JP5970786B2 - Optical sheet and video display device including the same - Google Patents

Description

  When the present invention is applied to video display, the light control function that transmits light necessary for video display and absorbs light unnecessary for video display improves the quality of the video light, thereby improving contrast and adjusting the viewing angle ( The present invention relates to an optical sheet that can be enlarged, reduced, and deflected) and an image display apparatus including the optical sheet. In particular, the present invention relates to an optical sheet with an improved light control function and a video display device including the same.

In various video display devices such as liquid crystal displays, plasma displays, EL (electroluminescent) displays, electronic pavers, or rear projection displays, by transmitting light necessary for video display and absorbing unnecessary light for video display, There is known an optical sheet that improves the quality of image light by improving the contrast or adjusting the viewing angle to enlarge, reduce, or deflect.
For example, in Patent Document 1, as an optical sheet capable of improving the contrast and improving the quality of image light, a plurality of light transmitting portions formed in parallel along a plane parallel to the sheet surface and capable of transmitting light, and the light An optical sheet having a plurality of light absorbing portions arranged in parallel between transmitting portions and capable of absorbing light is disclosed. A typical shape and arrangement of the light absorbing portions are columnar bodies having a wedge-shaped cross section. When the light absorbing portions arranged along a plane parallel to the sheet surface are observed from the normal direction of the sheet surface, a stripe shape is formed. doing. Further, the optical sheet may be composed of only a layered light control layer including the light absorbing portion and the light transmitting portion. However, in general, light transmission is possible from the viewpoint of mechanical strength and ease of manufacture. A transparent base material layer is further laminated.

Typically, the formation of such a light control layer comprising a light absorbing portion and a light transmitting portion is typically performed by first forming a transparent light transmitting portion on the base material layer with an ultraviolet curable resin, and then between the light transmitting portions. It is carried out by filling the concave portion formed in the above with a composition for forming a light absorbing portion containing light absorbing particles and a transparent ultraviolet curable resin. This filling is usually performed by applying the light-absorbing part-forming composition over the entire surface including the surface on the concave part and the light-transmitting part, and then adding an extra light-absorbing part-forming composition on the light-transmitting part other than the concave part. It is performed by a so-called wiping method which is scraped off by a doctor blade.
As the composition for forming a light absorbing part, a composition in which light absorbing particles are dispersed in a resin binder made of a transparent ultraviolet curable resin or the like is used. However, when carbon black is dispersed in the resin binder as light absorbing particles as it is, the particle diameter is small, for example, several tens to several hundreds of nanometers. The light-absorbing particles that remain without being completely scraped off when they are scraped off easily absorb light even at the light-transmitting portion, and easily impair the light-transmitting performance of the light-transmitting portion. Therefore, in order to reduce the scraping failure, in order to increase the substantial particle size so that the light absorbing particles are caught by the doctor blade, those having a small particle size such as carbon black have a larger particle size, for example, average particles. In general, colored resin beads dispersed and held in resin beads (particles) having a diameter of 3 μm or more are used as light absorbing particles.

JP 2011-34060 A

As described above, the light absorption part includes a resin binder and colored resin beads as light absorption particles dispersed in the resin binder inside. However, since the binder resin is a transparent resin, Unwanted light that has entered the absorption part is absorbed by the colored resin bead part, but is not absorbed by the resin binder part. The light absorption part has sufficient light absorption performance according to its volume in the light control layer. It cannot be said that it is demonstrating.
In addition, further enhancement of the contrast enhancement function by the light control layer and the viewing angle adjustment function is also desired.

  That is, an object of the present invention is to provide an optical sheet having an improved light control function of a light control layer having a light absorption part including a light absorption particle and a light transmission part, and an image display device including the optical sheet. is there.

Therefore, in the present invention, an optical sheet having the following configuration and an image display device including the optical sheet are provided.
(1) A plurality of light transmission parts arranged along a plane parallel to the sheet surface so that necessary light can be transmitted, and a plurality of light absorption parts arranged so as to be able to absorb unnecessary light between the light transmission parts. In an optical sheet comprising at least a light control layer having
The light absorbing portion includes light absorbing particles and a transparent resin binder that disperses and holds the light absorbing particles,
The content ratio of the light absorption particles in the light absorption part is 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the total amount of the light absorption particles and the resin binder.
The dispersion state of the light absorbing particles in the light absorbing portion is defined as a cross section in which the light absorbing portion is parallel to the normal line of the sheet surface and orthogonal to the extending direction in the target portion of the light absorbing portion. Two arbitrary particles selected from a plurality of light-absorbing particles observed at the main cutting plane and observed at the main cutting plane, and two inscribed lines in contact with the two particles are both For any two particles that are inscribed lines that do not overlap with other light-absorbing particles other than these two particles, between the contact points with the particles,
The average inclination angle θ _AVE obtained by averaging the inclination angles of the two inscribed lines and the normal of the sheet surface, including the respective inclination angles, for a plurality of sets of the two arbitrary particles. Is 18 ° to 35 °,
An optical sheet having an average particle diameter d of the light-absorbing particles of 2 μm or more and an optical sheet of 35 ° or less that is 0.5 times or less of the maximum width Wt in the main cut surface shape of the light-absorbing part. .
(2) The optical sheet according to (1), wherein the light absorbing particles are colored resin beads.
(3) The optical sheet according to (2), wherein the colored resin beads are crosslinked acrylic resin beads.
(4) The optical sheet according to (2) or (3), wherein the colored resin beads contain carbon black.
(5) The optical sheet according to any one of (1) to (4), wherein a transparent base material layer capable of transmitting light is laminated on the light control layer.
(6) The optical sheet according to any one of (1) to (5), wherein a functional layer is further laminated.
(7) An image display device comprising at least the optical sheet according to any one of (1) to (6) and an image light generation unit.

According to the optical sheet according to the present invention, the light control function of the light control layer can be improved because the dispersion state of the light absorbing particles inside the light absorbing portion is further optimized. As a result, when applied to video display, the contrast enhancement function and viewing angle adjustment function can be improved, and the quality of video light can be further improved.
According to the video display device of the present invention, since the optical sheet is provided as an optical sheet, the above-described effects can be obtained. As a result, the image light quality can be further improved.

Sectional drawing (a) which shows one embodiment of the optical sheet by this invention, and the partial expanded sectional view (b) explaining the tangent with respect to the dispersion state of the light absorption particle | grains inside a light absorption part. Sectional drawing which shows the cross-sectional example of a light absorption part. Sectional drawing which shows another embodiment of the optical sheet by this invention. 1 is a cross-sectional view illustrating an embodiment of a video display device according to the present invention.

  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] Optical Sheet First, the cross-sectional view of FIG. 1 is a cross-sectional view (a) showing an embodiment of the optical sheet according to the present invention, and an inscribed line drawn between any two particles in the light absorbing portion. It is a partial expanded sectional view explaining the tangent which this invention does not make object.
An optical sheet 10 shown in FIG. 1A includes a light control layer 1 and a transparent base material layer 4 laminated adjacent to the light control layer 1.
In the present invention, the base material layer 4 is not essential.

