JP2022130683A - Manufacturing method for image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent display from having color unevenness or prevent a gap from being formed on a display surface of an image display device when the image display device is manufactured by stacking an image display member and a light-transmitting cover member that is curved and disposed on a front surface side thereof.

SOLUTION: An image display device in which an image display member and a curved light-transmitting cover member are stacked through a light curable resin layer is manufactured in such a manner that: a light curable resin composition is applied on a concave surface of the curved light-transmitting cover member; the applied light curable resin composition is irradiated with UV rays so as to be temporarily cured; a temporarily cured resin layer with a small dent based on the curing shrinkage of the light curable resin composition is formed in a central part of the concave surface; the light curable resin composition, whose amount corresponds to the small dent of the temporarily cured resin layer, is applied to the temporarily cured resin layer or the image display member; the image display member and the light-transmitting cover member are stacked through the temporarily cured resin layer; the temporarily cured resin layer held between the image display member and the light-transmitting cover member is irradiated with UV rays for permanent curing.

SELECTED DRAWING: Figure 1A

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention provides an image in which an image display member such as a liquid crystal display panel and a light-transmissive cover member such as a curved transparent protective sheet disposed on the surface side of the image display member are laminated via a light-transmissive cured resin layer. The present invention relates to a method of manufacturing a display device.

An image display device used in an in-vehicle information terminal such as a car navigation is formed by applying a photocurable resin composition to a flat light-transmitting cover member and temporarily curing it by irradiating with ultraviolet rays to form a temporary curing resin layer. After that, a flat image display member such as a liquid crystal display panel or an organic EL panel is laminated on the temporary hardened resin layer, and then the temporary hardened resin layer is again irradiated with ultraviolet light to be fully cured to form a photocurable resin layer. (Patent Document 1).

By the way, in order to improve the design and touch feeling of an image display device for an in-vehicle information terminal, it is required to use a light-transmissive cover member curved in one direction. Therefore, an attempt has been made to manufacture such an image display device according to the manufacturing method described in Patent Document 1.

JP 2014-119520 A

In general, curing shrinkage occurs when a photocurable resin composition is photocured by irradiating with ultraviolet rays. Since the coating thickness of the photocurable resin composition in the direction is as thin as about 150 μm and uniform, even if the photocurable resin layer cures and shrinks, voids are unlikely to occur, and the residual stress of the photocurable resin layer with respect to image quality is reduced. The effect was negligible.

On the other hand, when the photocurable resin composition is applied to the concave surface of the light-transmitting cover member curved in one direction, the coating thickness of the photocurable resin composition near the non-curved side is about 0 to 500 μm. However, the coating thickness of the photocurable resin composition in the central portion of the concave surface is much thicker than the coating thickness in the vicinity of the sides, and in some cases it is as thick as several millimeters. For this reason, in the central portion of the concave surface, the curing shrinkage of the photocurable resin composition becomes extremely large, and as a result, a concave portion is formed in the central portion, and a gap is generated on the display surface of the assembled image display device. In addition, even if voids are not generated, the residual stress of the photocurable resin layer causes color unevenness in the display.

An object of the present invention is to solve the above-mentioned problems of the conventional technology, and an image display member and a curved light-transmitting cover member arranged on the surface side thereof are formed of a cured resin of a photocurable resin composition. When an image display device is manufactured by laminating layers through layers, the display surface of the assembled image display device should be free from voids. The purpose is to prevent color unevenness from occurring.

After applying a photocurable resin composition to the recessed surface of the light-transmitting cover member and subjecting it to temporary curing, the present inventor applied a new photocurable resin composition to the recess at the center of the temporary cured resin layer caused by curing shrinkage. By applying the resin composition, laminating the image display member, and performing the main curing treatment, it is possible to prevent the formation of voids on the display surface of the image display device and to reduce the residual stress of the photocurable resin layer. The inventors have found that it is possible to prevent color unevenness in display, and have completed the present invention.

That is, the present invention provides a method for manufacturing an image display device in which an image display member and a curved light-transmitting cover member are laminated via a photocurable resin layer,
The following steps (A)-(D):
<Step (A)>
applying a photocurable resin composition to the recessed surface of the curved light-transmitting cover member;
<Step (B)>
A step of irradiating the applied photocurable resin composition with ultraviolet rays to temporarily cure it, and forming a temporary cured resin layer having minute recesses based on curing shrinkage of the photocurable resin composition on the concave surface;
<Step (C)>
A step of applying a photocurable resin composition in an amount corresponding to the minute recesses of the temporary cured resin layer to the temporary cured resin layer or the image display member;
<Step (D)>
A step of laminating an image display member and a light-transmitting cover member with a temporary cured resin layer interposed therebetween; and <Step (E)>
A step of forming a light-transmitting cured resin layer by irradiating the temporarily-cured resin layer sandwiched between the image display member and the light-transmitting cover member with ultraviolet rays for full curing;
A manufacturing method is provided.

