Method for manufacturing an image display device

Abstract

To provide a manufacturing method for an image display device including a photocurable resin layer whose attachment surface to be attached to an image display member is flattened, by which the deterioration in image quality can be prevented.SOLUTION: A manufacturing method for an image display device includes the steps of forming a first photocurable resin composition layer 11 including a convex part 11b on an outer edge part by applying a first photocurable resin composition 10 on a protection panel 4, forming a first cured resin layer 13 by irradiating the first photocurable resin composition layer 11 with curing light, forming a second photocurable resin composition layer 15 whose height difference from the convex part 11b is reduced or solved by applying a second photocurable resin composition 10 on the first cured resin layer, forming an image display module 18 by stacking the protection panel 4 and an image display member 2, and forming a photocured resin layer 3 by irradiating the second photocurable resin composition layer 15 with curing light.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present technology relates to a method for manufacturing an image display device in which an image display member such as a liquid crystal display panel and a protective panel such as transparent protective glass disposed on the display surface side thereof are laminated via a photocurable resin layer.

Background Art

[0002] Image display devices such as liquid crystal display panels used in information terminals such as smartphones and car navigation systems have, for the purpose of thinning and improving visibility, an image display member such as a liquid crystal display panel or an organic EL panel and a light-transmissive protective panel such as transparent protective glass. A photocurable resin layer having light transmissivity is provided therebetween.

[0003] As a method for forming the photocurable resin layer, for example, a method is used in which a photocurable resin composition is applied to a protective panel to form a photocurable resin composition layer, an image display member such as a liquid crystal display panel or an organic EL panel is laminated via this photocurable resin composition layer, and then the photocurable resin composition layer is cured (Patent Document 1).

[0004] As a method for applying the photocurable resin composition to the protective panel, for example, there is a method of discharging it over the entire width from a moving slit nozzle onto the surface of the protective panel. In this method, as shown in FIG. 9, the photocurable resin composition 22 is discharged from the tip of the nozzle of the coating head 24 onto the surface 20a of the light-transmissive protective panel 20 facing the image display member 23, whereby, as shown in FIG. 10(A), a substantially rectangular photocurable resin composition layer 25 having a predetermined thickness is formed over the entire surface of the light-transmissive cover member 20.

[0005] Next, as shown in FIG. 10(B), the photocurable resin composition layer 25 formed on the surface 20a of the protective member 20 is irradiated with ultraviolet rays to be temporarily cured, thereby forming a temporarily cured resin layer 26. This is because the photocurable resin composition 22 is brought into a state where it does not flow significantly from the liquid state, so that it does not flow down even when turned upside down, thereby improving the handleability.

[0006] Next, as shown in FIG. 10(C), the protective member 20 is bonded to the image display member 23 from the side of the temporarily cured resin layer 26, and the temporarily cured resin layer 26 is fully cured by ultraviolet irradiation.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Here, due to the action of the surface tension of the photocurable resin composition 22, a convex portion 32 that rises above the main surface portion 31 is formed at the outer edge portion of the protective panel 20 in the photocurable resin composition layer 25. If the convex portion 32 formed in this photocurable resin composition layer 25 is high, when the protective panel 20 and the image display member 23 are bonded together, air may be mixed between them, and bonding unevenness may occur, resulting in image distortion and color unevenness, etc., which may deteriorate the image quality.

[0009] Therefore, when applying the photocurable resin composition 22 to the protective panel 20, it is necessary to apply the photocurable resin composition 22 flatly over the entire surface of the protective panel 20, but it is difficult to precisely control this convex portion 32.

[0010] In particular, in the method of applying the photocurable resin composition 22 to the protective panel 20 by discharging the photocurable resin composition 22 from a discharge head having fine discharge holes, it is required to use a photocurable resin composition 22 having a low viscosity. Generally, the photocurable resin composition 22 adjusted to a low viscosity often does not contain a plasticizer which is a high molecular weight component, so the storage elastic modulus after curing also becomes high, and the influence on the bonding accuracy due to the convex portion 32 tends to be greater.

[0011] Therefore, an object of the present technology is to provide a method for manufacturing an image display device capable of forming a photocurable resin layer having a flattened bonding surface with an image display member and preventing deterioration of image quality. **Means for Solving the Problems**

[0012] In order to solve the above-described problems, a method for manufacturing an image display device according to the present technology is a method for manufacturing an image display device in which an image display member and a protection panel that protects an image display surface of the image display member are laminated via a photocurable resin layer. <Step A> A step of applying a first photocurable resin composition to the protection panel to form a first photocurable resin composition layer having a convex portion at an outer edge portion; <Step B> A step of irradiating the first photocurable resin composition layer with curing light to form a first cured resin layer; <Step C> A step of applying a second photocurable resin composition to the first cured resin layer to form a second photocurable resin composition layer in which the height difference from the convex portion is reduced or eliminated; <Step D> A step of laminating the protection panel and the image display member via the second photocurable resin composition layer to form an image display module; <Step E> A step of irradiating the second photocurable resin composition layer side with curing light to form the photocurable resin layer; It has the above. **Effects of the Invention**

[0013] According to the present technology, in the image display device, since the bonding surface of the photocurable resin layer with the liquid crystal display is flattened, it is bonded uniformly without unevenness over the entire surface, and has good image quality without color unevenness over the entire surface. **Brief Description of the Drawings**

[0014]

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Figure 13

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, a method for manufacturing an image display device to which the present technology is applied will be described in detail with reference to the drawings. Note that the present technology is not limited to the following embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present technology. The drawings are schematic, and the ratios of the respective dimensions may be different from the actual ones. Specific dimensions and the like should be determined with reference to the following description. Needless to say, there are also portions where the relationships and ratios of the dimensions are different between the drawings.

[0016] [Image Display Device] The present technology is a method for manufacturing an image display device 1 formed by bonding an image display member 2 and a protection panel 4 via a photocured resin layer 3 shown in FIG. 1. Prior to the description of the bonding step of the protection panel 4 and the image display member 2, the configuration of the image display device 1 will be described.

