JP2011064744A - Optical sheet, backlight unit, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve friction resistance of an optical sheet provided in a display device, while maintaining the high-luminance performance and variation-in-luminance resolving performance of the display device. <P>SOLUTION: There is provided an optical sheet, wherein concavities and convexities are formed on both faces of a light-transmittable base material 15, a linear optical element 13 is arranged on one face 15a of the light-transmittable base material along the one face concerned, and a plurality of optical protrusions 14 which protrude higher than the optical element are also formed, wherein each of the protrusions is formed to have a curved face shape at its tip end in the protruding direction, and a distance between the adjacent optical protrusions is set to be longer than the arrangement pitches of the optical element. In this case, the following inequality is satisfied, wherein E [MPa] represents the elastic modulus of the optical sheet 12, ρ [g/cm<SP>3</SP>] represents the density of the optical sheet, h [μm] represents the thickness of the optical sheet, Tp [μm] represents the height of the optical element, Tr [μm] represents the height of the optical protrusions, and Pr [μm] represents a distance between the optical protrusions which are most adjacent to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a back surface of a liquid crystal panel in which a transmissive / non-transmissive lens sheet and a display optical sheet in pixel units or a display element having a display pattern defined according to a transparent state / scattering state is disposed. The present invention relates to a backlight unit that illuminates from the side, and a display device including the backlight unit.

In recent years, liquid crystal display devices using TFT (Thin Film Transistor) type liquid crystal panels and STN (Super Twisted Nematic) type 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 used in this type of backlight system is roughly divided into a light source lamp such as a cold cathode fluorescent tube (CCFT), and a flat plate made of acrylic resin having excellent light transmittance. There are a “light guide plate light guide method” (so-called edge light method) in which multiple reflections are made in the light guide plate, and a “direct type” method that does not use the 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. 9 is generally known.
In this liquid crystal display device, a liquid crystal panel 72 sandwiched between a pair of polarizing plates 71 and 73 is provided at the top, and a transparent base such as a substantially rectangular plate-like PMMA (polymethyl methacrylate) or acrylic is provided on the lower surface side thereof. A light guide plate 79 made of a material is provided. A diffusion film (diffusion layer, diffusion plate) 78 which is a kind of optical sheet is provided on the upper surface (light emission surface) side of the light guide plate 79.

Further, on the lower surface of the light guide plate 79, there is a scattering reflection pattern portion (not shown) for efficiently scattering and reflecting the light introduced into the light guide plate 79 in the direction toward the liquid crystal panel 72. A reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion.
In addition, a light source lamp 76 is attached to a side end portion of the light guide plate 79. Further, in order to efficiently make the light of the light source lamp 76 enter the light guide plate 79, the light source lamp 76 is covered so as to cover the rear side. A reflectance lamp reflector 81 is provided. The scattering reflection pattern portion described above is formed by printing a mixture obtained by mixing white titanium dioxide (TiO ₂ ) powder into a solution such as a transparent adhesive in a predetermined pattern (for example, a dot pattern) and drying it. This is a device for imparting directivity to the light incident on the light guide plate 79 and guiding it to the light exit surface side, and is intended to increase the luminance.

  Recently, in order to increase the light utilization efficiency of the light source lamp 76 to further increase the brightness, for example, as shown in FIG. 10, the optical sheet is a kind of optical sheet between the diffusion film 78 and the liquid crystal panel 72. It has been proposed to provide two prism films (prism layer, prism plate, prism sheet) 74 and 75 having a light condensing function. These prism films 74 and 75 are used to collect the 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. 9, since the control of the viewing angle is left only to the diffusibility of the diffusion film 78, this control is difficult, and the central portion in the front direction of the display is brighter and goes to the peripheral portion. The characteristic of darkening (the characteristic of the brightness in the normal direction of the display screen (liquid crystal screen) (frontal luminance) is inevitable) is that the central part of the liquid crystal screen is bright and becomes darker from the central part toward the peripheral part. Therefore, when the liquid crystal screen is viewed from the side (the direction inclined with respect to the normal direction), the luminance is greatly reduced, and the light utilization efficiency is reduced.
Further, in the apparatus using the prism films 74 and 75 illustrated in FIG. 10, two prism films 74 and 75 are necessary. Therefore, a decrease in the amount of light directed to the liquid crystal panel 72 due to light absorption by the prism films 74 and 75 ( Not only is the light use efficiency reduced), but the manufacturing cost of the apparatus increases due to an increase in the number of members.

On the other hand, the direct type backlight unit is used in a display device such as a large liquid crystal TV in which the light guide plate 79 is difficult to use. As a liquid crystal display device using a direct type backlight unit, a device illustrated in FIG. 11 is generally known.
In this liquid crystal display device, a liquid crystal panel 72 sandwiched between a pair of polarizing plates 71 and 73 is provided at the top, and a plurality of light sources 51 made of fluorescent tubes or the like are provided on the lower surface side. Further, a diffusion film 82 which is a kind of optical sheet is provided between the light source 51 and the liquid crystal panel 72. In this configuration, the light emitted from the light source 51 and diffused in the diffusion film 82 can be 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, in the apparatus illustrated in FIG. 11 as well, in the same way as in the apparatuses illustrated in FIGS. 9 and 10, since the control of the viewing angle is left only to the diffusibility of the diffusion film 82, this control is difficult. The center of the front direction is bright and dark as it goes to the periphery. 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.
In addition, if the distance between the light sources 51 is too wide, luminance unevenness is likely to occur on the display screen. Therefore, the number of light sources 51 cannot be reduced, resulting in an increase in power consumption and an increase in manufacturing cost. I will.

By the way, such a liquid crystal display device is strongly required as a market need to be lightweight, low power consumption, high brightness, and thin, and is mounted on the liquid crystal display device in accordance with this request. The backlight unit is also required to be lightweight, low power consumption, and high brightness.
However, it is difficult to say that the above-described conventional apparatus sufficiently satisfies the demand for high brightness and low power consumption, and the liquid crystal with low price, high brightness, high display quality, and low power consumption is not expected from the user. The development of a backlight unit that can realize a display device is awaited.

In response to such circumstances, attempts have been made to realize the functions of a plurality of optical sheets used in a backlight unit with a smaller number of optical sheets. For example, an optical system having both light collecting and diffusing functions. Sheet development is actively underway.
However, if an optical sheet (condensing sheet) that has a condensing function is located on the outermost surface of the panel (liquid crystal panel) side, the light source is turned on based on changes in the surrounding environment such as high temperature and high humidity. There is a problem that the temperature in the backlight unit changes based on switching off, which causes a difference in brightness between brightness and display quality.
In general, the demand for low power consumption for the backlight unit is dealt with by reducing the number of light sources or changing the position of the light source. The in-plane brightness unevenness due to will be larger than before. For this reason, further improvement in front luminance and elimination of in-plane luminance unevenness are required for the optical sheet.

  In view of the above, there is a demand for an optical sheet in the market that can exhibit both the luminance improvement required by only one optical sheet and the elimination of in-plane luminance unevenness. In view of display quality, luminance improvement, and luminance unevenness, there is a current situation in which two or more optical sheets including a diffusion plate are used in combination.

  When two or more optical sheets are used in combination, the surface properties (scratch resistance) that the optical sheets including the light collecting sheet (optical sheet) do not damage each other even if vibration occurs in the housing or the like. Must have. In addition, when two or more optical sheets are used in combination, the number of sheets is increased as compared with the case of a single-sheet configuration, and therefore further cost reduction is required for each optical sheet.

Note that improving the scratch resistance of the optical sheet itself is also effective in reducing the manufacturing cost of the optical sheet.
Specifically, in the related art, a protective film is bonded to the incident surface, the light emitting surface, or both of the optical sheet to prevent the surface (incident surface / light emitting surface) from being damaged. The main purpose of use of this protective film is through a number of processes from the preparation and processing of the optical sheet to the setting of the optical sheet to the housing, and the shape of the protective film is rubbed during the process. It is to prevent collapse. And since this protective film peels immediately before setting an optical sheet to a housing | casing, a protective film does not affect the performance of an optical sheet. That is, omitting the use of the protective film by improving the scratch resistance of the optical sheet itself leads to a reduction in the manufacturing cost of the optical sheet and the omission of the step of attaching the protective film, which is effective for cost reduction. .

  As a matter related to improving the scratch resistance of the optical sheet, Patent Document 1 describes a prism plate (optical sheet) in which a plurality of linear prisms are arranged on one surface. Each prism is formed between two flat slopes inclined in opposite directions with respect to the surface direction of the prism plate, and a flat surface formed between the upper ends of the two slope parts and parallel to the surface direction of the prism plate. It is formed by the top surface part made into the surface. The top surface portion is formed over the entire longitudinal direction of the prism. In this configuration, since another optical sheet can be disposed on the flat top surface portion, the other optical sheet can be prevented from being damaged by the prism.

  On the other hand, in Patent Document 2, a solution in which fine particles are dispersed is applied to the incident surface of the optical sheet (first method), or is transferred to the incident surface using a mold having an uneven shape. It has been proposed to form minute irregularities on the entire incident surface by (second method). Moreover, the effect that the balance of the brightness nonuniformity elimination effect by front surface brightness | luminance by the improvement of the diffusibility of an optical sheet and the front brightness | luminance is acquired by forming a micro unevenness | corrugation is shown. However, in the first method, the number of steps for applying the solution in which the fine particles are dispersed increases, so that the material cost and the processing cost increase, leading to an increase in the manufacturing cost of the optical sheet. In addition, by forming another layer (coating layer) from the above solution on the incident surface of the optical sheet, there is a difference in thermal expansion coefficient between the incident surface and the coating layer. There is also concern about deterioration of environmental characteristics such as deflection. On the other hand, in the second method, since the minute unevenness is directly formed on the incident surface of the optical sheet, the problem of the first method does not occur. Further, in the second method, since there are a large number of minute irregularities on the entire incident surface, the scratch resistance is less noticeable even if scratches are made, and the scratch resistance is improved. This is because the optical sheet has diffusibility due to minute unevenness, and thus the difference in unevenness between the portion where the scratch exists and the portion where the scratch does not exist is reduced, and the visibility of the scratch is reduced.

