JP3972651B2 - Light scattering film and display device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
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.
[0003]
[Prior art]
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.
[0004]
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 Japanese Patent Application Laid-Open No. 2000-171619 filed by the present applicant is a proposal relating to a light scattering film and a liquid crystal display device.
In the above proposal, a portion having a different refractive index is distributed in an irregular shape / thickness inside the film, thereby forming a shading pattern having a high or low refractive index. A light-scattering film having a structure in which the film is inclined and distributed in the thickness direction is employed.
[0005]
When the light scattering film is used in a liquid crystal display device, the light scattering film is integrated with another member such as a polarizing film or a display screen through an adhesive layer or an adhesive layer (hereinafter referred to as an adhesive layer). In general, it was used after being converted.
In the above configuration, an adhesive layer having optical characteristics different from that of the light scattering film is interposed between the light scattering film and another member (or display screen). Optical design must be performed in consideration of the intervention.
[0006]
In addition, the thickness of the adhesive layer must be constant when integrally laminating.
Furthermore, the number of constituent members is increased by the amount of the adhesive layer, which leads to an increase in cost.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a light-scattering film that has a simple layer structure, provides stable optical characteristics, and can be easily mounted on a display device.
[0008]
[Means for Solving the Problems]
The light scattering film according to the present invention comprises:
The portions with different refractive indices inside the film are distributed in irregular shapes and thicknesses, forming a band-like shade consisting of high and low refractive indices, and in the specific film cross section, the direction in which the band-like shade extends is In a light scattering film having a cross-section that is inclined with respect to the main surface of the film,
The light scattering film is
(A) a bisphenol A type epoxy resin or a brominated bisphenol A type epoxy resin;
(B) a compound having radical polymerizability;
(C) a compound having at least one cationically polymerizable group in the molecule;
(D) A photopolymerization initiator that generates radical species by actinic radiation
Photocuring a photopolymerizable polymer comprising a composition comprising:
In the unreacted state, it contains a photocurable resin (monomer) having adhesiveness, and is characterized by being given adhesiveness by refraining from heat treatment .
[0009]
As the monomer having adhesiveness, an acrylic monomer and / or a silicone monomer is preferable.
[0010]
The photopolymerizable polymer preferably contains an epoxy resin.
[0011]
The light-scattering film according to the present invention is used even if laminated integrally without interposing another surface treatment layer and an adhesive layer or an adhesive layer.
[0012]
As the other surface treatment layer, one type selected from a hard coat layer, an antireflection layer, an ultraviolet absorption layer, an antifouling layer, or a combination of two or more types,
Furthermore, when mounting on a liquid crystal display device, there is a usage form in which the polarizing film is laminated without an adhesive layer or an adhesive layer.
[0013]
A light-scattering film having a structure according to the purpose is put to practical use as a display device by being arranged on the screen of an image display element.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
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.
[0015]
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.
[0016]
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.
[0017]
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).
[0018]
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). .
[0019]
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.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
In the present invention, the light scattering film itself is required to have adhesiveness. Therefore, the photosensitive material (photopolymerizable polymer) constituting the light scattering film has a surface adhesiveness even after exposure recording (production). It is necessary to have.
[0026]
Examples of the photopolymerizable polymer include (A) bisphenol A type epoxy resin or brominated bisphenol A type epoxy resin, (B) a compound having radical polymerizability, and (C) at least one cationic polymerization in the molecule. And (D) a composition having a photopolymerization initiator that generates radical species by actinic radiation.
[0027]
When the photopolymerizable polymer is polymerized, (B) the refractive index of the compound having radical polymerizability is at least one in (A) bisphenol A type epoxy resin or brominated bisphenol A type epoxy resin and (C) molecule. The composition is lower than that of the compound having a cationic polymerizable group.
[0028]
Here, the epoxy equivalent of (A) bisphenol A type epoxy resin or brominated bisphenol A type epoxy resin is preferably in the range of 400 to 5,000. And it is preferable to mix | blend 20-80 weight part of compounds which have (B) radical polymerizability with respect to 100 weight part of (A) bisphenol A type epoxy resin or brominated bisphenol A type epoxy resin.
[0029]
The photopolymerizable polymer as described above often contains an unreacted photocurable resin (monomer) in the exposed and recorded product, and in general, the unreacted photocurable resin (monomer). Heat treatment is carried out for the purpose of moving the polymer to the polymerization portion.
By selecting an unreacted material having an adhesive property as an unreacted monomer, it is possible to impart an adhesive property by refraining from heat treatment on the light-scattering film itself that has been recorded by exposure.
[0030]
Examples of the monomer having tackiness when not reacted include acrylic monomers and silicone monomers. By blending this monomer in an excess amount than usual, the light scattering film itself can maintain the adhesiveness.
[0031]
As shown in FIG. 4, the photopolymerizable polymer 22 as described above is applied onto a base film 23, covered with a cover film 21, and formed into a film. The optical system illustrated in FIG. Record the light scattering pattern.
[0032]
The light-scattering film based only on exposure recording has adhesiveness on the surface of the photopolymerizable polymer 22. Therefore, after peeling the cover film 21 and the base film 23, it has functions other than light scattering due to its own adhesive force. It can be laminated with other films (hard coat layer, antireflection layer, ultraviolet absorption layer, antifouling layer, polarizing film) and the like without an adhesive layer.
[0033]
Or it is also possible to arrange | position the light-scattering film of the state which maintained adhesiveness directly on the screen of an image display element without interposing an adhesive layer.
[0034]
【The invention's effect】
As described above, it is possible to provide a light-scattering film that has a simple layer structure, has stable optical characteristics, and can be easily mounted on a display device.
In the configuration of the present invention, the light scattering film does not need to be optically designed in consideration of the interposition of the adhesive layer, and control such as making the thickness of the adhesive layer constant is unnecessary. The number of components is reduced, leading to cost reduction.
[0035]
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a light scattering film, in which FIG. 1 (a) is a plan view and FIG. 1 (b) is a cross-sectional view.
2A and 2B are explanatory views showing another embodiment of the light scattering film, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view.
FIG. 3 is an explanatory diagram showing an example of an optical system for producing a light scattering film using a random mask pattern.
FIG. 4 is an explanatory view showing a state in which a light scattering pattern is exposed and recorded on a photosensitive film having a photopolymerizable polymer.
[Explanation of symbols]
1. Light scattering film
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
31 ... Antireflection layer
32… Hard coat layer
33… UV absorbing layer
34… Anti-fouling layer

