparent resin and transparent particles dispersed in the transparent resin, and the refractive index of the transparent resin and the refractive index of the transparent particles need to be different.
The difference between the refractive index of the transparent resin and the refractive index of the transparent particles is preferably 0.02 or more. If the difference in refractive index is smaller than this, sufficient light scattering performance cannot be obtained.

  The diffusion layer 25 needs to transmit the light H incident on the diffusion layer 25 while scattering the light H. For this reason, the average particle diameter of the transparent particles contained in the diffusion layer 25 is desirably 0.5 to 10.0 μm. Preferably it is 1.0-5.0 micrometers. Alternatively, the diffusion layer 25 has a structure having a fine cavity containing air in the transparent resin, and the diffusion performance may be obtained by the difference in refractive index between the transparent resin and air.

As transparent resin, for example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, PET, polypropylene, polyacrylonitrile copolymer Polymers, acrylonitrile styrene copolymers and the like can be used.

Here, the linear expansion coefficients of polycarbonate, polystyrene, methylstyrene resin, and cycloolefin polymer are 6.7 × 10 ⁻⁵ (cm / cm / ° C.), 7 × 10 ⁻⁵ (cm / cm / ° C.), and 7 respectively. It is * 10 < ^-5 > (cm / cm / degreeC) and 6-7 * 10 < ^-5 > (cm / cm / degreeC). On the other hand, when the lens sheet 1 contains, for example, PET, the linear expansion coefficient of PET is 2.7 × 10 ⁻⁵ (cm / cm / ° C.), and the linear expansion coefficient of the diffusion layer 25 is larger. Accordingly, when the optical sheet 52 receives heat and deforms, warpage occurs on the diffusion layer 25 side.
However, in the embodiment of the present invention, considering that the linear expansion coefficient of the lens sheet 1 is small, the linear expansion coefficient of the diffusion layer 25 is set to 7.0 × 10 ⁻⁵ (cm / cm / ° C.) or less. Thus, the above-described deformation can be prevented.
In addition, when producing the lens sheet 1 using a polycarbonate as a material by the extrusion method, warpage does not occur because the linear expansion coefficient is substantially equal to that of other transparent resins.

Moreover, as transparent particles, transparent particles made of inorganic oxide or transparent particles made of resin can be used. For example, examples of the transparent particles made of an inorganic oxide include particles made of silica, alumina or the like. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and crosslinked melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoro). Examples thereof include fluorine-containing polymer particles such as ethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer), and silicone resin particles. These transparent particles may be used as a mixture of two or more.

And the plate-shaped diffusion layer 25 can be manufactured by disperse | distributing transparent particles in these transparent resins, and extrusion-molding. The thickness is desirably 1 to 5 mm.
If the thickness is less than 1 mm, the diffusion layer 25 is thin and has no defect, so that it has a drawback of bending. On the other hand, if it exceeds 5 mm, there is a drawback that the transmittance of light from the light source 41 is deteriorated.

FIG. 16 is a diagram showing another embodiment of a backlight unit using the optical sheet 52 of the present invention. The difference from the above-described embodiment is that an optical film 400 is installed between the optical sheet 52 of the present invention and the liquid crystal panel 32.

The optical film 400 is preferably a prism sheet, a lenticular sheet, or the lens sheet 1 of the present invention. In this case, the arrangement direction of the unit lenses 3 of the lens sheet 1 constituting the optical sheet 52 of the present invention is perpendicular to the prisms and lenticulars constituting the optical film 400, that is, in the X direction as shown in FIG. It is desirable that the prisms be arranged. Since the lens sheet 1 constituting the optical sheet 52 of the present invention is arranged in the V direction, a large light collecting effect is obtained in the V direction, so the optical film 400 is installed in a direction orthogonal to the lens sheet 1. This is because the light collecting effect in the X direction as well as the V direction can be obtained, so that the luminance increases.
Here, the prism and the lenticular may be shifted in the oblique direction from the X direction. This is to suppress the generation of moire interference fringes with the pixels of the display device. However, if the angle to be shifted is too large, the condensing effect in the X direction by the prism and lenticular is weakened, so a range of ± 20 degrees or less is desirable.

