JP2012018330A - Optical sheet - Google Patents

Abstract

An optical sheet which prevents optical adhesion on a back surface side opposite to a prism surface side by microprotrusions on the surface of a concavo-convex coating film containing microparticles, and prevents damage from microprotrusions and dropping off of microparticles. Furthermore, optical adhesion on the prism surface side is also improved.
In an optical sheet, a prism group in which columnar unit prisms 1 are arranged in parallel with each other in a ridge line is provided on one surface 2p of a sheet-like main body 2, and a projection height H is formed on the other surface 2q. It has the uneven | corrugated coating film 3 by which the micro processus | protrusion 4 whose average is 0.38 micrometer or more was formed in the surface. In addition, the concavo-convex coating film includes spherical particles 3b for forming the fine protrusions 4 in the binder resin 3a, and further includes a lubricant such as polyether-modified dimethylpolysiloxane. Optical contact on the prism surface side can be improved by changing the height of the ridge line of the columnar unit prism (interval from the main body portion) to a polygonal line shape without making it constant.
[Selection] Figure 1

Description

  The present invention relates to an optical sheet that changes the traveling direction of light. In particular, the present invention relates to an optical sheet that can prevent other optical members due to fine protrusions generated on the surface of the coating layer to prevent optical adhesion of the surface opposite to the prism surface side, and defects such as scratches on the optical sheet.

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, Patent Document 1 discloses an optical sheet in which a large number of minute projections for gap formation whose height is not less than the wavelength of the light source light and not more than 100 μm are arranged on the back surface opposite to the prism surface on which triangular prism unit prisms are arranged. Has been. By providing such a group of minute protrusions without making the back surface a mere smooth surface, when the light guide plate is disposed adjacent to the back surface of the optical sheet, optical contact with the light guide plate is prevented, and the optical contact It is possible to effectively prevent in-plane brightness non-uniformity, interference fringes, and the like.

In addition, such a microprojection group includes a heat embossing method, a molding method using a UV or electron beam curable resin liquid and a molding die (2P method: photopolymer method), and a paint containing fine particles in the resin liquid. It can be formed by a coating method in which irregularities due to fine particles appear on the surface of the coating. 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.
Here, an example of an optical sheet having fine protrusions formed by a coating method is shown in the cross-sectional view of FIG. In the optical sheet 60 of FIG. 6, a prism group in which a large number of triangular prism unit prisms 61 are arranged is formed on one surface of the main body 62, and fine particles 63b in the binder resin 63a are formed on the other surface (back surface) of the main body 62. A concavo-convex coating 63 is formed. And the surface of the uneven | corrugated coating film 63 is the structure by which the microprotrusion 64 is formed in the part of the fine particle 63b.

However, although the optical contact can be prevented by the minute protrusion 64, the surface of another optical member such as a light guide plate in contact with the minute protrusion 64 may be damaged. That is, the optical sheet 60 and another optical member disposed adjacent to the back surface of the optical sheet 60 on the microprojection 64 side are used in a state where the microprojections 64 are in contact with each other. This is because an external force is applied to a contact portion close to a point contact due to thermal deformation such as warping or deflection due to a change in environmental temperature during transportation or movement, and stress concentrates on the portion of the minute protrusion 64.
In addition, the fine particles 63b inside the uneven coating 63 may fall off the coating film, and the dropped fine particles may damage other adjacent optical members or themselves.
Therefore, Patent Document 2 discloses a technique in which fine particles to be contained in the coating film are spherical beads having a half-value width of 1 μm or less in order to prevent such scratches.

Japanese Patent No. 3518554 Japanese Patent No. 3913870

However, even when spherical particles having a monodispersed particle size distribution as disclosed in Patent Document 2 are used as the fine particles to be contained in the coating film, it is not sufficient to prevent the optical member from being damaged.
Moreover, even if various problems related to optical contact between the back surface, which is the non-prism side surface of the optical sheet, and other optical members can be solved by Patent Document 1 and Patent Document 2, the problem due to optical contact on the prism surface side is also solved. The need to do so has increased. In particular, in recent years, the light diffusing sheet that has been conventionally arranged as a standard is omitted between the optical sheet and the liquid crystal panel in order to reduce the cost and reduce the thickness, and the optical sheet and the liquid crystal panel are disposed adjacent to each other. This is because a configuration has been desired. For this reason, even between the prism surface of the optical sheet and the back surface of the liquid crystal panel, appearance defects such as interference fringes and light / dark unevenness (wet-out, wet-out) occur due to water contact. It has become necessary to solve this.

That is, an object of the present invention is to provide an optical sheet having a configuration in which optical adhesion is prevented by a microprotrusion generated on the surface of a concavo-convex coating film containing fine particles on the back surface side opposite to the prism surface side. It is to prevent the damaged particles from falling off other optical members.
Moreover, the subject of this invention is preventing the appearance defect generation | occurrence | production by optical contact | adherence by the prism surface side further.

The optical sheet according to the present invention is
(1) A prism group formed by arranging columnar unit prisms in parallel with each other in ridges is provided on one surface of a sheet-like main body, and a minute protrusion is formed on the other surface of the main body. An optical sheet having an uneven coating film,
The average value of the protrusion height H of the fine protrusions is 0.38 μm or more, and the uneven coating film contains spherical particles for forming the fine protrusions in the binder resin and a lubricant.
(2) Further, in the configuration of (1), the lubricant is a polyether-modified dimethylpolysiloxane.

