Patent ID: 12197066

DESCRIPTION OF EMBODIMENTS

Each embodiment of the present disclosure is described below with reference to the drawings.

Note that, in the description, terms such as “sheet”, “film”, and “plate” are not distinguished from each other based on only differences in names. Therefore, for example, “sheet” is a concept including a member that can be called “film” or “plate”. In addition, in the description, “sheet surface (plate surface, film surface)” refers to a surface that corresponds to a planar direction (surface direction) of an object sheet member when the object sheet member is entirely or broadly viewed. Note that, “sheet surface (plate surface, film surface)” may be called a main surface. Further, in the description, “normal direction to a sheet member” refers to a normal direction to the sheet surface of the object sheet member.

First Embodiment

FIG.1is a schematic view of a structure of a display device10including an optical film100according to a first embodiment. The display device10includes an organic LED (organic light emitting diode) panel15, a circularly polarizing plate20, a touch panel30, a cover glass40, and the optical film100, which are stacked in this order. As one example, the display device10according to the embodiment is formed as a smartphone. However, the display device10may be a tablet terminal (tablet device), a television, a computer display, or a car navigation system.

A display surface (front surface)15A of the organic LED panel15and a back surface of the circularly polarizing plate20are adhered to each other with a first adhesive layer51. A front surface of the circularly polarizing plate20and a back surface of the touch panel30are adhered to each other with a second adhesive layer52. A front surface of the touch panel30and a back surface of the cover glass40are adhered to each other with a third adhesive layer53. The adhesive layers51to53are each a so-called OCA (optical clear adhesive), and each have a high light transmittance.

The optical film100is disposed on a front surface of the cover glass40. In the embodiment, although the optical film100and the cover glass40are not adhered to each other with an adhesive layer, the optical film100and the cover glass40may be adhered to each other with an adhesive layer.

InFIG.1and the figures used in the description below, symbol D1denotes a first direction that is a direction parallel to a film surface of the optical film100. Symbol D2denotes a second direction that is a direction parallel to the film surface of the optical film100and orthogonal to the first direction D1. Symbol D3denotes a third direction that is orthogonal to both the first direction D1and the second direction D2.

Although the organic LED panel15is an organic LED panel having a microcavity structure, the organic LED panel15may have another structure. In general, in a LED panel, a blue shift tends to occur in an image viewed obliquely. Such a blue shift tends to noticeably occur particularly in an organic LED panel having a microcavity structure. Therefore, in the display device10, a color change within a viewing angle is suppressed by the optical film100.

In the embodiment, the circularly polarizing plate20, the touch panel30, and the cover glass40are disposed between the organic LED panel15and the optical film100. The circularly polarizing plate20has a polarizer and a phase difference plate. The phase difference plate is disposed on a side of the organic LED panel15, and the polarizer is joined to a surface of the phase difference plate on a side opposite to the organic LED panel15. Specifically, the polarizer is a linear polarizer, and the phase difference plate is a λ/4 phase difference plate. The touch panel30is a panel including a transparent glass plate. It is desirable that the touch panel30be a capacitive touch panel. The cover glass40has a protection function. However, the cover glass40may have other functions, such as a reflection preventing function.

The optical film100includes a low-refractive-index layer102and a high-refractive-index layer103that are adhered to each other. Although a base material is not disposed on a side of the low-refractive-index layer102opposite to the high-refractive-index layer103, such a base material may be provided.

FIG.2is a partial perspective view of the optical film100. InFIG.2, for explanatory convenience, the high-refractive-index layer103is shown by alternate long and two short dash lines.FIG.3shows the low-refractive-index layer102when viewed in a normal direction thereto, that is, when viewed in the third direction D3.FIG.3is a schematic view of an arrangement of lens portions110(described later) of the low-refractive-index layer102.FIG.4is a sectional view when the optical film100has been cut in a direction along line IV-IV inFIG.3.FIG.5is a sectional view when the optical film100has been cut in a direction along line V-V inFIG.3.

The low-refractive-index layer102has a film-like layer body102A and the plurality of lens portions110, which are integrated with each other, the layer body102A having a front surface and a back surface, and the plurality of lens portions110being disposed two-dimensionally on the back surface of the layer body102A in the first direction D1and the second direction D2. On the other hand, the high-refractive-index layer103is stacked on the low-refractive-index layer102so as to cover the lens portions110and to fill a space between the plurality of lens portions110. Therefore, in the embodiment, an interface between the low-refractive-index layer102and the high-refractive-index layer103has an uneven shape. The high-refractive-index layer103has a film shape having a plurality of holes that accommodate the plurality of lens portions110, and, more specifically, has a double-cross shape or a lattice shape.

