JP4303923B2 - Visibility improving sheet and display using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is installed on the front of the display, and the performance of the display, in particular, the function of preventing the deterioration of the performance due to the contrast reduction, glare, image reflection, etc. when the external light hits the display, The present invention relates to a visibility improving sheet having a function of widening a viewing angle by suitably diffusing effective light and a display using the same.
[0002]
As a visibility improving sheet, in addition to a surface antireflection sheet, a surface low reflectance sheet, an antiglare sheet, etc. that devised the external light reflection performance of the surface, a transparent sheet having light transmittance called a louver Known is one in which a light absorbing layer is provided in a part of the layer in the thickness direction of the sheet to provide a function of improving contrast.
[0003]
Among these visibility-improving sheets, the present invention is a layer (hereinafter referred to as a louver) in which a light absorption layer is provided in the substantially thickness direction of the sheet and the other part is a light transmission part that transmits light from the display (hereinafter referred to as the first). It is related with the visibility improvement sheet | seat which has the function to improve the contrast characterized by having provided 1 layer).
[Prior art]
[0004]
FIG. 10 is an explanatory diagram of the prior art. In FIG. 10, reference numeral 3 denotes a display such as liquid crystal, PDP, organic EL, CRT, rear projection. When these displays are used under conditions of strong external light such as outdoors, there is a problem that the external light is reflected by the display and the contrast of the image is lowered to impair visibility. In order to solve this problem, a method of forming a light absorption layer on a part of a transparent sheet layer and bonding it to the front surface of the display is well known. The light absorbing layer 22 is provided in a substantially thickness direction of the sheet, and the other part is formed of a light transmitting portion 21 that transmits light from the display, and the function of absorbing external light that strikes the display obliquely and preventing a decrease in contrast. The one having the is called louver (same meaning as the first layer of the present invention).
[0005]
In FIG. 10, the louver 2 is bonded to the surface of the display 3. The light absorption layer 22 is a thin layer. The light absorption layer may be formed in a substantially vertical direction from the display, and may extend linearly in the vertical direction of FIG. As shown in FIG. 9, when the entire visibility improving sheet is viewed from the observation side, the light absorption layer 23 may be formed in (a) horizontal direction, (b) vertical direction, or (c) lattice shape. Alternatively, (d) the transmission part 21 that transmits light from the display may be cylindrical and the other part may be the light absorption layer 24. In any case, it suffices that a part of the sheet is a light absorbing layer and the other part is a light transmitting part that transmits light from the display.
[0006]
Here, since the amount of external light 5 absorbed by the light absorption layer 22 and reflected by the display 3 is reduced, a reduction in contrast due to external light is reduced. However, as can be seen from FIG. 10, not only the external light but also the video light 41 emitted from the display is absorbed by the light absorption layer 22, and the brightness of the display is lowered.
[0007]
FIG. 11 is a diagram illustrating a state in which the image light of the display is absorbed by the light absorption layer 22 in a layer including the light absorption layer. In part (a) of FIG. 11, the light 41 of the display from the center in the width direction of the light transmission part (same as the center of the light absorption layer 22 formed continuously and the adjacent light absorption layer) is the light absorption layer 22. In FIG. 11B, the display light 42 from the end in the width direction of the light transmitting portion (same as the vicinity of the light absorbing layer 22) is absorbed by the light absorbing layer 22. Is shown. As shown in FIG. 11A, the light 41 of the display that emerges from the center in the width direction of the light transmission portion is 0 ° in the direction perpendicular to the display, and the light between −α1 and + α1 is the light absorption layer 22. However, the other light (light from −90 ° to −α1 and + α1 to + 90 °) is absorbed by the light absorption layer 22 and becomes lost light. Here, α1 is the width L of the light transmission part and the depth of the light absorption layer (same as the thickness of the light transmission part) D.
