Patent Application
20060104084
1. Field of the Invention
The present invention relates to a view angle controlling sheet to be disposed between the light source and the liquid crystal panel of a liquid crystal display apparatus, having the function of preferably controlling the performance of the liquid crystal display apparatus, in particular, the light beam from the light source of the liquid crystal display, and a liquid crystal display apparatus using the same.
2. Description of the Related Art
According to a liquid crystal display apparatus, in general, a wide view angle is preferred so that a preferable image can be obtained wherever the observer is.
On the other hand, in the case of working in a commuter train or according to a liquid crystal display installed at a public place such as an ATM, it is inconvenient to have the screen peeped from the other people. In this case, a peep preventive function for ensuring the sight of only the observer of the liquid crystal display while blocking the other's sight so as to protect the privacy is called for. Moreover, according to a vehicle mounting type liquid crystal display apparatus such as a car navigation system, there is the phenomenon of blocking the sight by the reflection of the liquid crystal display apparatus screen onto the window glass at night, or the like so that the reflection preventive function is called for and the control of the light beam output angle is desired. To such a demand, a louver type view angle controlling sheet as shown in for example
However, according to the conventional louver type view angle controlling sheet, since it has a configuration of merely forming the colored layer and the transparent layer alternately with a rectangular louver cross sectional shape so as to merely absorbing the light beam from the oblique direction by the colored layer without obtaining the converging effect of converging the light beam from the light source to a targeted output angle with a large light amount loss and a low light beam utilization efficiency so that a problem arises in that only the limited view angle control is enabled.
Furthermore, according to the production method mentioned in the patent article, the transparent portion and the colored portion should be laminated until a desired thickness is obtained, and thus it has the shortcomings of a poor productivity and a high production cost. Moreover, an extremely sophisticated and troublesome work of planning the obtained block to an even thickness after laminating the transparent portion and the colored portion so that a large number of steps and a bulky apparatus are required, and thus a problem is involved in that a gigantic cost is needed.
Accordingly, an object of the present invention is to provide an inexpensive view angle controlling sheet to be disposed between the light source and the display panel of a liquid crystal display apparatus, effective for limiting the light beam output angle for the peeping prevention, the reflection prevention, or the like while providing a high light beam transmittance to the observer side so as to provide the excellent light utilization efficiency.
A view angle controlling sheet of the present invention has light transmissible resins with a trapezoidal shape by a predetermined interval on the surface of a light transmissible base material so as to provide a lens part, and filling a wedge shaped gap between the adjacent trapezoids (hereinafter it is referred to as a “wedge part”) with a light absorbing material so as to form a light absorbing part.
A first aspect of the present invention is a view angle controlling sheet to be disposed between the light source and the liquid crystal panel of a liquid crystal display apparatus, wherein the view angle controlling sheet has lens parts having a trapezoidal cross sectional shape arranged by a predetermined interval and the wedge parts between the adjacent lens parts is filled with a light absorbing material such that the wedge part has the top end disposed to the observer side and the bottom surface to the light source side and a light reflection layer provided to at least the bottom surface part on the light source side of the wedge part and with the premise that the angle formed by the slant face portion of the wedge part and the normal of the light output plane is θ, θ is in a range of 3°≦θ≦15°.
According to the present invention, since the wedge part formed between the lens parts of the trapezoidal shape made of a light transmissible resin is filled with a light absorbing material, a view angle controlling sheet having the view angle controlling effect and a high light beam transmittance to the observer side can be obtained. According to the present invention, the wedge part has a cross sectional shape of a substantially isosceles triangle or a substantially isosceles trapezoid, or a trapezoid having a pair of opposite sides not parallel with each other with the angles formed with the upper bottom or the lower bottom different with each other (hereinafter, it is described as the “trapezoid unsymmetrical in the right and left direction”), or a triangle having angles formed with the right and left sides and the bottom side different with each other and the vertex and the bottom angle formed as an acute angle (hereinafter, it is described as the “acute triangle unsymmetrical in the right and left direction”). Since the wedge part has the cross sectional shape, a shaping die can be used in the production, a highly accurate sheet can be produced efficiently and continuously, and furthermore, the specification change can be dealt with immediately so that an inexpensive view angle controlling sheet can be obtained.
