JP2005099281A - Light scattering film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light scattering film which is free from warpage and is free from the problem of a local occurrence of Newton ring or a light source transparency, and which gives visually suitable display when being applied to a display device without any adhesive layer in all the surface. <P>SOLUTION: A light scattering layer made of a photosensitive material is formed on the surface of a transparent support body which is twice or more as thick as the light scattering layer, and is held between resin films having the same quality on front and rear sides. Light scattering layers made of the same kind of photosensitive materials are formed on front and rear surfaces of the transparent support body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light scattering film that has different scattering properties depending on the incident angle of light (or has an incident angle selectivity) and has anisotropy in light scattering characteristics, and the display image can be visually recognized by applying the light scattering film. The present invention relates to a display device that can improve performance (brightness, contrast, etc.) and reduce power consumption of the display device.

  The above-mentioned display device does not require a special light source such as a backlight or edge light, and is a type of “reflective liquid crystal display device” that uses reflected light from ambient light (such as sunlight or indoor illumination light) as display light. And “transmission type liquid crystal display device” of the type having the special light source.

  Further, the present invention can be applied not only to a liquid crystal display device but also to a display device using a self-luminous display element. Hereinafter, the liquid crystal display device will be described as a representative example.

  In a liquid crystal display device, a viewing angle during observation is ensured (that is, the display image is brightly displayed on the front surface of the display device), and the display image can be seen with uniform brightness over the entire display screen. For this purpose, a light scattering film is disposed on the front surface of the apparatus.

Among various viewing angle control films, the anisotropic of light scattering (forward scattering or back scattering, incident angle selectivity, output angle directivity) can be controlled, and the color of display light does not change depending on the observation position Proposals have been made for luminescent scattering films and liquid crystal display devices. (See Patent Document 1)
JP 2000-171619 A.

  In the viewing angle control film according to the above-mentioned proposal, a portion having different refractive indexes is distributed in an irregular shape / thickness inside the film, thereby forming a shading pattern having a high and low refractive index. The light scattering film has a structure in which different portions are distributed in a layered manner inclined with respect to the thickness direction of the film.

  A shading pattern having a high and low refractive index is formed by applying a technique for exposing and recording a speckle pattern.

  When the above light scattering film is used in a liquid crystal display device, the light scattering film is attached to another member such as a polarizing film or a display screen with an adhesive layer or an adhesive layer (hereinafter collectively referred to as an adhesive layer). In general, it is used integrally.

  In the above configuration, since an adhesive layer is interposed over the entire surface of the light scattering film between the light scattering film and another member (or display screen), a backlight (particularly a direct backlight) When applied to a display device having the above, the degree to which the light source can be seen through is high, and the light amount distribution (or the shape of the light source) according to the light source position is likely to be noticeable.

  For this reason, between the light-scattering film and another member (or display screen), the adhesive layer is not interposed over the entire surface, and at least a part of them is separated (the air layer is interposed). Is preferred.

  The above light scattering film has a structure in which a light-sensitive material layer in which a light and shade pattern having a refractive index is formed is laminated on the surface of a light-transmitting substrate (plastic sheet or plastic film). However, when the surface of the substrate and the other member (or display screen) is highly smooth, Newton's ring (interference pattern) may be locally generated along with the adhesion lamination. However, it is easy to cause an undesirable phenomenon as a display device.

  If the base material and the other member (or display screen) are separated over the entire surface so as not to cause Newton's ring, a phenomenon that the light scattering film is warped is caused.

  The cause of the warp is due to the difference in physical properties between the base material and the photosensitive material, and in particular, the cause is largely due to the difference in expansion rate (shrinkage rate) that accompanies an increase (decrease) in temperature inside the display device.

  If the light scattering film is warped inside the display device, a part that adheres and stacks locally with other members (or display screens) is generated, and Newton rings (interference patterns) are also generated. Will cause problems.

  The present invention eliminates the occurrence of warping of the light scattering film, and even when applied to a display device without interposing an adhesive layer over the entire surface, the occurrence of local Newton rings and the light source can be seen through. It is an object of the present invention to provide a light scattering film in which a suitable display is visible without any visible problem.

The light scattering film according to claim 1 of the present invention is:
Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
The light scattering layer has a structure formed on the surface of a transparent support having a thickness of twice or more.

The light scattering film according to claim 2 comprises:
Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
The light scattering layer is configured to be sandwiched between resin films of the same material on the front and back.

The light scattering film according to claim 3 is:
Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
The light scattering layer made of the same kind of photosensitive material is formed on both front and back surfaces of a transparent support.

