JP7376819B2 - Method for manufacturing an image display device - Google Patents

Description

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

Image display devices used in in-vehicle information terminals such as car navigation systems are made by applying a photocurable resin composition to a flat light-transmitting cover member and temporarily curing it by irradiating it with ultraviolet rays to form a temporary cured 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 temporarily cured resin layer, and then the temporary cured resin layer is irradiated with ultraviolet rays again to be fully cured to form a photocured resin layer. (Patent Document 1).

Incidentally, in order to improve the design and touch feel of an image display device for an in-vehicle information terminal, it has become necessary to use a light-transmitting cover member having a shape curved in one direction. For this reason, attempts have been made to manufacture such an image display device according to the manufacturing method described in Patent Document 1.

JP2014-119520A

Generally, curing shrinkage occurs when a photocurable resin composition is photocured by ultraviolet irradiation, but in the case of the manufacturing method of Patent Document 1 in which a flat image display member is laminated on a flat light-transmitting cover member, Since the coating thickness of the photocurable resin composition in the direction is as thin and uniform as about 150 μm, voids are unlikely to occur even when the photocurable resin layer cures and shrinks, and the residual stress of the photocurable resin layer affects image quality. The impact was negligible.

On the other hand, when a photocurable resin composition is applied to the concave surface of a light-transmitting cover member curved in one direction, the coating thickness of the photocurable resin composition near the non-curved side is approximately 0 to 500 μm. However, the coating thickness of the photocurable resin composition at the center of the recessed surface is much thicker than the coating thickness near the sides, and in some cases can be as thick as several millimeters. For this reason, the curing shrinkage of the photocurable resin composition becomes extremely large in the center of the recessed surface, and as a result, a recess is formed in the center, creating a void in the display surface of the assembled image display device. Furthermore, even if no voids are formed, there is a problem in that color unevenness occurs in the display due to residual stress in the photocurable resin layer.

An object of the present invention is to solve the above-mentioned problems of the conventional technology, and to combine an image display member and a curved light-transmitting cover member disposed on the surface side with a cured resin of a photocurable resin composition. When manufacturing an image display device by laminating layers, it is necessary to prevent gaps from forming on the display surface of the assembled image display device. The purpose is to prevent color unevenness from occurring.

The present inventor applied a photocurable resin composition to the concave surface of a light-transmitting cover member, subjected it to temporary curing treatment, and then applied a new photocurable resin composition to the concavity in 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 also to reduce the residual stress in the photocurable resin layer. The inventors have discovered that it is possible to prevent display color unevenness, 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 with a photocurable resin layer interposed therebetween.
The following steps (A) to (D):
<Process (A)>
a step of applying a photocurable resin composition to the concave surface of the curved light-transmitting cover member;
<Process (B)>
A step of temporarily curing the applied photocurable resin composition by irradiating it with ultraviolet rays to form a temporary cured resin layer having minute dents on the concave surface due to curing shrinkage of the photocurable resin composition;
<Step (C)>
A step of applying a photocurable resin composition in an amount corresponding to the minute dents in the temporarily cured resin layer to the temporarily cured resin layer or the image display member;
<Step (D)>
Step of laminating the image display member and the light-transmitting cover member via a temporarily cured resin layer; and <Step (E)>
forming a light-transmissive cured resin layer by irradiating ultraviolet rays to the temporarily cured resin layer sandwiched between the image display member and the light-transparent cover member to fully cure it;
A manufacturing method is provided.

In the method for manufacturing an image display device of the present invention, a photocurable resin composition is applied to the concave surface of a curved light-transmissive cover member, and after a temporary curing treatment, the center of the temporary cured resin layer generated by curing shrinkage is applied. A photocurable resin composition is newly applied to the recess of the part, an image display member is laminated, and a main curing process is performed. Therefore, it is possible to prevent the formation of voids on the display surface of the image display device, and also to reduce the residual stress in 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 explanatory diagram 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 with a photocurable resin layer interposed therebetween, and includes the following steps (A) to (E). This is the manufacturing method. Each step will be described in detail below with reference to the drawings.

