JP6776591B2 - Wavelength conversion sheet and backlight unit - Google Patents

Description

The present invention relates to a light emitter protective film, a wavelength conversion sheet and a backlight unit.

In a light emitting unit such as a backlight unit and an electroluminescence light emitting unit of a liquid crystal display, the performance may be deteriorated when the light emitting body in the light emitting body layer comes into contact with oxygen or water vapor for a long time. For this reason, these light emitting units often employ a structure in which a gas barrier film having a gas barrier layer formed on a polymer film is arranged on one or both sides of a light emitting body layer including a light emitting body. For example, Patent Document 1 discloses a color conversion member (wavelength conversion sheet) having a structure in which both side surfaces of two color conversion layers (fluorescent layer) are sandwiched between barrier films.

Japanese Unexamined Patent Publication No. 2011-13567

As a means for preventing the invasion of oxygen or water vapor, a film having a gas barrier property (hereinafter, referred to as "barrier film") is widely adopted. The barrier film has a laminated structure including, for example, a base material such as a polyethylene terephthalate (PET) film and a gas barrier layer laminated on at least one surface of the base material. When the barrier film is used for the light emitting unit, the barrier film is required to have high transparency in addition to the gas barrier property in order to efficiently transmit the light from the light emitting body through the barrier film. Further, since the barrier film is continuously exposed to the heat from the luminescent material layer, it is desired that the barrier film can maintain its transparency for a long period of time even when exposed to a high temperature environment.

The present invention has been made in view of the above circumstances, and is a luminescent material protective film having excellent gas barrier properties and transparency, and capable of maintaining transparency for a long period of time even when exposed to a high temperature environment. Another object of the present invention is to provide a wavelength conversion sheet and a backlight unit obtained by using the same.

The present invention comprises a first barrier film having a first base material and a first barrier layer formed on one surface of the first base material, and one surface of the second base material and the second base material. Provided is a luminescent material protective film including a second barrier film having a second barrier layer formed on the surface and a first adhesive layer containing a reaction product of an epoxy compound and an amine compound. In the light emitting body protective film, the first barrier film and the second barrier film are bonded to each other via the first adhesive layer so that the first barrier layer and the second barrier layer face each other. The amount of change Δb ^* of the color coordinates b ^* in the L ^* a ^* b ^* color system is 1.00 or less before and after exposure for 1000 hours in an environment with an air temperature of 85 ° C.

In the luminescent material protective film, two barrier films are used, and these are bonded to each other via a first adhesive layer containing a reaction product of an epoxy compound and an amine compound, so that excellent gas barrier properties can be obtained. Can be done. On the other hand, when a reaction product of an epoxy compound and an amine compound is used as an adhesive layer, the adhesive layer often turns yellow when exposed to a high temperature environment for a long time, and the transparency may decrease. However, in the light emitting body protective film, since the two barrier films are bonded so that the barrier layers face each other, oxygen entering into the first adhesive layer can be further reduced. Therefore, the luminescent material protective film has excellent gas barrier properties and transparency, and can maintain its transparency for a long period of time even when exposed to a high temperature environment.

It is preferable that the light emitting body protective film further includes a second adhesive layer and a support base material, and the support base material is bonded to the other surface of the second base material via the second adhesive layer. .. According to the luminescent material protective film, there is a tendency that the generation of wrinkles due to heat and tension applied during roll-to-roll production can be reduced. Further, even if wrinkles are generated in the production of the first barrier film and the second barrier film, there is a tendency that the wrinkles of the finally obtained light emitting body protective film can be sufficiently reduced.

In the luminescent material protective film, it is preferable that the water vapor permeability of both the first barrier film and the second barrier film is 100 mg / (m ² · day) or less. It is preferable that the luminescent material protective film further includes a coating layer, and the coating layer is provided so as to be the outermost surface of either one.

In the luminescent material protective film, the first barrier layer includes a first inorganic thin film layer and a first gas barrier coating layer, and the second barrier layer includes a second inorganic thin film layer and a second gas barrier coating layer. Is preferable. When the barrier layer has the above structure, the gas barrier property of the light emitting body protective film tends to be further improved.

In the present invention, the first protective film made of the light emitting body protective film, the phosphor layer, and the second protective film are laminated in this order, and the first protective film is the first barrier film. Provided is a wavelength conversion sheet in which the film is arranged so as to face the phosphor layer side.

The present invention also provides a backlight unit including a light source, a light guide plate, and the wavelength conversion sheet.

According to the present invention, a luminescent material protective film having excellent gas barrier properties and transparency and capable of maintaining transparency for a long period of time even when exposed to a high temperature environment, and a luminescent material protective film obtained by using the same. A wavelength conversion sheet and a backlight unit can be provided.

