JP2012083740A - Optical sheet, optical member, surface light source device, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet with a scratch resistance capable of preventing damage of the optical sheet itself when the optical sheet is disposed adjacent to another optical member or itself, the optical sheet having a rugged coating surface that is a rough surface on an opposite side of an optical element surface such as a prism surface; and to provide a surface light source device using the same and a liquid crystal display device.SOLUTION: An optical sheet 10 includes a unit optical element 2 disposed on one surface 1p of a main body section 1, and a rugged coating film 3 having a rough surface by small protrusions, on the other surface 1q. As for the hardness He of the optical element surface Pe and the hardness Hm of the rugged coating film surface using pencil hardness (with a load of 1000 g and speed of 1 mm/s) conformed to JIS K5600-5-4 (1999), the hardness Hm is F or more, and Hm≥He. Further, assuming that 1 unit harder hardness on a pencil hardness scale is defined as +1, it is favorable that the respective levels of hardness satisfy He+3≥Hm≥He+2. Furthermore, two optical sheets may be stacked with the surface/backside facing the same direction. The optical sheet is used for a surface light source device and a liquid crystal display device.

Description

The present invention relates to an optical sheet that changes the traveling direction of light, an optical member using the optical sheet, a surface light source device, and a liquid crystal display device using the surface light source device.
In particular, an optical sheet having a rough coating film with a rough outer surface or a smooth coating film with a smooth surface on the opposite side of the optical element surface by a columnar prism, etc. An optical sheet that is excellent in scratch resistance because the front and back surfaces of the optical sheet itself are hard to be damaged even if the optical sheets are in contact with each other or in contact with other members by storing and transporting in a roll. About. The present invention also relates to an optical member using the same, a surface light source device, and a liquid crystal display device using the surface light source device.

In a transmissive liquid crystal display device, there is known an optical sheet that is arranged on a light exit surface of a back light source and collects the emitted light to improve luminance.
For example, in Patent Document 1, a surface opposite to a prism surface on which triangular prism unit prisms and the like are arranged as unit optical elements has a large number of minute protrusions for forming a gap whose height is not less than the wavelength of the light source light and not more than 100 μm. A faced optical sheet is disclosed. By making the opposite side of the prism surface a rough surface instead of just a smooth surface, when the light guide plate is placed adjacent to the opposite side of the prism surface of the optical sheet, the optical contact with the light guide plate is improved. It is possible to effectively prevent in-plane luminance unevenness, interference fringes, and the like due to the optical contact.

  In addition, a rough surface having many such fine protrusions on the surface can be obtained by a hot embossing method, a molding method using an ultraviolet ray or electron beam curable resin solution and a molding die (2P method: photopolymer method), and fine particles in a resin solution. It can be formed by a coating method or the like in which irregularities due to fine particles appear on the surface of the coating film of the paint contained in the coating to make it rough. Among them, the coating film method has an advantage that a thermoplastic resin or a thermosetting resin can be used for the resin, and fine particles can use resin beads or the like, which can be easily and inexpensively formed as compared with other methods.

However, although the optical adhesion can be prevented by the rough surface, the surface of the other optical member disposed adjacent to the back side of the optical sheet due to fine projections on the rough surface or fine particles dropped from the inside of the coating film, I was hurt.
Therefore, in Patent Document 2, monodisperse spherical beads having a half-value width of 1 μm or less as a fine particle to be contained in the coating film in order to prevent such other adjacently disposed optical members from being damaged. We are proposing a technology that uses.

  It is also important that the optical sheet does not decrease in luminance due to its presence. Therefore, in Patent Document 3, in the optical sheet having one lens surface, a low refractive index layer is provided on the other surface serving as the light incident surface to prevent unnecessary light reflection on the light incident surface, and in the front direction. An optical sheet with improved brightness is proposed.

Japanese Patent No. 3518554 Japanese Patent No. 3913870 Japanese Patent No. 8-286005

However, even if the scratches of other optical members are improved by using monodispersed fine particles as proposed in Patent Document 2, the optical sheet itself is still scratched, and it is hoped that this will be eliminated. Mareta.
That is, the phenomenon in which the optical sheet scratches itself rather than other optical members first occurs when the optical sheet is shipped as a product at a stage before the optical sheet is assembled to the surface light source device. The optical sheet is usually manufactured in the form of a belt-like sheet from the viewpoint of productivity, and is wound up in a roll, stored, transported, and cut into single-sheet sheets of a shape and size according to the application when necessary. Ship. In addition, the optical sheets after being cut into single sheets are stacked and stored and transported. In these roll states and stacked states, the surface (outermost surface) of the optical sheet and the back surface (opposite outermost surface) of the optical sheet stacked thereon are in contact with each other. In this state, the front and back surfaces that are in contact with each other are rubbed due to vibrations during storage and transportation, and this causes damage and further damage due to the dropped fine particles. Such scratches occur on either the prism surface or the coating surface (front and back surfaces) on the opposite side of the prism surface.
By the way, such scratches on the front and back surfaces until the optical sheet is used can be obtained by attaching a protective film to the front and back surfaces and peeling the protective film when assembling the optical sheet to a surface light source device or the like. ,Resolve. However, from the viewpoint of cost reduction and resource saving, it is preferable that the protective film that is ultimately unnecessary can be omitted if possible.

Next, the phenomenon in which the optical sheet damages itself rather than other optical members occurs secondly after the optical sheet is assembled into a surface light source device or the like. For example, this phenomenon occurs when two optical sheets described in JP-B-1-37801, JP-A-10-506500, and the like are overlaid and assembled. Each of the two optical sheets to be overlaid usually has a triangular prism on one surface as unit optical elements arranged in the arrangement direction, and the two optical sheets are arranged in the arrangement direction of the triangular prisms. Are superimposed in the same direction so that they are orthogonal to each other.
In such a surface light source device having a configuration in which a plurality of optical sheets are adjacently stacked, or an optical device such as a liquid crystal display device using the surface light source device, even after each optical sheet is assembled, Similarly, scratches may occur on the front and back surfaces of the optical sheet due to the influence of vibration. This is because even in an optical apparatus, vibration may be applied when stored and transported as a semi-finished product or a commercial product.
Moreover, even if the optical sheets are not overlapped, if another optical member such as a light guide plate or a liquid crystal panel and the optical sheet are disposed adjacent to each other, vibration due to storage, transportation, etc. in contact with the other optical members Similarly, the front and back surfaces of the optical sheet itself may be damaged.
The unit optical element such as a prism can receive an external force in a relatively wide area, and does not include an object that easily falls off, such as fine particles. Therefore, it is possible to design to prevent damage caused by an external force by using a resin having flexibility and resilience as described in JP-A-2009-37204. On the other hand, in the case of a concavo-convex coating film, in addition to concentration of stress in a relatively small area, it also contains fine particles that easily fall off. there were.

In addition, the roughening of the contact surface for preventing optical adhesion may be dealt with by roughening the other optical member in contact with the optical sheet in addition to the roughening of the optical sheet. Patent Document 1 [0015] and FIG. 4 also describe such a form. For example, when the other optical member that contacts the optical sheet is a light diffusing sheet, the light emitting surface (and the light incident surface) is roughened.
It is not necessary to roughen the coating surface of the optical sheet for such applications. And according to the smoothed coating-film surface, the damage of the prism surface adjacent to a coating-film surface and the other optical member adjacent to a coating-film surface can be reduced. Further, even when the prism surface or the optical member adjacent to the coating surface is damaged, the damage is relatively minor and the influence on the optical characteristics is reduced.
However, since the surface of the coating film is smooth, scratches are conspicuous. It is inevitable that even scratches that do not affect the optical characteristics are judged to be defective in the appearance inspection or the commercial value is evaluated low. On the other hand, for the prism surface, since scratches are difficult to be visually recognized due to the streaky appearance of the prism surface and light collection or light diffusion characteristics, scratches are acceptable if they do not affect the optical characteristics. There is also.
Therefore, even when the coating film surface opposite to the prism surface is a smooth surface, the problem of scratches due to friction between the front and back surfaces of the optical sheet remains. In particular, reduction of scratches on the coating surface is an important issue, and when aiming for a protective film-less, it is necessary to deal with scratches due to contact between optical sheets as described above.

  In addition, the low refractive index layer provided from the viewpoint of improving brightness often has a thin thickness of about 1/4 of the wavelength of light to be antireflective, and is easily scratched by contact with other optical members. Easy to stick. Further, such a low refractive index layer itself does not take into consideration prevention of optical adhesion and damage of other optical members or optical sheets themselves, and these damages cannot be prevented.

That is, the object of the present invention is to make the surface opposite to the optical element surface made of a prism or the like into a coating film surface made of a rough surface in order to prevent optical adhesion, or to prevent optical adhesion. As for the optical sheet configured as a coated film surface consisting of a smooth surface, the front and back of the optical sheet are in contact with each other by using two optical sheets stacked or stored and transported in a roll. Alternatively, it is an object of the present invention to provide an optical sheet that is excellent in scratch resistance, and that can improve brightness, at least the coating film surface of the optical sheet itself is hardly scratched even when it comes into contact with other members.
Another object of the present invention is to provide an optical member, a surface light source device, and a liquid crystal display device in which an optical member such as the optical sheet is hardly damaged by using such an optical sheet.

The optical sheet according to the present invention is
An optical sheet having a pair of opposing surfaces,
A sheet-like body,
Unit optical elements arranged on one surface of the main body, and
A coating film provided on the other surface of the main body,
One of the pair of surfaces is configured as an optical element surface formed by the unit optical element,
The other of the pair of surfaces is formed by a coating surface comprising the surface of the coating film,
When the hardness He of the optical element surface and the hardness Hm of the coating surface are evaluated using pencil hardness measured according to JIS K5600-5-4 (1999) (load 1000 g, speed 1 mm / s) The hardness Hm is F or more (hardness Hm ≧ F), and the hardness Hm is more than the hardness He (hardness Hm ≧ hardness He).

In the optical sheet according to the present invention, when the hardness of one unit on the pencil hardness scale is +1,
Hardness He + 3 ≧ Hardness Hm ≧ Hardness He + 2
The relationship may be satisfied.

  In the optical sheet according to the present invention, the refractive index Nm of the resin forming the coating film may be smaller than the refractive index Ns of the portion forming the other surface in the main body.

  In the optical sheet according to the present invention, the coating film may be a concavo-convex coating film in which the coating film surface forms a rough surface by fine protrusions, or a smooth coating film in which the coating film surface is smooth. There may be.

The optical member according to the present invention includes two optical sheets according to the present invention described above,
Two optical sheets are overlapped with each other in the same direction.

A surface light source device according to the present invention comprises:
A light source;
Any of the optical sheets according to the present invention described above.

The liquid crystal display device according to the present invention comprises:
Any of the surface light source devices according to the present invention described above;
A transmissive liquid crystal display panel disposed to face the surface light source device.

FIG. 1 is a perspective view showing an optical sheet for explaining an embodiment of the present invention. FIG. 2 is a graph for explaining a preferable relationship between the pencil hardness of the front and back surfaces of the optical sheet. FIG. 3 is a cross-sectional view showing a modification of the optical sheet. FIG. 4 is a cross-sectional view showing another embodiment (two-sheet superposition form) of an optical sheet. FIG. 5 is a cross-sectional view showing still another embodiment (two-sheet superposition form) of the optical sheet. FIG. 6 is a cross-sectional view showing a surface light source device and a liquid crystal display device including the optical sheet of FIG. 7 is a cross-sectional view showing a surface light source device and a liquid crystal display device including the optical sheet of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are conceptual diagrams, and the scale relationships, aspect ratios, and the like of components may be exaggerated.

<[A] Outline>
First, an optical sheet according to an embodiment of the present invention is shown in the perspective view of FIG. The optical sheet 10 shown in the figure has unit columnar prisms having a triangular section as unit optical elements 2 on one surface 1p (surface in the drawing in the drawing) of the sheet-like main body portion 1 and their ridge directions are parallel to each other. A plurality of prism groups are arranged, and the other surface 1q of the main body 1 has an uneven coating film 3 whose outermost surface is a rough surface. As an example, the uneven coating film 3 is formed by applying a coating containing fine particles in a binder resin to the main body 1, and the outermost surface is roughened by forming minute protrusions on the outermost surface due to the presence of fine particles. Face. In the optical sheet 10, the outermost surface on the side having the unit optical elements 2 is the optical element surface Pe, and the outermost surface on the side having the uneven coating film 3 is the coating film surface Pm.

