JP7173008B2 - Method for manufacturing wavelength conversion sheet - Google Patents

Description

The present invention relates to a wavelength conversion sheet and its manufacturing method.

A liquid crystal display displays an image by transmitting or blocking light in each area based on the application of voltage. Therefore, external light is required to display an image on the liquid crystal display. As a light source for this purpose, a backlight provided on the back surface of the liquid crystal display is used. A cold cathode tube is conventionally used for the backlight. Recently, LEDs (light-emitting diodes) have also been used in place of cold-cathode tubes for reasons such as long life and good color development.

By replacing the backlight of the liquid crystal display from the general white LED with a three-wavelength white LED using a wavelength conversion material, the color reproducibility of the liquid crystal display can be improved to the NTSC ratio (TV created by the National Television Standards Committee of the United States) standard for evaluating the color gamut), a technique for increasing the color gamut to 100% or more is known.

In the three-wavelength white LED, part of the blue light emitted by the near-ultraviolet or blue LED passes through the phosphor, and the rest is absorbed by the green phosphor and the red phosphor, and converted into green and red light, respectively. is an example. This three-wavelength white LED has a peak wavelength of emission intensity derived from the blue LED in the wavelength range of 440 nm to 470 nm, and is derived from green phosphor and red phosphor in the wavelength ranges of 520 nm to 560 nm and 600 nm to 700 nm, respectively. It has a peak wavelength of emission intensity.

In order to realize the above technology, it is necessary to install a phosphor, which is a wavelength conversion material, in the backlight optical path. However, since phosphor generally reacts with oxygen and water and easily deteriorates, it is necessary to protect it from the outside air. become. As a method for realizing this, it is effective to use a wavelength conversion sheet in which the layer containing the phosphor is protected by a support film made of a transparent resin material and a protective film formed on the surface thereof (for example, Patent Document 1). , Patent Document 2).

JP 2011-13567 A Japanese Patent No. 5979319

However, so-called propeller curl may occur at the four corners of the produced wavelength conversion sheet. FIG. 11 schematically shows a configuration in which propeller curl is generated. A propeller curl is generated in the -Z direction at corners A and C and in the +Z direction at corners B and D as a convex direction. When the wavelength conversion sheet is cut into the size of a display, if such curls are 2 mm or more in height, there is a problem that the sheet does not fit into the mold when assembling members as a display.

The propeller curl can be suppressed by adjusting each tension during lamination and the amount of heat to be applied. In addition, since each film has a different thermal contraction rate, it is difficult to take countermeasures against the amount of heat. Although it is conceivable to take measures to specify the coefficient of thermal expansion of the film, there are restrictions on the films to be used, and there is the problem of incompatibility with cost and various characteristics.

The present invention has been made to solve the above problems, and the object thereof is to sandwich and bond the phosphor layer between the first protective film and the second protective film by a roll-to-roll method. In the production of the wavelength conversion sheet, it does not impair the transportability and barrier properties of the film, does not limit the film to be used, does not lead to an increase in cost, and prevents curling at the corners when cut into display size. An object of the present invention is to provide a wavelength conversion sheet and a method for manufacturing the same, which can suppress this.

The method for manufacturing a wavelength conversion sheet according to the present invention relates to a method for manufacturing a wavelength conversion sheet having a structure in which a phosphor layer is sandwiched between two protective films by a roll-to-roll method. This manufacturing method includes a step of preparing a roll for the first protective film, a step of preparing a roll for the second protective film, and curling of the first protective film and curling of the second protective film. placing a first protective film and a second protective film respectively on opposite sides of the phosphor layer so as to cancel out. Conventionally, when two protective films each include a biaxially stretched film, the wavelength conversion sheet tends to curl depending on the combination of stretching directions of these biaxially stretched films.

A first aspect of the production method according to the present invention includes a step of preparing a protective film raw roll containing a biaxially stretched film, and cutting the protective film raw roll along its longitudinal direction into three The step of producing the above protective film rolls, and the first protective film roll and the second protective film roll from the three or more protective film rolls based on the positions in the protective film original roll and selecting. The biaxially stretched film contained in the original roll for protective film is stretched in different directions depending on the position in the width direction (for example, central portion or peripheral portion), and curling is likely to occur due to this. By selecting the rolls for the first and second protective films based on their position on the original roll for the protective film and using these rolls, both can be arranged so that the curls of the rolls cancel each other out.