It is the schematic sectional drawing of the light emitting body protection film which concerns on one Embodiment of this invention. It is the schematic sectional drawing of the light emitting body protective film which concerns on another embodiment of this invention. It is the schematic sectional drawing of the wavelength conversion sheet which concerns on one Embodiment of this invention. It is the schematic sectional drawing of the backlight unit which concerns on one Embodiment of this invention.

Hereinafter, a plurality of embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted. Further, unless otherwise specified, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

(Luminescent protective film)
FIG. 1 is a schematic cross-sectional view of a light emitting body protective film according to an embodiment of the present invention. The light emitting body protective film 10 of FIG. 1 includes a first barrier film 1, a second barrier film 2, and a first adhesive layer 11, and the first barrier film 1 and the second barrier film 2 form a first adhesive layer 11. They are pasted together. A coating layer 7 is provided on the surface of the second barrier film 2 opposite to the first barrier film 1, if necessary. Since the illuminant protective film 10 includes two barrier films, high gas barrier properties can be obtained. Further, in the present embodiment, the first adhesive layer 11 contains a reaction product of an epoxy compound and an amine compound. The first adhesive layer 11 can obtain not only the adhesiveness between the barrier films but also the gas barrier property superior to that of the adhesive layer obtained by using other materials.

The first barrier film 1 has a first base material 1a and a first barrier layer 1b formed on one surface of the first base material 1a, and the second barrier film 2 has a second base material 2a and a second base material 2a. It has a second barrier layer 2b formed on one surface of the base material 2a, and the first barrier layer 1b and the second barrier layer 2b face each other. In other words, the first adhesive layer 11 is arranged so as to be adjacent to both the first barrier layer 1b and the second barrier layer 2b, and is sandwiched by these barrier layers. When another layer is arranged between the first barrier layer 1b and the second barrier layer 2b and the first adhesive layer 11, a small amount of oxygen penetrates from the end of the other layer and is supplied to the adhesive layer. There is a possibility. However, the light emitting body protective film 10 having the above layer structure can suppress the invasion of such a small amount of oxygen, and as a result, even when exposed to a high temperature environment for a long time, the first adhesive layer 11 Yellowing, and eventually yellowing of the light emitting body protective film 10 as a whole can be suppressed, and sufficiently high transparency can be maintained as the light emitting body protective film. Before and after exposing the illuminant protective film 10 having such a configuration to an environment at an air (1 atm) medium temperature of 85 ° C. for 1000 hours, the L ^* a ^* b ^* color coordinates b ^* of the illuminant protective film The amount of change Δb ^{* of} is 1.00 or less. The amount of change Δb ^* is preferably 0.50 or less, more preferably 0.30 or less, and even more preferably 0.10 or less. When the amount of change Δb ^* is within the above range, the illuminant protective film 10 can maintain its transparency for a long period of time even when exposed to a high temperature environment. The L ^* a ^* b ^* color system is a color system standardized by the CIE.

The first base material 1a and the second base material 2a are base materials that form the first barrier layer 1b and the second barrier layer 2b, respectively, and can suppress damage during processing, distribution, and the like. From the viewpoint of the transparency of the light emitting body protective film 10, the total light transmittance of the first base material 1a and the second base material 2a is preferably 85% or more. Examples of such a base material include, but are limited to, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon; polyolefins such as polypropylene and cycloolefins; polycarbonates; and triacetyl cellulose. Not done. Further, it is preferable that the first base material 1a and the second base material 2a are biaxially stretched. The thickness of the first base material 1a and the second base material 2a is preferably 9 to 100 μm, more preferably 12 to 50 μm. When the thicknesses of the base materials 1a and 2a are 9 μm or more, the strength of the base materials 1a and 2a can be sufficiently secured, and when the thickness is 100 μm or less, a long roll (rolls of the barrier films 1 and 2) is formed. It can be manufactured efficiently and economically.

The thickness of the first base material 1a and the thickness of the second base material 2a may be the same or different. From the viewpoint of making the thickness of the wavelength conversion sheet thinner, the thickness of the first base material 1a on the side closer to the light emitting body layer may be made thinner than the thickness of the second base material 2a on the side farther from the light emitting body layer. Since water and gas permeate mainly from the surface of the wavelength conversion sheet, the thickness of the second base material 2a is made relatively thick to prevent the permeation of water and oxygen from the surface, and the first base material 1a. The thickness of the entire wavelength conversion sheet can be reduced by making the thickness relatively thin. Since the permeation of water and oxygen occurs not only from the surfaces of the barrier films 1 and 2 but also from the end faces, the thinner the thickness of the first base material 1a, the more the invasion of water and oxygen from the end faces can be suppressed. it can. The thickness of the first base material 1a is preferably 40 μm or less.

A first barrier layer 1b and a second barrier layer 2b are formed on the first base material 1a and the second base material 2a, respectively, via an anchor coat layer (not shown), if necessary. Examples of the anchor coat layer include polyester resin, and the thickness of the anchor coat layer is about 0.01 to 1 μm.