<Step (A): Coating step>
First, a curved light-transmitting cover member 1 is prepared as shown in FIG. 1A, and a photocurable resin composition 2 is applied to the concave surface 1a of the light-transmitting cover member 1 using a dispenser D or the like as shown in FIG. 1B. Apply. The coating amount of this photocurable resin composition 2 varies depending on the size, shape, application, etc. of the image display element, but is usually 45 (w) x 80 (l) x 3 (t) mm (radius of curvature (r) : 300 mm) to a curved light-transmissive cover member, when an image display member of 40 (w) x 80 (l) mm is laminated in contact with two uncurved sides of the light-transmissive cover member, Preferably, it is 23.44 cc, and the thickness at the deepest curved part is 670 μm, but more preferably, it is 23.76 cc, and a gap of about 100 μm is provided between the two uncurved sides of the light-transmitting cover member and the image display member. It is possible. Although this gap depends on the design of the image display device, it is preferably 50 μm or more and 800 μm or less. Moreover, such a coating amount may be satisfied by one coating operation, or may be satisfied by a plurality of coating operations.

(Light transparent cover member 1)
A specific shape of the curved light-transmitting cover member 1 is a shape curved in one direction (for example, a shape on the side of a lower arc obtained by cutting a cylindrical pipe along a plane parallel to its central axis (hereinafter referred to as a horizontal gutter). shape)) (Fig. 1A), a shape curved in the X and Y directions (Fig. 1C), a shape curved in a 360° direction (for example, obtained by cutting a sphere with a plane that does not include its center point) (Figure 1D). A flat portion 1b may be formed in the center of these shapes (for example, FIG. 1E).

When the light-transmissive cover member 1 has a horizontal gutter shape (FIG. 1A), an inner dam member 3 (FIG. 1F) that demarcates the application area of the photocurable resin composition or its It is preferable to provide an outer dam member 4 (FIG. 1G) that defines a coating area for the photocurable resin composition on the outside of 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 temporary curing of the photocurable resin composition. It can be formed from any known material. For example, the inner dam material 3 may be one in which a known thermoplastic elastomer tape with a slightly adhesive layer is pasted to the inner side of the end portion of the light-transmitting cover member 1 in the shape of a bank. Examples of the outer dam material 4 include silicone sheets, fluororesin sheets, and the like.

Note that when the light-transmissive cover member 1 has the embodiment shown in FIG. 1C or FIG. 1D, the dam material may not be provided. In addition, even in the case of the embodiments shown in FIGS. 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, hydrophilization treatment, water repellency treatment, etc.) may be performed.

The material for the light-transmissive cover member 1 may be any light-transmissive material that allows the image formed on the image display member to be viewed, and may include resins such as glass, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate. Examples include materials. These materials can be subjected to hard coating treatment, antireflection treatment, etc. on one or both sides. The curved shape, dimensional characteristics such as thickness, and site-specific physical properties such as elasticity of the light-transmitting cover member 1 can be determined as appropriate depending on the purpose of use.

(Photocurable resin composition 2)
The photocurable resin composition 2 applied to the concave surface 1a of the light-transmissive cover member 1 is preferably in a liquid state. When a liquid composition is used, the photocurable resin composition 2 can be filled into the concave surface 1a of the light-transmitting cover member 1 so that the composition surface becomes flat. Here, the liquid state indicates a viscosity of 0.01 to 100 Pa·s (25° C.) as measured by a cone plate viscometer.

Preferred examples of such photocurable resin composition 2 include those containing a base component (component (a)), an acrylic monomer component (component (b)), and a photopolymerization initiator (component (c)). can do. If necessary, a plasticizer component (component (d)) can be further included. Note that the final curing shrinkage rate 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 that occurs between the uncured state and the completely cured state of the photocurable resin composition 2. Here, completely cured means a state in which the cure rate is at least 90% as described later. Hereinafter, the final curing shrinkage rate will be referred to as the total curing shrinkage rate. Moreover, 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 a photocurable resin composition is determined by measuring the specific gravity of the uncured (in other words, before curing) composition and the solid completely cured product after complete curing using an electronic hydrometer (SD manufactured by Alpha Mirage Co., Ltd.). -120L), and can be calculated from the difference in specific gravity between the two using the following formula. In addition, the temporary curing shrinkage rate of the temporary curing resin of the photocurable resin composition is determined by measuring the specific gravity of the uncured (in other words, before curing) composition and the solid temporary cured product after temporary curing using an electronic hydrometer (alpha SD-120L (manufactured by Mirage Co., Ltd.), and can be calculated from the difference in specific gravity between the two using the following formula. The main curing shrinkage rate can be calculated by subtracting the temporary curing shrinkage rate from the total curing shrinkage rate.