<< Light Control Layer 1 >>
The light control layer 1 is disposed so as to be able to absorb unnecessary light between a plurality of light transmitting portions 1a disposed along a plane parallel to the sheet surface 10p so that necessary light can be transmitted. A plurality of light absorbing portions 1b. The plane parallel to the sheet surface 10p usually means the layer surface 1p of the light control layer 1, and in this embodiment, the layer surface 1p of the light control layer 1 is also the sheet surface 10p of the optical sheet 10. It is.
In the present embodiment, the arrangement of the light transmission parts 1a is an arrangement in the horizontal direction of the drawing with a constant arrangement period P. Similarly, in the present embodiment, the arrangement of the light absorbers 1b is also arranged in the left-right direction of the drawing with the same arrangement period P as the arrangement period P.

  Furthermore, the light control layer 1 of the present embodiment also has land portions 1c that transmit the necessary light over the entire surface of the light control layer 1. The land portion 1c is formed integrally with the light transmitting portion 1a and is made of the same material. Therefore, the optical properties such as the refractive index and the transmittance are the same at the boundary between the land portion 1c and the light transmitting portion 1a. It has become. The land portion 1c is transparent and is a portion that cannot absorb unnecessary light.

  This figure is a cross-sectional view of the surface including the normal line N of the sheet surface 10p, and in the form of the figure, the cross-sectional shape of the light transmitting portion 1a is a trapezoidal shape, and the length of the side of the upper base and the lower base is long. The upper base with the smaller height is arranged as the upper part of the drawing. On the other hand, the cross-sectional shape of the light absorbing portion 1b is also a trapezoidal shape, and the light absorbing portion 1b is disposed with its upper base at the bottom of the drawing, contrary to the light transmitting portion 1a. Further, the level in the direction of the normal N of the upper base of the light transmitting portion 1a and the level in the direction of the normal N of the lower base of the light absorbing portion 1b are the same level, and the layer surface 1p of the light control layer 1 However, a certain sheet surface 10p is formed and is flush.

  Thus, each of the light transmitting portion 1a and the light absorbing portion 1b is a columnar body having a trapezoidal cross section, and both the extending directions of the columnar bodies are linear and perpendicular to the paper surface. Therefore, the cross-sectional view of the same figure is also a main cut surface with respect to the light transmitting portion 1a and the light absorbing portion 1b.

Here, in the present invention, the “main cut surface” is a surface parallel to the normal line N of the sheet surface 10p, and an element of interest (for example, the light transmitting portion 1a or the light absorbing portion 1b) is the sheet surface 10p. Means a plane defined as a cross section orthogonal to the extending direction of the target portion of the element of interest when the shape has an extending direction when observed from the direction of the normal N. The part of interest is the part of the cross section.
Further, the cross-sectional shape at the “main cut surface” is referred to as “main cut surface shape”.

[Light transmission portion 1a and land portion 1c]
The light transmitting portion 1a is made of a transparent material, and preferably made of a transparent resin from the viewpoint of easy formation. As this transparent resin, a known transparent resin can be used. For example, as the transparent resin, a thermoplastic resin such as an acrylic resin, a polycarbonate resin, or a styrene resin can be used. However, the transparent resin is preferably a curable resin, or an ionizing radiation that can be cured by ultraviolet rays or an electron beam, in terms of solvent resistance and rapid solidification at the time of formation as compared with the thermoplastic resin. It is preferable to use a curable resin. Examples of the ionizing radiation curable resin include acrylate-based, epoxy-based, and polyester-based resins. For example, acrylate-based resins include urethane acrylate resins.
What is necessary is just to set the thickness of the light transmissive part 1a suitably according to a light control function, for example, it is about 20-200 micrometers. The arrangement period P of the light transmission parts 1a is, for example, 10 to 200 μm.
The light transmitting portion 1a normally occupies a major portion of the area of the light control layer 1 projected onto the layer surface 1p or the sheet surface 10p. The main means that the projected area exceeds 50%.

The land portion 1 c is not essential, but is a portion that can be incidentally formed simultaneously with the formation of the light transmission portion 1 a and is an element belonging to the light control layer 1. The land portion 1c is transparent and is also a portion that cannot absorb unnecessary light.
The land portion 1c is typically formed integrally with the light transmitting portion 1a and made of the same material. For this reason, the boundary between the land portion 1c and the light transmitting portion 1a is an optical element such as a refractive index and a transmittance. The physical properties are the same.
The material constituting the land portion 1c can be the same as that of the light transmitting portion 1a.

[Light Absorbing Unit 1b]
The light absorbing portion 1b is composed of light absorbing particles 2 and a transparent resin binder 3 that disperses and holds the light absorbing particles 2.
The dimensions of the light-absorbing portion 1b in the main cut surface are, for example, a maximum width Wt of 5 to 50 μm, a minimum width Wb of 2 to 50 μm, a height H of 10 to 200 μm, which is equal to or less than the thickness of the light transmitting portion 1a. The hypotenuse inclination angle α formed by the hypotenuse and the normal N is 0 to 15 ° {see FIG. 2A}.
The arrangement period P in the main cut surface shape of the light absorbing portion 1b is the same as that of the light transmitting portion 1a and is, for example, 10 to 200 μm.

The maximum width Wt is the maximum width in the direction parallel to the sheet surface 10p or the layer surface 1p, as shown in the cross-sectional view of FIG. 2A in the case where the main cut surface has a trapezoidal shape. . The minimum width Wb is the minimum width in a direction parallel to the sheet surface 10p or the layer surface 1p. In each drawing of FIG. 2A to FIG. 2F including FIG. 2A, the surface parallel to the sheet surface 10p is the layer surface 1p of the light control layer 1, and this layer surface 1p is the sheet surface 10p. But it is drawn in the case of some form.
If it demonstrates with a specific example, in the case of the trapezoidal light absorption part 1b of Fig.2 (a), the dimension of the lower base of a trapezoid will be the maximum width Wt, and the dimension of an upper base will be the minimum width Wb.

(Light Absorbing Particle 2)
The light-absorbing particles 2 may be organic particles typified by resin beads, inorganic particles typified by glass beads, etc., but are preferably organic particles from the viewpoint of ease of production and availability. Some resin beads are used.
Examples of the resin of the colored resin beads include acrylic resin, melamine resin, polycarbonate resin, styrene resin, and urethane resin. Any of these resins is a crosslinked resin in that the particle shape can be maintained in the composition for forming a light absorption part due to insolubility of the solvent. Among these, acrylate-based ionizing radiation curable resins, that is, acrylic resins are usually used as the resin of the resin binder 3 in which the light absorbing particles 2 are dispersed and held. A resin, that is, a cross-linked acrylic resin is preferred. Therefore, as the colored resin beads, crosslinked acrylic resin beads are preferable.
The colorant for coloring the resin beads to be colored resin beads may be any colorant that can make the resin beads light-absorbing, and may be a dye in addition to the pigment. From the viewpoint of superiority, a pigment, particularly carbon black is preferably used. For this reason, as the resin beads, preferably, colored resin beads containing carbon black and colored in black are used.

  The color of the light-absorbing particles 2 is a dark color, and the representative color of the dark color is black. However, if it does not adversely affect the video display color, it may be a chromatic color with low brightness, and consciously modulates the video display color. For the purpose, it may be a chromatic color with low brightness.