In the manufacturing method according to the first aspect, square samples are cut out from the first protective film roll and the second protective film roll, and the first protective film and the second protective film are curled. may further include the step of confirming the When the size of each of the two samples is 1 m×1 m, the difference in curl size between the two samples is preferably in the range of 2 mm to 10 mm.

A second aspect of the production method according to the present invention includes a step of producing three or more biaxially stretched film rolls by cutting an original roll made of a biaxially stretched film along its longitudinal direction; selecting a first roll of biaxially stretched film and a second roll of biaxially stretched film from the three or more rolls of biaxially stretched film based on position on the opposite roll; Further comprising the steps of making a first protective film roll comprising the film and making a second protective film roll comprising a second biaxially stretched film. The original roll of the biaxially stretched film is stretched in different directions depending on the position in the width direction (for example, central portion or peripheral portion), and this tends to cause curling. Selecting the first and second biaxially stretched film rolls based on the position of the biaxially stretched film on the original roll, and using these to position them so that their curls cancel each other out. can be done.

In the first aspect, rolls for the first and second protective films are produced and cut in the longitudinal direction to obtain rolls of the first and second protective films. In the second aspect, first, the original roll of the biaxially stretched film is cut in its longitudinal direction to obtain rolls of the first and second biaxially stretched films. After that, the first and second protective films can be produced by performing various treatments in consideration of the front and back sides of the biaxially stretched films so that the curls caused by the stretching directions can be canceled. can. Therefore, in the manufacturing method according to the second aspect, the coating film for the phosphor layer may be formed on the inner surface of one of the rolls of the first and second protective films, A coating film for a phosphor layer may be formed on the outer surface.

In the production method according to the second aspect, a square sample is cut from each of the first biaxially stretched film roll and the second biaxially stretched film roll, and the first biaxially stretched film and the second biaxially stretched film are obtained. A step of confirming the curling state of the stretched film may be further included. When the size of each of the two samples is 1 m×1 m, the difference in curl size between the two samples is preferably in the range of 2 mm to 10 mm.

The wavelength conversion sheet according to the present invention has a structure in which a phosphor layer is sandwiched between two protective films, and the phosphor layer is arranged so that the curl of the first protective film and the curl of the second protective film cancel each other out. A first protective film and a second protective film are respectively arranged on both sides of the layer.

The first protective film has, for example, a structure in which a resin film, a first bulking layer resin film made of a biaxially stretched film, and a barrier layer are laminated in this order. The second protective film has, for example, a structure in which a resin film, a second bulking layer resin film made of a biaxially stretched film, and a barrier layer are laminated in this order. When the ratio of the thickness of the resin film for the bulking layer made of the biaxially stretched film to the total thickness of the first and second protective films is 50 to 90%, the curl of the first and second protective films is bulky. It tends to be mainly caused by the resin film for the additional layer. Therefore, in this case, it is preferable to arrange the first and second protective films so that the curls of the resin films for the bulking layer contained in the first and second protective films cancel each other out.

According to the present invention, in order to solve the problem, there is no limitation on the materials to be used and their physical properties, and no special manufacturing conditions are used. It is possible to suppress the curling that occurs at the corners when the film is cut out to the display size without causing restrictions on the film to be used or leading to an increase in cost.

FIG. 1(a) is a schematic cross-sectional view showing an example of the configuration of the wavelength conversion sheet, and FIG. 1(b) is a schematic cross-sectional view showing another example of the configuration of the wavelength conversion sheet. FIG. 2 is a schematic diagram showing the manufacturing process of the wavelength conversion sheet by the roll-to-roll method. FIG. 3 is a schematic diagram for explaining a process from a raw fabric roll (sometimes referred to as a "jumbo roll") to arranging individual rolls. FIG. 4 is a schematic diagram for explaining the relationship between the positions of the individual rolls in the jumbo roll and the curl of monitor samples (also referred to as “samples” in some cases) of the protective film cut from the individual rolls. FIG. 5 is a schematic diagram for explaining the relationship between the curling of a monitor sample of a protective film cut out from an individual roll and the propeller curling of a conventional wavelength conversion sheet. FIG. 6 is a schematic diagram for explaining the relationship between the curl of monitor samples of protective films cut out from individual rolls and the wavelength conversion sheet produced by the production method of the present invention. FIG. 7 is a schematic cross-sectional view showing a structural example of a wavelength conversion sheet having a resin film for bulking layer. FIGS. 8(a) and 8(b) are schematic cross-sectional views respectively showing other examples of the wavelength conversion sheet having the resin film for the bulking layer. FIG. 9(a) is a perspective view schematically showing a jumbo roll of a biaxially stretched film, and FIG. 9(b) is a curl of a monitor sample of a biaxially stretched film cut out from an individual roll, and the manufacturing method of the present invention. It is the schematic for demonstrating the relationship of the wavelength conversion sheet produced by. FIG. 10 is a schematic diagram for explaining a method for measuring the difference in thermal contraction rate in the oblique direction of two samples. FIG. 11 is a schematic diagram showing a state in which propeller curl occurs in a conventional wavelength conversion sheet.

