JP2007079392A - Optical film, display device, and deflection plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an antireflection function while maintaining the state in which color shift is inconspicuous. <P>SOLUTION: A multiplicity of convex parts 103 are disposed on the surface randomly. The thickness of a low refractive index layer 102 except the convex parts 103 decreases in the direction from the center of a transparent support 101 to its ends. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical film in which at least one low refractive index layer having a lower refractive index than that of the transparent support is laminated on the transparent support.

  When the surface of a display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), or a cathode ray tube display device (CRT) is reflected with a fluorescent lamp or external light There is. In this case, it becomes difficult to see characters and images displayed on the screen of the display device.

  On the other hand, an optical film having an antireflection function is attached to the surface of a display device to reduce the brightness of reflected light from the surface. As this optical film, what laminated | stacked the transparent thin film of the metal oxide which is a low refractive index layer whose refractive index is lower than this transparent film on a transparent film is common (for example, refer patent document 1). In addition, in an optical film in which a plurality of low refractive index layers are laminated, it becomes possible to prevent light reflection in a region as wide as possible in the visible region.

  This optical film functions to prevent reflection using optical interference. For this reason, if the antireflection of light is designed to be optimal in the front direction, the film thickness of the low refractive index layer increases when viewed from the oblique direction, and the reflected light from the oblique direction is colored and uncomfortable. Produce. Therefore, it may be difficult to see characters and images displayed on the screen.

On the other hand, in order to maximize the antireflection effect with respect to the incident angle θ of light into the low refractive index layer, the film thickness of the low refractive index layer is d, the refractive index is n, and the incident wavelength of light is λ. Then, it is said that it is when the following formula (1) is satisfied.
n · d / cos θ = λ / 4 (1)

  According to this formula (1), assuming that the refractive index n of the low refractive index layer is 1.5 with respect to the refractive index of the air layer, the center wavelength λ of visible light is 550 nm, and the incident angle is 0 degree, The film thickness d is 92 nm. With this film thickness, the reflectance is lowest when the incident angle of light is 0 degree.

JP 2003-121606 A

  According to the above calculation formula, if the film thickness of the low refractive index layer is set to 92 nm, the effect of reducing the reflectance can be obtained, but it is difficult to accurately form such a micro film pressure. That is, actually, the film thickness of the low refractive index layer is uneven, the desired interference condition is changed, and the reflection reduction wavelength is shifted. As a result, color misregistration and unevenness of reflected light are observed (first problem).

  In addition, in an optical film that obtains the desired interference condition (antireflection effect) when observed from the front in the center of the screen, both ends of the screen are observed in an oblique direction. The length increases. As a result, color misregistration occurs and is regarded as unevenness of reflected light (second problem).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical film that is visually less colored and can obtain the desired antireflection effect.

  The optical film of the present invention is an optical film in which at least one low refractive index layer having a lower refractive index than that of the transparent support is laminated on the transparent support, and a large number of the optical films are formed on the surface of the uppermost low refractive index layer. The thickness of the low-refractive index layer in the uppermost layer in a state in which the concave portions or a large number of convex portions are randomly formed and the concave portions are filled or in which the convex portions are removed is from the center of the transparent support. It is decreasing toward the department.

  In the optical film of the present invention, an average area of the concave portion or the convex portion in a plan view is in a range of 20 μm * 20 μm to 300 μm * 300 μm.

  In the optical film of the present invention, when the thickness at the center of the transparent support is 1 and the thickness at the end of the transparent support is m, 1.00 <l / m <1.05. Meet the conditions.

  In the display device of the present invention, the optical film is attached to the surface.

  The deflecting plate of the present invention has the optical film attached to the surface.

  According to the present invention, it is possible to provide an optical film that is visually less colored and capable of obtaining the desired antireflection effect.

FIG. 1 is a schematic cross-sectional view of an optical film for explaining an embodiment of the present invention. FIG. 2 is a plan view when the optical film shown in FIG. 1 is viewed from directly above (in the direction of arrow X in FIG. 1).
An optical film 100 shown in FIG. 1 includes a transparent support 101 and a low refractive index layer 102 laminated on the transparent support 101. The transparent support 101 is made of a molded product such as glass or plastic, a sheet, a film, or the like. When plastic is used as the transparent support 101, a surface coating treatment is performed in consideration of various physical properties such as adhesion, chemical resistance, and durability of the low refractive index layer 102. This surface coating treatment requires the same transparency as the transparent support 101.

  For the low refractive index layer 102, an inorganic oxide having a lower refractive index than the transparent support 101, for example, a transparent thin film of a metal oxide is used. The low refractive index layer 102 is formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD) of metal oxide, coating of inorganic fine particles, or the like. In addition, in the case where two or more kinds (for example, MgF2 and SiO2) of the inorganic fine particles are mixed, the refractive index can be changed. A plurality of low refractive index layers 102 may be laminated on the transparent support 101.