(3) Also, in the configuration of (1) or (2), when the columnar unit prisms are observed from a direction parallel to the arrangement direction, each columnar unit prism has a polygonal outer contour that forms irregularities. A plurality of convex portions defined by the polygonal outer contour of one columnar unit prism, and one of the main body portions between the top portion of each convex portion and the main body portion farthest from the main body portion The interval along the normal direction set up on the surface of the surface is not constant.

According to the present invention, the lubricant contained in the binder resin of the concavo-convex coating film for generating the microprotrusions causes the other optical member due to the microprotrusions and the spherical surface for generating microprotrusions. Prevents particles from falling off the uneven coating. Moreover, the use of polyether-modified dimethylpolysiloxane as a lubricant can more effectively prevent the scratches and dropout.
Also, by assuming that the height of the ridge line of the columnar unit prism is not constant, the optical diffusion between the prism surface side of the optical sheet and the liquid crystal panel can be omitted even if the light diffusion sheet between the liquid crystal panel is omitted. Appearance defects such as interference fringes and light oozing caused by adhesion can be prevented. As a result, the cost of the display can be reduced and the thickness can be reduced.

The perspective view (a) explaining one Embodiment of the optical sheet by this invention, and sectional drawing (b) explaining the protrusion height H of a microprotrusion. The perspective view explaining another embodiment (prism ridgeline height variable) of the optical sheet by this invention. Sectional drawing in a surface parallel to YZ surface containing the ridgeline of this prism when the optical sheet of FIG. 2 is observed from the arrangement direction (X-axis direction) of columnar unit prisms. Explanatory drawing which shows the measuring apparatus of the performance with a damage resistance. Sectional drawing which shows the structure of an edge light type back light source device when observing the appearance defect appearance condition by a damage. Sectional drawing which shows an example of the optical sheet which has a microprotrusion on the back surface of the past.

  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] Overview:
First, an optical sheet according to an embodiment of the present invention is shown in the perspective view of FIG. In the optical sheet 10 shown in the figure, a prism group in which a large number of columnar unit prisms 1 are arranged in parallel with each other in the ridge line direction is arranged on one surface 2p of the sheet-like main body portion 2 (surface on the upper side in the drawing). And an uneven coating film 3 is formed on the other surface 2q of the main body 2, and the uneven coating film 3 has a microprojection 4 on its surface. This uneven | corrugated coating film 3 contains the spherical particle 3b in binder resin 3a. Further, the uneven coating film 3 is formed with a film thickness such that a convex portion is formed on the surface of the portion where the spherical particles 3 b are present, and the convex portion is a minute protrusion 4. As shown in the cross-sectional view of FIG. 1B, the protrusion height H of the microprojections 4 is different from the height of the top of the microprojections 4 from the coating surface of the uneven coating film 3 where the microprojections 4 do not exist. (Z-axis direction in the drawing). And the average value of the protrusion height H of this microprotrusion 4 is more than the wavelength by the side of the short wavelength of visible light, ie, 0.38 micrometer or more. When the thickness is 0.38 μm or more, optical adhesion can be prevented over the entire visible light wavelength range.
The protrusion height H is measured by using a stylus type surface roughness meter when the density of the microprojections 4 is relatively dense and can be measured and evaluated with a stylus type surface roughness meter. With respect to the surface of the coating film 3, the ten-point average roughness Rz defined in JIS B0601: 1994 version is measured, and the protrusion height H is determined by this Rz value.
Further, when the density of the microprojections 4 is relatively sparse and measurement or evaluation with a stylus type surface roughness meter is impossible or difficult, the normal line nd of the optical sheet 10 (in FIG. 1A) The section cut along the plane including the Z axis) is observed with a microscope, and the height H of each microprotrusion 4 is directly read (see FIG. 1B). Then, the projection height H is obtained by averaging three or more, preferably about ten, data of the height H of each microprojection 4.

  In FIG. 1A, the X, Y, and Z axes of the orthogonal coordinate system are parallel to the arrangement direction of the columnar unit prisms 1, the Y axis is parallel to the ridge line direction of the columnar unit prisms 1, and the Z axis Is parallel to the thickness direction of the main body 2 and the thickness direction of the uneven coating film 3. Further, the cross-sectional view of FIG. 1B for explaining the protrusion height H is a cross-sectional view of an arbitrary plane parallel to the Z-axis.

Furthermore, the uneven coating film 3 contains a lubricant in the binder resin 3a.
By containing a lubricant, when the tops of the microprotrusions 4 are in physical contact with the surfaces of the other optical members, the contact surfaces can be easily slid between each other to prevent the contact between the contact surfaces. Scratches on the surface are prevented. At the same time, it is possible to prevent the spherical particles 3b existing immediately below the microprojections 4 from falling off due to the coating film of the microprojections 4 being broken from the contact surface portion.

  In addition, as well shown in FIG. 1B, which is an enlarged cross-sectional view of the microprojection 4, the spherical particles 3b contained in the binder resin 3a are separated from the coating film surface in the microprojection 4 portion. It is not exposed and is covered with the binder resin 3a in the coating film. Although there may be uncoated spherical particles 3b in a part of the microprojections 4 present in large numbers on the coating film surface, the majority, more preferably all the microprojections 4 are present in the coating film. It is preferable to be coated with the binder resin 3a. By covering the spherical particles 3b with the binder resin 3a in the coating film, the surface of the fine protrusions 4 becomes the surface of the binder resin 3a containing the lubricant, and the lubricant can be effectively applied. This is because the lubricant contained in the concavo-convex coating film 3 is constituted by the binder resin 3a and is contained in a matrix for dispersing and holding the spherical particles 3b. For this reason, when the microprotrusions 4 are coated with the binder resin 3a, the surface of the microprotrusions 4 becomes a surface made of the binder resin 3a containing the lubricant, and the effect of the lubricant can be maximized. .