Specifically, the high-refractive-index layer103has a film-like layer body103A having a front surface and a back surface, and a double-cross-shape portion103B. The double-cross-shape portion103B is integrated with the front surface of the layer body103A facing the low-refractive-index layer102. When viewed in the third direction D3, the double-cross-shape portion103B has a double-cross shape (grid shape, hash shape, or the like). Note that the low-refractive-index layer102may include a group of lens portions110without having the layer body102A. The high-refractive-index layer103may include only the double-cross-shape portion103B without having the layer body103A.

As shown inFIG.3, the lens portions110are arranged two-dimensionally in a matrix, and, specifically, rows of the plurality of lens portions110that are disposed side by side at equal intervals in the first direction D1are disposed side by side at equal intervals in the second direction D2. In the embodiment, the plurality of lens portions110all have the same shape. The lens portions110that are adjacent to each other in the second direction D2face each other in the second direction D2without being displaced in the first direction D1.

Each lens portion110has a columnar shape tapering toward a lower side inFIG.1of the optical film100, the lower side being one side of the optical film100in a normal direction to the film surface. Each lens portion110includes a flat portion111at an end thereof on a side of the high-refractive-index layer103, which is the one side in the normal direction, the flat portion111extending in a surface direction of the low-refractive-index layer102and the high-refractive-index layer103, that is, along the film surface of the optical film100. Specifically, each lens portion110has a quadrangular pyramidal shape, specifically, a regular quadrangular pyramidal shape; and each flat portion111has a rectangular shape, more specifically, a square shape. On the other hand, each lens portion110includes four side surfaces110S that are positioned between the flat portion111and the layer body102A and that are connected to each other so as to form a rectangular shape.

As shown inFIG.4, two side surfaces110S facing each other in the first direction D1via the flat portion111therebetween taper toward a side of the high-refractive-index layer103. As shown inFIG.5, two side surfaces110S facing each other in the second direction D2via the flat portion111therebetween also taper toward the side of the high-refractive-index layer103. The four side surfaces110S are each a curved surface that protrudes toward the side of the high-refractive-index layer103.

Each side surface110S may be a curved surface that has an arc shape in sectional view and that protrudes toward the side of the high-refractive-index layer103, or a curved surface that has an elliptical arc shape and that protrudes toward the side of the high-refractive-index layer103. Each side surface110S may be a bent surface that protrudes toward the side of the high-refractive-index layer103. Each side surface110S may be a curved surface or a bent surface that protrudes toward the side of the low-refractive-index layer102, or may be a flat surface.

Although clear from the figures, the optical film100of the embodiment is disposed so that the high-refractive-index layer103faces the organic LED panel15. In other words, the optical film100is disposed so that the flat portion111of each lens portion110faces the organic LED panel15. Therefore, the high-refractive-index layer103is positioned on a side of incidence light from the organic LED panel15, and the low-refractive-index layer102is positioned on a side of exiting light.

Symbol AIN, symbol AEX, and symbol PAshown inFIG.4stand for the following.AIN: a first-direction high-refractive-index-side incidence width that is a distance in the first direction D1between the flat portions111of lens portions110that are adjacent to each other in the first direction D1.AEX: a first-direction high-refractive-index-side exiting width that is a distance in the first direction D1between end portions of lens portions110that are adjacent to each other in the first direction D1, the end portions being situated on a side opposite to the flat portions111.PA: a first-direction pitch that is a distance in the first direction D1between midpoints in the first direction D1of lens portions110that are adjacent to each other in the first direction D1.Symbol BIN, symbol BEX, and symbol PBshown inFIG.5stand for the following.BIN: a second-direction high-refractive-index-side incidence width that is a distance in the second direction D2between the flat portions111of lens portions110that are adjacent to each other in the second direction D2.BEX: a second-direction high-refractive-index-side exiting width that is a distance in the second direction D2between end portions of lens portions110that are adjacent to each other in the second direction D2, the end portions being situated on a side opposite to the flat portions111.PB: a second-direction pitch that is a distance in the second direction D2between midpoints in the second direction D2of lens portions110that are adjacent to each other in the second direction D2.

Symbol H inFIGS.4and5denotes the height of a lens portion110.

Here, the optical film100according to the embodiment satisfies the relationships of Condition (1) and Condition (2) below.
((PA−((AIN+AEX)/2))×(PB−((BIN+BEX)/2)))/(PA×PB) is 0.42 or greater and 0.70 or less  Condition (1)
H/((AIN+AEX)/2), andH/((BIN+BEX)/2) are each 1.40 or greater and 3.00 or less  Condition (2)

Note that, below, ((PA−((AIN+AEX)/2))×(PB−((BIN+BEX)/2)))/(PA×PB) in Condition (1) is called a “slope ratio”.

H/((AIN+AEX)/2) in Condition (2) is called an average aspect in sectional view in the first direction, and H/((BIN+BEX)/2) in Condition (2) is called an average aspect in sectional view in the second direction.