JP 2009-122440 A JP 2009-123397 A

  However, the methods described in Patent Documents 1 and 2 described above appropriately design both the scratch resistance and optical performance of the optical sheet, that is, obtain desired optical performance while having high scratch resistance. However, there is a current situation in which optical design is performed at the expense of optical performance in order to provide scratch resistance.

  Specifically, in the prism plate described in Patent Document 1, although the flat top surface portion is provided to improve scratch resistance (scratch resistance), the flat top surface portion is replaced with each prism. In particular, forming over the entire longitudinal direction of each prism greatly affects the optical performance, and a reduction in luminance is inevitable. This is because when light incident obliquely from the incident surface of the optical sheet hits the flat top surface portion, the light is reflected there and returned without being emitted outward from the emission surface. When the planar top surface portion is formed over the entire length of each prism, the proportion of the planar top surface portion of the exit surface of the optical sheet is very large. As a result, the light exits outward from the exit surface. Very little light is emitted. In order to suppress the decrease in luminance as much as possible, the width of the top surface portion of each prism must be reduced to reduce the area, but in this case, the effect of scratch resistance is reduced.

Further, in the second method of Patent Document 2, since a large number of minute irregularities are formed over the entire incident surface, the diffusibility of the optical sheet is strongly exerted, so that it is difficult to freely control the emitted light. , Leading to a decrease in luminance and optical performance. In addition, in order to suppress the diffusibility of the optical sheet to be small, it is only necessary to reduce the minute unevenness, but in this case, the effect of making the scratches less noticeable is diminished. In particular, if the micro unevenness is extremely reduced, the effect of reducing the visibility of scratches is not exhibited.
As described above, in the conventional method for improving the scratch resistance, the scratch resistance and the optical performance (particularly luminance) are in a trade-off relationship, and it is impossible to freely design both performances.

  The present invention has been made in view of the circumstances described above, and is an optical that can freely design both scratch resistance and optical performance by combining an optical shape with excellent scratch resistance and an optical shape with excellent optical performance. An object is to provide a seat, a backlight unit including the sheet, and a display device.

  In order to solve the above problems, the present invention provides an optical sheet having high scratch resistance while maintaining the performance of eliminating high brightness and uneven brightness by controlling the shape of the exit surface and the entrance surface of the optical sheet. provide. Hereinafter, means provided by the present invention will be described in detail.

が成り立っていることを特徴とする。 The optical sheet of the present invention is an optical sheet in which a concavo-convex shape is formed on at least one surface of a translucent substrate, and the concavo-convex shape is formed on one surface of the translucent substrate. The optical elements are formed in a one-dimensional direction extending along the one surface or in the form of dots, and are arranged along the one surface. Further, the optical element is disposed on the one surface. A plurality of optical projections projecting higher than the height of the optical projection, each optical projection is formed in a shape having a curved surface at least at the tip in the projecting direction, and the distance between the adjacent optical projections is the optical element The elastic modulus of the optical sheet is E [MPa], the density is ρ [g / cm ³ ], the thickness is h [μm], and the height of the optical element is Tp [μm]. ], The height of the optical protrusion is Tr [μm], and the front Following equation shortest distance among distances between the optical projection when the Pr [μm],

It is characterized by that.

In this optical sheet, the surface on which light is incident (the other surface side of the translucent substrate) forms the incident surface of the optical sheet, faces the incident surface, and light is transmitted from the incident surface side. The surface that exits through the transparent substrate (one surface side of the translucent substrate) forms the exit surface of the optical sheet. In addition, the incident surface and the exit surface indicate surfaces including an uneven surface.
The optical element of the optical sheet is one that exhibits a function (optical function) such as condensing or diffusing light emitted from the exit surface (for example, a lens or a prism). Examples of the optical element having a shape extending in the one-dimensional direction include a prismatic prism shape, a cylindrical lens having a circular cross section or an elliptical shape. Specific examples of the dot-like optical element include, for example, those having a polygonal prism shape, hemispherical and hemispherical microlenses, and the like.

  Moreover, in the said optical sheet, it is preferable that the front-end | tip of the said optical protrusion is rounded.

  Furthermore, in the optical sheet, it is more preferable that the optical protrusion has a rounded or substantially hemispherical shape.

  In addition, the said hemispherical shape has shown that the planar view shape (The shape of the optical protrusion which looked at the optical sheet from the one surface side of the translucent base material) becomes a circular shape. On the other hand, the substantially hemispherical shape indicates that the planar view shape of the optical protrusion includes not only a circular shape but also an elliptical shape. In other words, the substantially hemispherical shape includes both a hemispherical shape and a semi-elliptical sphere shape.

  In the optical sheet, the plurality of optical protrusions may be regularly arranged.

  In the optical sheet, the plurality of optical protrusions may be irregularly arranged.

  Note that the regular arrangement of the plurality of optical protrusions indicates an arrangement of optical protrusions having geometric regularity / laws such as equidistant arrangement of the plurality of optical protrusions. On the other hand, the irregular arrangement of a plurality of optical protrusions indicates an arrangement of optical protrusions having no geometric regularity / law.

  Furthermore, in the said optical sheet, it is preferable to shape | mold an uneven | corrugated shape in the other surface of the said translucent base material.

が成り立っていることが好ましい。 Further, when the concave and convex shape is formed on the other surface of the optical sheet, a plurality of pressure adjusting portions for forming the concave and convex shape is formed on the other surface of the translucent substrate. The height of the pressure adjusting part is Td [μm], and the shortest distance among the distances between the pressure adjusting parts adjacent to each other When Pd [μm],

Is preferably satisfied.

  Furthermore, in the optical sheet, it is more preferable that the tip of the pressure adjusting unit is rounded.

  In the optical sheet, a plurality of the pressure adjusting units may be regularly arranged.

  Furthermore, in the optical sheet, the plurality of pressure adjusting units may be irregularly arranged.

  Note that the regular arrangement of the plurality of pressure adjusting units indicates the arrangement of the pressure adjusting units having geometric regularity / laws, such as an equal interval arrangement of the plurality of pressure adjusting units. ing. On the other hand, the irregular arrangement of the plurality of pressure adjusting units indicates the arrangement of the pressure adjusting units having no geometric regularity / law.

が成り立っていることがより好ましい。 Further, in the optical sheet, the following formula is provided between the optical element, the optical protrusion, and the pressure adjusting unit:

Is more preferable.

  The backlight unit of the present invention is for a display device, and is configured by disposing at least a light source on the other surface side of the translucent substrate with respect to the optical sheet. Features.

  In the display device of the present invention, an image display element that defines a display image according to transmission / light-shielding at least in units of pixels is arranged on the one surface side of the optical sheet in the backlight unit. It is characterized by being.

According to the present invention, both the optical performance and the scratch resistance are excellent by providing the optical element having a shape having high optical performance on the light exit surface of the optical sheet and the optical protrusion having a shape excellent in scratch resistance. An optical sheet can be obtained. In particular, by adjusting the installation ratio of the optical element and the optical protrusion so as to satisfy [Equation 1], it becomes possible to obtain desired scratch resistance without changing the shape of the optical element. In addition, with respect to the incident surface of the optical sheet, the scratch resistance is improved by providing the pressure adjusting portion.
And when the scratch resistance on both the incident surface and the exit surface is improved, the protective film conventionally used for surface shape protection can be omitted, and the manufacturing cost and the process cost can be reduced. The cost of the optical sheet can be reduced.

It is sectional drawing which shows the structure of the display apparatus containing the optical sheet by 1st embodiment of this invention. It is sectional drawing which shows the structure of the display apparatus containing the optical sheet by 2nd embodiment of this invention. It is sectional drawing which shows the optical sheet of this invention. It is sectional drawing before and behind abrasion of the optical protrusion in the optical sheet of this invention. It is sectional drawing before and behind abrasion of the optical protrusion in the optical sheet of this invention. It is a top view which shows the state which looked at the optical sheet of this invention from the output surface side. It is sectional drawing which shows the optical sheet of this invention. It is explanatory drawing of the extrusion method which is 1 type of the preparation methods of the optical sheet of this invention. It is explanatory drawing which shows the structure of the display apparatus by a light-guide plate light guide system as an example of a prior art. It is explanatory drawing which shows the structure of the display apparatus by another light-guide plate light guide system as an example of a prior art. It is explanatory drawing which shows the structure of the display apparatus by a direct type system as an example of a prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a first embodiment of a display device provided with the optical sheet of the present invention.
A display device 1 shown in FIG. 1 includes a backlight unit 2 and a liquid crystal panel (liquid crystal display element) 3 as an image display element. In the backlight unit 2, for example, a plurality of light sources 4 composed of cold cathode fluorescent lamps (CCFTs) arranged at predetermined intervals, and a reflector 5 that is disposed on the back surface of the light source 4 and reflects emitted light on the back surface side. A lamp house 6 is configured. The light source 4 is not limited to a cold cathode tube, and an EL, an LED, a semiconductor laser, or the like can be employed. That is, the light source 4 only needs to supply light toward at least the liquid crystal panel 3, and may be configured by a linear light source such as a cold cathode tube, a point light source such as an LED, or the like. The plurality of light sources 4 may be arranged along the surface direction of the liquid crystal panel 3.

