KR101087552B1 - Optical sheet and backlight unit using the same - Google Patents

Abstract

An object of the present invention is to provide an optical sheet capable of preventing scratches on the surface of the other optical sheet or the like while preventing sticking with another optical sheet or the like laminated on the back surface side.
This invention is equipped with the transparent base material layer, the optical layer laminated | stacked on one surface side of this base material layer, and the sticking prevention layer laminated | stacked on the other surface side of a base material layer, and this sticking prevention layer is a fine uneven | corrugated shape on the whole surface of a surface. An optical sheet having a film having a double-island structure in which the sticking prevention layer is composed of a plurality of resins in which phase separation is performed, wherein the domain phase is dispersed in the matrix phase and the granular phase is dispersed in the domain phase. The main material in the matrix of the sticking prevention layer may be urethane (meth) acrylate resin, the main material on the domain is a (meth) acrylic resin, and the granular material is a (meth) acrylic resin.

Description

Optical sheet and backlight unit using the same {OPTICAL SHEET AND BACKLIGHT UNIT USING THE SAME}

The present invention relates to an optical sheet having a high sticking prevention function and a scratch prevention function and a backlight unit using the same.

Liquid crystal display devices are widely used as display devices for screens such as televisions and PCs, and are largely classified into a direct view type for directly viewing a display screen and a projection type for viewing an image reflected on the screen. There are a direct-type liquid crystal display device having a transmissive type that transmits light of a backlight, a reflective type that uses reflected light such as natural light or an indoor light without a backlight, and a semi-transmissive type that is a reflective type in a bright place and a transmissive type in a dark place. On the other hand, projection type liquid crystal display devices include a front type for illuminating an image on a front screen, and a rear type for putting an image into a display cabinet and illuminating an image. Today, direct-type, and transmissive-type liquid crystal displays are generally used as mainstream.

BACKGROUND ART In the transmissive liquid crystal display device, a backlight system that illuminates the liquid crystal layer from the back is widespread, and a backlight unit such as an edge light type (side light type) or a direct type is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 2, the edge light type backlight unit 20 generally includes a lamp 21 as a light source and a rectangular light guide plate 22 disposed so that an end thereof follows the lamp 21. ) And a plurality of optical sheets 23 stacked on the surface side of the light guide plate 22. LEDs (light emitting diodes), cold cathode tubes and the like are used as the lamp 21 as the light source, but LEDs are generally used in view of miniaturization and energy saving. The optical sheet 23 has optical functions such as diffusion and refraction with respect to transmitted light, (1) a prism sheet 24 arranged on the surface side of the light guide plate 22 and having a refractive function toward the normal direction side. (2) The light diffusion sheet 25 etc. which are arrange | positioned at the surface side of the prism sheet 24 and which mainly have a light-diffusion function are used.

Although not shown, in view of the light guiding properties of the light guide plate 22 and the optical function of the optical sheet included in the optical sheet 23, the optical sheet 23 such as a light diffusion sheet or a prism sheet is more numerous. There is also a backlight unit arranged in an array.

Referring to the function of the backlight unit 20, first, the light rays incident on the light guide plate 22 from the lamp 21 are reflected from the reflective dots or the reflective sheet (not shown) and the respective side surfaces of the light guide plate 22, It is emitted from the light guide plate 22 surface. Light rays emitted from the light guide plate 22 are incident on the prism sheet 24, are refracted toward the normal direction by a plurality of protruding prism portions formed on the surface, and are emitted from the surface. Subsequently, the light rays emitted from the surface of the prism sheet 24 are incident on the light diffusion sheet 25, diffused and emitted from the surface, and illuminate the entire liquid crystal layer not shown above.

Generally, the light-diffusion sheet 25 arrange | positioned and superposed on the surface of the prism sheet 24 is a base material layer 26 made of a transparent synthetic resin, and this base material layer 26 as shown in FIG.2 (b). The optical layer 27 laminated | stacked on the surface of), and the sticking prevention layer 28 laminated | stacked on the back surface of the base material layer 26 are provided. The optical layer 27 generally has a structure in which the resin beads 30 are dispersed in the binder 29, and is configured to perform a light diffusion function or the like on the transmitted light. In addition, the sticking prevention layer 28 has a structure in which a small amount of beads 32 are separated and dispersed in the binder 31, and a lower portion of the beads 32 protrudes from the back surface of the binder 31. The anti-sticking layer 28 adheres to the surface of another optical sheet or the like (prism sheet 24) on the back surface of the light diffusion sheet 25, i.e., sticks to generate interference fringes, or is wound in a roll shape in the manufacturing process. This prevents the problem that blocking (attachment) occurs when stored. In addition, since the vertices of the prism portion are not acute, and form a flat or curved surface, the prism sheet 24 and the back surface side of the light diffusion sheet 25 are in band contact with each other in a band shape. Sticking occurs in the strip shape.

As the beads 32 dispersed in the anti-sticking layer 28 of the light diffusion sheet 25, acrylic beads and the like are generally used, and since they are relatively hard, the light diffusion sheet ( The surface (prism part apex part) of the prism sheet 24 etc. laminated | stacked on the back surface side of 25) may be damaged. In addition, the beads 32 dispersed in the sticking prevention layer 28 come off in contact with the prism portion apex of the prism sheet 24, and the dropping portions of the beads 32 are a cause of scratches. Scratches on the optical sheet cause luminance unevenness of the liquid crystal display device.

Therefore, in order to prevent scratches of the prism sheet or the like and other optical sheets or the light guide plate laminated on the back side, an optical sheet (see Japanese Patent Application Laid-Open No. 2004-85626, etc.) provided with the back surface is coated with a coating solution. An anti-blocking curable resin composition (refer to Unexamined-Japanese-Patent No. 2007-182519, etc.) which forms a fine unevenness | corrugation by surface hardening is developed.

However, even in the optical sheet provided with the above-mentioned scratch prevention layer, since the fine beads for preventing sticking exist, the damage | wound to another optical sheet etc. cannot fully be prevented. In addition, in the case where the unevenness is formed on the surface by the anti-blocking curable resin composition, the unevenness of the surface is too fine and the anti-sticking performance is not sufficient, and the anti-blocking curable resin composition for improving the brightness of the optical sheet. When the coating film is thinned, the unevenness | corrugation formed becomes finer, and there exists a problem that the sticking prevention performance further falls short.

Japanese Patent Laid-Open No. 2004-85626 Japanese Patent Application Laid-Open No. 2007-182519

(Summary of invention)

(Tasks to be solved by the invention)

This invention is made | formed in view of these problems, and uses the optical sheet which can prevent the damage | wound to the surface, such as another optical sheet, while preventing sticking with the other optical sheet etc. laminated | stacked on the back surface side, and this optical sheet is used. Therefore, it is an object of the present invention to provide a high quality backlight unit by preventing luminance unevenness and interference fringes caused by scratches.

The invention made to solve the above problems,

A transparent base material layer, the optical layer laminated | stacked on one surface side of this base material layer, and the sticking prevention layer laminated | stacked on the other surface side of a base material layer, and this sticking prevention layer has the fine uneven | corrugated shape in the whole surface of a surface As a sheet,

The sticking prevention layer is composed of a plurality of resins separated in phase, and has a double island-in-sea structure in which the domain phase is dispersed in the matrix phase and the granular phase is dispersed in the domain phase. It is an optical sheet.

The optical sheet has a double-inorganic structure in which the sticking prevention layer is composed of a plurality of resins in which phase separation is performed, in which the domain phase is dispersed in the matrix phase, and the granular phase is dispersed in the domain phase. According to the said optical sheet, since the sticking prevention layer has such a double islands structure, the fine unevenness | corrugation of the surface of a sticking prevention layer is formed effectively. Thereby, the sticking prevention layer can exhibit high sticking prevention performance, and can prevent the sticking with the other sheet laminated | stacked on the sticking prevention layer side suitably. In addition, the said optical sheet can prevent the damage by the unevenness | corrugation on the surface of a sticking prevention layer at the same time. Moreover, according to the said optical sheet, since the sticking prevention layer surface has such a double islands-in-sea structure, even if the thickness of a sticking prevention layer is made thin, it becomes easy to form the unevenness | corrugation sufficient to exhibit sticking prevention performance. Thus, since the said optical sheet can make thickness of a sticking prevention layer thin, the fall of a brightness | luminance can be prevented by providing a sticking prevention layer. Moreover, it can be set as the optical sheet provided with the sticking prevention layer which has a desired suitable thickness and surface roughness.

The main material in the matrix phase of the sticking prevention layer may be a urethane (meth) acrylate resin, a domain main material is a (meth) acrylic resin, and a granular material is a (meth) acrylic resin. When the phase-separated base material of each resin phase which comprises the sticking prevention layer is said resin, the unevenness | corrugation of the surface of a sticking prevention layer is formed more effectively, and the sticking prevention performance of the said optical sheet further improves. In addition, since all resin which forms a sticking prevention layer is resin of (meth) acrylic-type, the said optical sheet can ensure high brightness.