In the method for manufacturing the image display device of the present invention, the photocurable resin composition is applied to the concave surface of the curved light-transmitting cover member, and after temporary curing treatment, the center of the temporarily cured resin layer caused by curing shrinkage A new photocurable resin composition is applied to the recesses of the part, the image display member is laminated, and the main curing treatment is performed. Therefore, it is possible to prevent the generation of voids on the display surface of the image display device, and to reduce the residual stress of the photocurable resin layer, thereby preventing the occurrence of color unevenness in the display.

FIG. 1A is an explanatory diagram of step (A) of the manufacturing method of the present invention. FIG. 1B is an explanatory diagram of step (A) of the manufacturing method of the present invention. FIG. 1C is an explanatory diagram of a light transmissive cover member. FIG. 1D is an explanatory diagram of a light transmissive cover member. FIG. 1E is an explanatory diagram of a light transmissive cover member. FIG. 1F is an illustration of a light transmissive cover member. FIG. 1G is an explanatory diagram of a light transmissive cover member. FIG. 2A is an explanatory diagram of step (B) of the manufacturing method of the present invention. FIG. 2B is an explanatory diagram of step (B) of the manufacturing method of the present invention. FIG. 3A is an explanatory diagram of step (C) of the manufacturing method of the present invention. FIG. 3B is an explanatory diagram of step (C) of the manufacturing method of the present invention. FIG. 4 is an explanatory diagram of step (D) of the manufacturing method of the present invention. FIG. 5 is an explanatory diagram of step (E) of the manufacturing method of the present invention.

The present invention is a method for manufacturing an image display device in which an image display member and a curved light-transmitting cover member are laminated via a photocurable resin layer, and includes the following steps (A) to (E). manufacturing method. Each step will be described in detail below with reference to the drawings.

<Step (A): Coating step>
First, as shown in FIG. 1A, a curved light-transmitting cover member 1 is prepared, and as shown in FIG. apply. The amount of the photocurable resin composition 2 applied varies depending on the size and shape of the image display element, the application, etc., but is usually 45 (w) × 80 (l) × 3 (t) mm (radius of curvature (r) : 300 mm), when an image display member of 40 (w) × 80 (l) mm is attached in contact with two non-curved sides of the light-transmitting cover member, Preferably, the thickness is 23.44 cc and the thickness of the deepest part of the curve is 670 μm. It is possible. This gap is preferably 50 μm or more and 800 μm or less, although it depends on the design of the image display device. In addition, such a coating amount may be satisfied by a single coating operation, but may be satisfied by a plurality of coating operations.

(Light transmissive cover member 1)
As a specific shape of the curved light-transmitting cover member 1, there is a shape curved in one direction (for example, a shape on the inferior arc side obtained by cutting a cylindrical pipe along a plane parallel to its central axis (hereinafter referred to as a horizontal gutter). (referred to as shape)) (Fig. 1A), a shape curved in the X and Y directions (Fig. 1C), a shape curved in the 360° direction (e.g. minor arc side) (Fig. 1D). A flat portion 1b may be formed in the central portion of these shapes (eg, FIG. 1E).

When the light-transmissive cover member 1 has a lateral gutter shape (FIG. 1A), an inner dam member 3 (FIG. 1F) defining a coating region of the photocurable resin composition is provided inside both ends 1x and 1y of the cover member 1 (FIG. 1A). It is preferable to provide an outer dam member 4 (FIG. 1G) that defines the application area of the photocurable resin composition outside both ends 1x and 1y. The inner dam material 3 and the outer dam material 4 can block the applied photocurable resin composition without being compatible with it, and can be easily removed after the temporary curing of the photocurable resin composition. can be formed from any known material. For example, as the inner dam material 3, a known thermoplastic elastomer tape having a slightly adhesive layer or the like is attached to the inside of the end portion of the light-transmissive cover member 1 in the shape of a bank. Examples of the outer dam material 4 include a silicone sheet and a fluororesin sheet.