A diffusion plate 7 serving as a light diffusion layer for diffusing light entering from the light source 4 is disposed in front of the light irradiation direction of the light source 4 (direction K in FIG. 1). On the other hand, the liquid crystal panel 3 is configured by sandwiching a liquid crystal element 10 between a pair of polarizing plates 9. Further, an optical sheet 12 that collects and diffuses light transmitted through the diffusion plate 7 is disposed between the diffusion plate 7 and the liquid crystal panel 3.
In the present embodiment, a liquid crystal display device is shown as the display device 1. However, the present invention is not limited to this, and an image is displayed by light, such as a projection screen device, a plasma display device, or an EL display device. Any type of display device 1 may be used as long as it is a display device. In other words, any display device including an image display element that defines a display image according to transmission / light shielding at least in pixel units may be used.

FIG. 2 is a schematic view showing a second embodiment of a display device provided with the optical sheet of the present invention.
As shown in FIG. 1, only the optical sheet 12 may be installed between the diffusion plate 7 and the liquid crystal panel 3, but as shown in FIG. A combination of the optical sheets 31 and 32 may be installed. That is, the display device 30 shown in FIG. 2 is different from the configuration of the display device 1 shown in FIG. 1 in that the backlight unit 33 includes other optical sheets 31 and 32.
In FIG. 2, the other optical sheets 31 and 32 are installed both above and below the optical sheet 12. However, for example, another optical sheet 31 may be installed only above, or Alternatively, another optical sheet 32 may be installed only below. Further, the number of other optical sheets 31 and 32 used is not limited to one as shown in FIG. 2, and two or more sheets are stacked and installed above or below the optical sheet 12 of the present invention. It is also possible. Further, as the other optical sheets 31 and 32, two or more types of optical sheets having different optical functions such as light collection and diffusion may be used, or the same type of optical sheets may be used. .

  If it demonstrates in detail, it is possible to employ | adopt the suitable optical sheet for condensing as another optical sheet 31 and 32, for example, the polygonal-prism prism sheet represented by the square-prism prism sheet, a triangle, etc. Examples include a prismatic prism sheet represented by a columnar prism sheet, a semicircular or semielliptical cylindrical lens, a microlens sheet, and a diffusion sheet. In the case where a polygonal prism sheet or a cylindrical lens is employed as the other optical sheets 31 and 32, each prism and each lens are formed in a column shape. It is desirable to arrange a plurality of prisms and lenses in each of the optical sheets 31 and 32 so that the direction is orthogonal to the longitudinal direction of the prisms and lenses of the other optical sheet 32.

As shown in FIG. 3, the optical sheet 12 is generally configured by forming concave and convex shapes on both surfaces 15 a and 15 b of a translucent substrate 15 formed in a plate shape. And in this optical sheet 12, on one surface 15a of the translucent base material 15, a plurality of optical elements 13 for forming a concavo-convex shape, and a plurality of protrusions higher than the height dimension of the optical element 13 are provided. An optical protrusion 14 is formed. In addition, a plurality of pressure adjusting portions 16 for forming a concavo-convex shape project from the other surface 15 b of the translucent base material 15.
In this optical sheet 12, the light incident surface (the other surface 15b side of the translucent substrate 15) is the incident surface of the optical sheet 12, facing the incident surface, and the light is incident on the incident surface side. The surface on the side that exits through the light-transmitting substrate 15 (the one surface 15 a side of the light-transmitting substrate 15) is defined as the light-emitting surface of the optical sheet 12. And these incident surfaces and output surfaces have shown the surface containing an uneven | corrugated shaped surface.
Therefore, in the display devices 1 and 30 and the backlight units 2 and 33 shown in FIGS. 1 and 2, the light source 4 and the diffusion plate 7 are disposed on the other surface 15 b side of the translucent substrate 15, and the liquid crystal panel 3 is The light-transmitting substrate 15 is disposed on the one surface 15a side.

Hereinafter, the detail regarding the structure by the side of the output surface of the optical sheet 12 of this invention is described.
Each optical element 13 exhibits a function (optical function) such as condensing and diffusing with respect to light emitted from the exit surface of the optical sheet 12 (for example, a lens or a prism). As such an optical element, for example, in a one-dimensional direction along one surface 15a of the translucent base material 15 such as a prismatic prism shape, a cylindrical lens having a circular cross section or an elliptical shape, or the like. The thing of the extended shape (for example, refer FIG. 6) is mentioned. Further, examples of the optical element 13 include a polygonal prism-shaped one and a dot-shaped one such as a hemispherical or hemispherical microlens. In FIG. 3, the optical element 13 is described as a prism having an apex angle of 90 °.
The plurality of optical elements 13 configured as described above are arranged at a constant pitch along one surface 15a of the translucent substrate 15.

Each optical protrusion 14 is formed in a shape having a curved surface shape. In FIG. 3, the optical protrusion 14 is formed in a hemispherical shape and the entire surface thereof has a curved surface shape, but may be formed in, for example, an elliptical sphere as another shape in which the entire surface has a curved surface shape. . The optical protrusion 14 may not have a curved surface as a whole. For example, even if the optical protrusion 14 is formed in a conical shape, a polygonal pyramid shape, a cylindrical shape, a polygonal columnar shape, or the like, at least the protruding direction of the optical protrusion 14 It is only necessary to have a curved surface shape at the tip (see, for example, FIG. 5). In other words, the tip in the protruding direction of the optical protrusion 14 only needs to be rounded. However, the optical protrusion 14 is most preferably hemispherical or semi-elliptical.
Further, as shown in FIG. 6, each optical protrusion 14 has various dot shapes such as a circular shape (optical protrusion 14C), an elliptical shape (optical protrusion 14D), and a polygonal shape (optical protrusion 14E) in plan view. Is formed. The plurality of optical protrusions 14 configured as described above are arranged such that the distance between the adjacent optical protrusions 14 is set longer than the arrangement pitch of the optical elements 13.

  The diameter of each optical protrusion 14 (including the major axis or the length of one side here) Dr (see FIG. 6) is not limited, but the optical sheet 12 of the present invention is the first embodiment. When used as in (FIG. 1) or the second embodiment (FIG. 2), it is necessary that the optical protrusion 14 be of such a size that it cannot be seen on the screen, so its diameter Dr is 200 μm. It is necessary to do the following. In particular, in order to eliminate the visibility of the optical protrusion 14 by using only the optical sheet 12 of the present invention without combining with the other optical sheets 31 and 32 as in the first embodiment, the diameter Dr should be 170 μm or less. Is desirable. This is because when the diameter Dr of the optical protrusion 14 is larger than 170 μm, the shape and arrangement of the optical protrusion 14 are visually recognized, and the display quality of the optical sheet 12 is lowered. On the other hand, although the optical protrusion 14 can be implemented if it is not visually recognized, if the diameter is actually smaller than 20 μm, the height dimension of the optical protrusion 14 is set to the height dimension of the optical element 13 when the optical sheet 12 is molded. It is desirable to set the diameter of the optical protrusion 14 to 20 μm or more, because it is difficult to set a higher value than that, or to satisfy the relational expression [Formula 1] described later.

By the way, as a measure for improving the scratch resistance of the optical sheet 12, while preventing the scratch itself from entering, the visibility of the scratch is lowered when the scratch is entered, and the optical performance of the optical sheet 12 before and after the scratch is entered. There must be little change. Note that the optical performance of the optical sheet 12 mainly depends on the optical element 13.
In the optical sheet of the present invention, the elastic modulus of the optical sheet 12 is E [MPa], the density is ρ [g / cm ³ ], the thickness is h [μm], and the height of the optical element 13 is Tp [μm], When the height of the optical protrusion 14 is Tr [μm] and the distance between the optical protrusions 14 closest to each other is Pr [μm], the following equation is established.

It should be noted that the distance Pr between the optical projections 14 that are closest to each other indicates the shortest distance among the plurality of optical projections 14.
[Equation 1] indicates that the optical element 13 does not come into contact with the flat surface when placed on a flat surface so that the emission surface of the optical sheet 12 faces the optical sheet 12 of the present invention without applying a particularly large load. It also shows the conditions that can withstand even slight wear. In general, the deflection amount Vs has the following relationship.

  That is, the deflection amount Vs of the optical sheet can be adjusted by the elastic modulus E, the density ρ, and the thickness h of the optical sheet 12. However, the elastic modulus E and the density ρ are values determined by the materials used, and in the case of the optical sheet 12 of the present invention used for optical applications, other than the optical performance such as the refractive index, translucency, and transparency. In addition, the resin (material) that can be used is limited by strength and moldability, and it is difficult to select freely. Further, regarding the thickness h of the optical sheet 12, the thickness that can be implemented is limited because it affects the moldability, environmental characteristics, and price. Therefore, the optical element 13 can be protected by adjusting [Equation 1] by adjusting the height Tp of the optical element 13, the height Tr of the optical protrusion 14, and the distance Pr between the optical protrusions 14.