Hereinafter, the method for manufacturing the wavelength conversion sheet of the present invention will be described with reference to the drawings. The same constituent elements will be denoted by the same reference numerals unless there is a reason for convenience, and redundant explanations will be omitted. Moreover, the present invention is not limited to the following embodiments without departing from the gist of the present invention.

First, the manufacturing process of the wavelength conversion sheet by the conventional roll-to-roll method and the manner of curl generation will be described.

FIG. 1(a) is a schematic cross-sectional view showing an example of the configuration of a wavelength conversion sheet. The wavelength conversion sheet 100 includes a phosphor layer 50 in which one or more kinds of phosphors 52 using quantum dots or the like are mixed in a sealing resin 51 and sealed, and first and second phosphor layers provided on both sides of the phosphor layer 50, respectively. 2 protective films 10a and 10b. The first and second protective films 10a and 10b have a resin film 1a and barrier layers 1b and 2b. The barrier layers 1b and 2b are inorganic thin film layers 1v and 2v and gas barrier coating layers 1c and 2c, respectively. consists of

In the first and second protective films 10a and 10b, the inorganic thin film layer 1v is formed on one surface of the resin film 1a, and the gas barrier coating layer 1c is laminated on the inorganic thin film layer 1v. An inorganic thin film layer 2v is laminated on the protective coating layer 1c, and a gas barrier coating layer 2c is laminated on the inorganic thin film layer 2v. That is, two barrier layers 1b and 2b are laminated on one surface of the resin film 1a. In addition, in this embodiment, the barrier film 1 is comprised by the resin film 1a and the barrier layer 1b.

Although FIG. 1(a) exemplifies a configuration in which two barrier layers are laminated on one surface of the resin film, the number of barrier layers may be only one (see FIG. 1(b)). , or three or more layers (not shown). Also, the order of lamination of the inorganic thin film layer and the gas barrier coating layer may be reversed from that shown in FIG.

The first protective film 10a can be manufactured by a roll-to-roll method. Specifically, an inorganic thin film layer 1v is formed on one surface of the resin film 1a. Next, a coating agent whose main ingredient is an aqueous solution or a water/alcohol mixed solution 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 laminated by coating on the surface of the inorganic thin film layer 1v and drying by heating. By performing the same operation, the inorganic thin film layer 2v is laminated on the gas barrier coating layer 1c, the gas barrier coating layer 2c is laminated on the inorganic thin film layer 2v, and the roll 22a of the first protective film 10a (first protective film) is formed. rolls for film) are obtained. Similarly, a roll 22b of the second protective film 10b (roll for the second protective film) is produced.

The inorganic thin film layers 1v and 2v can be formed, for example, by depositing aluminum oxide, silicon oxide, silicon oxynitride, magnesium oxide, or a mixture thereof. Among these inorganic materials, it is desirable to use aluminum oxide or silicon oxide from the viewpoint of barrier properties and productivity. The deposition layer is formed by techniques such as vacuum deposition, sputtering, and CVD.