According to the present invention, since the wedge part formed between the trapezoids made of a light transmissible resin is filled with a material having the light absorbing property, a view angle controlling sheet having the effect of controlling the view angle and a high light beam transmittance to the observer side can be obtained. In the present invention, since the wedge part is substantially isosceles trapezoidal or trapezoidal unsymmetrical in the right and left direction, the vertex of the upper bottom surface of the wedge part can be an obtuse angle so that the die for producing the wedge part, or the like can be produced easily, and furthermore, the strength of the wedge part can be improved so as to produce a high quality view angle controlling sheet (including a film) can be produced stably. Furthermore, since a shaping mold can be used for the production, a highly accurate sheet can be produced efficiently and continuously and furthermore, the specification change can be dealt with immediately so that an inexpensive view angle controlling sheet can be obtained.
According to the present invention, in the case the angle θ formed by the slant face portion of the wedge part and the normal of the light output plane is less than 3°, the diffused light beam from the light source cannot reach sufficiently to the observer front side so that the luminance improving effect cannot be obtained. On the other hand, in the case θ is more than 15°, due to too small the area of the lens part for having the diffused light beam from the light source transmitted, the luminance is lowered. In order to maintain the front side luminance using the view angle controlling sheet of the present invention, the preferable range of θ is 3° or more and 15° or less.
A second aspect of the present invention is the view angle controlling sheet of the first aspect, wherein the cross sectional shape of the wedge part is substantially isosceles trapezoidal or substantially isosceles triangular with the wider lower bottom surface provided to the light source side.
According to the present invention, since the wedge part is substantially isosceles trapezoidal, the vertex of the upper bottom surface of the wedge part becomes an obtuse angle so that the die, or the like for producing the wedge part can be produced more easily compared with the case of the substantially isosceles triangular cross sectional shape, and furthermore, the strength of the wedge part is improved so that a high quality view angle controlling sheet (including a film) can be produced stably, and thus it is preferable.
A third aspect of the present invention is the view angle controlling sheet according to the first aspect, wherein the cross sectional shape of the wedge part is trapezoidal unsymmetrical in the right and left direction or an acute triangular unsymmetrical in the right and left direction with the wider lower bottom provided to the light source side.
According to the present invention, since the cross sectional shape of the wedge part is trapezoidal unsymmetrical in the right and left direction or an acute triangular unsymmetrical in the right and left direction, the light output angle with the peak light beam transmittance can be shifted so as to effectively realize the reflection preventing function, and thus it is preferable.
A fourth aspect of the present invention is the view angle controlling sheet according to any one of the first to third aspects, wherein with the premise that the refractive index of the main material comprising the wedge part is N2 and the refractive index of the material comprising the lens part is N1, the relationship of N2<N1 is satisfied.
According to the present invention, since the refractive index difference of the light transmissible resin as the material comprising the lens part and the main material comprising the wedge part is provided larger by N2<N1, the total reflection in the slant face portion of the wedge part can be carried out efficiently so that the luminance deterioration in the front side can be restrained.
A fifth aspect of the present invention is the view angle controlling sheet according to any one of the first to fourth aspects, wherein the slant face portion of the wedge part has a curved and/or bent cross sectional shape such that the angle formed with the observer side surface differs in the light source side and the observer side.
A sixth aspect of the present invention is the view angle controlling sheet according to any one of the first to fifth aspects, wherein the light absorbing material to fill the wedge part is black particles.
A seventh aspect of the present invention is the view angle controlling sheet according to the sixth aspect, wherein with the premise that the lower bottom surface width of the wedge part is L μm and the average particle size of the black particles is φ μm, the relationship of 1 μm≦φ≦(L/2) μm is satisfied.
An eighth aspect of the present invention is the view angle controlling sheet according to any one of the first to seventh aspects, wherein the light reflection layer provided to the bottom surface part on the light source side of the wedge part comprises a transparent resin layer including a light reflection material.
A ninth aspect of the present invention is the view angle controlling sheet according to the eighth aspect, wherein the light reflection material is a white pigment including one kind or two or more kinds selected from the group consisting of a silica, an alumina, a titanium oxide, a zinc oxide, a barium sulfate, and a magnesium oxide, or resin beads colored in white or glass beads.