  In FIG. 1, the X, Y, and Z axes of the orthogonal coordinate system are parallel to the arrangement direction of the unit optical elements 2 (unit columnar prisms in this embodiment), and the Y axis is the unit optical element 2 (unit columnar shape). The Z axis is parallel to the thickness direction of the main body 1 and the thickness direction of the uneven coating film 3.

  In the present invention, the coating film formed on the other surface 1q of the main body 1 has a smooth surface instead of the uneven coating film 3 as in the optical sheet 10 shown in the sectional view of FIG. There is also a form which makes the coating film 4. In the present invention, as will be described later, the coating films 3 and 4 have a predetermined hardness from the viewpoint of scratch resistance. From this point of view, it can be said that the coating films 3 and 4 are given scratch resistance, and such a smooth coating film 4 is also called an abrasion resistance coating film. Therefore, in this specification, the smooth coating film 4 is also referred to as an abrasion-resistant coating film.

  And the refractive index Nm of resin which comprises these uneven | corrugated coating film 3 and smooth coating film (scratch-resistant coating film) 4 is the part (the other surface 1q of a main-body part) which faces the coating film of the sheet-like main-body part 1. The refractive index Ns of the portion formed) is smaller. As a result, by providing the uneven coating film 3 and the smooth coating film 4, the luminance does not decrease, and conversely, the luminance can be improved.

  Returning to the embodiment of FIG. 1, in this embodiment, the hardness He of the optical element surface Pe formed by the arrayed unit optical elements 2 and the uneven coating film 3 or the smooth coating film 4 (collectively referring to both) The hardness Hm of the coating surface Pm consisting of the surface of the “coating film” or “coating film 3, 4”) is a load of 1000 g, speed according to JIS K5600-5-4 (1999). When the pencil hardness measured under the condition of 1 mm / s is evaluated, the hardness Hm is F or higher, and the hardness Hm ≧ hardness He, that is, the hardness Hm is higher than the hardness He.

  FIG. 2 is a graph showing preferred regions of the hardness He and the hardness Hm, with the hardness He of the optical element surface Pe on the horizontal axis (X axis) and the hardness Hm of the coating film surface Pm on the vertical axis (Y axis). As shown in the drawing, the region Ea is a region where the hardness Hm is F or more and the hardness Hm ≧ hardness He is satisfied. By setting the hardness He and the hardness Hm in the region Ea, the scratch resistance of the optical sheet 1 itself can be improved. As for the hardness He, for example, even if it is softer than “F” such as “B”, it is deformed when an external force is applied, and when it is released from the external force, it returns to its original shape by an elastic restoring force. Can be effectively prevented, and it is not particularly necessary to set F or higher as in the hardness Hm of the coating surface Pm. Usually, the hardness He of the optical element surface is set to 4B or more.

  More preferably, by setting the region Eb with hardness He + 3 ≧ hardness Hm ≧ hardness He + 2, the scratch resistance of the optical sheet can be remarkably improved, and particularly when the optical sheets are superposed, scratches are generated. Can be effectively prevented. In particular, when the optical element surface Pe and the back side surface Pm are in contact with each other and are strongly subjected to friction as shown in FIGS. 4 and 5, the two optical sheets 10 have a hardness Hm−hardness He> 3. There is a possibility that the optical element surface Pe is too soft compared with the coating film surface Pm, and the optical element surface Pe is damaged. Conversely, when hardness Hm−hardness He <1, the optical element surface Pe is too hard (becomes brittle) with respect to the coating film surface Pm, and the optical element surface Pe may be damaged, The coating surface Pm may be damaged by the hard optical element surface Pe.

<[B] Definition of terms>
Next, definitions of major terms used in the present invention will be explained here.

The “one surface 1p” of the main body 1 is a surface on the side where the unit optical elements 2 of the main body 1 are arranged. Further, the “one surface 1p” side of the optical sheet 10 is referred to as an “optical element side”. The “one surface 1p” is a virtual surface that does not actually exist on the main body 1 itself as a surface serving as an outermost surface or an interface when the unit optical elements 2 are arranged so as to be filled without gaps to constitute an optical element group. It becomes a surface. Further, when the unit optical elements 2 are arranged with a gap therebetween to constitute an optical element group, the “one surface 1 p” of the main body includes an actual surface exposed between the unit optical elements 2.
The “optical element surface Pe” is a surface composed of only the unit optical elements 2 arranged without a gap when one surface 1p of the main body 1 is completely filled with the unit optical elements 2 arranged without a gap. Further, when the unit optical elements 2 are arranged on the one surface 1p of the main body 1 with a gap, the optical element surface Pe includes the surface of the unit optical elements 2 arranged with a gap and the unit optical element 2 And one surface 1p of the main body 1 exposed therebetween.
When the optical sheet 10 is used in a direction in which the “optical element side” is the “light exit side”, the “optical element side” is the “observer side” that observes the display image when the optical sheet 10 is applied to the display. .
The “front and back surfaces” is a general term for both surfaces when the mutual relationship between the optical element surface Pe and the coating film surface Pm is a problem. Here, the terms “front (surface)” and “back (surface)” do not mean front or back surfaces, particularly based on an image observer, a light source, or the like.
In addition, “the two optical sheets are overlapped in the same direction” means that two or more optical sheets 10a, 10b,... Are as shown in FIG. 4 and FIG. The optical element surfaces Pe, Pe,... Are superposed so that they all face the same direction (upward in FIGS. 4 and 5), and the optical element surfaces Pe of one optical sheet 10b are adjacent to each other. It means making it face the coating film surface Pm of the sheet 10a.

The “main cut surface” refers to a cross section parallel to the normal nd (see FIG. 1) standing on “one surface 1p” of the main body 1 when the unit optical element 2 has a columnar shape such as a unit columnar prism. Of these, a section parallel to the arrangement direction of the unit optical elements 2 is meant. In other words, the cross section is parallel to the normal line nd and orthogonal to the ridge line of the unit optical element 2 (unit columnar prism). In FIG. 1, the Z axis is parallel to the normal line nd.
“Smooth” means smooth in an optical sense. That is, it means the degree to which a certain percentage of visible light is refracted while satisfying Snell's law on the surface constituting the optical sheet 10. Therefore, for example, a surface having a ten-point average roughness Rz (JISB0601: 1994 version) less than the shortest visible light wavelength (0.38 μm) corresponds to a sufficiently smooth surface.
The “rough surface” means an uneven surface that does not satisfy the “smooth” condition. That is, if the 10-point average roughness Rz value of a certain surface (outermost surface) is 0.38 μm or more, it can be said to be a rough surface. However, in order to sufficiently achieve the optical effects of the rough surface such as the optical adhesion prevention effect and the light diffusion effect over the entire visible light wavelength band, the surface 10-point average roughness Rz value is the longest visible. It is preferable that the light exceeds 0.78 μm. Usually, the ten-point average roughness Rz value of the rough surface is about 1 to 10 μm.
Terms that specify shape and geometric conditions, such as “triangle”, “circular”, “elliptical”, “parallel”, “orthogonal”, “polyline”, etc., are not bound to a strict meaning. It is a term that is interpreted to include an error, an allowable range, or an equivalent range to the extent that a similar function can be expected, including limitations in manufacturing technology and errors during molding.

<[C] Optical sheet>
Hereinafter, each layer of the optical sheet will be further described.

[Main body]
As the main body 1, a polyester resin such as poly (ethylene terephthalate) or polyethylene naphthalate, a transparent resin material such as an acrylic resin, a polycarbonate resin, or a polyolefin resin, or a transparent inorganic material such as glass or ceramics can be used. .
The main body 1 is “sheet-like”, and “sheet” here also includes the concept of “film” and “plate”, and these terms are different from each other based only on the difference in designation. It is not distinguished. That is, they are not distinguished by thickness or rigidity. For example, the thickness of the main body 1 is 25 μm to 5 mm or the like.
However, in terms of excellent productivity, the optical sheet is preferably flexible enough to be wound on a roll. In this respect, it is preferable that the optical sheet is not called a rigid so-called plate or substrate. Considering this point, the thickness of the main body 1 is preferably about 25 μm to 500 μm.
The other surface 1q of the main body 1 is a surface on which the coating films 3 and 4 are formed, and is usually a smooth surface, but may be a non-smooth surface.
Moreover, both the 1st surface 1p and the other surface 1q of the main-body part 1 are normally planes, and when the main-body part 1 is a plate, it will become flat form.

(Formation of main body and unit optical element)
In addition, the part of the optical sheet 10 which consists of the main-body part 1 and the unit optical element 2 can be formed from a conventionally well-known method and a transparent material. For example, an optical element group formed by arranging unit optical elements 2 and the main body 1 are integrally molded with the same material by a molding method such as a melt extrusion method, an injection molding method, or an embossing method by hot pressing. Can be formed. Alternatively, a resin liquid is brought into contact with the main body 1 formed or molded in advance and the resin liquid is sandwiched between the mold and the main body 1 and solidified by a chemical reaction of a curing reaction or cooling. In addition, the layers can be formed as different layers by a molding method in which an optical element group such as a prism shape is formed on the surface. The unit optical element 2 is prepared by a method of curing with ionizing radiation using an ionizing radiation curable resin that is cured with ionizing radiation such as ultraviolet rays or electron beams in the resin liquid, so-called 2P method (photopolymer method). You can also. In this case, when a transparent substrate such as a resin sheet is used as the main body 1, an optical element group composed of a resin layer is formed on the transparent substrate. That is, a resin layer having a slight thickness is formed also in the valley portion between the adjacent optical elements 2. In such a case, the main body portion 1 is a resin layer having a resin thickness in the valley portion, the resin layer (land portion) extending to a portion other than the valley portion and the valley portion, a transparent substrate, And includes a part of the thickness of the resin layer formed on the transparent substrate.

(Unit optical element)
The unit optical element 2 is typically a unit columnar prism, but other than this, a microlens (a device in which a large number of microlenses are arranged is called a fly-eye lens or an eyelet lens) is conventionally used. Various known unit optical elements can be appropriately employed.
Hereinafter, the unit columnar prism will be further described.

(Unit columnar prism)
The unit columnar prism is typically a unit prism having a triangular shape with a main cut surface having a base on the main body 1 side. As such unit columnar prisms, various conventionally known prisms can be appropriately employed. The main cutting plane shape is not only a straight line shape such as a triangle, quadrangle, pentagon, hexagon, etc., but also a shape with a curve in part, a shape only with a curve (for example, a circle, an ellipse, a fence line, A part of a curve such as a hyperbola or a sine curve may also be included.
When the main cut surface is a part of a curve such as a circle or an ellipse, it can also be called a unit columnar lens, and the unit columnar prism in the present invention may include a unit columnar lens.

Further, the unit columnar prisms do not have to have the same shape and the same size as each of the arranged unit columnar prisms, and one or more of the shapes and sizes may be different or may be irregularly different. Further, the arrangement of the unit columnar prisms may be different from each other in the arrangement period other than the regular arrangement in the same arrangement period, or may be irregularly different.
Further, as the unit columnar prism, the height of the ridge line described in Japanese Patent No. 3119471, Japanese Translation of PCT International Publication No. 2002-504698, etc. is changed into a polygonal line shape, and the shape is not constant. It is a kind of a preferable shape in that various problems caused by optical adhesion such as can be prevented. In order to manufacture a prism group in which unit columnar prisms in which the height of the ridgeline is changed to a polygonal line are manufactured, for example, cylindrical (cylindrical) molding conventionally used for manufacturing this type of prism group is used. When the mold is manufactured with a cutting tool, it can be easily manufactured by cutting while changing the cutting depth of the cutting tool into a polygonal line.

(Specific examples of dimensions and distribution)
Here, if the specific example of the dimension of a unit columnar prism and the optical element group (prism group) which consists of it is shown, the width | variety of the bottom face (dimension in a prism arrangement direction) of a unit columnar prism will be 10-500 micrometers, and the top part which forms a ridgeline When the main cutting plane shape is an isosceles triangle, the apex angle forming the ridge line is 80 to 110 °, preferably 90 °.

  Similarly to the unit columnar prism, each of the arranged microlenses may have one or more different shapes and dimensions other than the same shape and size, and may be irregularly different. good. Further, the arrangement of the microlenses may be other than the regular arrangement with the same arrangement period, the arrangement period may be different, and the arrangement may be irregularly different. A typical microlens is a part of a sphere or ellipsoid whose bottom shape is a circle or an ellipse, but other shapes (for example, a cone or a pyramid) may be used.

  As described above, the unit optical element 2 typically includes a unit columnar prism and a microlens, but the unit optical element 2 provided in the optical sheet 10 includes a unit columnar prism (can include a unit columnar lens). Or a microlens alone, or may have both a unit columnar prism and a microlens as disclosed in Japanese Patent Application Laid-Open No. 2010-44379.