The convex part should just be formed scattered by the granular image distributed on the surface of the said sticking prevention layer. The convex portions are scattered on the surface of the sticking prevention layer due to the dispersed granular phase, so that the sticking preventing performance of the optical sheet is exhibited very effectively. In addition, since the convex part of the surface of the said sticking prevention layer is formed of resin, the flaw to another optical sheet etc. which originate in an uneven | corrugated shape can be prevented.

The average thickness of the anti-sticking layer is 0.5 μm or more and 4 μm or less, and the arithmetic mean roughness Ra of the surface of the anti-sticking layer is 0.03 μm or more and 0.3 μm or less, and the average length RSm of the roughness curve element is 40 μm or more 400 It should just be a micrometer or less. The arithmetic mean roughness Ra and the average length RSm of the roughness curve element on the surface of the anti-sticking layer are relatively small values in the above ranges, so that the prevention of sticking with other sheets laminated on the anti-sticking layer side can be suitably prevented. In addition, the flaw resulting from the fine uneven | corrugated shape of the surface of this sticking prevention layer can be prevented. Moreover, since the average thickness of the sticking prevention layer is as thin as 0.5 micrometer or more and 4 micrometers or less, the said optical sheet can prevent the fall of the brightness by providing a sticking prevention layer.

Therefore, in the backlight unit for a liquid crystal display device which disperse | distributes the light ray generate | occur | produced from a lamp, and guides it to the surface side, when it is provided with the said optical sheet, the high scratch prevention property of the said optical sheet is prevented by the damage of other optical sheets, etc. The occurrence of luminance unevenness and the generation of interference fringes can be prevented, so that the quality of the liquid crystal display screen can be improved, and the handling when manufacturing, transporting, storage and the like becomes easy.

Here, the term "optical layer" means a layer that performs a predetermined optical function with respect to transmitted light, and specifically, (a) a light diffusing layer having a light diffusing agent in the binder, and (b) almost embossing on the surface thereof. The light diffusing layer having fine irregularities uniformly formed, the (c) prism layer having a triangular prism portion in a stripe shape, and the like are applicable, and the concept includes a case where the substrate layer is formed with a certain shape. In addition, "arithmetic mean roughness (Ra)" and "10-point average roughness (Rz)" comply with JIS B0601-1994, and "average length (RSm) of roughness curve element" and "square root mean square roughness (Rq)" Is a value of cut-off (lambda) c2.5mm and an evaluation length of 12.5mm according to JIS B0601-2001. "Pencil hardness" is a pencil scraping value based on the test method 8.4 of JIS K5400.

As described above, the optical sheet of the present invention has sufficient irregularities on the surface of the anti-sticking layer, and furthermore, even if the thickness of the anti-sticking layer is reduced, sufficient irregularities can be ensured, thus preventing high sticking to other sheets or the like. While securing a function, it is possible to prevent scratches on the surface of other sheets or the like. In addition, the backlight unit of the present invention can prevent occurrence of luminance unevenness and interference fringes caused by scratches of an optical sheet, a light guide plate, or the like, and facilitates handling during manufacture, transportation, storage, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows the optical sheet which concerns on one Embodiment of this invention.
2 (a) is a schematic perspective view showing a general edge light type backlight unit, and (b) is a schematic cross sectional view showing a general light diffusion sheet.

(Form to carry out invention)

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

The optical sheet 1 of FIG. 1 has the base material layer 2, the optical layer 3 laminated | stacked on one surface side of this base material layer 2, and the sticky layer laminated | stacked on the other surface side of this base material layer 2 The king prevention layer 4 is provided.

Since the base material layer 2 needs to transmit light, it is formed of transparent, especially colorless and transparent glass or synthetic resin. The synthetic resin used for the base material layer 2 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride, and the like. Can be. Especially, the polyethylene terephthalate which is excellent in transparency and high in strength is preferable, and the polyethylene terephthalate which the bending performance improved was especially preferable.

Although the thickness (average thickness) of the base material layer 2 is not specifically limited, For example, 10 micrometers or more and 500 micrometers or less, Preferably 35 micrometers or more and 250 micrometers or less, Especially preferably, they are 50 micrometers or more and 188 micrometers or less. do. When the thickness of the base material layer 2 is less than the said range, when coating the resin composition for forming the optical layer 3, curling will generate | occur | produce easily and troubles, such as handling become difficult, arise. On the contrary, when the thickness of the base material layer 2 exceeds the said range, the brightness | luminance of a liquid crystal display device may fall, and also the thickness of a backlight unit may become large and it is against the request of thickness reduction of a liquid crystal display device.

The sticking prevention layer 4 has the fine uneven | corrugated shape 7 in the whole surface. For this reason, when this optical sheet 1 is piled up and arrange | positioned on the surface of other optical sheets, such as a prism sheet, light guide plate, etc., the convex part of the fine uneven shape 7 abuts on the surface of another optical sheet, etc., and the optical sheet 1 The entire back surface of the () does not contact other optical sheets or the like. Thereby, sticking with the optical sheet 1 and another optical sheet etc. can be prevented, and the luminance nonuniformity of the screen of a liquid crystal display device can be suppressed.

In the optical sheet 1 of the present invention, the surface of the anti-sticking layer 4 is composed of a plurality of resins in which phases are separated, and has a double-inorganic structure in which the domain phase is dispersed in the matrix phase and the granular phase is dispersed in the domain phase. have. Since the said sticking prevention layer has such a double islands structure, the fine unevenness | corrugation of the surface of a sticking prevention layer is formed effectively. By this, high sticking prevention performance can be exhibited and sticking with the other sheet laminated | stacked on the sticking prevention layer side can be prevented suitably. In addition to this, scratches due to irregularities on the surface of the sticking prevention layer can be prevented. Moreover, since the said sticking prevention layer has such a double islands-in-sea structure, even if the thickness of a sticking prevention layer is made thin, it becomes easy to form the unevenness | corrugation sufficient for sticking prevention. Thereby, since the thickness of a sticking prevention layer can be made thin, the fall of the brightness by providing a sticking prevention layer can be prevented. Moreover, it can be set as the optical sheet which has a sticking prevention layer which has a desired suitable thickness and surface roughness.

Since the surface of the anti-sticking layer has a double island-in-sea structure, fine unevenness is effectively formed, and even if the thickness of the anti-sticking layer is thin, the reason why the formation of sufficient unevenness is easy is not necessarily clear. By synergistic combination of polymerization shrinkage and particle formation respectively occurring in each resin phase, it is possible to form finer irregularities.

It can be observed that such a sticking prevention layer has a dual islands structure in which the domain phase is dispersed in the matrix phase and the granular phase is dispersed in the domain phase, for example, using an electron microscope or the like.

Although it does not specifically limit as resin which forms each phase in the said sticking prevention layer, For example, an acrylic resin, a urethane (meth) acrylate resin, an epoxy (meth) acrylate resin, ester (meth) acrylate resin, an olefin Resins, polystyrene resins, styrene copolymers, norbornene resins, polycarbonate resins, polyether resins, polyethersulfone resins, polyester resins, polyurethane resins, polysiloxane resins, polysilane resins, polyamide resins, polyimide resins, Melamine resin, a fluororesin, etc. are mentioned. As (meth) acrylic resin, the homopolymer or copolymer of a (meth) acryl monomer, the copolymer of the (meth) acryl monomer, and the monomer which has another ethylenically unsaturated double bond, etc. are mentioned. Examples of the olefin resins include polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ionomers, ethylene-vinyl alcohol copolymers, ethylene-vinyl chloride copolymers, and the like. Polyethylene glycol, polypropylene glycol, polytetramethylene glycol etc. are mentioned as polyether resin. Examples of the polyester resins include polyethylene terephthalate, polybutylene terephthalate, unsaturated polyester resins and alkyd resins. As resin, the copolymer which has 2 or more types of structural units of these resin may be sufficient, and the copolymer which consists of the structural unit of these resin and other monomer units may be sufficient.

Especially, as a matrix main material, it is preferable that it is urethane (meth) acrylate resin, epoxy (meth) acrylate resin, or ester (meth) acrylate resin. By using the acrylic resin containing such a polar group as a main material in a matrix form, the said double islands structure is effectively expressed, and the unevenness | corrugation of the sticking prevention layer surface becomes large. As a result, the sticking prevention performance of the said optical sheet becomes high. In addition, even when the thickness of the anti-sticking layer is thin, sufficient unevenness is formed on the anti-sticking layer surface, so that the anti-sticking performance of the optical sheet is secured. Among these, a urethane (meth) acrylate resin is especially preferable at the point that a double islands structure is expressed more effectively, and the sticking prevention performance of the optical sheet obtained becomes higher.

