JP2011252939A - Manufacturing method of visibility improvement sheet, and visibility improvement sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a visibility improvement sheet that is capable of efficiently being filled with ink by only one time ink filling and that has superior contrast even when a narrow line width light absorption part is formed.SOLUTION: Grooves, each of which has a roughly rectangular cross section, provided in parallel between light transmission parts are formed by forming the light transmission parts with predetermined intervals in parallel. Then ink compositions including transparent ionized radiation curable resin compositions and colored fine particles are filled into the grooves while being pressurized.

Description

  The present invention relates to a method for manufacturing a visibility improving sheet, and more particularly, installed on the front surface of a display device, and the performance of the display device, in particular, a decrease in contrast or glare when the display device is exposed to external light, The present invention relates to a method for manufacturing a visibility-enhancing sheet having a function of preventing a decrease in performance due to image reflection, a function of controlling a viewing angle by suitably diffusing or condensing effective light of a display device, and the like.

  In a liquid crystal display device, it is usually preferred that the viewing angle is wide so that a good image can be obtained from any position of the observer. On the other hand, for example, when working on a commuter train or in a liquid crystal display device installed in a public place such as an ATM, it may be difficult to see the screen from people around you. There is a demand for a peeping prevention function for protecting privacy so that it can be seen only by an observer of the display device and cannot be seen by others. In car-mounted liquid crystal display devices such as car navigation systems, the screen of the liquid crystal display device is reflected on the window glass at night and the like, and the phenomenon of blocking the field of view occurs. Control of the light emission angle is desired.

  In response to such a demand, for example, JP 2006-119365 A (Patent Document 1) proposes a louver-type visibility improving sheet having a structure in which light transmission layers and light shielding layers are alternately arranged. As a light shielding layer, it is disclosed to use a material comprising a light transmission layer mixed with a filler such as carbon black or carbon fiber.

On the other hand, the louver-type visibility improving sheet as described above simply cuts the image light in the oblique direction, so that depending on the type of display device, the diffusion light source of the image light that should reach the observer is reduced. As a result, the brightness of the display screen may be lowered.

  In order to solve the above problems, a visibility improving sheet capable of improving the contrast by shielding outside light and reducing the occurrence of double images should be installed between the light source of the liquid crystal display device and the liquid crystal panel. Has been proposed. As such a visibility improving sheet, sheets having various structures have been proposed. For example, a lens portion having a trapezoidal cross-sectional shape is arranged at a predetermined interval, and a wedge portion between adjacent lens portions is provided with a lens portion. A material having a structure filled with a material having a lower refractive index and a carbon pigment or the like has been proposed (for example, JP-A-2006-85050, etc .: Patent Document 2).

  Then, as a material constituting the wedge-shaped part, an ink composition in which a colored resin bead is mixed with a lens material such as an ionizing radiation curable resin is used, and this composition is filled in the wedge-shaped part and irradiated with ionizing radiation to be cured. Forming a wedge-shaped portion. The filling of the ink composition into the wedge-shaped part is such that after filling the ink composition into the recesses between the plurality of prism parts, the excess ink composition is scraped off and the wedge-shaped groove is filled with the ink composition. It is common to do this. (For example, Unexamined-Japanese-Patent No. 2008-146074: Patent document 3).

  Filling the wedge-shaped portion with the ink composition is performed by pouring the ink composition into the wedge-shaped portion and then scraping off excess ink with a doctor or the like. However, depending on the shape of the wedge-shaped portion, that is, the opening width and depth, ink may not be sufficiently filled into the wedge-shaped portion. In order to solve such a problem, Japanese Patent Application Laid-Open No. 2008-146074 proposes that ink is filled into the wedge-shaped portion two or more times and ink is filled more completely.