The inventor of the present disclosure has found out that, when Condition (1) or (2) above is satisfied, color change within a viewing angle can be effectively suppressed while maintaining a good display quality in front view of the display device10. The inventor of the present disclosure also found out that, when Conditions (1) and (2) are satisfied at the same time, such an effect can be further increased.

The optical film100totally reflects at the side surfaces110S of the lens portions110, for example, light beams L1to L3shown inFIG.4from the organic LED panel15, and diffuses the totally reflected light beams in a wide angle range on a high angle side. Here, when the lens portions110are small, the quantity of light that can be totally reflected by the side surfaces110S may be reduced. When the lens portions110are small and the side surfaces110S have a steep gradient, light can no longer by diffused in a wide range. When the side surfaces110S have a steep gradient and ends of the lens portions110are pointed or rounded, light parallel to a front view direction may be undesirably diffused. As a result of, while considering these matters, carrying out assiduous research regarding, for example, the shape/size of the lens portions110, the inventor of the present disclosure arrived at Conditions (1) and (2) above.

More specifically, when light exiting to the outside from the organic LED panel15via the optical film100was observed in a front view direction of the display device10parallel to the third direction D3and in a direction that was 45 degrees with respect to the front view direction in a plane including the front view direction and the first direction D1, and when color change Δu′v′ of light exiting in the 45-degree direction with respect to the color of light exiting in the front view direction was calculated, it was found that the color change Δu′v′ with the optical film100could be 75% or less of the color change without the optical film100.

Similarly, when light exiting to the outside from the organic LED panel15via the optical film100was observed in the front view direction of the display device10parallel to the third direction D3and in a direction that was 45 degrees with respect to the front view direction in a plane including the front view direction and the second direction D2, and when color change Δu′v′ of light exiting in the 45-degree direction with respect to the color of light exiting in the front view direction was calculated, it was found that the color change Au′v′ with the optical film100could be 75% or less of the color change without the optical film100.

Note that the color change Au′v′ indicates a color difference, and, in the embodiment, the smaller this value is, the smaller the color difference with respect to light exiting in the front view direction. The color change Au′v′ is calculated from the color prescribed by u′ and v′ in a uniform color space. A value of Au′v′ at an angle θ within a certain viewing angle is expressed by the following Formula (1). By substituting the value of 45 degrees for θ in Formula (1), the color change at a visibility angle of 45 degrees can be determined.
[Formula 1]
Δu′v′(θ)=√{square root over ((u′(θ)−u′(0))2−(v′(θ)−v′(0))2)}  (1)

u′ and v′ that are color coordinates of the uniform color space in Formula (1) are expressed by the following Formula (2-1) and Formula (2-2), respectively.

[Formula⁢2]u′=4⁢x-2⁢x+12⁢y+3(2-1)v′=9⁢y-2⁢x+12⁢y+3(2-2)

Here, in each of the formulas above, x and y denote color coordinates that are prescribed by a CIE1931 color space (CIE xyY color space).

Symbol θAinFIG.4denotes an acute angle formed by a straight line with respect to the third direction D3, the straight line passing through an end point of a side surface110S on a side of the high-refractive-index layer103and through an opposite end point. Symbol θBinFIG.5denotes an acute angle formed by a straight line with respect to the third direction D3, the straight line passing through an end point of a side surface110S on the side of the high-refractive-index layer103and through an opposite end point. Under the condition that Conditions (1) and (2) above are satisfied, the angles θAand θBare determined to be in a range greater than 0 degrees and 15 degrees or less. The angles θAand θBare preferably greater than 0 degrees and 10 degrees or less, and more preferably 5 degrees or greater and 10 degrees or less. When the angles θAand θBbecome 0 degrees or less, a problem that releasing from a die becomes difficult occurs. When the angles θAand θBbecome 15 degrees or greater, light totally reflected at a side surface110S may propagate in an excessively oblique manner, and thus a problem that front luminance is reduced may occur. Note that the angles θAand θBcorrespond to “slope angle average” in, for example, Table 1 below.

In order to satisfy Conditions (1) and (2) above, it is preferable that the first-direction high-refractive-index-side incidence width AINand the first-direction high-refractive-index-side exiting width AEXbe such that the relationship in which ((AIN−AEX)×2)/PAis 0.2 or greater and 0.5 or less (in percentage, 20% or greater and 50% or less) is established. It is preferable that the second-direction high-refractive-index-side incidence width BINand the second-direction high-refractive-index-side exiting width BEXbe such that the relationship in which ((BIN−BEX)×2)/PBis 0.2 or greater and 0.5 or less (in percentage, 20% or greater and 50% or less) is established. When ((AIN−AEX)×2)/PAor ((BIN−BEX)×2)/PBis less than 0.2, the effect of suppressing color change may no longer be effectively obtained. When ((AIN−AEX)×2)/PAor ((BIN−BEX)×2)/PBbecomes greater than 0.5, front luminance may be reduced.