Here, when the optical sheet 12 is placed on a flat surface so that the emission surfaces face each other, the wear of the optical protrusions 14 on the flat surface will be described.
4A and 4B, when the optical protrusion 14 (14A) has a hemispherical shape, the optical protrusion 14 (14B) has a curved shape at the tip of the 90 ° prism in FIGS. 5A and 5B. The schematic before and after abrasion of the optical sheet 12 is shown respectively.
In the case of the hemispherical shape shown in FIG. 4, when the tip end of the prism rubs against a flat surface such as another sheet or a liquid crystal panel, the tip end shape is not easily broken, and when it is broken, the influence on the optical performance is small.
On the other hand, in the case of the shape having a curved surface at the tip of the 90 ° prism as shown in FIG. 5, even if slight wear, the shape change before and after the wear is large, and thus a significant decrease in luminance occurs. In order to solve this problem, it is necessary to increase the number of installed optical projections 14B and reduce the amount of wear of each optical projection 14B by reducing the pressure applied to each optical projection 14B. However, when the number of the optical projections 14B is increased, the ratio of the optical elements 13 is decreased, so that the optical performance of the optical sheet 12 is deteriorated. Therefore, the number of optical projections 14 is limited, and it is difficult to obtain sufficient scratch resistance.
From the above, it is desirable that the optical protrusion 14 be hemispherical or elliptical.

  In the present invention, the optical element 13 is designed to freely design the lens shape while ignoring the problem of scratch resistance and to provide the optical sheet 12 with scratch resistance by providing the optical protrusion 14. Therefore, the optical element 13 is not limited to the 90 ° prism as shown in FIG. 3, but is a triangular prism shape, a quadrangular prism shape or a polygonal prism shape with other angles such as 80 ° and 110 °. Or semi-elliptical cylindrical lenses, microlenses, and the like. That is, since the shape of the optical element 13 is not limited by providing the optical protrusion 14, any shape may be used as long as it satisfies the optically required performance (optical performance).

Further, the plurality of optical protrusions 14 may be arranged regularly or irregularly. In FIG. 6, the plurality of optical protrusions 14 are irregularly arranged.
When the optical protrusions 14 are regularly arranged, the distance between adjacent optical protrusions 14 is constant over the entire surface of the optical sheet 12, and the scratch resistance can be made uniform in the surface. However, when the optical projections 14 are regularly arranged, moire between the optical elements 13 and the optical projections 14, moire between other optical sheets 31 and 32 and the diffusion plate 7 provided as appropriate, and other members such as the liquid crystal panel 3. Therefore, there is a possibility that moire occurs.
On the other hand, when the optical projections 14 are irregularly arranged, it is possible to solve the moire problem that is most concerned when the optical projections 14 are regularly provided, and it is possible to use the optical projections 14 freely without considering the size. Become. However, since the distance between the optical protrusions 14 in the plane is not constant, the scratch resistance in the plane becomes non-uniform. Therefore, it is necessary to sufficiently consider so that a portion where the distance between the optical protrusions 14 is extremely large does not occur in the surface.

Next, the detail regarding the structure by the side of the entrance plane of the optical sheet 12 of this invention is described.
As shown in FIG. 3, each pressure adjusting unit 16 is a protrusion protruding from the other surface 15 b of the translucent substrate 15, for example, one-dimensionally along the other surface 15 b of the translucent substrate 15. It may be a linear protrusion extending in the direction or a dot-like protrusion. In the following description, the pressure adjustment unit 16 is mainly described as a dot shape. Moreover, in the following description, the other surface 15b of the translucent base material 15 also forms the incident surface of the optical sheet 12 by arranging the plurality of pressure adjusting portions 16 at intervals. Furthermore, although the following description demonstrates the other surface 15b of the translucent base material 15 as the smooth surface 15b without an unevenness | corrugation, you may have an unevenness | corrugation, for example.
In the optical sheet 12 of the present invention, for the purpose of improving the scratch resistance, when the height of the pressure adjusting portion 16 is Td [μm] and the distance between the pressure adjusting portions 16 that are closest to each other is Pd [μm], The following equation holds.

In addition, the distance Pd between the pressure adjusting units 16 that are closest to each other indicates the shortest distance among the plurality of pressure adjusting units 16.
[Equation 2] indicates that the optical sheet of the present invention is smooth without the pressure adjusting unit 16 when placed on a flat surface so that the incident surface of the optical sheet 12 faces without applying a particularly large load. The surface 15b is not in contact with each other, and shows a condition that the surface 15b can sufficiently withstand even slight wear. The deflection amount Vn of the optical sheet 12 has the relationship of the following equation.

  That is, the deflection amount Vn of the optical sheet 12 can be adjusted by the elastic modulus E, the density ρ, and the thickness h of the optical sheet 12. However, the elastic modulus E and the density ρ are values determined by the materials used, and in the case of the optical sheet 12 of the present invention used in optical applications, in addition to optical performance such as refractive index, translucency, and transparency. However, the resin (material) that can be used is limited depending on the strength and moldability, and it is difficult to select freely. In addition, the thickness h of the optical sheet 12 is also limited because it affects the moldability, environmental characteristics, and price. Therefore, the smooth surface 15b can be protected by adjusting the height Td of the pressure adjusting unit 16 and the distance Pd between the pressure adjusting units 16 to satisfy [Equation 2].

Next, further details of the incident surface shape of the optical sheet 12 of the present invention will be described.
An example of the shape of the pressure adjusting portion 16 on the incident surface is shown in FIG. In FIG. 7A, the substantially hemispherical (for example, semi-elliptical sphere) pressure adjusting portion 16A is randomly arranged (irregularly arranged) on the incident surface which is a smooth surface (flat surface) 15b. . Moreover, in FIG.7 (b), although the substantially hemispherical pressure adjustment part 16B is randomly arrange | positioned on the smooth surface 15b similarly to the case of Fig.7 (a), compared with Fig.7 (a), A dot shape having a large aspect ratio (ratio of height to width) representing the ratio between the height and the width of the pressure adjuster 16B is used as the pressure adjuster 16B. That is, the pressure adjustment part 16A in FIG. 7A has a height dimension set smaller than the width dimension, and the pressure adjustment part 16B in FIG. 7B has a height dimension greater than the width dimension. Is also set larger.
Here, the shape of the pressure adjusting unit 16 may be any shape as long as it has a curved surface at the tip in the protruding direction, but the entire surface is a curved surface, in particular, a hemispherical shape (a shape with an aspect ratio of 1) or substantially. A hemispherical shape is desirable. The reason is the same as in the case of the optical protrusion 14 provided on the exit surface of the optical sheet 12 of the present invention, and it is more preferable that the pressure adjusting portion 16 has a hemispherical shape (a shape with an aspect ratio of 1) or a substantially hemispherical shape. This is because the scratch resistance is improved and the optical performance changes little before and after the scratches are made.

The pressure adjusting unit 16C in FIG. 7C has a cylindrical shape as another example of the dot shape, and its tip is rounded in the same manner as the pressure adjusting units 16A and 16B in FIGS. 7A and 7B. I am tinged. Thus, if the condition that the tip of the pressure adjusting portion 16C is round is satisfied, the wear amount of the pressure adjusting portion 16C can be reduced. However, when the size (height dimension) of the tip portion (curved surface portion) exhibiting a curved surface shape is small, if the entire curved surface portion is worn, it is based on the shape change of the pressure adjusting portion 16C on the incident surface. There is a drawback that the amount of change in luminance becomes very large. On the other hand, when the pressure adjusting unit 16 has a hemispherical shape or a substantially hemispherical shape, the change in optical performance due to wear of the pressure adjusting unit 16 is gentle, and therefore, it is more suitable.
Furthermore, the size of the aspect ratio of the pressure adjusting unit 16 is not particularly limited, but a smaller one is more preferable. This is because, as described above, when the aspect ratio is large, the optical performance is easily affected, and the optical performance change before and after the wear becomes significant. However, as the height Td of the pressure adjusting unit 16 is increased, the incident surface can be more reliably prevented from being damaged. Therefore, the aspect ratio and the height Td of the pressure adjusting unit 16 are improved in terms of scratch resistance and optical performance. It is necessary to set in consideration of both.

Further, the diameter Dd (see FIG. 3) of the pressure adjusting unit 16 is not particularly limited, but is preferably 20 μm or more and 200 μm or less, and more preferably 50 μm or more and 150 μm or less.
When the diameter Dd of the pressure adjusting portion 16 is very small, such as 20 μm or less, in order to obtain sufficient scratch resistance, the pressure adjusting portion 16 is necessarily made a dot shape with a large aspect ratio. However, as described above, there arises a problem that the change in the optical performance before and after the wear becomes significant.
On the other hand, when the diameter Dd of the pressure adjusting part 16 is larger than 200 μm, the pressure adjusting part 16 is easily visually recognized, so that the display quality is deteriorated. Therefore, the diameter Dd of the pressure adjusting unit 16 is preferably 200 μm or less, particularly 150 μm or less when used without being combined with other optical sheets (optical sheets 31 and 32 in FIG. 2) as in the first embodiment.
In addition, although the numerical range of the diameter dimension (width dimension) Dd when the pressure adjustment part 16 is dot shape was described here, for example, when the pressure adjustment part 16 is linear extending in a one-dimensional direction. It is desirable to set the width dimension within the numerical range described above.

Moreover, the pressure adjustment part 16 may be arrange | positioned regularly and may be arrange | positioned irregularly. When regularly arranged, the distance between the pressure adjusting portions 16 adjacent to each other on the entire surface of the optical sheet 12 becomes constant, and the scratch resistance can be made uniform in the surface. However, as in the case of the optical protrusion 14 described above, moire between the pressure adjusting unit 16 and the optical element 13 or the optical protrusion 14, moire between other optical sheets 31 and 32 or the diffusion plate 7 provided as appropriate, or a liquid crystal panel. Since there is a possibility that moire with other members such as 3 may occur, it is necessary to sufficiently consider regularity.
On the other hand, when the pressure adjusting unit 16 is irregularly arranged, it can solve the moire problem that is most concerned when the pressure adjusting unit 16 is regularly provided, and can be freely used without considering the size. It becomes. However, since the distance Pd between the pressure adjusting portions 16 in the plane is not constant, the scratch resistance in the plane becomes non-uniform. Therefore, it is necessary to sufficiently consider so that a portion where the distance Pd between the pressure adjusting portions 16 is extremely large does not occur in the surface.