JP 2006-119365 A JP 2006-85050 A JP 2008-146074 A

  As described above, when the ink is filled into the wedge-shaped portion, the ink may not be completely filled up to the bottom of the wedge-shaped portion if the filling is performed only once as in the prior art. In particular, in recent years, a display device having a narrower line width, that is, a visibility improving sheet having a substantially rectangular cross section and a narrow opening width has been sought due to higher definition of display devices, and a light absorbing portion having a narrow line width is formed. On the other hand, it is difficult to completely fill the ink to the bottom of the wedge-shaped portion by filling the ink only once. Further, although the ink filling rate to the wedge-shaped portion is improved by performing the ink filling a plurality of times, the number of manufacturing steps increases, so there is a concern that the manufacturing cost increases.

  In order to form the light absorbing portion constituting the visibility improving sheet, the present inventors recently filled the grooves provided in parallel between the light absorbing portions while pressurizing the ink, and scraped off the excess ink. As a result, even when the ink was filled only once, it was possible to efficiently fill the light absorbing portion with a narrow line width, and as a result, it was possible to realize a visibility improving sheet excellent in contrast. The present invention is based on this finding.

  Therefore, even if the object of the present invention is to form a light absorbing portion with a narrow line width, the ink can be efficiently filled into the groove by filling the ink only once, and the ink filling rate of the light absorbing portion is high, It is providing the method which can manufacture the visibility improvement sheet | seat which is excellent in contrast.

  Another object of the present invention is to provide a visibility improving sheet obtained by the above production method.

  Another object of the present invention is to provide a display device including the visibility improving sheet.

The method for manufacturing a visibility improving sheet according to the present invention includes a light transmission part arranged in parallel at a predetermined interval and a light absorption part provided in parallel between the light transmission parts and having a substantially rectangular cross section. A method for producing a property improving sheet,
By forming the light transmission part so as to be arranged in parallel at a predetermined interval, a groove having a substantially rectangular cross section provided in parallel between the light transmission parts is formed,
Filling the groove with an ink composition comprising a transparent ionizing radiation curable resin composition and colored fine particles while applying pressure;
It is characterized by comprising.

Moreover, as an aspect of the present invention, it is preferable that the pressurization at the time of filling is performed in a range of ^{2 to} 15.0 kgf / cm ² .

  Moreover, as an aspect of the present invention, the ink filling is preferably performed using a coating apparatus selected from a die coater, a bar coater, a roll coater, or a knife coater.

  Moreover, as an aspect of the present invention, it is preferable that the ink ejection speed from the coating apparatus is 1 to 1.5 times the coating speed.

  Moreover, as an aspect of the present invention, it is preferable to perform a hydrophilization treatment on the groove surface before filling the groove with ink.

  As an aspect of the present invention, it is preferable that the hydrophilic treatment is performed by an atmospheric pressure plasma treatment.

  As an aspect of the present invention, it is preferable that an opening width of the groove is 8 to 12 μm.

  Moreover, as an aspect of the present invention, it is preferable that the hypotenuse of the light absorbing portion having the substantially triangular cross section or the substantially rectangular cross section has an angle of 0 to 3 ° with respect to the normal direction of the visibility improving sheet surface.

  As an aspect of the present invention, it is preferable that the colored fine particles are made of resin beads in which carbon black is kneaded in a resin.

  Moreover, as an aspect of the present invention, the carbon black preferably has an average particle size of 10 to 500 nm.

  Further, as an aspect of the present invention, the ionizing radiation curable resin composition comprises a polyester resin, a polyether resin, an acrylic resin, an epoxy resin, a urethane resin, an alkyd resin, a spiroacetal resin, a polybutadiene resin, a polythiol polyene resin, and many It is preferably composed of an oligomer or prepolymer such as (meth) arylate of a polyfunctional compound selected from polyhydric alcohols.

  Furthermore, as an aspect of the present invention, the ink composition preferably has a viscosity of 500 to 5,000 mPa · s.

  Further, as another aspect of the present invention, a visibility improving sheet obtained by the above method and a display device including the visibility improving sheet are also provided.

  In addition, as an aspect of the present invention, it is preferable that 1 to 30% by volume of the voids are included with respect to the total volume of the light absorbing portion.