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

Preferred examples of the elastomer include acrylic copolymers made of copolymers of acrylic acid esters, polybutenes, polyolefins, and the like. The weight average molecular weight of this acrylic 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, examples of acrylic oligomers include (meth)acrylate oligomers having skeletons such as polyisoprene, polyurethane, and polybutadiene. In addition, in this specification, the term "(meth)acrylate" includes acrylate and methacrylate.

Preferred specific examples of the (meth)acrylate oligomer having a polyisoprene skeleton include an esterified product of a maleic anhydride adduct of a polyisoprene polymer and 2-hydroxyethyl methacrylate (UC102 (polystyrene equivalent molecular weight 17,000), manufactured by Kuraray Co., Ltd. ; UC203 (polystyrene equivalent molecular weight: 35,000); Kuraray Co., Ltd.; UC-1 (molecular weight: approximately 25,000); Kuraray Co., Ltd.).

Preferred specific examples of (meth)acrylate oligomers having a polyurethane skeleton include aliphatic urethane acrylates (EBECRYL230 (molecular weight 5000), Daicel Allnex Corporation; UA-1, Light Chemical Industries, Ltd.). can be mentioned.

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

The acrylic monomer component (b) is used as a reactive diluent in the manufacturing process of image display devices in order to impart sufficient reactivity, coating properties, etc. to the photocurable resin composition. Examples of such acrylic monomers include 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, stearyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl methacrylate, isobornyl acrylate, and dicyclopentenyl acrylate. Examples include cyclopentanyl acrylate and lauryl methacrylate.

As the photopolymerization initiator of component (c), known radical photopolymerization initiators can be used, such as 1-hydroxy-cyclohexylphenyl ketone (Irgacure 184, BASF Japan Ltd.), 2-hydroxy -1-{4-[4-(2-hydroxy-2-methyl-propylonyl)benzyl]phenyl}-2-methyl-1-propan-1-one (Irgacure 127, BASF Japan Ltd.), benzophenone, acetophenone, etc. can be mentioned.

If such a photopolymerization initiator is used in too little amount, curing will be insufficient when irradiated with ultraviolet rays, and if it is too much, curing may occur due to cleavage, based on the total of 100 parts by mass of the acrylic oligomer and acrylic monomer component (b) in base component (a). Since outgas tends to increase and foaming problems occur, the amount is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass.

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

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

Since the curing shrinkage rate of the photocurable resin composition 2 in the main curing process after the temporary curing process described below is suppressed to less than 3%, it is basically not essential to contain a plasticizer component. However, in order to provide buffering properties to the cured resin layer and reduce the curing shrinkage rate of the photocurable resin composition, it contains a plasticizer component (component (d)) within a range that does not impair the effects of the present invention. can do. Therefore, the total content of the base component of component (a) and the acrylic monomer component of component (b) 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 (d) does not react with the base component (i) and the acrylic monomer component (b) when irradiated with ultraviolet light. Such a plasticizer component contains a solid tackifier (1) and a liquid oil component (2).

Solid tackifiers (1) include terpene resins such as terpene resins, terpene phenol resins, and hydrogenated terpene resins; rosin resins such as natural rosins, polymerized rosins, rosin esters, and hydrogenated rosins; and terpene hydrogenated resins. can be mentioned. In addition, non-reactive oligomers obtained by converting the aforementioned acrylic monomer components into low-molecular-weight polymers can also be used. Specifically, copolymers of butyl acrylate, 2-hexyl acrylate, and acrylic acid, and copolymers of cyclohexyl acrylate and cyclohexyl acrylate can also be used. Examples include copolymers of methacrylic acid.