After producing the first and second rolls, the wavelength conversion sheet 100 is manufactured by a roll-to-roll method. The outline of the manufacturing process is shown in FIG. First, the first roll 22a and the second roll 22b are arranged so that the barrier layer 2b side surfaces of the first and second protective films 10a and 10b face each other (S1). On the other hand, a liquid mixture is prepared by mixing the sealing resin 51, the phosphor 52 and, if necessary, a solvent. Next, the mixed solution 50a is applied to the barrier layer 2b side surface of the second protective film 10b of the second roll 22b, and this surface and the barrier layer 2b side surface of the first protective film 10a of the first roll 22a are bonded together. Paste (S2). At this time, if the sealing resin 51 is a photosensitive resin, the photosensitive resin is cured (UV cured) by irradiation with ultraviolet rays. The photosensitive resin may be further thermally cured after UV curing. As the sealing resin 51, a thermosetting resin, a chemically setting resin, or the like may be used other than the photosensitive resin. After that, by cutting the bonded laminate into a predetermined size, the wavelength conversion sheet 100 is obtained (S3). Here, the case of producing the wavelength conversion sheet 100 using the first and second protective films 10a and 10b shown in FIG. The barrier film 1 may be used as a protective film, or first and second protective films 20a and 20b shown in FIG. 3 may be used. 2 and the like indicate the manner in which the wavelength conversion sheet 200 is produced using the first and second protective films 20a and 20b.

Next, the factors that can suppress the curling that tends to occur in the production of the wavelength conversion sheet by the conventional roll-to-roll method according to the present embodiment will be described.

As the first roll 22a and the second roll 22b shown in FIG. 2, a larger jumbo roll 21 (original roll for protective film) is used to produce a protective film, and the jumbo roll 21 is divided into individual rolls. be. That is, as shown in FIG. 3, the jumbo roll 21 is used to produce the protective film 10 (S-1), the jumbo roll 21 is divided into individual rolls (here, 5 lines are divided into 5), and two of them are The rolls (the first roll 22a and the second roll 22b) are selected (S0), the second roll 22b is turned over, and the barrier layer 2b side surfaces of the protective films 10a and 10b face each other (S1). , S1 in FIG. Here, the case of producing five individual rolls from the jumbo roll 21 by taking 5 lines is illustrated, but the number of individual rolls to be produced may be three or more.

Here, while the protective film 10 is being produced (during lamination) by the jumbo roll 21, the tension applied to the film is divided into five parts ((1) to (5)) that are divided into individual rolls in the next process. When considered, it becomes like T1 to T5 in FIG. Each of T1 to T5 is a resultant force of tension in the MD (Machine Direction) direction, which is the conveying direction, and the TD (Transverse Direction) direction perpendicular to the MD direction, as shown by vectors. ) to (5) are equivalent. On the other hand, the tension in the TD direction is balanced at the portion (3) and becomes 0, and at the portions (1) and (5), and (2) and (4), the magnitude is the same in the opposite direction, and (1), The portion (5) is larger than the portions (2) and (4).

Actually, when a monitor sample (specimen) of the protective film is cut out from the above five portions ((1) to (5)) and the curl state is examined, the portions (1) and (5) are illustrated on the right side of FIG. will come to That is, in the portions (1) and (5), curls are generated at two corners (B and D in (1), E and G in (5)) located on diagonal lines in the same direction as T1 and T5, respectively. . Also, although not shown, curls are generated at two corners located on diagonal lines in the same direction as T2 and T4 in portions (2) and (4), respectively, but T2 and T4 are smaller than T1 and T5. Curls get smaller. In (3), diagonal curl does not occur.

Therefore, when individual rolls composed of the protective film of the part (1) are selected as the first roll and the second roll to produce the wavelength conversion sheet, as shown on the left side of FIG. 5, the second protection of the second roll Since the film is placed inside out, the tension T1 directions of the first protective film and the second protective film are perpendicular to each other. Therefore, when the wavelength conversion sheet is produced, as shown in the right side of FIG. 5, curling occurs in all of the four corners (in opposite directions on two orthogonal diagonal lines). Conventionally, in this way, the combination of the first protective film and the second protective film, the right half in the TD direction (for example (1), (2)), the left half (for example (4), (5) made with a jumbo roll )) was not taken into consideration, curling occurred in the wavelength conversion sheet.

In the method for manufacturing the wavelength conversion sheet of the present embodiment, when selecting the individual rolls, the combinations ((1) and (5), (2 ) and (4) and (3)), thereby suppressing curling. That is, as shown in FIG. 6, the directions of the tensions T1 and T5 of the first protective film and the second protective film are the same, and the curl direction is opposite to the Z direction. Curling is suppressed.