As already described in the background art section, when the light absorbing particles 2 are dispersed as they are in the resin binder 3 as the light absorbing particles 2, the particle diameter of the carbon black is as small as 10 to 500 nm. When the absorbing portion 1b is formed, when the excess light absorbing portion forming composition on the light transmitting portion 1a is scraped off by the wiping method, the light absorption in the light absorbing portion forming composition that remains without being sufficiently scraped off. The particle | grains 2 may reduce the light transmittance of the light transmissive part 1a.
However, even a small colorant having a particle diameter of 500 nm or less, such as carbon black, can be used for the light-absorbing particles 2 in the form of colored resin beads contained in resin beads having a particle diameter of 2 μm or more. It is possible to effectively prevent a decrease in light transmittance of the light transmitting portion 1a.
However, the light-absorbing particles 2 having a particle diameter of less than 2 μm may be eliminated, but may be contained as long as the light-transmitting performance of the light-transmitting portion 1a is not hindered in practice. Specifically, the content of the light absorbing particles 2 having a particle diameter of less than 2 μm is 7 parts by mass or less with respect to 100 parts by mass of the total amount of the light absorbing particles 2 and the resin binder 3 constituting the light absorbing unit 1b. It is preferable to stop.
In addition, the content rate in the light absorption part 1b as the whole of the light absorption particle 2 is about 10-60 mass parts with respect to 100 mass parts of whole quantity of the light absorption particle 2 and the resin binder 3. FIG. If it is less than this range, sufficient light absorption performance cannot be imparted, and if it exceeds this range, the applicability of the composition for forming a light absorption part is lowered.

  As described above, the particle diameter of the light absorbing particles 2 is preferably 2 μm or more at least from the viewpoint of reducing a decrease in light transmittance of the light transmitting portion 1a when the light absorbing portion 1b is formed by a wiping method. It is good to do.

  If the average particle diameter d is taken as the particle diameter of the light-absorbing particles 2, it is preferable that the particle diameter is 2 μm or more from the viewpoint of an effective dispersion state with respect to light absorption inside the light-absorbing portion 1b.

  Here, in the present invention, the average particle diameter d means the volume average particle diameter of primary particles in which particles are not aggregated.

  When the particle size distribution (particle size distribution) of the light-absorbing particles 2 is narrow, the lower limit particle size of the particle size distribution may be 2 μm or more as described above. When the dispersed light absorbing particles 2 are used, the lower limit of the average particle diameter d may be 2 μm. On the other hand, when the particle size distribution has a certain extent, the lower limit particle size of the particle size distribution may be set to 2 μm or more as described above. Therefore, in such a case, the average particle size d exceeds 2 μm. It is preferable to use one having a size of 4 μm or more.

Further, from the viewpoint of effective filling of the light absorbing particles 2 into the light absorbing portion 1b and further effective dispersion state, the average particle diameter d is the maximum width in the main cut surface shape of the light absorbing portion 1b. Although it is necessary to make the maximum width Wt or less in relation to Wt, it is preferable that the following relational expression [1] is satisfied.
d / Wt ≦ 0.5 [1]
That is, the average particle diameter d is preferably 0.5 times or less of the maximum width Wt of the light absorbing portion 1b.

In addition, as shown in FIG. 2A, when the main cut surface shape of the light absorbing portion 1b is a trapezoidal shape, the light absorbing portion 1b has a portion having a width smaller than the maximum width Wt. This corresponds to the smallest minimum width Wb. Thus, in the case of the main cut surface shape having the minimum width Wb smaller than the maximum width Wt, effective filling and effect of the light-absorbing particles 2 inside the light-absorbing portion 1b including the portion of the minimum width Wb are achieved. From the viewpoint of a typical dispersed state, it is preferable that the minimum width Wb is a dimension that can be filled with the light absorbing particles 2 having a particle diameter of 2 μm or more. For this purpose, the minimum width Wb is preferably 2 μm or more.
Conversely, when the light absorbing particles 2 are taken as a reference, and the size of the light absorbing particles 2 is viewed as the average particle diameter d, the relationship between the average particle system d and the minimum width Wb is the particle size distribution. In consideration of the case, it is preferable that the average particle diameter d is twice or less the minimum width Wb, and therefore, the following relational expression [2] should be satisfied.
2d ≦ Wb [2]
(Wt> Wb ≧ 2 μm)
However, the average particle diameter d is preferably 2 μm or more due to the relationship with the wiping method described above. In this respect, the minimum width Wb is the lower limit of the width in which the light-absorbing particles 2 of 2 μm can be accommodated, and Wb ≧ 2 μm. When the light-absorbing particles 2 are monodispersed and have a narrow particle size distribution, the average particle diameter d itself may be the minimum width Wb or less. That is, in this case, d ≦ Wb. For example, the average particle diameter d is 4 μm with respect to the minimum width Wb of 6 μm.

If the range of the particle diameter of the light-absorbing particles 2 is indicated by the average particle diameter d, it is about 2 to 10 μm, for example.
If the average particle diameter d of the light absorbing particles 2 exceeds the above range, the light absorbing particles 2 are dispersed and held inside the light transmitting portion 1a when the high-definition light absorbing portion 1b, for example, the maximum width Wt is about 10 μm or less. This is not easy, and the light absorption performance is likely to deteriorate due to an increase in the proportion of the resin binder 3.

(Resin binder 3)
As the resin binder 3, a transparent binder material containing a resin can be used, and typically, an ionizing radiation curable resin cured with ultraviolet rays can be used. The resin of the resin binder 3 (binder resin) may be a thermoplastic resin such as an acrylic resin, a polycarbonate resin, or a styrene resin, but is preferably a curable resin from the viewpoint of rapid solidification at the time of formation, It is preferable to use an ionizing radiation curable resin that is cured by ultraviolet rays or electron beams. As the ionizing radiation curable resin, resins such as acrylate, epoxy, and polyester are used.
The resin binder 3 may contain various additives such as a stabilizer in addition to the binder resin.

  The resin binder 3 adjusts the relationship between the refractive index nb and the refractive index na when the refractive index of the resin binder 3 is nb and the refractive index of the material constituting the light transmission part 1a is na. Thus, the light control function can be adjusted by adjusting the amount of reflection including light refraction and total reflection at the interface between the light absorbing portion 1b and the light transmitting portion 1a.

(Average inclination angle θ _AVE )
What is characteristic in the present invention is that the dispersion state in the light absorption part 1b of the light absorption particle 2 has a specific state. This dispersed state can be known as the dispersed state of the light absorbing particles 2 in the main cross section of the light absorbing portion 1b.

  The inventors of course have the light control function of the light control layer 1 related to the shape of the main cut surface of the light absorption part 1b. In addition to this, the light control function includes the light absorption part 1b. It was considered that the dispersion state of the light-absorbing particles 2 imparting light-absorbing property to the inside of the light-absorbing portion 1b is also related. In particular, the light-absorbing particles 2 are on the order of 500 nm or less, such as submicron order, and are not significantly different on the order of less than 1/10, or even less than 1/100, compared to the maximum width Wt of the light-absorbing portion 1b. It was thought that the influence of the dispersion state of the light absorbing particles 2 inside the light absorbing portion 1b is large when the particle size is 1 μm or more. Therefore, as a result of earnest research, the reason is not clear, but it has been found that the light control function by the light absorbing portion 1b can be effectively enhanced in a specific dispersion state grasped as follows.