7A to 7C, the other surface 15b of the translucent base material 15 is a smooth surface. In addition to a mirror surface having no particular shape, it may be formed as a surface having a minute uneven shape as shown in FIG. Further, on the other surface 15b of the translucent base material 15, a triangular prism shape such as a micro prism shape whose height is sufficiently smaller than the pressure adjusting portion 16, a quadrangular prism shape, or a semi-elliptical cylindrical lens, a microlens A lens shape or the like may be formed. In particular, in the case of a micro uneven shape, a cylindrical lens, or a micro lens, it becomes more difficult to be scratched, and even if a scratch is made, the diffusibility of these shapes lowers the visibility of the scratch and makes the scratch less noticeable. effective. However, since the optical properties of the optical sheet 12, particularly the front luminance, tend to decrease due to the increase in diffusibility of the optical sheet 12, various shapes are imparted to the other surface 15b of the translucent substrate 15. In some cases, the optical performance of the optical sheet 12 must be fully considered.
As described above, the incident surface of the optical sheet 12 has a plurality of pressure adjusting portions 16 and is formed into a concavo-convex shape, but is formed only with a flat smooth surface such as a mirror shape. May be. In other words, the other surface 15b of the translucent substrate 15 does not have to be formed with an uneven shape. Moreover, the incident surface of the optical sheet 12 does not have the pressure adjusting unit 16, and is formed into a concavo-convex shape by having one or more of a micro concavo-convex micro prism shape, a cylindrical lens, and a micro lens shape. May be.

  And in the optical sheet 12 which has the pressure adjustment part 16, by satisfy | filling following Formula [Formula 3], even if it is "protection film removal" which does not stick a protective film on both the incident surface and an output surface, an optical sheet The generation of scratches and the like that affect the optical performance of the optical sheet 12 can be prevented during the period from the preparation and processing to the step of incorporating the optical sheet 12 into the housing.

[Equation 3] indicates that when two or more optical sheets 12 of the present invention are laminated, particularly when a large load is intentionally laminated, scratches or the like are generated on both the incident surface and the exit surface of the optical sheet 12. It is a condition that does not. Usually, the optical sheet 12 is molded by an extrusion method or a UV molding method. If the thickness is small, it is molded and wound into a roll at the same time, and then cut or punched into a predetermined size and loaded. If the thickness is very thick, it is cut and loaded immediately after molding.
In general, the stacked optical sheets 12 are delivered in a predetermined packing box. Normally, the optical sheets 12 are stacked with the incident surface or the exit surface determined upward or downward. That is, the incident surface of one of the stacked optical sheets 12 and the exit surface of the other optical sheet 12 come into contact with each other.
Therefore, even if the optical sheets 12 are stacked, it is necessary to satisfy the condition that the pressure adjusting unit 16 on the incident surface side and the optical element 13 on the output surface side do not come into contact with each other (condition that the optical element 13 is not damaged).
[Equation 3] described above satisfies the above-described condition, and when the condition that the pressure adjusting unit 16 (tip) approaches the optical element 13 (tip) most closely when the optical sheets 12 are stacked is considered. Must satisfy [Equation 3]. This is because, in a plurality of stacked optical sheets 12, when the incident surface of one optical sheet 12 and the exit surface of the other optical sheet 12 contact each other, the pressure adjusting unit 16 does not contact the optical element 13 and wears. It is a condition for not.

In addition to those described above, scratches that affect the optical performance may be those generated when the optical projection 14 on the exit surface side wears the smooth surface 15b on the entrance surface side.
However, in terms of the performance of the optical sheet 12, the height dimension of the optical element 13 on the exit surface side is higher than the smooth surface 15b on the incident surface side, and the tip of the optical element 13 is convex. In general, the incident surface is more easily damaged than the exit surface. Furthermore, the scratches on the exit surface side have a greater influence on the optical performance of the optical sheet 12 and the visibility is higher than the scratches on the entrance surface side.
Therefore, as long as the optical sheet 12 of the present invention satisfies [Equation 3], both surfaces of the optical sheet 12 are not damaged even when the optical sheet 12 is laminated.

  Note that one or both of the incident surface and the exit surface of the optical sheet 12 of the present invention may be provided with a hard coat layer having a high hardness or a high slip property in order to further improve the scratch resistance. Further, for example, in the extrusion method described later, only a surface layer (for example, a thin layer including a portion that becomes the optical element 13, the optical protrusion 14, and the pressure adjustment unit 16 in the optical sheet 12) is used, and the hardness is high. Alternatively, it may be possible to improve slipperiness and obtain further scratch resistance.

As the material used for the optical sheet 12, a material having optical transparency with respect to the wavelength of light emitted from the light source 4 is used. For example, a plastic material that can be used for an optical member such as a lens is used. it can.
Examples of this material include polyester resin, acrylic resin, polycarbonate resin, polystyrene resin, MS (acrylic and styrene copolymer) resin, polymethylpentene resin, thermoplastic resin such as cycloolefin polymer, or polyester acrylate. And transparent resins such as radiation curable resins composed of oligomers such as urethane acrylate and epoxy acrylate, or acrylates. Depending on the application of the optical sheet 12, for example, a material in which fine particles are dispersed in a transparent resin may be used as the material of the optical sheet 12.
As the fine particles, particles made of an inorganic oxide or particles made of a resin can be used. For example, transparent particles made of an inorganic oxide include particles made of silica, alumina, titanium oxide, or the like. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Examples thereof include fluorine-containing polymer particles such as fluoroethylene monohexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene monotetrafluoroethylene copolymer), and silicone resin particles. Further, the material used for the fine particles may be, for example, a mixture of two or more of the materials described above.
The optical sheet 12 may have a single layer structure or a multilayer structure, and may include a transparent layer.

When the optical sheet 12 is produced, for example, such a material is poured into a mold and solidified to form a plate-like member for producing the optical sheet 12 (hereinafter referred to as an optical sheet plate material). ), And thereafter, the optical element 13, the optical protrusion 14, and the pressure adjusting portion 16 may be appropriately formed on the optical sheet plate. The optical sheet plate material mainly forms the translucent substrate 15 in the optical sheet 12.
Typical examples of the method for forming the optical protrusion 14 include a laser method and a cutting method. In the laser method, a black resin having a high light-shielding property is uniformly applied to the surface (peripheral surface) of a mold roll (first mold roll) for forming the optical element 13 and the optical protrusion 14 on the emission surface side of the optical sheet 12. After irradiating the surface with a laser after being applied to the surface, the portion of the first mold roll irradiated with the laser is corroded by attaching the entire first mold roll to the acid solution, so that the optical protrusion 14 is exposed. This is a method of forming a corresponding shape on the surface (peripheral surface) of the first mold roll. In the cutting method, the shape corresponding to the optical protrusion 14 is formed on the first mold roll by intermittently pressing the center of the cutting tool whose tip shape is an aspherical shape against the surface (circumferential surface) of the first mold roll. It is a method of producing on the surface.
Further, by cutting the surface (circumferential surface) of the first mold roll with a diamond tool having various lens shapes, the shape corresponding to the optical element 13 (for example, a triangular shape) is formed on the surface of the first mold roll. Make it.
In the surface processing of the first mold roll described above, either the shape corresponding to the optical protrusion 14 or the shape corresponding to the optical element 13 may be performed first.

Next, a method for producing a mold roll (second mold roll) for forming the pressure adjusting unit 16 on the incident surface side of the optical sheet 12 will be described.
Since only the shape corresponding to the pressure adjustment unit 16 needs to be produced on the incident surface side of the optical sheet 12, only the method for producing the shape corresponding to the optical protrusion 14 described above is performed, so that the desired second A mold roll can be obtained. And the shaping | molding method of the shape corresponding to the pressure adjustment part 16 can mention the laser system and cutting system similar to the shaping | molding method of the optical protrusion 14. FIG.

Next, using these two mold rolls, the optical element 13, the optical protrusion 14, and the pressure adjusting unit 16 are formed on the optical sheet plate material, thereby producing the optical sheet 12. Examples of the molding method include an extrusion method, a casting method, and an injection method. In this case, as the plate material for the optical sheet, one having a thickness of 12 μm or more and 1 mm or less can be used. This is because if the thickness is less than 12 μm, the rigidity that can withstand the processing by the molding method described above cannot be obtained, and if the thickness exceeds 1 mm, the flexibility that can withstand the processing by the molding method cannot be obtained.
Moreover, the optical sheet 12 may be produced by, for example, a UV curing method.
When the optical sheet 12 is produced by the UV curing method, a UV curable resin is applied onto a base (a plate material for an optical sheet) that is a sheet-like base material, a mold having a desired shape is pressed, and then UV is applied. By irradiating, the optical sheet 12 including the base, the optical element 13 and the optical protrusion 14 can be obtained. As the sheet-like substrate, PET (polyethylene terephthalate), polycarbonate, acrylic, polypropylene films and the like well known in the art can be used.
At this time, the optical element 13 and the optical protrusion 14 and the base may be molded separately or may be molded integrally. Further, when the optical element 13, the optical protrusion 14, and the base are molded, a diffusing agent such as a filler can be dispersed therein and molded.

  In addition, although the typical preparation example about the optical sheet 12 was demonstrated, if the optical characteristic of this embodiment can be achieved, it can also be produced using materials, structures, processes other than the above. is there.