As a main material on a domain, (meth) acrylic resin is preferable. Moreover, as a granular main material, (meth) acrylic resin is preferable. An optical sheet with high brightness can be obtained by using an acrylic resin as the main material of domain and granular phases.

In the said sticking prevention layer, it is especially preferable that the main material in a matrix form is a urethane (meth) acrylate resin, the main material of a domain is (meth) acrylate, and a granular material is a (meth) acrylic resin. By employing such a combination as the resin forming the sticking prevention layer, the double islands structure is particularly effectively expressed. As a result, uneven | corrugated formation of the sticking prevention layer surface is especially accelerated | stimulated, and the sticking prevention performance of the said optical sheet can be made high. In addition, it is possible to make an optical sheet with high brightness.

It is particularly preferable that the convex portions are scattered on the surface of the sticking prevention layer due to the dispersed granular phase. In the said optical sheet, since such a convex part is formed in the sticking prevention layer surface, high sticking prevention performance is exhibited and sticking with the other sheet laminated | stacked on the sticking prevention layer side can be prevented suitably. Moreover, the said convex part is formed of resin and its hardness is comparatively low. As a result, the said optical sheet can prevent the damage by the unevenness | corrugation of the sticking prevention layer surface.

As a minimum of the average thickness of the sticking prevention layer 4, 0.5 micrometer is preferable, 1 micrometer is more preferable, 1.5 micrometer is especially preferable. On the other hand, as an upper limit of the average thickness of the sticking prevention layer 4, 4 micrometers is preferable, 3.5 micrometers is more preferable, and 3 micrometers is especially preferable. If the average thickness of the sticking prevention layer 4 is smaller than the lower limit, it is difficult to form an uneven shape having a sufficient size at the time of forming the fine uneven shape 7 by coating and curing the resin and monomer or oligomer described later. do. On the contrary, when the average thickness of the anti-sticking layer 4 exceeds the upper limit, the amount of light absorption by the anti-sticking layer 4 increases, so that the light transmittance decreases.

As a minimum of arithmetic mean roughness Ra of the surface of the sticking prevention layer 4, 0.03 micrometer is preferable, 0.05 micrometer is more preferable, 0.08 micrometer is especially preferable. On the other hand, as an upper limit of this arithmetic mean roughness Ra, 0.3 micrometer is preferable, 0.25 micrometer is more preferable, 0.2 micrometer is especially preferable. If the arithmetic mean roughness Ra of the surface of the anti-sticking layer 4 is smaller than the lower limit, the fine concavo-convex shape 7 becomes small, so that portions other than the convex portions also come into contact with the surfaces of other optical sheets and the like. There is a fear that the protection function is not exerted. On the contrary, when the arithmetic mean roughness Ra of the surface of the sticking prevention layer 4 exceeds the said upper limit, the uneven | corrugated shape becomes rough and there exists a possibility that surface flaw formation, such as another optical sheet arrange | positioned at the back surface, may arise.

As a minimum of the average length (RSm) of the roughness curve element of the surface of the sticking prevention layer 4, 40 micrometers is preferable, 80 micrometers is more preferable, 120 micrometers is especially preferable. On the other hand, as an upper limit of the average length RSm of this roughness curve element, 400 micrometers is preferable, 280 micrometers is more preferable, 240 micrometers is especially preferable. The average length RSm of the roughness curve element on the surface of the anti-sticking layer 4 takes a relatively small value within the above range so that the fine concavo-convex shape 7 is island-shaped and uniformly formed on the entire surface of the surface. Even when Ra is a relatively small value within the above range, it is possible to prevent the occurrence of interference fringes due to adhesion (sticking) to the light guide plate surface or the like.

In particular, when the arithmetic mean roughness Ra is relatively small, the average length RSm of the roughness curve element is in the above range, and the fine concavo-convex shape 7 is formed in an island shape and is constant on the entire surface of the surface, thereby sticking. Even when the prevention layer 4 is in contact with the band-shaped prism portion apex on the surface of the prism sheet, it is possible to produce a part which is not in contact with the part that abuts on the band-shaped part. Therefore, according to the said optical sheet 1, the sticking prevention function with respect to the prism sheet surface (surface on the prism part side) can be exhibited effectively.

When the average length RSm of this roughness curved element is smaller than the said lower limit, the size of each convex part becomes small, and there exists a possibility of causing the flaw formation of the surface of another optical sheet etc. which abut. In the case where the prism sheet surface (surface on the prism portion side) is in contact with the anti-sticking layer 4, at the apex of the strip-shaped prism portion in contact with the anti-sticking layer 4, a portion which does not abut against the abutting portion does not occur. There is concern. On the contrary, when the average length RSm of the roughness curved element exceeds the upper limit, fine irregularities are not sufficiently formed, and there is a possibility that interference fringes may be generated by contacting surfaces of other optical sheets or the like on surfaces other than the convex portions. .

As a minimum of 10-point average roughness Rz of the sticking prevention layer 4 surface, 0.2 micrometer is preferable, 0.3 micrometer is especially preferable, and 0.4 micrometer is more preferable. On the other hand, as an upper limit of this 10-point average roughness Rz, 1.4 micrometers is preferable, 1 micrometer is especially preferable, and 0.8 micrometer is more preferable. When the ten-point average roughness Rz of the surface of the anti-sticking layer 4 is smaller than the lower limit, in the fine uneven shape 7 on the surface of the anti-sticking layer 4, portions other than the convex portions may be different from each other. There is a fear that sticking may occur by coming into contact with the surface. On the contrary, when this 10-point average roughness Rz is larger than the said upper limit, the uneven | corrugated shape will become too rough and there exists a possibility of causing scratches of the surface of other optical sheets etc. laminated | stacked on the back surface side.

As a minimum of ratio (Rz / Ra) with respect to the arithmetic mean roughness Ra of the 10-point average roughness Rz of the sticking prevention layer 4, 3 is preferable, 4 is especially preferable, and 5 is more preferable. On the other hand, as an upper limit of this ratio, 10 is preferable, 9 is especially preferable, and 8 is more preferable. By setting the ratio (Rz / Ra) to the arithmetic mean roughness (Ra) of the ten-point average roughness (Rz) of the sticking prevention layer (4) to a small value within the above range, the optical sheet 1 has unevenness in which the height is relatively even. The shape is made constant. Therefore, the said optical sheet 1 can prevent the damage of the other sheet | seat which generate | occur | produces by force concentrating especially in the protruding part among the convex parts in the fine uneven shape 7 of the sticking prevention layer 4. As shown in FIG. Moreover, the flaw of the surface, such as another optical sheet, by which the protruding convex part falls out can be prevented. When the ratio (Rz / Ra) to the arithmetic mean roughness Ra of the ten-point average roughness Rz of the sticking prevention layer 4 is smaller than the lower limit, sufficient formation of this fine uneven shape 7 becomes difficult. . On the contrary, when this ratio (Rz / Ra) exceeds the said upper limit, the difference of the height of the convex part in the fine uneven | corrugated shape 7 will become remarkable, and a force will be concentrated in the part, and it will be with respect to the surface of another optical sheet etc. Scratches may occur.

As a minimum of the root mean square roughness Rq of the surface of the sticking prevention layer 4, 0.04 micrometer is preferable, 0.07 micrometer is especially preferable, and 0.1 micrometer is more preferable. On the other hand, as an upper limit of this root mean square roughness Rq, 0.4 micrometer is preferable, 0.3 is especially preferable, and 0.2 is more preferable. According to the said optical sheet 1, since the square root mean square roughness Rq of the surface of the sticking prevention layer 4 has a small value in the said range, the inclination of the fine uneven | corrugated shape 7 will be formed smoothly, and it will laminate | stack Scratches of other optical sheets can be prevented. When the square root mean square roughness Rq of the surface of the sticking prevention layer 4 is smaller than the said lower limit, since the formation of the fine uneven | corrugated shape 7 is not enough, there exists a possibility that the sticking prevention function may fall. On the contrary, when the square root mean square roughness Rq exceeds the upper limit, a sharp inclined portion is formed in the fine uneven shape 7, which may cause scratches on the surface of the light guide plate or the like near this steep slope.

As a minimum of the average height h of each convex part of the sticking prevention layer 4 surface, 0.5 micrometer is preferable, 0.7 micrometer is especially preferable, and 1 micrometer is more especially preferable. Moreover, as an upper limit of this average height h, 3 micrometers is preferable, 2.5 micrometers is more preferable, and 2 micrometers is more especially preferable. According to the said optical sheet, by making the average height h of each convex part of the surface of the sticking prevention layer 4 comparatively small as mentioned above, the flaw formation of surfaces, such as another optical sheet, can be reduced, and flaw formation When this happened, the depth of the wound can be made shallow. If the average height h of each convex part is smaller than the said minimum, sufficient sticking prevention function cannot be exhibited. On the contrary, when this average height h exceeds the said upper limit, there exists a possibility that the flaw formation of another optical sheet surface may arise, and the flaw which this generate | occur | produces may become deep. In addition, this average height h is observed in a predetermined area with a laser microscope, and is computed by the average height of the upper 16 convex parts with a high height among the several convex parts observed.