In the embodiment, the low-refractive-index layer102and the high-refractive-index layer103are selected so that the difference between the refractive index of the low-refractive-index layer102and the refractive index of the high-refractive index layer103is in the range of 0.05 or greater and 0.60 or less. When the optical film100is combined with the organic LED panel15, the difference between the refractive index of the low-refractive-index layer102and the refractive index of the high-refractive-index layer103is preferably 0.05 or greater and 0.50 or less and more preferably 0.10 or greater and 0.20 or less. Even when the optical film100is combined with a liquid crystal panel instead of the organic LED panel15, the difference between the refractive index of the low-refractive-index layer102and the refractive index of the high-refractive-index layer103is preferably 0.05 or greater and 0.50 or less and more preferably 0.10 or greater and 0.20 or less.

Note that the refractive index of the low-refractive-index layer102is, for example, 1.40 or greater and 1.55 or less, and the refractive index of the high-refractive-index layer103is, for example, 1.55 or greater and 1.90 or less, and is greater than the refractive index of the low-refractive-index layer102.

As described above, the optical film100is disposed so that the high-refractive-index layer103is positioned on a side of incidence light from the organic LED panel15, and the low-refractive-index layer102is positioned on a side of exiting light. In the embodiment, by satisfying Conditions (1) and (2) above, a large amount of light propagating toward the side surfaces110S of the lens portions110, which are part of the low-refractive-index layer102, from the high-refractive-index layer103and being totally reflected by the side surfaces110S is ensured. Here, if the low-refractive-index layer102is positioned on the side of incidence light from the organic LED panel15, and a portion corresponding to the lens portions110is formed in the high-refractive-index layer103, it becomes difficult to ensure a large amount of light to be totally reflected. Therefore, in the optical film100, the high-refractive-index layer103is disposed on the side of the organic LED panel15.

However, the inventor of the present disclosure has confirmed that, when the low-refractive-index layer102is positioned on the side of incidence light from the organic LED panel15and the low-refractive-index layer102includes the lens portions110, advantageous optical performance can be realized.

Note that the low-refractive-index layer102may be formed by curing, for example, ultraviolet curable resin, electron beam curable resin, or thermosetting resin. When the low-refractive-index layer102is formed by curing ultraviolet curable resin, the ultraviolet curable resin may include acrylic resin or epoxy resin.

Similarly, the high-refractive-index layer103may be formed by curing, for example, ultraviolet curable resin, electron beam curable resin, or thermosetting resin. When the high-refractive-index layer103is formed by curing ultraviolet curable resin, the ultraviolet curable resin may include acrylic resin or epoxy resin. When the high-refractive-index layer103is formed as an adhesive layer, the high-refractive-index layer103may be made from an acrylic resin adhesive.

The thickness of the layer body102A of the low-refractive-index layer102in the third direction D3is, for example, 0.5 μm or greater and 30 μm or less. The height of each lens portion110is, for example, 1.0 μm or greater and 30 μm or less. On the other hand, the thickness of the high-refractive-index layer103is 5 μm or greater and 100 μm or less. Note that the thickness of the high-refractive-index layer103is the distance from an end point of the double-cross-shape portion103B on the side of the low-refractive-index layer102to a surface of the layer body103A on a side opposite to the low-refractive-index layer102.

Next, operations in the embodiment is described.

When light for forming an image exits from the organic LED panel15, the light passes through the circularly polarizing plate20, the touch panel30, and the cover glass40, and is incident upon the optical film100. Of the light incident upon the optical film100, a light beam propagating toward a flat portion111and a light beam propagating toward a flat portion of the layer body102A between adjacent lens portions110in the front view direction exit from the low-refractive-index layer102without changing or almost without changing their angles in a propagation direction as shown by symbols L4and L5inFIG.4, and do not contribute to forming an image in front view.

On the other hand, of the light incident upon the optical film100, a light beam that propagates toward a side surface110S of a lens portion110in the front view direction and light beams that propagate toward the side surface110S of the lens portion110in directions that are inclined by only relatively small angles with respect to the front view direction are totally reflected by the side surface110S, have their propagation directions changed toward a high angle side, and exit from the low-refractive-index layer102as shown by symbols L1to L3inFIG.4. That is, the light beams propagating in the directions that are inclined by relatively small angles with respect to the front view direction propagate toward a higher angle side than before after being totally reflected by the side surface110S. Therefore, a large quantity of light is prevented from concentrating in the front view direction and thus a good image is formed when viewed in an oblique direction.