  The light scattering film is not limited to the light scattering body on which the “volume type speckle pattern” disclosed in JP 2000-171619 A is exposed and recorded, but may be a volume type hologram.

  The light scattering film is prevented from warping, and even when applied to a display device without an adhesive layer over the entire surface, local Newton rings are prevented from being generated, and a suitable display is visually recognized. The

  The present invention will be described below with reference to the drawings. The description relating to the function (optical characteristics) of the light scattering film (synonymous with the light diffusing film) and the production method is common to the above-mentioned JP-A-2000-171619.

  FIG. 1 shows a light scattering film 1 in which portions having different refractive indexes are distributed in irregular shapes and thicknesses, and a light and shade pattern having a high and low refractive index (represented in black and white in the figure) is formed. FIG. 1A is a plan view and FIG. 1B is a cross-sectional view.

  As can be seen from FIG. 1A, the shape of the portion having a different refractive index is horizontally long. Further, as can be seen from FIG. 1B, the portions having different refractive indexes are structured in a layered manner inclined with respect to the thickness direction of the film.

  In FIG. 1, the refractive index distribution is uniform (the color does not change in the inclined direction) in the direction in which the portions having different refractive indexes are inclined in layers.

  2A and 2B are explanatory diagrams showing a light scattering film 1 according to another embodiment, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view. In FIG. 2, the shape of the portion with different refractive index is vertically long, and the distribution of the refractive index is irregular in the direction in which the portion with different refractive index is inclined like a layer (the color changes even in the inclined direction). Is).

  First, the optical characteristics of the light scattering film of FIGS.

  Light scattering occurs for light incident at an angle along the tilt direction in which the portions having different refractive indices are distributed in layers (in the direction of arrow 2 in the figure, which forms an angle θ from the normal of the film). .

  For light incident at an angle perpendicular to the tilt direction (the direction of arrow 3 in the figure), it functions as a simple transparent film, and the incident light is emitted without being scattered.

  Next, considering the plan view, if the shape of the part with different refractive index is vertically long (or horizontally long), if light incident on that part is scattered and emitted, the light emitted from each part The scattering characteristics have anisotropy that is horizontally long (or vertically long).

  In FIG. 1, since the shape is horizontally long, the emitted light is scattered vertically. In FIG. 2, since the shape is vertically long, the emitted light is scattered horizontally.

  Hereinafter, an example of means for producing the light scattering film of the present invention will be described. The light scattering film of the present invention can be produced by optical exposure means.

  FIG. 3 is an explanatory view showing an example of an optical system for producing the light scattering film having the structure shown in FIG. 1 using a random mask pattern.

  The ultraviolet light emitted from the UV light source 15 is converted into parallel light 17 by the collimating optical system 16 and irradiated on the mask original plate 18. The mask original plate 18 includes a glass substrate 20 and a chrome pattern which is a random pattern.

  A photosensitive material 19 is disposed in close contact with the surface of the mask original plate 18 opposite to the UV irradiation side, and the pattern of the mask original plate 18 is exposed and irradiated to the photosensitive material 19.

  At this time, the UV parallel light 17 and the mask original plate 18 are inclined at a predetermined angle α as shown in the figure, so that the pattern exposure is performed at a predetermined angle in the photosensitive material 19. Since this angle corresponds to the inclination angle (that is, the incident angle-dependent scattering peak angle θ) of the portion having a different refractive index in the light scattering film, the angle is 0 to 60 ° depending on the application. It is appropriately selected within a range of degree.

  The photosensitive material 19 used here is a photosensitive material that can be recorded with the degree of refractive index modulation between the exposed portion and the unexposed portion of UV light, and has a higher resolving power than the gray pattern to be recorded, and has a thickness of The material must be capable of recording a pattern in the direction.

The above is the explanation of the light scattering layer by the volume type speckle pattern. However, in the present invention, the light scattering film to be produced needs to be configured to prevent warping, and the photosensitive material (photopolymerizable) It is necessary to explain in relation to the constituent elements other than (polymer).
<Embodiment 1>
The light scattering film according to claim 1 has a structure in which the light scattering layer is formed on the surface of the transparent support having a thickness of twice or more.

  In the light scattering film 50 according to this embodiment, as illustrated in FIG. 5, a light scattering layer (photosensitive material) 40 having a thickness of 20 μm is laminated on one surface of a transparent support 30 having a thickness of 50 μm.