As a confirmation method, in the manufacturing method of the wavelength conversion sheet of the present embodiment, a monitor sample having sides parallel to the MD direction and the TD direction is cut out in advance from the protective film, and the curl is measured. Specifically, a 1 m-square monitor sample is cut out, placed on a surface plate, for example, and the heights of warped corners are measured with a ruler. As a result, when the two corners located on the diagonal line are curled, when the surfaces of the first protective film and the second protective film on the barrier layer 2b side are opposed to each other and the phosphor layer is sandwiched and bonded, the diagonal line curls. are made to face each other so that they are aligned with each other. It should be noted that the measurement using the monitor sample does not need to be performed for each sheet of the wavelength conversion sheet produced, and may be carried out at the beginning of the period of production using the same material and under the same conditions.

In the manufacturing method of the wavelength conversion sheet of the present embodiment, when the monitor sample cut out from the first protective film and the second protective film has a difference in curl size of 2 mm to 10 mm, lamination is performed as described above. , it is desirable to produce a wavelength conversion sheet. Here, the difference in curl size means the absolute value of a−b, where a and b are the maximum curls of the first protective film and the second protective film. However, when the curl direction is opposite, the signs of a and b are opposite to each other.

When the difference in curl size is smaller than 2 mm, it does not cause any trouble when the wavelength conversion sheet is produced and the members are assembled as a display. In the case of a curl larger than 10 mm, even with the method of the present invention, it is difficult to suppress the curl generated when cutting out to display size to the extent that it does not interfere with the assembly of members.

The method for producing a wavelength conversion sheet according to the present embodiment is also effective when the wavelength conversion sheet is provided with a bulking layer resin film or a functional layer on the outer layer side of the barrier layer. By bonding the resin film for the bulking layer to the barrier film, it is possible to reduce wrinkles and curls generated in the manufacturing process of the barrier film. The functional layer contains a binder resin and fine particles, and the fine particles are embedded in the binder resin so that part of the fine particles is exposed from the surface of the functional layer. Thereby, the functional layer can have at least one function selected from the group consisting of an interference fringe prevention function, an antireflection function, a light scattering function, an antistatic function and a scratch prevention function. Note that the functional layer is not limited to a single-layer structure, and may be a laminate of layers exhibiting multiple functions. Furthermore, by providing a functional layer on the outermost surface of the resin film for the bulking layer, the separation distance from the barrier layer to the outermost layer is increased, so that small foreign matter (such as vapor deposition powder) can be trapped on the barrier layer. Even if the defect exists, the effect is that when the display is assembled and the presence or absence of the defect on the display is observed, it is difficult to be visually recognized from the outside.

FIG. 7 is a schematic cross-sectional view showing a configuration example of a wavelength conversion sheet 200 having a resin film for bulking layer. Comparing the configuration of FIG. 7 with the configuration of FIG. 1(a), in the wavelength conversion sheet 200 of FIG. A functional layer 15 is formed outside the resin film 16a. Furthermore, the wavelength conversion sheet 200 is formed with the barrier film 1 and the second barrier film 2 , which face each other and are adhered by the second adhesive layer 22 . Also, the barrier film 1 and the bulking layer resin film 16 a are adhered by the first adhesive layer 11 . When the barrier film is deformed due to heating or the like during production, the deformation can be alleviated by laminating the resin film for the bulking layer.

Materials for the resin film 1a in the wavelength conversion sheet 100 in FIG. 1, the resin films 1a and 2a in the wavelength conversion sheet 200 in FIG. 85% or more is desirable. For example, a polyethylene terephthalate film, a polyethylene naphthalate film, or the like can be used as a film having high transparency and excellent heat resistance. Even when a biaxially stretched film is employed as these resin films, curling occurring in the wavelength conversion sheet can be sufficiently suppressed according to the method according to the present embodiment.

As described above, the wavelength conversion sheet 200 of FIG. 7 has more layers than the wavelength conversion sheet 100 of FIG. and For this reason, the behavior of contraction stress and thermal expansion, which cause curling during production of the protective film and wavelength conversion sheet, becomes more complicated. As the number of parameters increases, it becomes easier to control the resin film for bulking layer, which is particularly thick. The method for manufacturing a wavelength conversion sheet according to the present embodiment can suppress the curling of such a wavelength conversion sheet 200 by a simple method.