Here, in the embodiment, by forming the optical film100to satisfy Conditions (1) and (2) above, the lens portions110are long in a height direction and the area of each side surface110S can be large and thus light is easily guided to the side surfaces110S of the lens portions110from locations between adjacent lens portions110, as a result of which the light can be diffused in a wide range. By providing the flat portions111at the ends of the lens portions110, light propagating in the front view direction is prevented from being undesirably diffused, and thus a reduction in image quality in front view is suppressed. Since each lens portion110has a columnar shape tapering toward the side of the high-refractive-index layer103, color change can be suppressed in a direction that is inclined with respect to the front view direction in the plane including the front view direction and the first direction D1and in a direction that is inclined with respect to the front view direction in the plane including the front view direction and the second direction D2.

Accordingly, in the present embodiment, it is possible to effectively suppress color change within a viewing angle while maintaining good display quality in front view of the display device.

Modifications of the embodiment above are described below.FIGS.6to9show modifications of the embodiment above. Structural elements in each modification that are the same as the structural elements described in the embodiment above are given the same reference numerals, and matters other than the differences are not described below.

In the modification shown inFIG.6, a side surface110S is a bent surface, and includes a first element surface131, a second element surface132, and a third element surface133, which are three element surfaces each constituted as a plane surface. In the modification shown inFIG.7, a side surface110S includes a curved surface134and a bent surface including two element surfaces135and136that are constituted as plane surfaces. In the modification shown inFIG.8, a side surface110S includes a curved surface137and a plane surface138.

A display device10′ according to the modification shown inFIG.9includes an organic LED panel15, an optical film100, a circularly polarizing plate20, a touch panel30, and a cover glass40, which are stacked in this order. The optical film100is disposed on a display surface (front surface)15A of the organic LED panel15. A front surface of the optical film100and a back surface of the circularly polarizing plate20are adhered to each other with an adhesive layer510. A front surface of the circularly polarizing plate20and a back surface of the touch panel30are adhered to each other with an adhesive layer520. A front surface of the touch panel30and a back surface of the cover glass40are adhered to each other with an adhesive layer530. The adhesive layers510,520, and530are each a so-called OCA (optical clear adhesive), and each have a high light transmittance. Although, in the modification, the organic LED panel15and the optical film100are not adhered to each other with an adhesive layer, the organic LED panel15and the optical film100may be adhered to each other with an adhesive layer.

In the display device10′ according to the modification, the circularly polarizing plate20is disposed closer than the optical film100to outside light incidence side (a side of the cover glass40). Therefore, when outside light is incident toward the organic LED panel15from the cover glass40, it becomes difficult for the outside light to be incident upon the optical film100due to the circularly polarizing plate20, and thus multiple reflection inside the optical film100can be suppressed. Therefore, it is possible to suppress occurrence of visibility hindrance phenomenon, such as iridescent unevenness or interference patterns, and to thus ensure good visibility of an image.

In the embodiment above, each lens portion110of the low-refractive-index layer102may have a quadrangular pyramidal shape, a conical shape, a hexagonal pyramidal shape, or an octagonal pyramidal shape. The arrangement of the lens portions110is not limited to a matrix arrangement, and may be, for example, a houndstooth check arrangement.

When each lens portion110is viewed in a normal direction to the low-refractive-index layer102, in the embodiment above, the flat portion111and a base end portion have square shapes. That is, as shown inFIG.3, when each lens portion110is viewed in the normal direction to the low-refractive-index layer102, the aspect ratio (first maximum width W1:second maximum width W2in a direction orthogonal to a direction that prescribes the first maximum width W1) of each lens portion110(flat portion111and base end portion) is 1:1. However, the shape of each lens portion110is not limited thereto, and, for example, W1:W2may be approximately 1:3 to 3:1. The direction that prescribes the first maximum width W1and the direction that prescribes the second maximum width W2may be parallel to the first direction D1. When the difference between the first maximum width W1and the second maximum width W2is greater than three times, productivity is reduced due to die releasing becoming difficult, and the risk of the lens portions110collapsing is increased.

Although each of the display devices10and10′ above includes a combination of the organic LED panel15and the optical film100whose lens portions110are arranged two-dimensionally, a liquid crystal panel and the optical film100may be combined.

In assembling the display device10′ shown inFIG.9, an optical-film-provided polarizing film in which the optical film100and the circularly polarizing plate20are integrated with each other may be previously fabricated. In this case, the low-refractive-index layer102of the optical film100and the phase difference plate of the circularly polarizing plate20are adhered to each other.

Second Embodiment

FIG.10is a schematic view of a structure of a display device10″ including an optical film200according to a second embodiment. Structural portions of the present embodiment that are the same as the structural portions of the first embodiment are given the same reference numerals, and are not described.

In the optical film200of the display device10″ according to the second embodiment, the orientations of a low-refractive-index layer102and a high-refractive-index layer103are opposite to the orientations of the low-refractive-index layer102and the high-refractive-index layer103of the optical film100in the first embodiment. The other structures are the same as those of the first embodiment.