In addition, when the light-transmitting cover member 1 is in the form of FIG. 1C or FIG. 1D, the dam material may be omitted. 1A and 1B, the surface of the light-transmitting cover member 1 corresponding to the inner dam member 3 is subjected to surface treatment (for example, Depending on the characteristics of the photocurable resin composition, surface roughening treatment, hydrophilic treatment, water repellent treatment, etc.) may be applied.

The material of the light-transmitting cover member 1 may be any light-transmitting material such that an image formed on the image display member can be visually recognized. materials. These materials can be subjected to single-sided or double-sided hard coating treatment, antireflection treatment, and the like. Dimensional characteristics such as the curved shape and thickness of the light-transmitting cover member 1, and physical properties such as elasticity can be appropriately determined according to the purpose of use.

(Photocurable resin composition 2)
The property of the photocurable resin composition 2 applied to the recessed surface 1a of the light-transmitting cover member 1 is preferably liquid. If a liquid material is used, the concave surface 1a of the light-transmitting cover member 1 can be filled with the photocurable resin composition 2 so that the composition surface becomes flat. Here, the term “liquid” indicates a viscosity of 0.01 to 100 Pa·s (25° C.) with a cone-plate viscometer.

Such a photocurable resin composition 2 preferably includes a base component (component (a)), an acrylic monomer component (component (b)), and a photopolymerization initiator (component (c)). can do. If necessary, it may further contain a plasticizer component (component (d)). The final cure shrinkage of the photocurable resin composition 2 is 3% or more. It may be 5% or more.

Here, the "final cure shrinkage rate" means the cure shrinkage rate generated between the uncured state of the photocurable resin composition 2 and the completely cured state. Here, "completely cured" means a state in which the curing rate is at least 90% as described later. Hereinafter, the final cure shrinkage rate is referred to as the total cure shrinkage rate. In addition, the curing shrinkage rate that occurs between the uncured state and the temporarily cured state of the curable resin composition is referred to as the temporary curing shrinkage rate. Furthermore, in the main curing step, the curing shrinkage rate that occurs between the temporary curing state and the completely cured state is referred to as the main curing shrinkage rate.

The total curing shrinkage rate of the photocurable resin composition is obtained by measuring the specific gravity of the uncured (in other words, before curing) composition and the solid completely cured product after complete curing with an electronic hydrometer (SD manufactured by Alpha Mirage Co., Ltd.). -120L), and can be calculated by the following formula from the difference in specific gravity between the two. In addition, the temporary curing shrinkage rate of the temporary curing resin of the photocurable resin composition is an electronic hydrometer (alpha SD-120L manufactured by Mirage Co., Ltd.), and can be calculated from the difference in specific gravity between the two by the following formula. The final curing shrinkage rate can be calculated by subtracting the temporary curing shrinkage rate from the total curing shrinkage rate.

The component (a), the base component, is a film-forming component for the light-transmitting cured resin layer and contains at least one of an elastomer and an acrylic oligomer. Both may be used together as the component (a).

Examples of elastomers include acrylic copolymers, polybutenes, and polyolefins, which are preferably copolymers of acrylic acid esters. The weight average molecular weight of this acrylic acid ester copolymer is preferably 5,000 to 500,000, and the repeating number n of polybutene is preferably 10 to 10,000.

On the other hand, acrylic oligomers preferably include (meth)acrylate oligomers having a skeleton of polyisoprene, polyurethane, polybutadiene, or the like. In this specification, the term "(meth)acrylate" includes acrylate and methacrylate.

A preferred specific example of the (meth)acrylate oligomer having a polyisoprene skeleton is an esterified product of a maleic anhydride adduct of a polyisoprene polymer and 2-hydroxyethyl methacrylate (UC102 (polystyrene equivalent molecular weight: 17000), Kuraray Co., Ltd.). UC203 (polystyrene equivalent molecular weight: 35,000), Kuraray Co., Ltd.; UC-1 (molecular weight: about 25,000, Kuraray Co., Ltd.).

Further, preferred specific examples of (meth)acrylate oligomers having a polyurethane skeleton include aliphatic urethane acrylates (EBECRYL230 (molecular weight: 5000), Daicel-Ornex Co.; UA-1, Light Chemical Industry Co., Ltd.), and the like. can be mentioned.

As the (meth)acrylate-based oligomer having a polybutadiene skeleton, known ones can be employed.