[0017] The image display device 1 is a liquid crystal display panel, an organic EL display panel, or other optical devices, and is used in various information terminals and information devices such as smartphones, car navigation systems, and instrument panels. As shown in FIG. 1, for the purpose of thinning and improving visibility, the image display device 1 has a light-transmissive photocured resin layer 3 provided between an image display member 2 such as a liquid crystal display panel and a protection panel 4 that protects the image display member 2.

[0018] [Protection Panel] The protective panel 4 has light transmissivity and covers and protects the display surface of the image display member 2 while ensuring the visibility of the image display member 2 by being laminated with the image display member 2 via the photocuring resin layer 3.

[0019] As the material of the protective panel 4, any material with light transmissivity that allows the image formed on the image display member 2 to be visible is acceptable, such as glass, resin materials like acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate. These materials can be subjected to one-sided or double-sided hard coat treatment, antireflection treatment, etc. Also, when the image display member 2 described later is a touch panel, a part of the touch panel member can also be used as the protective panel 4.

[0020] Further, in order to improve the luminance and contrast of the displayed image, a black frame-shaped light-shielding portion 8 called a so-called black matrix is formed in a region corresponding to the periphery of the display region of the image display member 2 on the protective panel 4. In the image display device 1, the inside of the light-shielding portion 8 surrounding the display region of the image display member 2 becomes a display portion 9 that transmits the display region of the image display member 2 through the protective panel 4.

[0021] The light-shielding portion 8 is formed to have a uniform thickness by applying a paint colored black or the like by a screen printing method or the like and drying and curing it. The thickness of the light-shielding portion 8 is usually 5 to 100 μm.

[0022] The shape of the protective panel 4 to which this technology is applied is not particularly limited and is appropriately set according to the shape of the image display device 1 and the like. For example, the protective panel 4 has a rectangular plate shape. Also, the protective panel 4 may have a curved surface shape, for example, a shape concave-curved in one direction, a convex-curved shape, a paraboloid of revolution, a hyperbolic paraboloid, or other quadratic surface shapes. Furthermore, it may have a flat portion in a part of the curved shape and the quadratic surface shape.

[0023] Note that dimensional characteristics such as the shape and thickness of the protective panel 4, and physical properties such as elasticity can be appropriately determined according to the purpose of use of the image display device 1.

[0024] [Image display member] The image display member 2 can be exemplified by an image display member such as a liquid crystal display panel, an organic EL display panel, a plasma display panel, a touch panel, etc. Here, the touch panel means an image display / input panel that combines a display element such as a liquid crystal display panel and a position input device such as a touch pad. The surface shape on the protective panel 4 side of such an image display member 2 is not particularly limited, but it is preferably flat. Also, a polarizing plate may be disposed on the surface of the image display member 2.

[0025] [Photo-curable resin layer] The photo-curable resin layer 3 interposed between the protective panel 4 and the image display member 2 has light transmissivity and enables the image displayed by the image display member 2 to be visible.

[0026] The photo-curable resin composition 10 constituting the photo-curable resin layer 3 is in a liquid state. As an example, the viscosity measured with a cone plate viscometer at 25°C is 3 to 1000 mPa·s, and it may be 3 to 500 mPa·s.

[0027] Such a photo-curable resin composition 10 can preferably be exemplified by those containing, for example, the following component (A), component (B), component (C), and component (D), or those containing component (B), component (C), and component (D).

[0028] [Component (A)] Component (A) is a film-forming component of the photocurable resin layer 3 having light transmissibility, and an acrylic oligomer, an acrylic polymer, etc. can be used. As the acrylic oligomer, for example, (meth)acrylate oligomers having a skeleton such as polyisoprene, polyurethane, polybutadiene, etc. can be mentioned. In this specification, "(meth)acrylate" is a term encompassing acrylate and methacrylate. Examples of the (meth)acrylate oligomer having a polyisoprene skeleton include esterified products of maleic anhydride adducts of polyisoprene polymers and 2-hydroxyethyl methacrylate (UC102 (polystyrene-equivalent molecular weight 17000), UC203 (polystyrene-equivalent molecular weight 35000), UC-1 (molecular weight approximately 25000), all manufactured by Kuraray Co., Ltd.), etc. Examples of the (meth)acrylic oligomer having a polyurethane skeleton include aliphatic urethane acrylate (EBECRYL230 (molecular weight 5000), manufactured by Daicel Ornex Co., Ltd.; UA-1, manufactured by Lite Chemical Co., Ltd.), etc. Examples of the acrylic polymer include (meth)acrylate polymers having no (meth)acryloyl group. For example, (meth)acrylate polymers having no (meth)acryloyl group with a hydroxyl value of 120 mgKOH / g or more, more preferably a hydroxyl value of 170 mgKOH / g or more can be mentioned. By using such a base component, plasticity can be imparted to the cured product, and good film-forming properties (film property maintenance) and adhesiveness can be ensured.

[0029] (Meta)acrylate polymer's hydroxyl value refers to the mass (mg) of KOH required to neutralize acetic acid generated by hydrolyzing acetyl groups after acetylating hydroxyl groups in 1 g of the polymer. Therefore, the larger the hydroxyl value, the more hydroxyl groups it means. By setting the hydroxyl value of the (meta)acrylate polymer of component (A) to, for example, 120 mgKOH / g or more, it is possible to suppress a decrease in the crosslink density of the cured product of the photocurable resin composition, and particularly to suppress a decrease in the elastic modulus at high temperatures. Also, from the viewpoint of preventing the crosslink density of the cured product of the photocurable resin composition from becoming too high and losing flexibility, the hydroxyl value of the (meta)acrylate polymer is preferably, for example, 400 mgKOH / g or less, more preferably 350 mgKOH / g or less. Further, by using a (meta)acrylate polymer having no (meta)acryloyl group as the (meta)acrylate polymer of component (A), it is possible to prevent it from being excessively incorporated into the main chain of the polymer chain composed of the (meta)acrylate monomers of component (B) and component (C).