A sticking preventive layer (4) as the lower limit of the average protrusion diameter (r ₁₎ of each convex portion of the surface 2㎛ are preferred, and 2.5㎛ particularly preferred, more particularly preferred is 3㎛. On the other hand, if the mean projection The upper limit of the diameter (r ₁₎ and 5㎛ are preferred, and particularly preferred is 4.5㎛, it is more particularly preferred 4㎛. According to the art the optical sheet, and thus, a sticking prevention layer 4, an average protrusion diameter (r ₁₎ of each convex portion of the surface by comparatively small as described above, to reduce the scratch generated on the surface, such as another optical sheet, and In addition, the scratch width of the generated scratch can be narrowed. If the average protrusion diameter r ₁ of each convex part is smaller than the said minimum, sufficient sticking prevention function cannot be exhibited. On the contrary, if the average protrusion diameter (r ₁₎ when it exceeds the foregoing upper limit, causing a scratch generated in the other optical surface of the sheet, and is also widely scratch width of the scratches to occur. In addition, this average protrusion diameter r ₁ observes a predetermined area inside by a laser microscope, and is computed by the average protrusion diameter of the upper 16 convex parts with a high height among the several convex parts observed. In addition, the projection diameter (r ₁ ) refers to the diameter of the cross section cut at a height (0.9h) of 90% of the height (h) of the convex portion, the average of each projection diameter is the Ferret Diameter (constant direction) Space | interval when the projection image is pinched | interposed by the parallel line of ().

A sticking preventive layer (4) As the lower limit of the average diameter (r ₂₎ of each convex portion of the surface 40㎛ are preferred, and 60㎛ particularly preferred, more particularly preferred 70㎛. Meanwhile, as the upper limit of the average diameter (r ₂₎ and 200㎛ are preferred, and 150㎛ are particularly preferred, more particularly preferred is 120㎛. According to the art the optical sheet, and thus a sticking prevention layer 4 by an average diameter (r ₂₎ of each convex portion of the surface is relatively large as described above, the scratches deep when the wake generated scratches occurred on the other optical surface of the sheet It can be suppressed shallowly. If the average diameter (r ₂₎ is less than the lower limit of each of the convex portions it can not exhibit a sufficient sticking resistance. On the other hand, the average diameter (r ₂₎ If this exceeds the upper limit, as well as the load tends to occur scratches generated on the other optical surface of the sheet, the wound turns becomes a deeper depth. In addition, the average diameter (r ₂₎ is calculated by the average diameter of observing a predetermined area in a laser microscope, of a plurality of convex portions is observed, the higher the height of the convex portion 16 higher. In addition, each diameter means the diameter of the cross section cut | disconnected at the height (0.05h) of 5% of the height (h) of a convex part, and the average of each diameter is this Feret diameter (when the projection image is sandwiched between parallel parallel lines). Time interval).

A sticking preventive layer (4) as the lower limit of the height ratio (h / r ₂₎ of each convex portion of the surface is preferably 1/400, and 1/200 is particularly preferable, and 1/150 is even more particularly preferred, 1/120 This is even more preferred. In addition, 1/10 are preferred as the upper limit of this height ratio (h / r _2), and 1/30 are particularly preferred, more particularly preferred and 1/60, 1/80 is a still more particularly preferred. According to the said optical sheet, by making small the height ratio (h / r <_2> ) of each convex part on the surface of the sticking prevention layer 4 as mentioned above, while suppressing the generation | occurrence | production of the flaw of the surface of another optical sheet, and creating a flaw, In this case, the size of the scratch itself can be reduced. This height ratio (h / r ₂₎ is less than the lower limit, there is a fear not be able to exert sufficient sticking resistance. On the other hand, the height ratio (h / r ₂₎ if it exceeds the upper limit, and the dimensions of the other optical sheet liable to cause scratches formed on the surface as well as load, scratch itself.

In addition, non-art sticking prevention layer 4, the convex portion of the surface, and thus a relatively small average height (h), relatively small average protrusion diameter (r _1), a relatively large mean diameter (r ₂₎ and a small height (h / By having r ₂ ), the frictional force at the surface in contact with the layer can be improved. According to the said optical sheet 1 provided with such a sticking prevention layer 4, the friction between this sticking prevention layer 4 and another optical sheet or prism sheet which contact this layer becomes high, and a slip is prevented as a result. Scratches on the surface of another optical sheet or prism sheet can be suppressed by suppressing fine shifts generated between these sheets.

As a minimum of the density of the presence of the convex part of the sticking prevention layer 4 surface, 40 piece / mm <^2> is preferable, 60 piece / mm <^2> is especially preferable, and 80 piece / mm <^2> is more especially preferable. Moreover, as an upper limit of the density of this convex part, 500 piece / mm <^2> is preferable, 400 piece / mm <^2> is especially preferable, and 300 piece / mm <^2> is more especially preferable. If the presence density of the convex part of the surface of the sticking prevention layer 4 is smaller than the said minimum, there exists a possibility that it may become impossible to exhibit sufficient sticking prevention function. On the contrary, when the density | concentration of this convex part is larger than the said upper limit, it will become easy to produce the flaw formation of the surface of another optical sheet. In addition, the presence density of this convex part measures the number of the convex parts in the visual field magnified 1000 times by the laser microscope, and calculates it using the viewing area.

In addition, the average height (h), an average protrusion diameter (r _1), an average diameter (r ₂₎ and a convex portion at the time of calculating the existence density is a sticking preventive layer (4) refers to a height above the surface of the projection 0.2㎛ .

As a minimum of the pencil hardness of the sticking prevention layer 4 surface, when the base material layer 2 is glass, H is preferable and 2H is especially preferable. On the other hand, as an upper limit of this pencil hardness, 5H is preferable and 4H is especially preferable. Moreover, when the base material layer 2 is synthetic resins, such as polyethylene terephthalate, B is preferable and HB is especially preferable as a minimum of the pencil hardness of the anti-sticking layer 4 surface. On the other hand, as an upper limit of the pencil hardness in this case, 3H is preferable and 2H is especially preferable. According to the said optical sheet 1, in addition to having the shape of the sticking prevention layer 4 in the said shape, since the pencil hardness is the said range, while exhibiting an anti-sticking function effectively, the damage of the other sheet laminated can be prevented. . When the pencil hardness of the surface of the sticking prevention layer 4 is smaller than the lower limit, the unevenness is fine, so that the tip and the like are easily broken, and as a result, scratches may occur on the surface of the light guide plate or the like. On the contrary, when this pencil hardness exceeds the said upper limit, the fine unevenness | corrugation shape itself which has a high hardness may generate | occur | produce a flaw formation to the surface, such as a light guide plate.

<Curable composition for sticking prevention layer formation>

The sticking prevention layer 4 can be formed by coating and hardening the curable composition containing the three components which are at least 1 sort (s) selected from the group which consists of a polymer, an oligomer, and a monomer each independently. According to the said curable composition, when a curable composition is coated and hardened | cured, a matrix form, a domain form, and a granular form are formed from three components contained, and the sticking prevention layer which has said double islands-in-sea structure is formed. Formation of such a double-island island structure may arise at the time of apply | coating the said curable composition to a base material layer, based on the difference in the physical property of each component, and at the time of subsequent hardening, may arise due to the difference in the physical property of formed resin.

As said polymer, a (meth) acryl polymer, polyolefin, polyether resin, polyether sulfone, polystyrene, styrene copolymer, norbornene resin, polycarbonate, polyester, polyurethane, polysiloxane, polysilane, poly Amide, polyimide, melamine resin or fluorine resin. As a (meth) acryl polymer, the homopolymer or copolymer of a (meth) acryl monomer, the copolymer of the (meth) acryl monomer, and the monomer which has another ethylenically unsaturated double bond, etc. are mentioned. Examples of the polyolefin include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ionomer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer and the like. Polyethylene glycol, polypropylene glycol, polytetramethylene glycol etc. are mentioned as polyether resin. Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, unsaturated polyester, alkyd resin, and the like. As a polymer, the copolymer which has 2 or more types of structural units of these polymers may be sufficient, and the copolymer which consists of structural units of these polymers and the monomer unit other than that may be sufficient. Among these, from the viewpoint of uneven formation being accelerated and the anti-sticking performance of the optical sheet improved, a homopolymer or copolymer of a (meth) acryl monomer is preferable, and a copolymer of a (meth) acryl monomer is more preferable. . As the polymer, one kind or a plurality of kinds thereof can be used.