A tenth aspect of the present invention is the view angle controlling sheet according to any one of the first to ninth aspects, wherein at least one additive function of AR, AS and AG is provided to at least on one surface side.
An eleventh aspect of the present invention is a liquid crystal display apparatus comprising the view angle controlling sheet according to any one of the first to tenth aspects, a light source to be disposed on one side of the view angle controlling sheet, and a liquid crystal panel to be disposed on the other side of the view angle controlling sheet so as to solve the problems.
A twelfth aspect of the present invention is the liquid crystal display apparatus according to the eleventh aspect, wherein the view angle controlling sheet is bonded to the liquid crystal panel side.
According to the view angle controlling sheet of the present invention, since the lens parts having a trapezoidal cross sectional shape made of a light transmissible resin are arranged by a predetermined interval, the cross sectional shape of the adjacent lens parts is wedge like with the lower bottom surface wider to the light source side as substantially isosceles trapezoidal, substantially isosceles triangular, trapezoidal unsymmetrical in the right and left direction or acute triangular unsymmetrical in the right and left direction, and the wedge part is filled with a material having the light absorbing property, a view angle controlling sheet having the view angle controlling effect can be obtained. Moreover, since the view angle controlling sheet of the present invention is provided between the light source and the liquid crystal panel of a liquid crystal display apparatus, the light incident angle to the liquid crystal panel can be controlled so that the unnecessary reflection of the screen of the vehicle mounting type liquid crystal display apparatus to the window glass, or the like can be prevented. Furthermore, since the refractive index difference of the light transmissible resin and the main material comprising the wedge part is large, the light beam diffused from the light source can be utilized effectively so as to improve the utilization efficiency of the light beam for improving the front side luminance.
Furthermore, according to the view angle controlling sheet of the present invention, since a shaping die can be used at the time of the production, a highly accurate sheet with the wedge part strength improved can be produced efficiently and continuously, and furthermore, an inexpensive view angle controlling sheet capable of immediately dealing with the specification change can be obtained.
Hereinafter, the embodiments of the present invention will be explained with reference to the drawings. In order to facilitate understanding of the present invention, the reference numerals of the accompanied drawings are applied, however, the present invention is not limited to the embodiments shown in the drawings.
In the present embodiment, the base sheets 11, 13 to be attached to the view angle controlling sheet S1 may be provided on either of the light source side and the observer side, or only the view angle controlling sheet S1 may be provided without using a base sheet. As to the method for forming the lens part, the conventionally known methods such as the thermal press method of pressing a heated die to a thermoplastic resin, the casting method of injecting a thermoplastic resin composition into a mold and solidifying the same, an injection molding method, and a UV method of injecting a ultraviolet ray hardening type resin composition into a shaping mold and hardening the same with a ultraviolet ray, can be used. Among these methods, the UV method with the excellent mass productivity is more preferable. According to the UV method, using a roll like mold, an arranged lens unit can be produced continuously.
The refractive index N1 of the lens part 12 and the refractive index N2 of the low refractive index substance for filling the wedge part 14 are set in a predetermined range N2<N1 for obtaining the optical characteristics of the view angle controlling sheet S1. Moreover, the angle formed by the slant face with the wedge part 14 and the lens part 12 contacted and the normal V of the light output plane (the line parallel to the perpendicular incident light beam to the view angle controlling sheet S1) is formed in a predetermined angle θ1.
The wedge part 14 is filled with a resin as the main material mixed with a pigment such as a carbon or a predetermined dye so as to be colored to a predetermined concentration. The resin colored to a predetermined concentration is filled into the wedge part by a method such as the wiping method so as to be hardened and fixed by heat, the ultraviolet ray, or the like. The view angle controlling sheet S1 shown in the figure has a light reflection layer 10 formed on the lower bottom surface 17 on the light source side. Moreover, the light source side base sheet 11 and the observer side base sheet 13 are made of a material having the substantially same refractive index as that of the lens part 12. At least one additive function of AR, AS and AG may be provided to at least on one surface side of the view angle controlling sheet S1. Here, “AR” is the abbreviation of the anti reflection, which denotes the function of restraining the reflectance of the light beam incident on the lens surface. Moreover, “AS” is the abbreviation of the anti static, which denotes the function of preventing charging that prevents charging in the production process. Moreover, “AG” is the abbreviation for the anti glare, which denotes the function of preventing glaring of the lens surface that prevents generation of the Newton ring.