  The specific dispersion state of the light absorbing particles 2 can be known by observing the main cross section of the light absorbing portion 1b that appears when the optical sheet 10 is cut. The main cross section can be observed with a microscope, and an electron microscope can be used as the microscope. For example, it can be known by cutting the optical sheet 10 into a thin piece sample with a microtome and observing the sample with a transmission electron microscope. Observation of the dispersion state with a microscope and measurement of the inclination angle of the inscribed line for grasping the dispersion state can be easily performed by taking a photograph of an image of the observed cross section.

The specific state of the dispersed state of the light-absorbing particles 2 on the main cut surface is any two particles 2 selected from a plurality of light-absorbing particles 2 observed on the main cut surface, Two arbitrary tangents that are in contact with two particles 2 are inscribed lines that do not overlap with other light-absorbing particles 2 other than the two particles 2 between the contact points that are in contact with the two particles 2. With respect to the particles 2, the inclination angles of the two inscribed lines and the normal line N of the sheet surface 10p are averaged with respect to the plurality of sets of the arbitrary two particles 2 including the respective inclination angles. The dispersion state is such that the average inclination angle θ _AVE is 35 ° or less.

  In the present specification, “light-absorbing particles 2” may be simply referred to as “particles 2” from the viewpoint of easy reading of a document. Similarly, for example, the “light-absorbing particles 2a” may be referred to as “particles 2a”.

Hereinafter, the average inclination angle θ _AVE will be described with reference to a partially enlarged cross-sectional view of the light absorbing portion 1b in FIG.

In the figure, light absorbing particles 2a, 2b, 2c,... Are dispersed as light absorbing particles 2 in order from the sheet surface 10p side above the drawing inside the light absorbing portion 1b. Here, the arbitrary two light-absorbing particles 2 are the light-absorbing particles 2a closest to the sheet surface 10p inside the light-absorbing portion 1b and the light-absorbing particles 2b closest to the sheet surface 10p in the drawing, and then the light-absorbing particles 2b. Is selected. Moreover, in the same figure, the layer surface 1p of the light control layer 1 is also the sheet surface 10p.
As a tangent to the set of the two particles 2a and 2b, there are a total of four tangent lines, two internal tangent lines and two external tangent lines. Among these, the tangents targeted in the present invention are inscribed lines, and are two inscribed lines L _L and inscribed lines L _R drawn with solid lines in the figure. In the figure, the two tangent lines Lo _L and the outer tangent line Lo _R drawn by broken lines are not the tangent lines targeted by the present invention.

The difference between the subscripts L and R in the inscribed line L _L and the inscribed line L _R is the upper part of the drawing of the two particles 2a and 2b of interest (the same applies to the other two particles 2). For the particle 2a closer, in other words, closer to the sheet surface 10p, the subscript L is attached to the tangent located on the left side in the drawing, and the subscript is attached to the tangent located on the right side in the drawing. The letter R is attached.

The difference between the inscribed lines L _L and L _R and the circumscribed lines Lo _L and Lo _R is that the two inscribed lines L _L and L _R intersect each other between the two particles 2a and 2b. The lines Lo _L and Lo _R do not intersect each other between the two particles 2a and 2b. In other words, the two inscribed lines L _L and L _R are both in contact with one of the two particles 2a and 2b on one side of the tangent, and the two particles 2a and 2b on the other side of the tangent. The two outer tangents Lo _L and Lo _R are both in contact with both of the two particles 2a and 2b on one side of the tangent.

The two inscribed lines L _L and L _R have an inclination angle θ with respect to the normal N standing on the seat surface 10p, the inscribed line L _L has an inclination angle θ _L , and the inscribed line L _R has an inclination angle θ _R. It has become.
In the present invention, the inclination angle θ _L and the inclination angle θ _R are both regarded as positive numbers. In other words, the inclination angle θ _L and the inclination angle θ _R are not captured by the angle in which the measurement direction exists, such as clockwise or counterclockwise.

As the arbitrary two particles 2, the set of the light absorbing particles 2 a closest to the sheet surface 10 p and the third light absorbing particle 2 c closest to the sheet surface 10 p in the drawing is not adopted. The reason is that, as shown in the figure by tangent lines, the two inscribed lines Lx _L and Lx _R for the light absorbing particles 2a and the light absorbing particles 2c exist between the light absorbing particles 2a and the light absorbing particles 2c. This is because it overlaps with the light absorbing particles 2b. In this way, in the portion between the two particles 2a and 2c, the tangent line overlapping with the light absorbing particles 2 other than the two particles 2a and 2c (specifically, the light absorbing particles 2b) is the two particles described above. Since the disposition relationship between particles at more distant positions than in the case of 2a and 2b is evaluated as a dispersed state, it is not adopted as an inscribed line for evaluating the inclination angle θ.
In the present invention, the term “not overlapping with the other light absorbing particles 2” includes not contacting the other light absorbing particles 2.
Two particle 2a, the sense that the portion between 2c, for inscribed line Lx _L, means that between the contact points Cc _L between the contact Ca _L and the light-absorbing particles 2c of the light absorbing particles 2a, inscribed line Lx _R means a point between the contact point Ca _R with the light absorption particle 2a and the contact point Cc _R with the light absorption particle 2c.
Unlike the outer tangent, the two inner tangents L _L and L _R always intersect each other between the two particles 2a and 2b. Due to the nature of the inscribed line, the average inclination angle θ _AVE does not become zero. A positive number.

In this way, as the arbitrary two particles 2, the light absorbing particles 2 a and the light absorbing particles 2 b satisfying the predetermined condition that the inscribed lines L _L and L _R do not overlap with the other light absorbing particles 2. A pair is chosen.

In the same manner, a plurality of other pairs of two arbitrary particles 2 are selected, and the inclination angles θ _L and θ _R of the inscribed lines L _L and L _R with respect to the normal N are obtained. An average of these inclination angles θ _L and θ _R including the inclination angle θ _L and the inclination angle θ _R is calculated as an average inclination angle θ _AVE . That is, the average inclination angle θ _AVE is calculated by the following equation [3].
Average inclination angle θ _AVE = (Inclination angle θ _L i + Inclination angle θ _R i) / 2n [3]
(Where i is a positive integer up to 1, 2, 3,..., N)
The number n of sets of any two particles 2 required for averaging is at least 5 sets, preferably 10 sets or more. That is, n is 5 or more, preferably 10 or more.

And in this invention, this average inclination _| tilt angle (theta) _AVE shall be 35 degrees or less. That is, the following conditional expression [4] is satisfied.
Average inclination angle θ _AVE ≦ 35 ° [4]
When the average inclination angle θ _AVE exceeds 35 °, the light absorption performance decreases as in the measurement results of Examples and Comparative Examples described later, so the average inclination angle θ _AVE is preferably set to 35 ° or less.
The lower limit of the average inclination angle theta _AVE, as described above, copying the nature zero inscribed line, the average inclination angle theta _AVE is smaller becomes higher spacing between 2 between the light-absorbing particles away in the thickness direction Thus, the degree of light passing from the oblique direction between these light absorbing particles 2 increases, and it becomes difficult to exhibit sufficient light absorbing performance with only the single light absorbing portion 1b. Normally, when the average inclination angle θ _AVE is less than 18 °, it is difficult for the adjacent light absorbing portion 1b to receive the light passing through and the light absorbing performance as the whole of the plurality of light absorbing portions 1b is hardly exhibited. For this reason, the average inclination angle θ _AVE is preferably set to 18 ° or more.