  The surface of the low-refractive index layer 102 (the uppermost low-refractive index layer when a plurality of layers are stacked) is formed with a large number of randomly arranged convex portions 103, and a concave portion that is not projected by the large number of convex portions 103 Is a recess 104.

  Since the protrusions 103 are randomly formed, the film thickness of the low refractive index layer 102 varies randomly depending on the location. For this reason, the condition of the above formula (1) is not satisfied depending on the location, and a color shift occurs even when the incident angle is 0 °. However, since the total sum of color shifts is visually recognized, there are a large number of randomly satisfying and unsatisfied parts, resulting in inconspicuous color shifts and less unevenness. Perceived as reflected light. Moreover, when the convex part 103 is formed at random, when the optical film 100 is applied to a display device, moire can be suppressed.

  Furthermore, for the sake of ease of manufacture and ease of explanation, it is assumed that the protruding heights of the large number of protrusions 103 are substantially the same. However, it is also possible to implement a configuration in which there are changes in the protruding heights of the many convex portions 103. The thickness of the low refractive index layer 102 excluding the convex portion 103 (hereinafter simply referred to as the thickness of the low refractive index layer 102) is l at the center of the transparent support 101 and m (<l) at the end. It decreases from the center toward the edge. For this reason, when the end portion of the low refractive index layer 102 is observed from an oblique direction, it is possible to avoid an increase in the optical path length of incident light, and to eliminate a color shift when viewed from the oblique direction. it can.

  The thickness of the low refractive index layer 102 can be obtained as a value of d shown in the above formula (1). First, the incident angle θ of light when observing the optical film 100 is set at an arbitrary position from the center to the end of the transparent support 101 (the incident angle at the center is 0 degree). Then, a value of d satisfying the interference condition at the set incident angle θ is calculated by the equation (1), and the calculated value is set as the thickness of the low refractive index layer 102 at the position. In this way, the thickness of the low refractive index layer 102 can be determined for each arbitrary position from the center to the end of the transparent support 101. Since the incident angle θ increases from the center of the transparent support 101 toward the end, the thickness of the low refractive index layer 102 increases from the center of the transparent support 101 toward the end according to the equation (1). Therefore, it decreases.

  As shown in FIG. 2, the convex portion 103 has, for example, a square shape in plan view, and in the case of an optical film for a 20-inch display device, the average value of the area of each of the numerous convex portions 103 is 20 μm * 20 μm to It is preferably in the range of 300 μm * 300 μm. This is because if the area is too large or too small, the above effect is weakened by the diffraction phenomenon and the color shift becomes conspicuous. In addition, the convex part 103 does not need to be a rectangle, but can be made into a circular shape and other three-dimensional shapes.

  The thickness l of the low refractive index layer 102 at the center of the transparent support 101 and the thickness m of the low refractive index layer 102 at the end of the transparent support 101 are 1.00 <l / m <1.05. When the condition is satisfied, the effect of suppressing color misregistration can be maximized.

Consider a case where an optical film having such a configuration is applied to a display device of HDTV (high vision) type. In the case of an HDTV (high-vision) type display device, an observation distance that is three times the vertical length of the screen (display area) of the display device is recommended as the observation distance at which a sense of reality can be realized. The aspect ratio of the HDTV (high vision) type screen is 9/16. For example, when considering an HDTV with a 9u vertical screen, the distance from the center to the edge of the screen is 8u, and the recommended observation distance is 27u. Here, u is a virtual unit length. In this case, the thickness that maximizes the anti-reflection effect is as follows:
l = λ / (4n)
And m is
m = cos θ · λ / (4n) ≈0.958 · λ / (4n) = 0.958 · l
And
l / m = 1 / 0.958 ≒ 1.043
Is considered to be the optimal condition in a strict sense. However, considering the actual viewing form and taking into account the movement of the observer's head, it is conceivable to extend this condition to a range of l / m: 1.04 to 1.05.

Further, in NTSC, it is known that the screen ratio is 3/4 in the aspect ratio and the recommended observation distance is 5 times the vertical length of the screen. In this case as well,
l / m = 1 / 0.991 ≒ 1.008
Is the optimal condition in the strict sense. Also in this case, considering the actual viewing form, it can be expanded to a range of l / m: 1.00 to 1.01.

Satisfying both HDTV and NTSC is considered a practical and suitable condition.
1.00 <l / m <1.05 can be defined as an appropriate range.

  The optical film 100 described above can be used by being attached to the surface of a display device such as a liquid crystal display device, thereby suppressing reflection on the surface and making it difficult to see characters and figures displayed on the screen. Can be prevented. It is also possible to sell the optical film 100 as an integrated product by attaching it to the surface of a deflection plate used in a display device.

(Second embodiment)
The optical film of the present embodiment has the same cross-sectional view as FIG. 1, and the plan view has a configuration in which the reference numeral 103 and the reference numeral 104 are interchanged in the plan view shown in FIG. In this configuration, a large number of concave portions 104 are formed, and a portion not recessed by the concave portion 104 is a convex portion 103. According to the optical film of the present embodiment, the same effect as that of the optical film of the first embodiment can be obtained by forming a large number of concave portions 104 at random. Hereinafter, a case where such a configuration is adopted will be described in detail.