Claims (7)

The portions with different refractive indices inside the film are distributed in irregular shapes and thicknesses, forming a band-like shade consisting of high and low refractive indices, and in the specific film cross section, the direction in which the band-like shade extends is In the light scattering film having a cross-section that is inclined with respect to the main surface of the film, the light scattering film includes: (A) bisphenol A type epoxy resin or brominated bisphenol A type epoxy resin;
(B) a compound having radical polymerizability;
(C) a compound having at least one cationic polymerizable group in the molecule ;
(D) a photopolymerization initiator that generates radical species by actinic radiation ;
(E) When unreacted, a photopolymerizable polymer composed of a photocurable monomer having tackiness is photocured, and when unreacted, it contains a photocurable monomer having tackiness. A light scattering film characterized in that it is given tackiness by refraining from heat treatment. 2. The light scattering film according to claim 1, wherein the adhesive monomer is an acrylic monomer or / and a silicone monomer. The light scattering film according to claim 1, wherein the photopolymerizable polymer contains an epoxy resin. The light-scattering film according to any one of claims 1 to 3, wherein the light-scattering film has a light scattering property, characterized in that the light-scattering film is integrated with another surface treatment layer without interposing an adhesive layer or an adhesive layer. the film. 5. The light scattering property according to claim 4, wherein the other surface treatment layer is one selected from a hard coat layer, an antireflection layer, an ultraviolet absorption layer, and an antifouling layer, or a combination of two or more. With film. A light-scattering film obtained by laminating the light-scattering film according to any one of claims 1 to 5 on a polarizing film without interposing an adhesive layer or an adhesive layer. A display device comprising the light scattering film according to claim 1 arranged on a screen of an image display element.

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