The acrylic monomer component (b) is used as a reactive diluent in order to impart sufficient reactivity and coatability to the photocurable resin composition in the manufacturing process of image display devices. Examples of such acrylic monomers include 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, stearyl acrylate, benzyl acrylate, tetrahydrofurifyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl methacrylate, isobornyl acrylate, di Cyclopentanyl acrylate, lauryl methacrylate and the like can be mentioned.

As the photopolymerization initiator of component (c), known photoradical polymerization initiators can be used, for example, 1-hydroxy-cyclohexylphenyl ketone (Irgacure 184, BASF Japan Ltd.), 2-hydroxy -1-{4-[4-(2-hydroxy-2-methyl-propyronyl)benzyl]phenyl}-2-methyl-1-propan-1-one (Irgacure127, BASF Japan Ltd.), benzophenone, acetophenone, etc. can be mentioned.

If the amount of such a photopolymerization initiator is too small with respect to a total of 100 parts by mass of the acrylic oligomer and acrylic monomer component (b) in the base component (a), curing will be insufficient during ultraviolet irradiation, and if it is too large, cleavage will occur. The amount is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, since outgassing increases and foaming problems tend to occur.

Moreover, the photocurable resin composition 2 can contain a chain transfer agent for adjusting the molecular weight. Examples include 2-mercaptoethanol, laurylmercaptan, glycidylmercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, α-methylstyrene dimer and the like.

Moreover, the photocurable resin composition 2 may further contain general additives such as an adhesion improver such as a silane coupling agent and an antioxidant, if necessary.

The photocurable resin composition 2 has a curing shrinkage rate of less than 3% in the main curing step after the temporary curing step described later, so basically it is not essential to contain a plasticizer component. However, in order to impart cushioning properties to the cured resin layer and reduce the cure shrinkage of the photocurable resin composition, a plasticizer component (component (d)) is contained within a range that does not impair the effects of the present invention. can do. Therefore, the total content of the component (a) base component and the component (b) acrylic monomer component in the photocurable resin composition is preferably 25 to 85% by mass. The content of the agent component is in the range of 0 to 65% by mass.

The plasticizer component of component (d) does not react with the base component of component (a) and the acrylic monomer component of component (b) when irradiated with ultraviolet rays. Such plasticizer components include a solid tackifier (1) and a liquid oil component (2).

Examples of the solid tackifier (1) include terpene resins such as terpene resins, terpene phenolic resins and hydrogenated terpene resins, rosin resins such as natural rosin, polymerized rosin, rosin ester, hydrogenated rosin, and terpene hydrogenated resins. can be mentioned. In addition, a non-reactive oligomer obtained by polymerizing the above-mentioned acrylic monomer component into a low-molecular-weight polymer in advance can also be used. Copolymers of methacrylic acid and the like can be mentioned.

The liquid oil component (2) may contain polybutadiene-based oil, polyisoprene-based oil, or the like.

<Step (B): Temporary curing step>
Next, as shown in FIG. 2A, the applied photocurable resin composition 2 is irradiated with ultraviolet light UV to be temporarily cured, and is applied to the concave surface 1a of the light-transmitting cover member 1 (usually, in the central portion thereof). ) Temporarily cured resin layer 5 having minute recesses 5a based on curing shrinkage of the photocurable resin composition 2 (for example, although the recesses are X-shaped in FIG. 2B, recesses of other shapes such as lines may be used) form. "Very small" in the minute dents 5a means the amount of volume change due to temporary hardening shrinkage. Here, the reason why the photocurable resin composition 2 is temporarily cured is to make the photocurable resin composition 2 in a non-fluid state so as to improve the handleability. The level of such temporary curing is such that the curing rate (gel fraction) of the temporary cured resin layer 5 is preferably 10 to 90%, more preferably 40 to 90%. Further, the curing rate (gel fraction) is the ratio of the amount of (meth)acryloyl groups present after UV irradiation to the amount of (meth)acryloyl groups present in the photocurable resin composition 2 before UV irradiation (consumption Amount ratio), and the larger the value, the more the curing progresses.

The curing rate (gel fraction) is the absorption peak height (X) from 1640 to 1620 cm ^-1 from the baseline in the FT-IR measurement chart of the resin composition layer before UV irradiation, and the resin after UV irradiation. It can be calculated by substituting the absorption peak height (Y) at 1640 to 1620 cm ⁻¹ from the baseline in the FT-IR measurement chart of the composition layer into the following formula.