In order to set the average inclination angle θ _AVE to 35 ° or less, the main cut surface shape of the light absorbing portion 1b, the maximum width Wt and the minimum width Wb, the particle diameter of the light absorbing particles 2, and the light absorbing particles 2 and the resin This can be done by adjusting the ratio of the binder 3 or the like. When the width of the light absorbing portion 1b is close to the particle diameter of the light absorbing particles 2, the dispersion state of the light absorbing particles 2 inside the light absorbing portion 1b is aligned, and the average inclination It becomes easy to satisfy the conditional expression [4] for the angle θ _AVE . For example, the alignment means that the light absorbing particles 2 are arranged in a line in the height H direction of the light absorbing portion 1b. Of course, it's not really neatly arranged in a line.
However, if the width of the light absorbing portion 1b is too close to the particle diameter of the light absorbing particles 2, it is difficult to form a dispersion state in which the light absorbing particles 2 are sufficiently filled in the light absorbing portion 1b. . In this respect, the particle diameter of the light-absorbing particles 2 is the relational expression [1] with the maximum width Wt of the light-absorbing portion 1b, or the relational expression with the minimum width Wb when it has a finite minimum width Wb. It is preferable to satisfy [2]. The interval between the light absorbing particles 2 is adjusted by the ratio between the light absorbing particles 2 and the resin binder 3. By doing so, a dispersed state having an average inclination angle θ _AVE of 35 ° or less can be more easily formed.

As described above, by setting the average inclination angle θ _AVE to 35 ° or less, the dispersion state of the light absorbing particles 2 inside the light absorbing portion 1b becomes a more optimized arrangement. The light absorbing action of the light absorbing portion 1b is improved, and the light control function can be improved.
As a result, when applied to video display, light control functions such as contrast enhancement functions and viewing angle adjustment functions that adjust the viewing angle adjustment, such as enlargement, reduction, and deflection, can be improved, and the quality of video light can be improved. Can be increased.

[Method of Forming Light Transmitting Part 1a, Light Absorbing Part 1b, and Land Part 1c]
The light transmitting portion 1a, the light absorbing portion 1b, and the land portion 1c can be formed by a conventionally known method for forming the light control layer 1.
For example, a hot pressing method in which a heated mold is pressed against a thermoplastic resin layer, a casting method in which a thermoplastic resin composition is injected into a mold and solidified, an injection molding method, and an ionizing radiation curable resin composition are molded. A 2P method (photopolymer method) or the like that is injected into the mold (inside) and cured with ionizing radiation can be used. Among these molding methods, the 2P method is more preferable in terms of excellent productivity. In the 2P method, a cylindrical (cylindrical) mold can be used to continuously form a belt-like sheet or the like. If the base material layer 4 is used as the belt-like sheet, the land portion 1c laminated on the base material layer 4, the light transmitting portion 1a laminated integrally with the land portion 1c on the land portion 1c, and this light A concave portion corresponding to the shape of the light absorbing portion 1b can be formed on the surface on the transmitting portion 1a side. Further, if the mold surface of the mold and the base material 4 are brought into close contact with each other, the light transmitting portion 1a on the base material 4 and light on the light transmitting portion 1a side are formed in a form without the land portion 1c. A concave portion corresponding to the shape of the absorbing portion 1b can be formed.
And if the inside of the said recessed part is filled with the composition for light absorption part formation containing the light absorption particle | grains 2 and the resin binder 3 by a wiping method, and solidifies, the light absorption part 1b can be formed.

<< Base material layer 4 >>
The base material layer 4 is composed of a transparent base material that can transmit light. The base material layer 4 supplements the mechanical strength when the mechanical strength of the light control layer 1 alone is insufficient, and acts as a base material when the light control layer 1 is formed in the 2P method (photopolymer method) or the like. Easy to form.
The base material layer 4 is not particularly limited as long as it is a material having transparency, and a known material can be appropriately employed. For the base material layer 4, a resin film such as a polyethylene terephthalate film is typically used. As the base material layer 4, a resin film is typical in this way. Examples of the resin include polyester resins such as polyethylene terephthalate, polyolefin resins such as cycloolefin polymers, and celluloses such as triacetyl cellulose. Resin, acrylic resin, polycarbonate resin or the like. These resins are used in the form of films, sheets, and plates. Note that “film”, “sheet”, and “plate” are generally roughly distinguished by thickness, but in the present invention, they are merely different in name, and there is no particular distinction in meaning. The thickness of the base material layer 4 is, for example, 25 to 300 μm.
In the present invention, the base material layer 4 is not essential.

<Deformation>
In the present invention, the optical sheet 10 can take other forms besides the above-described form. Some of these will be described below.

[Main cut surface shape of light absorbing portion 1b]
In FIG. 2, the example of various shapes of the main cut surface shape of the light absorption part 1b is shown. First, FIG. 2A shows a trapezoidal shape in which the four sides are straight lines in the embodiment illustrated in FIG. 1 and also has a wedge shape.
For example, even if the main cutting plane shape of the light absorbing portion 1b is the same wedge shape, as shown in FIG. 2 (b), it is closer to the lower base including the lower base of the original trapezoidal shape than the original lower base. A wedge-shaped shape with the base of the wedge widened like a large bottom triangle, as shown in Fig. 2 (c). A pentagonal shape with a sharp edge, or a shape with a curved wedge tip, such as a trapezoidal shape with the upper base removed and the upper base portion made semicircular as shown in FIG. 2 (d). Among these, FIG. 2B and FIG. 2C also have a shape in which the hypotenuse has a broken line, and FIG. 2D has a shape in which the hypotenuse has a curved line.
Alternatively, the main cut surface shape of the light absorbing portion 1b may be a quadrangular shape whose slope is parallel to the normal line N and perpendicular to the sheet surface 10p, as shown in FIG.

Among these shapes, shapes having a minimum width Wb, that is, shapes having a finite minimum width Wb and Wb> 0 are FIGS. 2A, 2B, and 2E, The shapes in which the minimum width Wb does not exist, that is, the minimum width Wb = 0 are shown in FIGS. 2C and 2D. For the shape where the minimum width Wb = 0, that is, the shape where the minimum width Wb does not exist, the relational expression [2] that defines the magnitude relationship between the average particle diameter d of the light-absorbing particles 2 and the minimum width Wb described above. Is not considered.
However, as shown in FIG. 2 (f), the triangular shape in which the wedge-shaped tip has an acute angle and the minimum width Wb is zero makes it difficult to fill the light-absorbing particles 2 to the tip. FIG. 2C, which is a broken line with the hypotenuse convex toward the outside, is preferable.