In the case of the configuration shown in the figure, even if the light scattering layer (photosensitive material) 40, which is relatively large in expansion or contraction due to temperature change, is deformed (expanded or contracted), the thick transparent support 30 is not affected As a result, the light scattering film (whole) 50 can be regarded in the same manner as the case of the single transparent support 30, and the difference between the expansion rates (or contraction rates) of the two layers can be considered. No warpage due to.
<Embodiment 2>
The light scattering film according to claim 2 is configured such that the light scattering layer is sandwiched between resin films of the same material on the front and back sides.

  In the light scattering film 50 according to this embodiment, a light scattering layer (photosensitive material) 40 is sandwiched between transparent supports 31 and 32 as illustrated in FIG.

In the present embodiment, it is not necessary to make the thickness of the transparent supports 31 and 32 twice or more that of the light scattering layer (photosensitive material) 40 as in the first embodiment. Even if any one of the transparent supports is affected by the deformation, it is sufficient that the thickness is balanced so that the other transparent support is relaxed.
<Embodiment 3>
The light scattering film according to claim 3 has a structure in which light scattering layers made of the same kind of photosensitive material are formed on both front and back surfaces of the transparent support.

  In the light scattering film 50 according to this embodiment, light scattering layers (photosensitive materials) 41 and 42 are laminated on both surfaces of a transparent support 30 as illustrated in FIG.

  In the case of the configuration shown in the figure, even if one of the light scattering layers (photosensitive material) is deformed, the other light scattering layer is similarly deformed. As a result, the light scattering film (whole) 50 is a single layer. It can be considered in the same manner as the case of the light scattering layer, and no warping occurs.

  In the present embodiment, there is an explanation in the case where there are two light scattering layers having an anisotropic light scattering function. However, in order to prevent the light scattering film (whole) from warping, one light scattering layer has anisotropic light scattering. It is not necessary to have a function, and the presence of a layer made of the same material as the light scattering layer is sufficient because the deformation of the light scattering layer can be offset.

  In the first to third embodiments described above, the description is related to the light scattering layer in which the volume speckle pattern is exposed and recorded. However, in the present invention, a volume hologram having an anisotropic light scattering function may be used. Is possible.

  Further, the cause of warpage is the process of exposing and recording a volume speckle pattern (or volume hologram) on a transparent support on which a photosensitive material layer is formed when manufacturing a light scattering film. There is also a cause associated with the curing and shrinkage of the photosensitive material layer.

  In the light scattering film manufacturing process shown in FIG. 3, the mask pattern is exposed and recorded on the sheet of photosensitive material 19, but in the case of continuous mass production of the light scattering film, Since production by a two-roll method is desired, a method of continuously supplying a photosensitive film formed with a photosensitive material layer to an exposure recording unit is employed.

  As shown in FIG. 4, the light scattering film having the structure described in the second embodiment is obtained by laminating a transparent support 32 on the surface of the photosensitive material layer 40 with respect to the photosensitive film that has passed through the exposure recording section. It will be.

  In laminating the transparent support 32, an adhesive layer is interposed or an easy adhesion process to the transparent support 32 is performed as necessary.

It is explanatory drawing which shows a light-scattering film (light-scattering layer), FIG. 1 (a) is a top view, FIG.1 (b) is sectional drawing. It is explanatory drawing which shows a light-scattering film (light-scattering layer), FIG. 2 (a) is a top view, FIG.2 (b) is sectional drawing. Explanatory drawing which shows an example of the optical system which produces a light-scattering film (light-scattering layer) using a random mask pattern. Explanatory drawing which shows embodiment of a light-scattering film. Explanatory drawing which shows embodiment of a light-scattering film. Explanatory drawing which shows embodiment of a light-scattering film. Explanatory drawing which shows embodiment of a light-scattering film.

Explanation of symbols

1. Light scattering film (light scattering layer)
15 ... UV light source
16 ... Collimating optics
17 ... Parallel light
18 ... Mask original
20 ... Glass substrate
21 ... Cover film
22 ... Photopolymerizable polymer
23… Base film
30, 31, 32 ... Transparent support
40, 41, 42 ... Light scattering layer
50 ... Light scattering film

Claims (4)

Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
The light scattering film is characterized in that the light scattering layer is formed on the surface of a transparent support having a thickness twice or more of the thickness. Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
The light scattering film is characterized in that the light scattering layer is sandwiched between resin films of the same material on the front and back. Optical anisotropy that changes the degree of scattering of the incident light to the light scattering layer and the direction and range of light scattering depending on the distribution of parts with different refractive indexes inside the light scattering layer made of photosensitive material In a light scattering film having properties,
A light scattering film, wherein the light scattering layer made of the same kind of photosensitive material is formed on both front and back surfaces of a transparent support.   The light scattering film according to claim 1, wherein the light scattering layer is a volume hologram.