The first barrier layer 1b preferably includes the first inorganic thin film layer 1v and the first gas barrier coating layer 1c. That is, in the first barrier layer 1b, the first inorganic thin film layer 1v is provided on one surface of the first base material 1a, and the first gas barrier coating layer 1c is provided on the first inorganic thin film layer 1v. It is a configuration. The second barrier layer 2b preferably includes a second inorganic thin film layer 2v and a second gas barrier coating layer 2c. That is, in the second barrier layer 2b, the second inorganic thin film layer 2v is provided on one surface of the second base material 2a, and the second gas barrier coating layer 2c is provided on the second inorganic thin film layer 2v. It is a configuration.

The inorganic thin film layers 1v and 2v are not particularly limited, and for example, aluminum oxide, silicon oxide, magnesium oxide, or a mixture thereof can be used. Among these, it is desirable to use aluminum oxide or silicon oxide from the viewpoint of barrier properties and productivity.

The inorganic thin film layers 1v and 2v contain an inorganic compound, and preferably contain a metal oxide. Examples of the metal oxide include oxides of metals such as aluminum, copper, silver, yttrium, tantalum, silicon, and magnesium. The metal oxide is preferably silicon oxide (SiO _x , x is 1.0 to 2.0) because it is inexpensive and has excellent gas barrier properties. When x is 1.0 or more, good gas barrier properties tend to be easily obtained.

The inorganic thin film layers 1v and 2v are preferably inorganic vapor deposition film layers formed by a thin film deposition method from the viewpoint of manufacturing cost. When the inorganic thin film layers 1v and 2v are inorganic vapor deposition film layers, holes may be generated in the inorganic thin film layers 1v and 2v due to the scattering (splash) of the vapor deposition material. Although the frequency of splash occurrence is low, the holes generated by the splash are relatively large defects and can be holes that penetrate the base materials 1a and 2a as well. Therefore, in a protective film with splash holes, it can be an oxygen ingress route. In particular, when holes are formed in the first base material 1a and the first inorganic thin film layer 1v arranged on the side close to the light emitting body layer, dark spots are more likely to be generated in the light emitting body layer around the holes. However, if the oxygen permeability of the first adhesive layer 11 described later is 1000 cm ³ / (m ² · day · atm) or less, even if there is a relatively large defect as described above, there is no defect. Similarly, it becomes easier to suppress the occurrence of dark spots. Therefore, the manufacturing cost is reduced because the first inorganic thin film layer 1v is an inorganic vapor deposition film layer and the oxygen permeability of the first adhesive layer 11 is 1000 cm ³ / (m ² · day · atm) or less. At the same time, it becomes easier to suppress the occurrence of dark spots.

The thickness (film thickness) of the inorganic thin film layers 1v and 2v is preferably 5 to 500 nm, and more preferably 10 to 100 nm, respectively. When the film thickness is 5 nm or more, a uniform film is easily formed, and the gas barrier function tends to be more sufficiently fulfilled. On the other hand, when the film thickness is 500 nm or less, the inorganic thin film layer can maintain sufficient flexibility, and more reliably prevents the thin film from cracking due to external factors such as bending and pulling after the film formation. Tend to be able. The thickness of the first inorganic thin film layer 1v and the thickness of the second inorganic thin film layer 2v may be the same or different.

The first gas barrier coating layer 1c and the second gas barrier coating layer 2c are provided to prevent various secondary damages in the subsequent process and to impart high barrier properties, respectively. These gas barrier coating layers 1c and 2c are at least one selected from the group consisting of hydroxyl group-containing polymer compounds, metal alkoxides, metal alkoxide hydrolysates and metal alkoxide polymers from the viewpoint of obtaining excellent barrier properties. It is preferably contained as an ingredient.

Examples of the hydroxyl group-containing polymer compound include water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone and starch. The hydroxyl group-containing polymer compound is preferably polyvinyl alcohol from the viewpoint of barrier properties. These are not limited to one type, but a plurality of types can be used in combination.

Examples of the metal alkoxide include compounds represented by the following formula (1).
M (OR ¹ ) _m (R ² ) _nm ... (1)

In the above formula (1), R ¹ and R ² are independently monovalent organic groups having 1 to 8 carbon atoms, and are preferably alkyl groups such as a methyl group and an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, Zr. m is an integer of 1 to n. Examples of the metal alkoxide include tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] and triisopropoxyaluminum [Al (O-iso-C ₃ H ₇ ) ₃ ]. The metal alkoxide is preferably tetraethoxysilane or triisopropoxyaluminum because it is relatively stable in an aqueous solvent after hydrolysis. Examples of the metal alkoxide hydrolyzate include silicic acid (Si (OH) ₄ ), which is a hydrolyzate of tetraethoxysilane, and aluminum hydroxide (Al (OH) ₃ ), which is a hydrolyzate of tripropoxyaluminum. ) Etc. can be mentioned. These are not limited to one type, but a plurality of types can be used in combination.