α1 = tan ⁻¹ (L / 2D)
It is represented by
Next, when the display light in FIG. 11B is emitted from the end in the width direction of the light transmission part of the layer including the light absorption layer 22, light in the range of 0 ° to α2 becomes effective light, Light at other angles becomes lost light. Where α2 is
α2 = tan ⁻¹ (L / D)
It is represented by
As can be seen from this equation, when L / D is not large, 2 × α1≈α2. Therefore, the effective light range is 2 × α1 in the left side explanatory diagram and α2 in the right side explanatory diagram, and the range of the angular range is substantially equal. It can be seen that the effective light from the display from the center to the end of the light transmission part has an angular width of approximately 2 × α1. For this reason, when the image light from the display is emitted at an angle or more, lost light is generated and a bright image cannot be delivered to the observer.
[0008]
[Problems to be solved by the invention]
In the present invention, as described above, in the conventional visibility improving sheet (louver) having a function of preventing a decrease in contrast due to external light, the image light from the display is absorbed by the light absorption layer 22 and is lost. There is a part, and this loss light (amount) is reduced, and a bright image is sent to the observer.
[0009]
[Means for solving the problems]
The first invention is a visibility improving sheet that is bonded to the front surface of the display to enhance the visibility of the display, and the visibility improving sheet is composed of two or more layers in the thickness direction from the display surface toward the observation side, A first layer composed of a light absorbing layer formed in a substantially thickness direction of the visibility improving sheet, a light transmitting portion for transmitting light from the display, and another layer of at least one other layer; The refractive index of the light transmitting portion that transmits light from the display of the first layer is higher than the refractive index of the second layer provided on the display surface side of the first layer sharing the interface with the first layer. refractive index der is, and, the second layer consists of an adhesive, and characterized in that bonding the layer of second so that the display on the side of the display.
By forming a second layer having a refractive index lower than the refractive index of the light transmitting portion that transmits the light of the first layer on the display side of the layer (louver) including the light absorption layer as the first layer Brightness is maintained while maintaining the function of reducing the loss of light from the display without changing the function of absorbing external light, increasing the effective light ratio (transmittance), and preventing the deterioration of contrast due to external light Video could be provided to the observer.
[0010]
The second invention is characterized in that a third layer having a function of diffusing light is provided on the surface on the observation surface side of the visibility improving sheet of the first invention. The light diffusing layer as the third layer only needs to have a function of diffusing light, and may be a layer with almost no thickness obtained by matting the surface of the louver as the first layer. The lenticular lens layer Or a light diffusing agent layer.
[0011]
The third invention is characterized in that a low reflective layer or a non-reflective layer that lowers the reflectivity is formed as a third layer on the surface on the observation surface side of the visibility improving sheet in the first invention. .
A fourth invention is the visibility improving sheet according to claim 3, wherein the light absorption layer is formed in a horizontal direction, a vertical direction, or a lattice shape.
Moreover, 5th invention is a visibility improvement sheet | seat of any one of Claim 1 thru | or 4, Comprising: An aperture ratio shall be 80% or more.
[0012]
The sixth invention is characterized in that the above-described visibility improving sheet is bonded to a display unit.
A seventh invention is a display according to claim 6, wherein the visibility enhancement sheet Ru der which is characterized in that is bonded to the surface of the PDP on the viewer side.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the principle of the visibility improving sheet 1 of the present invention. In the visibility improving sheet 1 of the present invention, a layer 13 having no light absorbing layer is provided as a second layer on the display side of the first layer including the light absorbing layer 12 so as to share the interface. The refractive index of the second layer 13 without the light absorption layer is smaller than the refractive index of the light transmitting portion 11 that transmits light from the display in the first layer. At this time, the display light is absorbed as follows. Part (a) of FIG. 1 shows the state of display light generated at the center of the light transmission part of the first layer as in part (a) of FIG. In this portion, light having an angle of -α1 to + α1 becomes effective light from the interface 14 between the first layer 2 and the second layer 13 to the light transmitting portion 11 in the first layer, and other light becomes loss light. This is the same as the conventional example of FIG. This is because the structure of the first layer 2 is the same in FIG. 11 (a) and FIG. 1 (a). By the way, in order to emit light from the interface 14 at an angle α1, it is necessary to enter the interface 14 with β1 satisfying the following expression.