In this embodiment, the light reflection layer 10 comprises a transparent resin layer including a light reflection material. The light reflection material is preferably a white pigment including one kind or two or more kinds selected from the group consisting of a silica, an alumina, a titanium oxide, a zinc oxide, a barium sulfate, and a magnesium oxide, or resin beads colored in white or glass beads. As the material for the resin beads, for example, an acrylic resin, a polyurethane, a polyvinyl chloride, a polystyrene, a polyacrylonitrile, a polyamide, or the like can be presented. As to the resin beads or the glass beads, those having the particle size specified are preferable in terms of the reflectance control. The average particle size thereof is preferably same as that of the black particle, that is, 1 μm or more and half of the width of the upper bottom surface or less, however, as long as it is in the particle size range, it needs not always same as the particle size of the black particle. In the case the particle size of the resin beads or the glass beads is less than 1 μm, the light reflection effect is insufficient. On the other hand, in the case the particle size is more than the range, the coating operation of the resin composition comprising the light reflection layer 10 is difficult.
As in the case of the low refractive index substance filled into the wedge part 14, the transparent resin layer including the light reflection material is filled and fixed on the low refractive index substance filled in the wedge part 14 so as to have a predetermined film thickness by a method such as the wiping method. As the transparent resin comprising the light reflection layer 10, the resin used as the binder for the light absorbing layer, or the like can be used. An ink prepared with the light reflection material, the binder and the photo initiator can be filled into the wedge part 14 so as to be hardened and fixed by the ultraviolet ray.
The material including the light reflection material comprising the light reflection layer in this embodiment can be prepared and used as an ink with the materials optionally selected from the materials. The composition ratio thereof can be determined optionally according to the evaluation of the hardening property by the ionizing radiation and the various physical properties after hardening. It is preferably 10 to 50 parts of the light reflection material, 50 to 90 parts of the binder and about 1 to 10 parts of the photo initiator. The ink may include a component to be included ordinarily, such as a plasticizing agent in addition to the components.
Next, the optical path of a light beam inputted into the lens part 12 of the view angle controlling sheet S1 will be explained briefly with reference to
The refractive index N1 of the lens part 22 and the refractive index N2 of the low refractive index substance 26 are set in a predetermined range N2<N1 for obtaining the optical characteristics of the view angle controlling sheet S2. Moreover, the angle formed by the slant face with the wedge part 24 and the lens part 22 contacted and the normal V of the light output plane (the line parallel to the perpendicular incident light beam to the view angle controlling sheet S2) is formed in a predetermined angle θ2.
As to the method for forming the lens part, the conventionally known methods such as the thermal press method of pressing a heated die to a thermoplastic resin, the casting method of injecting a thermoplastic resin composition into a mold and solidifying the same, an injection molding method, and a UV method of injecting a ultraviolet ray hardening type resin composition into a shaping mold and hardening the same with a ultraviolet ray, can be used. Among these methods, the UV method with the excellent mass productivity is more preferable. According to the UV method, using a roll like mold, an arranged lens unit can be produced continuously. For example, the lens part 22 in general is made of an ionizing radiation hardening material such as an epoxy acrylate. In the case of carrying out a method for producing a lens part using an ionizing radiation hardening material, a method of forming a lens part on a base sheet 23 is used.
At the time, as the transparent low refractive index substance 26 to be the main material comprising the wedge part 24, it is preferable to use an ionizing radiation hardening material such as a urethane acrylate. As the light absorbing particle 29 comprising the wedge part 24, a commercially available colored particle can be used. For example, it is used as an ink in a state dispersed in the transparent low refractive index substance 26 as the binder.
That is, the wedge part 24 is filled with an ink comprising a colored particle having a light absorbing function, an ionizing radiation hardening type resin to be the main material having the function of a transparent low refractive index substance and of a binder, and a photo initiator for smoothly carrying out the ionizing radiation hardening operation. In order to improve the production easiness, as needed, a small amount of an additive such as a defoaming agent and a leveling agent may optionally be added to the ink.