[0030] When containing a (meta)acrylate polymer as component (A), if the weight average molecular weight Mn of the (meta)acrylate polymer is too small, the number of molecules without introduced hydroxyl groups increases, and there is a tendency for an increase in risks such as bleed. Therefore, it is preferably 5000 or more, more preferably 100000 or more. Also, if the weight average molecular weight Mn of the (meta)acrylate polymer of component (A) is too large, there is a tendency for poor discharge due to an increase in viscosity. Therefore, it is preferably 500000 or less, more preferably 300000 or less. In this specification, the weight average molecular weight Mw and number average molecular weight Mn of the polymer can be measured by gel permeation chromatography (GPC) (in terms of standard polystyrene molecular weight).

[0031] Also, if the dispersity (Mw / Mn) of the (meta)acrylate polymer of component (A) is too low, the polymer and unreacted monomers tend to be easily separated. Therefore, it is preferably 3 or more. If it is too high, it will result in the incorporation of a relatively low molecular weight polymer component that is not desired. Therefore, it is preferably 10 or less.

[0032] Examples of such (meth)acrylate polymers of component (A) preferably include copolymers of a hydroxyl group-containing (meth)acrylate monomer and a hydroxyl group-free (meth)acrylate monomer. It is preferably liquid at room temperature. Although homopolymers of hydroxyl group-containing (meth)acrylate monomers can also be exemplified, there is a tendency for the polarity of the polymer to become too high, resulting in a high-viscosity liquid or solid at room temperature, and there is concern that the compatibility with other components may decrease.

[0033] The hydroxyl group-containing (meth)acrylate monomer, which is a monomer unit constituting the (meth)acrylate polymer of component (A), is a (meth)acrylate having one or more hydroxyl groups in the molecule. Specifically, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, propylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, cyclohexyl dimethanol mono (meth)acrylate, etc. can be mentioned. Among them, 2-hydroxyethyl (meth)acrylate can be preferably exemplified in terms of polarity control and price.

[0034] Examples of the hydroxyl group-free (meth)acrylate monomer that can constitute the (meth)acrylate polymer of component (A) include monofunctional (meth)acrylic acid alkyl esters having a linear or branched alkyl group with 1 to 18 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, tridecyl (meth)acrylate, etc. can be mentioned.

[0035] Particularly preferred examples of the (meth)acrylate polymer of component (A) include a copolymer of 2-hydroxyethyl acrylate and 2-ethylhexyl acrylate from the viewpoints of easy availability and the realizability of the effects of the invention. Isobornyl acrylate may be further copolymerized.

[0036] The content of component (A) in the photocurable resin composition can be changed according to the amounts of the other components (B), component (C), and component (D). For example, the photocurable resin composition may not contain component (A). When the photocurable resin composition contains component (A), the content of component (A) in the photocurable resin composition can be, for example, 1% by mass or more, and can also be 10% by mass or more. Also, the content of component (A) in the photocurable resin composition can be 55% by mass or less, and can also be 45% by mass or less.

[0037] <Component (B)> The photocurable resin composition preferably contains a hydroxyl group-containing monofunctional (meth)acrylate monomer (component (B)) as a polymerization component. When it contains a hydroxyl group, in the case of containing a (meth)acrylate polymer containing a hydroxyl group as component (A), the affinity with the (meth)acrylate polymer containing a hydroxyl group is high, and also because the reliability in a high-temperature and high-humidity environment is further improved. In this case, there may be a plurality of hydroxyl groups in the monomer molecule, but preferably one hydroxyl group is present in the monomer molecule.

[0038] Specific examples of the hydroxyl group-containing monofunctional (meth)acrylate monomer of component (B) can be exemplified by the same monomers as the hydroxyl group-containing (meth)acrylate monomers that can constitute the (meth)acrylate polymer of component (A). Among them, at least one selected from 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate is preferable.

[0039] If the content of the hydroxyl group-containing monofunctional (meth)acrylate monomer of component (B) in the photocurable resin composition is too small, there is a tendency for insufficient reliability in a high-temperature and high-humidity environment, so it is preferably 1% by mass or more, more preferably 5% by mass or more. If it is too much, the balance of the polarity of the resin before or after curing is disrupted and it tends to become opaque, so it is preferably 30% by mass or less, more preferably 25% by mass or less.

[0040] <Component (C)> The photocurable resin composition preferably contains a hydroxyl group-free monofunctional (meth)acrylate monomer (component (C)) as a polymerization component. The reason for using those without a hydroxyl group is to set the adhesiveness and viscosity of the cured product of the photocurable resin composition composed of component (A) and component (B) in good ranges respectively, and to improve the performance as a transparent adhesive.

[0041] Specific examples of the hydroxyl group-free monofunctional (meth)acrylate monomer of component (C) can include the same monomers as the hydroxyl group-free (meth)acrylate monomers that can constitute the (meth)acrylate polymer of component (A). Among them, at least one selected from isostearyl (meth)acrylate and octyl (meth)acrylate is preferable.

[0042] If the content of the hydroxyl group-free monofunctional (meth)acrylate monomer of component (C) in the photocurable resin composition is too small, it tends to have a high viscosity. Therefore, it is preferably 30% by mass or more, more preferably 65% by mass or more. If it is too much, it tends to become brittle. Therefore, it is preferably 90% by mass or less, more preferably 75% by mass or less.

[0043] <Component (D)> As the photopolymerization initiator (component (D)), a known photoradical polymerization initiator can be used in the photocurable resin composition. In particular, as component (D), it is preferable to contain a hydrogen abstraction type photopolymerization initiator rather than an intramolecular cleavage type photopolymerization initiator such as a benzoin derivative. Thereby, when the (meth)acrylate polymer containing a hydroxyl group is included as component (A), the (meth)acrylate polymer containing a hydroxyl group can be bonded to the side chain of the polymer chain.

[0044] As the hydrogen abstraction type photopolymerization initiator of component (D), a known hydrogen abstraction type photopolymerization initiator can be used. For example, diaryl ketones such as benzophenone and phenylglyoxylates such as methyl benzoyl formate can be mentioned. A preferable example can be methyl benzoyl formate from the viewpoints of no yellowing and high hydrogen abstraction ability.