[Uneven film]
Among the coating films, the uneven coating film 3 is a transparent layer containing at least a binder resin and having an outermost surface exposed to the outside (such as an ambient atmosphere) as a rough surface. The concavo-convex coating 3 may have a structure that does not include fine particles, and may have a concavo-convex surface (rough surface) formed on the surface of the coating film by a mold, or may include a binder resin and fine particles. Concavities and convexities may be formed by protrusion to the film surface. Hereinafter, in particular, a mode in which the binder resin contains fine particles will be described in detail.
In the case of such a form, the concavo-convex coating film 3 includes a binder resin and fine particles as essential components, and further, by applying a resin composition (coating liquid, paint) containing various additives, solvents, and the like as necessary. Can be formed. When the resin composition contains a solvent, it may cause a decrease in film thickness due to shrinkage of the coating film volume during solidification. By reducing the film thickness, fine protrusions are formed so that the fine particles are lifted, and the surface of the uneven coating film 3, that is, the coating film surface Pm can be formed as a rough surface. Further, a resin that is cured by a crosslinking reaction, an addition polymerization reaction, or the like may be used for the binder resin to cause volume reduction at the time of curing. Also in this case, the rough surface can be formed by projecting the fine particles on the surface of the uneven coating film by volume shrinkage.
In any form including the fine particles, the protruding fine particle surface may be either coated with a binder resin or not coated with a binder resin. However, in order to prevent the protruding fine particles from falling off and to further improve the effect of preventing scratches on the front and back surfaces of the optical sheet itself aimed at by the present invention, a form in which the protruding fine particle surface is coated with a binder resin is preferable.

As the binder resin, first, from the viewpoint of firmly fixing the fine particles in the binder resin matrix and preventing peeling of the uneven coating film 3 itself from the main body 1, the adhesion between the main body 1 and the fine particles is high. A strong transparent resin may be used as appropriate.
As such a binder resin, a transparent resin such as a thermoplastic resin or a curable resin such as a thermosetting resin or an ionizing radiation curable resin can be used. For example, the thermoplastic resin is an acrylic resin, a polyester resin, a polyurethane resin, a vinyl chloride-vinyl acetate copolymer, and the thermosetting resin is a thermosetting acrylic resin, a thermosetting polyester resin, Examples of the thermosetting polyurethane resin include ionizing radiation curable resins such as acrylic resins, epoxy resins, and polyester resins that are cured by irradiation with ionizing radiation such as ultraviolet rays and electron beams. In the case of a curable resin, a curing agent, a polymerization disclosure agent, and the like can be included as part of the resin component.
Among the various binder resins mentioned above, the ionizing radiation curable resin, in particular, is quick in curing and excellent in productivity, and also can increase the coating strength of the formed uneven coating film 3 and have excellent scratch resistance. Is preferable.

As the ionizing radiation curable resin, monomers and / or prepolymers that are polymerized and cured by a reaction such as crosslinking with ionizing radiation are used.
Examples of the monomer (monomer) include radically polymerizable monomers such as methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, Monofunctional (meth) acrylates such as dicyclopentenyl (meth) acrylate, dipropylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane Tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol tetra (me ) Acrylates, polyfunctional (meth) acrylate various (meth) acrylates such as such as dipentaerythritol hexa (meth) acrylate. Here, the expression (meth) acrylate means acrylate or methacrylate.
Examples of the cationic polymerizable monomer include alicyclic epoxides such as 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate, glycidyl ethers such as bisphenol A diglycidyl ether, 4-hydroxybutyl vinyl ether And vinyl ethers, and oxetanes such as 3-ethyl-3-hydroxymethyloxetane.

Moreover, as said prepolymer (or oligomer), as a radically polymerizable prepolymer, for example, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, triazine (meth) acrylate, silicon (meth) acrylate And various (meth) acrylate prepolymers such as polythiol prepolymers such as trimethylolpropane trithioglycolate and pentaerythritol tetrathioglycolate, and unsaturated polyester prepolymers.
In addition, examples of the cationic polymerizable prepolymer include a novolac type epoxy resin prepolymer and an aromatic vinyl ether type resin prepolymer.
These monomers or prepolymers may be used alone or in combination of two or more types of monomers, two or more types of prepolymers, or one type of monomer, depending on the required performance, coating suitability, etc. A mixture of the above and one or more prepolymers can be used.

  When ultraviolet rays or visible rays are employed as the ionizing radiation, a photopolymerization initiator is usually added. As a photopolymerization initiator, in the case of a radical polymerizable monomer or prepolymer, a compound such as a benzophenone-based, thioxanthone-based, benzoin-based, or acetophenone-based compound, or in the case of a cationic polymerization-based monomer or prepolymer, Metallocene, aromatic sulfonium and aromatic iodonium compounds are used. These photopolymerization initiators are added in an amount of about 0.1 to 5 parts by mass with respect to 100 parts by mass of the composition comprising the monomer and / or prepolymer.

((Refractive index))
Further, as the binder resin, secondly, from the viewpoint of improving luminance, the refractive index Nm of the resin is set to a portion facing the coating surface in the main body portion 1 (portion facing the other surface 1q). A resin having a smaller refractive index Ns than that of the resin is employed. As a result, the loss of light due to diffusion, reflection, etc. that can occur on the coating surface of the uneven coating 3 provided on the light incident surface side of the optical sheet 10 can be suppressed. As a result, the luminance can be improved accordingly. Further, the refractive index difference at the interface with the air layer is such that the surface of the uneven coating film 3 with a refractive index Nm smaller than the refractive index Ns is smaller than when the surface of the main body 1 having a refractive index Ns is exposed. Smaller when exposed. Accordingly, also in this respect, the luminance can be improved by the presence of the uneven coating film 3 having a small refractive index difference from air.

The refractive index Nm and the refractive index Ns are set so that the refractive index Nm <the refractive index Ns. Further, as is known in the design theory of optical antireflection films, in order to minimize the reflection loss of incident light and maximize the brightness enhancement effect, Nm = (Ns) ^1/2. (() ^1/2 means the square root of ()) In general, it is often difficult to meet this relationship exactly with materials that can be used, but as much as possible A design that approaches this relationship is good.
In order to make the refractive index Nm of the resin forming the uneven coating film 3 smaller than the refractive index Ns of the main body 1, when the main body 1 is made of, for example, polyethylene terephthalate, the refractive index Ns is 1.65. The resin forming the coating film 3 may be a resin having a refractive index Nm <1.65, and particularly, Nm = (1.65) ^1/2 = 1.29 is optimal.

Two or more binder resins may be used in combination to adjust various physical properties. Among them, a known low refractive index resin is used in combination as a preferred resin for adjusting and lowering the refractive index. Alternatively, a low refractive index resin may be used alone. As the low refractive index resin, for example, a fluorine atom-containing polymer can be used. The fluorine atom-containing polymer may be used alone, but in order to adjust physical properties such as adhesion, a fluorine atom-free polymer containing no fluorine atom may be used in combination. In addition, the fluorine atom-containing polymer itself may be a polymer (copolymer) in which a fluorine atom-free monomer is used in addition to the fluorine atom-containing monomer. The physical properties may be adjusted.
As the fluorine atom-containing polymer, an ionizing radiation curable polymer can be preferably used in terms of coating film strength and rapid curing. For example, a fluorine atom-containing acrylate ionizing radiation curable resin. According to the fluorine atom-containing polymer, the refractive index Nm can be 1.45 or less. The fluorine atom-containing acrylate ionizing radiation curable resin may be used in combination with a fluorine atom-free acrylate ionizing radiation curable resin that does not contain fluorine atoms. For example, combined use of polyfunctional acrylate monomers.

  Moreover, as a fluorine atom containing polymer, a commercial item can also be used. For example, Opstar TU2181-6, Opstar TU2181-7, Opstar TU2202, Opstar JN35, Daikin Industries, Ltd. OPTOOL AR110, OPTOOL AR100, etc. manufactured by JSR Corporation may be used.

Moreover, in order to reduce the refractive index of a coating film, the uneven | corrugated coating film 3 may contain a low refractive index agent other than binder resin. A well-known thing can be used as a low refractive index agent. For example, solid inorganic fine particles having a low refractive index per se, hollow fine particles having cavities and voids inside, and the like can be used. Here, the hollow fine particles mean fine particles having a hollow structure having a cavity inside or a porous structure having a gap inside.
Solid inorganic fine particles include silica (refractive index 1.45), magnesium fluoride (refractive index 1.38), Na ₃ AlF ₆ (refractive index 1.33), and the average particle size is, for example, 10 nm to 100 nm. The hollow fine particles are typically hollow silica having cavities inside, and the average particle size can be set to, for example, 10 nm to 100 nm.
In addition, a low refractive index agent is normally used in 50-200 wt% with respect to binder resin at the point of the refractive index fall effect.

As described above, when the concavo-convex coating film 3 is constituted with fine particles as an essential component for forming the surface concavo-convex together with the binder resin, the fine particles do not impair the light transmittance which is the basic performance as an optical sheet. Fine particles having transparency can be used. Of these, spherical particles having a spherical particle shape are preferred as the fine particles. Note that the term “spherical” refers to particles having a spherical shape or a nearly spherical shape. By making the particle shape spherical, the shape of the tops of the fine protrusions generated on the surface of the concavo-convex coating film 3 by the fine particles and the periphery thereof can be generated in a rounded shape instead of a square shape. In addition, when the fine protrusions do not expose the fine particles and the spherical fine particles are coated with the binder resin, the fine particles are difficult to drop off, and the binder resin itself is in contact with the adjacent member. Become. As a result, the microprotrusions can be made slippery in shape, so that the optical member in contact with the optical sheet, or the optical sheet itself (also the microprotrusions such as the tips of the microprotrusions) are hardly damaged by friction or the like. It is effective for preventing the contact portion from being chipped.
As such spherical fine particles, that is, spherical particles, in addition to resin beads such as acrylic resin beads, polycarbonate resin beads, and polyurethane resin beads, inorganic beads such as glass beads and silica beads can be used.

Since the refractive index of the fine particles is not usually used as a low refractive index material, it is necessary to use a material having a refractive index as close as possible to the refractive index of the binder resin, which diffuses light at the interface between the fine particles and the binder resin. This is preferable in that it is not allowed to occur. However, this is not the case when the light diffusion function is consciously imparted to the optical sheet.
By the way, the fine particles for forming surface irregularities can also be used as the low refractive index agent. However, for that purpose, it is necessary to contain it at the same level as about 50 to 200 wt% with respect to the binder resin in terms of the effect of reducing the refractive index. However, in this case, since the fine particles for forming the surface irregularities are preferably contained in the binder resin usually at a maximum of 5 wt% or less, it becomes difficult to form the surface irregularities as intended by the fine particles. In addition, the light diffusibility becomes too strong than necessary. Accordingly, the fine particles for forming the surface irregularities have a particle diameter of about 1 to 10 μm, which is sufficient to form microprotrusions having a wavelength longer than the visible light wavelength (Rz ≧ 0.78 μm) for preventing optical adhesion, and are refracted as much as possible with the binder resin. On the other hand, the inorganic fine particles and hollow fine particles as the low refractive index agent are about 0.01 to 0.2 μm which is less than the minimum wavelength of visible light in order to avoid unnecessary light diffusion expression. It is preferable to use a particle size and a refractive index satisfying the relationship of Nm = (Ns) ^1/2 as much as possible, and to share the function with each other.

  The particle size of the spherical particles is, for example, about 1 to 10 μm in terms of (primary of individual particles not averaged). In addition, when the particle size distribution is wide, the distribution of the respective protrusion heights of the microprotrusions (the altitudes of the individual microprotrusion portions from the surface of the uneven coating film 3 where the microprotrusions do not exist) becomes wide. Therefore, spherical particles with a large particle size generate microprojections with a high protrusion height and positively act on the formation of voids. However, since the contact frequency with the optical member is high and the external force due to the contact also increases, the coating amount is increased accordingly. The film surface Pm is easily damaged. For this reason, it is preferable that the particle size distribution is narrow. Accordingly, it is more preferable that the particle size distribution is narrow, that is, monodisperse or has a particle size distribution close to monodispersion. For example, as disclosed in the above-mentioned Patent Document 2, it is preferable that the particle size distribution has a half width of 1 μm or less in the particle size distribution curve. Thus, by using monodispersed spherical particles having a half-value width of 1 μm or less as the fine particles, the uniformity of the projection height of the microprojections generated by the microparticles is improved, and the microprojections having a relatively high projection height are obtained. The load concentration degree can be reduced. The half-value width is the particle diameter (value distribution) width at a portion corresponding to a height that is ½ of the peak height of the particle diameter distribution curve. For this reason, the scratch resistance can be improved also from the spherical particle side.