The thickness (film thickness) of the gas barrier coating layers 1c and 2c is preferably 50 to 1000 nm, and more preferably 100 to 500 nm, respectively. When the film thickness is 50 nm or more, a more sufficient gas barrier property tends to be obtained, and when the film thickness is 1000 nm or less, a more sufficient flexibility tends to be maintained. The thickness of the first gas barrier coating layer 1c and the thickness of the second gas barrier coating layer 2c may be the same or different.

The water vapor permeability of the barrier films 1 and 2 is preferably 100 mg / (m ² · day) or less, and more preferably 50 mg / (m ² · day) or less. When the water vapor permeability of the barrier films 1 and 2 is 100 mg / (m ² · day) or less, more excellent gas barrier properties tend to be obtained.

The first adhesive layer 11 is obtained by curing a thermosetting adhesive containing an epoxy compound and an amine compound, and contains a reaction product of the epoxy compound and the amine compound. The light emitting body protective film 10 provided with the first adhesive layer 11 obtained as described above can obtain a higher gas barrier property. The oxygen permeability of the first adhesive layer 11 is preferably 1000 cm ³ / (m ² · day · atm) or less in the thickness direction at a thickness of 5 μm. The oxygen permeability is more preferably 500 cm ³ / (m ² · day · atm) or less, further preferably 100 cm ³ / (m ² · day · atm) or less, and 50 cm ³ / (m ² · atm) or less. It is more preferably less than or equal to day · atm), and particularly preferably less than or equal to 10 cm ³ / (m ² · day · atm). Oxygen permeability of the first adhesive layer ^11, by at most ^{1000cm 3 / (m 2 · day} · atm), when used in the light emitting unit, even if the barrier film had a defect, the defective There is a tendency to suppress the generation of dark spots in the surrounding illuminant layer. The lower limit of the oxygen permeability is not particularly limited, but is, for example, 0.1 cm ³ / (m ² · day · atm).

The thickness of the first adhesive layer 11 is preferably 0.5 to 50 μm, more preferably 1 to 20 μm, and even more preferably 2 to 6 μm. When the thickness of the first adhesive layer 11 is 0.5 μm or more, the adhesion between the first barrier film 1 and the second barrier film 2 can be easily obtained, and when the thickness is 50 μm or less, the adhesion is easily obtained. It becomes easier to obtain better gas barrier properties and transparency.

The coating layer (matte layer) 7 is provided on the other surface of the second base material 2a in order to exert one or more optical functions, antistatic functions, or scratch prevention functions, and is the most of the light emitting body protective film 10. It is the surface. The optical function is not particularly limited, and examples thereof include an interference fringe (moire) prevention function, an antireflection function, and a diffusion function. Among these, the coating layer 7 preferably has at least an interference fringe prevention function as an optical function. In the present embodiment, the case where the coating layer 7 has at least an interference fringe prevention function will be described.

The coating layer 7 is composed of, for example, a binder resin and fine particles. By embedding the fine particles in the binder resin so that a part of the fine particles protrudes from the surface of the coating layer 7, fine irregularities may be generated on the surface of the coating layer 7. By providing the coating layer 7 on the surface opposite to the light emitting body layer in this way, it is possible to more sufficiently prevent the occurrence of interference fringes such as Newton's rings.

The binder resin is not particularly limited, but a resin having excellent optical transparency can be used. More specifically, for example, polyester resin, acrylic resin, acrylic urethane resin, polyester acrylate resin, polyurethane acrylate resin, urethane resin, epoxy resin, polycarbonate resin, polyamide resin, polyimide resin. , Melamine-based resin, phenol-based resin and the like can be used. The binder resin may be any of a thermoplastic resin, a thermosetting resin and a radiation curable resin. Among these, it is desirable to use an acrylic resin having excellent light resistance and optical characteristics. These are not limited to one type, but can be used in combination of a plurality of types.

The fine particles are not particularly limited, but are, for example, inorganic fine particles such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, and alumina, as well as styrene resin, urethane resin, and silicone resin. Organic fine particles such as acrylic resin can be used. These are not limited to one type, but can be used in combination of a plurality of types.

The average particle size of the fine particles is preferably 0.1 to 30 μm, more preferably 0.5 to 10 μm. When the average particle size of the fine particles is 0.1 μm or more, an excellent interference fringe prevention function tends to be obtained, and when it is 30 μm or less, the transparency tends to be further improved. The content of the fine particles in the coating layer 7 is preferably 0.5 to 30% by mass, more preferably 3 to 10% by mass, based on the total amount of the coating layer 7. When the content of the fine particles is 0.5% by mass or more, the light diffusion function and the effect of preventing the occurrence of interference fringes tend to be further improved, and when it is 30% by mass or less, the reduction in brightness is sufficiently suppressed. There is a tendency to be able to do it.