  Furthermore, the display apparatus provided with the said visibility improvement sheet | seat as another aspect of this invention is also provided.

  In the present invention, when forming the light absorbing portion provided in parallel between the light transmitting portions, the ink composition is filled into the groove having a wedge-shaped cross section or a substantially rectangular cross section while being pressurized. As a result, even if the ink is filled only once, the light absorbing portion having a narrow line width can be efficiently filled with the ink, so that a visibility improving sheet excellent in contrast can be manufactured.

The schematic process drawing explaining the manufacturing method of the visibility improvement sheet | seat in one Embodiment of this invention. FIG. 2A is a schematic cross-sectional view when the ink composition is filled in a groove having a substantially rectangular cross section, and FIG. 2B is a diagram in which the ink composition is filled in a groove having a substantially triangular or wedge-shaped cross section. It is a cross-sectional schematic diagram at the time. The schematic process drawing explaining the manufacturing method of the visibility improvement sheet | seat in one Embodiment of this invention.

<Manufacturing method of visibility improving sheet>
First, the manufacturing method of the visibility improvement sheet | seat by this invention is demonstrated, referring drawings. The method for producing a visibility improving sheet according to the present invention includes a light transmitting portion arranged in parallel at a predetermined interval, a light absorbing portion having a substantially triangular cross section or a substantially rectangular cross section provided in parallel between the light transmitting portions, A wedge-shaped cross section or a substantially rectangular cross section provided in parallel between the light transmission portions by forming the light transmission portions so as to be parallel to each other at a predetermined interval. And a groove is filled with an ink composition containing a transparent ionizing radiation curable resin composition and colored fine particles while applying pressure. Hereinafter, each process is demonstrated in order.

  FIG. 1 shows a schematic process of a method for producing a visibility improving sheet according to the present invention. First, a plurality of light-transmitting portions 2 having a substantially trapezoidal shape or a substantially rectangular shape in a cross section in the layer thickness direction are formed on the base material 1 (FIG. 1A). The light transmitting portion 2 is an element having a substantially trapezoidal or substantially rectangular cross section arranged so that one sheet surface side is an upper side and the other sheet surface side is a lower side.

  The base material used in the above process is a layer that is disposed on the incident side of the image light and serves as a base for forming the light transmission part 2 and the light absorption part 5 described above. As the substrate, a transparent resin film, a transparent resin plate, a transparent resin sheet, or transparent glass can be used. Transparent resin films include triacetate cellulose (TAC) film, polyester film such as polyethylene terephthalate (PET), diacetyl cellulose film, acetate butyrate cellulose film, polyethersulfone film, polyacrylic resin film, polyurethane resin film Polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, polyether ketone film, (meth) acrylonitrile film, etc. can be suitably used. Among these, polyester films are preferably used. . Examples of the polyester film include polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, and polytrimethylene terephthalate.

  The formation of the light transmitting portion 2 varies depending on the type of resin used. For example, when the light transmission part is formed using a transparent thermoplastic resin, a hot press method or an injection molding method in which a heated mold is pressed against the thermoplastic resin, or a thermoplastic resin monomer is injected into the mold. A light transmitting portion having a desired shape can be formed by a casting method for polymerization and solidification. Further, when using an ionizing radiation curable resin, particularly an ultraviolet curable resin, a light transmitting portion having a desired shape is formed by a so-called UV method in which the resin is injected into a mold and irradiated with ultraviolet rays to be cured. Can be formed. Among these methods, in the present invention, the UV method excellent in mass productivity can be suitably used. According to the UV method, the arranged light transmission unit 2 can be continuously manufactured using a roll-shaped mold.