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

“One surface 2p” is a surface on the side where the columnar unit prisms 1 of the main body 2 are arranged. In addition, the “one surface 2p” side of the optical sheet 10 is referred to as a “prism surface side”. The “one surface 2p” is a virtual surface that does not actually exist as the outermost surface or the interface surface when the prism unit is filled with the columnar unit prisms 1 arranged without gaps. Further, “one surface 2p” means that when the columnar unit prisms 1 are arranged with a gap therebetween to form a prism group, the prism group has the gap and the one surface 2p is partially formed by the gap. It becomes an exposed real surface.
When the optical sheet 10 is used with the “prism surface side” as the “light output side”, the “prism surface side” is the “observer side”.
The “main cut surface” refers to the columnar unit prism 1 in the arrangement direction of the columnar unit prisms 1 in a cross section parallel to the normal line nd (see FIG. 3) standing on the “one surface 2p” of the main body 2. Also refers to a parallel cross section. In other words, the cross section is parallel to the normal line nd and orthogonal to the ridge line of the columnar unit prism 1. In FIG. 1A, the Z axis is parallel to the normal nd.
The “projection height H” is defined by referring to FIG. 1 (b), and the top of the microprojection 4 is defined by using the surface of the uneven coating film 3 where the microprojection 4 does not exist as a reference plane. It is the protruding height. “Smooth” means smooth in an optical sense. That is, it means the degree that a certain proportion of visible light is refracted while satisfying Snell's law on the surface of the optical sheet 10. Therefore, for example, if the ten-point average roughness Rz (JISB0601: 1994 version) of the other surface 2q of the main body 2 is less than the shortest visible light wavelength (0.38 μm), it is sufficiently smooth.
Terms that specify shape and geometric conditions, such as “triangle”, “circular”, “elliptical”, “parallel”, “orthogonal”, “polyline”, etc., are not bound to a strict meaning. These terms are interpreted to include errors, tolerances, or equivalent ranges to the extent that similar optical functions can be expected, including limitations in manufacturing technology and errors during molding.

[C] Details of each layer:
Hereinafter, each layer will be further described.

(Columnar unit prism)
The columnar unit prism 1 is typically a triangular unit prism whose main cut surface has a base on the main body 2 side. As such a columnar unit prism 1, conventionally known various prisms can be appropriately employed. Further, the main cut surface shape may include a shape having only a curved line and a shape having only a curved line (for example, a part of a circle or an ellipse) in addition to a shape consisting only of a straight line such as a triangle.
In addition, when a main cut surface shape is a part of a circle or an ellipse, it can also be called a lens, and the columnar unit prism 1 in the present invention may include a so-called columnar unit lens.

  In addition, the columnar unit prisms 1 may be arranged such that one or more of the shapes and dimensions of the arranged columnar unit prisms 1 are different from each other in addition to the same shape and size, and may be irregularly different. Further, the arrangement of the columnar unit prisms 1 may be different from the regular arrangement in the same arrangement period, may be different in the arrangement period, or may be irregularly different.

(Ridge height variable shape)
Further, as the columnar unit prism 1, as in the optical sheet 10 illustrated in the perspective view of FIG. 2, the height of the ridge line is changed to a polygonal line shape and the shape is not constant. This is a preferred form in that it can prevent various problems caused by optical adhesion.
FIG. 3 is a diagram illustrating the shape of the outer contour of the ridge line when the columnar unit prism 1 illustrated in the perspective view of FIG. 2 is viewed from a direction parallel to the arrangement direction (X-axis direction).
The columnar unit prism 1 illustrated in the perspective view of FIG. 2 is viewed from the direction (Z-axis direction) perpendicular to the extending direction, that is, the ridge line direction and the arrangement direction, in other words, one surface of the main body 2. When viewed from the normal nd direction set at 2p, the ridge line is a straight line parallel to the Y axis. Therefore, the columnar unit prism 1 of the optical sheet 10 illustrated in FIG. 2 has an YZ plane including the entire length of the ridgeline, and is an external view viewed from the arrangement direction (X-axis direction) showing the height change of the ridgeline. As a cross-sectional view taken along the YZ plane, it is also possible to adopt. Therefore, in FIG. 3, it is drawn as a cross-sectional view on the YZ plane. 3 is a cross-sectional view of the columnar unit prism 1 viewed from the arrangement direction (X direction), and is a plane parallel to the normal direction nd of the one surface 2p of the main body 2 and the ridgeline direction of the columnar unit prism 1. 2 is a cross-sectional view taken along a plane including the ridge line of the columnar unit prism 1.

In FIG. 3, the ridge line of the columnar unit prism 1 is composed of a broken line group in which broken lines such as the ridge line Lu _i and the ridge line Lu _{i + 1} are connected for each unit section L _i , L _{i + 1} . In this way, as a result of the ridge line being a broken line on the YZ plane, the ridge line has a plurality of top portions P _i and top portions P _{i + 1} .
In addition, i is an integer starting from 1, and is a number obtained by numbering the tops of the ridgelines of any one columnar unit prism 1 from the first in order from the end. In addition, when subscripts i, i + 1, etc. are not added, what is common to each individual element (top, ridge line, etc.) with a subscript will be described.