The diffusion plate 7 is composed of a transparent resin and fine particles or gas dispersed in the transparent resin. In this diffusing plate 7, the refractive index of the transparent resin and the refractive index of fine particles or gas need to be different from each other. This difference in refractive index causes light reflection and scattering at these interfaces. Thereby, luminance unevenness of the light emitted from the light source 4 is suppressed.
Note that the luminance distribution can be controlled in accordance with the characteristics required for the display light of the liquid crystal display device by appropriately selecting a material such as a transparent resin and fine particles constituting the diffusion plate 7 or a kind of gas. The difference in refractive index between the transparent resin and the transparent particles (fine particles) is preferably 0.01 or more. This is because if the difference in refractive index is smaller than 0.01, sufficient light scattering performance cannot be obtained. The difference in refractive index may be 0.5 or less.
Furthermore, since it is necessary for the diffusing plate 7 to transmit the incident light while scattering it, it is desirable that the average particle diameter of the transparent particles be 0.5 μm or more and 30.0 μm or less. Further, the diffusion plate 7 may adopt a structure having a fine cavity containing air (gas) as a transparent particle in a main material (for example, the above-described transparent resin). In this case, the main material and Diffusion performance can be obtained by the difference in refractive index with air.

Examples of the transparent resin used for the diffusion plate 7 include polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, MS (methacrylstyrene copolymer) resin, epoxy acrylate resin, and polystyrene resin. , Cycloolefin polymer, methylstyrene resin, fluorene resin, PET, polypropylene and the like.
As fine particles, particles made of an inorganic oxide or particles made of a resin can be used. For example, transparent particles made of an inorganic oxide include particles made of silica, alumina, titanium oxide, or the like. Further, transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, particles of melamine-formalin condensate, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Examples thereof include fluorine-containing polymer particles such as fluoroethylene monohexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene monotetrafluoroethylene copolymer), and silicone resin particles. Further, the material used for the fine particles may be, for example, a mixture of two or more of the materials described above.

The diffusion plate 7 configured as described above is manufactured by applying an extrusion method or a co-extrusion method to a material obtained by dispersing fine particles or bubbles in a transparent resin that is a thermoplastic resin. be able to. The extrusion method is a method in which a thermoplastic resin is heated and dissolved in an extruder and extruded from a T die to form a plate or a sheet. The coextrusion method is used when the diffusion plate 7 is formed as a laminated plate or a laminated sheet. Using a plurality of extruders, the thermoplastic resin is heated and melted, and a laminated die such as a feed block die or a manifold die is used. This is a method of forming into a multi-layered plate by laminating and extruding.
The diffusion plate 7 may be a multi-layer, or the plurality of layers may be composed of different resins, fine particles, or the like.

Examples will be described below.
(Experiment 1: Examination of Tp, Tr, Pr on the exit surface)
As the examination of the exit surface of the optical sheet 12, the height difference Tr-Tp between the optical projection 14 and the optical element 13 is 6 types from 5 μm to 25 μm, and the distance Pr between the optical projections 14 closest to each other is 300 μm. 7 types were prepared in the range of up to 600 μm, and a total of 42 types of optical sheets 12 were prepared by combining these two parameters, and the scratch resistance was evaluated.
Each of the optical elements 13 in these optical sheets 12 has a triangular prismatic prism lens shape with an apex angle of 90 ° and an arrangement pitch of 30 μm and a height Tp of 15 μm. The optical protrusion 14 has a microlens shape with a height Tr of 20 μm to 40 μm, and the diameter Dr of the optical protrusion 14 is adjusted as needed to correspond to the desired height Tr of the optical protrusion 14. Further, the plurality of optical protrusions 14 are regularly arranged in a honeycomb structure (hexagonal fine structure).

(Experiment 1: optical sheet manufacturing method)
A microlens shape having a honeycomb structure (hexagonal fine structure) corresponding to the optical protrusions 14 was formed on the entire mold roll using a laser method. The distance Pr between the optical protrusions 14 was dealt with by adjusting the laser irradiation position. Further, the height Tr of the optical protrusion 14 was dealt with by adjusting the laser diameter at the time of laser irradiation and the time for the mold roll to be immersed in the acid solution and corroded after the laser irradiation. As a result, the mold shapes corresponding to the desired height Tr of the optical projections 14 could be obtained. Thereafter, this mold roll was set on a precision cutting machine, and a 90 ° prism shape corresponding to the optical element 13 was formed on the base surface (surface of the mold roll) by cutting with a diamond tool having a prism shape at the tip. . As described above, a mold roll for molding the optical sheet 12 was produced.

And the optical sheet 12 was produced by the extrusion method using the said metal mold | die roll. FIG. 8 shows a schematic view of the extruder.
As shown in FIG. 8, the mold roll is arranged as a forming roll 42 so as to be close to the extruder 41. The thermoplastic polycarbonate resin is melted and molded into a sheet by an extruder 41, and the resin sheet is sandwiched between a forming roll 42 and a mold pressing roll 43 before the thermoplastic polycarbonate resin sheet is cooled and cured. Then, the optical element 13 and the optical protrusion 14 are respectively molded by the forming roll 42. As a result, a lens sheet (optical sheet 12) having a microlens shape as the optical protrusion 14 and a prism shape as the optical element 13 was obtained. In addition, all the thickness of the optical sheet 12 was 320 micrometers.
All the optical sheets 12 of Experiment 1 are made of a thermoplastic polycarbonate resin manufactured by Teijin Chemicals Ltd. The elastic modulus E of this thermoplastic polycarbonate resin is 2400 MPa, and the specific gravity is 1.2 g / cm ³ . Furthermore, regarding the molding of the optical element 13 and the optical protrusion 14, the transfer rate from the mold roll is very good, and the shaping rate is 98% or more. Further, when the optical sheet 12 of Experiment 1 is manufactured, the mold pressing roll 43 is a mirror surface roll, and the incident surface of the optical sheet 12 is only the smooth surface 15b having no dots (pressure adjusting unit 16). .

(Experiment 1: Verification of scratch resistance, chassis vibration test)
Based on the case where each optical sheet 12 obtained was mounted as in the second embodiment (FIG. 2), the scratch resistance when the produced optical sheet 12 and another optical sheet 31 were stacked was confirmed. Here, two types of diffusion sheet BS702 made by Ewa and prism sheet BEFIII made by Sumitomo 3M were installed as another optical sheet 31, and the presence or absence of scratches was confirmed before and after the vibration test.
A diffusion plate RM871 manufactured by Sumitomo Chemical Co., Ltd. is set as a diffusion plate 7 on a 37-inch LCD TV manufactured by Sharp, and the optical sheet 12 of the present invention is placed thereon, and a diffusion sheet BS702 or a prism sheet BEFIII is installed thereon as another optical sheet 31. A vibration test was performed. The vibration test device is a 2-way automatic switching type vibration test device G-8150-1HT-060 manufactured by Riken, and the vibration conditions are a frequency of 5 to 50 Hz, a sweep time of 3 minutes, and a constant acceleration of 1.0 G. Amplitude is 0.2 to 19.8 mm (peak), vibration direction is up / down / left / right / front / back, vibration time is up / down 60 minutes, left / right 15 minutes, front / back 15 minutes.
Regarding the evaluation of the vibration test, when either the diffusion sheet BS702 or the prism sheet BEFIII is mounted, there is no scratch on the exit surface of the optical sheet 12, or when the liquid crystal television is turned on even if the scratch occurs. The case where the scratch could not be visually confirmed on the display screen was determined as “pass”, and the case where the scratch occurred and the scratch was confirmed visually when the liquid crystal television was turned on was determined as “fail”.
The evaluation results are shown in Table 1.

  In Table 1, when the diffusion sheet BS702 is laminated as another optical sheet 31 and when the prism sheet BEFIII is laminated, it is OK (O), when the diffusion sheet BS702 is laminated, or When either or both of the prism sheets BEFIII were laminated, “NG” (x) was set.

  In Table 1, the housing vibration test of 42 types of optical sheets 12 appropriately combining two parameters of the height difference Tr−Tp between the optical protrusion 14 and the optical element 13 and the distance Pr between the optical protrusions 14. Shows the results. According to the evaluation results in Table 1, when the distance Pr between the optical protrusions 14 is sufficiently small, it is not necessary to increase the height difference Tr−Tp so much. On the other hand, when the ratio of the optical elements 13 is increased and the ratio of the optical protrusions 14 is decreased in order to obtain sufficiently high optical performance, the distance Pr between the optical protrusions 14 is increased, so that the optical elements 13 are prevented from being damaged. Therefore, it is necessary to increase the height difference Tr−Tp.

(Experiment 2: Examination of E and ρ)
In order to examine the selection of the material for the optical sheet 12, the optical sheet 12 was produced using three types of polycarbonate resin, ABS resin, and acrylic resin, and scratch resistance was evaluated.
Each of the optical elements 13 in these optical sheets 12 has a triangular prismatic prism lens shape with an apex angle of 90 ° and an arrangement pitch of 30 μm and a height Tp of 15 μm. Further, four types of heights of the optical projections 14 are set between 25 μm and 35 μm so that the height difference Tr−Tp is 10 μm to 20 μm. Furthermore, since the optical protrusion 14 has a microlens shape, the diameter Dr of the optical protrusion 14 is adjusted as needed to correspond to the desired height Tr of the optical protrusion 14. Further, two types of distances Pr of 500 μm and 600 μm are produced for the distance Pr between the optical protrusions 14, and the plurality of optical protrusions 14 are regularly arranged in a honeycomb structure (hexagonal fine structure).