As a minimum of the weight average molecular weight of the said polymer, 2,000 is preferable and 5,000 is more preferable. On the other hand, as an upper limit of the weight average molecular weight of a polymer, 100,000 is preferable and 50,000 is more preferable. If the weight average molecular weight of a polymer is smaller than the said lower limit, the unevenness | corrugation of the sticking prevention layer formed will become small, and there exists a possibility that the sticking prevention performance may fall. On the contrary, when the weight average molecular weight of a polymer exceeds the said upper limit, the hardness of the uneven | corrugated material of a sticking prevention layer will become high, and there exists a possibility that the flaw formation, such as an optical sheet which contact | connects a sticking prevention layer, may arise.

As said oligomer, the low molecular weight thing of the said polymer, etc. are mentioned. As an oligomer, the number of repeating units is 3-10, and the weight average molecular weight is 8,000 or less is preferable. As an oligomer, the copolymer which has 2 or more types of structural units of these oligomers may be sufficient, and the copolymer which consists of the structural units of these oligomers and other monomer units may be sufficient. As an oligomer, one type or multiple types can be used.

As said monomer, as long as it is a compound which has a functional group which can superpose | polymerize, it can be used. As a functional group which can superpose | polymerize, an unsaturated double bond, an epoxy group, etc. are illustrated, for example, A unsaturated double bond is preferable and a (meth) acryloyl group is especially preferable at the point which is easy to superpose | polymerize. Moreover, as a monomer, since the unevenness | corrugation of the sticking prevention layer surface becomes large, a polyfunctional monomer is preferable. (Meth) acrylate esters, such as a polyhydric alcohol, etc. are mentioned as a polyfunctional monomer, Specifically, 1, 6- hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene glycol di Bifunctional (meth) acrylates such as (meth) acrylate; Trifunctional (meth) acrylates such as trimetholpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and glycerol tri (meth) acrylate; Tetrafunctional (meth) acrylates such as pentaerythritol tetra (meth) acrylate and ditrimetholpropane tetra (meth) acrylate; 5-functional (meth) acrylates such as dipentaerythritol penta (meth) acrylate; 6-functional (meth) acrylates, such as dipentaerythritol hexa (meth) acrylate and sorbitol hexa (meth) acrylate, etc. are illustrated. The monomers may be functional groups other than polymerizable functional groups such as urethane groups, isocyanurate groups, urea groups, carbonate groups, amide groups, ester groups, carboxyl groups, ether groups, imino groups, amino groups, hydroxyl groups and the like. You may have in a molecule | numerator. In addition, the monomer may have atoms, such as halogen, silicon, sulfur, and phosphorus, such as fluorine and chlorine.

It is preferable that the three components contained in the said curable composition have functional groups which mutually react, respectively. When each component has such a functional group, the intensity | strength of the sticking prevention layer obtained will become high and durability can be improved. As a combination of such functional groups, for example, an ethylenically unsaturated group, an ethylenically unsaturated group, a functional group (hydroxyl group, an amino group, a thiol group, a carboxyl group, etc.) and an epoxy group having an active hydrogen, a functional group having an active hydrogen, an isocyanate group, active The functional group which has hydrogen, the functional group which has active hydrogen, a silanol group, a silanol group, a silanol group, an epoxy group, active methylene group, acryloyl group, an oxazoline group, a carboxyl group, etc. are mentioned. Among them, the combination produced is preferably a combination of an ethylenically unsaturated group and an ethylenically unsaturated group as the functional groups reacting with each other in that the resulting bond is firm and the formation of irregularities on the surface of the sticking prevention layer is promoted. Moreover, it is preferable that all three components contained in the said curable composition have ethylenically unsaturated group. Thereby, while the intensity | strength of a sticking prevention layer further improves, the formation of the unevenness | corrugation of the sticking prevention layer surface is further accelerated. Although it does not specifically limit as ethylenically unsaturated group, A (meth) acryloyl group is especially preferable at the point which superposition | polymerization is easy.

From the viewpoint of promoting the formation of the double islands-in-sea structure and increasing the unevenness of the surface of the sticking prevention layer, the curable composition preferably includes at least one polymer component, and preferably contains at least one monomer or oligomer component. By employing such a combination as each component of the curable composition, a granular phase is effectively formed from the polymer component to be blended, and convex portions are scattered on the surface of the anti-sticking layer by the granular phase, so that the optical sheet has high sticking. Prevention performance can be exhibited. Moreover, since the convex part of the surface of the said sticking prevention layer is formed of resin, the damage | wound to other optical sheets etc. which originate in an uneven | corrugated shape can be prevented.

Moreover, it is especially preferable that one component is a polymer, another one component is a monomer or an oligomer, and the other one component is a monomer or oligomer which has a polar group among the said three components. When the curable composition contains a monomer or an oligomer having a polar group as one component, phase separation between the matrix phase and the domain phase is promoted, and irregularities are formed more effectively, so that the anti-sticking performance of the resulting optical sheet is further improved. When the curable composition has such a component, a dispersed phase in which the monomer or oligomer is cured is dispersed in a matrix formed by curing the monomer or oligomer having a polar group, and a granular phase in which the polymer is cured is present in the dispersion layer. A double islands structure is formed. Thereby, the unevenness | corrugation formed becomes large and the sticking prevention performance of the optical sheet obtained becomes high.

The polar group is not particularly limited as long as it is an organic group in which polarization is generated by atoms having high electronegativity, such as oxygen, nitrogen, sulfur, or halogen, and examples thereof include urethane groups, isocyanurate groups, urea groups, and carbonate groups. , Amide group, ester group, carboxyl group, acid anhydride group, ether group, epoxy group, imino group or amino group. Among these, a urethane group or an isocyanurate group is preferable at the point which the said double-island island structure is easily formed, the unevenness | corrugation of the surface of the said sticking prevention layer becomes large, and the sticking prevention performance of the said optical sheet becomes high. As a specific example of the monomer or oligomer which has a polar group, a urethane (meth) acrylate, an epoxy (meth) acrylate, polyester (meth) acrylate, etc. are mentioned. Among these, urethane (meth) acrylate is particularly preferable because the double islands-in-sea structure is easily formed, the unevenness of the surface of the anti-sticking layer is increased, and the anti-sticking performance of the optical sheet is increased.

Urethane (meth) acrylate is a monomer or oligomer which has a functional group of both a urethane group (-N-CO-O-) and a (meth) acryloyl group in 1 molecule. Urethane (meth) acrylate can be obtained by reacting polyfunctional isocyanate, the compound which has active hydrogen, such as a (meth) acryloyl group, a hydroxyl group, and an amino group, and polyol as needed, for example. Examples of the polyfunctional isocyanate include diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, 2,2, 4-trimethylhexamethylene diisocyanate, cyclohexyl methane diisocyanate, methylcyclohexane diisocyanate, isopropylidene bis (4-cyclohexyl isocyanate), hexamethylene diisocyanate, etc. are mentioned. Modified products such as bifunctional or polyfunctional isocyanate trimers containing isocyanurate groups of these polyfunctional isocyanates can also be used.

As a compound which has a (meth) acryloyl group and active hydrogen, Hydroxyalkyl (meth) acrylates, such as 2-hydroxyethyl (meth) acrylate; Ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol Polyalkylene glycol mono (meth) acrylates such as mono (meth) acrylate; Caprolactone modified hydroxy (meth) acrylate etc. are mentioned. Examples of the polyol used as necessary include ethylene glycol, propylene glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,8-octanediol, 1,9-nonanediol, 1, Polyalkylene glycol, such as 10-decanediol and 1, 4- cyclohexanediol, etc. are mentioned. As a specific example of urethane (meth) acrylate, the reactant of diphenylmethane diisocyanate and ethylene glycol mono (meth) acrylate, the reactant of isophorone diisocyanate and 2-hydroxyethyl (meth) acrylate, for example. , Isocyanurate modified product of hexamethylene diisocyanate and polyethylene glycol mono (meth) acrylate, isocyanurate modified product of hexamethylene diisocyanate, polycaprolactone modified hydroxyethyl (meth) acrylate And reactants such as isocyanuric acid ethylene oxide modified di (meth) acrylate, isophorone diisocyanate or a multimer thereof and pentaerythritol polyfunctional (meth) acrylate.

Examples of the case where the formation of the double island-in-the-sea structure are promoted include three-component solubility parameter (SP value), glass transition temperature (Tg), surface tension, and molecular weight of the resin contained in the curable composition. have.

From the viewpoint of promoting the formation of the double islands-in-sea structure, the difference in solubility parameters (SP values) between the three components included in the curable composition is preferably 0.3 or more, more preferably 0.4 or more. SP value can be calculated | required by the method of Fedors, for example. The method is described in POLYMERENG INEERING AND SCIENCE, FEBRUARY, 1974, vol. 14, Issue 2, p. 147-154.