  By forming the plurality of light transmitting portions 2 on the base as described above, wedge-shaped or substantially rectangular grooves 3 provided in parallel are formed between the light transmitting portions. In the present invention, it is preferable to perform a hydrophilic treatment on the surface of the groove before filling the groove with the ink composition. By performing the hydrophilic treatment on the groove surface, it becomes easier to fill the groove with the ink composition, and the ink filling rate is improved. The hydrophilization treatment can be performed using a conventionally known method. Examples thereof include dry processes such as low-pressure plasma treatment, atmospheric pressure plasma treatment, corona treatment, ultraviolet irradiation treatment, and excimer lamp treatment, and wet processes such as alkali treatment with sodium hydroxide, potassium hydroxide, ethanolamine, and the like. Among these, atmospheric pressure plasma treatment is preferable from the viewpoint of production efficiency.

Next, an ink composition 4 containing a transparent ionizing radiation resin composition and colored fine particles is filled into the groove 3 having a wedge-shaped or substantially rectangular cross-section provided in parallel (FIG. 1B). Conventionally, an ink composition is poured into a groove using a dispenser or the like, and an excess ink composition overflowing from the groove is scraped off with a doctor blade or the like to fill the groove with the ink composition. In the present invention, the filling of the ink composition into the groove is performed while applying pressure. The pressurization during filling is preferably in the range of 1.5 to 15.0 kgf / cm ² , preferably in the range of ^{2 to} 12 kgf / cm ² , more preferably in the range of ^{2 to} 10 kgf / cm ² . When pressurizing less than 1.5 kgf / cm ^2, when forming a light-absorbing portion with a narrow line width, that is, when filling an ink composition into a groove with a narrow width of the opening, the ink reaches the bottom of the groove. The composition may not be fully filled. On the other hand, when the ink composition is filled at a pressure exceeding 15.0 kgf / cm ² , the filling pressure is too high and the load on the apparatus becomes large. Therefore, it is necessary to use a special apparatus.

  In order to fill the groove with the ink composition while applying pressure, it is preferably performed using a coating device selected from a die coater, a bar coater, a roll coater, or a knife coater. When ink marks are conspicuous, filling with a die coater is preferable. As a method of filling the groove while pressurizing the ink composition, a pressure pump can be used. For example, by adjusting the shim thickness and slit gap width of the die head portion of the die coater and supplying the ink composition into the die head with a pressure pump, the ink composition can be efficiently filled into the groove while being pressurized. .

  In particular, as shown in FIG. 2A, a visibility improving sheet incorporated in a high-definition display device has, for example, a substantially rectangular cross section having a height of 105 μm, an upper side width of 46 μm, and a lower side width of 48 μm. A line having a cross-sectional structure in which a light transmitting portion and a light absorbing portion having a substantially rectangular cross section in which the width of the upper side (that is, the width of the opening of the groove) is 12 μm and the width of the lower side is 10 μm are 1 pitch. A thing provided with a narrow light absorption part has come to be used. Further, the visibility improving sheet having such a thin line width light absorbing portion has a rectangular cross section of the light absorbing portion having an angle of 0 to 3 ° with respect to the normal direction of the visibility improving sheet surface, and is rectangular. It has a cross-sectional shape close to. When filling a groove with such a narrow opening width and a slanted side substantially vertically with ink using a conventional dispenser or the like, the cross section of the light absorbing portion as shown in FIG. 2B has a wedge shape. In comparison, the ink composition cannot be filled to the bottom of the groove in one filling, and in order to increase the ink filling rate, the ink filling with a dispenser and the excess ink scraping with a doctor blade, etc. Had to be repeated several times. In the present invention, since the ink composition is filled into the groove while applying pressure, it is considered that the ink composition is filled to the bottom of the groove even if it is filled once.

  After the ink composition 4 is filled into the grooves 3, that is, the recesses 3 between the plurality of light transmitting portions 2, the excess ink composition 4 is scraped off, and the ink composition 4 is formed in the wedge-shaped or substantially rectangular grooves 3. It is made to fill (FIG. 3 (a)). In order to improve the ink scraping property, as shown in FIG. 3A, a continuous scraping device such as a doctor blade 8 or a wiping roll is used.