As shown in FIG. 2, the light emitting body protective film 10 may further include a second adhesive layer 22 and a supporting base material 3. In FIG. 2, the support base material 3 is bonded to the other surface of the second base material 2a via the second adhesive layer 22, and the coating layer 7 is formed on the support base material 3 to form the outermost surface. There is. When the illuminant protective film 10 includes the support base material 3, there is a tendency that wrinkles due to heat and tension applied when the illuminant protective film 10 is manufactured by roll-to-roll can be reduced. Further, even if wrinkles are generated in the production of the first barrier film and the second barrier film, there is a tendency that the wrinkles can be sufficiently reduced in the end.

The supporting base material 3 is not particularly limited, but a base material having a total light transmittance of 85% or more is desirable. For example, a polyethylene terephthalate film, a polyethylene naphthalate film, or the like can be used as a base material having high transparency and excellent heat resistance. The thickness of the support base material 3 is preferably 10 to 250 μm, more preferably 25 to 240 μm, further preferably 40 to 210 μm, and particularly preferably 55 to 200 μm. When the thickness of the support base material 3 is 10 μm or more, it becomes easy to sufficiently secure the strength of the support base material 3 for obtaining the effect of improving the wrinkles of the light emitting body protective film 10, and when the thickness is 250 μm or less. , It becomes easy to prevent the total thickness of the wavelength conversion sheet from becoming excessively thick.

As shown in FIG. 2, the second adhesive layer 22 is provided between the barrier film 2 and the support base material 3 in order to bond and laminate the barrier film 2 and the support base material 3. Examples of the adhesive constituting the second adhesive layer 22 include acrylic adhesives, epoxy adhesives, urethane adhesives and the like. Examples of the pressure-sensitive adhesive constituting the second adhesive layer 22 include an acrylic pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a starch paste-based adhesive. The pressure-sensitive adhesive is preferably an acrylic pressure-sensitive adhesive. By using the acrylic pressure-sensitive adhesive, it becomes easy to maintain the transparency of the second adhesive layer 22 for a long period of time. The thickness of the second adhesive layer 22 is preferably 0.5 to 50 μm, more preferably 1 to 20 μm, and even more preferably 2 to 6 μm. When the thickness of the second adhesive layer 22 is 0.5 μm or more, the adhesion between the barrier film 2 and the supporting base material 3 can be easily obtained, and when the thickness is 50 μm or less, more excellent gas barrier property can be obtained. It becomes easy to be.

Next, a method for manufacturing the light emitting body protective film 10 will be described. First, for example, barrier films 1 and 2 are manufactured by a roll-to-roll method. Specifically, the inorganic thin film layer 1v is laminated on one surface of the first base material 1a by, for example, a thin film deposition method. Next, a coating agent containing an aqueous solution or a water / alcohol mixed solution as a main component containing at least one component selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a metal alkoxide hydrolyzate, and a metal alkoxide polymer is applied. The gas barrier coating layer 1c is formed by applying it on the surface of the inorganic thin film layer 1v and drying it at, for example, 80 to 250 ° C. As a result, the first barrier film 1 in which the barrier layer 1b (inorganic thin film layer 1v and gas barrier coating layer 1c) is provided on one surface of the first base material 1a can be obtained. By performing the same operation as this, a second barrier film 2 in which the barrier layer 2b (inorganic thin film layer 2v and gas barrier coating layer 2c) is provided on one surface of the second base material 2a can be obtained.

An anchor coat layer may be provided between the base material and the inorganic thin film layer in order to improve the adhesion between the base material and the inorganic thin film layer laminated on the surface thereof. The anchor coat layer can be formed by applying the above-mentioned resin-containing solution onto a substrate and drying and curing it at, for example, 50 to 200 ° C. The thickness of the anchor coat layer is preferably in the range of 5 to 500 nm, and more preferably in the range of 10 to 100 nm.

After producing the first barrier film 1 and the second barrier film 2, respectively, the laminated film is produced by laminating them with the first adhesive layer 11. Specifically, using a laminating device, the barrier layer 1b of the first barrier film 1 and the barrier layer 2b of the second barrier film 2 are opposed to each other by a roll-to-roll method to form the first adhesive layer 11. A laminated film is obtained by laminating the barrier films 1 and 2 with an adhesive (or an adhesive) and drying the adhesive.

Further, the laminated film and the supporting base material 3 may be bonded to each other. Specifically, an adhesive (or adhesive) constituting the second adhesive layer 22 is used by using a laminating device and using a roll-to-roll method to make the second base material 2a of the laminated film and the supporting base material 3 face each other. The laminated film and the supporting base material 3 are bonded together with the agent). A protective film is obtained by drying the adhesive.

Next, the coating layer 7 is formed on one surface of the protective film (for example, the surface of the supporting base material 3) by the roll-to-roll method, if necessary. Specifically, a coating solution in which a binder resin, fine particles, and a solvent, if necessary, is mixed on one surface of the protective film (for example, the surface of the supporting base material 3) is applied and dried to obtain a coating layer. 7 is formed. As a result, a protective film with a coating layer is obtained. As described above, the light emitting body protective film 10 is obtained.