The liquid oil component (2) may contain polyptadiene oil, polyisoprene 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 rays to temporarily cure it, and is applied to the concave surface 1a of the light-transmitting cover member 1 (usually in the center thereof). ) Temporarily cured resin layer 5 having minute depressions 5a based on curing shrinkage of the photocurable resin composition 2 (for example, in FIG. 2B, it is an X-shaped depression, but it may be a depression in other shapes such as a line shape) to form. "Minute" in the minute recess 5a means the amount of volume variation due to temporary curing shrinkage. Here, the reason why the photocurable resin composition 2 is temporarily cured is to make the photocurable resin composition 2 non-flowing and improve its handling properties. The level of such temporary curing is such that the curing rate (gel fraction) of the temporarily cured resin layer 5 is preferably 10 to 90%, more preferably 40 to 90%. In addition, the curing rate (gel fraction) is the ratio (consumption) 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. The larger the value, the more the curing progresses.

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

Regarding ultraviolet irradiation, there are no particular restrictions on the type, output, cumulative light amount, etc. of the light source, as long as it can be temporarily cured so that the curing rate (gel fraction) is preferably 10 to 80%. (meth)acrylate photoradical polymerization process conditions can be adopted.

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

The level of curing in the temporary curing is such that the curing shrinkage rate that occurs between the temporarily cured resin layer 5 and the cured resin layer in the main curing step described below is less than 3%. That is, in the case of the photocurable resin composition 2 having a total curing shrinkage rate of 5%, the temporary curing shrinkage should be at least 2% during temporary curing.

In addition, when the inner dam material 3 or the outer dam material 4 is provided in step (A), the inner dam material 3 or the outer dam material 4 may be removed after step (B) and before step (C). preferable. This is because the photocurable resin composition 2 has already been temporarily cured and no resin flow occurs.

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

In addition, from the viewpoint of refractive index, it is preferable to use the same photocurable resin composition 2 as the photocurable resin composition 2 used in step (A), but the refractive index Photocurable resin compositions having different compositions may be used as long as they are substantially the same. Further, the application of the photocurable resin composition is preferably performed by a conventionally known method so that the photocurable resin composition 2 is filled into the minute depressions 5a. For example, when applying the photocurable resin composition 2 to the temporarily cured resin layer 5 or the image display member 6, it may be applied in a line shape (FIGS. 3A and 3B), an X shape, or a dot in the center so as to fill the minute recesses 5a. It can be applied in a shape.

In addition, even if the application position of the photocurable resin composition 2 deviates from the minute recess 5a, the applied photocurable resin composition 2 can be vacuum pasted while maintaining its fluidity without being temporarily cured. Therefore, 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 refers to 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.

In addition, as a preferable embodiment of the step (B) and this step (C) described above, in the step (B), a minute dent is generated at least in the center of the recessed surface of the light-transmitting cover member, and at the same time, in the step (C) ), an embodiment may be mentioned in which a photocurable resin composition corresponding to 70% or more of the volume of the minute depressions is applied to the corresponding temporarily cured resin layer or image display member.

<Step (D): Lamination step>
Subsequently, the image display member 6 and the light-transmitting cover member 1 are laminated with the temporarily cured resin layer 5 interposed therebetween (FIG. 4). Lamination can be performed by applying pressure at 10°C to 80°C using a known pressure bonding device, but if air bubbles are formed between the temporarily cured resin layer 5 and the image display member 6 or the light-transmissive cover member 1. In order to prevent this from occurring, it is preferable to perform the lamination by a so-called vacuum lamination method.

In addition, after step (D) and before step (E), the laminate is subjected to a known pressure degassing treatment (example of treatment conditions: 0.2 to 0.8 MPa, 25 to 60°C, 5 to 20 min). It is preferable to do so.

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

Note that the light transmittance level of the light transmitting cured resin layer 7 may be such that the image formed on the image display member 6 is visible.

Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, in the following examples, the total curing shrinkage rate, temporary curing shrinkage rate, and main curing shrinkage rate of the photocurable resin composition are based on the specific gravity of the photocurable resin composition, the temporarily cured product, and the fully cured product, respectively. The specific gravity was measured using an electronic hydrometer (SD-120L manufactured by Alpha Mirage Co., Ltd.) and calculated by applying the measurement results to the following formula.

Comparative example 1
(Process (A): Coating process))
First, prepare a transparent resin plate (polyethylene terephthalate plate) with a size of 45 (w) x 80 (l) x 3 (t) mm, and use a known method to make the radius of curvature (r) 300 mm in the width direction. A resin cover (FIG. 1A) was obtained as a curved gutter-shaped light-transmissive cover member.