As the colored particle, a black pigment such as a carbon black, a resin particle such as a transparent particle of an acrylic, or the like dyed with the black pigment such as a carbon black, or the like can be used. Moreover, a mixture of various pigments of blue, purple, yellow and red other than the black pigment and/or a dye, or a substantially black material prepared by mixing and dispersing the black coloring material to a blue, purple, yellow and red coloring material can be used as well. As the blue pigment, a copper phthalocyanine, or the like, as the purple pigment, a dioxadine violet, or the like, as the yellow pigment, a disazo yellow, or the like, and as the red pigment, a chromo phthalic red typel, or the like can be used, but it is not limited thereto, and instead of a pigment, a dye can be used as well. Moreover, a colored particle prepared by coloring a resin particle of a transparent particle such as an acrylic with a coloring pigment or a dye with a blue, purple, yellow, red, black pigment or dye mixed and dispersed can be used as well. Among the colored particles, in the present invention, a black particle having the highest light absorbing property is the preferable material.
The light absorbing particle 29 in the view angle controlling sheet S2 in the second embodiment preferably has a 1 μm or more average particle size and half of the width of the upper bottom surface 28 of the wedge part 24 or less. In the case the size of the light absorbing particle 29 is less than 1 μm and too small, a sufficient light absorbing effect cannot be obtained. On the other hand, in the case the size of the light absorbing particle 29 is more than half or the width of the upper bottom surface 28 of the wedge part 24 and too large, the inside of the wedge part 24 can hardly be filled with the ink at the time of the production so as to deteriorate the filling ratio as well as irregularity is generated in the filling ratio depending on the unit wedge part so as to generate the optical irregularity, and thus it is not preferable.
Moreover, the light absorbing particle 29 in the view angle controlling sheet S2 in the second embodiment is provided preferably by 10 to 50% by volume with respect to the total volume of the wedge part 24. By maintaining the ratio, the easy production conditions can be provided while maintaining a sufficient light absorbing effect.
As transparent low refractive index substance 26 as the binder, for example, a transparent resin having a predetermined refractive index and the ionizing radiation hardening function, such as a ultraviolet ray hardening type resin, an electron beam hardening type resin, or the like can be used. Although some have the hardening reaction directly by the ionizing radiation, it is general to generate the hardening reaction via a catalyst or a substance for exciting the reaction called an initiating agent. In order to generate the hardening function with an ultraviolet ray having a 300 to 400 nm wavelength, it is general to mix a substance for exciting the reaction in an ultraviolet ray range called a photo initiator by several %. As the photo initiator, there are a ketone based one and an acetophenone based one, and Sandley 1000, Darocure 1163, Darocure 1173, Irgacure 183, Irgacure 651, or the like are known. According to the kind (wavelength characteristics) of the ionizing radiation for hardening, it can be selected optionally. As the ionizing radiation hardening type resin, a reactive oligomer (an epoxy acrylate based one, a urethane acrylate based one, a polyether acrylate based one, a polyester acrylate based one, a polythiol based one, or the like), a reactive monomer (a vinyl pyrrolidone, a 2-ethyl hexyl acrylate, a β-hydroxy acrylate, a tetrahydro fulfuryl acrylate, or the like) can be selected optionally. For the flowability adjustment for the ionizing radiation hardening type light absorbing material before hardening, the kind of the reactive oligomer and the composition ratio of a low molecular weight reactive monomer having a low viscosity can be changed optionally.
The material having the light absorbing property in this embodiment can be used as an ink by homogeneously dispersing (mixing) one optionally selected from the materials by a three roll dispersing method, or the like. The composition ratio can be determined optionally according to the evaluation of the hardening property by the ionizing radiation, and the various physical properties after hardening, and the coloring agent is 10 to 50 parts, the binder is 50 to 90 parts and the photo initiator is preferably about 1 to 10 parts.
After filling the wedge part 24 by a wiping method, or the like, the ink including at least the transparent low refractive index substance 26 and the light absorbing particle 29 is hardened by the ionizing radiation such as the ultraviolet ray so as to be fixed to the wedge part. Moreover, the light source side base sheet 21 and the observer side base sheet 23 are made of a material having the substantially same refractive index as that of the lens part 22.