  In the present invention, the above-described hydrophilization treatment of the groove surface, ink filling, and excess ink scraping can be performed continuously. For example, as shown in FIG. 1 (a), using a roll-shaped mold 6, the arranged light transmission unit 2 is continuously formed, and then the sheet is continuously fed in one direction (in the drawing, ), Atmospheric pressure plasma treatment device (not shown), die coater head (reference numeral 7 in FIG. 1B), and excess ink scraping device (reference numeral 8 in FIG. 3A) Can be installed in front of the sheet-shaped mold 6 in the sheet feeding direction. In this case, the ink discharge speed from the die coater is preferably 1 to 1.5 times the line speed. The discharge speed means the amount of ink discharged per unit area (m / min) per minute, and the line speed means a sheet in which a plurality of light transmission unit units are formed on a substrate. Means the sheet conveyance speed (m / min) when ink is filled while continuously feeding in one direction. When the line speed is faster than the ink discharge speed (that is, less than 1), the amount of ink filled in the groove becomes insufficient. On the other hand, if the discharge speed exceeds 1.5 times the line speed, the excess ink increases, and the excess ink that is scraped off increases, which is uneconomical.

  The filling ratio of the ink into the groove is influenced by the viscosity of the ink composition in addition to the degree of pressurization at the time of filling. In the present invention, the viscosity of the ink composition is preferably in the range of 500 to 5,000 mPa · s. If the ink viscosity is 5,000 mPa · s or more, even if it is pressurized, the viscosity of the ink is too high and the ink may not be filled to the bottom of the groove. Further, as will be described later, the ink scraping property deteriorates. On the other hand, when the ink viscosity is less than 500 mPa · s, the ink scraping property is good, but it becomes difficult to fill the wedge-shaped groove with the ink composition. In addition, the viscosity of an ink composition shall mean the value measured in 25 degreeC environment using the B-type viscosity meter.

  In order to improve the ink scraping property, a continuous wiping device using a doctor blade or a wiping roll is used. When the ink viscosity exceeds 5,000 mPa · s, the fluidity of the ink is poor and ink marks are conspicuous, and it may be difficult to form a desired light absorbing portion.

  Here, the ink composition used in this step will be described. The ink composition contains a transparent ionizing radiation resin composition and colored fine particles as essential components. As the ionizing radiation curable resin composition, an ionizing radiation curable resin composition used for a conventionally known visibility improving sheet or viewing angle improving sheet can be used. For example, those having an acrylate functional group can be suitably used. Specifically, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetals having a relatively low molecular weight can be used. Examples thereof include oligomers or prepolymers such as (meth) allylates of polyfunctional compounds such as resins, polybutadiene resins, polythiol polyene resins, and polyhydric alcohols. Although depending on the material constituting the light transmitting portion of the visibility improving sheet, a resin having a refractive index smaller than that of the material constituting the light transmitting portion may be selected from these resins.

  In addition, a reactive diluent may be added to the resin composition. Examples of such a reactive diluent include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N- Monofunctional monomers such as vinyl pyrrolidone and polyfunctional monomers may be used. Specifically, dimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di ( Examples include meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like.

  In order to convert the ionizing radiation curable resin composition into an ultraviolet curable resin composition, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylchuram mono as a photopolymerization initiator in the composition. A mixture of sulfides, thioxanthones, n-butylamine, triethylamine, poly-n-butylphosphine, or the like as a photosensitizer can be used. In particular, in the present invention, it is preferable to mix urethane acrylate as an oligomer and dipentaerythritol hexa (meth) acrylate as a monomer.

  As the colored fine particles used in the present invention, colored fine particles capable of selectively absorbing a specific wavelength in accordance with the characteristics of image light may be used for resin beads or glass beads, and carbon black, graphite, fibrous carbon may be used. Further, a material in which a metal salt such as black iron oxide, a colorant such as a dye or a pigment is kneaded can be used. From the viewpoint of easy kneading of the colorant, it is preferable to use resin beads. As the resin beads, melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, polystyrene beads, polyvinyl chloride beads and the like can be suitably used. Further, urethane cross-linked fine particles and silicon-based beads can also be suitably used. These resin beads are preferably those having a refractive index difference of about 0.1 of the ionizing radiation curable resin composition described above. Also, as the resin before kneading the colorant, a transparent resin can be used, but it is preferable to use a resin colored with a pigment or a dye, and a specific wavelength is selectively selected according to the characteristics of the image light. However, resin beads colored in black are preferably used.