  The optical film 400 is preferably a microlens sheet, a quadrangular prism sheet, or a polygonal prism sheet. In this case, since the light collecting effect in multiple directions is obtained, the luminance increases. Here, the microlens sheet may have a perfect circle shape, but may have an elliptical shape. As shown in FIG. 18, in the case of an elliptical shape, the major axis direction L of the elliptical microlens 401 and the direction orthogonal to the arrangement direction of the unit lenses 3 of the lens sheet 1 constituting the optical sheet 52 of the present invention. It is desirable to install. Since the elliptical microlens 401 has a smaller radius of curvature in the minor axis direction S than in the major axis direction L, the light collection effect is enhanced. Therefore, the overall luminance is higher when the minor axis direction of the elliptical microlens 401 is the X direction. Similarly, the aspect ratio can be changed also in a quadrangular prism sheet or a polygonal prism sheet. In this case, it is desirable to install in the direction perpendicular to the direction of the straight axis and the arrangement direction of the unit lenses 3 of the lens sheet 1 constituting the optical sheet 52 of the present invention.

The optical film 400 is preferably a diffusion film. More preferably, the total light transmittance is 60 to 80% (in the measurement according to JIS K7361-1), and the haze value is 85% to 98% (in the measurement according to JIS K7136). Here, the diffusion film is one in which a resin filler 405 is disposed on a translucent substrate 403 as shown in FIG. The resin filler 405 protrudes from the surface of the film, and by combining with the optical sheet 52 of the present invention, the same effect as that of the microlens sheet can be obtained, and the luminance is increased.
In addition, since the large and small resin fillers 405 are arranged almost randomly in the diffusion film, an effect of suppressing moire interference fringes generated between the optical sheet 52 of the present invention and the pixels of the display device can be obtained.
When the total light transmittance is less than 60%, the diffuser film combined with the optical sheet 52 of the present invention is not desirable because the amount of reflected light increases and the overall luminance decreases. If it exceeds 80%, the protruding amount of the resin filler 405 is small and the light collecting effect is reduced, which is not desirable. If the haze value is less than 80%, the projection amount of the resin filler 405 is small and the light condensing effect is reduced. Further, the diffusion effect is insufficient, and the moire interference fringe suppressing effect is lowered, which is not desirable. If it exceeds 98%, the diffusion effect is too strong, and the light collecting effect cannot be obtained.

  The optical sheet 52 can be used not only in the case where the light source is a cold cathode fluorescent lamp, but also in a display device using LEDs, EL, semiconductor lasers and the like that have recently attracted attention as a light source for display.

Here, when an LED is used as a light source of a display device, an array of red, green, and blue LEDs is used, and light from the array of red, green, and blue LEDs is mixed with a light guide plate or the like to uniformly generate white light. It can also be used for those that emit light and those that can be emitted uniformly as white light by mixing light from an array of red, green, and blue LEDs using a diffuser plate or the like.

Further, the backlight unit has been made thinner and thinner, and the distance between the light source 41 and the optical sheet 52 has been shortened accordingly. However, if the optical sheet 52 of the present invention is used, a direct type or a side edge type is used. This backlight unit can be used satisfactorily without any influence of visibility such as a dark spot between the light source lamps.
In addition, the size of the optical sheet 1 is also increasing along with the increase in the size of the display device, but the optical sheet 52 of the present invention is thin and strong, and further has excellent display quality. It can be sufficiently used for such a large display device.