In this embodiment, the light reflection layer 20 comprises a transparent resin layer including a light reflection material. The light reflection material is preferably a white pigment including one kind or two or more kinds selected from the group consisting of a silica, an alumina, a titanium oxide, a zinc oxide, a barium sulfate, and a magnesium oxide, or resin beads colored in white or glass beads. As the material for the resin beads, for example, an acrylic resin, a polyurethane, a polyvinyl chloride, a polystyrene, a polyacrylonitrile, a polyamide, or the like can be presented. As to the resin beads or the glass beads, those having the particle size specified are preferable in terms of the reflectance control. The average particle size thereof is preferably same as that of the black particle, that is, 1 μm or more and half of the width of the upper bottom surface or less, however, as long as it is in the particle size range, it needs not always same as the particle size of the black particle. In the case the particle size of the resin beads or the glass beads is less than 1 μm, the light reflection effect is insufficient. On the other hand, in the case the particle size is more than the range, the coating operation of the resin composition comprising the light reflection layer 20 is difficult.
As in the case of the low refractive index substance filled into the wedge part 24, the transparent resin layer including the light reflection material is filled and fixed on the low refractive index substance filled in the wedge part 24 so as to have a predetermined film thickness by a method such as the wiping method. As the transparent resin comprising the light reflection layer 20, the resin used as the binder for the light absorbing layer, or the like can be used. An ink prepared with the light diffusing material, the binder and the photo initiator can be filled into the wedge part 24 so as to be hardened and fixed by the ultraviolet ray.
The material including the light reflection material comprising the light reflection layer in this embodiment can be prepared and used as an ink with the materials optionally selected from the materials. The composition ratio thereof can be determined optionally according to the evaluation of the hardening property by the ionizing radiation and the various physical properties after hardening. It is preferably 10 to 50 parts of the light reflection material, 50 to 90 parts of the binder and about 1 to 10 parts of the photo initiator. The ink may include a component to be included ordinarily, such as a plasticizing agent in addition to the components.
In this embodiment, as in the case of the view angle controlling sheet S1 in the first embodiment, at least one additive function of AR, AS and AG may be provided to at least on one surface side of the view angle controlling sheet S2 so as to provide the function property to the view angle controlling sheet s2.
Next, the optical path of a light beam inputted into the lens part 22 of the view angle controlling sheet S2 will be explained briefly with reference to
In the present invention, the base sheets 31, 33 to be attached to the view angle controlling sheet S3 may be provided on either of the light source side and the observer side, or only the view angle controlling sheet S3 may be provided without using a base sheet. As to the method for forming the lens part, the conventionally known methods such as the thermal press method of pressing a heated die to a thermoplastic resin, the casting method of injecting a thermoplastic resin composition into a mold and solidifying the same, an injection molding method, and a UV method of injecting a ultraviolet ray hardening type resin composition into a shaping mold and hardening the same with a ultraviolet ray, can be used. Among these methods, the UV method with the excellent mass productivity is more preferable. According to the UV method, using a roll like mold, an arranged lens unit can be produced continuously. For example, the lens part 32 in general is made of an ionizing radiation hardening material such as an epoxy acrylate. In the case of carrying out a method for producing a lens part using an ionizing radiation hardening material, a method of forming a lens part on a base sheet 33 is used.
The refractive index N1 of the lens part 32 and the refractive index N2 of the low refractive index substance 26 for filling the wedge part 34 are set in a predetermined range N2<N1 for obtaining the optical characteristics of the view angle controlling sheet S3. Moreover, the angles formed by the slant face with the wedge part 34 and the lens part 32 contacted and the normal V of the light output plane (the line parallel to the perpendicular incident light beam to the view angle controlling sheet S3) 041, θ42 are formed unsymmetrical in the right and left direction such that θ41<θ42, 3°≦θ41≦15°, 3°≦θ42≦15°.
After filling the wedge part 34 by a wiping method, or the like, the ink including at least the transparent low refractive index substance 26 and the light absorbing particle 29 is hardened by the ionizing radiation such as the ultraviolet ray so as to be fixed to the wedge part. Moreover, the light source side base sheet 31 and the observer side base sheet 33 are made of a material having the substantially same refractive index as that of the lens part 32.