  The depths of the recesses of the multiple recesses 104 are substantially the same. The thickness of the low refractive index layer 102 in the state where the concave portion 104 is filled (hereinafter simply referred to as the thickness of the low refractive index layer 102) is L (see FIG. 1) at the center of the transparent support 101, and at the end portion. M (<L) (see FIG. 1), which decreases from the center toward the end. For this reason, when the edge part of the low-refractive-index layer 102 is observed from an oblique direction, it is possible to avoid an increase in the optical path length of incident light and to eliminate a color shift when viewed from the oblique direction. .

  The thickness of the low refractive index layer 102 can be obtained as d shown in the above formula (1). First, the incident angle θ of light when observing the optical film 100 is set at an arbitrary position from the center to the end of the transparent support 101 (the incident angle at the center is 0 degree). Then, a value of d satisfying the interference condition at the set incident angle θ is calculated by the equation (1), and the calculated value is set as the thickness of the low refractive index layer 102 at the position. In this way, the thickness of the low refractive index layer 102 can be determined for each arbitrary position from the center to the end of the transparent support 101. Since the incident angle θ increases from the center of the transparent support 101 toward the end, the thickness of the low refractive index layer 102 increases from the center of the transparent support 101 toward the end according to the equation (1). Therefore, it decreases.

  The concave portion 104 has, for example, a square shape in a plan view, and in the case of an optical film for a 20-inch display device, the average value of the area of each of the numerous concave portions 104 is in the range of 20 μm * 20 μm to 300 μm * 300 μm. Is preferred. This is because if the area is too large or too small, the above effect is weakened by the diffraction phenomenon and the color shift becomes conspicuous. In addition, the recessed part 104 does not need to be a rectangle, but can be made into a circular shape and other three-dimensional shapes.

  The condition where the thickness L of the low refractive index layer 102 at the center of the transparent support 101 and the thickness M of the low refractive index layer 102 at the end of the transparent support 101 is 1.00 <L / M <1.05. When the condition is satisfied, the effect of suppressing color misregistration can be maximized. The reason is as described in the first embodiment.

Next, the manufacturing process of the optical film 100 is demonstrated with reference to the process drawing of FIG. Here, a case where the transparent support 101 is plastic will be described.
First, a plastic material 201 that is a material of the transparent support 101 is prepared, and as shown in FIG. 3A, a pressing die 202 that gives a predetermined film thickness variation is pressed and adhered.

  Next, the pressing mold 202 is removed to obtain the transparent support 101 formed into the shape shown in FIG. Subsequently, a low-refractive index material 203 having a refractive index lower than that of the transparent support 101 is formed on the transparent support 101 by a predetermined amount based on the value of d obtained by the equation (1), and this is flattened. To obtain a state as shown in FIG. In this state, the thickness of the low refractive index material 203 decreases from the center to the end of the transparent support 101, and the thickness at any position from the center to the end depends on the incident angle at that position. It is the thickness obtained by calculation according to equation (1). The state shown in FIG. 3C corresponds to a state in which the convex portion 103 is removed in the first embodiment, and corresponds to a state in which the concave portion 104 is filled in the second embodiment.

In the case of making the optical film described in the first embodiment, after the transparent plastic material 203 is cured, particles of the same material as the transparent plastic material 203 are applied to the surface of the transparent plastic material 203, and a large number of convex portions. To complete the production of the optical film 100.
On the other hand, in the case of making the optical film described in the second embodiment, before the transparent plastic material 203 is cured, a large number of recesses 104 are formed on the surface of the transparent plastic material 203 using a pressing die, and then the transparent plastic material 203 is formed. By curing the material 203, the production of the optical film 100 is completed.

The cross-sectional schematic diagram of the optical film for demonstrating embodiment of this invention Plan view of the optical film shown in FIG. Process drawing which shows the manufacturing process of the optical film shown in FIG.

Explanation of symbols

101 Transparent support 102 Low refractive index layer 103 Convex part 104 Concave part

Claims (5)

An optical film in which at least one low refractive index layer having a refractive index lower than that of the transparent support is laminated on the transparent support,
A large number of concave portions or a large number of convex portions are randomly formed on the surface of the uppermost low refractive index layer,
An optical film in which the thickness of the uppermost low refractive index layer in a state in which the concave portion is filled or in which the convex portion is excluded decreases from the center of the transparent support toward the end portion. The optical film according to claim 1,
The optical film which has the average area in planar view of the said recessed part or the said convex part in the range of 20 micrometers * 20 micrometers-300 micrometers * 300 micrometers. The optical film according to claim 1 or 2,
An optical film satisfying a condition of 1.00 <l / m <1.05, where l is the thickness at the center of the transparent support and m is the thickness at the end of the transparent support.   The display apparatus with which the optical film in any one of Claims 1-3 was affixed on the surface.   A deflecting plate having the optical film according to claim 1 attached to a surface thereof.

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