The protective film contains a bulking layer resin film made of a biaxially stretched film, and the ratio of the thickness of the bulking layer resin film to the total thickness of the protective film is 50 to 90% (especially 60 to 90%). In this case, the curling of the first and second protective films tends to be mainly caused by the resin film for the bulking layer. Even in such a case, by arranging the first and second protective films so that the curls of the resin films for the bulking layer contained in the first and second protective films cancel each other out, wavelength conversion can be achieved. Curling of sheets can be suppressed.

The aspect of the protective film containing the resin film for the bulking layer is not limited to the configuration shown in FIG. good too. The protective films 30a and 30b shown in FIG. 8(a) each have a structure including one barrier film 2, and the resin film 16a for bulking layer and the barrier layer 2b face each other with the adhesive layer 11 interposed therebetween. In the configuration of FIG. 8A, the bulking layer resin film 16a has the effect of preventing damage to the barrier layer 2b.
The protective films 40a and 40b shown in FIG. 8(b) each include one barrier film 1, and the resin film 16a for the bulking layer and the resin film 1a face each other with the adhesive layer 11 interposed therebetween. In the configuration of FIG. 8B, since the barrier layer 1b is arranged on the phosphor layer side, it is possible to further prevent oxygen and water from entering from the edge of the resin film 1a. 8(a) and 8(b) can be compared with the configuration of FIG. 7, the ratio of the thickness of the resin film for the bulking layer to the total thickness of the protective film can be increased, and the effect on curling can be reduced. become dominant. In addition, when the barrier film is deformed due to heating or the like during manufacturing, the effect of alleviating the deformation by the resin film for the bulking layer is increased.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the jumbo roll 21 for the protective film is prepared and cut in its longitudinal direction to produce rolls of the first and second protective films. As shown in 9(a), the original roll 31 of the biaxially stretched film is cut in its longitudinal direction, and two rolls of the same row (row (1) in FIG. 9(b)) (for example, bulking roll for layer resin film 16a) may be selected. Considering the front and back sides of these biaxially stretched films so that the curls can be canceled each other, rolls of the first and second protective films are produced by performing various treatments, and these protective films are used. By producing a wavelength conversion sheet by doing so, as shown in the right side of FIG. 9B, the occurrence of curling can be sufficiently suppressed. In this aspect of the manufacturing method, the coating film for the phosphor layer may be formed on the inner surface of the roll of the first protective film, or the phosphor layer may be formed on the outer surface of the roll of the first protective film. In some cases, a coating film is formed.

Curling of the wavelength conversion sheet may occur even when the protective film is manufactured after dividing the jumbo roll of the resin films 1a and 2a or the resin film 16a for the bulking layer into individual rolls. One of the factors is that the curling of each resin film causes a propeller curl depending on the lamination method, and that the effect of the bulking layer resin film having a large thickness is large. 1(a) and 1(b), the resin film 16a for the bulking layer may be arranged outside the resin film 1a, and the functional layer 15 may be arranged outside thereof. good too.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

<Example 1>
Protective films (20a, 20b) having the form shown in FIG. 2 were produced by a jumbo roll apparatus as follows. First, an acrylic resin coating liquid is applied to one side of a PET film having a thickness of 23 μm as the resin film 1a and dried to form an anchor coat layer. Silicon oxide is formed on the anchor coat layer as an inorganic thin film layer 1v by a vacuum deposition method. It was provided with a thickness of 30 nm. Furthermore, a gas barrier coating layer 1c having a thickness of 300 nm was formed on the inorganic thin film layer 1v. This gas barrier coating layer 1c was formed by applying a coating liquid containing tetraethoxysilane and polyvinyl alcohol by a wet coating method. As a result, a barrier film 1 having a barrier layer 1b composed of an inorganic thin film layer 1v and a gas barrier coating layer 1c provided on one surface of the resin film 1a was obtained. A second barrier film 2 having the same structure as the barrier film 1 was prepared separately.