That is, in the optical film200of the display device10″ according to the second embodiment, the low-refractive-index layer102is positioned on a side of incidence light from an organic LED panel15, and includes lens portions110.

Even in such an optical film200, by satisfying the following Condition (1) and/or Condition (2) described in the first embodiment, it is possible to effectively suppress color change within a viewing angle while maintaining a good display quality in front view of the display device.
((PA−((AIN+AEX)/2))×(PB−((BIN+BEX)/2)))/(PA×PB) is 0.42 or greater and 0.70 or less  Condition (1)
H/((AIN+AEX)/2), andH/((BIN+BEX)/2) are each 1.40 or greater and 3.00 or less  Condition (2)

EXAMPLES

Examples and comparative examples thereof are described below.

Optical films according to Examples 1 to 4 have shapes that are the same as those described in the first embodiment above, and include quadrangular pyramidal lens portions110that are arranged in a matrix at equal pitches of 8.6 μm in both the first direction D1and the second direction D2. The lens portions110have a regular quadrangular pyramidal shape and flat portions111have a square shape.

Low-refractive-index layers102are made of a resin having a refractive index of 1.48, and high-refractive-index layers103are made of a resin having a refractive index of 1.65.

In the optical films according to Examples 1 to 4, the slope ratio determined by ((PA−((AIN+AEX)/2))×(PB−(BIN+BEX)/2)))/(PA×PB) becomes 0.42 or greater and 0.70 or less, and the average aspect in sectional view in the first direction determined by H/((AIN+AEX)/2) and the average aspect in sectional view in the second direction determined by H/((BIN+BEX)/2) are each 1.40 or greater and 3.00 or less.

Note that, since each lens portion110has a regular quadrangular pyramidal shape, the average aspect in sectional view in the first direction and the average aspect in sectional view in the second direction have the same value. Hereunder, the term “average aspect” when simply used means both the average aspect in sectional view in the first direction and the average aspect in sectional view in the second direction.

An optical film according to Example 5 has the same shape as that described in the second embodiment above, and includes quadrangular pyramidal lens portions110that are arranged in a matrix at equal pitches of 8.6 μm in both the first direction D1and the second direction D2. The lens portions110have a regular quadrangular pyramidal shape and flat portions111have a square shape.

A low-refractive-index layer102is made of a resin having a refractive index of 1.48, and a high-refractive-index layer103is made of a resin having a refractive index of 1.65.

Example 5 differs from Examples 1 to 4 in that, whereas, in Examples 1 to 4, the high-refractive-index layer103is positioned on a side of a light source (display panel), in Example 5, the low-refractive-index layer102is positioned on the side of the light source (display panel).

In the optical film according to Example 5, although the slope ratio is 0.42 or greater and 0.70 or less, the average aspect falls outside the range of 1.40 or greater and 3.00 or less.

In Comparative Examples 1 to 4, regular quadrangular pyramidal lens portions are provided, and are arranged in a matrix at equal pitches of 8.6 μm in both the first direction D1and the second direction D2. However, the slope ratio falls outside the range of 0.42 or greater and 0.70 or less, and the average aspect falls outside the range of 1.40 or greater and 3.00 or less. Note that formation materials are the same as those of the examples. That is, in Comparative Examples 1 to 4, although the basic shapes are the same as those in Examples 1 to 4, the slope ratio falls outside the range of 0.42 or greater and 0.70 or less and the average aspect falls outside the range of 1.40 or greater and 3.00 or less.

In Comparative Examples 5 and 6, regular quadrangular pyramidal lens portions are provided, and are arranged in a matrix at equal pitches of 8.6 μm in both the first direction D1and the second direction D2. However, the slope ratio falls outside the range of 0.42 or greater and 0.70 or less, and the average aspect falls outside the range of 1.40 or greater and 3.00 or less. Moreover, the positions of dispositions of a low-refractive-index layer and a high-refractive-index layer are opposite to those in Examples 1 to 4. Specifically, the low-refractive-index layer includes the lens portions. That is, in Comparative Examples 5 and 6, the low-refractive-index layer and the high-refractive-index layer are disposed in this order from a side of a light source (“L high low” in Table 1 below means that the low-refractive-index layer and the high-refractive-index layer are disposed side by side in this order from the side of the light source). Note that formation materials are the same as those in Examples 1 to 5. Specifically, in Comparative Examples 5 and 6, although the basic shapes are the same as that in Example 5, the slope ratio falls outside the range of 0.42 or greater and 0.70 or less and the average aspect falls outside the range of 1.40 or greater and 3.00 or less.

The examples and the comparative examples were evaluated from the viewpoints of luminance and color change. The luminance was evaluated by comparing the luminance (front luminance) in a front view direction of an image displayed by an organic LED display panel to which an optical film was attached with the front luminance of the same image displayed by an organic LED display panel to which an optical film was not attached, and by calculating the ratio of the former to the latter.