In the shape where the finite minimum width Wb does not exist as shown in FIGS. 2C and 2D, the existence ratio of the light absorbing particles 2 is small at the tip portion of the wedge, and particularly in FIG. 2C. If the wedge tip is sharp, the tendency is strong. However, as shown in FIG. 2C, if dH is as small as about 1/20 with respect to the original height H = Hb + dH, the portion of dH at the wedge tip is excluded as having a small contribution to the light absorption function. The portion Hb can be regarded as the height H. As a specific example, when Hb is 76 μm and dH is 4 μm with respect to a height of H80 μm, dH / H = 1/20.
As can be seen from FIGS. 2C and 2D, dH is a height (thickness) from the wedge tip with respect to a portion where the width tends to narrow toward the wedge tip. .
Then, considering the width at the height Hb as the minimum width Wb, the relational expression [2] between the average particle diameter d and the minimum width Wb may be applied.

  The main cut surface shape of the light absorbing portion 1b is not shown, but in the case of the trapezoidal shape in FIG. 2A, the portion on the side that is flush with the layer surface 1p of the light control layer 1 on the sheet surface 10p side. However, it may not be flush with each other and may have a shape that is recessed inside the light absorbing portion 1b. The depression is, for example, about 0.5 to 6 μm. Such a dent is a volume accompanying the drying and curing of the light absorbing part forming composition when the light absorbing part forming composition is filled in the recess corresponding to the shape of the light absorbing part 1b to be formed. Due to shrinkage.

  As described above, the contrast improving function and the viewing angle adjusting function can be adjusted by adjusting the main cut surface shape of the light absorbing portion 1b. For example, the viewing angle can be adjusted by adjusting the traveling direction of light, or the amount of light absorption with respect to various angle components of external light that causes a decrease in contrast can be adjusted.

[Arrangement of Light Transmission Part 1a and Light Absorption Part 1b]
In the above-described embodiment, the light transmission portion 1a is a columnar body, and the extending directions extending linearly of the columnar body are parallel to each other, and the light control layer 1 is parallel to the sheet surface 10p in a certain direction at regular intervals. At the same time, the light absorbing portion 1b is also a columnar body, and the linearly extending directions of the columnar body are parallel to each other at regular intervals. The arrangement is such that the light control layers 1 are arranged in a certain direction along the layer surface 1p parallel to the sheet surface 10p. In both the light transmitting portion 1a and the light absorbing portion 1b, the direction perpendicular to the extending direction is the arrangement direction. In other words, when observed from the direction of the normal N, the light transmitting portions 1a and the light absorbing portions 1b are alternately arranged in a stripe shape.
However, in the present invention, the arrangement of the light transmission part 1a and the arrangement of the light absorption part 1b are not limited to this. For example, when observed from the direction of the normal N, the light absorbing portion 1b is arranged in a square lattice shape that runs vertically and horizontally, and the square portion of the square lattice is an array that becomes the light transmitting portion 1a. In other words, the shape of the light absorbing portion 1b is such that a columnar body extending linearly in the first direction and a columnar body extending linearly in a second direction orthogonal to the first direction are mutually connected. It becomes a fused shape. When the first direction and the second direction are orthogonal to each other, a square lattice is formed. When the first direction and the second direction are crossed obliquely, an oblique lattice is formed.

[Functional layer 5]
The optical sheet in the present invention includes the light control layer 1 and the base material layer 4 in the above-described form, but may further have a configuration in which functional layers are laminated. As the functional layer, various functional layers in a conventionally known optical sheet for an image display device can be appropriately employed.

  For example, the optical sheet 10 illustrated in FIG. 3 has a configuration in which a pressure-sensitive adhesive layer 5 a and a release film 5 b are stacked as the functional layer 5 on the layer surface 1 p of the light control layer 1 in this order. A transparent adhesive is used for the adhesive layer 5a, for example, an acrylic adhesive, a polyester adhesive, a silicone adhesive, or the like. The release film 5b is a film that temporarily protects the surface of the pressure-sensitive adhesive layer 5a until use. Usually, a transparent release film is used, and the surface of the polyester film is release-treated with silicone or the like. Is used.

In the form of the optical sheet 10 shown in FIG. 3, the sheet surface 10 p located on the upper side in the drawing is the layer surface 1 p located on the upper side in the drawing among the two layer surfaces of the light control layer 1. It becomes a different aspect. Of the two layer surfaces of the light control layer 1, which layer surface is labeled 1p is not essentially distinguished, but in this specification, the layer surface positioned on the upper side in the drawing is the layer surface 1p. And will be called with the reference numerals. The same applies to the sheet surface 10p.
On the other hand, in the form of the optical sheet 10 shown in FIG. 1, the sheet surface 10p is flush with the layer surface 1p. Thus, in the form in which another layer is laminated on the layer surface of the light control layer 1, the layer surface 1p and the sheet surface 10p may be different surfaces. However, the sheet surface 10p and the layer surface 1p are parallel to each other.
Thus, in the present invention, in the arrangement of the light transmitting portion 1a and the light absorbing portion 1b, the “parallel surface” of “arranged along a plane parallel to the sheet surface” means the sheet surface 10p itself, Alternatively, it means an exposed surface that comes into contact with air, such as the layer surface 1p, or a virtual surface parallel to these surfaces, for example, the light transmission in FIG. It may be a virtual surface such as a dotted line drawn between the portion 1a and the land portion 1c.

The functional layer 5 can be broadly classified into an optical functional layer responsible for optical functions and a non-optical functional layer responsible for functions other than optical functions.
Examples of optical functional layers include a near-infrared absorbing layer that absorbs near infrared rays, an ultraviolet absorbing layer that absorbs ultraviolet rays, or neon light that absorbs neon light from a plasma display panel body that can provide visual effects. Absorptive layer, wavelength filter layer that suppresses transmission of specific wavelength light, such as a color correction function that corrects the display image to a desired color tone, and transmits the remaining wavelength light, an antireflection layer (antiglare, usually provided in the outermost layer) Any of antireflection, antiglare and antireflection)), a Fresnel lens layer that deflects the traveling direction of light, or the light control layer 1 described above. When the functional layer 5 is the light control layer 1, the optical sheet 10 has a configuration including two or more light control layers 1.
Examples of non-optical functional layers include an electromagnetic wave shielding layer that shields electromagnetic waves from the image generation unit such as a plasma display panel, a surface protective layer or hard coat layer that protects the surface, an antistatic layer, a pollution prevention layer, and an impact resistant layer. There are a barrier layer that prevents mass transfer between two layers, an adhesive layer (including a pressure-sensitive adhesive layer) that adheres the two layers, or the base material layer 4 described above.

Each layer of the optical functional layer and the non-optical functional layer may be a single layer that also functions, or may be shared between the optical functional layer and the non-optical functional layer. Further, the near-infrared absorbing layer, the ultraviolet absorbing layer, the neon light absorbing layer, the wavelength filter layer, and the like are also used as the light transmitting portion 1a and the land portion 1c in the base material layer 4, the adhesive layer 5a, or the light control layer 1. It can also be made.
The position of the functional layer 5 is the case where the functional layer 5 is a layer other than the base material layer 4, for example, as illustrated in FIG. The material layer 4 may be opposite to the light control layer 1 or both of them. Further, the position of the functional layer 5 may be between the base material layer 4 and the light control layer 1.

  By laminating the functional layer 5, a function corresponding to the function of the laminated functional layer 5 can be imparted.