Two barrier films 1 and 2 obtained as described above were laminated together. A two-component epoxy adhesive consisting of an epoxy resin main agent and an amine curing agent is used for bonding, and the second adhesive layer 22 (under an environment of 30° C. and 70% RH) having a film thickness of 5 μm after curing is used. Oxygen permeability: 5 cm ³ /m ² ·day·atm), and gas barrier coating layers 1c and 2c of two barrier films 1 and 2 were laminated so as to face each other to prepare a film. The oxygen permeability of the second adhesive layer 22 was measured as follows. 20 μm thick OPP film (oxygen permeability 3000 cm ³ /m ² · day · atm (measurement limit) or more in an environment of 30 ° C. 70% RH) so that the film thickness after curing is 5 μm. A liquid-type epoxy adhesive film was formed to prepare an evaluation sample, and a differential pressure gas measuring device (GTR-10X manufactured by GTR Tech) was used in accordance with the method described in JIS K7126A under a 30 ° C. 70% RH environment. The oxygen permeability of the samples was measured at

A functional layer 15 having a thickness of 3 μm was formed on the surface of a PET film having a thickness of 75 μm as the bulking resin film 16a. The functional layer 15 was formed by applying a coating liquid containing acrylic resin and urethane resin particles (average particle size 3 μm) by a wet coating method. A bulking resin film 16a was superimposed on the laminated film (no bulking film) with the surface on which the functional layer 15 was formed facing upward to prepare protective films (20a, 20b) in the form shown in FIG. . The ratio of the thickness of the bulking resin film to the total thickness of the protective film was 55%.

As described above, a protective film in the form shown in FIG. 2 is produced, and in five rows (1) to (5) as shown in FIG. With the second protective film 20b taken at the position (5), a 1 m square monitor sample having sides parallel to the MD and TD directions is cut out, placed on a surface plate, and placed at four corners (corners A, B, C , D, or E, F, G, H) height (curl) was measured with a ruler.

The second roll having the second protective film 20b is turned inside out, and the phosphor layer is sandwiched and bonded between the first protective film 20a and the second protective film 20b by a roll-to-roll device, as shown in FIGS. A wavelength conversion sheet 200 of the form was produced. After that, it was placed on a surface plate, and the height (curl) of the four corners was measured with a ruler. Furthermore, as flatness, the maximum height difference (Peak-Valley) of the curl at the four corners was similarly measured.

<Example 2>
After producing a jumbo roll of the protective film, instead of cutting it in the longitudinal direction, as shown in FIGS. After taking 5 lines (1) to (5) along the longitudinal direction, using the roll at the taking position (1) to make a roll of the first protective film, and the roll at the taking position (1) was used, a second protective film was produced by turning the front and back sides of the first protective film. A wavelength conversion sheet 200 having the configuration shown in FIGS. 2 and 7 was produced in the same manner as in Example 1 except for these matters, and curl and flatness were measured in the same manner as in Example 1. The ratio of the thickness of the bulking resin film to the total thickness of the protective film was 55%.

<Example 3>
A wavelength conversion sheet was produced in the same manner as in Example 1, except that the barrier films of the first protective film and the second protective film had the structure shown in FIG. Curl and flatness were measured. The ratio of the thickness of the bulking resin film to the total thickness of the protective film was 70%.

<Example 4>
A wavelength conversion sheet having the form shown in FIG. 200 was produced, and the curl and flatness were measured in the same manner as in Example 1. The ratio of the thickness of the bulking resin film to the total thickness of the protective film was 80%.
<Comparative example>
A wavelength conversion sheet was produced in the same manner as in Example 1, except that the first protective film 20a and the second protective film 20b were taken from the jumbo roll at the position (1), and the same method as in Example 1. Curl and flatness were measured.

[result]
Table 1 shows the measurement results of the take-up position from the jumbo roll, the curl of the protective film and the wavelength conversion sheet, and the flatness of the above examples and comparative examples. As for the second protective film, the sign of curl is - (minus) because it is turned over when the wavelength conversion sheet is produced.

The "maximum value of the difference in heat shrinkage in the diagonal direction between the two films to be laminated" in Table 1 is the two bulking resin films (before processing) before being used as part of the protective film (before processing). A PET film having a thickness of 75 μm) was measured as follows. First, a square sample with a side of 1 m was cut out from two bulking resin films, and the outer surface (the surface on which the functional layer 15 shown in FIG. 7 was formed) was used as a reference, and FIG. , the diagonal direction from the upper left to the lower right of the first sample (first bulking resin film) (arrow A1 direction in FIG. 10 (a), diagonal line AC (corner A and corner C in Table 1 )), and the diagonal direction from the upper right to the lower left (the direction of the arrow A2 in FIG. 9(a), the diagonal line BD (the direction connecting the corners B and D in Table 1))). Shrinkage was measured. Similarly, the oblique direction from the upper left to the lower right of the second sample (second bulking resin film) (direction of arrow B1 in FIG. 10(b), diagonal line AC (connecting corner H and corner F in Table 1) direction))), and the diagonal direction from the upper right to the lower left (the direction of the arrow B2 in FIG. 10(b), the diagonal line AC (the direction connecting the corners G and E in Table 1))). was measured. The difference between the heat shrinkage rate A1 of the first sample and the heat shrinkage rate B2 of the second sample, and the difference between the heat shrinkage rate A2 of the first sample and the heat shrinkage rate B1 of the second sample Calculated. If the maximum value of these differences is 0.3% or less, the effect of suppressing curling can be expected. The thermal contraction rate of the sample was obtained by heating the sample at 150 ° C. for 30 minutes and then cooling it at room temperature for 30 minutes. was divided by the size before heating.