(Wavelength conversion sheet)
FIG. 3 is a schematic cross-sectional view of a wavelength conversion sheet according to an embodiment of the present invention. The wavelength conversion sheet is a sheet capable of converting a part of the wavelengths of light from the light source of the backlight unit for a liquid crystal display. In FIG. 3, the wavelength conversion sheet 100 is provided as a first protective film and a second protective film on one surface side and the other surface side of the phosphor layer 50 and the phosphor layer 50, respectively. The films 10 and 10 are provided. That is, the illuminant protective film 10, the phosphor layer 50, and the illuminant protective film 10 are laminated in this order. The wavelength conversion sheet 100 has a structure in which the phosphor layer 50 is wrapped (that is, sealed) between the pair of light emitter protective films 10 and 10. The pair of light emitter protective films 10 and 10 are arranged so that their first barrier films face the phosphor layer 50 side.

The phosphor layer 50 is a thin film having a thickness of several tens to several hundreds of μm, and contains a sealing resin 51 and a phosphor 52 as shown in FIG. The inside of the sealing resin 51 is sealed with one or more phosphors 52 mixed therein. When the phosphor layer 50 and the pair of light emitter protective films 10 and 10 are laminated, the sealing resin 51 serves to join them and fill the voids between them. The phosphor layer 50 may be a stack of two or more phosphor layers in which only one type of phosphor 52 is sealed. As the two or more types of phosphors 52 used for the one layer or two or more layers of phosphors, those having the same excitation wavelength are selected. This excitation wavelength is selected based on the wavelength of the light emitted by the light source L. The fluorescent colors of the two or more types of phosphors 52 are different from each other. When a blue light emitting diode (blue LED) is used as a light source, the fluorescent colors are red and green. The wavelength of each fluorescence and the wavelength of the light emitted by the light source are selected based on the spectral characteristics of the color filter. The peak wavelength of fluorescence is, for example, 610 nm for red and 550 nm for green.

As the sealing resin 51, for example, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like can be used. These resins may be used alone or in combination of two or more.

Examples of the thermoplastic resin include cellulose derivatives such as acetyl cellulose, nitro cellulose, acetyl butyl cellulose, ethyl cellulose and methyl cellulose; vinyl acetate and its copolymer, vinyl chloride and its copolymer, and vinylidene chloride and its copolymer. Vinyl-based resins such as; acetal resins such as polyvinylformal and polyvinylbutyral; acrylic resins and their copolymers, methacrylic resins and their copolymers and the like; acrylic resins; polystyrene resins; polyamide resins; linear polyester resins; fluorine Resin; Also, polycarbonate resin and the like can be used. Examples of the thermosetting resin include phenol resin, urea melamine resin, polyester resin, silicone resin and the like. Examples of the ultraviolet curable resin include photopolymerizable prepolymers such as epoxy acrylate, urethane acrylate, and polyester acrylate. Further, it is also possible to use these photopolymerizable prepolymers as a main component and a monofunctional or polyfunctional monomer as a diluent.

Quantum dots are preferably used as the phosphor 52. Examples of the quantum dots include those in which the core as a light emitting portion is coated with a shell as a protective film. Examples of the core include cadmium selenide (CdSe) and the like, and examples of the shell include zinc sulfide (ZnS) and the like. Quantum efficiency is improved by covering the surface defects of CdSe particles with ZnS having a large bandgap. Further, the phosphor 52 may have a core double-coated with a first shell and a second shell. In this case, CsSe can be used for the core, zinc selenide (ZnSe) can be used for the first shell, and ZnS can be used for the second shell. Further, YAG: Ce or the like can be used as the phosphor 52 other than the quantum dots.

The average particle size of the phosphor 52 is preferably 1 to 20 nm. The thickness of the phosphor layer 50 is preferably 1 to 500 μm. The content of the phosphor 52 in the phosphor layer 50 is preferably 1 to 20% by mass, more preferably 3 to 10% by mass, based on the total amount of the phosphor layer 50.

In the above embodiment of the wavelength conversion sheet 100, the light emitting body protective film 10 is provided on both sides of the phosphor layer 50, but may be provided only on one surface of the phosphor layer 50. That is, a light emitting body protective film 10 may be provided as a first protective film on one surface of the phosphor layer 50, and another protective film may be provided as a second protective film on the other surface.

The method for manufacturing the wavelength conversion sheet 100 is not particularly limited, and examples thereof include the following methods. For example, the phosphor 52 is dispersed in the sealing resin 51, and the prepared phosphor dispersion is applied onto the surface of the light emitter protective film 10 on the first barrier film 1 side, and then another light emitter protective film is applied to the coated surface. The wavelength conversion sheet 100 can be manufactured by laminating 10 and curing the phosphor layer 50.