β1 = sin ⁻¹ ((n2 / n1) sin (α1))
n1 is the refractive index of the second layer, and n2 is the refractive index of the light transmitting portion of the first layer. Here, since n2> n1, β1> α1. Further, the outgoing angle of the incident angle smaller than β1 with respect to the interface 14 is smaller than α1. Accordingly, display light having an angle of −β1 to + β1 becomes effective light in the vicinity of the central portion of the light transmitting portion. Since β1> α1, the amount of display light that is more effective in FIG. 1, that is, the present invention is larger than that in FIG. 11, that is, the conventional one. On the other hand, the absorption of external light hardly changes because it is almost determined by the layer including the light absorption layer. Therefore, the brightness of the display can be increased without changing the absorption of external light.
[0014]
1 (a) is near the center of the light transmission part, and this is the same at the end of the light transmission part (near the light absorption layer) in FIG. 1 (b). ,
β2 = sin ⁻¹ ((n2 / n1) sin (α2))
Thus, light from 0 ° to β2 becomes effective light. As described above, since 2 × α1≈α2, 2 × β1≈β2. Throughout the display, the effective light angle is 2 × α1 in the case of the prior art, and 2 × β1 in the present invention, and the light emission of the display has a spread of ± γ, and γ> β1 and β1> α1, If the brightness is isotropic within this range, the ratio of effective light in the prior art is α1 / γ, and in the case of the present invention is β1 / γ, and the efficiency of the present invention is β1 / α1 times that of the prior art. It becomes. Therefore, since β1> α1, the efficiency is 1 or more, which shows that the present invention is effective.
[0015]
A high refractive index material that can be used as the light transmission portion 11 of the first layer and a low refractive index material of the second layer 13 formed on the display side will be examined. A larger refractive index difference between the two is desirable because the effect of the present invention due to refraction is greater, but when a practical material is studied, the material of the high refractive index layer 11 has a refractive index of about 1.5 to 1.65. Selected from polycarbonate resin, polystyrene resin, acrylic resin, epoxy resin, etc., and as the material of the layer 13 of the low refractive index material, a fluororesin having a refractive index of about 1.3 to 1.4 is selected. As a result, the refractive index difference is about 0.2 to 0.3.
[0016]
In the above description, the case where the display and the first layer including the light absorption layer are close to each other has been described. However, even if there is a distance between the first layer 2 and the display 3 as shown in FIG. is there. This is because even when the display is not in contact with the layer including the light absorption layer, it can be regarded as optically the same as the portion where the light absorption layer disappears, which emits light at 6 shown in FIG. Because. This is because the light traveling in the α direction from one of the 6 lines is considered to be the light emitted at the same angle α from the point where the straight line extending in the display direction intersects the display 3.
[0017]
In the present invention, the image light from the display is set to a diffusion range within an angle range in which the absorption in the light absorption layer is reduced, and is allowed to pass through the light transmission portion 11 of the first layer 2, and then the first The light diffusion range can be widened by refraction or the like on the observation side surface of the layer.
[0018]
Therefore, when the present invention is applied to a light projection method such as a rear projection display that is not uniform in all directions and can be limited to a certain angle range, only the contrast can be improved without narrowing the viewing angle. it can. In particular, if the vertical light spread method is easily controlled by a screen like the above-mentioned rear projection display, the vertical light spread method is set in advance to an angle range that passes through the first layer ( If γ is smaller than α1 or β1, the contrast can be improved without reducing the light efficiency. At this time, if the viewing angle in the vertical direction is insufficient, a minute uneven layer is formed on the observation side surface of the first layer as in the second aspect of the invention, and light is diffused slightly in the vertical direction there. You can do that. This layer may be a fine lenticular lens layer.