(Example 1)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 100 μm, the lens height is 50 μm, and the shift amount Δ is 40 μm. The unit lens 3 having a pitch of 140 μm is made of UV curable resin, a two-stage cylindrical protrusion is made of UV curable resin on the other surface, and the first-stage cylinder radius close to the flat part 102 is 40 μm. The height was 30 um, the radius of the second column was 20 um, and the height was 15 um, and they were arranged at a pitch of 200 um. In addition, the angle formed by the unit lens 3 and the arrangement direction of the protrusions 4 was 15 degrees.
The produced lens sheet 1 is laminated and integrated with a commercially available PC resin diffuser plate with an adhesive, and is set so that the angle formed between the pixel of the liquid crystal TV and the unit lens 3 is 20 degrees. As a result, a liquid crystal TV with no peeling and no moire was obtained.
(Example 2)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 100 μm, the lens height is 50 μm, and the shift amount Δ is 40 μm. The unit lens 3 having a pitch of 140 μm is made of UV curable resin, and a two-stage cylindrical protrusion is formed on the other surface using UV curable resin at a position facing the pitch between adjacent unit lenses 3. The first-stage cylinder radius close to the plane part 102 is 40 μm, the height is 30 μm, the second-stage cylinder radius is 20 μm, the height is 15 μm, and the pitch is 280 μm.
The produced lens sheet 1 is laminated and integrated with a commercially available PC resin diffuser plate with an adhesive, and is set so that the angle formed between the pixel of the liquid crystal TV and the unit lens 3 is 20 degrees. As a result, a liquid crystal TV with no peeling and no moire was obtained.
(Example 3)
By adjusting each coefficient of the base material 2 and the curved side surface from (Equation 1), the unit lens 3 having a prism lens pitch of 100 μm, a lens height of 50 μm, a shift amount Δ of 40 μm and a pitch of 140 μm, and 2 Stepped cylindrical protrusions are made by extrusion molding with PC resin, and the shape of the protrusions is 40 μm for the first columnar radius near the flat surface 102, 30 μm for the height, and 20 μm for the second columnar radius. The height was 15 um, and the pitch was 200 um. In addition, the angle formed by the unit lens 3 and the arrangement direction of the protrusions 4 was 15 degrees.
The produced lens sheet 1 is laminated and integrated with a commercially available PC resin diffuser plate with an adhesive, and is set so that the angle formed between the pixel of the liquid crystal TV and the unit lens 3 is 20 degrees. As a result, a liquid crystal TV with no peeling and no moire was obtained.
Example 4
As a result of setting the optical sheet 52 produced in Examples 1 to 3 at an angle of 0 ° between the pixel of the liquid crystal TV and the unit lens 3 and placing a diffusion film thereon, a liquid crystal TV free from moire was obtained. . Further, as a result of measuring the luminance, the liquid crystal TV of Example 1 was + 6%, the liquid crystal TV of Example 2 was + 5%, and the liquid crystal TV of Example 3 was + 3% compared to before the diffusion film was placed. was gotten.
(Example 5)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 45 μm, the lens height is 25 μm, and the shift amount Δ is 20 μm. The unit lens 3 having a pitch of 65 μm is made of UV-curing resin, a two-stage cylindrical protrusion is made of UV-curing resin on the other surface, and the first-stage cylinder radius near the flat portion 102 is 30 μm. When the height of the second column is 15 um, the height of the column is 15 um, the height is 10 um, and the pitch of 242 um is thinned out with respect to the arrangement of the basic grid, the projections 4 are arranged in all the basic grids. It arranged so that it might become 50% of number of projection parts 4 with respect to the case where it was done.
(Example 6)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 45 μm, the lens height is 25 μm, and the shift amount Δ is 20 μm. The unit lens 3 having a pitch of 65 μm is made of UV-curing resin, a two-stage cylindrical protrusion is made of UV-curing resin on the other surface, and the first-stage cylinder radius near the flat portion 102 is 30 μm. When the height of the second column is 15 um, the height of the column is 15 um, the height is 10 um, and the pitch of 242 um is thinned out with respect to the arrangement of the basic grid, the projections 4 are arranged in all the basic grids. It arranged so that it might become 70% of number of protrusion parts 4 with respect to the case where it was done.
(Comparative Example 1)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 45 μm, the lens height is 25 μm, and the shift amount Δ is 20 μm. The unit lens 3 having a pitch of 65 μm is made of UV-curing resin, a two-stage cylindrical protrusion is made of UV-curing resin on the other surface, and the first-stage cylinder radius near the flat portion 102 is 30 μm. When the height of the second column is 15 um, the height of the cylinder is 15 um, the height is 10 um, and the pitch of 316 um is thinned out with respect to the layout of the basic grid, the projections 4 are arranged in all the basic grids. It arranged so that it might become 50% of number of projection parts 4 with respect to the case where it was done.
(Example 7)
By adjusting each coefficient of the curved side surface from (Equation 1) on one surface of the biaxially stretchable and easily adhesive PET film substrate 2, the prism lens pitch is 45 μm, the lens height is 25 μm, and the shift amount Δ is 20 μm. The unit lens 3 having a pitch of 65 μm is made of UV-curing resin, a two-stage cylindrical protrusion is made of UV-curing resin on the other surface, and the first-stage cylinder radius near the flat portion 102 is 30 μm. When the height of the second column is 15 um, the height of the cylinder is 15 um, the height is 10 um, and the pitch of 316 um is thinned out with respect to the layout of the basic grid, the projections 4 are arranged in all the basic grids. It arranged so that it might become 70% of number of protrusion parts 4 with respect to the case where it was done.