  The particle size distribution and the average particle size may be based on the number, but generally, the volume basis (or weight) is used. In the present invention, the volume-based volume average particle size is also used in the same manner. The price range is the same. Such a volume-based particle size distribution or average particle size can be measured by a dynamic light scattering method using a laser beam. Moreover, the particle diameter of each spherical particle may be measured by microscopic observation and calculated from this.

Further, when the maximum diameter (individual particles) of the spherical particles exceeds 10 μm, the light path changing action increases. For this reason, when the optical sheet 10 is used as a brightness enhancement sheet, the light condensing action that functions on the optical element surface Pe of the optical sheet 10 is reduced, and the optical function thereof starts to be impaired. Therefore, it is preferable to avoid particles exceeding 10 μm as much as possible.
However, it is not intended to exclude a mode of giving a function of appropriately diffusing by adopting a particle having a large particle diameter. On the other hand, when the minimum diameter (individual particles) of the spherical particles is less than 1 μm, a high level of technology is required to disperse the spherical particles in the coating composition that forms the uneven coating film 3, and the uneven surface roughness is reduced. It is not preferable in that it is difficult to secure a projection height (evaluated by a ten-point average roughness Rz) of 0.78 μm or more which is required and the material itself is expensive.
In addition, content of microparticles | fine-particles, such as a spherical particle, shall be 2-15 mass% with respect to binder resin, for example. By adjusting the content of the fine particles, the surface density of the fine protrusions can be adjusted.

  The uneven coating film 3 may be positively imparted with a light diffusion function for diffusing light. For example, the light diffusing function can be imparted by causing the fine particles contained in the uneven coating film 3 to function as a light diffusing agent. In order for the fine particles to function as a light diffusing agent, it is preferable to use a material having a large difference in refractive index between the fine particles and the binder resin. In this case, the difference in refractive index between the fine particles and the binder resin can be 0.1 or more, preferably 0.15 or more.

(Additive)
The uneven coating film 3 may contain various known additives such as a lubricant, a dispersant, a stabilizer, a plasticizer, an ultraviolet absorber, and an antistatic agent. These are used by adding to the resin composition for forming the uneven coating film 3.

For example, the lubricant improves the slipperiness of the outermost surface (surface) that is the rough surface of the uneven coating film 3, makes it difficult for the optical sheet itself to be damaged, and improves the scratch resistance.
Lubricants include hydrocarbon lubricants such as liquid paraffin, paraffin wax, synthetic polyethylene wax, fatty acid lubricants such as lauric acid, higher alcohol lubricants such as stearyl alcohol, stearic acid amide, oleic acid amide, erucic acid amide, etc. Aliphatic amide lubricants, alkylene fatty acid amide lubricants such as methylene bis stearamide, ethylene bis stearamide, metal soap lubricants composed of metal stearates such as zinc stearate, calcium stearate, magnesium stearate, stearic acid Examples thereof include fatty acid ester lubricants such as monoglyceride, stearyl stearate and hydrogenated oil, and silicone lubricants such as silicone oil and modified silicone oil.
In addition to the above, as modified silicone oil, polyether modified silicone oil, amino modified silicone oil, epoxy modified silicone oil, olefin modified silicone oil, fluorine modified silicone oil, alcohol modified silicone oil, higher fatty acid modified silicone oil, etc. Can be mentioned.

  Of the above-mentioned various lubricants, modified silicone oils are preferable, and polyether-modified silicone oils are particularly preferable lubricants. The polyether-modified silicone oil is a compound in which the siloxane skeleton of the silicone oil is modified with the polyether skeleton, and a block in which the polyether skeleton is bonded to one or more of one end, both ends, and side chains of the siloxane skeleton. It is a copolymer. As a preferred compound example of such a polyether-modified silicone oil, for example, polyether-modified dimethylpolysiloxane can be mentioned. The polyether-modified dimethylpolysiloxane is a compound in which the siloxane skeleton is dimethylpolysiloxane and the polyether skeleton is bonded thereto.

[Smooth coating (scratch-resistant coating)]
Further, the optical sheet according to the present invention may have a smooth coating film 4 having a smooth surface in place of the uneven coating film 3 described above, as in the embodiment illustrated in the cross-sectional view of FIG. In this case, the coating film surface Pm becomes a smooth surface by the smooth coating film 4.

The smooth coating film 4 is a transparent layer containing at least a resin and having a smooth surface, and is formed by coating a resin composition. The smooth coating film 4 is formed when the optical sheets 10 are in contact with each other without a protective film, or when the optical sheet 10 is in contact with another optical member whose contact surface is roughened to prevent optical adhesion. It is a layer for preventing scratches.
Such a smooth coating film 4 can be formed by a resin composition obtained by removing the fine particles for forming the unevenness from the resin composition used for forming the uneven coating film. Therefore, the same resin component may be adopted as appropriate, and various additives such as a low refractive index resin, a low refractive index agent, and a lubricant other than the fine particles can be similarly added. Since the setting of the magnitude relationship of the refractive index is the same, further explanation is omitted here.

[Front and back hardness]
In the present invention, the surface He of the optical sheet 10, that is, the hardness He of the optical element surface Pe that is the outermost surface on the unit optical element 2 side, and the back side of the optical sheet 10, that is, the rough surface on the uneven coating film 3 side. The hardness Hm of the coating film surface Pm, which is the outermost surface formed or the outermost surface forming the smooth surface on the smooth coating film 4 side, is the hardness specified by the pencil hardness.

(Pencil hardness)
Here, the pencil hardness related to the hardness He and the hardness Hm means a pencil hardness measured under conditions of a load of 1000 g and a speed of 1 mm / s in accordance with JIS K5600-5-4 (1999 edition). And the hardness Hm of the coating film surface Pm of the uneven coating film 3 or the smooth coating film 4 is F or more in pencil hardness, and the hardness Hm is more than the hardness He by the pencil hardness of the optical element surface Pe on the opposite surface. It is preferable that (Hm ≧ He). As shown in the graph of FIG. 2, the hardness Hm and the hardness He measured for the optical sheet 10 are preferably located in the region Ea.

  The reason why the hardness Hm is equal to or higher than the hardness He is that unless the hardness Hm of the coating film surface Pm is equal to or higher than the hardness He of the optical element surface Pe, the coating film surface Pm is easily damaged. On the other hand, the optical element surface Pe is deformed when an external force is applied and softened so that it returns to the original state when released from the external force, thereby preventing the optical element surface Pe from being damaged. In this regard, the coating film surface Pm, particularly in the case of the uneven coating film 3 having a rough surface, on the contrary, even when an external force is applied, in order to prevent optical adhesion, the coating film surface Pm can endure without corresponding deformation. Need to be maintained. In addition, stress is concentrated on the concavo-convex point-like protrusions in the concavo-convex coating film 3 as compared with the optical element surface Pe, and it is necessary to withstand this. Therefore, it is preferable that the hardness Hm is not less than the hardness He.

Moreover, when the coating film surface Pm is the smooth coating film 4 which has a smooth surface, it is not necessary to consider maintenance of the uneven | corrugated shape which forms the rough surface with respect to external force like the said uneven | corrugated coating film 3. FIG. However, when the coating film surface Pm is a smooth surface of the smooth coating film 4, when the rough surface comes into contact with the coating film surface Pm, for example, an optical member such as a light diffusion sheet or the optical element surface Pe of the optical sheet 10 is coated. When the surface Pm is contacted, a dent is generated on the smooth surface, and if the surface remains unrecovered, it leads to an optical defect. On the other hand, since the surface is smooth, the optical defect is conspicuous, and it is also necessary to withstand deformation against an external force.
In the first place, since the optical element surface Pe originally has irregularities, even if some scratches are attached to the optical element surface Pe, the scratches are relatively inconspicuous, and the scratches are less likely to be a problem. On the other hand, the surface Pm of the smooth coating film 4 is also smooth because the surface is smooth, and it is easy to stand out if any scratches are made.
Therefore, it is preferable that the hardness Hm is equal to or higher than the hardness He even when the smooth coating film 4 is employed.

  By making such hardness and hardness relationship, contact between the front and back surfaces of the optical sheet (between the optical element surface Pe and the coating film surface Pm), or another optical member having a rough surface of the optical sheet and the contact surface Even if contact with the surface occurs, it is possible to effectively prevent scratches such that the optical element surface Pe and the coating film surface Pm of the optical sheet are scraped.

More preferably, the relationship between the hardness He and the hardness Hm is such that the hardness He + 3 ≧ the hardness Hm ≧ the hardness He + 2 when the hardness of one unit on the pencil hardness scale is +1. That is, it is preferable that the hardness Hm of the coating surface Pm is at least +2 units or more on the pencil hardness scale, rather than the hardness He of the optical element surface Pe. However, at most, the hardness Hm of the coating surface Pm may be hardened up to +3 units on the pencil hardness scale with respect to the hardness He of the optical element surface Pe, but it should not be harder than 3 units. Is preferred. In simple terms, it is considered that the harder the pencil hardness is, the harder it is to be scratched. However, when the front and back surfaces of the optical sheet 10 are actually superposed, the optical element surface Pe is scratched. Therefore, it has been found that the above range relation is good.
In addition, the specification of the hardness Hm of the coating film surface and the optical element surface He as described above, particularly the provision of the upper limit He + 3 to the hardness of the coating film surface, is arranged adjacent to the optical sheet 10 by the coating films 3 and 4. It is also effective in eliminating scratches on other optical members.
In addition, the scale of pencil hardness is 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, etc. in order from the softer to the harder. In this pencil hardness scale, for example, “+1 unit” with respect to “HB” means “F”, which is one higher hardness unit, and “+2 unit” means two higher hardness units. Means “H”. Therefore, for example, if He is HB, hardness He + 3 ≧ hardness Hm ≧ hardness He + 2 means 2H ≧ hardness Hm ≧ H.

  By having such hardness and hardness relationship, contact between the front and back surfaces of the optical sheets, or contact between the optical sheet and other members (particularly, in the case of the smooth coating film 4, the contact surface is a rough surface) Can be more reliably prevented from being scraped off the optical element surface Pe and the coating film surface Pm of the optical sheet (see Tables 1, 3 and 4).

(Recovery rate and Martens hardness in Martens hardness test)
For the hardness He of the optical element surface Pe and the hardness Hm of the concavo-convex coating surface Pm of the concavo-convex coating 3, it is preferable to further define a recovery rate by a Martens hardness test. Martens hardness (hardness) is a kind of hardness index, and is measured using, for example, a micro hardness tester (PICODERTOR (registered trademark) HM500, ISO 14577-1) manufactured by Fisher Instruments Co., Ltd. Can do.
Here, the recovery rate and Martens hardness in the Martens hardness test are characteristic values measured using the HM500 micro hardness tester. Specifically, it means a hardness calculated from an indentation depth (μm) at a constant indentation load in a hardness test using the microhardness tester. The indentation load means a load in the normal direction with respect to the optical sheet 10, and the indentation depth represents the depth of the interface when the load is applied (at the time of loading) with the interface of the measurement surface before being pushed as 0. The recovery rate (%) is calculated by the following [Equation 1].

  In addition to the above-mentioned definition of hardness by pencil hardness, if this recovery rate is 50% or more for either one or both of the unit optical element 2 and the uneven coating film 3, the scratch resistance of the optical sheet itself can be improved. (See Table 2). When the recovery rate is high, the degree to which the shape is restored is increased even when an external force is applied, and a part is not lost or permanently deformed and remains indented, so that it is difficult to be damaged.

  In order to make the hardness He and the hardness Hm, the pencil hardness or the recovery rate in the Martens hardness test as described above, the unit optical element 2 and the concavo-convex coating film 3 are made of resin, and This can be realized by using an ionizing radiation curable resin or the like as the resin and adjusting the resin composition. Further, by using the same curable resin such as an ionizing radiation curable resin for the resin of the unit optical element 2 and the concavo-convex coating film 3, it is effective for preventing warpage of the optical sheet due to curing shrinkage or the like.

Further, the Martens hardness is a numerical value obtained by rounding off the first digit with respect to the concavo-convex coating surface Pm as shown in Table 2 in terms of scratch resistance of the optical sheet itself, and is 100 to 180 N / mm. ^{Although a} favorable result was obtained with ² , no favorable result was obtained with 220 N / mm ² . Even if the recovery rate is 50% or more, the highest level of scratch resistance cannot be obtained if the Martens hardness is as high as 220 N / mm ² (Comparative Example A3 in Table 2).
On the other hand, the recovery rate of the optical element surface Pe is also preferable in that 50% or more hardly remains recessed due to an external force, like the concavo-convex coating surface Pm, but the Martens hardness may be softer than the concavo-convex coating layer Pm. Results are obtained (in Table 2 it is about 2-4 N / mm ² ).