[0019]
The present invention can be modified in various ways, and as shown in FIG. 5, an uneven layer 15 may be provided as a third layer on the observation side surface in order to increase the viewing angle. A non-reflective layer or a low-reflective layer may be formed by multilayer coating a material having a refractive index lower than the refractive index of the outermost surface material of the visibility improving sheet with a thickness of about ¼ of the wavelength of visible light rays. . Further, the cross section of the light absorption layer is not a narrow rectangle, but may be a trapezoidal shape or other shapes as shown in FIG. In addition, the present invention improves the visibility of the display, and in particular, prevents a decrease in visibility (such as a decrease in contrast) due to external light. Therefore, as already mentioned, In consideration of the direction in which external light is directed to the display and the direction of the viewer of the display, the absorbing layer 23 is (a) horizontal when the entire visibility improving sheet is viewed from the observation side as shown in FIG. Or (c) may be formed in a lattice shape, or (d) the light transmitting portion 21 that transmits light from the display is cylindrical, and other portions absorb light. It may be the layer 24. Furthermore, although the light absorption layer in the visibility improving sheet has been described in the case where it is provided perpendicular to the display surface, the display usage environment (direction in which external light hits the display, the direction of the main observer ( If the position) is clear, the light absorption layer is made with a certain inclination from the vertical direction of the display according to the conditions, and the balance between the improvement of the external light absorption rate and the viewing angle (diffusion) angle is achieved. You can also.
[0020]
FIGS. 8A and 8B assume a case where the large display device is above the observer using the display and the external light 5 (assuming sunlight) comes from above. . In this case, since the external light 5 is only from above, the light absorption layer 12 may be installed in a direction extending in the horizontal direction as shown in FIG. Further, the light absorbing layer 12 in the visibility improving sheet is perpendicular to the display surface as shown in FIG. 8C in order to improve the absorption of the external light 5 and to favor the light diffusion toward the viewer. Rather, it can be formed slightly downward. Thus, the light absorption layer is not limited to the vertical direction from the display surface.
[0021]
[Example 1]
1 having the configuration of FIG. 1 = 0.36 mm
D = 1mm
The width of the light absorption layer 12 of the first layer: 0.02 mm
Arrangement of light absorption layer of first layer: FIG. 9A
Thickness of the second layer (low refractive index layer) 13: 0.1 mm
Refractive index of the second layer (low refractive index layer) 13: n = 1.35 (fluororesin)
Refractive index of the light transmission part 11 of the first layer: n = 1.65 (modified acrylic resin)
α1 = 10.2 ° α2 = 19.8 °
β1 = 12.5 ° β2 = 24.5 °
β1 / α1 = 1.23 β2 / α2 = 1.24
Therefore, if the brightness of the display is isotropic and the spread angle is larger than β2 (= 24.5 °), the brightness is improved by about 23% in the first embodiment.
[0022]
[Method of creating embodiment 1]
A plate-like portion corresponding to the light absorption layer portion of the first layer is coated on the surface member of the acrylic resin liquid crystal display with a fluororesin 100 μm thick as the second layer (low refractive index layer). The modified acrylic resin is cast (polymerization molding) using a mold having A solvent-based black ink is embedded in the groove portion thus formed as a light absorption layer by a wiping method and dried with hot air. The surface member thus produced was set (bonded) to the surface of a 15-inch liquid crystal display.
[0023]
The same method as in Example 1 except that the UV curable modified acrylic resin having the same refractive index (1.65) as the material of the light transmitting portion of the first layer was coated at the position of the second layer and UV cured. A comparative sample was created. The brightness of the display, toward the viewing surface of the illuminance meter display front side, was measured, it brightened from 50 lm / m ² of the comparative example to 60 lm / m ² of Example 1.
[0024]
[Example 2]
3 having a sheet configuration shown in FIG. 3, in which a first layer is formed on a polyester film 7 and bonded to a display with a low refractive index adhesive 8.
Polyester film thickness: 0.1 mm (refractive index n = 1.6)
Thickness of the second layer (low refractive index adhesive): 0.03 mm (refractive index n = 1.3)
First layer thickness D1 = 0.6 mm
Refractive index of light transmission part of first layer: n = 1.6
Depth D of light absorption layer of first layer = 0.57 mm
Width L of light transmission part of first layer = 0.4 mm
The width of the light absorption layer of the first layer: 0.02 mm
Arrangement of light absorption layer of first layer: FIG. 9A
α1 = 15.9 ° α2 = 29.7 °
β1 = 19.8 ° β2 = 37.6 °
β1 / α1 = 1.25 β2 / α2 = 1.27
Therefore, if the brightness of the display is isotropic and the spread angle is larger than β2 (= 37.6 °), the brightness is improved by about 25% in the second embodiment.