FIG. 4 is a schematic cross-sectional view of a backlight unit obtained by using the wavelength conversion sheet. In FIG. 4, the backlight unit 200 includes a light source L and a wavelength conversion sheet 100. Specifically, in the backlight unit 200, the wavelength conversion sheet 100, the light guide plate G, and the reflector R are arranged in this order, and the light source L is arranged on the side of the light guide plate G (the surface direction of the light guide plate G). To. The thickness of the light guide plate G is, for example, 100 to 1000 μm.

The light guide plate G and the reflector R efficiently reflect and guide the light emitted from the light source L, and known materials are used. As the light guide plate G, for example, acrylic, polycarbonate, cycloolefin film and the like are used. The light source L is provided with, for example, a plurality of blue light emitting diode elements. The light emitting diode element may be a purple light emitting diode or a light emitting diode having a lower wavelength. Light emitted from the light source L is incident on the light guide plate G (D ₁ direction), and enters the phosphor layer 50 with the reflection and refraction, etc. (D ₂ direction). The light that has passed through the phosphor layer 50 becomes white light by mixing the light before passing through the phosphor layer 50 with the yellow light generated in the phosphor layer 50.

Hereinafter, the present invention will be specifically described with reference to examples, but the scope of the present invention is not limited thereto.

(Example 1)
[Preparation of illuminant protective film]
The barrier film was prepared by a roll-to-roll method as follows. First, silicon oxide is provided as an inorganic thin film layer at a thickness of 30 nm on one side of a polyethylene terephthalate (PET) film having a thickness of 30 μm as a base material by a vacuum vapor deposition method, and further, a gas barrier property with a thickness of 300 nm is provided on the inorganic thin film layer. A coating layer was formed. This gas barrier coating layer was formed by applying a coating liquid containing tetraethoxysilane and polyvinyl alcohol by a wet coating method. As a result, a roll of a barrier film having a barrier layer composed of an inorganic thin film layer and a gas barrier coating layer provided on one surface of the base material was obtained. A roll of a barrier film having the same composition as this barrier film was separately produced. The water vapor permeability of the resulting barrier film was measured water vapor permeability by a method analogous infrared sensor method JIS K 7129, it was ^{50mg / (m 2 · day)} . A water vapor permeability measuring device (trade name: Permatran, manufactured by MOCON) was used for measuring the water vapor permeability. The temperature of the permeation cell was 40 ° C., the relative humidity of the high humidity chamber was 90% RH, and the relative humidity of the low humidity chamber was 0% RH.

The two barrier films obtained as described above were pasted together. A two-component epoxy adhesive consisting of an epoxy resin main agent and an amine-based curing agent is used for bonding, and an adhesive layer (oxygen permeability: 5 cm ³ / (m ² · day)) having a film thickness of 5 μm after curing is used. -Atm)) was formed, and a film was prepared in which the gas barrier coating layers of the two barrier films were laminated so as to face each other. The oxygen permeability of the adhesive layer was measured as follows. The above-mentioned two-component type so that the film thickness after curing is 5 μm on a stretched polypropylene (OPP) film (oxygen permeability: 3000 cm ³ / (m ²・ day ・ atm) (measurement limit) or more) having a thickness of 20 μm. An epoxy adhesive film is formed to prepare a sample for evaluation, and using a differential pressure type gas measuring device (GTR-10X, manufactured by GTR Tech), the temperature is 30 ° C. according to the method described in JIS K7126-1 (Annex 1). The oxygen permeability of the sample under a 70% RH environment was measured.

The laminated film obtained as described above and a PET film (supporting base material) having a thickness of 30 μm were laminated. An acrylic pressure-sensitive adhesive was used for bonding, and an adhesive layer was formed so that the thickness after lamination was 2 μm. As a result, a roll of a protective film (before forming the coating layer) in which an adhesive layer was interposed between the laminated film (base material side) and the supporting base material was obtained.

A coating layer (mat layer) having a thickness of 3 μm was formed on the surface of the supporting base material of the protective film obtained as described above. This coating layer was formed by applying a coating liquid containing an acrylic resin and silica fine particles (average particle size 3 μm) by a wet coating method. As a result, a roll of a protective film with a coating layer was obtained.

[Preparation of wavelength conversion sheet]
As the first protective film and the second protective film, two obtained protective films with a coating layer were prepared. After mixing CdSe / ZnS 530 (trade name, manufactured by SIGMA-ALDRICH) as a quantum dot with an epoxy-based photosensitive resin, the mixed solution is applied to the base material side of the first protective film, and the second protective film is applied thereto. A wavelength conversion sheet was obtained by laminating and UV curing laminating.

(Comparative Example 1)
The same as in Example 1 except that the two barrier films are laminated so that the base materials face each other to prepare a laminated film, and the supporting base material is bonded to the laminated film (gas barrier coating layer side). , A roll of a protective film with a coating layer, and a wavelength conversion sheet were obtained.