  Among the above-mentioned materials, carbon black can be preferably used as the colorant. The amount of carbon black kneaded into the resin beads is about 0.1 to 0.7 parts by mass, preferably 0.15 to 0.5 parts by mass, more preferably 1 part by mass of the resin beads. Is 0.2 to 0.35 parts by mass. When the amount of kneading of carbon black is more than 0.7 parts by mass, the resin beads may be easily broken. On the other hand, when the amount is less than 0.1 parts by mass, colored fine particles having desired blackness cannot be obtained. There is a case. Carbon black having an average particle diameter of 10 to 500 nm can be suitably used. For example, furnace black, acetylene black, channel black, thermal black, carbon nanotube, carbon fiber and the like can be used. Commercially available products can also be used. For example, HCF series, MCF series, RCF series, LFF series (all manufactured by Mitsubishi Chemical Corporation), Vulcan series (made by Cabot Corporation), Ketjen series (Lion Corporation) Can be suitably used. Here, the average particle diameter means an arithmetic average diameter obtained by observing carbon black particles with an electron microscope.

  In order to improve the dispersibility of the colored fine particles in the ionizing radiation curable resin composition, the colored fine particles may be surface-treated. Examples of the surface treatment include hydrophilic treatment with a conventionally known silica coating and surface modification with plasma or the like.

  The ink composition containing each component described above is prepared by mixing a predetermined amount of colored fine particles into an ionizing radiation curable resin composition and adding a polymerization initiator or the like as desired. The addition amount of the colored fine particles is preferably in the range of 15 to 35% with respect to the total mass of the ink composition, and by setting this range, it is possible to realize a visibility improving sheet with more excellent contrast. If the content of the colored fine particles is too small, the light blocking property of the wedge-shaped groove (light absorbing portion) may be insufficient. If the content of the colored fine particles is too large, the resin beads may come into contact with each other and cracks or chipping may occur. Problems are likely to occur.

  In the preparation of the ink composition, as described above, the blending amount of each component and the type of each component can be appropriately selected so that the ink viscosity is 500 to 5,000 mPa · s.

  As described above, the light absorbing portion 5 having a substantially triangular or substantially rectangular cross-sectional shape is formed by filling the groove having a wedge-shaped or substantially rectangular cross section and curing the ink composition (FIG. 3B). As a method for curing the ionizing radiation curable resin in the ink composition, it can be cured by a normal curing method, that is, irradiation with an electron beam or ultraviolet rays. For example, in the case of electron beam curing, 50 to 50 emitted from various electron beam accelerators such as a Cockloft Walton type, a bandegraph type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type An electron beam having an energy of 1000 keV, preferably 100 to 300 keV is used. In the case of ultraviolet curing, ultraviolet rays emitted from rays such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. Available.

<Visibility improvement sheet>
The visibility improving sheet obtained as described above has a substantially trapezoidal or substantially rectangular light transmission part in a cross section in the sheet thickness direction, and a substantially triangular or substantially rectangular cross section arranged in parallel between the light transmission parts. The light absorption part which has. The light transmission part is an element having a substantially trapezoidal or substantially rectangular cross section arranged so that one sheet surface side is an upper side and the other sheet surface side is a lower side. The light absorbing portion is an element having a substantially triangular or substantially rectangular cross section formed between the light transmitting portions. The surfaces corresponding to the base of the triangle or the upper side of the rectangle are arranged in parallel so as to face the sheet surface on the upper side of the light transmission part. Thereby, one side of the visibility improving sheet is constituted by the upper side of the light absorption part (the groove filled with the ink composition) and the upper side of the light transmission part. It is preferable that the oblique side of the substantially triangular shape or the long side of the substantially rectangular shape in the light absorbing portion has an angle in the range of 0 to 3 ° with respect to the normal direction of the visibility improving sheet surface. When the angle of the hypotenuse is close to 0 degrees, the cross section is substantially a rectangular shape.