[Two sheets stacked]
The optical sheet 10 according to the present invention may be an optical sheet (optical member) 10A in a state where two sheets are overlapped as conceptually shown in the cross-sectional views of FIGS. The state where the two sheets are overlapped means that the upper and lower optical sheets 10a and 10b are not arranged with a space between them but are in contact with each other and arranged adjacent to each other. In the form shown in FIGS. 4 and 5, the two optical sheets are formed such that the optical element surface Pe of the lower optical sheet 10b and the coating surface Pm of the upper optical sheet 10a are in contact with each other. It is piled up.
In the form shown in FIG. 4, each optical sheet 10 a, 10 b has the uneven coating film 3 as a coating film, and the coating film surface Pm of each optical sheet 10 a, 10 b is roughened by the uneven coating film 3. It is formed as. On the other hand, in the form shown in FIG. 5, each of the optical sheets 10 a and 10 b has the smooth coating film 4 as a coating film, and the coating film surface Pm of each of the optical sheets 10 a and 10 b is smooth by the smooth coating film 4. It is formed as. Moreover, although illustration is abbreviate | omitted, either one coating film of two optical sheets may be formed of the uneven | corrugated coating film 3, and the other coating film of two optical sheets may be formed as the smooth coating film 4. .
Moreover, 10 A of optical members comprised from a some optical sheet may be comprised including 3 or more of the optical sheets which were mentioned above.

In the optical member 10A shown in FIGS. 4 and 5, the upper and lower optical sheets 10a and 10b are stacked such that the optical element surface Pe faces the same side, but face different sides. The present invention does not exclude forms that are overlapped in this way. The upper and lower optical sheets 10a and 10b are both unit columnar prisms having a triangular section as the unit optical element 2, and the extending direction of the ridge line is drawn as a direction perpendicular to the paper surface for convenience of drawing. When such columnar unit optical elements are arranged, the extending direction of the ridge line intersects between the optical sheet 10a and the optical sheet 10b, such as orthogonal to each other.
Further, when two optical sheets are stacked, the optical sheets to be stacked are configured in the same manner as the contents of the unit optical element 2 and the uneven coating films 3 and the smooth coating films 4 that form the coating film surface Pm. It may be configured differently.

  When such an optical sheet (optical member) 10A is incorporated into a surface light source device or the like, the coating surface Pm and the optical element surface Pe of the optical sheets 10a and 10b due to mutual contact are unlikely to occur. Scratch resistance is obtained. Further, according to the optical sheet (optical member) 10A in which the refractive indexes Nm and Nm are adjusted, the luminance can be improved.

[Others]
The optical sheet 10 of the present invention may include other layers other than the above-described layers within a range not departing from the gist of the present invention.
For example, an antistatic layer may be further provided on the optical sheet 10. The antistatic layer can reduce the adhesion of foreign matters such as dust, and can prevent the attached foreign matter from being damaged. In addition, an antistatic agent is added to any one or more of the main body 1, the unit optical element 2, and the coatings 3 and 4 (uneven coating 3 or smooth coating 4) without providing an antistatic layer as a separate layer. Thus, an antistatic function may be added.
Moreover, the surface which becomes the light incident surface of the optical sheet 10 may be formed as an antireflection layer having a function of effectively preventing reflection. For example, when the layer forming the light incident surface of the optical sheet 10 has a lower refractive index than the layer adjacent to the layer, the layer can function as an antireflection layer.

In addition, in the optical sheet 10 having the concavo-convex coating film 3 whose coating film surface Pm is rough, 90% or more in the state of the main body 1 and the coating films 3 and 4 where the unit optical element 2 does not exist. The total light transmittance can be exhibited. In the same state, the haze can be reduced to 10% or less. In the same state, the transmission sharpness using the optical combs of 0.125 mm and 0.5 mm can be 50% or more.
The total light transmittance is measured according to JIS K-7361, and the haze is measured according to JIS K-7136. The total light transmittance and haze can be measured using, for example, a haze / transmittance meter HM-15 (manufactured by Murakami Color Research Laboratory Co., Ltd.). The transmission sharpness is measured in accordance with the image sharpness defined in JIS K-7105. The transmission definition can be measured using, for example, a image clarity measuring device (Suga Test Instruments Co., Ltd., ICM-1DP).

<[D] Surface light source device>
The surface light source device according to the present invention is a light source device that includes at least a light source and an optical sheet 10 through which light from the light source passes, and emits light in a planar shape. The configuration and arrangement of various optical members of a conventionally known surface light source device may be appropriately adopted as the configuration and arrangement of the light source and other optical members arranged as necessary, which are components other than the optical sheet 10. it can.

For example, the surface light source device 30 illustrated in FIG. 6 includes a light source 31, a light guide plate 32 including the light source 31 on a side surface, and the optical sheet 10 disposed adjacent to the light output surface of the light guide plate 32. ing. A well-known thing can be suitably employ | adopted for the light source 31, the light-guide plate 32, or the other optical member (not shown) provided as needed. In the surface light source device 30 shown in FIG. 6, the optical sheet 10 is arranged in such a direction that the optical element surface Pe is on the light output surface side in the upper part of the drawing.
On the other hand, the coating film surface Pm of the optical sheet 10 is on the light guide plate 32 side, and the coating film surface Pm is in contact with the light exit surface of the light guide plate 32 that is another optical member that contacts the optical sheet 10. However, in the form of the figure, the coating film surface Pm of the optical sheet 10 is formed as a rough surface by the uneven coating film 3. Therefore, the uneven coating 3 prevents optical contact with the light guide plate 32, and can effectively prevent uneven luminance in the surface, interference fringes, and the like due to the optical contact. Furthermore, since the scratch resistance of the coating surface Pm is improved, it is possible to effectively prevent the optical sheet itself from being damaged and from being damaged by contact with the light exit surface of the light guide plate 32 in the illustrated surface light source device. can do.

  6, the optical sheet 10 incorporated in the surface light source device 30 has the uneven coating film 3 as a coating film. However, as shown in FIG. 7, the optical sheet incorporated in the surface light source device 30. 10 may have a smooth coating film 4 instead of the uneven coating film 3. In the surface light source device shown in FIG. 7, the surface of the other optical member in contact with the smooth coating film 4 is a rough surface to prevent optical adhesion. The optical member in contact with the smooth coating film 4 may be the light guide plate 32, but in the illustrated example, a member in which the surface facing the optical sheet is formed as a rough surface between the light guide plate 32 and the optical sheet 10. For example, a light diffusion sheet 35 is disposed. Also in the surface light source device 30 shown in FIG. 7, the smooth coating surface Pm of the optical sheet 10 and the rough surface of the member disposed adjacent to the optical sheet (for example, the rough surface forming the light exit surface of the light diffusion sheet 35). ) Can be effectively avoided from scratches on the smooth coating film surface Pm of the optical sheet 10 and problems due to optical adhesion.

6 and 7 show an example in which only one optical sheet 10 is incorporated in the surface light source device, but a plurality of, for example, two optical sheets shown in FIGS. 4 and 5 are used. The sheet may be incorporated in the surface light source device.
Moreover, although the surface light source device shown in FIGS. 6 and 7 is configured as an edge light type, the surface light source device into which the optical sheet is incorporated may be configured as a direct type. Further, as the light source 31, in addition to a fluorescent lamp such as a linear cold cathode tube, a spot LED (light emitting diode) or a planar EL (electroluminescent element) is used. For example, a transparent acrylic resin or the like is used for the light guide plate 32, and a light diffusing portion is provided on the surface facing the light output surface by printing or the like.
The light source 31 is usually provided with a reflecting member such as a reflecting plate in order to direct light from the light source 31 toward the light guide plate 32 or the optical sheet 10. The reflecting member is made of a highly reflective material such as metal. In addition, optical members such as a light diffusing plate, a polarization separation film, and a retardation plate are further arranged as necessary.

<[E] Liquid crystal display device>
A liquid crystal display device according to the present invention is a display device including at least a surface light source device according to the present invention used as a backlight and a transmissive displayable liquid crystal panel disposed on a light exit surface of the surface light source device. An optical sheet 10 according to the present invention is provided in the surface light source device. In this display device, conventionally known constituent members of a liquid crystal display device can be appropriately adopted as the liquid crystal panel, other members not shown, for example, an optical member such as an antiglare film, a panel drive circuit, and the like.
For example, in the liquid crystal display device 40 shown in FIGS. 6 and 7, the surface light source device 30 described above is used as a backlight, and a transmissive liquid crystal panel 41 is disposed adjacently on the light exit surface. Accordingly, the light exit surface of the surface light source device 30 is the optical element surface Pe of the optical sheet 10 as shown in the figure, so that the optical element surface Pe serves as another optical member in contact with the optical sheet 10. It is in contact with the back surface of the liquid crystal panel 41. Note that a polarizing plate is usually laminated on the back surface of the liquid crystal panel 41 in contact. Then, the image on the liquid crystal panel 41 is observed by the observer V above the drawing by the light from the surface light source device 30.
As a liquid crystal display device having such a configuration, even when the optical sheet 10 and the liquid crystal panel are disposed adjacent to each other, the scratch resistance of the optical element surface Pe is improved, and thus the optical sheet itself can be prevented from being damaged. It has become. Moreover, since the surface light source device 30 including the optical sheet 10 is used, the luminance can be improved.

  In the liquid crystal display device 40 illustrated in FIGS. 6 and 7, the surface light source device 30 included in the liquid crystal display device 40 is configured as an edge light type, but may be configured as a direct type as described above.

<[F] effect>
(1) In the optical sheet described above, the pencil hardness on the front and back surfaces of the optical sheet and the relationship between the two are in spite of the fact that the outermost surface has a rough concavo-convex coating or the outermost smooth coating. By specifying, the scratch resistance of the front and back surfaces of the optical sheet itself when used adjacent to the optical member including itself when two sheets are overlapped is improved, and scratches are effectively prevented. be able to.
In particular, even if the optical sheet is subjected to vibration during storage, transportation or the like in a roll state, the front and back surfaces are prevented from being scratched, and the quality is not deteriorated due to poor appearance or the like. As a result, it is possible to eliminate the need for a protective film that is usually temporarily attached to both the front and back surfaces of the optical sheet until use, so that resource saving and cost reduction can be achieved.
Furthermore, by defining the refractive index relationship between the coating film and the main body, while providing a coating film for improving the scratch resistance, the brightness does not decrease correspondingly, and the number of layers is provided by providing the coating film. Even if the brightness increases, the luminance does not decrease. That is, the luminance can be improved while ensuring the scratch resistance.
(2) Further, in the surface light source device and the liquid crystal display device described above, since the scratch resistance of the front and back surfaces of the optical sheet is improved as described above, the device is subjected to vibration during storage and transportation. In addition, it is possible to effectively prevent scratches on the front and back surfaces of the incorporated optical sheet.

  Hereinafter, the present invention will be further described with reference to examples and comparative examples.

<Survey 1>
First, as investigation 1, an investigation was performed on an optical sheet having the configuration of FIG. That is, the optical sheet targeted in Investigation 1 had a coating film composed of a concavo-convex coating film, and the coating film surface was formed as a rough surface.

[Preparation of paint for forming uneven film]
In order to form uneven coating films having various pencil hardnesses, paints having the following respective compositions were prepared.

(Composition A1: for pencil hardness HB)
Fluorine atom-containing urethane acrylate ultraviolet curable resin 99 parts by mass Fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle diameter of 5 μm) 1 part by mass (MX-500H, manufactured by Soken Chemical Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition A2: for pencil hardness F)
Fluorine atom-containing urethane acrylate UV curable resin 49.5 parts by mass Pentaerythritol triacrylate 49.5 parts by mass Fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle diameter of 5 μm) 1 part by mass (Soken Chemical Co., Ltd.) (Made by company, MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition A3: for pencil hardness H)
99 parts by weight of pentaerythritol triacrylate Fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle diameter of 5 μm) 1 part by weight (Made by Soken Chemical Co., Ltd., MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition A4: for pencil hardness 2H)
Pentaerythritol triacrylate 49.5 parts by mass Dipentaerythritol hexaacrylate 49.5 parts by mass Fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle diameter of 5 μm) 1 part by mass (manufactured by Soken Chemical Co., Ltd., MX- 500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition A5: for pencil hardness 3H)
99 parts by mass of dipentaerythritol hexaacrylate 1 part by mass of fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle size of 5 μm) (MX-500H, manufactured by Soken Chemical Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

[Example A1]
The optical sheet 10 shown in FIG. 1 in which a unit columnar prism was adopted as the unit optical element 2 was produced.
First, a metallic cylinder-shaped mold having an uneven surface opposite to the prism group composed of unit columnar prisms was prepared as a mold. Then, a transparent acrylic ultraviolet curable resin liquid having a resin composition for forming unit optical elements described below was applied to the mold, and a transparent biaxially stretched polyethylene terephthalate film (PET film) having a thickness of 188 μm was further formed thereon. The resin liquid was cured by ultraviolet irradiation from a high pressure mercury lamp. Then, a prism sheet member having a prism group in which unit columnar prisms as unit optical elements 2 are arranged on one surface 1p of the sheet-like main body portion 1 in parallel with each other in the ridgeline was manufactured.