Then, the top P _i, In the figure, which is an intersection with a line segment Lu _i right-up, the line segment Ld _i downward sloping connecting the right end of the line segment Lu _i of the right-up. Further, the left end of the line segment Lu _{i that} rises to the right is connected to the line segment Ld _i-1 that falls to the right that belongs to the adjacent unit section, and the intersection is the ridge C _i . Similarly, the right end of the right-down line segment Ld _i is connected to the right-up line segment Lu _{i + 1} belonging to the next unit section, and the intersection is the ridge part C _{i + 1} . In the figure, a line segment Lu _{i + 1} that rises to the right is a line segment group that is composed of two continuous straight line segments and is a broken line.
The saddle C _i and the line segment Lb _i which connects the saddle C _{i + 1,} and the line segment Lu _i upward sloping connecting to該鞍section C _i, segment of the right up Lu _i and the saddle C _{i The} portion surrounded by the lower right line segment Ld _i connected to ₊₁ forms a polygon (in the figure, a triangle), and this defines one convex portion T _i ( In order to make it easy to understand in the drawing, halftone dots are hatched only on the convex portions T _i ). Then, right adjacent to the convex portion T _i is the next protrusion T _{i + 1.}

Further, in the case of the figure, the line segment Lu _{i + 1} that rises to the right belonging to the convex portion T _{i + 1} is a line segment group that is composed of two continuous line segments and is itself a broken line, The line segment Lu that rises to the right and the line segment Ld that descends to the right may be a line segment group in which a plurality of line segments (straight lines) are connected in addition to a line segment composed of only one straight line. Note that the line segment Lu _{i + 1} that rises to the right of the convex portion T _{i + 1} in the figure is a line segment group in which two straight lines are connected, and thus the outer shape of the convex portion T _{i + 1} is a quadrangle.

Further, as indicated by the top part P _i and the top part P _{i + 1} , the distance d _i and the distance d _{i +} from the one surface 2p of the main body part 2 of the top part P _i and the top part P _{i + 1} that are adjacent to each other. ₁ is not equal. In other words, the “height” of the apex P from the one surface 2p is not constant. That is, the distance d can be said to be the “height” of the top portion P. In the case of the figure, the top P _{i + 1} having a larger distance d relative to the top P _i, becomes as contact with the surface of the other optical members 20. (Strictly speaking, it is when there is no compression deformation of the top P _{i + 1} )

The plurality of apexes P included in one columnar unit prism 1 are at least (in the ridge line direction) adjacent to each other in that problems due to optical contact with other optical members 20 on the prism surface side of the optical sheet 10 are also prevented. It is preferable that the intervals d are not the same between the tops P to be performed. In FIG. 3, it is preferable that the interval p _i and the interval d _{i + 1} are different between the apex P _i and the apex P _{i + 1} . Furthermore, it is more preferable that the intervals d of all the top portions P included in one columnar unit prism 1 are all different from each other.

  Moreover, as shown in the perspective view of FIG. 2, it is preferable that the respective top portions P in the ridge lines of the adjacent columnar unit prisms 1 are not located at the same position (the same Y coordinate) in the extending direction of the ridge lines. In other words, it is preferable that the apexes P in the ridge lines of the adjacent columnar unit prisms 1 are arranged so as not to line up in the arrangement direction of the columnar unit prisms 1. In this way, when the optical sheet 10 is disposed adjacent to another optical member 20 such as another optical sheet or a light guide plate, the contact with the other optical member 20 is observed when observing a transmission type display device or the like. And you can prevent it from standing out.

Note that the height (interval d) of the ridge lines of the columnar unit prism 1 is an example of changing into a polygonal line formed of a line segment group in which only straight lines are connected in the examples of FIGS. As a result, when the prism surface side is arranged adjacent to the smooth surface of another optical member, linear adhesion over a long region at the ridge line portion (which may occur in a columnar unit prism having a constant ridge line height) Does not occur. For this reason, generation | occurrence | production of the various malfunction resulting from the optical contact | adherence with the other optical member 20 can be suppressed significantly.
In addition, since the heights (intervals d) of the apex portions P of the ridge lines are not all the same, when arranged adjacent to the other optical member 20, the other optical member 20 has a height of the apex portion P. A part of the high apex P contacts. The contact is point-like or only a linear region in consideration of shape deformation due to pressure at the time of contact. When the contact pressure increases due to warping or bending / deformation due to external force of the optical sheet 10 or another optical member 20 disposed adjacent thereto, the top portion P that is not yet in contact has a high height. Also, it comes into contact with the other optical member 20. In this way, even if there is an increase in the contact pressure between the optical sheet 10 and the other optical member 20 disposed adjacent thereto, the pressure is dispersed by the newly generated contact region, and the contact with the other optical member 20 is achieved. It is possible to effectively prevent problems caused by.

  Although the height (interval d) of the ridge lines is not constant, in the optical sheet 10 illustrated in FIGS. 2 and 3, the ridge lines extend linearly in a plan view (projection onto the XY plane). Accordingly, the main cut surface shape of the columnar unit prism 1 is an isosceles triangle having the same shape in any part on the ridge line except for the part close to the main body 2 and the side including the ridge line. . For this reason, the optical effect is the same over the extending direction of the ridgeline. Therefore, the apex portion P having a different height generated by changing the height of the ridge line into a broken line shape without making the ridge line constant does not cause a new appearance defect.

  By the way, in order to manufacture a prism group in which the columnar unit prisms 1 having the ridgeline height changed to a polygonal line are arranged in this way, for example, a cylinder-like structure conventionally used for manufacturing this kind of prism group ( When producing a (cylindrical) mold with a cutting bit, it can be easily manufactured by cutting while changing the cutting depth of the cutting bit into a polygonal line.