[B] Video Display Device A video display device according to the present invention includes at least the optical sheet and the video generation unit. The video display device 20 shown in the exemplary embodiment of FIG. 4 includes an optical sheet 10 and a plasma display panel as the video generation unit 6. The optical sheet 10 is directly bonded to the surface of the front glass substrate of the plasma display panel by the adhesive layer 5a. For this reason, as shown in the figure, the optical sheet 10 has an adhesive layer 5a for bonding, and as a whole layer structure, in order from the viewer V side, the base material layer 4, the light control layer 1, It has an adhesive layer 5a.

  By configuring the video display device 20 to include the video generation unit 6 and the optical sheet 10, the effect of the optical sheet 10 can be obtained, and the contrast of video light generated by the video generation unit 6 can be improved. The quality of the video generated by the video generation unit 6 can be improved by adjusting the viewing angle.

  In the video display device 20 of the present invention, in the form in which the optical sheet 10 includes an adhesive layer 5a for laminating the optical sheet 10 on another adherend, the adherend is a plasma display panel or the like. For example, a glass plate or a resin plate disposed on the viewer V side of the video generation unit 6 with or without an air layer between the video generation unit 6 and the like. The front plate may be used. The position of the optical sheet 10 with respect to the front plate may be on the viewer V side or on the image generation unit 6 side.

  In the video display device 20 of the present invention, when the main cutting surface shape of the light absorbing portion 1b in the light control layer 1 of the optical sheet 10 is a wedge shape, the direction of the tip of the wedge is as shown in FIG. In addition to the form on the video generation unit 6 side, there may be a form on the viewer V side opposite to this. The direction of the image light from the image generation unit 6 and the amount of unnecessary external light absorbed can be adjusted by adjusting the direction of the wedge-shaped tip, thereby adjusting the quality of the image light and the viewing angle. In addition, the degree of external light absorption can be adjusted.

  In the video display device 20 of the present invention, the position where the optical sheet 10 is arranged is not limited to the video generator 6 as shown in FIG. When the light source unit 6 illuminates from the back side, such as a transmissive liquid crystal display panel, there is a mode in which the light source unit side of the back side of the image generation unit 6 is provided. In this case, according to another embodiment of the present invention. There may be a form in which the optical sheet is arranged on the viewer V side. By disposing the optical sheet 10 on the back side of the video generation unit 6, the traveling direction and spread of the illumination light from the back toward the video generation unit 6 is adjusted, that is, the viewing angle is adjusted, thereby improving the quality of the video. be able to.

In the present invention, as the image generation unit 6, in addition to the plasma display panel, there are various display panels such as a liquid crystal panel and an EL (electroluminescence) panel, or a digital micromirror device (DMD). obtain.
In the present invention, the video display device 20 includes, in addition to the video generation unit 6 and the optical sheet 10, a drive circuit for the video generation unit 6, wiring for connecting the drive circuit and the video generation unit 6, and an integrated panel. Depending on the use of the chassis or frame to be modularized, and the video display device 20, for example, in the case of a television receiver, various input / output components such as a tuner, a known housing, and a housing for housing these ( Cabinet) or the like. These other components are not particularly limited, and depend on the application.

[C] Application The optical sheet according to the present invention is suitably used for an image display device. It is also used for rear projection screens.
The image display device provided with the optical sheet according to the present invention includes a television receiver, measuring equipment and instruments, office equipment, medical equipment, computing equipment, telephone, electronic signboard, amusement equipment, digital photo frame, rear projection display, etc. It is suitable as a video display device.

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

Example 1
As Example 1, an optical sheet 10 with an adhesive layer as shown in FIG. 3 was produced as follows.

(1) Preparation of cylindrical mold As a cylindrical mold for molding the light control layer 1, a mold having an uneven shape corresponding to the light transmitting portion 1a on the mold surface was prepared. The uneven shape of the mold surface is a shape in which a portion of the light transmitting portion 1a becomes a concave portion and a portion corresponding to the light absorbing portion 1b becomes a convex portion. The surface of the mold surface was plated with copper, and this mold surface was cut with a diamond bit and then chrome plated to form a mold. The irregularities of the mold surface of the mold are trapezoids having a main cut surface shape of 10 μm at the bottom corresponding to the maximum width Wt, 3 μm at the top bottom corresponding to the minimum width Wb, and 88 μm in height when captured by the light absorbing portion 1b. A light absorbing portion 1b made of a linear columnar body has a plurality of light absorbing portions 1b arranged in an arrangement period P of 45 μm in a direction orthogonal to the extending direction with the extending directions parallel to each other. Corresponds to the shape of irregularities that can be formed.

(2) Preparation of Base Material Layer 4 As the base material layer 4, a transparent polyethylene terephthalate film having a thickness of 100 μm was prepared.

(3) Formation of the light transmission part 1a Ionizing radiation curing that can be cured with ultraviolet rays while inserting and transporting the base material layer 4 prepared in the above (2) between the mold prepared in the above (1) and the nip roll. The resin composition was supplied onto the base material layer 4, and the resin composition was filled between the base material layer 4 and the molding die by a pressing force between the molding die and the nip roll. Thereafter, the resin composition is cured by irradiating ultraviolet rays from the base material layer 4 side, and then the resin layer cured on the base material layer 4 together with the base material layer 4 is released from the mold with a peeling roll. An intermediate sheet member was obtained. In this intermediate sheet member, the resin layer on the base material layer 4 has a land portion 1c having a thickness of 20 μm on the base material layer 4 side, and light transmission portions 1a arranged at an array period of 45 μm are formed on the land portion 1c. The groove-like recesses between the arranged light transmission parts 1a correspond to the shape of the light absorption part 1b.

The ionizing radiation curable resin composition includes an acrylate-based prepolymer, an acrylate-based bifunctional monomer, an acrylate-based reactive dilution monomer, a phosphoric ester-based mold release agent, and a photopolymerization initiator. A resin composition was used (indicated by component A in Table 1).
This ionizing radiation curable resin composition exhibits a refractive index of 1.550 at a measurement wavelength of 589 nm after curing.

(4) Formation of the light absorbing portion 1b On the surface of the intermediate sheet member produced in (3) above on the light transmitting portion 1a side, a light absorbing portion forming resin composition that can be cured with ultraviolet rays is applied, and a doctor blade is used. By using the wiping method used, the groove-shaped recesses existing between the light transmitting portions 1a were filled, and the excess resin composition for forming the light absorbing portion on the light transmitting portions 1a was scraped off. Then, the intermediate | middle optical sheet member in which the light control layer 1 was formed on the base material layer 4 was obtained by irradiating an ultraviolet-ray, hardening the resin composition for light absorption part formation, and forming the light absorption part 1b.

The resin composition for forming a light absorption part includes an acrylate-based prepolymer, an acrylate monomer, colored resin beads as the light-absorbing particles 2 (18% by mass with respect to the total amount of the composition), and a photopolymerization initiator. An acrylate resin composition was used. The colored resin beads (indicated by component X in Table 1) are crosslinked acrylic resin beads (manufactured by Ganz Kasei Co., Ltd.) having an average particle size of 4.0 μm and containing 25% by mass of carbon black.
This resin composition for forming a light-absorbing part has a refractive index at a measurement wavelength of 589 nm after curing of the composition (indicated by component B in Table 1) corresponding to the resin binder 3 excluding the colored resin beads. 1.540 is shown.