From the viewpoint of promoting the formation of the double islands structure, when the curable composition contains a polymer component, the glass transition temperature (Tg) of the polymer component is preferably 0 ° C or more. When Tg of the said polymer component is 0 degreeC or more, since formation of the said double islands structure effectively occurs from the said curable composition, the sticking prevention performance of the optical sheet obtained improves. Moreover, when two or more components of a polymer component are contained among the three components of the said curable composition, it is preferable that all the differences of the glass transition temperature (Tg) between these polymer components are all 10 degreeC or more, and it is more preferable that all are 20 degreeC or more. .

As a compounding ratio of the three components contained in the said curable composition, the mass ratio of the granular formation component based on the total amount of a granular formation component, a domain phase formation component, and a matrix formation component is 0.1 mass% or more and 10 mass% or less, and domain phase formation. It is preferable that the mass ratio of a component is 10 mass% or more and 50 mass% or less, and the mass ratio of a matrix-form component is 40 mass% or more and 89.9 mass% or less. Moreover, the mass ratio of the granular formation component is 0.1 mass% or more and 5 mass% or less, the mass ratio of the domain phase formation component is 12 mass% or more and 50 mass% or less, and the mass ratio of the matrix-forming component is 49.9 mass% or more and 87.9 mass% or less. Is more preferable. The mass ratio of the granular formation component is 0.1 mass% or more and 3 mass% or less, the mass ratio of the domain phase formation component is 20 mass% or more and 50 mass% or less, and the mass ratio of the matrix-forming component is 49.9 mass% or more and 79.9 mass% or less. desirable. Since the compounding ratio of the three components contained in the said curable composition which forms each phase of the said sticking prevention layer exists in the said range, the unevenness | corrugation of the sticking prevention layer surface is also effectively formed, and the sticking prevention performance of the optical sheet obtained further improves. do. Moreover, when one component is a monomer or an oligomer among the said three components, and the other one component is a monomer or oligomer which has a polar group, as a compounding ratio (mass ratio) of these components, the monomer which has a polar group with respect to the mass of a monomer or an oligomer component, or It is preferable that the mass ratio of an oligomer component is 1 or more, It is more preferable that it is 1.2 or more, It is especially preferable that it is 1.3 or more. In such a curable composition, phase separation occurs more effectively by two components, which are monomers or oligomers, and the unevenness of the surface of the anti-sticking layer is increased, so that the anti-sticking performance of the optical sheet is further improved.

The said curable composition may contain the solvent further from a viewpoint of making coating easy. As said solvent, For example, aromatic hydrocarbons, such as toluene and xylene; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; Alcohols such as methanol, ethanol, propanol, isopropanol and butanol; Ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, anisole, phentol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and propylene glycol monomethyl ether; Esters such as ethyl acetate, butyl acetate, isopropyl acetate and ethylene glycol diacetate; Amides such as dimethylformamide, diethylformamide and N-methylpyrrolidone; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; Halogenated hydrocarbons, such as dichloromethane and chloroform, etc. are mentioned. Among them, aromatic hydrocarbons, ketones, esters, alcohols and ethers are preferable in terms of solubility, and ketones are particularly preferable. These solvent can use 1 type or multiple types.

The curable composition may contain a polymerization initiator in order to cure when the component has an unsaturated double bond. As such a polymerization initiator, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2- Morpholinopropane-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane- Photoinitiators, such as 1-one; Azo-type, such as azobisisobutyronitrile, and peroxide-type thermal polymerization initiators, such as benzoyl peroxide, are mentioned. Moreover, the said curable composition may contain the hardening | curing agent, a catalyst, a photosensitizer, etc.

The optical layer 3 has a binder 5 and a light diffusing agent 6 dispersed in the binder 5. By dispersing the light diffusing agent 6 in the optical layer 3 in this manner, the light transmitted through the optical layer 3 from the rear surface side to the surface side can be uniformly diffused. Moreover, fine unevenness | corrugation is formed in the surface of the optical layer 3 substantially uniformly by the light-diffusion agent 6, and each recessed part and convex part of this fine unevenness | corrugation are formed in the lens shape. Due to the lenticular action of the fine concavities and convexities, the optical sheet 1 exhibits an excellent light diffusing function, and due to this light diffusing function, the refractive function and the transmitted light that refracts the transmitted light toward the normal direction are macroscopically in the normal direction. It also has a light condensing function.

The light diffusing agent 6 is a particle having a property of diffusing light, and classified into an inorganic filler and an organic filler. As the inorganic filler, specifically, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used. As a specific material of an organic filler, an acrylic resin, an acrylonitrile resin, a polyurethane, polyvinyl chloride, polystyrene, polyamide, polyacrylonitrile, etc. can be used. Especially, acrylic resin with high transparency is preferable, and polymethylmethacrylate (PMMA) is especially preferable.

The binder 5 is formed by hardening (crosslinking or the like) a polymer composition containing a base polymer. By this binder 5, the light-diffusion agent 6 is arrange | positioned and fixed by substantially equal density on the whole surface of the base material layer 2 surface. In addition, the polymer composition for forming the binder 5 may be, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, a UV absorber, an antioxidant, a viscosity modifier, a lubricant, A light stabilizer etc. may be mix | blended suitably.

Next, the manufacturing method of the said optical sheet 1 is demonstrated. Generally as a manufacturing method of the said optical sheet 1, (a) the process of manufacturing the coating liquid for optical layers by mixing the light-diffusion agent 6 with the polymer composition which comprises the binder 5, (b) Coating this optical layer coating liquid on the surface of the base material layer 2, laminating | stacking the optical layer 3, (c) manufacturing said curable composition for anti-sticking layer formation, (d) this sticking It has the process of forming a fine uneven | corrugated shape on this surface by laminating | stacking and hardening the sticking prevention layer 4 by coating the composition for prevention layer formation on the back surface of the base material layer 2.

Since the said optical sheet 1 has the fine concavo-convex shape of the said property on the whole surface of the sticking prevention layer, this smooth and evenly formed convex part sticks with the light guide plate etc. which are arrange | positioned and overlapped on the other surface side. Can be prevented and scratches on the surface of the light guide plate or the like can be prevented. Moreover, even if the said optical sheets 1 mutually rub each other by winding or overlapping with the said optical sheet 1 itself, it is prevented that they scratch or block.

Therefore, the lamp 21, the light guide plate 22, the light diffusion sheet 25, and the prism sheet 24 as shown in FIG. 2 (a) are provided, and the light rays generated from the lamp 21 are dispersed to provide a surface. In the backlight unit 20 for the liquid crystal display device which leads to the side, when the said optical sheet 1 is used as the light-diffusion sheet 24, the surface of the prism sheet 24 by the favorable scratch prevention property of the optical sheet 1 Scratches are reduced, and as a result, the occurrence of luminance unevenness due to the scratches is reduced, and the quality is improved.

In addition, the optical sheet of this invention is not limited to the said embodiment, For example, a prism sheet (refractive optical sheet), a microlens sheet, a polarizing sheet, a reflective polarizing sheet, a reflective sheet, a retardation sheet, a viewing magnification sheet It is also possible to provide the said sticking prevention layer in one surface of the optical sheet of another form, such as these. By the anti-sticking layer laminated | stacked on one surface (surface on the opposite side to an optical layer), an anti-scratching property and an anti-sticking property can be provided to various types of optical sheets.

[Example]

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

Synthesis Example 1 Synthesis of Unsaturated Double Bond-Containing Acrylic Copolymer (A-1)]

100 mass parts of propylene glycol monomethyl ethers were thrown into the 2 L reaction container provided with the stirrer, the thermometer, the nitrogen introduction pipe | tube, the cooler, and the dropping funnel, and it substituted at nitrogen, and heated at 110 degreeC. Next, a mixture consisting of 50 parts by mass of isobornyl methacrylate, 1 part by mass of methyl methacrylate and 3 parts by mass of methacrylic acid, 0.5 part by mass of t-butylperoxy-2-ethylhexanoate as a polymerization initiator and propylene The mixture which consists of 20 mass parts of glycol monomethyl ethers was dripped simultaneously, respectively over 3 hours. It was made to react at 110 degreeC further for 1 hour after completion | finish of dripping. Thereafter, a mixture of 0.1 part by mass of t-butylperoxy-2-ethylhexanoate and 5 parts by mass of propylene glycol monomethyl ether was added dropwise, followed by reaction at 110 ° C for 30 minutes.

4-hydroxybutyl acrylate glycidyl was added to the reaction mixture while bubbling air after adding a mixture consisting of 0.5 parts by mass of tetrabutylammonium bromide, 0.03 parts by mass of hydroquinone and 2 parts by mass of propylene glycol monomethyl ether. The mixture which consists of 7 mass parts of ethers, and 2 mass parts of propylene glycol monomethyl ethers was dripped over 1 hour, and also it was made to react for 5 hours. In this way, an unsaturated double bond containing acrylic copolymer (A-1) was obtained. The number average molecular weight of the unsaturated double bond containing acrylic copolymer (A-1) was 6000, the weight average molecular weight was 20000, SP value was 9.6, and Tg was 95 degreeC.