[0025]
[Method of creating embodiment 2]
Using the reverse mold of the light transmission part of the first layer on the polyester film, the shape of the light transmission part of the first layer is formed with UV resin, and then black ink is applied to the groove part by the above wiping method Was coated on the opposite side of the polyester film with a low refractive index adhesive 30 μm thick as a second layer to prepare a visibility improving sheet. This visibility improving sheet 1 was bonded to a 40-inch PDP surface 61 as shown in FIG.
[0026]
A comparative sample was prepared in the same manner as in Example 2 except that the modified acrylic resin adhesive having the same refractive index (1.6) as that of the material of the light transmitting portion of the first layer was coated at the position of the second layer. did. The brightness of the display, toward the viewing surface of the illuminance meter display front side, was measured, brightened from 100lm / m ² of the comparative example to 125lm / m ² of Example 2.
[0027]
[Example 3]
The sheet structure shown in FIG. 4 is the same as that of Example 2 except that the first light absorption layer 12 has a wedge shape.
Width L of light transmission part of first layer = 0.4 mm
Width (front side) W1 = 0.08 mm of the light absorption layer of the first layer
The width (bottom side) of the light absorption layer of the first layer W2 = 0.02 mm
The portion other than the shape of the light absorption layer of the first layer is the same as that of the second embodiment, and the change in the thickness of the light absorption layer has almost no effect. Will improve. This visibility improving sheet was bonded to the surface of a 2-inch organic EL. Was prepared in the same manner as in Comparative Sample Example 2, the brightness of the display toward the viewing surface of the illuminance meter display front side, was measured, from 40 lm / m ² of the comparative example to 50 lm / m ² of Example 3 It became brighter. With such a shape, the light absorption part shape of the first layer is tapered and a merit that mold release becomes easy when the first layer is formed is additionally generated.
[0028]
[Example 4]
The surface on the observation surface side of the visibility improving sheet of Example 3 is formed as a surface mat 15 having a half value angle of diffusion of 5 °, and the vertical diffusion (1/10 angle value) is 20 ° as shown in FIG. The first light absorption layer was bonded to the surface of the screen 71 of the rear projection display so that the first light absorption layer was aligned in the horizontal direction as shown in FIG. As shown in FIG. 7 (b), a screen 77 and a member 77 on which the visibility improving sheet 1 is bonded are installed at the position of the screen of the rear projection display 70 (the projector 72 and the mirror 73 are installed in the housing). Carried out. The brightness of the display hardly changed, the contrast was improved, the vertical viewing angle was sufficient, and no reflection that disturbed the image was observed.
[0029]
[Example 5]
The configuration was the same as in Example 1. However, the low refractive index layer of the second layer was a low refractive index adhesive layer. The first layer is produced by coextrusion of a light-transmitting part and a light-absorbing layer with two layers of modified acrylic resin, the sheet is laminated at a temperature equal to or higher than the thermal softening point, heat-sealed, and then 1 mm Cut to a thickness and made. On top of that, a low refractive index pressure-sensitive adhesive was coated as a second layer to form a visibility improving sheet, which was bonded to the display.
[0030]
[Example 6]
A visibility improving sheet having the configuration of Example 2 was prepared. Separately from this, a low reflective layer (reflectance: 0.2%) of multilayer deposition was formed on one side of a 0.05 mm thick polyester film. This polyester film was bonded to the first surface side of the visibility improving sheet having the configuration of Example 2.
[0031]
A comparative sample was prepared in the same manner as the brightness comparison in Example 2. The brightness of the display, toward the viewing surface of the illuminance meter display front side, was measured, brightened from 100lm / m ² of the comparative example to 125lm / m ² of Example 2. Furthermore, the reflection of external light such as fluorescent lights was not noticeable.
[0032]
【The invention's effect】
According to the first invention, the second layer made of a material having a refractive index smaller than the refractive index of the light transmitting portion of the first layer of the visibility improving sheet is provided between the display and the visibility improving sheet of the prior art. By providing, it is possible to reduce the proportion of the image light emitted from the display that is absorbed by the light absorption layer and lost, and a bright image can be provided to the viewer.