(5) Formation of pressure-sensitive adhesive layer 5a An acrylic resin-based transparent pressure-sensitive adhesive containing a cross-linking agent and a benzotriazole-based ultraviolet absorber has a thickness of 25 μm on the release surface of a release film 5b made of polyethylene terephthalate having a thickness of 25 μm. After forming the pressure-sensitive adhesive layer 5a in such a manner, the intermediate optical sheet member prepared above is bonded to the surface of the pressure-sensitive adhesive layer 5a on the surface on the light control layer 1 side, as shown in FIG. The optical sheet 10 with the target adhesive layer was produced. The pressure-sensitive adhesive layer 5 a and the release film 5 b correspond to the functional layer 5.

Example 2
In Example 1, the colored resin beads, which are the light absorbing particles 2 in the composition for forming a light absorbing portion, were crosslinked acrylic resin beads having an average particle diameter of 4.0 μm and containing 25% by mass of carbon black (Negami Industrial Co., Ltd.). An optical sheet 10 was produced in the same manner as in Example 1 except that the product was changed to a product made by the company (indicated by component Y in Table 1).

Example 3
In Example 1, except that the components other than the light absorbing particles 2 in the composition for forming a light absorbing portion were the same as the components of the ionizing radiation curable resin used for forming the light transmitting portion 1a, An optical sheet 10 was produced in the same manner as in Example 1.

<< Comparative Example 1 >>
In Example 1, an optical sheet was produced in the same manner as in Example 1 except that the mold was changed and the shapes and dimensions of the light transmission part 1a and the light absorption part 1b of the light control layer 1 were changed. The light control layer 1 has a trapezoidal shape with a main cut surface shape of a bottom 10 μm corresponding to the maximum width Wt, a bottom 6 μm corresponding to the minimum width Wb, and a height 85 μm when captured by the light absorbing portion 1 b. It consists of a linear columnar body. The arrangement period P is the same 45 μm.

《Measurement evaluation of average inclination angle θ _AVE 》
About the optical sheet of an Example and a comparative example, in order to observe the main cut surface of the light absorption part 1b, it cut | disconnects with a microtome, produces a thin piece, From the photograph image which this thin piece image | photographed with the transmission electron microscope, an inscribed line The inclination angles θ _{L and} θ _R formed by L _{L and} L _{R and the} normal line N were measured. The tilt angle was measured by selecting 10 sets of two particles 2 for each optical sheet. The average inclination angle θ _AVE was calculated by averaging 20 points including the viewing angle θ _L and the inclination angle θ _R. For the calculation, first, an average value of 10 points is obtained for the viewing angle θ _L , similarly, an average value of 10 points is obtained for the viewing angle θ _R , and these average values are further averaged to obtain a final average inclination angle θ. _AVE was calculated. The results are summarized in Table 1.

<< Evaluation of light control function >>
As a light control function, the contrast improvement performance when applied to the image generation unit 6 including a plasma display panel was evaluated. Specifically, the optical sheet originally bonded to the glass surface of the front glass substrate of the plasma display panel incorporated in the plasma TV is peeled off, and the optical sheet obtained above is bonded instead. Luminance and black luminance were measured. The optical sheets of Examples and Comparative Examples were bonded to the glass surface of the front glass substrate by the adhesive layer 5a that was peeled off and exposed from the release film 5b.
Contrast is measured with luminance meter (LS-110, manufactured by Konica Minolta Sensing Co., Ltd.) from the front position 2 m away from the center of the TV screen in the normal direction of the screen at an illuminance of 550 lx under the indoor fluorescent lamp. did. White luminance is measured by displaying a full white screen in white mode with a color pattern generator (CG-935N, manufactured by Kenwood TMI Co., Ltd.). Black luminance is black in cross hatch mode with the same pattern generator. A black pattern was measured by displaying a lattice pattern of white vertical lines and horizontal lines. Then, the contrast was calculated as [white luminance / black luminance]. The results are shown in Table 2.

As shown in Table 2, Examples 1-3 in which the dispersion state of the light-absorbing particles 2 satisfies the conditions defined in the present invention in which the average inclination angle θ _AVE is 35 ° or less are Comparative Examples 1 that do not satisfy these conditions In contrast, the contrast was improved, the light control function was improved, and the quality of the image light was improved. The contrast improvement rate was 23.3% (10.3 / 8.4) in Example 1 and Example 2 with respect to this reference, with the contrast of Comparative Example 1 being 1.00. Example 3 improved by 1.22 and 21% (10.2 / 8.4).

DESCRIPTION OF SYMBOLS 1 Light control layer 1a Light transmission part 1b Light absorption part 1c Land part 1p (Light control layer) layer surface 2 Light absorption particle 3 Resin binder 4 Base material layer 5 Functional layer 5a Adhesive layer 5b Release film 6 Image | video production | generation part 10 Optical sheet 10p Sheet surface 20 Video display device L _L inscribed line L _R inscribed line Lo _L outer tangent line Lo _R outer tangent line Lx _L intangible line not subject to Lx _R intangible line outside subject N normal V V observer Wb of light absorbing portion inclination angle theta _AVE average inclination angle of the inclined angle theta _R inscribed line minimum width Wt light absorbing portion maximum width α hypotenuse inclined angle theta _L inscribed line

Claims (7)

A plurality of light transmitting portions arranged along a plane parallel to the sheet surface so that necessary light can be transmitted, and a plurality of light absorbing portions arranged to absorb unnecessary light between the light transmitting portions. In an optical sheet comprising at least a light control layer having,
The light absorbing portion includes light absorbing particles and a transparent resin binder that disperses and holds the light absorbing particles,
The content ratio of the light absorption particles in the light absorption part is 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the total amount of the light absorption particles and the resin binder.
The dispersion state of the light absorbing particles in the light absorbing portion is defined as a cross section in which the light absorbing portion is parallel to the normal line of the sheet surface and orthogonal to the extending direction in the target portion of the light absorbing portion. Two arbitrary particles selected from a plurality of light-absorbing particles observed at the main cutting plane and observed at the main cutting plane, and two inscribed lines in contact with the two particles are both For any two particles that are inscribed lines that do not overlap with other light-absorbing particles other than these two particles, between the contact points with the particles,
The average inclination angle θ _AVE obtained by averaging the inclination angles of the two inscribed lines and the normal of the sheet surface, including the respective inclination angles, for a plurality of sets of the two arbitrary particles. Is 18 ° to 35 °,
An optical sheet having an average particle diameter d of the light absorbing particles of 2 μm or more and 0.5 times or less of a maximum width Wt in the main cut surface shape of the light absorbing portion.   The optical sheet according to claim 1, wherein the light absorbing particles are colored resin beads.   The optical sheet according to claim 2, wherein the colored resin beads are crosslinked acrylic resin beads.   The optical sheet according to claim 2 or 3, wherein the colored resin beads contain carbon black.   The optical sheet according to claim 1, wherein a transparent base material layer capable of transmitting light is laminated on the light control layer.   The optical sheet according to claim 1, wherein a functional layer is laminated on the light control layer. An image display device comprising at least the optical sheet according to claim 1 and an image light generation unit.

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