[0045] If the content of the hydrogen abstraction type photopolymerization initiator of component (D) in the photocurable resin composition is too small, it tends to result in insufficient crosslinking. Therefore, it is preferably 0.1% by mass or more, more preferably 1% by mass or more. If it is too much, it tends to cause deterioration of environmental reliability. Therefore, it is preferably 10% by mass or less, more preferably 5% by mass or less.

[0046] <Component E> The photocurable resin composition may further contain a polyfunctional (meth)acrylate monomer (Component (E)) in order to improve the reaction rate and maintain the high-temperature elastic modulus. Specific examples of the polyfunctional (meth)acrylate monomer include difunctional or higher (meth)acrylates such as 1,6-hexanediol diacrylate (HDDA), 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, and pentaerythritol triacrylate. These can have other functional groups such as hydroxyl groups as long as the effects of the present technology are not impaired. Among them, preferred specific examples of the polyfunctional (meth)acrylate monomer can include at least one selected from trimethylolpropane triacrylate, pentaerythritol triacrylate, and hydroxypivalic acid neopentyl glycol diacrylate.

[0047] If the content of the polyfunctional (meth)acrylate monomer of Component (E) in the photocurable resin composition is too low, the crosslink density tends to be low. Therefore, it is preferably 0.1% or more, more preferably 1% by mass or more. If it is too much, it tends to be brittle. Therefore, it is preferably 5% by mass or less, more preferably 3% by mass or less.

[0048] <Other components> In addition to the above-described components (A) to (D), the photocurable resin composition can be blended with various additives as long as the effects of the present invention are not impaired. For example, as a liquid plastic component for reducing the curing shrinkage rate, a polybutadiene-based plasticizer, a polyisoprene-based plasticizer, a phthalate-based plasticizer, an adipate-based plasticizer, or the like can be blended. Further, as a tackifier for improving tackiness, a terpene resin, a rosin resin, a petroleum resin, or the like can be blended. Further, as a chain transfer agent for adjusting the molecular weight of the cured product, 2-mercaptoethanol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, α-methylstyrene dimer, or the like can be blended. Furthermore, if necessary, an adhesion improver such as a silane coupling agent and general additives such as an antioxidant can be contained.

[0049] [First Manufacturing Process] Next, the first manufacturing process of the image display device 1 will be described. The manufacturing process of the image display device 1 includes the following steps A to E in a manufacturing method of an image display device in which an image display member and a protective panel for protecting the image display surface of the image display member are laminated via a photocurable resin layer. <Step A> A step of applying a first photocurable resin composition to the protective panel to form a first photocurable resin composition layer having a convex portion at an outer edge portion; <Step B> A step of irradiating the first photocurable resin composition layer with curing light to form a first cured resin layer; <Step C> A step of applying a second photocurable resin composition to the first cured resin layer to form a second photocurable resin composition layer in which the height difference from the convex portion is reduced or eliminated; <Step D> A step of laminating the protective panel and the image display member via the second photocurable resin composition layer to form an image display module; <Step E> A step of irradiating the second photocurable resin composition layer side with curing light to form the photocurable resin layer;

[0050] According to the present technology, after forming the first cured resin layer on the protective panel, by further applying the second photocurable resin composition, a second photocurable resin composition layer with a reduced or eliminated height difference from the convex portions formed on the first cured resin layer can be formed. Thereby, a photocurable resin layer with a flattened bonding surface with the image display member can be formed, and deterioration of the image quality of the image display device can be prevented.

[0051] <Step A> First, a protective panel 4 is prepared. As shown in FIG. 2, a photocurable resin composition 10 is applied to the attachment surface 4a to the image display member 2 by a discharge device 12 to form a first photocurable resin composition layer 11. The photocurable resin composition 10 applied in Step A is referred to as a first photocurable resin composition 10a.

[0052] As the discharge device 12 for applying the first photocurable resin composition 10a to the protective panel 4, a known discharge device can be used. However, it preferably has one or a plurality of discharge heads in which a plurality of discharge holes are arranged in a predetermined pattern, and ejects as fine droplets from the discharge holes and adheres to the protective panel 4, that is, a discharge device applying a so-called inkjet method can be preferably used. According to such a discharge device, a predetermined amount of the first photocurable resin composition 10a can be applied in a desired thickness and a desired pattern, and the application speed is also fast (for example, thickness: 30 μm, application speed: 170 mm / second).

[0053] The discharge device 12 shown in FIG. 2 has a discharge head 12a provided with a plurality of discharge holes. This discharge head 12a is installed facing the attachment surface 4a of the protective panel 4, and discharges the first photocurable resin composition while moving relatively to the protective panel 4. Further, the discharge device 12 may adjust the discharge width and the protruding force by providing a plurality of discharge heads 12a. The plurality of discharge heads 12a may be arranged in parallel or in a staggered manner.

[0054] In addition, as shown in FIG. 2, a plurality of protective panels 4 may be arranged, and the first photocurable resin composition layer 11 may be formed on the plurality of protective panels 4 simultaneously in a single coating step.

[0055] Here, the first photocurable resin composition 10a has a low viscosity (e.g., 3 to 1000 mPa·s) that can be discharged by an inkjet-type discharge device 12. Therefore, as shown in FIG. 3, due to the action of surface tension, a convex portion 11b that bulges more than the main surface portion 11a is formed along the outer edge portion in the first photocurable resin composition layer 11. Also, the main surface portion 11a becomes a concave surface portion surrounded by the convex portion 11b.

[0056] In addition, since the first photocurable resin composition 10a often does not contain a plasticizer which is a high molecular weight component, the storage elastic modulus after curing tends to be high. Specifically, it is in the range of 1000 to 10000000 Pa. For this reason, even if the height H of the convex portion 11b is several tens of μm, it may affect the bonding accuracy between the protective panel 4 and the image display member 2 and impair the visibility of the image display device 1. Therefore, in this technology, a step of applying the second photocurable resin composition 10b is provided in step C described later to improve the smoothness of the surface of the photocured resin layer 3. Note that the height H of the convex portion 11b refers to the distance between the main surface portion a of the first photocurable resin composition layer 11 and the apex of the convex portion 11b in a direction perpendicular to the surface of the protective panel 4 (FIG. 3).