In this embodiment, as in the case of the view angle controlling sheets S1, S2 in the first or second embodiment, at least one additive function of AR, AS and AG may be provided to at least on one surface side of the view angle controlling sheet S3 so as to provide the function property to the view angle controlling sheet S3.
Next, the optical path of a light beam inputted into the lens part 32 of the view angle controlling sheet S3 will be explained briefly optionally with reference to
The embodiments with the wedge part cross sectional shape of a substantial isosceles trapezoid or a trapezoid unsymmetrical in the right and left direction have been described so far, however, the cross sectional shape of the wedge part according to the present invention is not limited to these shapes. Even in the case the cross sectional shape is substantially isosceles triangular (see
The surface protection plate 53 faces to the display area 52b of the surface 52a of the liquid crystal panel 52. The surface protection plate 53 may be provided with a function by applying a surface treatment of hard coating, non glare, non reflection coating, or the like to the surface of a transparent film of an acrylic resin, a polycarbonate, or the like.
The view angle controlling sheet 51 of the present invention can also be used for a semi transmission type/semi reflection type liquid crystal display apparatus.
The surface light source 54 disposed on the rear surface side of the liquid crystal panel 52 plays the role of a back light for the liquid crystal panel 52. The light source 54 outputs a surface like light beam from the light emitting surface 54a toward the rear surface of the liquid crystal panel 52 via the view angle controlling sheet 51. As to the light source 54, either of the immediately below type system or the edge light type system can be used. Those of any system such as those having a surface like light beam from a cold cathode fluorescent pipe or a light emitting diode with a light diffusion plate, or the like, or an electroluminescence, or the like can be used as long as it is a surface light source for directing a light beam to the entire surface of the liquid crystal panel. The view angle controlling sheet 51 is superimposed thereon between the light source 54 and the liquid crystal panel 52 such that the view angle controlling sheet 51 receives a light beam from the light source 54 so as to input the same to the rear surface of the liquid crystal panel 52 while controlling the transmission angle of the light beam. Thereby, an image can be displayed on the liquid crystal panel 52.
A display apparatus of such a configuration is used mainly for the application of preventing the reflection of the display image to a front glass as in the case of a display apparatus for a vehicle. As the display apparatus in the embodiment, various kinds such as a liquid crystal television, a liquid crystal monitor for a navigator, a display apparatus for an air conditioner, and a meter can be presented.
Moreover, it can be used also for the application of preventing peeping for the display apparatus such as a portable telephone and an ATM. At the time, in order to thoroughly preventing peeping, it is also possible that only the observer in the front can view by using a view angle controlling sheet with the lens parts arranged in the perpendicular direction and a view angle controlling sheet with the lens parts arranged in the horizontal direction in a state with the two sheets laminated.
A view angle controlling sheet provided with a wedge part having an isosceles trapezoidal cross section as shown in
As to the luminance measurement, using a 5,000 cd/m2 back light having an even diffusion characteristic as the light source, it was measured from the back light front side with the view angle controlling sheet placed on the back light by a luminance meter LS-110 produced by KONICA MINOLTA HOLDINGS, INC. As to the view angle, using a minute deviation angle luminance meter GP-500 produced by Nakamura Color Technology Research Institute, the angle dependency of the transmittance was measured in a state with the view angle controlling sheet superimposed on the back light. The angle range to have the transmittance of 10% or more with the reference piece provided as 100% was defined to be the view angle.
Aperture ratio: 40%
Pitch between the lenses: 0.065 mm
Lens part material (resin) refractive index: 1.56
Wedge part main material refractive index: 1.48
Wedge part upper bottom surface width: 8 μm
Trapezoid taper angle: 6°
Black light absorbing particle size: 6 μm
Black light absorbing particle concentration (with respect to the wedge part total volume): 20% by volume
Light reflection layer material: barium sulfate
A view angle controlling sheet was produced in the same conditions as in the example 1 except that the light reflection layer was not provided.
The view angle controlling sheets produced by the example 1 and the comparative example 1 were compared in terms of the view angle and the luminance. The results are shown in the table 1.
As it is shown in the table 1, the view angle controlling sheet of the example 1 shows the effect of improving the luminance by 10% compared to the comparative example 1 without the light reflection layer. The view angle characteristics are not changed.