In the second invention, a light diffusion layer such as a fine concavo-convex layer is provided on the observation-side surface of the visibility improving sheet, and the viewing angle limited by the visibility improving sheet is expanded, which is good for many observers. Can now be provided.
In 3rd invention, the low reflective layer and the non-reflective layer were provided in the observation side surface of the visibility improvement sheet | seat, and the performance of the visibility improvement sheet | seat which provides a bright image | video could be improved further.
In 4th invention, the said visibility improvement sheet | seat was mounted | worn to the display display part, the display with high visibility was provided, and it came to be able to provide many observers with the image | video which was bright and excellent in visibility.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a visibility improving sheet according to the present invention.
FIG. 2 is an explanatory diagram when the display surface of the present invention is separated from the first layer. FIG. 3 is an explanatory diagram of a form of Example 2 of the visibility improving sheet of the present invention.
FIG. 4 is an explanatory diagram of a form of Example 3 of the visibility improving sheet of the present invention.
FIG. 5 is an explanatory diagram of a three-layer structure in the visibility improving sheet of the present invention.
FIG. 6 is an explanatory diagram of a state in which the visibility improving sheet of the present invention is bonded to a liquid crystal display.
FIG. 7 is an explanatory diagram illustrating a configuration of a display and a state in which a visibility improving sheet according to a fourth embodiment of the present invention is bonded to a rear projection display screen.
FIG. 8 is an explanatory diagram of an example of a visibility improving sheet in which the light absorption layer of the first layer is inclined downward from the vertical surface of the display.
FIG. 9 is an explanatory diagram (exemplary) of the position of the light absorption layer of the first layer as viewed from the observation side.
FIG. 10 is an explanatory diagram of a visibility improving sheet according to a conventional technique.
FIG. 11 is an explanatory diagram of an effective portion and a loss portion of video light from a display on a visibility improving sheet according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Visibility improvement sheet | seat 2 of this invention 1st layer (layer containing a light absorption layer)
3 Display 5 External light 8 Sun 9 Floor 11, 21 Light transmitting layer 12, 22, 23, 24 through which light from display passes (L is pitch, D is height)
13 Second layer (low refractive index layer)
14 Interface between the first layer and the second layer (low refractive index layer) 15 Light diffusion layer 19 Direction of the viewer as viewed from the display 41, 42 Image light from the display 60 Display housing 61 Display display 70 Rear projection display 71 Rear projection display screen 72 Projector 73 Mirror 77 The visibility improving sheet of the present invention is bonded to the screen.

Claims (8)

In the visibility improving sheet that is bonded to the front surface of the display to enhance the visibility of the display, the visibility improving sheet is composed of two or more layers in the thickness direction from the display surface toward the observation side. A light absorption layer formed in the thickness direction, a first layer comprising a light transmission part that transmits light from the display, and another layer of at least one other layer, from the display of the first layer refractive index of the light transmitting portion for transmitting light, Ri higher refractive index der than the refractive index of the second layer provided on the display surface side of the first layer that share the first layer and the interface, And the said 2nd layer consists of adhesives, and this 2nd layer is bonded together so that it may become a display display part side, The visibility improvement sheet | seat characterized by the above-mentioned.   The visibility improving sheet according to claim 1, wherein a third layer having a function of diffusing light is provided on the surface on the observation surface side of the visibility improving sheet.   2. The visibility improving sheet according to claim 1, wherein a low reflection layer or a non-reflective layer that lowers the reflectance is formed as a third layer on the surface on the observation surface side of the visibility improving sheet.   4. The visibility improving sheet according to claim 3, wherein the light absorption layer is formed in a horizontal direction, a vertical direction, or a lattice shape.   The visibility improving sheet according to any one of claims 1 to 4, wherein the opening ratio is 80% or more.   6. A display comprising the display display unit and the visibility improving sheet according to any one of claims 1 to 5 bonded together so that the second layer is on the display display unit side. The display according to claim 6, wherein the visibility improving sheet is bonded to a surface on the viewer side of the PDP.   The display according to any one of claims 6 to 7, wherein the bonding is performed using an adhesive material.

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