Separately, 50 parts by mass of a (meth)acrylic oligomer with a polybutadiene skeleton (TE-2000, Nippon Soda Co., Ltd.), 20 parts by mass of hydroxyethyl methacrylate, and 10 parts by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Ltd.) A photocurable resin composition was prepared by uniformly mixing 3 parts by mass of SpeedCure TPO (manufactured by DKSH Japan Co., Ltd.) and 7 parts by mass of SpeedCure TPO (manufactured by DKSH Japan Co., Ltd.). This photocurable resin composition exhibited a total curing shrinkage rate of 5.6% in a curing rate of 0% to 90%.

Next, both ends of the gutter-shaped resin cover were sandwiched between two silicone rubber sheets as outer dam members (FIG. 1G). The prepared photocurable resin composition was discharged into the recessed portion of the resin cover using a resin dispenser so that the thickness at the central portion was 880 μm to form a photocurable resin composition film.

(Step (B): temporary curing step)
Next, this photocurable resin composition film was irradiated with ultraviolet light using an ultraviolet irradiation device (LC-8, Hamamatsu Photonics Co., Ltd.) with an intensity of 200 mW/cm ² so that the cumulative amount of light was 1200 mJ/cm ² . The photocurable resin composition film was temporarily cured by irradiating it with ultraviolet rays for 6 seconds to form a temporarily cured resin layer, and the outer dam material was further removed. During the temporary curing, it was observed that a minute recess was formed in the center of the temporarily cured resin layer (FIG. 2B). Note that the temporary curing shrinkage rate was 3.8%.

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

(Process (D): Lamination process)
Next, the light-transmitting cover member obtained in step (B) was placed on the surface of a flat liquid crystal display element with a size of 40 (W) x 80 (L) mm on which the polarizing plate was laminated, with the temporarily cured resin layer side facing up. It was placed so that the polarizing plate side was facing, and it was pasted from the resin cover side using a vacuum lamination machine (degree of vacuum 50 Pa, lamination pressure 0.07 MPa, lamination 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-transmissive cured resin layer. The curing rate of the light-transmissive cured resin layer was 98%. As a result, a liquid crystal display device was obtained in which a curved resin cover as a light-transmissive cover member was laminated on a liquid crystal display element via a light-transparent cured resin layer. Further, the main curing shrinkage rate was 1.8%.

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, bubble-like voids were found approximately at the center of the interface between the light-transmissive cured resin layer and the liquid crystal display element.

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

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 was operated, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 3.1%, and the main 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 photoradically polymerizable poly(meth)acrylate, 15 parts by mass of dicyclopentenyloxyethyl methacrylate and lauryl methacrylate as a reactive diluent. 5 parts by mass, 20 parts by mass of polybutadiene (Polyvest 110, Evonik Japan Ltd.) as a plasticizer, 1 part by mass of a photopolymerization initiator (Irgacure 184, BASF Japan Ltd.), and hydrogenated terpene resin (Clearon) as a tackifier. A photocurable resin composition prepared by uniformly blending 53 parts by mass of M105 (produced by Yasuhara Chemical Co., Ltd.) (showing a total curing shrinkage rate of 2.6% from a curing rate of 0% to 90%). A liquid crystal display device was obtained in the same manner as in Comparative Example 1 except for using the same method.

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 was operated, color unevenness was observed in the display at the center of the resin cover. The temporary curing shrinkage rate was 2.2%, and the main curing shrinkage rate was 0.4%.

Example 1
Between step (B) and step (D) in Comparative Example 1, as step (C), a photocurable resin composition (step (A ) was applied in a line in the center of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. A liquid crystal display device was obtained. The amount of the photocurable resin composition corresponding to the minute dents in the temporarily cured resin layer was measured by the amount (volume) of the photocurable resin composition used and the temporary cure shrinkage rate, and the amount was 0.91 cc. Ta.

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 main curing shrinkage rate was 1.8%.

Example 2
Between step (B) and step (D) in Comparative Example 1, as step (C), a photocurable resin composition (step (A ) was applied in a line in the center of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. A liquid crystal display device was obtained. In addition, the amount corresponding to the minute dents in the temporarily cured resin layer of the photocurable resin composition was 0.91 cc as measured by the amount (volume) of the photocurable resin composition used and the temporary cure shrinkage rate. , 0.64 cc of the photocurable resin composition, which corresponds to about 70% of the amount, was applied.