A view angle controlling sheet provided with a wedge part having an isosceles trapezoidal cross section as shown in
The front side transmittance of the view angle controlling sheet was measured using a minute deviation angle luminance meter GP-500 produced by Nakamura Color Technology Research Institute, with a reference piece capable of obtaining a substantially even diffused light beam at the angle −80° to +80° for reference with the transmittance of only the reference piece provided as 100%. Next, with the view angle controlling sheet to be measured superimposed on the reference peace, the transmittance in the front direction was measured so as to find out the relative value with respect to the reference piece.
As to the luminance measurement, using a 5,000 cd/m2 back light having an even diffusion characteristic as the light source, it was measured from the back light front side with the view angle controlling sheet placed on the back light by a luminance meter LS-110 produced by KONICA MINOLTA HOLDINGS, INC.
Aperture ratio: 50%
Pitch between the lenses: 0.060 mm
Lens part material (resin) refractive index: 1.56
Wedge part main material refractive index: 1.48
Wedge part upper bottom surface width: 6.4 μm
Wedge part lower bottom surface width: 30 μm
Trapezoid taper angle: 4.5°
Black light absorbing particle size: 6 μm
Black light absorbing particle concentration (with respect to the wedge part total volume): 20% by volume
Light reflection layer material: barium sulfate
A view angle controlling sheet provided with a wedge part having a trapezoidal cross section unsymmetrical in the right and left direction as shown in
Aperture ratio: 55%
Pitch between the lenses: 0.074 mm
Lens part material (resin) refractive index: 1.56
Wedge part main material refractive index: 1.48
Wedge part upper bottom surface width: 6.4 μm
Wedge part lower bottom surface width: 33 μm
Trapezoid taper angle: θ41=3.5°, θ42=6.5°
Black light absorbing particle size: 6 μm
Black light absorbing particle concentration (with respect to the wedge part total volume): 20% by volume
Light reflection layer material: barium sulfate
A view angle controlling sheet provided with a wedge part having a trapezoidal cross section unsymmetrical in the right and left direction as shown in
Aperture ratio: 54%
Pitch between the lenses: 0.060 mm
Lens part material (resin) refractive index: 1.56
Wedge part main material refractive index: 1.48
Wedge part upper bottom surface width: 6.4 μm
Wedge part lower bottom surface width: 28 μm
Trapezoid taper angle: θ41=3.5°, θ42=4.5°
Black light absorbing particle size: 6 μm
Black light absorbing particle concentration (with respect to the wedge part total volume): 20% by volume
Light reflection layer material: barium sulfate
Using the view angle controlling sheets produced by the specifications of the examples 2, 3, the relationship between the transmittance and the light output angle of the view angle controlling sheet was examined. The results are shown in
As shown in
The luminance of the view angle controlling sheets of the examples 2, 3, 4 was compared in the case of the light output angle of 0°, −5°, 30°. The results are shown in the table 2.
As shown in the table 2, the view angle controlling sheet according to the example 2 comprising the wedge part having an isosceles trapezoidal cross sectional shape has a luminance at the light output angle 0° larger than the luminance at the light output angles −5°, 30°. On the other hand, the view angle controlling sheets according to the examples 3, 4 comprising the wedge part having a trapezoidal cross section unsymmetrical in the right and left direction have a luminance at the light output angle −5° larger than the luminance at the light output angles 0°, 30°. That is, from the results of the table 2, it was confirmed that the peak position can be shifted by providing the cross sectional shape of the wedge part unsymmetrical in the right and left direction. As in the case of the view angle controlling sheet according to the example 2, the luminance at the light output angle 30° was extremely small also in the view angle controlling sheets according to the examples 3, 4. That is, from the results, it was confirmed that a view angle controlling sheet with the excellent view angle control can be produced with a wedge part cross sectional shape provided as a trapezoid unsymmetrical in the right and left direction.
Although the present invention has been explained relating to the embodiments which seemed to be most practical and preferable at this point, the present invention is not limited to the embodiments disclosed in this specification, and it can be modified optionally within a scope not parting from the gist and the idea of the invention to be read out from the claims and the entire specification so that a view angle controlling sheet accompanied with such a modification and a liquid crystal display apparatus using the same should be understood as those included in the technological range of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-333953 | Nov 2004 | JP | national |
| 2005-270968 | Sep 2005 | JP | national |