(Specific examples of dimensions and distribution)
Here, if the specific example of the dimension of the columnar unit prism 1 and the prism group which consists of it is shown, the width | variety of the bottom face of the columnar unit prism 1 (dimension in a prism arrangement direction) will be 10-500 micrometers, and the space | interval d (height of the top part P). ) Is 5 to 100 μm, and when the main cut surface shape is an isosceles triangle, the apex angle forming the ridge line is 80 to 110 °, preferably 90 °. Furthermore, when not all the intervals d of the top portions P are the same, the amplitude (height difference) that is the difference between the maximum value and the minimum value of the intervals d of the top portions P is preferably 1 to 10 μm as an example. In addition, the distance between the adjacent apexes P in the extending direction of the ridge line is within a range of 70 to 900 mm as an example in consideration of restrictions on mold manufacturing such as depth control of cutting tools and an effect of preventing optical adhesion. For example, it is variable.

[Main body]
As the main body 2, 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. .
Although the main body 2 is “sheet-like”, the term “sheet” 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 2 is 25 μm to 5 mm or the like.
In addition, the other surface 2q of the main body 2 is a surface on which the uneven coating film 3 is formed, and is usually a smooth surface. However, the other surface 2q as the uneven coating film forming surface may not be a smooth surface.
Moreover, both the one surface 2p and the other surface 2q of the main body 2 are usually flat, and the main body 2 is flat when it is a plate.

(Formation of main body and columnar unit prism)
In addition, the part which consists of the main-body part 2 and the columnar unit prism 1 can be formed from a conventionally well-known method and a transparent material. For example, the prism group formed by arranging the columnar unit prisms 1 and the main body 2 are integrally formed 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 do. Alternatively, it is solidified by a chemical reaction such as a curing reaction or cooling in a state where a resin liquid is brought into contact with the main body 2 formed or formed in advance and the resin liquid is sandwiched between the mold and the main body 2. Thus, different layers can be formed by a molding method in which a prism shape is formed on the surface. When the resin liquid is cured with ionizing radiation using an ionizing radiation curable resin that is cured with ionizing radiation such as ultraviolet rays or electron beams, it is called a so-called 2P method (photopolymer method). At this time, when a transparent substrate such as a resin sheet is used as the main body 2, a prism group made of a resin layer is formed on the transparent substrate. That is, a resin layer having a slight thickness is formed between the adjacent unit columnar prisms 1 even at the valleys. In such a case, the main body 2 is composed of a resin layer in a portion other than the valley and the valley corresponding to the thickness of the resin layer in the valley, and a transparent substrate, and on the transparent substrate. A part of the thickness of the formed resin layer is included.

[Uneven film]
The uneven coating film 3 is a transparent layer including at least a binder resin 3a, spherical particles 3b, and a lubricant. The uneven coating film 3 can be formed by coating with a resin composition (coating liquid or paint) containing a binder resin 3a, spherical particles 3b, a lubricant, and a solvent. When the resin composition contains a solvent, microscopic protrusions 4 that protrude so that the spherical particle 3b portion is lifted are formed by the film thickness reduction due to the shrinkage of the coating film volume during solidification. In addition to the above, the resin composition may contain various known additives such as a dispersant, a stabilizer, and an ultraviolet absorber.

(Binder resin)
As the binder resin 3a, a transparent resin having strong adhesion to the main body 2 and the spherical particles 3b may be appropriately employed from the viewpoint of preventing the spherical particles 3b from dropping off or peeling of the uneven coating film 3 itself. As such a binder resin 3a, 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 thereof include thermosetting polyurethane resins, and ionizing radiation curable resins are acrylic resins, epoxy resins, polyester resins, and the like that are cured by ultraviolet rays or 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.

(Spherical particles)
The spherical particles 3b are transparent particles, and are substantially spherical particles having a spherical shape or a shape close to that. As such spherical particles 3b, 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.
By using the spherical particles 3b in shape as the fine particles for generating the fine protrusions 4, the shape of the generated fine protrusions 4 can be made to be a slippery shape.

  The particle diameter of the spherical particles 3b is, for example, about 1 to 10 μm in particle diameter (not averaged). Further, if the particle size distribution is wide, the distribution of the protrusion heights H of the microprojections 4 is widened. Accordingly, the spherical particles 3b having a large particle diameter generate the fine protrusions 4 having a high protrusion height H and positively act on the formation of voids, but easily fall off from the uneven coating film 3. Moreover, even if it does not fall off, the surface density of the fine protrusions 4 with a high protrusion height H is relatively smaller than when the particle size distribution is narrow, and the degree of influence on scratches is increased. For this reason, it is preferable that the particle size distribution is narrow. Therefore, it is more preferable that the particle size distribution is narrow, that is, a monodispersion or a particle size distribution close to monodispersion. For example, as disclosed in the aforementioned Patent Document 2, it is preferable that the particle size distribution has a half-value width of 1 μm or less in the particle size distribution curve. By using the monodispersed spherical particles 3b, the uniformity of the projection height H of the microprojections 4 is improved, and the degree of load concentration on the microprojections 4 having a relatively high projection height H is reduced. For example, by setting the half-value width of the particle size distribution to 1 μm or less, the half-value width of the distribution of the protrusion height H can be set to approximately 1 μm or less. The half-value width is a particle size width at a portion corresponding to a height that is ½ of the peak height of the particle size distribution curve in the particle size distribution. The same applies to the protrusion height H. For this reason, it can contribute to prevention of a damage | wound and drop-off from the spherical particle 3b side with the effect by a lubricant.