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 main curing shrinkage rate was 1.8%.

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

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 main curing shrinkage rate was 0.3%.

Example 4
Between step (B) and step (D) in Comparative Example 3, as step (C), a photocurable resin composition (step (A ) was applied to the liquid crystal display element side in a line corresponding to the central part of the temporarily cured resin layer using the resin dispenser used in Comparative Example 1. 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 temporarily cured resin layer is measured by the amount (volume) of the photocurable resin composition used and the temporary cure shrinkage rate, and the amount is 0.53 cc. there were.

When the obtained liquid crystal display device was visually observed from the resin cover side for the presence or absence of voids, 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 main 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 concave surface of a curved transparent cover member, and after a temporary curing treatment, the center portion of the temporarily cured resin layer caused by curing shrinkage is removed. A photocurable resin composition is newly applied to the recess, an image display member is laminated, and a main curing process is performed. Therefore, it is possible to prevent the formation of voids on the display surface of the image display device, and also to reduce the residual stress in the photocurable resin layer, thereby preventing the occurrence of color unevenness in the display. Therefore, the manufacturing method of the present invention is useful for industrially manufacturing in-vehicle information terminals equipped with touch panels.

1 Light-transmitting cover member 1a Concave surface of light-transmitting cover member 1x, 1y Both ends 2 Photo-curable resin composition 3 Inner dam material 4 Outer dam material 5 Temporarily cured resin layer 5a Slight dent 6 Image display member 7 Light transmission Curing resin layer D Dispenser

Claims (7)

The image display member and the curved light-transmitting cover member are formed by photocuring a photocurable resin composition such that the total curing shrinkage rate, which is the sum of the temporary curing shrinkage rate and the main curing shrinkage rate, is 5% or more. In a method for manufacturing an image display device laminated with a light-transmissive photocuring resin layer interposed therebetween,
The following steps (A) to (D):
<Process (A)>
A photocurable resin composition is applied to the concave surface of a light-transmissive cover member curved in the shape of a gutter , and the thickness near the uncurved sides of the light-transmissive cover member is thinner, and the thickness is thinner in the center of the curved concave surface. The process of applying the coating so that it becomes thicker ;
<Process (B)>
The applied photocurable resin composition is temporarily cured by irradiating ultraviolet rays so that the temporary curing rate is 40 to 90% and the temporary curing shrinkage rate is 2% or more, and the concave surface is a step of forming a temporarily cured resin layer having a line-shaped minute depression based on curing shrinkage of the photocurable resin composition in the central part;
<Step (C)>
An amount of the same photocurable resin composition as that used in step (A) corresponding to the linear minute depressions in the temporarily cured resin layer was temporarily applied in a line shape to fill the minute depressions. A step of applying the cured resin layer or the image display member;
<Step (D)>
A step of laminating an image display member and a light-transmitting cover member via a temporarily cured resin layer by a vacuum bonding method; and <Step (E)>
forming a light-transparent photo-cured resin layer by irradiating the temporary-cured resin layer sandwiched between the image display member and the light-transparent cover member with ultraviolet rays to fully cure it;
A manufacturing method comprising : 2. The manufacturing method according to claim 1, wherein in the step (C), a photocurable resin composition corresponding to 70% or more of the volume of the microscopic depressions is applied to the corresponding temporarily cured resin layer or image display member. The production according to claim 1 or 2, wherein an inner dam member or an outer dam member is provided on the inner side or the outer side of both ends of the horizontal gutter shape of the light-transmissive cover member, respectively, to define an application area of the photocurable resin composition. Method. 4. The manufacturing method according to claim 3, wherein the inner dam material or the outer dam material is removed between step (B) and step (C). 5. The manufacturing method according to claim 1, 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 5 , wherein in step (E), the temporarily cured resin layer is irradiated with ultraviolet rays for main curing so that the cure rate of the light-transmissive cured resin layer is 95 % or more. Method. 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 manufacturing method according to any one of claims 1 to 6 , wherein the acrylic oligomer is at least one selected from the group consisting of polyurethane (meth)acrylate, polybutadiene (meth)acrylate, and polyisoprene (meth)acrylate. .

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