[0057] The coating area of the first photocurable resin composition 10a on the protective panel 4 can be appropriately set according to the configuration of the image display device. It may be applied to the entire surface of the protective panel 4, or a non-coating area may be provided in part. When the first photocurable resin composition 10a is applied to the entire surface of the protective panel 4, the convex portion 11b is formed along the outer edge portion of the protective panel 4.

[0058] <Process B> Next, as shown in FIG. 4, the first photocurable resin composition layer 11 is irradiated with curing light such as ultraviolet light to form the first cured resin layer 13. The irradiation conditions for the first photocurable resin composition layer 11 are set so that the curing rate is at least such that the coating shape of the first photocurable resin composition layer 11 can be maintained (for example, 40 to 50% or more). That is, the first cured resin layer 13 is cured with the convex portions 11b formed.

[0059] As the light source for the curing light, known light sources such as LEDs, mercury lamps, metal halide lamps, and xenon lamps can be used.

[0060] Here, the curing rate is a numerical value defined as the ratio (consumption ratio) of the amount of (meth)acryloyl groups present in the photocurable resin composition after light irradiation to the amount of (meth)acryloyl groups present in the photocurable resin composition before light irradiation. The larger the numerical value of this curing rate, the more the curing has progressed. Specifically, the curing rate is calculated by substituting the absorption peak height (X) at 1640 to 1620 cm -1 from the baseline in the FT-IR measurement chart of the photocurable resin composition 6 before light irradiation and the absorption peak height (Y) at 1640 to 1620 cm -1 from the baseline in the FT-IR measurement chart of the photocurable resin composition (first cured resin layer 13) after light irradiation into the following formula. Curing rate (%) = [(X - Y) / X] × 100

[0061] The light irradiation conditions are not particularly limited as long as the curing rate of the first cured resin layer 13 is preferably 40 to 50% or more, such as the type of light source, output, illuminance, and integrated light quantity.

[0062] Also, the curing step of the first photocurable resin composition layer 11 in step B may be a so-called temporary curing that stops at a curing rate that can maintain the coating shape of the first photocurable resin composition layer 11, or a so-called full curing that completely cures it (for example, a curing rate of 90% or more, preferably 95% or more).

[0063] In the above-described step A, if the desired thickness cannot be obtained by a single application by the discharge device 12, the first photocurable resin composition may be applied multiple times. In this case, after applying the first photocurable resin composition multiple times, the first photocurable resin composition layer 11 may be irradiated with curing light such as ultraviolet light to form the first cured resin layer 13. Alternatively, after applying the first photocurable resin composition, the step of irradiating with curing light such as ultraviolet light may be repeated multiple times.

[0064] <Process C> Next, as shown in FIG. 5, the photocurable resin composition 10 is applied to the first cured resin layer 13 to form the second photocurable resin composition layer 15. The photocurable resin composition 10 applied in Process C is designated as the second photocurable resin composition 10b. The second photocurable resin composition layer 15 refers to a layer composed of the first cured resin layer 13 and the second photocurable resin composition 10b.

[0065] As the second photocurable resin composition 10b, the same photocurable resin composition 10 as the above-described first photocurable resin composition can be used, but it is not limited thereto. For example, as the second photocurable resin composition 10b, a photocurable resin composition 10 having a different composition may be used as long as the refractive index is substantially the same as that of the first photocurable resin composition 10a.

[0066] Further, as the second photocurable resin composition 10b, a photocurable resin composition 10 having a higher viscosity than the first photocurable resin composition 10a may be used. Thereby, the second photocurable resin composition 10b applied to the slope of the convex portion 11b of the first cured resin layer 13 is less likely to flow, and the second photocurable resin composition layer 15 can be flattened more until it reaches the end.

[0067] Further, the second photocurable resin composition 10b is applied at least to the main surface portion 11a of the first cured resin layer 13. As a result, the height difference between the convex portion 11b formed on the first cured resin layer 13 and the main surface portion 15a of the second photocurable resin composition layer 15 is reduced or eliminated, and as a result, the surface is made substantially flat. By such planarization, the photocurable resin layer 3 having a substantially flat bonding surface with the image display member can be formed.

[0068] The application of the second photocurable resin composition 10b can be preferably performed using a discharge device applying the above-described inkjet method (see FIG. 2). According to such a discharge device, a predetermined amount of the photocurable resin composition 10b can be applied at a desired thickness and in a desired pattern.

[0069] In this step C, a multilayered second photocurable resin composition layer 15 may be formed by applying the second photocurable resin composition 10b a plurality of times.

[0070] Further, as shown in FIG. 6, the second photocurable resin composition 10b may be applied up to the outer slope of the convex portion 11b of the first photocurable resin layer 13. As a result, the entire surface including the outer slope of the convex portion 11b of the first photocurable resin layer 13 is covered with the second photocurable resin composition 10b, and the photocurable resin layer 3 flattened over the entire application region of the photocurable resin composition 10 can be formed. Further, control such as reducing the application amount on the convex portion 11b to be less than the application amount on the main surface portion 11a and increasing the application amount outside the convex portion 11b is required, but the application amount corresponding to the application position can be easily controlled by the discharge device 12 of the inkjet method described above.

[0071] Note that the application pattern of the second photocurable resin composition 10b includes a pattern 1 in which it is applied only to the central portion of the main surface portion 11a of the first cured resin layer 13, a pattern 2 in which it is applied to the central portion and the end portions of the main surface portion 11a of the first cured resin layer 13, respectively, and a pattern 3 in which it is applied to the entire surface including the main surface portion 11a and the convex portion 11b of the first cured resin layer 13.