[Resin composition for unit optical element formation]
Prepolymer (caprolactone-modified urethane acrylate) 11 parts by weight Prepolymer (tolylene diisocyanate urethane acrylate) 8 parts by weight Bifunctional monomer (bisphenol A diacrylate) 47 parts by weight Trifunctional monomer (glycerin epoxy triacrylate) 30 parts by weight Initiator 2.5 parts by mass (2,4,6-trimethylbenzoyldiphenylphosphine oxide)
Lubricant (phosphate ester lubricant) 1 part by mass

  The main body 1 is composed of the PET film and a part of the cured product layer corresponding to the thickness of the cured product layer of the ultraviolet curable resin liquid between the PET film and the convex portion on the mold surface. The Further, the remaining thickness portion of the cured product layer constitutes a prism group having a number of unit columnar prisms as unit optical elements 2. The unit columnar prism has a main cut surface shape of a right isosceles triangle having an apex angle of 90 °, a base of 50 μm, a constant height of 25 μm, and an arrangement period of 50 μm. The unit optical element 2 composed of the unit columnar prism completely covers one surface 1p of the main body 1 to form a prism structure in which unit optical elements are arranged in the same shape, the same size and the same period. The outer surface is the optical element surface Pe.

Next, the other surface 1q of the main body 1 which is the back surface side of the prism sheet member is coated with the coating composition for forming an uneven coating film of the composition A2, dried by heating, and then cured by irradiation with ultraviolet rays from a high pressure mercury lamp. A 3 μm-thick uneven coating film 3 was formed to produce a target optical sheet.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the uneven coating surface Pm was F.

[Example A2]
An optical sheet of Example A2 was produced in the same manner as in Example A1, except that the coating film for forming an uneven coating film in Example A1 was changed to Composition A3.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the uneven coating surface Pm was H.

[Example A3]
An optical sheet of Example A3 was produced in the same manner as in Example A1, except that the coating film for forming an uneven coating film in Example A1 was changed to Composition A4.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the uneven coating film surface Pm was 2H.

[Example A4]
An optical sheet of Example A4 was produced in the same manner as in Example A1, except that the coating film for forming an uneven coating film in Example A1 was changed to Composition A5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the uneven coating film surface Pm was 3H.

[Example A5]
The optical coating of Example A5 is the same as Example A2 except that the coating composition for forming an uneven coating film in Example A2 remains as composition A3 and the resin composition for forming unit optical elements is changed to the following composition. A sheet was produced.
The resin composition for forming an optical element uses caprolactone-modified urethane acrylate and ethylene oxide-modified biphenyloxyethyl acrylate as prepolymers, and further uses neopentyl glycol methacrylate and bisphenol A diacrylate as bifunctional monomers. A glycerin epoxy triacrylate is used as a functional monomer, and a bisacylphosphine oxide-based initiator and 1-hydroxycyclohexyl phenyl ketone (Irgacure (registered trademark) 184) are added as initiators, and a phosphate ester-based lubricant is added. It is the added resin composition.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was H.

[Example A6]
An optical sheet of Example A6 was produced in the same manner as in Example A5, except that the coating film for forming an uneven coating film in Example A5 was changed to Composition A4.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was 2H.

[Example A7]
An optical sheet of Example A7 was produced in the same manner as in Example A5, except that the coating film for forming an uneven coating film in Example A5 was changed to Composition A5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was 3H.

[Example A8]
An optical sheet of Example A8 was produced in the same manner as in Example A5 except that the coating film for forming an uneven coating film in Example A5 was changed to Composition A2.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was F.

[Example A9]
In Example A5, the concavo-convex coating film-forming coating material remains as composition A3, and as the resin composition for forming the unit optical element, the above-described concavo-convex coating film-forming coating material composition A3 is used. Otherwise, an optical sheet of Example A9 was produced in the same manner as Example A5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the uneven coating surface Pm was H.

[Comparative Example A1]
An optical sheet of Comparative Example A1 was produced in the same manner as in Example A1, except that the coating film for forming an uneven coating film in Example A1 was changed to Composition A1.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the uneven coating surface Pm was HB.

[Comparative Example A2]
An optical sheet of Comparative Example A2 was produced in the same manner as in Example A5, except that the uneven coating film-forming coating material in Example A5 was changed to Composition A1.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was HB.

[Comparative Example A3]
An optical sheet of Comparative Example A3 was produced in the same manner as in Example A9, except that the coating film for forming an uneven coating film in Example A9 was changed to Composition A2.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the uneven coating surface Pm was F.

[Comparative Example A4]
In Example A5, the concavo-convex coating film-forming coating material remains as composition A3, and the above-described concavo-convex coating film-forming coating material composition A4 is used as the resin composition for unit optical element formation. Otherwise, an optical sheet of Comparative Example A4 was produced in the same manner as Example A5.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was 2H, and the hardness Hm of the uneven coating surface Pm was H.

[Performance evaluation]
About the optical sheet of said Example A1-A9 and Comparative Example A1-A4, pencil hardness and scratch resistance were evaluated. Moreover, the Martens hardness and recovery rate of each Example were measured. The pencil hardness test on the optical element surface Pe was performed by moving the pencil in the prism ridge direction.

(1) The pencil hardness was measured under the conditions of a load of 1000 g and a speed of 1 mm / s in accordance with JIS K5600-5-4 (1999).
(2) The scratch resistance was evaluated as follows. First, ten optical sheets cut into a square having a side length of 5 cm were stacked on a transparent acrylic resin plate. Ten optical sheets were overlapped with each optical element surface facing downward and with the unit optical elements, that is, unit columnar prisms arranged in parallel to each other. The same transparent acrylic resin plate as described above was further stacked on the 10 optical sheets stacked, and the periphery of each side was fixed with an adhesive tape. A pair of acrylic resin plates with 10 optical sheets sandwiched between them are fixed on a horizontal shaking table of a vibration tester (manufactured by IDEX Co., Ltd., BF-50UL). In this state, three axes of vertical and horizontal vibrations were applied simultaneously. The vibration was an acceleration of 7.3 G and a frequency of 67 Hz.
About the optical sheet after applying vibration, the surface condition was confirmed by visual observation with a microscope having a magnification of 500 times. For the optical element surface Pe, an area over the length of 3 mm of the ridge line portion of the unit columnar prism was observed, and for the coating film surface Pm, a square area with an area of 9 mm ² was observed to confirm the presence or absence of scratches.
In order to evaluate the scratch resistance of the coating film surface (the uneven coating film surface in Investigation 1), the presence or absence of scratches on each of the five optical sheets after the test was confirmed in each of the Examples and Comparative Examples. If no scratches were generated on the coating surfaces of all five optical sheets, the scratch resistance of the coating surfaces was evaluated as “excellent”, and the coating surfaces of all five optical sheets were scratched. If it occurred, the scratch resistance of the coating film surface was evaluated as “bad”, and scratches were generated on the optical element surface of some optical sheets, but the coating surface of the remaining optical sheets were scratched. When it did not occur, the scratch resistance of the coating surface was evaluated as “good”.
In order to evaluate the scratch resistance of the optical element surface, in each of the Examples and Comparative Examples, the presence or absence of scratches was confirmed on five optical sheets after the test. If no scratch has occurred on the optical element surfaces of all five optical sheets, the scratch resistance of the optical element surfaces is evaluated as “excellent”, and the optical element surfaces of all five optical sheets are scratched. If it occurs, the scratch resistance of the optical element surface is evaluated as “bad”, and scratches have occurred on the optical element surfaces of some optical sheets, but scratches have occurred on the optical element surfaces of the remaining optical sheets. If not, the scratch resistance of the optical element surface was evaluated as “good”.
(3) Martens hardness and recovery rate were measured using a microhardness tester (PICODERTOR (registered trademark) HM500, ISO145777-1) manufactured by Fisher Instruments Co., Ltd.

[Performance comparison]
And Table 1 and FIG. 2 show hardness He and hardness Hm in pencil hardness of Examples A1 to A9 and Comparative Examples A1 to A4 and scratch resistance. In FIG. 2 and Table 1, as a comprehensive evaluation, a case where the evaluation of the scratch resistance of the coating film surface Pm and the optical element surface Pe was “excellent” is indicated by a circle, and the evaluation of the scratch resistance of the coating film surface Pm Is “excellent” and the evaluation of the scratch resistance of the optical element surface Pe is “good” is indicated by Δ, and the evaluation of the scratch resistance of the coating surface Pm is “good” or “bad”. Alternatively, a case where the evaluation of the scratch resistance of the optical element surface Pe is “defective” is indicated by a cross. Further, alphabets A to H alongside the circle mark, the triangle mark, and the cross mark are symbols corresponding to “positions on the graph” in Table 1. For example, the coordinates (B, HB) of He = B and Hm = HB of the point A correspond to the comparative example A1.

  As shown in Table 1 and FIG. 2, in Comparative Example A3 and Comparative Example A4 in which the hardness Hm of the coating film surface Pm is lower than the hardness He of the optical element surface Pe, the scratch resistance of the coating film surface Pm is “bad”. " In Comparative Examples A1 and A2 in which the hardness Hm of the coating film surface Pm is lower than “F” even though the hardness Hm of the coating film surface Pm is equal to or higher than the hardness He of the optical element surface Pe, The scratch resistance of the surface Pm did not become “excellent”. In each example where the hardness Hm is equal to or higher than the hardness He (hardness Hm ≧ hardness He) and the hardness Hm is equal to or higher than “F” (hardness Hm ≧ F), the scratch resistance of the coating surface Pm becomes “excellent” and The scratch resistance of the optical element surface Pe was “good” or higher, and the overall evaluation focusing on the scratch resistance on the coating film surface Pm was “good” or “good”.

  However, in Example A3, Example A4, and Example A7 in which “Hardness Hm−Hardness He> 3”, scratches that are considered to have no problem in practice are optically damaged on one or two optical sheets. It occurred on the element surface Pe. Also in Example A8 and Example A9 in which “Hardness Hm−Hardness He” is “1” or “0”, there is one or two optical scratches to the extent that there is no practical problem. It occurred on the optical element surface Pe of the sheet. On the other hand, in Example A1, Example A2, Example A5, and Example A6 satisfying the hardness He + 3 ≧ hardness Hm ≧ hardness He + 2, both the scratch resistance of the optical element surface Pe and the coating surface Pm is “excellent”. Evaluation became "(circle)".

Next, in Table 2, the recovery rate in the Martens hardness test is shown together with the pencil hardness for several examples of the above examples and comparative examples. As shown in Table 2, it can be seen that the scratch resistance is good when the recovery rate is 50% or more, and that the scratch resistance is poor when it is 41.6% (Comparative Example A1) and less than 50%.
Further, it can be seen that the Martens hardness is too large or too small for the uneven coating film surface Pm to deteriorate the scratch resistance and is good in the range of 100 to 180 N / mm ² . On the other hand, regarding the optical element surface Pe, the Martens hardness is 2 to 4 N / mm ² which is about two orders of magnitude smaller than the concavo-convex coating surface Pm, but it can be seen that the scratch resistance is still good. It is considered that the optical element surface Pe is acting in a good direction to be deformed without resisting to external force much like a willow and to return to its original shape when released from the external force.

<Survey 2>
As Survey 2, an optical sheet having the configuration of FIG. 1 was surveyed. That is, the optical sheet used in Investigation 2 had a coating film composed of a concavo-convex coating film, and the coating film surface was formed as a rough surface.

[Preparation of paint for forming uneven film]
In order to form uneven coating films having various pencil hardnesses, paints having the following respective compositions were prepared.