  The light absorbing portion has a refractive index that is the same as or smaller than the refractive index of the light transmitting portion. When the refractive index between the light transmitting part and the light absorbing part is as described above, the image light from the light source incident on the light transmitting part under a predetermined condition is appropriate at the boundary surface between the light absorbing part and the light transmitting part. It is possible to provide a bright image to the observer. Further, since a part of the external light from the observer side is absorbed, the contrast is improved. Further, stray light that is incident on the inner side of the light absorbing portion without being reflected at the boundary surface between the light absorbing portion and the light transmitting portion is absorbed by the colored fine particles in the light absorbing portion. In addition, since the external light from the observer side incident at a predetermined angle can be appropriately absorbed, the contrast can also be improved.

  In addition, two layers for improving the visibility may be overlapped, and in this case, each visibility improving sheet may have a different structure. For example, the width, pitch, depth (depth of the wedge-shaped portion) and shape of the light absorbing portion are changed between the first layer visibility improving sheet and the second layer visibility improving sheet, or the thickness of the light absorbing portion. The direction of the direction can be changed, and the bias angle of the light absorption unit with respect to the image light (the inclination angle of the light absorption unit with respect to the horizontal direction) can be changed. Moreover, the material (the kind of resin and the density | concentration of colored fine particles) which forms a light absorption part can also be changed. For example, the second layer is designed to cut external light efficiently and emphasize the improvement of contrast, and the second layer is designed to focus on the front brightness improvement effect using reflection, and the effect is changed in each layer. It is preferable.

  The visibility improvement sheet | seat by this invention may contain the other functional layer employ | adopted as the conventional visibility improvement sheet | seat and the viewing angle expansion member. Specifically, an antireflection layer, an adhesive layer, an electromagnetic wave shielding layer, a wavelength filter layer, an antiglare layer, a hard coat layer, and the like may be appropriately combined. The stacking order and the number of stacks of these functional layers can be appropriately determined according to the use of the visibility improving sheet to be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
<Preparation of ink composition>
Resin beads obtained by kneading carbon black (RCF # 45, manufactured by Mitsubishi Chemical Corporation) with an average particle size of 24 nm into acrylic resin (Hyperl, manufactured by Nemoto Kogyo Co., Ltd.) were used. The amount of carbon black kneaded was 35% based on the weight of the acrylic resin. It was 1.0 micrometer when the average particle diameter of this resin bead was measured with the particle size distribution measuring apparatus (LA-920, Horiba, Ltd. make).

  As ionizing radiation curable resins, 33.6 parts by weight of urethane acrylate, 14.4 parts by weight of epoxy acrylate, 28 parts by weight of tripropylene glycol diacrylate, 4 parts by weight of methoxytriethylene glycol acrylate, and an acrylic bifunctional monomer (Osaka Organic) (Chemical Industry Co., Ltd.) 240 parts by mass and 4 parts by mass of Irgacure 184 as a photopolymerization initiator were mixed, and 21 parts by mass of the above resin beads were further mixed to prepare an ink composition. . The viscosity of the obtained ink composition was 3,800 mPa · s when measured in a 25 ° C. environment using a B-type viscometer.

<Preparation of a sheet for improving visibility>
On a PET substrate (A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm, a urethane mold curable resin having a refractive index of 1.55 after curing is subjected to continuous molding using a molding die, and a plurality of light A transmission part and a wedge-shaped groove provided in parallel between the light transmission parts were formed. Next, the ink composition obtained above was filled into wedge-shaped grooves using a die coater. The ink filling pressure of the die coater at this time was 3.5 kgf / cm ² . Subsequently, after the excess ink composition was scraped off with a metal doctor blade, the light absorbing part was formed by irradiating with ultraviolet rays to cure the ink composition. When the cross section of the obtained visibility improving sheet was observed with an optical microscope, the opening width of the light absorption part (groove) was 12 μm, the width of the bottom of the groove was 10 μm, and the depth was 105 mm. It was also confirmed that the ink composition was filled to the bottom of the groove. In addition, voids due to bubbles could not be confirmed in the light absorbing portion.