[0072] In Pattern 1 and Pattern 2, the coating thickness of the second photocurable resin composition 10b is in the range of 30% or more and 120% or less of the height H of the convex portion 11b, preferably, the upper limit is 100% and the lower limit is 90%. In Pattern 2, no coating is applied on the convex portion 11b. In Pattern 3, the discharge amount is changed between the main surface portion 11a and the convex portion 11b, and the discharge amount is relatively reduced on the convex portion 11b. In Pattern 3, the coating thickness of the second photocurable resin composition 10b on the main surface portion 11a is in the range of 100% or more and 300% or less of the height H of the convex portion 11b, preferably, the upper limit is about 150%.

[0073] The selection of Patterns 1 to 3 and the coating thickness of the second photocurable resin composition 10b in each pattern need to be appropriately set in consideration of the viscosity of the second photocurable resin composition 10b, the discharge speed and movement speed of the discharge head 12a, and other factors, based on the purpose of reducing or eliminating the height difference between the convex portion 11b and the main surface portion 15a of the second photocurable resin composition layer 15.

[0074] In Step C, after the second photocurable resin composition 10b is applied, the second photocurable resin composition layer 15 is immediately irradiated with curing light such as ultraviolet light to be temporarily cured. The irradiation conditions for the second photocurable resin composition layer 15 are performed so that the curing rate is at least such that the shape of the second photocurable resin composition layer 15 can be maintained (for example, 40 to 50% or more).

[0075] <Step D> Next, as shown in FIG. 7, the protective panel 4 and the image display member 2 are laminated via the second photocurable resin composition layer 15 to form an image display module 18. The lamination can be performed by applying pressure in a predetermined temperature environment (for example, 10°C to 80°C) using a known pressure bonding device. In order to prevent air bubbles from entering between the second photocurable resin composition layer 15 and the image display member 2, it is preferable to perform the lamination by a so-called vacuum bonding method.

[0076] Note that after step D, a pressure defoaming process known to the image display module 18 (processing condition example: 0.2 to 0.8 MPa, 25 to 60 °C, 5 to 20 min) may be performed.

[0077] <Step E> Also, after the above step D, a curing light is irradiated from the second photocurable resin composition layer 15 side of the protective panel 4 of the image display module 18 to perform main curing, thereby forming the photocured resin layer 3. When the first cured resin layer 13 formed in the above step B is a temporary cured layer, the first cured resin layer 13 is also main-cured in this step E. Thereby, an image display device 1 in which the protective panel 4 and the image display member 2 are adhered and laminated via the photocured resin layer 3 with a flattened bonding surface is obtained. Since the bonding surface of such an image display device 1 with the image display member 2 of the photocured resin layer 3 is flattened, it is bonded uniformly without unevenness over the entire surface and has good image quality over the entire surface.

[0078] Note that step E may be performed after the above step C and before the above step D. That is, before laminating with the image display member 2, a photocured resin layer 3 composed of the second photocurable resin composition layer 15 that has been main-cured in advance may be formed. Since the bonding surface of the photocured resin layer 3 with the image display member 2 is flattened, it can be bonded uniformly without unevenness over the entire surface and without entrapment of air bubbles between it and the image display member 2. First Embodiment

[0079] Next, an example of forming an image display device using this technology will be described. In this example, cover glass was used as the protective panel 4, and a liquid crystal display (LCD) was used as the image display member 2, and an image display device in which the liquid crystal display and the cover glass were laminated via an ultraviolet curable photocured resin layer was used. A black frame-shaped light-shielding portion was formed on the cover glass at a position corresponding to the periphery of the display area of the LCD.

[0080] Then, the color unevenness when the image display devices according to Example 1, Comparative Example 1, and Comparative Example 2 described below were white-displayed was visually evaluated.

[0081] [Example 1] In Example 1, first, the cover glass was placed on the stage of the coating apparatus, and the photocurable resin composition (the storage elastic modulus after curing is 4.4×10 5 Pa) was applied to form a first photocurable resin composition layer. The coating thickness was 450 μm. Note that the coating thickness refers to the thickness from the surface of the cover glass to the main surface portion of the first photocurable resin composition layer. Convex portions are formed along the outer edge of the first photocurable resin composition layer.

[0082] Also, in Example 1, an inkjet type coating apparatus was used. The coating apparatus used in Example 1 had three ejection heads arranged in tandem, and the dot density in the TD direction of each ejection head for ejecting the photocurable resin composition was 360 dpi. Also, the dot density in the MD direction of each ejection head was 2880 dpi. The stage on which the cover glass was placed was 260 mm in width × 310 mm in length, and the coating range was 60 mm in width × 60 mm in length.

[0083] Next, the first photocurable resin composition layer was irradiated with ultraviolet light for temporary curing to form a first cured resin layer. A metal halide lamp was used as the UV light source. Next, the same photocurable resin composition as the first photocurable resin composition was applied as the second photocurable resin composition to the first cured resin layer, and the second photocurable resin composition layer was formed by irradiating with ultraviolet light for temporary curing. As the coating pattern of the second photocurable resin composition, the above pattern 3 in which the entire surface including the main surface portion and the convex portions of the first cured resin layer was coated was used. In the second photocurable resin composition layer, the height difference between the convex portions formed on the first cured resin layer and the main surface portion of the second photocurable resin composition layer was reduced or eliminated, and the surface was flattened.

[0084] Next, the cover glass and the liquid crystal display were laminated via a second photocurable resin composition layer to form an image display module. Then, the second photocurable resin composition layer was irradiated with curing light from the cover glass side of the image display module for final curing to form a photocured resin layer. As a result, an image display device was obtained in which the cover glass and the liquid crystal display were adhered and laminated via the photocured resin layer with a flattened bonding surface.

[0085] [Comparative Example 1] In Comparative Example 1, first, the cover glass was placed on the stage of the coating apparatus, and the photocurable resin composition was coated to form a photocurable resin composition layer. The same coating apparatus as in Example 1 was used. Further, a convex portion having a height of 60 μm was formed along the outer edge of the photocurable resin composition layer. Next, the photocurable resin composition layer was irradiated with ultraviolet light for temporary curing to form a temporarily cured resin layer. A metal halide lamp was used as the UV light source.