実施例５から７のサンプルは、平坦面１０２に傷がほとんど生じなかった。
比較例１は平坦面１０２に擦れ傷が発生した。また、このレンズシートをディスプレイ装置に組み込んだところ、表示画像に傷が視認されてしまった。 The lens sheets of Examples 5 to 7 and Comparative Example 1 were punched with a Thomson blade in a 32-inch size with a protective film bonded only to the lens surface, and packed in a set of 100 sheets for a transportation test. Carried out. The results are shown in Table 1.

In the samples of Examples 5 to 7, the flat surface 102 was hardly damaged.
In Comparative Example 1, scratches were generated on the flat surface 102. Further, when this lens sheet was incorporated into a display device, scratches were visually recognized in the display image.

(A) It is explanatory drawing which shows the lens sheet sectional drawing which concerns on embodiment of this invention. (B) It is explanatory drawing which shows the lens sheet top view which concerns on embodiment of this invention. (C) It is explanatory drawing which shows the lens sheet bottom view which concerns on embodiment of this invention. (A) It is explanatory drawing which shows arrangement | positioning with the unit lens and projection part of the lens sheet which concerns on embodiment of this invention. (B) It is explanatory drawing which shows arrangement | positioning with the unit lens and projection part of the lens sheet which concerns on embodiment of this invention. (C) It is explanatory drawing which shows arrangement | positioning with the unit lens and projection part of the lens sheet which concerns on embodiment of this invention. (D) It is explanatory drawing which shows arrangement | positioning with the unit lens and projection part of the lens sheet which concerns on embodiment of this invention. (A) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (B) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (C) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (D) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (E) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (F) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (G) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (H) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (I) It is a figure explaining an example of the projection part shape in connection with embodiment of this invention. (A) It is a figure explaining an example of the unit lens in connection with embodiment of this invention. (B) It is a figure explaining an example of the unit lens in connection with embodiment of this invention. (C) It is a figure explaining an example of the unit lens in connection with embodiment of this invention. It is a figure explaining the lens sheet which concerns on embodiment of this invention. It is explanatory drawing of (Formula 5) in this invention. (A) It is a figure explaining the effect by arrangement | positioning of the projection part in connection with the form of a prior art. (B) It is a figure explaining the effect by arrangement | positioning of the projection part in connection with the form of a prior art. (C) It is a figure explaining the effect by arrangement | positioning of the projection part in connection with embodiment of this invention. It is explanatory drawing which shows the illustrative display apparatus which concerns on embodiment of this invention. It is a figure explaining the optical effect | action of the lens sheet which concerns on embodiment of this invention. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the perspective view of BEF by a prior art. It is explanatory drawing which shows the structural example of the optical sheet for liquid crystal displays by a prior art. It is explanatory drawing which shows the light intensity distribution radiate | emitted from the optical sheet using BEF. It is explanatory drawing which shows the illustrative display apparatus which concerns on another embodiment of this invention. It is explanatory drawing which shows arrangement | positioning of the optical film which concerns on embodiment of this invention. It is explanatory drawing of the optical film which concerns on embodiment of this invention. It is explanatory drawing of the diffusion film which concerns on embodiment of this invention.