With respect to ultraviolet irradiation, as long as temporary curing can be performed so that the curing rate (gel fraction) is preferably 10 to 80%, the type of light source, output, cumulative light amount, etc. are not particularly limited, and known ultraviolet irradiation. can adopt the photoradical polymerization process conditions of (meth)acrylates according to.

In addition, regarding the ultraviolet irradiation conditions, it is possible to select conditions that do not cause dripping or deformation of the temporarily cured resin layer 5 during the bonding operation in the step (C) described later, within the above-described curing rate range. preferable. Expressing the conditions under which such dripping and deformation do not occur in terms of viscosity is 20 Pa·S or more (cone and plate rheometer, 25° C., cone and plate C35/2, rotation speed 10 rpm).

The level of hardening in the temporary hardening is such that the hardening shrinkage rate between the temporary hardened resin layer 5 and the hardened resin layer is less than 3% in the main hardening step described later. That is, in the case of the photocurable resin composition 2 having a total curing shrinkage rate of 5%, the temporary curing shrinkage is at least 2% at the time of temporary curing.

When the inner dam material 3 and the outer dam material 4 are provided in the process (A), the inner dam material 3 or the outer dam material 4 may be removed after the process (B) and before the process (C). preferable. This is because the photocurable resin composition 2 has already been temporarily cured, and resin flow does not occur.

<Step (C): Refilling of photocurable resin composition>
Next, an amount of the photocurable resin composition 2 corresponding to the minute recesses 5a of the temporary cured resin layer 5 is applied to the temporary cured resin layer 5 (FIG. 3A) or the normally flat image display member 6 (FIG. 3B). . Here, the amount corresponding to the minute recesses 5a is obtained by measuring the recess shape of the minute recesses 5a using a minute surface shape measuring device (eg, 3D measuring laser microscope (OLS4000 series), Shimadzu Corporation). can be calculated. Alternatively, it can be determined by the temporary curing shrinkage rate and the amount (volume) of the photocurable resin composition.

In addition, the photocurable resin composition 2 used in this step is preferably the same as the photocurable resin composition 2 used in step (A) from the viewpoint of the refractive index, but the refractive index are substantially the same, photocurable resin compositions having different compositions may be used. Further, the application of the photocurable resin composition is preferably carried out by a conventionally known technique so that the fine recesses 5a are filled with the photocurable resin composition 2 . For example, when the photocurable resin composition 2 is applied to the temporary curing resin layer 5 or the image display member 6, a line shape (FIGS. 3A and 3B), an X shape, or a dot in the center so as to fill the minute concave portion 5a It should be applied in a shape.

In addition, even if the application position of the photocurable resin composition 2 is displaced from the minute concave portion 5a, the applied photocurable resin composition 2 is vacuum-bonded while maintaining fluidity without being temporarily cured. As a result, the photocurable resin composition 2 can be appropriately moved to the minute recesses 5a.

Examples of the image display member 6 include a liquid crystal display panel, an organic EL display panel, a plasma display panel, a touch panel, and the like. Here, the touch panel means an image display/input panel in which a display element such as a liquid crystal display panel and a position input device such as a touch pad are combined.

As a preferred embodiment of the step (B) and the present step (C) described above, in the step (B), at least the central portion of the recessed surface of the light-transmitting cover member is formed with minute recesses, and the step (C) ), the photocurable resin composition corresponding to 70% or more of the volume of the microrecesses is applied to the corresponding temporary cured resin layer or image display member.

<Step (D): Lamination step>
Subsequently, the image display member 6 and the light transmissive cover member 1 are laminated via the temporary hardening resin layer 5 (FIG. 4). Lamination can be performed by applying pressure at 10° C. to 80° C. using a known crimping device. It is preferable to perform lamination by a so-called vacuum lamination method in order to prevent entrapment.

After the step (D) and before the step (E), the laminate is subjected to a known pressure defoaming treatment (treatment condition example: 0.2 to 0.8 MPa, 25 to 60 ° C., 5 to 20 min). preferably.

<Step (E): main curing step)>
Subsequently, the temporarily cured resin layer 5 sandwiched between the image display member 6 and the light-transmitting cover member 1 is irradiated with UV rays to be fully cured, thereby forming the light-transmitting cured resin layer 7 ( Figure 5). As a result, the desired image display device is obtained. The main curing in this step is to sufficiently cure the temporarily cured resin layer 5 to adhere and laminate the image display member 6 and the light-transmissive cover member 1 . Such a main curing level is such that the curing rate (gel fraction) of the light-transmitting cured resin layer 7 is preferably 90% or more, more preferably 95% or more.