[Evaluation of illuminant protective film]
The films with the coating layer obtained in Examples and Comparative Examples were exposed to air at 85 ° C. for 1000 hours, and the films with the coating layer before and after the exposure were prepared respectively.

(L ^* a ^* b ^* Change amount Δb ^* of color coordinates b ^* in the color system)
The L ^* a ^* b ^* color coordinates b ^* in the color system of the film with the coating layer before and after exposure to the high temperature environment obtained in Examples and Comparative Examples were measured by a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., NF333). Was used to determine the amount of change Δb ^* in the color coordinates b ^* . Table 1 shows the measurement results of the color coordinates b ^* before and after exposure to the high temperature environment and the calculation results of the amount of change Δb ^* .

(Spectroscopic transmittance)
The spectral transmittance of the film with a coating layer at a wavelength of 435 nm before and after exposure to a high temperature environment obtained in Examples and Comparative Examples was measured using a spectrophotometer (UV3600, manufactured by Shimadzu Corporation). Table 1 shows the measurement results of the spectral transmittance before and after exposure to a high temperature environment and the difference between them.

(Water vapor permeability)
The water vapor permeability of the protective film with a coating layer before and after exposure to the high temperature environment obtained in Examples and Comparative Examples was measured by a method according to the infrared sensor method of JIS K 7129. Table 1 shows the measurement results of water vapor permeability before and after exposure to a high temperature environment. A water vapor permeability measuring device (trade name: Permatran, manufactured by MOCON) was used for measuring the water vapor permeability. The temperature of the permeation cell was 40 ° C., the relative humidity of the high humidity chamber was 90% RH, and the relative humidity of the low humidity chamber was 0% RH.

In both Example 1 and Comparative Example 1, it was confirmed that the light emitter protective film had a high spectral transmittance and a low water vapor transmittance. In Example 1, the amount of change Δb ^* before and after exposure to a high temperature environment was small and the decrease in spectral transmittance was small, whereas in Comparative Example 1, the amount of change Δb ^* was large and the spectral transmittance was higher than in Example 1. It dropped significantly. Further, in Example 1, there was no change in water vapor permeability before and after exposure to a high temperature environment, whereas in Comparative Example 1, the water vapor permeability decreased. It is considered that this is because the adhesive layer formed by the epoxy adhesive is oxidized by the high temperature environment exposure, and the gas barrier effect of the adhesive layer is reduced.

1 ... 1st barrier film, 1a ... 1st base material, 1b ... 1st barrier layer, 1c ... 1st gas barrier coating layer, 1v ... 1st inorganic thin film layer, 2 ... 2nd barrier film, 2a ... 2nd group Material, 2b ... Second barrier layer, 2c ... Second gas barrier coating layer, 2v ... Second inorganic thin film layer, 3 ... Support base material, 7 ... Coating layer, 10 ... Luminescent protective film, 11 ... First adhesive layer , 22 ... Second adhesive layer, 50 ... Fluorescent layer, 51 ... Encapsulating resin, 52 ... Fluorescent, 100 ... Wavelength conversion sheet, 200 ... Backlight unit, G ... Light guide plate, L ... Light source, R ... Reflector ..

Claims (6)

A first protective film composed of a light emission member protecting film,
With the fluorescent layer,
With the second protective film,
Are stacked in this order,
The luminous body protective film is
A first barrier film having a first base material and a first barrier layer formed on one surface of the first base material,
A second barrier film having a second base material and a second barrier layer formed on one surface of the second base material,
A first adhesive layer containing a reaction product of an epoxy compound and an amine compound,
With
The first barrier film and the second barrier film are bonded to each other via the first adhesive layer so that the first barrier layer and the second barrier layer face each other.
Before and after exposure for 1000 hours in an environment with an air temperature of 85 ° C., the amount of change Δb ^* of the color coordinates b ^* in the L ^* a ^* b ^* color system was 1.00 or less.
The first protective film is a wavelength conversion sheet in which the first barrier film is arranged so as to face the phosphor layer side. The luminescent material protective film further includes a second adhesive layer and a supporting base material, and further comprises.
The wavelength conversion sheet according to claim 1, wherein the supporting base material is bonded to the other surface of the second base material via the second adhesive layer. The wavelength conversion sheet according to claim 1 or 2, wherein both the first barrier film and the second barrier film have a water vapor permeability of 100 mg / (m ² · day) or less. The illuminant protective film further comprises a coating layer and
The wavelength conversion sheet according to any one of claims 1 to 3, wherein the coating layer is provided so as to be the outermost surface of either one. The first barrier layer includes a first inorganic thin film layer and a first gas barrier coating layer.
The wavelength conversion sheet according to any one of claims 1 to 4, wherein the second barrier layer includes a second inorganic thin film layer and a second gas barrier coating layer. A backlight unit including a light source, a light guide plate, and a wavelength conversion sheet according to any one of claims 1 to 5 .

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