Explanation of symbols

H, K: light, V: vertical direction, X: horizontal direction, β: angle formed by the unit lens 3 and the protrusion 4, L: viewing surface (display display surface), M: average distance between the protrusions, S The height of the protrusion 1, the lens sheet, 2, the base material, 3 the unit lens, 4 the protrusion 25, the light diffusion layer 31, 33 the polarizing plate 32, the liquid crystal panel 35, the liquid crystal layer 36 ... Optical sheet, 39 ... Optical function sheet, 41 ... Light source, 43 ... Lamp house, 45 ... Light reflector, 50 ... Adhesive layer or adhesive layer, 52 ... Optical sheet, 100 ... Non-incident surface of the light diffusion layer, 101 Light emitting surface of light diffusing layer, 102 Flat surface (light incident surface of lens sheet), 200 Air gap, 300 Light diffusing film, 400 Optical film, 401 Ellipsoidal microlens, 403 Base material of optical film 405: Resin filler

Claims (16)

In a translucent base material provided with an entrance surface and an exit surface,
At least one type of unit lens is arranged on the emission surface,
A lens sheet comprising a substantially flat plane portion on the incident surface and a plurality of protrusions protruding from the plane portion.   The lens sheet according to claim 1, wherein the protruding portion is formed in a columnar shape having a central axis extending in a direction parallel to the thickness direction of the base material.   The lens sheet according to claim 1, wherein a cross-sectional area of the projecting portion decreases as the distance from the planar portion increases.   2. The lens sheet according to claim 1, wherein the protrusion is configured by two or more columns having different widths, and a cross-sectional area thereof decreases as the distance from the planar portion increases. The unit lens has a compound lens shape in which a prism lens having a pitch P0 having at least one kind of curved side surface is compounded by shifting in the pitch direction by Δ,
The shift amount Δ is the following formula:

The lens sheet according to claim 1, wherein the lens sheet is defined by a range of The unit lens has a lenticular shape arranged at a constant pitch,
A lens sheet in which the protrusions are arranged at a constant pitch,
The unit lenticular and the arrangement direction of the protrusions are shifted by an angle β,
The angle β is

The lens sheet according to claim 1, wherein the lens sheet is defined by a range of The array of the protrusions is
When the pitch for each protrusion is Pi and the basic pitch is Pm,

The lens sheet according to any one of claims 1 to 4, wherein each pitch Pi is randomly arranged at an integral multiple of the basic pitch Pm.   5. The optical sheet according to claim 1, wherein the protrusion is formed at a position facing a vicinity of a point where the inclined side surfaces of the adjacent unit lenses are joined. 6. The array of the protrusions is
When the pitch of each protrusion is Pi and the pitch of the unit lens is PL, the following equation:

9. The optical sheet according to claim 8, wherein each pitch Pi is randomly arranged at an integral multiple of the unit lens pitch Pm. The lens sheet according to any one of claims 1 to 9, wherein the thickness of the base material is 50 µm to 500 µm,
M is an average distance between two adjacent projections scattered on the back surface of the lens sheet on which the unit lenses are arranged.
When the height of the protrusion is S,
A lens sheet, wherein S / M is 7% or more and 15% or less. A diffuser plate that emits diffused light by reducing the unevenness in the amount of light by entering the light emitted from the light source and diffusing the incident light;
It comprises at least the lens sheet according to any one of claims 1 to 10,
An optical sheet in which the exit surface of the diffusion plate and the protrusion formed on the entrance surface of the lens sheet are integrally laminated by an adhesive layer or an adhesive layer. An image display element for defining a display image;
A backlight unit for display, comprising at least a light source and the optical sheet according to claim 11 on a back surface of the image display element.   An optical film provided with a concavo-convex shape for diffusing and collecting incident light on one surface of a translucent substrate between the image element and the optical sheet according to claim 11. The display backlight unit according to claim 12.   The display backlight unit according to claim 13, wherein the optical film is a prism film, a lenticular film, or a microlens film. The optical film is a diffusion film in which a resin filler is disposed on one surface of a translucent substrate,
14. The display backlight unit according to claim 13, wherein the total light transmittance is 60 to 80% and the haze value is 80% to 98%. An image display element that defines a display image according to transmission / shading in pixel units;
A display device comprising the display backlight unit according to claim 12 on a back surface of the image display element.

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