[0086] Next, the cover glass and the liquid crystal display were laminated via the temporarily cured resin layer to form an image display module. Then, the temporarily cured resin layer was irradiated with curing light from the cover glass side of the image display module for final curing to form a photocured resin layer. As a result, an image display device was obtained in which the cover glass and the liquid crystal display were adhered and laminated via the photocured resin layer.

[0087] [Comparative Example 2] In Comparative Example 2, first, the cover glass was placed on the stage of the coating apparatus, and the photocurable resin composition was coated to form a photocurable resin composition layer. The same coating apparatus as in Example 1 was used. Further, a convex portion having a height of 30 μm was formed along the outer edge of the photocurable resin composition layer. Next, the photocurable resin composition layer was irradiated with ultraviolet light for temporary curing to form a temporarily cured resin layer. A metal halide lamp was used as the UV light source.

[0088] Next, a cover glass and a liquid crystal display were laminated via a temporary curing resin layer to form an image display module. Then, the temporary curing resin layer was irradiated with curing light from the cover glass side of the image display module to perform main curing, thereby forming a photocurable resin layer. As a result, an image display device in which the cover glass and the liquid crystal display were adhered and laminated via the photocurable resin layer was obtained.

[0089] [Reference Example] As a reference example, an image display device composed only of a liquid crystal display without a laminated cover glass was prepared. The height (TD waveform) of the photocurable resin layer, the image display screen when the liquid crystal display was white-displayed, and the color unevenness evaluation results of the image display devices according to Example 1, Comparative Example 1, and Comparative Example 2 are shown in FIG. 8.

[0090] As shown in FIG. 8, in the image display device according to Example 1, since the bonding surface of the photocurable resin layer with the liquid crystal display is flattened, it is bonded uniformly without unevenness over the entire surface, and has good image quality without color unevenness over the entire surface.

[0091] On the other hand, in the image display devices according to Comparative Example 1 and Comparative Example 2, due to the influence of the convex portions formed on the photocurable resin layer, the cover glass and the liquid crystal display were not bonded uniformly, and color unevenness occurred. In Comparative Example 2, even though the height of the convex portions was 30 μm, since a low-viscosity photocurable resin composition was used because an inkjet coating apparatus was used, the high post-curing elastic modulus had an influence and color unevenness occurred.

[0092] [Second Manufacturing Process] Next, the second manufacturing process of the image display device 1 will be described. In the protection panel 4 according to the second manufacturing process, a stepped portion 8a is provided between the main surface portion 4b by forming a light-shielding portion 8. In the above step A, the coating thickness of the first photocurable resin composition on the main surface portion 4b of the protection panel 4 is thicker than the coating thickness of the first photocurable resin composition on the light-shielding portion 8, and the coating thickness of the first photocurable resin composition on the light-shielding portion 8 of the protection panel 4 is within the range of ±30% of the height of the stepped portion 8a.

[0093] That is, as shown in FIG. 11, by forming the light-shielding portion 8 on the protective panel 4, a stepped portion 8a having a height H1 is provided between the main surface portion 4b of the protective panel 4. Here, if the coating amounts of the first photocurable resin composition 10a are the same on the main surface portion 4b and on the light-shielding portion 8, the first photocurable resin composition layer 11 has, in addition to the convex portion 11b, a stepped raised portion appearing on the stepped portion 8a. In the subsequent step C of applying the second photocurable resin composition 10b to form the second photocurable resin composition layer 15, it may hinder the flattening of the second photocurable resin composition layer 15.

[0094] Therefore, as shown in FIG. 12, in this manufacturing process 2, in the step A of applying the first photocurable resin composition 10a by the discharge device 12 to form the first photocurable resin composition layer 11, the coating thickness T1 on the main surface portion 4b is made thicker than the coating thickness T2 on the light-shielding portion 8, and the coating thickness T2 of the first photocurable resin composition 10a on the light-shielding portion 8 is within the range of H1 ± 30% of the height H1 of the stepped portion 8a. That is, the coating thickness T2 and the height H1 of the stepped portion 8a have the following relationship. 0.7H1 ≦ T2 ≦ 1.3H1

[0095] Thereby, the first photocurable resin composition layer 11 can be formed while suppressing the influence of the stepped portion 8a on the light-shielding portion 8. Also, in the subsequent step C of applying the second photocurable resin composition 10b to form the second photocurable resin composition layer 15, the second photocurable resin composition layer 15 with the height difference from the convex portion 11b reduced or eliminated can be formed.

[0096] On the other hand, when the coating thickness T2 of the first photocurable resin composition 10a on the light-shielding portion 8 exceeds +30% of the height H1 of the stepped portion 8a, in addition to the convex portion 11b of the first photocurable resin composition layer 11 formed, a portion that bulges stepwise appears on the light-shielding portion 8, and in step C, it may hinder the planarization of the second photocurable resin composition layer 15. Further, when the coating thickness T2 of the first photocurable resin composition 10a on the light-shielding portion 8 is less than 30% of the height H1 of the stepped portion 8a, a concave portion lower than the main surface portion 11a appears at the portion corresponding to the stepped portion 8a of the first photocurable resin composition layer 11, and similarly in step C, it may hinder the planarization of the second photocurable resin composition layer 15.

[0097] In order to partially change the coating thicknesses T1 and T2 between the main surface portion 4b of the protective panel 4 and the light-shielding portion 8, a discharge device applying the so-called inkjet method described above can be preferably used. According to such a discharge device, a predetermined amount of the first photocurable resin composition 10a can be applied with a desired thickness and a desired pattern. Second Embodiment

[0098] Next, a second embodiment of forming the first photocurable resin composition layer 11 on the protective panel 4 using this technology will be described. In this embodiment, a cover glass is prepared as the protective panel 4, a first photocurable resin layer made of an ultraviolet-curable resin is formed, and the height (TD waveform) is measured. The cover glass has a black frame-shaped light-shielding portion formed at a position corresponding to the periphery of the display area of the LCD. Further, an inkjet method discharge device was used for applying the ultraviolet-curable resin.