Synthesis Example 2 Synthesis of Acrylic Copolymer (A-2)

100 mass parts of propylene glycol monomethyl ethers were thrown into the 2 L reaction container provided with the stirrer, the thermometer, the nitrogen introduction pipe | tube, the cooler, and the dropping funnel, and it substituted at nitrogen, and heated at 110 degreeC. Next, a mixture consisting of 50 parts by mass of isobornyl methacrylate, 1 part by mass of methyl methacrylate and 3 parts by mass of methacrylic acid, 3 parts by mass of t-butylperoxy-2-ethylhexanoate as a polymerization initiator and propylene The mixture which consists of 20 mass parts of glycol monomethyl ethers was dripped simultaneously, respectively over 3 hours. After completion of the dropwise addition, the mixture was reacted at 110 ° C for 30 minutes. In this way, an acrylic copolymer (A-2) was obtained. As for the number average molecular weight of the acrylic copolymer (A-2), 3000, the weight average molecular weight were 5500, SP value was 10.1, and Tg was 117 degreeC.

Synthesis Example 3 [Synthesis of unsaturated double bond-containing acrylic copolymer (A-3)]

100 mass parts of propylene glycol monomethyl ethers were thrown into the 2 L reaction container provided with the stirrer, the thermometer, the nitrogen introduction pipe | tube, the cooler, and the dropping funnel, and it substituted at nitrogen, and heated at 110 degreeC. Next, a mixture consisting of 25 parts by mass of isobornyl methacrylate, 1 part by mass of methyl methacrylate, 25 parts by mass of ethylhexyl acrylate and 3 parts by mass of methacrylic acid, and t-butylperoxy-2-ethyl as a polymerization initiator The mixture which consists of 0.5 mass part of hexanoate and 20 mass parts of propylene glycol monomethyl ethers was dripped simultaneously over 3 hours, respectively. After completion of the dropwise addition, the mixture was reacted at 110 ° C for 1 hour. Thereafter, a mixture consisting of 0.1 parts by mass of t-butylperoxy-2-ethylhexanoate and 5 parts by mass of propylene glycol monomethyl ether was added dropwise thereto, followed by further reaction at 110 ° C for 30 minutes.

To the reaction mixture was added 5 parts by mass of glycidyl methacrylate and propylene while adding a mixture consisting of 0.5 parts by mass of tetrabutylammonium bromide, 0.03 parts by mass of hydroquinone and 2 parts by mass of propylene glycol monomethyl ether. The mixture which consists of 2 mass parts of glycol monomethyl ethers was dripped over 1 hour, and also it was made to react for 5 hours. In this way, an unsaturated double bond containing acrylic copolymer (A-3) was obtained. The number average molecular weight of the unsaturated double bond containing acrylic copolymer (A-3) was 4300, the weight average molecular weight was 9000, SP value was 10.1, and Tg was 6 degreeC.

Synthesis Example 4 [Synthesis of unsaturated double bond-containing acrylic copolymer (A-4)]

100 mass parts of propylene glycol monomethyl ethers were thrown into the 2 L reaction container provided with the stirrer, the thermometer, the nitrogen introduction pipe | tube, the cooler, and the dropping funnel, and after nitrogen-substituting, it heated at 110 degreeC. Next, a mixture consisting of 50 parts by mass of isobornyl methacrylate, 1 part by mass of methyl methacrylate, and 3 parts by mass of methacrylic acid, 0.5 part by mass of t-butylperoxy-2-ethylhexanoate as a polymerization initiator; The mixture of 20 mass parts of propylene glycol monomethyl ether was dripped over 3 hours simultaneously, respectively. After completion of the dropwise addition, the mixture was reacted at 110 ° C for 1 hour. Thereafter, a mixture consisting of 0.1 parts by mass of t-butylperoxy-2-ethylhexanoate and 5 parts by mass of propylene glycol monomethyl ether was added dropwise thereto, followed by further reaction at 110 ° C for 30 minutes.

To the reaction mixture, a mixture consisting of 0.5 parts by mass of tetrabutylammonium bromide, 0.03 parts by mass of hydroquinone and 2 parts by mass of propylene glycol monomethyl ether was added, and 5 parts by mass of glycidyl methacrylate and propylene glycol while bubbling air. After the mixture which consists of 2 mass parts of monomethyl ethers was dripped over 1 hour, it was made to react further for 5 hours. In this way, an unsaturated double bond containing acrylic copolymer (A-4) was obtained. The number average molecular weight of the unsaturated double bond containing acrylic copolymer (A-4) was 1700, the weight average molecular weight was 2500, SP value was 10.4, and Tg was 121 degreeC.

Synthesis Example 5 Synthesis of Urethane Acrylate (C-1)

Isocyanurate-modified product of hexamethylene diisocyanate (Takeda Akhin Kogyo Co., Ltd. "Takenate D-170N": 2 isocyanate group (-NCO) content in 2L reaction vessel equipped with a stirrer, a thermometer and a cooler): 20.9 Mass%) 50 parts by mass, polyethylene glycol monoacrylate ("Blemmer AE-150" manufactured by Nippon Oil Industries, Ltd .: hydroxyl value 264 mgKOH / g, ethylene oxide equivalent repeat unit number: 3.4) 42 parts by mass, dibutyltin 0.02 mass part of laurate and 0.02 mass part of hydroquinone monomethyl ether were thrown in, and reaction was performed at 70 degreeC for 5 hours. In this way, urethane acrylate (C-1) was obtained.

Synthesis Example 6 Synthesis of Urethane Acrylate (C-2)

50 parts by mass of toluene and 50 parts by mass of isocyanurate-modified type ("Takenate D-170N" manufactured by Takeda Akuhin Kogyo Co., Ltd.) 63 mass parts of polycaprolactone modified hydroxyethyl acrylate ("Flacel FA1" by Daicel Kagaku Kogyo Co., Ltd.), 0.02 mass part of dibutyltin laurate, and 0.02 mass part of hydroquinone monomethyl ether, Reaction was performed at 70 degreeC for 5 hours. Then, 63 mass parts of toluene was added and the urethane acrylate (C-2) of 50 mass% of solid content was obtained. The repeating number of caprolactone units per acrylate monomer residue in urethane acrylate (C-2) is 1.

Synthesis Example 7 Synthesis of Urethane Acrylate (C-3)

50 parts by mass of toluene and 4.2 parts by mass of stearyl alcohol (NAA-46, manufactured by Nippon Oil Chemical Co., Ltd., hydroxyl value: 207) were added to a 2L reaction vessel equipped with a stirrer, a thermometer, and a cooler. Stearyl alcohol was completely dissolved. Next, 50 mass parts of isocyanurate-modified types of hexamethylene diisocyanate (Takeda Akihin Kogyo Co., Ltd. "Takenate D-170N") were added, and it was made to react at 70 degreeC for 30 minutes. Further, caprolactone-modified hydroxyethyl acrylate (179 parts by mass of "Flacel FA5" manufactured by Daicel Kagaku Kogyo KK, 0.02 parts by mass of dibutyltin laurate and 0.02 parts by mass of hydroquinone monomethyl ether were added thereto, and 70 ° C. 118 parts by mass of toluene was added to obtain a urethane acrylate (C-3) having a solid content of 50% by mass of the caprolactone unit per acrylate monomer residue in the urethane acrylate (C-3). The number of repetitions is three.

Example 1

100 parts by mass of a binder resin compound ("Bylon" of Toyo Boseki Co., Ltd.) which uses polyester polyol as a base polymer, and "PL-1 of colloidal silica (Fusokagaku Kogyo Co., Ltd.) whose average particle diameter is 20 nm. In a polymer composition containing 50 parts by mass, 5 parts by mass of a curing agent (`` Cornate HX '' of Nippon Polyurethane Co., Ltd.) and a light stabilizer (`` PUVA-1033 '' of Otsuka Kagaku Co., Ltd.) 50 mass parts of acrylic resin beads ("MBX-15" of Sekisui Kasehin Kogyo) of 15 micrometers of average particle diameters are mixed, and a coating liquid is produced and this coating liquid is made of the transparent polyester of thickness 100micrometer by the roll coating method. 15 g / m <^2> (solid content conversion) was applied to the surface of the base material layer ("A-4300" of Toyo Boseki Co., Ltd.), and the optical layer was formed by hardening.