  The particle size distribution and the average particle size are 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 the same as this, and the half-value width is the same. Is the same. Such a volume-based particle size distribution or average particle diameter 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 3b exceeds 10 μm, the light path changing action increases. For this reason, the light condensing action by the prism surface of the optical sheet 10 is reduced, and the optical function as the brightness enhancement sheet 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 3b is less than 1 μm, a high level of technology is required to disperse the spherical particles 3b in the coating composition forming the uneven coating film 3, and the material itself is This is not preferable in that it is expensive.
In addition, content of the spherical particle 3b shall be 2-15 mass% with respect to binder resin, for example. By adjusting the content of the spherical particles 3b, the surface density of the microprojections 4 can be adjusted.

(Lubricant)
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, methylene bis stearamide, alkylene fatty acid amide lubricants of ethylene bis stearamide, metal soap lubricants made of metal stearate such as zinc stearate, calcium stearate, magnesium stearate, stearic acid monoglyceride And fatty acid ester lubricants such as stearyl stearate and hydrogenated oil, and silicone lubricants such as silicone oil and various modified silicone oils.
By blending the lubricant into the uneven coating film 3, when the top of the microprojection 4 comes into contact with the other optical member 20, the slip at the top is improved, and scratches on itself and other members are caused. In addition, the effect of preventing the spherical particles 3b from falling out of the coating film due to the shape deformation of the microprojections 4 can be obtained.

  Among the above-mentioned various lubricants, polyether-modified silicone oil which is a kind of modified silicone oil is a preferable lubricant. 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. As such a polyether-modified dimethylpolysiloxane, for example, a compound represented by the following [general formula 1] in which a polyether skeleton is bonded as a side chain of the dimethylpolysiloxane skeleton is compatible with a binder resin, slip It is a kind of a preferable lubricant in terms of properties.

In [General Formula 1], a is an integer of 1 to 5, b is an integer of 1 to 5, c is an integer of 1 to 30, d is an integer of 1 to 70 that is greater than or equal to c, and R ¹ is H (hydrogen atom). Alternatively, an alkyl group, R ² is H or an alkyl group, and Me is a methyl group.

The polyether-modified dimethylpolysiloxane represented by [General Formula 1] has a polyether skeleton containing an ethylene oxide unit (when R ² is H), a propylene oxide unit (when R ² is a methyl group), and the like. Have. The polyether-modified dimethylpolysiloxane preferably has a weight average molecular weight of 5,000 to 25,000 in terms of lubricant performance. Moreover, the compounding quantity becomes like this. Preferably it is 0.01-5 mass% with respect to binder resin, More preferably, it is 0.1-1 mass%. If the amount of the lubricant is too much, it becomes difficult to disperse the lubricant, and bleeding out to the surface becomes remarkable. In addition, the appearance such as transparency is also hindered. If the amount of lubricant is too small, the effect of the lubricant cannot be obtained.

  Examples of the modified silicone oil include amino-modified silicone oil, epoxy-modified silicone oil, olefin-modified silicone oil, fluorine-modified silicone oil, alcohol-modified silicone oil, and higher fatty acid-modified silicone oil.

  As described above, by containing the lubricant composed of the polyether-modified dimethylpolysiloxane or the like in the binder resin 3a of the concavo-convex coating film 3, it is possible to prevent damage and prevent the spherical particles 3b from falling off. The slipperiness which can exhibit can be given.

[Microprojections]
As described above in the description of the uneven coating film 3, the microprojections 4 are generated on the surface of the portion where the spherical particles 3b exist in the coating film by forming the uneven coating film 3. Further, by adopting the spherical particles 3b as the fine particles in the coating film, the shape of the top of the fine protrusions 4 and the periphery thereof can be generated in a rounded shape instead of a square shape. As a result, the fine protrusions 4 can be made slippery with respect to other optical members in terms of shape.
From the viewpoint of preventing optical adhesion, which is the original purpose of the microprojection 4, the average value of the projection height H of the microprojection 4 is 0.38 μm or more, which is the shortest wavelength of visible light, more preferably visible light. It is preferable that the longest wavelength is 0.78 μm or more. If the average value is less than 0.38 μm, that is, less than the minimum wavelength of visible light, optical adhesion cannot be effectively prevented. The maximum value of the average value of the protrusion height H is not particularly limited, but the maximum particle diameter of the spherical particles 3b for generating the fine protrusions 4 is preferably 10 μm as described above. The thickness is preferably 10 μm.
The average value of the protrusion height H is calculated by arithmetically averaging at least 10 and preferably 30 or more of the fine protrusions 4 for an arbitrary measurement evaluation area.
Further, the surface density of the fine protrusions 4 is preferably about 100 to 3000 / mm ² in terms of dispersion of contact pressure. Beyond this range, a decrease in luminance due to a decrease in light transmittance starts to stand out. On the other hand, if it is less than this range, the voids cannot be generated uniformly on the surface.

[D] Variation:
In addition to the above-described configuration, the optical sheet 10 according to the present invention may have a configuration in which other components are further added, for example, as described below.

  The uneven coating film 3 may have a light diffusion function for diffusing light. For example, the light diffusing function can be imparted by causing the spherical particles 3b contained in the uneven coating film 3 to function as a light diffusing agent. In order to make the spherical particles 3b function as a light diffusing agent, it is preferable to use a material having a large refractive index difference between the spherical particles 3b and the binder resin 3a.