The color change was evaluated by comparing the color change Δu′v′ when an image displayed by the organic LED display panel to which an optical film was not attached was viewed from a direction inclined by 45 degrees with respect to the front view direction with the color change Δu′v′ when the same image displayed by the organic LED display panel to which an optical film was attached was viewed from the direction inclined by 45 degrees with respect to the front view direction.

When evaluating the luminance and the color change, a white image was displayed on the entire organic LED display panel.

As a device for measuring the luminance and the color change, CS-1000 manufactured by KONICA MINOLTA, INC. was used.

Dimensional conditions, the slope ratio, the average aspect, the ratio (%) of front luminance with optical film/front luminance without optical film, and the values of color change of the examples and the comparative examples are shown in Table 1 below. Note that the slopes during display corresponds to side surfaces. Although each lens portion has a regular quadrangular pyramidal shape, the side surfaces are curved surfaces and have their curvatures determined.FIG.11is a graph showing the ratio of front luminance with optical film/front luminance without optical film, and the values of color change, with the horizontal axis indicating the ratio of front luminosities and the vertical axis indicating the values of color change.

“High-refractive-index-side exiting width” in the table regarding Example 5 corresponds the symbol AIN(BIN) in FIG.10, and “high-refractive-index-side incidence width” in the table regarding Example 5 corresponds to the symbol AEX(BEX) inFIG.10. That is, “high-refractive-index-side exiting width” and “high-refractive-index-side incidence width” in the table regarding Example 5 are determined in accordance with the definitions described in the first embodiment above. Note that “high-refractive-index-side exiting width” and “high-refractive-index-side incidence width” in the table regarding Comparative Examples 5 and 6 are also determined similarly to Example 5.

TABLE 1STANDARD:COMPARATIVEPANEL ONLYEXAMPLE 1EXAMPLE 2EXAMPLE 3EXAMPLE 4EXAMPLE 5EXAMPLE 1FILMLLLLLLSTRUCTUREHIGH LOWHIGH LOWHIGH LOWHIGH LOWLOW HIGHHIGH LOWPITCH (μm)8.68.68.68.68.68.6SLOPE ANGLE7.97.97.95.812.19.7AVERAGESLOPE20.020.020.040.015.020.4CURVATURERADIUS (μm)HIGH-2.41.60.81.61.83.6REFRACTIVE-INDEX-SIDEEXITINGWIDTH (μm)HIGH-3.62.82.02.83.14.9REFRACTIVE-INDEX-SIDEINCIDENCEWIDTH (μm)HEIGHT (μm)4.24.24.24.53.03.7SLOPE RATIO0.420.550.700.550.510.26AVERAGE ASPECT1.401.913.002.051.220.87FRONT100.0%93.1%92.1%90.4%90.0%91.0%94.7%LUMINANCEΔu′v′0.01500.01120.01030.00990.01030.01110.0123COLOR CHANGE746866697482SUPPRESSIONRATIO(%)COMPARATIVECOMPARATIVECOMPARATIVECOMPARATIVECOMPARATIVEEXAMPLE 2EXAMPLE 3EXAMPLE 4EXAMPLE 5EXAMPLE 6FILMLLLLLSTRUCTUREHIGH LOWHIGH LOWHIGH LOWLOW HIGHLOW HIGHPITCH (μm)8.68.68.68.68.6SLOPE ANGLE7.96.55.812.19.7AVERAGESLOPE20.020.040.015.020.4CURVATURERADIUS (μm)HIGH-3.43.43.62.53.6REFRACTIVE-INDEX-SIDEEXITINGWIDTH (μm)HIGH-4.64.64.84.34.9REFRACTIVE-INDEX-SIDEINCIDENCEWIDTH (μm)HEIGHT (μm)4.24.44.54.13.7SLOPE RATIO0.290.290.260.370.26AVERAGE ASPECT1.051.101.071.210.87FRONT94.2%93.9%93.7%95.1%93.2%LUMINANCEΔu′v′0.01190.01210.01200.01190.0114COLOR CHANGE7980807976SUPPRESSIONRATIO(%)

In Examples 1 to 4, as indicated by the color change suppression ratio, the color change Δu′v′ when the image is viewed from the direction inclined by 45 degrees with respect to the front view direction can be suppressed to 75% or less with respect to the color change without an optical film. The luminance here is 90% or greater of the luminance without an optical film, and a reduction in the luminance in front view is suppressed. The effects of the present disclosure has been confirmed from such results of the examples.

In Example 5, the color change Δu′v′ when the image is viewed from the direction inclined by 45 degrees with respect to the front view direction can be suppressed to 75% or less with respect to the color change without an optical film. Note that, although the slope ratio is 0.51 in Example 5, it is presumed that, even for the slope ratios of Examples 1 to 4 within a range of 0.42 to 0.70, good color change suppression effects are provided. Although the average aspect in Example 5 is 1.22 and falls outside the range of 1.40 or greater and 3.00 or less, when the range is 1.40 or greater and 3.00 or less, it is presumed that, due to the lens portions110not being too pointed while ensuring a large area of each side surface110S, the effects of suppressing color change and suppressing a reduction in front luminance can be increased.