Moreover, the solution containing 0.6 mass part of unsaturated double bond containing acrylic copolymers (A-1) of the synthesis example 1, and 41.9 mass parts of pentaerythritol triacrylate (B-1) which is a polyfunctional unsaturated double bond containing monomer is synthesize | combined. 57.7 parts by mass of the urethane acrylate (C-1) of Example 5, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one which is a photoinitiator ("IRGACURE 907" made by Chiba Corporation) ) By dropping into a solution containing 7 parts by mass and 3 parts by mass of 1-hydroxycyclohexyl-phenyl ketone ("IRGACURE 184" manufactured by Chiba-Geigy Co., Ltd.), to obtain methyl ethyl ketone (MEK) and methyl isobutyl ketone In the mixed solvent (mixing ratio: MEK / MIBK = 1: 1 mass ratio), the coating liquid containing three components of a matrix forming component, a domain forming component, and a granular forming component so that a non-volatile component ratio may be 50 mass% is carried out. Made. ² g / m <^2> (solid content conversion) was applied to the back surface of the said base material layer by the roll coating method, and it hardened by UV irradiation, and the sticking prevention layer of 2.8 micrometers of average thickness was formed. This obtained the optical sheet of Example 1.

EXAMPLES 2-8

Coating liquid for sticking prevention layer formation similarly to Example 1 except having used the acrylic copolymer which is a granular formation component as described in Table 1, a domain formation component, and a matrix formation component in each compounding quantity. Except for producing and using, in the same manner as in Example 1, an optical sheet according to each example was obtained. In Example 7, urethane acrylate (C-2) and urethane acrylate (C-3) were used together as a matrix-forming component by mixing ratio (C-2 / C-3) = 3/1 (mass ratio). In Example 8, methyl methacrylate (C-4) was used as the matrix forming component.

Comparative Example 1

In Example 1, it carried out similarly to Example 1 except having not mix | blended the urethane acrylate (C-1) which is a matrix form component at the time of preparation of the coating solution for sticking prevention layer formation, An optical sheet was obtained.

Comparative Example 2

100 parts by mass of a binder resin compound ("Bylon" of Toyo Boseki Co., Ltd.) which uses polyester polyol as a base polymer, and "PL-1 of colloidal silica (Fusokagaku Kogyo Co., Ltd.) whose average particle diameter is 20 nm. ) In a polymer composition containing 50 parts by mass, 5 parts by mass of a curing agent (`` Cornate HX '' of Nippon Polyurethane Co., Ltd.) and 5 parts by mass of a light stabilizer (`` PUVA-1033 '' of Otsuka Kagaku Co., Ltd.) 10 mass parts of acrylic resin beads ("MBX-5" of Sekisui Kasehin Kogyo) of an average particle diameter are mixed, a coating liquid is produced, and this coating liquid is rolled on the back surface of the said base material layer by 2 g / m. ² (solid content conversion) It carried out similarly to Example 1 except having formed the sticking prevention layer by coating and hardening, and obtained the optical sheet of the comparative example 2 whose average thickness of a sticking prevention layer is 3.0 micrometers.

(Evaluation of characteristics)

Using the optical sheets of Examples 1 to 8 and Comparative Examples 1 and 2, the resin phase separation structure on the surface of the anti-sticking layer was observed, and the arithmetic mean roughness (Ra) of the surface properties and the average length (RSm) of the roughness curve elements were measured. , 10-point average roughness (Rz), square root mean square roughness (Rq), and pencil hardness, and also the frontal luminance when these optical sheets are placed in the backlight unit, and the effects on other optical sheets ( Adhesion, occurrence of interference fringes, and occurrence of scratches) were evaluated. The results are shown in Table 1 below.

The resin phase separation structure on the surface of the anti-sticking layer was observed with an electron microscope and evaluated from the following viewpoints.

A: Formation of the double islands structure (matrix phase, domain phase, granular phase) was confirmed.

B: Double islands-in-sea structure (matrix phase-domain phase-granular phase) formation was not confirmed.

The arithmetic mean roughness (Ra) and the ten-point average roughness (Rz) of the surface properties are in accordance with JIS B0601-1994, and the "average length (RSm) of roughness curve elements" and "square root mean square roughness (Rq)". According to JIS B0601-2001, cut-off (lambda) c was 2.5 mm and evaluation length was 12.5 mm, and it measured using the stylus type surface roughness measuring instrument "surfcomb 470A" made by Tokyo Semit. "Pencil hardness" was measured according to the test method 8.4 of JIS K5400.

In addition, the front brightness when the optical sheet is inserted into the backlight unit, and the quality of the liquid crystal display screen which the optical sheet exerts, actually put these optical sheets into the edge light type backlight unit (as an optical sheet on the surface of the light guide plate). The prism sheet H505 manufactured by K and the laminated material and the optical sheet (the light diffusing sheet) of the example or the comparative example laminated on this surface were used.), The front luminance, the adhesion with the prism sheet, and the generation of the interference fringes Confirmed.

The adhesiveness with a prism sheet evaluated the adhesiveness after leaving for 48 hours in the state of 40 degreeC of air temperature and 90% of humidity from the following viewpoint.

◎: not in close contact

○: Some parts are in close contact

△: adhered to some extent

X: Strongly adhered.

The generation of interference fringes was visually evaluated from the following point of view.

◎: no interference fringes at all

○: you can see a little interference stripes

△: Interference fringes can be confirmed without looking

X: An interference fringe can be confirmed reliably.

The occurrence of scratches was observed by microscopic observation of the presence or absence of scratches on the prism portion after rubbing the anti-sticking layer of these optical sheets and the surface (surface on the prism portion side) of KAI Co., Ltd. prism sheet H505 100 times. Rated in terms of.

◎: no scratch is observed at all

○: slight scratches observed

△: scratches are observed

X: Scratches are clearly observed.

As shown in Table 1, the optical sheets of Examples 1 to 8 have high front luminance when inserted into the backlight unit, suppress the adhesion of other optical sheets and the generation of interference fringes, and further, the other optical sheets. It is understood that scratches on the surface are reduced.

EXAMPLES 9-16

In Example 1, the compounding quantity of the unsaturated double bond containing acrylic copolymer (A-1), pentaerythritol triacrylate (B-1), and urethane acrylate (C-1) which are components of the coating solution for anti-sticking layers is As shown in Table 2 below, except that the non-volatile content rate of the coating solution for anti-sticking layer was 60% by mass, and the average thickness of the anti-sticking layer to be formed was 2 µm. In the same manner, optical sheets of Examples 9 to 16 were obtained.

[Evaluation of Characteristics]

Formation of the double islands structure on the surface of the sticking prevention layer was confirmed by the said electron microscope observation about all the optical sheets of the obtained Examples 9-16. In addition, as described above, the arithmetic mean roughness Ra of the surface properties, the average length RSm of the roughness curve element, the ten-point average roughness Rz, the square root mean square roughness Rq, and the pencil hardness were measured. The front brightness when these optical sheets were put into a backlight unit, and the influence (adhesiveness, generation | occurrence | production of an interference fringe, a flaw) of other optical sheets which an optical sheet exerts were evaluated according to the said evaluation criteria. In addition, they measured the average height of a styryl each convex portion of the king-layer surface (h), an average protrusion diameter (r _1), an average diameter (r _2), and the existence density. The laser microscope "VK-8500" (made by Keyence Corporation) was used for the measurement about each convex part. The results are shown in Table 2 below.

From the results in Table 2, by changing the compounding amount ratio of the components forming the optical sheet, the surface properties of the anti-sticking layer can be adjusted while maintaining high front brightness and anti-scratching properties, and are designed in accordance with other optical sheets to be laminated. By doing so, it has been suggested that the adhesion prevention properties and the like can be further improved.

As mentioned above, the optical sheet of this invention is useful as a component of the backlight unit of a liquid crystal display device, and can be especially used suitably for a transmissive liquid crystal display device.

1 optical sheet 2 base layer
3 Optical layer 4 Anti-sticking layer
5 Binder 6 Light Diffusion
7 fine uneven shape

Claims (5)

A transparent base material layer, the optical layer laminated | stacked on one surface side of this base material layer, and the sticking prevention layer laminated | stacked on the other surface side of a base material layer, and this sticking prevention layer has the fine uneven | corrugated shape in the whole surface of a surface As a sheet,
The said sheet | seat prevention layer consists of a plurality of types of resin from which phase separation is carried out, and has a double-island structure in which a domain phase is disperse | distributed in a matrix phase, and a granular phase is disperse | distributed in a domain phase. The optical sheet according to claim 1, wherein the main material in the matrix phase of the anti-sticking layer is a urethane (meth) acrylate resin, a domain main material is a (meth) acrylic resin, and a granular material is a (meth) acrylic resin. . The optical sheet according to claim 1, wherein convex portions are formed scattered on the surface of the anti-sticking layer by granular images dispersed. The thickness of the said anti-sticking layer is 0.5 micrometer or more and 4 micrometers or less,
The arithmetic mean roughness Ra of the surface of the said sticking prevention layer is 0.03 micrometer or more and 0.3 micrometer or less, and the average length RSm of a roughness curve element is 40 micrometers or more and 400 micrometers or less. In the backlight unit for a liquid crystal display device which disperse | distributes the light ray emitted from a lamp and guides it to the surface side,
The optical sheet of Claim 1 is provided, The backlight unit for liquid crystal display devices characterized by the above-mentioned.

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