(Composition B1: for pencil hardness HB)
99 parts by mass of UV curable fluorine atom-containing polymer (refractive index 1.41) (Opstar (registered trademark) JN35, manufactured by JSR Corporation, solid content 15 wt%, solvent methyl isobutyl ketone)
1 part by weight of fine particles (monodispersed spherical cross-linked acrylic resin beads having an average particle diameter of 5 μm) (manufactured by Soken Chemical Co., Ltd., MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition B2: for pencil hardness F)
80 parts by mass of UV curable fluorine atom-containing polymer (refractive index 1.41) (Opstar (registered trademark) JN35, manufactured by JSR Corporation, solid content 15 wt%, solvent methyl isobutyl ketone)
Pentaerythritol triacrylate (refractive index 1.51) 19 parts by mass Fine particles (monodispersed spherical crosslinked acrylic resin beads having an average particle diameter of 5 μm) 1 part by mass (MX-500H, manufactured by Soken Chemical Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition B3: for pencil hardness H)
Pentaerythritol triacrylate (refractive index 1.51) 80 parts by mass UV curable urethane acrylate oligomer (refractive index 1.52) 19 parts by mass (Shikou (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
1 part by weight of fine particles (monodispersed spherical cross-linked acrylic resin beads having an average particle diameter of 5 μm) (manufactured by Soken Chemical Co., Ltd., MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition B4: for pencil hardness 2H)
29 parts by mass of dipentaerythritol hexaacrylate (refractive index 1.51) (KAYARAD (registered trademark) DPHA, manufactured by Nippon Kayaku Co., Ltd.)
70 parts by mass of UV-curable curable urethane acrylate oligomer (refractive index 1.52) (purple light (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
1 part by weight of fine particles (monodispersed spherical cross-linked acrylic resin beads having an average particle diameter of 5 μm) (manufactured by Soken Chemical Co., Ltd., MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition B5: for pencil hardness 3H)
80 parts by mass of dipentaerythritol hexaacrylate (refractive index 1.51) (KAYARAD (registered trademark) DPHA, manufactured by Nippon Kayaku Co., Ltd.)
UV-curable curable urethane acrylate oligomer (refractive index 1.52) 19 parts by mass (purple light (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
1 part by weight of fine particles (monodispersed spherical cross-linked acrylic resin beads having an average particle diameter of 5 μm) (manufactured by Soken Chemical Co., Ltd., MX-500H)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

[Example B1]
The optical sheet 10 shown in FIG. 1 in which a unit columnar prism was adopted as the unit optical element 2 was produced. The shape of the unit columnar prism was the same as in Example A1. In Example B1, an optical sheet was produced in the same manner as in Example A1, except that the coating for forming an uneven coating film was changed to composition B2. Therefore, in Example B1, the unit optical element-forming resin composition was obtained by using a unit optical element-forming resin composition similar to Example A1 and a unit columnar prism having the same shape as Example A1. Produced. The resin composition for forming the unit optical element was a transparent biaxially stretched polyethylene terephthalate film (PET film) having a thickness of 188 μm, as in Example A1, and the refractive index of this PET film was 1.65. .

  Rz (JIS B0601 (1994 version) regulation) of the outermost surface of the coating film surface Pm was 3.26 μm. Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating surface Pm was F. Moreover, the refractive index Ns of the part which faces the coating film of the main-body part 1 was 1.65, and the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.47.

[Example B2]
An optical sheet of Example B2 was produced in the same manner as in Example B1, except that the coating film for forming an uneven coating film in Example B1 was changed to Composition B3.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was H. Further, the refractive index Nm of the resin forming the uneven coating film 3 was 1.51 with respect to the refractive index Ns1.65 of the portion facing the coating film of the main body 1.

[Example B3]
An optical sheet of Example B3 was produced in the same manner as in Example B1, except that the coating material for forming an uneven coating film in Example B1 was changed to Composition B4.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was 2H. Further, the refractive index Nm of the resin forming the uneven coating film 3 was 1.52.

[Example B4]
An optical sheet of Example B4 was produced in the same manner as in Example B1, except that the coating for forming an uneven coating film in Example B1 was changed to Composition B5.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was 3H. Moreover, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.51.

[Example B5]
The optical coating of Example B5 is the same as Example B2 except that the coating composition for forming an uneven coating film in Example B2 is still the composition B3 and the resin composition for forming the unit optical element is changed to the following composition. A sheet was produced.
The resin composition for forming an optical element uses caprolactone-modified urethane acrylate and ethylene oxide-modified biphenyloxyethyl acrylate as prepolymers, and further uses neopentyl glycol methacrylate and bisphenol A diacrylate as bifunctional monomers. A glycerin epoxy triacrylate is used as a functional monomer, and a bisacylphosphine oxide-based initiator and 1-hydroxycyclohexyl phenyl ketone (Irgacure (registered trademark) 184) are added as initiators, and a phosphate ester-based lubricant is added. It is the added resin composition. Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating surface Pm was H. In addition, with respect to the refractive index Ns1.65 of the part which faces the coating film of the main-body part 1, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.51.

[Example B6]
An optical sheet of Example B6 was produced in the same manner as in Example B5, except that the coating film for forming an uneven coating film in Example B5 was changed to Composition B4.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating film surface Pm was 2H. The refractive index Nm of the resin forming the uneven coating film 3 was 1.52.

[Example B7]
An optical sheet of Example B7 was produced in the same manner as in Example B3 except that the coating film for forming an uneven coating film in Example B5 was changed to Composition B5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating film surface Pm was 3H. The refractive index Nm of the resin forming the uneven coating film 3 was 1.51.

[Example B8]
An optical sheet of Example B8 was produced in the same manner as in Example B5 except that the coating material for forming an uneven coating film in Example B5 was changed to Composition B2.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was F. The refractive index Nm of the resin forming the uneven coating film 3 was 1.47.

[Example B9]
In Example B5, the concavo-convex coating film-forming coating material remains as composition B3, and the above-described concavo-convex coating film-forming coating material composition B3 is used as the resin composition for unit optical element formation. Otherwise, an optical sheet of Example B9 was produced in the same manner as Example B5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the uneven coating surface Pm was H. The refractive index Nm of the resin forming the uneven coating film 3 was 1.51.

[Comparative Example B1]
An optical sheet of Comparative Example B1 was produced in the same manner as in Example B1, except that the coating film for forming an uneven coating film in Example B1 was changed to Composition B1.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was HB. Moreover, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.41.

[Comparative Example B2]
An optical sheet of Comparative Example B2 was prepared in the same manner as in Example B5, except that the uneven coating film-forming coating material in Example B5 was changed to Composition B1.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the uneven coating surface Pm was HB. Moreover, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.41.

[Comparative Example B3]
An optical sheet of Comparative Example B3 was produced in the same manner as in Example B9, except that the coating film for forming an uneven coating film in Example B9 was changed to Composition B2.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the uneven coating surface Pm was F. Moreover, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.47.

[Comparative Example B4]
In Example B5, the concavo-convex coating film-forming coating material remains as composition B3, and the above-described concavo-convex coating film-forming coating material composition B4 is used as the resin composition for unit optical element formation. Otherwise, an optical sheet of Comparative Example B4 was produced in the same manner as Example B5.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was 2H, and the hardness Hm of the uneven coating surface Pm was H. Moreover, the refractive index Nm of resin which comprises the uneven | corrugated coating film 3 was 1.51.

[Comparative Example D1]
An optical sheet was produced in the same manner as in Example B1, except that the formation of the uneven coating film 3 in Example B1 was omitted. This optical sheet is composed of a main body 1 and unit optical elements 2, and the back side surface opposite to the optical element surface of the optical sheet is the other surface of the main body 1 (unit optical elements 2 are not formed). Side surface).

[Comparative Example D2]
An optical sheet was produced in the same manner as in Example B5 except that the formation of the uneven coating film 3 in Example B5 was omitted. This optical sheet is composed of a main body 1 and unit optical elements 2, and the back side surface opposite to the optical element surface of the optical sheet is the other surface of the main body 1 (unit optical elements 2 are not formed). Side surface).

[Performance evaluation]
About the optical sheet of said Example B1-B9 and Comparative Example B1-B4, pencil hardness and abrasion resistance were evaluated. Moreover, the brightness | luminance was evaluated about the optical sheet of Example B1-B7 and Comparative Example B1, B2, D1, D2. The pencil hardness test on the optical element surface Pe was performed by moving the pencil in the prism ridge direction.

(1) The pencil hardness was evaluated in the same manner as in Examples A1 to A9 and Comparative Examples A1 to A4 described above.
(2) The scratch resistance was evaluated in the same manner as in Examples A1 to A9 and Comparative Examples A1 to A4 described above.
(3) Brightness is obtained by removing the liquid crystal display plate and various optical members from the screen side of a liquid crystal television receiver (product number: UN40B6000VF) manufactured by Samsung Electronics Co., Ltd., and an edge light type surface light source device (the outermost surface is a light guide plate). The optical sheets of Examples B1 to B7 and Comparative Examples B1, B2, D1, and D2 are placed on the light exit surface (on the light guide plate) of the surface light source device, with the coating film surface Pm side facing the light guide plate side. Then, the luminance in the normal direction of the light guide plate was measured and evaluated. The luminance was measured using a luminance meter (Topcon Co., Ltd., BM-7). The evaluation method is as follows: Comparative Example B1 and Examples B1 to B4 are evaluated as a percentage when the unit optical element 2 is not provided with a coating film and the luminance of Comparative Example D1 of the same resin is 100%. B2 and Examples B5 to B8 were evaluated in terms of percentage when the coating film was not provided and the unit optical element 2 had the same luminance as Comparative Example D2 of the same resin as 100%.

[Performance comparison]
And Table 3 shows hardness He and hardness Hm in pencil hardness of Examples B1 to B9 and Comparative Examples B1 to B4, D1 and D2, scratch resistance, coating film refractive index, and luminance in the front direction. .

  Regarding Examples B1 to B9 and Comparative Examples B1 to B4, the relationship between the hardness Hm of the coating surface Pm and the hardness Pe of the optical element surface He and the scratch resistance is the same as that of Examples A1 to A9 shown in FIG. Similar to Examples A1-A4.

  Specifically, as shown in Table 3 and FIG. 2, in Comparative Examples B3 and B4 in which the hardness Hm of the coating surface Pm is lower than the hardness He of the optical element surface Pe, the resistance of the coating surface Pm Abrasion became "bad". In Comparative Examples B1 and B2 in which the hardness Hm of the coating film surface Pm is lower than “F” even if the hardness Hm of the coating film surface Pm is equal to or higher than the hardness He of the optical element surface Pe, The scratch resistance of the surface Pm did not become “excellent”. In Examples B1 to B9 where the hardness Hm is equal to or higher than the hardness He (hardness Hm ≧ hardness He) and the hardness Hm is equal to or higher than “F” (hardness Hm ≧ F), the scratch resistance of the coating surface Pm is “excellent”. As a result, the scratch resistance of the optical element surface Pe was “good” or higher, and the overall evaluation focusing on the scratch resistance on the coating film surface Pm was “good” or “good”.

  However, in Example B3, Example B4, and Example B7 in which “Hardness Hm−Hardness He> 3”, scratches that are considered to have no problem in practical use are caused by the optical properties of one or two optical sheets. It occurred on the element surface Pe. Also in Example B8 and Example B9 in which “Hardness Hm−Hardness He” is “1” or “0”, there is one or two optical scratches to the extent that there is no practical problem. It occurred on the optical element surface Pe of the sheet. On the other hand, in Example B1, Example B2, Example B5, and Example B6 satisfying the hardness He + 3 ≧ hardness Hm ≧ hardness He + 2, both the scratch resistance of the optical element surface Pe and the coating film surface Pm becomes “excellent”. Evaluation became "(circle)".

(Evaluation of brightness)
As shown in Table 3, Examples B1 to B8 and Comparative Examples in which a coating film made of a resin having a refractive index lower than the refractive index 1.65 of the portion (PET film) facing the coating film 3 of the main body 1 was formed. Both B1 and B2 exceeded 100%, and the brightness was higher than that of Comparative Examples D1 and D2 (100%) where such a coating film was not formed on the light incident surface.

<Survey 3>
As Survey 3, an optical sheet having the configuration of FIG. 3 was surveyed. That is, the optical sheet used in Investigation 3 had a coating film made of a smooth coating film (a scratch-resistant coating film), and the coating film surface was formed as a smooth surface.

[Preparation of paint for forming smooth coating film]
In order to form smooth coating films having various pencil hardnesses, paints having the following respective compositions were prepared.