The light transmittance level of the light transmittance cured resin layer 7 may be such that an image formed on the image display member 6 can be visually recognized.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. In the following examples, the total curing shrinkage rate, temporary curing shrinkage rate, and main curing shrinkage rate of the photocurable resin composition are the specific gravity of the photocurable resin composition, the temporary cured product, and the completely cured product. The specific gravity was measured using an electronic hydrometer (SD-120L, manufactured by Alpha Mirage Co., Ltd.), and the measurement results were applied to the following formula for calculation.

Comparative example 1
(Step (A): coating step))
First, a transparent resin plate (polyethylene terephthalate plate) having a size of 45 (w) × 80 (l) × 3 (t) mm was prepared, and the radius of curvature (r) in the width direction was adjusted to 300 mm by a known method. A resin cover (FIG. 1A) was obtained as a curved lateral gutter-shaped light-transmitting cover member.

Separately, (meth)acrylic oligomer having a polybutadiene skeleton (TE-2000, Nippon Soda Co., Ltd.) 50 parts by weight, hydroxyethyl methacrylate 20 parts by weight, photopolymerization initiator 10 parts by weight (Irgacure 184, BASF Japan Co., Ltd.) and 7 parts by mass of SpeedCure TPO (manufactured by DKSH Japan Co., Ltd.) were uniformly mixed to prepare a photocurable resin composition. This photocurable resin composition exhibited a total cure shrinkage of 5.6% at a cure rate of 0% to 90%.

Next, both ends of the lateral gutter-shaped resin cover were sandwiched between two silicone rubber sheets as outer dam materials (FIG. 1G). A photocurable resin composition film was formed by discharging the prepared photocurable resin composition into the concave portion of the resin cover using a resin dispenser so that the thickness at the central portion was 880 μm.

(Step (B): Temporary curing step)
Next, the photocurable resin composition film was irradiated with an ultraviolet irradiation device (LC-8, Hamamatsu Photonics Co., Ltd.) with an intensity of 200 mW/cm ² so that the integrated amount of light was 1200 mJ/cm ² . was irradiated with UV rays for 6 seconds to temporarily cure the photocurable resin composition film to form a temporarily cured resin layer, and then the outer dam material was removed. During temporary curing, it was observed that a minute concave portion was formed in the central portion of the temporarily cured resin layer (Fig. 2B). The temporary curing shrinkage rate was 3.8%.

The curing rate of the temporarily cured resin layer was about 70% when the absorption peak height at 1640 to 1620 cm ⁻¹ from the baseline in the FT-IR measurement chart was used as an indicator.

(Step (D): Lamination step)
Next, the light-transmitting cover member obtained in the step (B) was placed on the surface of the flat liquid crystal display element having a size of 40 (W) × 80 (L) mm on which the polarizing plates were laminated. It was placed so as to face the polarizing plate, and was bonded from the resin cover side by a vacuum bonding machine (degree of vacuum: 50 Pa, bonding pressure: 0.07 MPa, bonding time: 3 seconds, room temperature) (Fig. 4).

(Step (E): main curing step)
Next, this liquid crystal display element is irradiated with ultraviolet rays (200 mW/cm ² ) at 3000 mJ/cm ² from the resin cover side using an ultraviolet irradiation device (ECS-03601EG, Eye Graphics Co., Ltd.). The temporarily cured resin layer was completely cured to form a light-transmitting cured resin layer. The curing rate of the light-transmitting cured resin layer was 98%. As a result, a liquid crystal display device was obtained in which a curved resin cover as a light-transmitting cover member was laminated on the liquid crystal display element via a light-transmitting cured resin layer. Moreover, the main cure shrinkage rate was 1.8%.

When the presence or absence of voids in the obtained liquid crystal display device was visually observed from the side of the resin cover, it was found that a bubble-like void was generated in the substantially central portion of the interface between the light-transmitting cured resin layer and the liquid crystal display element.