(Experiment 2: optical sheet manufacturing method)
A microlens shape having a honeycomb structure (hexagonal fine structure) corresponding to the optical protrusions 14 was formed on the entire mold roll using a laser method. The distance Pr between the optical protrusions 14 was dealt with by adjusting the laser irradiation position. Further, the height Tr of the optical protrusion 14 was dealt with by adjusting the laser diameter at the time of laser irradiation and the time for the mold roll to be immersed in the acid solution and corroded after the laser irradiation. As a result, the mold shapes corresponding to the desired height Tr of the optical projections 14 could be obtained. Thereafter, this mold roll was set on a precision cutting machine, and a 90 ° prism shape corresponding to the optical element 13 was formed on the base surface (surface of the mold roll) by cutting with a diamond tool having a prism shape at the tip. . As described above, a mold roll for molding the optical sheet 12 was produced.

The optical sheet 12 of Experiment 2 was produced by an extrusion method for all three types of polycarbonate resin, ABS resin, and acrylic resin. FIG. 8 shows a schematic view of the extruder.
As shown in FIG. 8, the mold roll is arranged as a forming roll 42 so as to be close to the extruder 41. And after melt | dissolving each resin mentioned above, it shape | molds with the extruder 41, and before this resin sheet is cooled and hardened | cured, the resin sheet is inserted | pinched with the formation roll 42 and the metal mold | die press roll 43, and the formation roll 42 is used. The optical element 13 and the optical projection 14 are respectively molded. Thus, a lens sheet (optical sheet 12) having a microlens shape as the optical protrusion 14 and a prism shape as the optical element 13 was obtained. And all the thickness of the optical sheet 12 was 500 micrometers. When actually used as the optical sheet 12, the appropriate thickness of the optical sheet 12 differs depending on the resin from the viewpoint of not only optical performance but also environmental characteristics and moldability, but in Experiment 2, only the scratch resistance is evaluated. In order to carry out, not only the kind of resin but thickness was made constant.
The polycarbonate resin of Experiment 2 is a thermoplastic polycarbonate resin manufactured by Teijin Chemicals Ltd. similar to Experiment 1. The thermoplastic polycarbonate resin used in this experiment has an elastic modulus E of 2400 MPa and a specific gravity ρ of 1.2 g / cm ³ . Further, the ABS resin of Experiment 2 is used by blending a technopolymer ABS resin, the elastic modulus E of this ABS resin is 2400 MPa, and the specific gravity ρ is 1.02 g / cm ³ . Furthermore, the acrylic resin made from Mitsubishi Rayon is used for the acrylic resin of Experiment 2, the elastic modulus E of this acrylic resin is 3000 MPa, and the specific gravity ρ is 1.19 g / cm ³ . When the optical sheet 12 of Experiment 2 is manufactured, the mold pressing roll 43 is a mirror surface roll, and the incident surface of the optical sheet 12 is only the smooth surface 15b that does not have the pressure adjusting unit 16 (dots).

(Experiment 2: Scratch resistance verification: chassis vibration test)
Based on the case where each optical sheet 12 obtained is mounted in the second embodiment (FIG. 2), the scratch resistance when the produced optical sheet 12 and another optical sheet 31 are stacked was confirmed. Here, two types of diffusion sheet BS702 made by Eiwa and prism sheet BEFIII made by Sumitomo 3M were installed as another optical sheet 31, and the presence or absence of scratches was confirmed before and after the vibration test.
The vibration test device is a 2-way automatic switching type vibration tester G-8150-1HT-060 type made by vibration research, vibration conditions are vibration frequency 5-50Hz, sweep time round trip 3 minutes, constant acceleration 1.0G, amplitude 0.2-19.8 mm (peak), vibration direction up / down / left / right / front / rear, vibration time up / down 60 minutes, left / right 15 minutes, front / rear 15 minutes.
Regarding the evaluation of the vibration test, when either the diffusion sheet BS702 or the prism sheet BEFIII is mounted, there is no scratch on the exit surface of the optical sheet 12, or when the liquid crystal television is turned on even if the scratch occurs. The case where the scratch could not be visually confirmed on the display screen was determined as “pass”, and the case where the scratch occurred and the scratch was confirmed visually when the liquid crystal television was turned on was determined as “fail”.
The evaluation results are shown in Table 2.

  In Table 2, when the diffusion sheet BS702 is laminated as another optical sheet 31 and when the prism sheet BEFIII is laminated, it is OK (◯), when the diffusion sheet BS702 is laminated, or When either or both of the prism sheets BEFIII were laminated, “NG” (x) was set.

  In Table 2, the three parameters of the height difference Tr−Tp between the optical protrusion 14 and the optical element 13, the distance Pr between the optical protrusions 14, and the type of resin for the optical sheet 12 are appropriately combined 24 The result of the case vibration test of the kind of optical sheet 12 is shown. According to the evaluation results in Table 2, it is possible to reduce the amount of deflection by appropriately selecting and adjusting the resin (material) of the optical sheet 12, thereby preventing the optical element 13 from being damaged. In the results shown in Table 2, it is most preferable to select an acrylic resin as a material, and it is preferable to select an ABS resin and a polycarbonate resin in this order. However, changing the material affects not only the optical performance such as refractive index, transparency, and translucency, but also environmental properties, moldability, and cost. Therefore, it is sufficient to adjust the elastic modulus E and specific gravity ρ. It is difficult to obtain scratch resistance.

(Experiment 3: Examination of Td and Pd)
As the evaluation of the incident surface of the optical sheet 12, samples having different heights Td of the pressure adjusting portions 16 and distances Pd between the pressure adjusting portions 16 were prepared, and their scratch resistance was verified. The pressure adjustment parts 16 are all microlens shapes, and the aspect ratio (height Td of the pressure adjustment part 16 / diameter Dd of the pressure adjustment part 16) is all 0.5. Then, five types of distances Pd between the pressure adjusting portions 16 are prepared from 300 μm to 650 μm, and the plurality of pressure adjusting portions 16 are regularly arranged in a honeycomb structure (hexagonal fine structure). Further, four types of height Td of the pressure adjusting unit 16 are prepared between 15 μm and 50 μm, and the incident surface of the optical sheet 12 excluding the pressure adjusting unit 16 is a mirror surface (smooth surface 15b) having no uneven shape. It has become.

(Experiment 3: optical sheet manufacturing method)
A microlens shape having a honeycomb structure (hexagonal fine structure) corresponding to the pressure adjusting unit 16 was formed on the entire mold roll using a laser method. The distance Pd between the dots (pressure adjusting unit 16) was dealt with by adjusting the laser irradiation position. Further, the height Td of the pressure adjusting unit 16 is a dot of different height (pressure adjusting unit 16) by adjusting the laser diameter at the time of laser irradiation and the time for immersing and corroding the mold roll in the acid solution after the laser irradiation. The mold shapes corresponding to each were obtained. In addition, in the optical sheet 12 of Experiment 3, since the incident surface excluding the pressure adjusting unit 16 is a smooth surface 15b having a mirror shape without an uneven shape, a portion corresponding to the smooth surface 15b is formed. Only the molding of the microlens shape by the laser method was carried out.

And the optical sheet 12 was produced by the extrusion method using the said metal mold | die roll. FIG. 8 shows a schematic view of the extruder.
The mold roll is arranged as a mold pressing roll 43 in FIG. The thermoplastic polycarbonate resin is melted and molded into a sheet by an extruder 41, and the resin sheet is sandwiched between the forming roll 42 and the mold pressing roll 43 before the thermoplastic polycarbonate resin sheet is cooled and cured. The pressure adjusting part 16 was molded. In addition, all the thickness of the optical sheet 12 was 320 micrometers.
The optical sheet 12 of Experiment 3 is all produced by an extrusion method using a thermoplastic polycarbonate resin manufactured by Teijin Chemicals Limited. The thermoplastic polycarbonate resin used in the present invention has an elastic modulus E of 2400 MPa and a specific gravity of 1.2 g / cm ³ . This optical sheet 12 has a very good transfer rate from the mold, and the shaping rate is 98% or more.

(Experiment 3: Verification of scratch resistance, chassis vibration test)
Each optical sheet 12 obtained was evaluated for scratch resistance. First, considering the case of mounting in the first embodiment (FIG. 1), a diffusion plate RM871 made by Sumitomo Chemical is set as a diffusion plate 7 on a 37-inch sharp LCD TV, and the optical sheet 12 of Experiment 3 is placed thereon. Installed and conducted vibration test. Next, based on the case of mounting in the second embodiment (FIG. 2), a diffusion plate RM871 made by Sumitomo Chemical is set as a diffusion plate 7 on a 37-inch sharp LCD TV, and another optical sheet 32 is provided thereon. A Japanese diffusion sheet BS702 or a Goyo Paper Industries prism sheet GTL5000F was installed, and the optical sheet 12 of Experiment 3 was placed thereon, and a vibration test was performed. Each of these components was checked for scratches before and after the vibration test.
The vibration test equipment is a 2-way automatic switching type vibration test equipment G-8150-1HT-060 manufactured by Riken, and the vibration conditions are a frequency of 5 to 50 Hz, a sweep time of 3 minutes, a constant acceleration of 1.0 G, and an amplitude of 0 .2 to 19.8 mm (peak), vibration direction up / down / left / right / front / rear, vibration time up / down 60 minutes, left / right 15 minutes, front / rear 15 minutes.
Regarding the evaluation of the vibration test, if the incident surface of the optical sheet 12 is not damaged, or if it is generated, if it cannot be visually confirmed when the liquid crystal television is turned on, “pass”, a scratch occurs, and If the scratches are visible when the LCD TV is turned on, it was judged as “Fail”.
The evaluation results are shown in Table 3.