The optical sheet 10 may have an antistatic layer. 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 layer may be added to any one or more of the columnar unit prism 1, the main body 2, and the concavo-convex coating film 3 without providing an antistatic layer separately to provide an antistatic function.
Further, the entire columnar unit prism 1 and the main body 2 may be made of a transparent inorganic material such as glass or quartz.
Further, an antireflection layer composed of a low refractive index layer having a relatively lower refractive index than that of the layer immediately below the surface may be provided on the surface of the optical sheet 10 as the light incident surface. The reflection loss of incident light on the optical sheet 10 can be reduced.

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

[Example 1]
A transparent acrylic UV-curing resin liquid is applied to a metal mold having a mold surface that has a concave and convex shape opposite to that of the prism group consisting of the columnar unit prisms 1, and further, a transparent biaxial film having a thickness of 188 μm. In a state where stretched polyethylene terephthalate films (PET films) are stacked, the resin liquid is cured by ultraviolet irradiation, and the columnar unit prisms 1 are arranged in parallel with each other on one surface of the sheet-like main body 2. The prism sheet member which has the prism group which consists of was produced. The main body 2 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 including a large number of columnar unit prisms 1. The columnar unit prism 1 has a main cut surface shape of a right isosceles triangle having a vertex angle of 90 °, a base of 50 μm, a height of 25 μm over the entire area in the ridge line direction, and an arrangement period of 50 μm. The prism unit has a prism structure in which one surface 2p of the main body 2 is completely covered and the columnar unit prisms 1 are arranged with the same shape, the same size and the same period.

  Next, a coating material having the following composition is applied to the other surface 2q of the main body 2 which is the back surface side of the prism sheet member, followed by heating and drying to form a concavo-convex coating film 3, as illustrated in FIG. An optical sheet 10 was produced.

[Coating composition]
Binder resin (thermoplastic polyester resin) 94.99 parts by mass Spherical particles (cross-linked acrylic resin beads) 5 parts by mass (5% by mass)
(Made by Soken Chemical Co., Ltd., MX-500H, spherical shape with an average particle size of 5 μm, monodisperse type with a particle size distribution of 2 to 10 μm and a half-value width of 1 μm)
Lubricant (polyether-modified dimethylpolysiloxane) 0.01 parts by weight Solvent (methyl ethyl kent) Appropriate amount

In the obtained uneven coating film 3, fine protrusions 4 having a protrusion height H of 10-point average roughness Rz3.24 μm were formed at a surface density of 100 / mm ² .

[Example 2]
In Example 1, an optical sheet was produced in the same manner as in Example 1 except that the blending amount of the lubricant was increased to 5% by mass.

Example 3
An optical sheet was prepared in the same manner as in Example 1, except that the amount of spherical particles was increased to increase the surface density of the microprojections 4 to 3000 / mm ² .

Example 4
In Example 3, an optical sheet was produced in the same manner as in Example 3 except that the blending amount of the lubricant was increased to 5% by mass.

[Comparative Example 1]
In Example 1, an optical sheet was prepared in the same manner as in Example 1 except that the lubricant was removed from the coating composition used for forming the uneven coating film 3.

Example 5
In the first embodiment, the shape of the columnar unit prism 1 is changed as the shape of the columnar unit prism 1 so that the height of the ridge line as shown in FIGS. 2 and 3 becomes a polygonal line shape when viewed from the arrangement direction of the columnar unit prisms. An optical sheet was produced in the same manner as in Example 1 except that the changed height variable prism was used.
The interval d (height) of the apex portion P of the ridge line was distributed in a range of ± 2 μm (23 to 27 μm) with respect to the reference interval (height) of 25 μm. Further, the lengths of the bases of the convex portions T (see FIG. 3) were distributed in the range of 74 to 893 mm.

[Performance evaluation]
The scratch resistance is shown in Table 1 together with the main specifications of Examples 1 to 4 and Comparative Example 1.

The scratch resistance performance was evaluated as follows. As conceptually shown in FIG. 4, a test piece 42 (optical sheet 10) is placed on a movable plate 41 of an abrasion resistance tester (manufactured by Tester Sangyo Co., Ltd., “AB-301 Gakushin type friction fastness tester”). Is placed with the concave-convex coating 3 side up, and an optical member 43 that may be adjacent when the optical sheet 10 is used is placed on the surface of the concave-convex coating 3 of the test piece 42. Further, a load of 250 g is applied to the load portion 44 placed on the optical member 43. The bottom surface of the load portion 44 has a donut shape with an outer diameter of 20 mm and an inner diameter of 10 mm, and the bottom area is 2.36 cm ² . Then, after the movable platen 41 is moved 100 mm in one direction (illustrated by a left arrow) at a moving speed of 5 mm / s over 20 seconds, the contact condition of the contact surface of the test piece 42 and the other optical member 43 is damaged. Is confirmed by visual observation with a microscope in the range of 100 to 1000 times magnification. In this actual measurement, a magnification of 500 times was selected.

The level of performance is determined by level A (indicated by “A” in Table 1, the same applies hereinafter) where no scratch was observed on the contact portion of the other optical member 43 by microscopic observation, and from 1 to 5 by microscopic observation. Although this observation was made, if no scratches could be confirmed by visual observation in the state assembled in the edge light type rear light source device 50 as shown in FIG. Those in which scratches were confirmed by visual observation in the state assembled to the back light source device were evaluated as level C.
In the case of a lens sheet, the area where the scratches are observed is the area extending over the length of 3 mm of the prism ridge, and in the case of the diffusion sheet and the light guide plate, a square area having an area of 9 mm ² is used.