Comparative example 2
As the photocurable resin composition, (meth)acrylate oligomer having a polyisoprene skeleton (UC203, Kuraray Co., Ltd.) 40 parts by mass, dicyclopentenyloxyethyl methacrylate (FA512M, Hitachi Chemical Co., Ltd.) 20 parts by mass , hydroxypropyl methacrylate (HPMA, Nippon Kasei Co., Ltd.) 3 parts by mass, tetrahydrofurfuryl acrylate (Light Ester THF, Kyoeisha Chemical Co., Ltd.) 15 parts by mass, lauryl acrylate (Light Ester L, Kyoeisha Chemical Co., Ltd.), Polybutadiene polymer (Polyoil 110, Evonik Japan Co., Ltd.) 20 parts by mass, hydrogenated terpene resin (P85, Yasuhara Chemical Co., Ltd.) 45 parts by mass, photopolymerization initiator (Irgacure 184, BASF Japan Co., Ltd.) 4 parts by mass The same as in Comparative Example 1 except that a photocurable resin composition prepared by uniformly blending (curing rate between 0% and 90%, showing a total cure shrinkage of 3.4%) is used. A liquid crystal display device was obtained by the operation.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, no voids were observed at the interface between the liquid crystal display device (polarizing plate) and the light-transmitting cured resin layer. When the display operation was performed, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.1%, and the final curing shrinkage rate was 0.3%.

Comparative example 3
As a photocurable resin composition, 6 parts by mass of polyisoprene methacrylate (UC102, Kuraray Co., Ltd.) as a photoradical polymerizable poly(meth)acrylate, 15 parts by mass of dicyclopentenyloxyethyl methacrylate and lauryl methacrylate as reactive diluents 5 parts by mass, 20 parts by mass of polybutadiene (Polyvest 110, Evonik Japan Co., Ltd.) as a plasticizer, 1 part by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Co., Ltd.), and a hydrogenated terpene resin (Clearon A photocurable resin composition prepared by uniformly blending 53 parts by mass of M105 and Yasuhara Chemical Co., Ltd. (hardening rate between 0% and 90%, showing a total curing shrinkage rate of 2.6%). A liquid crystal display device was obtained in the same manner as in Comparative Example 1, except that it was used.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, no voids were observed at the interface between the liquid crystal display device (polarizing plate) and the light-transmitting cured resin layer. When the display operation was performed, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 2.2%, and the final curing shrinkage rate was 0.4%.

Example 1
Between the step (B) and the step (D) in Comparative Example 1, as the step (C), an amount of the photocurable resin composition corresponding to the minute recesses of the temporary cured resin layer (step (A ) The same composition as used in Comparative Example 1) was applied in a line to the central part of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. By the same operation as in Comparative Example 1. A liquid crystal display was obtained. The amount of the photocurable resin composition corresponding to the minute dents in the temporary cured resin layer was measured by the amount (volume) of the photocurable resin composition used and the temporary curing shrinkage rate, and the amount was 0.91 cc. rice field.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.8%, and the final curing shrinkage rate was 1.8%.

Example 2
Between the step (B) and the step (D) in Comparative Example 1, as the step (C), an amount of the photocurable resin composition corresponding to the minute recesses of the temporary cured resin layer (step (A ) The same composition as used in Comparative Example 1) was applied in a line to the central part of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. By the same operation as in Comparative Example 1. A liquid crystal display was obtained. The amount of the photocurable resin composition corresponding to the minute dents in the temporary cured resin layer was 0.91 cc when measured from the amount (volume) of the photocurable resin composition used and the temporary curing shrinkage rate. , 0.64 cc of the photocurable resin composition corresponding to about 70% thereof was applied.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, almost no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.8%, and the final curing shrinkage rate was 1.8%.

Example 3
Between the step (B) and the step (D) in Comparative Example 2, as the step (C), an amount of the photocurable resin composition corresponding to the minute recesses of the temporary cured resin layer (the step (A ) The same composition as used in Comparative Example 1) was applied in a line to the central part of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. By the same operation as in Comparative Example 1. A liquid crystal display was obtained. The amount of the photocurable resin composition corresponding to the minute dents in the temporary cured resin layer is measured by the amount (volume) of the photocurable resin composition used and the temporary curing shrinkage rate, and the amount is about 0.74 cc. there were.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.1%, and the final curing shrinkage rate was 0.3%.

Example 4
Between the step (B) and the step (D) in Comparative Example 3, as the step (C), an amount of the photocurable resin composition corresponding to the minute recesses of the temporary cured resin layer (step (A ) The same composition as used in Comparative Example 1), using the resin dispenser used in Comparative Example 1, except that it was applied to the liquid crystal display element side of the location corresponding to the line in the central part of the temporary cured resin layer. A liquid crystal display device was obtained by the same operation as in Comparative Example 1. The amount of the photocurable resin composition corresponding to the minute dents in the temporary cured resin layer is measured by the amount (volume) of the photocurable resin composition used and the temporary curing shrinkage rate, and the amount is 0.53 cc. there were.