According to the present invention, in order to solve the problem, there is no limitation on the materials to be used and their physical properties, and no special manufacturing conditions are used. It is possible to suppress the curling that occurs at the corners when the film is cut out to the display size without causing restrictions on the film to be used or leading to an increase in cost.

Reference Signs List 1 Barrier film 1a Resin film 1b Barrier layer 1c Gas barrier coating layer 1v Inorganic thin film layer 2 Second barrier film 2a Second resin film 2b Second barrier Layer 2c... Second gas barrier coating layer 2v... Second inorganic thin film layer 10, 20... Protective film 10a, 20a... First protective film 10b, 20b... Second protective film 11... First adhesive layer 15 Functional layer 16a Bulk-increasing resin film (first and second bulk-increasing resin films) 21 Jumbo roll (raw roll for protective film) 22 Second adhesive layer , 22a . ... phosphor layer, 52... phosphor, 100, 200... wavelength conversion sheet

Claims (9)

A method for manufacturing a wavelength conversion sheet having a structure in which a phosphor layer is sandwiched between two protective films by a roll-to-roll method,
preparing a roll for the first protective film;
preparing a roll for a second protective film;
disposing the first protective film and the second protective film on both sides of the phosphor layer so that the curl of the first protective film and the curl of the second protective film cancel each other out; ,
A method for producing a wavelength conversion sheet comprising: A step of preparing a raw roll for a protective film containing a biaxially stretched film;
A step of producing three or more protective film rolls by cutting the raw roll for protective film along its longitudinal direction;
A step of selecting the roll for the first protective film and the roll for the second protective film from the rolls of the three or more protective films based on the position in the raw roll for the protective film;
The method for producing a wavelength conversion sheet according to claim 1, further comprising Square samples are cut out from the roll for the first protective film and the roll for the second protective film, respectively, and the step of checking the curling aspect of the first protective film and the second protective film is further performed. The manufacturing method of the wavelength conversion sheet of Claim 1 or 2 containing. A step of producing three or more biaxially stretched film rolls by cutting a raw roll made of a biaxially stretched film along its longitudinal direction;
selecting a first biaxially stretched film roll and a second biaxially stretched film roll from the three or more biaxially stretched film rolls based on the position in the original roll;
A step of producing a first protective film roll containing the first biaxially stretched film;
A step of producing a second protective film roll containing the second biaxially stretched film;
The method for producing a wavelength conversion sheet according to claim 1, further comprising A square sample is cut out from each of the roll of the first biaxially stretched film and the roll of the second biaxially stretched film, and the curl state of the first biaxially stretched film and the second biaxially stretched film. The method for manufacturing a wavelength conversion sheet according to claim 4, further comprising the step of confirming. further comprising measuring the diagonal thermal shrinkage of two of said samples;
6. The method for producing a wavelength conversion sheet according to claim 5, wherein the maximum value of the difference in thermal shrinkage between the two samples is 0.3% or less. The method for producing a wavelength conversion sheet according to any one of claims 4 to 6, comprising the step of forming the coating film for the phosphor layer on the inner surface of one of the protective film rolls. The method for producing a wavelength conversion sheet according to any one of claims 4 to 6, comprising the step of forming the coating film for the phosphor layer on the outer surface of one of the protective film rolls. The first protective film has a structure in which a resin film, a first bulking layer resin film made of a biaxially stretched film, and a barrier layer are laminated in this order,
Any one of claims 1 to 8, wherein the second protective film has a structure in which a resin film, a second bulking layer resin film made of a biaxially stretched film, and a barrier layer are laminated in this order. A method for producing a wavelength conversion sheet according to claim 1.

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