(Composition C1: for pencil hardness HB)
UV-curable fluorine atom-containing polymer (refractive index 1.41) 100 parts by mass (Opstar (registered trademark) JN35, manufactured by JSR Corporation, solid content 15 wt%, solvent methyl isobutyl ketone)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition C2: for pencil hardness F)
UV-curable fluorine atom-containing polymer (refractive index 1.41) 80 parts by mass (Opstar (registered trademark) JN35, manufactured by JSR Corporation, solid content 15%, solvent methyl isobutyl ketone)
Pentaerythritol triacrylate (refractive index 1.51) 20 parts by mass Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition C3: for pencil hardness H)
80 parts by mass of pentaerythritol triacrylate (refractive index 1.51) 20 parts by mass of UV-curable curable urethane acrylate oligomer (refractive index 1.52) (purple light (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition C4: for pencil hardness 2H)
30 parts by mass of dipentaerythritol hexaacrylate (refractive index 1.51) (KAYARAD (registered trademark) DPHA, manufactured by Nippon Kayaku Co., Ltd.)
70 parts by mass of UV-curable curable urethane acrylate oligomer (refractive index 1.52) (purple light (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

(Composition C5: for pencil hardness 3H)
80 parts by mass of dipentaerythritol hexaacrylate (refractive index 1.51) (KAYARAD (registered trademark) DPHA, manufactured by Nippon Kayaku Co., Ltd.)
UV-curable curable urethane acrylate oligomer (refractive index 1.52) 20 parts by mass (purple light (registered trademark) UV1700B, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Photoinitiator (1-hydroxycyclohexyl phenyl ketone) 1 part by mass
(Irgacure (registered trademark) 184)
Solvent (Methyl isobutyl ketone: cyclohexanone = 1: 1 mass ratio) Appropriate amount

[Example C1]
The optical sheet of Example C1 in the same manner as in Example B1, except that the smooth coating film 4 was formed by changing the coating material for forming the uneven coating film in Example B1 to the smooth coating film forming composition C2. Was made.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating surface Pm was F. Further, the refractive index Nm of the resin forming the smooth smooth coating film 4 was 1.47 with respect to the refractive index Ns1.65 of the portion facing the coating film of the main body 1.
The outermost surface Rz (JIS B0601 (1994 version) regulation) of the coating film surface Pm was 0.16 μm.

[Example C2]
An optical sheet of Example C2 was produced in the same manner as in Example C1, except that the coating material for forming a smooth coating film in Example C1 was changed to composition C3.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was H. Further, the refractive index Nm of the resin forming the smooth smooth coating film 4 was 1.51 with respect to the refractive index Ns1.65 of the portion facing the coating film of the main body 1.

[Example C3]
An optical sheet of Example C3 was produced in the same manner as in Example C1, except that the coating material for forming a smooth coating film in Example C1 was changed to composition C4.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was 2H. Further, the refractive index Nm of the resin forming the smooth coating film 4 was 1.52.

[Example C4]
An optical sheet of Example C4 was produced in the same manner as in Example C1, except that the coating material for forming a smooth coating film in Example C1 was changed to composition C5.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was 3H. Further, the refractive index Nm of the resin forming the smooth coating film 4 was 1.51.

[Example C5]
The optical coating of Example C5 was the same as Example C2 except that the coating composition for forming a smooth coating film in Example C2 was kept as composition C3 and the resin composition for forming the unit optical element was changed to the following composition. A sheet was produced.
The resin composition for forming an optical element uses caprolactone-modified urethane acrylate and ethylene oxide-modified biphenyloxyethyl acrylate as prepolymers, and further uses neopentyl glycol methacrylate and bisphenol A diacrylate as bifunctional monomers. A glycerin epoxy triacrylate is used as a functional monomer, and a bisacylphosphine oxide-based initiator and 1-hydroxycyclohexyl phenyl ketone (Irgacure (registered trademark) 184) are added as initiators, and a phosphate ester-based lubricant is added. It is the added resin composition. Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating surface Pm was H. In addition, with respect to the refractive index Ns1.65 of the part which faces the coating film of the main-body part 1, the refractive index Nm of resin which comprises the smooth coating film 3 was 1.51.

[Example C6]
An optical sheet of Example C6 was produced in the same manner as in Example C5, except that the coating material for forming a smooth coating film in Example C5 was changed to composition C4.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating film surface Pm was 2H. Further, the refractive index Nm of the resin forming the smooth coating film 4 was 1.52.

[Example C7]
An optical sheet of Example C7 was produced in the same manner as in Example C5, except that the coating material for forming a smooth coating film in Example C5 was changed to composition C5.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating film surface Pm was 3H. Further, the refractive index Nm of the resin forming the smooth coating film 4 was 1.51.

[Example C8]
An optical sheet of Example C8 was produced in the same manner as in Example C5 except that the coating material for forming a smooth coating film in Example C5 was changed to composition C2.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating surface Pm was F. In addition, the refractive index Nm of resin which comprises the smooth coating film 3 was 1.47.

[Example C9]
The coating composition for forming a smooth coating film in Example C5 remains as composition C3, and the composition C3 for coating composition for forming a smooth coating film described above is used as the resin composition for forming the unit optical element. In the same manner as described above, an optical sheet of Example C9 was produced.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the coating surface Pm was H. In addition, the refractive index Nm of resin which comprises the smooth coating film 3 was 1.51.

[Comparative Example C1]
An optical sheet of Comparative Example C1 was prepared in the same manner as in Example C1, except that the coating material for forming a smooth coating film in Example C1 was changed to the composition C1.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was B, and the hardness Hm of the coating film surface Pm was HB. Further, the refractive index Nm of the resin forming the smooth coating film 4 was 1.41.

[Comparative Example C2]
An optical sheet of Comparative Example C2 was produced in the same manner as in Example C5, except that the coating material for forming a smooth coating film in Example C5 was changed to the composition C1.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was HB, and the hardness Hm of the coating surface Pm was HB. Moreover, the refractive index Nm of resin which comprises the smooth coating film 3 was 1.41.

[Comparative Example C3]
An optical sheet of Comparative Example C3 was produced in the same manner as in Example C9, except that the coating material for forming a smooth coating film in Example C9 was changed to Composition C2.
Regarding the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was H, and the hardness Hm of the coating surface Pm was F. Moreover, the refractive index Nm of resin which comprises the smooth coating film 3 was 1.47.

[Comparative Example C4]
The coating composition for forming a smooth coating film in Example C5 remains as composition C3, and the composition C4 for coating composition for forming a smooth coating film is used as the resin composition for forming a unit optical element. In the same manner, an optical sheet of Comparative Example C4 was produced.
As for the pencil hardness of the obtained optical sheet, the hardness He of the optical element surface Pe was 2H, and the hardness Hm of the coating surface Pm was H. Further, the refractive index Nm of the resin forming the smooth coating film 3 was 1.51.

[Performance evaluation]
About the optical sheet of said Example C1-C9 and Comparative Example C1-C4, pencil hardness and abrasion resistance were evaluated. Moreover, the luminance was also measured for the optical sheets of Examples C1 to C7 and Comparative Examples C1 and C2. The pencil hardness test on the optical element surface Pe was performed by moving the pencil in the prism ridge direction.

(1) The pencil hardness was evaluated in the same manner as in Examples A1 to A9 and Comparative Examples A1 to A4 described above.
(2) The scratch resistance was evaluated in the same manner as in Examples A1 to A9 and Comparative Examples A1 to A4 described above.
(3) The luminance was evaluated in the same manner as in Examples B1 to B7 and Comparative Examples B1 and B2 described above. As for the evaluation method, Comparative Example C1 and Examples C1 to C4 were not provided with a coating film, and the unit optical element 2 had a luminance of Comparative Example D1 (Survey 2) of substantially the same resin as 100%. Evaluation in percentage, Comparative Example C2 and Examples C5 to C8, when no coating film is provided, the unit optical element 2 is substantially the same resin as Comparative Example D2 (Survey 2) when the luminance is 100% The percentage was evaluated.

[Performance comparison]
Table 4 shows the hardness He and hardness Hm in Examples C1 to C9 and Comparative Examples C1 to C4, the scratch resistance, the coating film refractive index, and the luminance in the front direction.

[Performance comparison]
Regarding Examples C1 to C9 and Comparative Examples C1 to C4, the relationship between the hardness Hm of the coating film surface Pm and the hardness Pe of the optical element surface He and the scratch resistance is the same as in Examples A1 to A9 shown in FIG. Similar to Examples A1-A4.

  Specifically, as shown in Table 4 and FIG. 2, in Comparative Example C3 and Comparative Example C4 in which the hardness Hm of the coating film surface Pm is lower than the hardness He of the optical element surface Pe, the resistance of the coating film surface Pm Abrasion became "bad". Further, in Comparative Examples C1 and C2 in which the hardness Hm of the coating film surface Pm is lower than “F” even if the hardness Hm of the coating film surface Pm is equal to or higher than the hardness He of the optical element surface Pe, the coating film The scratch resistance of the surface Pm did not become “excellent”. In Examples C1 to C9 where the hardness Hm is equal to or higher than the hardness He (hardness Hm ≧ hardness He) and the hardness Hm is equal to or higher than “F” (hardness Hm ≧ F), the scratch resistance of the coating surface Pm is “excellent”. As a result, the scratch resistance of the optical element surface Pe was “good” or higher, and the overall evaluation focusing on the scratch resistance on the coating film surface Pm was “good” or “good”.

  However, in Example C3, Example C4, and Example C7 in which “Hardness Hm−Hardness He> 3”, scratches that are considered to have no problem in practice are optically damaged on one or two optical sheets. It occurred on the element surface Pe. Also in Example C8 and Example C9 in which “Hardness Hm−Hardness He” is “1” or “0”, there is one or two optical scratches to the extent that there is no practical problem. It occurred on the optical element surface Pe of the sheet. On the other hand, in Example C1, Example C2, Example C5, and Example C6 satisfying the hardness He + 3 ≧ hardness Hm ≧ hardness He + 2, both the scratch resistance of the optical element surface Pe and the coating surface Pm is “excellent”. Evaluation became "(circle)".

(Evaluation of brightness)
As shown in Table 4, Examples C1 to C7 and Comparative Examples in which a coating film made of a resin having a refractive index lower than the refractive index 1.65 of the portion (PET film) facing the coating film 3 of the main body 1 was formed. C1 and C2 both exceeded 100%, and the brightness was higher than the brightness (100%) of Comparative Examples D1 and D2 in which such a coating film was not formed on the light incident surface.

DESCRIPTION OF SYMBOLS 1 Main-body part 1p One surface 1q The other surface 2 Unit optical element 3 Concavity and convexity coating film, coating film 4 Smooth coating film, coating films 10, 10a, 10b Optical sheet 10A Two-layered optical sheet 20 Other optical member which contacts (Light guide plate, liquid crystal panel, etc.)
30 (light source type) surface light source device 31 light source 32 light guide plate 40 liquid crystal display device 41 liquid crystal panel He pencil hardness Hm of optical element surface pencil hardness of uneven film surface nd normal Pe optical element surface Pm uneven film surface V Observer

Claims (8)

An optical sheet having a pair of opposing surfaces,
A sheet-like body,
Unit optical elements arranged on one surface of the main body, and
A coating film provided on the other surface of the main body,
One of the pair of surfaces is configured as an optical element surface formed by the unit optical element,
The other of the pair of surfaces is formed by a coating surface comprising the surface of the coating film,
When the hardness He of the optical element surface and the hardness Hm of the coating surface are evaluated using pencil hardness measured according to JIS K5600-5-4 (1999) (load 1000 g, speed 1 mm / s) The optical sheet is such that the hardness Hm is F or more (hardness Hm ≧ F) and the hardness Hm is more than the hardness He (hardness Hm ≧ hardness He). When the hardness of 1 unit on the pencil hardness scale is +1,
Hardness He + 3 ≧ Hardness Hm ≧ Hardness He + 2
The optical sheet according to claim 1, wherein   The optical sheet according to claim 1 or 2, wherein a refractive index Nm of the resin forming the coating film is smaller than a refractive index Ns of a portion forming the other surface in the main body portion.   The said coating film is an optical sheet as described in any one of Claims 1-3 whose said coating-film surface is an uneven | corrugated coating film in which the rough surface forms the microprotrusion.   The optical sheet according to claim 1, wherein the coating film is a smooth coating film having a smooth coating film surface. Two optical sheets according to any one of claims 1 to 5 are provided,
An optical member in which two optical sheets are superposed on each other in the same direction. A light source;
A surface light source device comprising the optical sheet according to claim 1 or the optical member according to claim 6. A surface light source device according to claim 7;
A transmissive liquid crystal display panel disposed to face the surface light source device.

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