[0099] The height H1 of the stepped portion of the light-shielding portion was 10 μm. Also, the coating thickness T1 of the ultraviolet-curable resin on the main surface portion of the cover glass was 60 μm. This coating thickness T1 is thicker than the coating thickness T2 of the ultraviolet-curable resin on the light-shielding portion.

[0100] [Example 2] In Example 2, the coating thickness T2 of the ultraviolet-curable resin on the light-shielding portion was 13 μm. This coating thickness T2 is a thickness of +30% of the stepped portion height H1 (10 μm).

[0101] [Example 3] In Example 3, the coating thickness T2 of the ultraviolet curable resin on the light-shielding portion was set to 10 μm. This coating thickness T2 is the same (+0%) thickness as the step portion height H1 (10 μm).

[0102] [Example 4] In Example 4, the coating thickness T2 of the ultraviolet curable resin on the light-shielding portion was set to 7 μm. This coating thickness T2 is a thickness of -30% of the step portion height H1 (10 μm).

[0103] [Comparative Example 3] In Comparative Example 3, the coating thickness T2 of the ultraviolet curable resin on the light-shielding portion was set to 15 μm. This coating thickness T2 is a thickness of +50% of the step portion height H1 (10 μm).

[0104] [Comparative Example 4] In Comparative Example 4, the coating thickness T2 of the ultraviolet curable resin on the light-shielding portion was set to 5 μm. This coating thickness T2 is a thickness of -50% of the step portion height H1 (10 μm).

[0105] The height (TD waveform) of the photocurable resin layer of the image display device according to Examples 2 to 4, Comparative Example 3, and Comparative Example 4 is shown in FIG. 13.

[0106] As shown in FIG. 12, in the cover glass according to Examples 2 to 4, no stepped ridges or recesses appeared other than the convex portions of the first photocurable resin composition layer, and the influence of the step portion was not observed. From this, it can be seen that setting the coating thickness of the first photocurable resin composition on the light-shielding portion within the range of ±30% of the height of the step portion is effective in forming a flattened first photocurable resin composition layer.

[0107] On the other hand, in the cover glass according to Comparative Example 3, stepped ridges appeared in addition to the convex portions of the first photocurable resin composition layer. Further, in the cover glass according to Comparative Example 4, concave portions lower than the main surface portion appeared at the sites corresponding to the stepped portions of the first photocurable resin composition layer. From this, the cover glasses according to Comparative Examples 3 and 4 were unable to form a planarized first photocurable resin composition layer, and in Step C of applying the second photocurable resin composition and forming the second photocurable resin composition layer thereafter, it became possible to impede the planarization of the second photocurable resin composition layer 15.

Explanation of Signs

[0108] 1 Image display device, 2 Image display member, 3 Photocurable resin layer, 4 Protection panel, 8 Light-shielding portion, 9 Display portion, 10 Photocurable resin composition, 11 First photocurable resin composition layer, 11a Main surface portion, 11b Convex portion, 12 Discharge device, 12a Discharge head, 13 First cured resin layer, 15 Second photocurable resin composition layer, 15a Main surface portion, 18 Image display module, 20 Protection panel, 20a Surface, 22 Photocurable resin composition, 23 Image display member, 24 Coating head

Claims

1. In a method for manufacturing an image display device in which an image display member and a protective panel for protecting the image display surface of the image display member are laminated via a photocurable resin layer, <Step A> A step of applying a first photocurable resin composition to the protective panel to form a first photocurable resin composition layer having convex portions at the outer edge; <Step B> A step of irradiating the first photocurable resin composition layer with curing light to form a first cured resin layer; <Step C> A step of applying a second photocurable resin composition to the first cured resin layer to form a second photocurable resin composition layer in which the height difference from the convex portions is reduced or eliminated; <Step D> A step of laminating the protective panel and the image display member via the second photocurable resin composition layer to form an image display module; <Step E> A step of irradiating curing light from the side of the second photocurable resin composition layer to form the photocurable resin layer; comprising: A method for manufacturing an image display device, wherein the second photocurable resin composition is a composition having a higher viscosity than the first photocurable resin composition.

2. The method for manufacturing an image display device according to claim 1, wherein step E is performed after step C and before step D.

3. The method for manufacturing an image display device according to claim 1 or 2, wherein the viscosity of the first photocurable resin composition is 3 to 1000 mPa·s.

4. The method for manufacturing an image display device according to any one of claims 1 to 3, wherein at least the second photocurable resin composition is applied by being discharged from a discharge device in which a plurality of discharge holes are arranged, and is disposed opposite to the surface of the protective panel to which the image display member is attached.

5. The method for manufacturing an image display device according to any one of claims 1 to 4, wherein the first photocurable resin composition is applied to the entire surface of the protective panel.

6. The method for manufacturing an image display device according to any one of claims 1 to 5, wherein the second photocurable resin composition is applied to the main surface portion surrounded by the convex portions of the first cured resin layer.

7. The method for manufacturing an image display device according to claim 6, wherein in step C, the second photocurable resin composition is applied up to the outer inclined surface of the convex portions of the first cured resin layer.

8. The method for manufacturing an image display device according to claim 1, wherein in step B, the first photocurable resin composition layer is pre-cured.

9. The method for manufacturing an image display device according to claim 1, wherein in step B, the first photocurable resin composition layer is fully cured.

10. The method for manufacturing an image display device according to claim 1, wherein in the above step A, the above first photocurable resin composition is applied a plurality of times.

11. The method for manufacturing an image display device according to claim 1, wherein in the above step C, the above second photocurable resin composition is applied a plurality of times.

12. On the above protection panel, a stepped portion is provided between the main surface portion by forming a light-shielding portion at the peripheral portion, In the above step A, the coating thickness of the above first photocurable resin composition on the above main surface portion of the above protection panel is thicker than the coating thickness of the above first photocurable resin composition on the above light-shielding portion, and the coating thickness of the above first photocurable resin composition on the above light-shielding portion of the above protection panel is within the range of ±30% of the height of the above stepped portion. The method for manufacturing an image display device according to any one of claims 1 to 11.

Images