When the presence or absence of voids in the resulting liquid crystal display device was visually observed from the resin cover side, no voids were observed at the interface between the resin cover and the light-transmitting cured resin layer. Further, when the display operation was performed, no color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 2.2%, and the final curing shrinkage rate was 0.4%.

In the method for manufacturing an image display device of the present invention, a photocurable resin composition is applied to the recessed surface of a curved transparent cover member, and after temporary curing treatment, the central portion of the temporary cured resin layer caused by curing shrinkage. A new photocurable resin composition is applied to the recesses, an image display member is laminated, and main curing treatment is performed. Therefore, it is possible to prevent the generation of voids on the display surface of the image display device, and to reduce the residual stress of the photocurable resin layer, thereby preventing the occurrence of color unevenness in the display. Therefore, the production method of the present invention is useful for industrial production of an in-vehicle information terminal equipped with a touch panel.

REFERENCE SIGNS LIST 1 light-transmitting cover member 1a recessed surface of light-transmitting cover member 1x, 1y both ends 2 photocurable resin composition 3 inner dam member 4 outer dam member 5 temporary cured resin layer 5a minute recess 6 image display member 7 light transmission curable resin layer D dispenser

Claims (11)

In a method for manufacturing an image display device in which an image display member and a curved light-transmitting cover member are laminated via a photocurable resin layer,
The following steps (A)-(D):
<Step (A)>
applying a photocurable resin composition to the recessed surface of the curved light-transmitting cover member;
<Step (B)>
A step of irradiating the applied photocurable resin composition with ultraviolet rays to temporarily cure it, and forming a temporary cured resin layer having minute recesses based on curing shrinkage of the photocurable resin composition on the concave surface;
<Step (C)>
A step of applying a photocurable resin composition in an amount corresponding to the minute recesses of the temporary cured resin layer to the temporary cured resin layer or the image display member;
<Step (D)>
A step of laminating an image display member and a light-transmitting cover member with a temporary cured resin layer interposed therebetween; and <Step (E)>
A step of forming a light-transmitting cured resin layer by irradiating the temporarily-cured resin layer sandwiched between the image display member and the light-transmitting cover member with ultraviolet rays for full curing;
A manufacturing method having 2. The manufacturing method according to claim 1, wherein the light-transmitting cover member used in step (A) has a lateral gutter shape. In the step (B), micro-recesses are generated at least in the central portion of the recessed surface of the light-transmitting cover member, and in the step (C), the photocurable resin composition corresponding to 70% or more of the volume of the micro-recesses is applied. 3. The manufacturing method according to claim 1 or 2, wherein the temporary curing resin layer or the image display member is coated. 4. The manufacture according to claim 2 or 3, wherein an inner dam member or an outer dam member is provided on the inside or outside of both lateral gutter-shaped end portions of the light-transmitting cover member, respectively, to define the application area of the photocurable resin composition. Method. 5. The manufacturing method according to claim 4, wherein the inner dam material or the outer dam material is removed between step (B) and step (C). The manufacturing method according to any one of claims 1 to 5, wherein the lamination in step (D) is performed by a vacuum bonding method. The production method according to any one of claims 1 to 6, wherein a pressure defoaming treatment is performed between step (D) and step (E). The manufacturing method according to any one of claims 1 to 7, wherein the image display member is a liquid crystal display panel, an organic EL display panel, a plasma display panel or a touch panel. The production according to any one of claims 1 to 8, wherein in the step (B), the photocurable resin composition is temporarily cured by irradiating ultraviolet rays so that the curing rate of the temporary cured resin layer is 10 to 90%. Method. 10. The production method according to any one of claims 1 to 9, wherein in the step (E), the temporarily cured resin layer is irradiated with ultraviolet rays to be fully cured so that the curing rate of the light-transmitting cured resin layer is 90% or more. . The photocurable resin composition is a liquid resin composition containing at least one of an elastomer and an acrylic oligomer, an acrylic monomer, and a photopolymerization initiator,
The elastomer is at least one selected from the group consisting of acrylic copolymers, polybutenes and polyolefins,
The production method according to any one of claims 1 to 10, wherein the acrylic oligomer is at least one selected from the group consisting of polyurethane-based (meth)acrylates, polybutadiene-based (meth)acrylates and polyisoprene-based (meth)acrylates. .

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