A straight line L inFIG.11indicates the tendency of the optical films according to Comparative Examples 5 and 6 in which the low-refractive-index layer and the high-refractive-index layer are disposed in this order from the side of the light source. Examples 1 to 4 are positioned below the straight line L, and the optical films in Examples 1 to 4 can suppress color change by a greater degree than the optical films in Example 5 and Comparative Examples 5 and 6 in which the low-refractive-index layer and the high-refractive-index layer are disposed in this order from the side of the light source. From the results, it has been confirmed that greater color change suppression effects are obtained when the high-refractive-index layer103is positioned on the side of the light source (display panel) than when the low-refractive-index layer102is positioned on the side of the light source (display panel).

(Simulation)

In the optical film100of the first embodiment, the high-refractive-index layer103facing the side of the light source includes a double-cross-shape portion103B and the low-refractive-index layer102includes lens portions110. In a simulation to be described below, the effectiveness of such a form of the first embodiment was examined by comparison with a simulation Comparative Example X. The simulation Comparative Example X is an optical film in which lens portions are provided in a high-refractive-index layer facing a side of a light source and a low-refractive-index layer is stacked thereupon has a double-cross shape.

In the lens portions110of the optical film100of the first embodiment to be the object of simulation, the following dimensional conditions were set. Note that the high-refractive-index-side exiting width and the high-refractive-index-side incidence width become the same values in both the first direction D1and the second direction D2.Lens portions have regular quadrangular pyramidal shapes.Pitch: 8.6 μm (in both the first direction D1and the second direction D2)Slope angle average: 12.1 (degrees)Slope curvature radius: 15 (μm)High-refractive-index-side exiting width: 1.8 (μm)High-refractive-index-side incidence width: 3.1 (μm)Height: 3 (μm)Slope ratio: 51(%)Average aspect: 1.22

In the lens portions of the simulation Comparative Example X, the following dimensional conditions were set. The high-refractive-index-side exiting width and the high-refractive-index-side incidence width become the same values in both the first direction D1and the second direction D2.

Lens portions have regular quadrangular pyramidal shapes.Pitch: 8.6 μm (in both the first direction D1and the second direction D2)Slope angle average: 12.1 (degrees)Slope curvature radius: 15 (μm)High-refractive-index-side exiting width: 5.5 (μm)High-refractive-index-side incidence width: 6.8 (μm)Height: 3 (μm)Slope ratio: 8(%)Average aspect: 0.48*Note that the “high-refractive-index-side exiting width” of the simulation Comparative Example X is calculated in accordance with the definition described in the first embodiment above by the distance in the first direction D1(second direction D2) between flat portions111of lens portions110that are adjacent to each other in the first direction D1(second direction D2).

Similarly, the “high-refractive-index-side incidence width” of the simulation Comparative Example X is calculated in accordance with the definition described in the first embodiment above by the distance in the first direction D1(second direction D2) between end portions of lens portions110that are adjacent to each other in the first direction D1(second direction D2), the end portions being situated on a side opposite to the flat portions111.

In the simulation results, the color changes Δu′v′ with respect to a front view at a plurality of visibility angles (45 degrees, 30 degrees, 15 degrees) inclined with respect to the front view were calculated. Table 2 below shows the simulation results.

TABLE 2SIMULATIONFIRSTCOMPARATIVEEMBODIMENTEXAMPLE XCOLOR CHANGE (VISIBILITY0.01100.0139ANGLE: 45 DEGREES)COLOR CHANGE (VISIBILITY0.00660.0069ANGLE: 35 DEGREES)COLOR CHANGE (VISIBILITY0.00180.0019ANGLE: 15 DEGREES)

According to the simulation results above, in the first embodiment, for each of the visibility angles, the degree of color change is smaller than that in the simulation Comparative Example X, and the color change is effectively suppressed. From such simulation results, it has been confirmed that the double-cross-shape portion103B of the high-refractive-index layer103, which faces the side of the light source, and the lens portions110of the low-refractive-index layer102are effective in suppressing color change than when the lens portions are arranged at the high-refractive-index layer.

REFERENCE SIGNS LIST

10display device15organic LED panel15A display surface20circularly polarizing plate30touch panel40cover glass51first adhesive layer52second adhesive layer53third adhesive layer100optical film102low-refractive-index layer102A layer body103high-refractive-index layer103A layer body103B double-cross-shape portion110lens portion110S side surface111flat portion131first element surface132second element surface133third element surface134curved surface135,136element surface137curved surface138plane surface