  In Table 3, when the optical sheet 12 of Experiment 3 is brought into contact with the diffusion plate RM871 manufactured by Sumitomo Chemical, the diffusion sheet BS702 is brought into contact, and the prism sheet GTL5000F is brought into “pass” in all three conditions. If OK (◯), scratch was generated even in one of the three conditions, and when the visual confirmation was possible (when “fail”), it was determined as NG (×).

  In Table 3, the result of the housing vibration test of 20 types of optical sheets 12 in which two parameters of the distance Pd between the pressure adjusting units 16 and the height Td of the pressure adjusting unit 16 are appropriately combined is shown. According to the results of Table 3, when the distance Pd between the pressure adjusting parts 16 is small, even if the height Td of the pressure adjusting part 16 is low, scratches are not generated and sufficient scratch resistance is obtained. However, if the ratio of the pressure adjusting unit 16 on the incident surface of the optical sheet 12 is increased, the optical performance of the optical sheet 12 is lowered. Therefore, when the distance Pd of the pressure adjusting unit 16 is increased, [Equation 2] is satisfied. In addition, the height Td of the pressure adjusting unit 16 needs to be selected higher.

(Experiment 4: Examination of removal of protective film)
In order to verify whether the protective film does not have to be attached to both the incident surface and the exit surface of the optical sheet 12, the optical element 13 and the optical projection 14 are formed on the exit surface, and the pressure adjustment is performed on the entrance surface. The optical sheet 12 in which the part 16 was molded was produced. At this time, the incident surface has a height Td of the pressure adjusting unit 16 of 20 μm, a distance Pd between the pressure adjusting units 16 of 500 μm, and the plurality of pressure adjusting units 16 each having a microlens shape have a honeycomb structure (hexagonal fine structure). Arranged regularly. The optical element 13 on the exit surface has a 90 ° prism shape with an arrangement pitch of 30 μm and a height (Tp) of 15 μm. At this time, the height Tr of the optical protrusion 14 and the distance Pr between the optical protrusions 14 are changed. (5 types each), scratch resistance evaluation was carried out.

(Experiment 4: Manufacturing method of optical sheet)
A mold roll (first mold roll) corresponding to the emission surface of the optical sheet 12 was produced using a laser system in the same manner as in Experiment 1. A microlens shape having a honeycomb structure (hexagonal fine structure) corresponding to the optical protrusions 14 was formed on the entire first mold roll. The distance Pr between the optical protrusions 14 was dealt with by adjusting the laser irradiation position. Further, the height Tr of the optical protrusion 14 corresponds to the optical protrusion 14 having a different height by adjusting the laser diameter at the time of laser irradiation and the time for the first mold roll to be immersed in the acid solution and corroded after the laser irradiation. A mold shape was obtained. Thereafter, the first mold roll is set on a precision cutting machine, and a 90 ° prism shape corresponding to the optical element 13 is formed on the base surface (the surface of the first mold roll) by cutting with a diamond tool having a prism shape at the tip. ). As described above, a first mold roll for molding the exit surface of the optical sheet 12 was produced.
In addition, a mold roll (second mold roll) corresponding to the incident surface of the optical sheet 12 was also produced using a laser method as in the case of the emission surface. Since only the microlens shape corresponding to the pressure adjusting unit 16 needs to be formed in the second mold roll on the incident surface, laser irradiation corresponding to the pressure adjusting unit 16 is performed, and then the second mold roll is turned into the acid solution. A shape corresponding to the pressure adjusting portion 16 was obtained by dipping and corrosion.

The optical sheet 12 was produced by an extrusion method using the two mold rolls. FIG. 8 shows a schematic view of the extruder.
The first mold roll corresponding to the emission surface is arranged as the forming roll 42, and the second mold roll corresponding to the incident surface is arranged as the mold pressing roll 43. Then, the thermoplastic polycarbonate resin is melted and molded into a sheet by the extruder 41, and the resin sheet is sandwiched between the forming roll 42 and the mold pressing roll 43 before the thermoplastic polycarbonate resin sheet is cooled and cured. Thus, the optical element 13, the optical protrusion 14, and the pressure adjusting unit 16 are simultaneously molded by the forming roll 42 and the mold pressing roll 43. The thickness of the optical sheet 12 is all 320 μm.
The optical sheet 12 of Experiment 4 is all manufactured by an extrusion method using a thermoplastic polycarbonate resin manufactured by Teijin Chemicals Limited. The thermoplastic polycarbonate resin used in the present invention has an elastic modulus E of 2400 MPa and a specific gravity of 1.2 g / cm ³ .

(Experiment 4: Verification of scratch resistance (packaging box test))
For each optical sheet 12 of Experiment 4 obtained, it was verified whether it was possible to remove the protective film for preventing surface shape damage. The purpose is based on the state of vibration until the molded optical sheet 12 is incorporated into the housing of the liquid crystal television. The optical sheet 12 that does not use a protective film on both the exit surface and the entrance surface was cut to 840 mm × 480 mm corresponding to the size of a backlight member of a 37-inch liquid crystal television, and 100 sheets were stacked with the exit surface facing up. These 100 optical sheets 12 were wrapped in a PE bag having antistatic performance and fixed with tape. Furthermore, it put into the general PE bag, the whole circumference | surroundings were wrapped with the air cap, and it fixed with the tape. Then, it was stored in a carton case of a predetermined size.
And the vibration test was implemented with respect to this carton case. The vibration test device and vibration conditions are the same as those of the case vibration test. The device is a bi-directional automatic switching vibration test device G-8150-1HT-060 type manufactured by Riken, and the vibration conditions are 5 to 50 Hz. Sweep time reciprocation 3 minutes, acceleration 1.0 G constant, amplitude 0.2 to 19.8 mm (peak), vibration direction up / down / left / right / front / rear, vibration time up / down 60 minutes, left / right 15 minutes, front / back 15 minutes.
The evaluation of the vibration test was judged by checking the incident surface of the optical sheet 12 before and after the vibration test and the presence or absence of scratches on the incident surface, and whether or not the scratches were visible when the scratches occurred. . And when there is no scratch, and even when the scratch is generated, when the optical sheet 12 is mounted on the 37-inch Sharp LCD TV in the first embodiment (FIG. 1), the scratch is not visible. It was set as a pass (◯), and when a scratch was visible, it was determined as a fail (x).
The evaluation results are shown in Table 4.

  In Table 4, the housing vibration test of 25 types of optical sheets 12 appropriately combining two parameters of the height difference Tr−Tp between the optical protrusion 14 and the optical element 13 and the distance Pr between the optical protrusions 14. Shows the results. According to the evaluation results in Table 4, when the pressure adjustment unit 16 is present on the incident surface of the optical sheet 12, the height Tr (height difference) of the optical protrusion 14 on the emission surface is compared with the case where the pressure adjustment unit 16 is not provided. It is necessary to further increase (Tr-Tp).

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

1,30 Display device 2,33 Backlight unit 3 Liquid crystal display element (image display element)
4 Light source 7 Diffuser 12 Optical sheet 13 Optical element 14 Optical protrusion 15 Translucent base material 15a One surface 15b The other surface (smooth surface)
16 Pressure adjustment part

Claims (13)

An optical sheet having a concavo-convex shape formed on at least one surface of the translucent substrate,
On one surface of the translucent substrate, an optical element for forming the uneven shape is formed in a shape or a dot shape extending in a one-dimensional direction along the one surface. Arranged along the plane of
Furthermore, a plurality of optical protrusions that protrude higher than the height of the optical element are formed on the one surface,
Each optical protrusion is formed into a shape having a curved surface shape at least at the tip in the protruding direction,
The distance between the optical projections adjacent to each other is set longer than the arrangement pitch of the optical elements,
The elastic modulus of the optical sheet is E [MPa], the density is ρ [g / cm ³ ], the thickness is h [μm],
The height of the optical element is Tp [μm],
The height of the optical protrusion is Tr [μm],
When the shortest distance among the distances between the optical protrusions is Pr [μm],

An optical sheet characterized in that   The optical sheet according to claim 1, wherein a tip of the optical protrusion is rounded.   The optical sheet according to claim 2, wherein the optical protrusion has a hemispherical shape or a substantially hemispherical shape.   The optical sheet according to claim 1, wherein the plurality of optical protrusions are regularly arranged.   The optical sheet according to any one of claims 1 to 3, wherein the plurality of optical protrusions are irregularly arranged.   6. The optical sheet according to claim 1, wherein an uneven shape is formed on the other surface of the translucent substrate. On the other surface of the translucent substrate, a plurality of pressure adjusting portions for forming the uneven shape are formed in a shape or a dot shape extending in a one-dimensional direction along the other surface,
The height of the pressure adjusting unit is Td [μm],
When the shortest distance among the distances between the pressure adjusting parts adjacent to each other is Pd [μm],

The optical sheet according to any one of claims 1 to 6, wherein:   The optical sheet according to claim 7, wherein a tip of the pressure adjusting unit is rounded.   The optical sheet according to claim 7 or 8, wherein the plurality of pressure adjusting units are regularly arranged.   The optical sheet according to claim 7 or 8, wherein the plurality of pressure adjusting units are irregularly arranged. Between the optical element, the optical protrusion, and the pressure adjustment unit,

The optical sheet according to any one of claims 7 to 10, wherein:   12. A display comprising at least a light source arranged on the other surface side of the translucent substrate with respect to the optical sheet according to any one of claims 1 to 11. Backlight unit for equipment.   An image display element that defines a display image according to transmission / light-shielding at least in units of pixels is arranged on the one surface side of the optical sheet in the backlight unit according to claim 12. A display device.

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