As the optical member 43 that may be adjacent to the uneven coating film 3, as listed in Table 1, evaluation was made with three types of lens sheet, lower diffusion sheet, and light guide plate.
As the lens sheet, a brightness enhancement film (trade name “BEF II”) manufactured by Sumitomo 3M Limited was used. The brightness enhancement film used has a prism group in which columnar unit prisms (triangular prisms) whose main cut surfaces are isosceles triangles are arranged in parallel with each other. The surface to be brought into contact with the test piece 42 is a prism surface, and the direction of the ridge line of the prism is parallel to the moving direction of the movable platen 41 (“peak parallel” in Table 1) and orthogonal (“peak” in Table 1). The evaluation was performed under two conditions of “orthogonal”. FIG. 4 is a drawing when the peaks are orthogonal.
Further, as the lower diffusion sheet, a mat surface of a back surface mat prism sheet (Haze 5) manufactured by Dai Nippon Printing Co., Ltd. was used for evaluation. The surface (contact surface) of the diffusion sheet has a center line average roughness Ra of 0.23 μm and a ten-point average roughness Rz of 3.92 μm. The center line average roughness Ra and the ten-point average roughness Rz are characteristic values measured according to JIS B0601 (1994 edition).
Further, as the light guide plate, a transparent plate having a thickness of 3 mm made of polymethyl methacrylate resin (manufactured by Mitsubishi Rayon Co., Ltd.) for use as a light guide plate was used.

The configuration of the edge light type rear light source device is similar to the rear light source device 50 shown in the cross-sectional view of FIG. 5 on the light emitting surface of the light guide plate 52 having a cold cathode tube 51 on the side surface. Is a planar light source device having a configuration in which a lens sheet 43 (another optical member 20) and a test piece 42 which is the optical sheet 10 are stacked in this order. The optical sheet 10 is arranged with the prism surface side as the light output side. Further, when the other optical member 20 at the time of performance evaluation is a lens sheet, the prism surface side of the lens sheet is arranged in a direction in contact with the surface of the uneven coating film 3 of the test piece 42 (optical sheet 10).
Further, in the form in which the columnar unit prism 1 of the optical sheet 10 is made variable in height as shown in FIG. 2, a polarizing film is formed on the prism surface of the test piece 42 of the optical sheet 10 used for the scratch evaluation. Deploy.
And it visually observes from the observer V side and evaluates an external appearance.

In addition, the drop of the spherical particles 3b is obtained by observing the surface of the concavo-convex coating film 3 after the test with a microscope in the range of magnification of 100 to 1000 times with respect to a square region having an area of 9 mm ^{2 in} the same manner as the evaluation with scratches. The presence or absence of a crater-like depression after the spherical particles 3b are removed is confirmed. In this actual measurement, a magnification of 500 times was selected.

As a result, as shown in Table 1, in each of the examples containing the lubricant, some scratches were slightly observed by microscopic observation (level B), but as a rear light source device, the appearance was practically poor. It was not about. On the other hand, in Comparative Example 1 in which no lubricant was contained, the number of scratches was increased and the appearance was practically poor (level C).
Further, the dropout of the spherical particles 3b was not observed in each example, but in Comparative Example 1, the dropout of the spherical particles 3b was observed when the other optical member was a lens (orthogonal) and a lower diffusion sheet. It was done.

  Further, in the embodiment in which the columnar unit prism 1 according to the fifth embodiment is variable in ridge line height, an edge light type surface light source device as shown in FIG. 5 is used as another optical member 20 on the prism surface of the optical sheet 10. Even when the polarizing film 53 was placed, no defect of light oozing due to optical adhesion was observed. However, in Examples 1 to 4 and Comparative Example 1, a light oozing due to optical contact (a bleed-like bright and dark pattern wet with water) was observed.

DESCRIPTION OF SYMBOLS 1 Columnar unit prism 2 Main-body part 2p One surface 2q The other surface 3 Uneven coating film 3a Binder resin 3b Spherical particle 4 Microprotrusion 10 Optical sheet 20 Other optical members (light guide plate etc.)
40 Measuring Device 41 for Scratch Resistance 41 Movable Plate 42 Test Piece 43 Other Optical Member 44 Adjacent to Load Part 50 Edge Light Type Surface Light Source Device 51 Light Source 52 Light Guide Plate 53 Polarizing Film 60 Conventional Optical Sheet 61 Columnar Unit Prism 62 Main Body Part 63 Concavity and convexity coating 63a Binder resin 63b Spherical particle 64 Minute protrusion d Interval (height of top of ridge line)
C ridge part H protrusion height L ridge line nd normal line (direction)
P Top part T Convex part V Observer

Claims (3)

A prism group consisting of columnar unit prisms whose ridges are arranged in parallel to each other is provided on one surface of a sheet-like main body, and the other surface of the main body has a concavo-convex coating with minute protrusions formed on the surface. An optical sheet having a film,
An optical sheet in which the average protrusion height H of the fine protrusions is 0.38 μm or more, and the uneven coating film contains spherical particles for forming the fine protrusions in a binder resin and a lubricant.   The optical sheet according to claim 1, wherein the lubricant is a polyether-modified dimethylpolysiloxane. When the columnar unit prisms are observed from a direction parallel to the arrangement direction, each columnar unit prism has a polygonal outer contour that forms irregularities, and is defined by the polygonal outer contour of one columnar unit prism. With respect to the plurality of convex portions, the interval along the normal direction set up on one surface of the main body portion between the top portion of each convex portion and the main body portion farthest from the main body portion is not constant, Item 3. The optical sheet according to Item 1 or 2.

Images