Comparative Example 1
In Example 1, a visibility improving sheet was prepared in the same manner as in Example 1 except that a dispenser was used instead of the die coater for ink filling. Ink filling with the dispenser was performed under atmospheric pressure (1 kgf / cm ² ). When the cross section of the obtained visibility improving sheet was observed with an optical microscope, the opening width of the light absorption part (groove) was 12 μm, the width of the bottom of the groove was 10 μm, and the depth was 105 mm. Further, it was confirmed that the ink composition was not filled up to the bottom of the groove, and there existed voids that seemed to be bubbles in part.

<Contrast evaluation>
Next, the obtained visibility improving sheet was evaluated for contrast by the following evaluation method. First, the luminance of the black screen in a state where the visibility improving sheet was pasted on the display screen and the luminance of the black screen in a state before pasting the visibility improving sheet on the display screen were visually observed. The evaluation criteria for contrast were as follows.
明 ら か に: Obviously black ○: Black equal to or greater than △: Almost equal black ×: Black equal to or less than equivalent The evaluation results are as shown in Table 1 below.

  As is clear from the results in Table 1, the visibility improving sheet of the example has no voids such as bubbles in the light absorbing portion. Therefore, as shown in Comparative Example 1, the visibility improving sheet has a void in the light absorbing portion. In comparison, it was found that the contrast was remarkably improved.

DESCRIPTION OF SYMBOLS 1 Base material 2 Light transmissive part 3 Groove 4 Colored ink composition 5 Light absorption part 6 Mold 7 Coating apparatus (die coater)
8 Ink scraper

Claims (14)

A method of manufacturing a visibility improving sheet comprising: a light transmitting portion arranged in parallel at a predetermined interval; and a light absorbing portion having a substantially rectangular cross section provided in parallel between the light transmitting portions,
By forming the light transmission part so as to be arranged in parallel at a predetermined interval, a groove having a substantially rectangular cross section provided in parallel between the light transmission parts is formed,
Filling the groove with an ink composition comprising a transparent ionizing radiation curable resin composition and colored fine particles while applying pressure;
A method comprising the steps of: The method according to claim 1, wherein the pressurization at the time of filling is performed in a range of ^{2 to} 15 kgf / cm ² .   The method according to claim 1 or 2, wherein the ink filling is performed using a coating apparatus selected from a die coater, a bar coater, a roll coater, or a knife coater.   The method according to claim 3, wherein a discharge speed of ink from the coating device is 1 to 1.5 times a line speed.   The method according to any one of claims 1 to 4, further comprising performing a hydrophilization treatment on the groove surface before filling the groove with ink.   The method according to claim 5, wherein the hydrophilization treatment is performed by an atmospheric pressure plasma treatment.   The method according to claim 1, wherein an opening width of the groove is 8 to 12 μm.   The hypotenuse of the light absorption part which has the said substantially trapezoid cross section thru | or a substantially rectangular cross section has an angle of 0-3 degrees with respect to the normal line direction of a visibility improvement sheet | seat surface. the method of.   The method according to any one of claims 1 to 8, wherein the colored fine particles comprise resin beads in which carbon black is kneaded in a resin.   The method according to claim 9, wherein the carbon black has an average particle size of 10 to 500 nm.   The ionizing radiation curable resin composition is selected from polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and polyhydric alcohols. The method as described in any one of Claims 1-10 which consists of oligomers or prepolymers, such as (meth) allylate of a compound.   The method according to claim 1, wherein the ink composition has a viscosity of 500 to 5,000 mPa · s.   The visibility improvement sheet | seat obtained by the method as described in any one of Claims 1-12.   A display device comprising the visibility improving sheet according to claim 13.

Images