Reflection-type display body

Abstract

Provided is a reflection-type display body 1 that comprises a light diffusion control layer 11 that has a regular internal structure that comprises a plurality of regions that have a relatively high refractive index within a region that has a relatively low refractive index, a display device 12, and a diffuse reflection plate 13 that has a reflection surface that has an uneven structure. The reflection-type display body 1 is configured such that, when a beam of light that has an angle of incidence of 30° is shined from the four directions at azimuths of 0°, 90°, 180°, and 270° at one arbitrary point on the surface on the light diffusion control layer 11 side to generate reflected light that is diffusely reflected from the one point and the standard deviation of the brightness of the reflected light that both advances within a plane that includes the one point and a normal line and is orthogonal to the azimuth from which the light beam was shined and is also at an angle of no more than 30° from the normal line is calculated for each of the four directions, the average of the four standard deviations is less than 0.25 cd / m2. The reflection-type display body 1 makes it possible to achieve excellent visibility regardless of the vertical direction of display content.

Description

reflective display

[0001] The present invention relates to a reflective display device having a light diffusion control layer that can transmit and diffuse incident light within a predetermined range of incident angles in a strong manner with low optical loss.

[0002] Some displays, such as liquid crystal display devices, organic electroluminescence (EL) displays, and electronic paper, are classified as reflective displays that have a reflective layer. In such reflective displays, the display surface is generally illuminated by a light source such as indoor lighting or the sun, or a light source provided on the display surface side of the display. The light from these light sources is reflected by the reflective layer, allowing the display to be clearly visible due to the reflected light.

[0003] In reflective displays, the positional relationship between the light source and the viewer is usually not constant due to the use of an external light source. As a result, depending on the position of the light source, insufficient light reaches the viewer, reducing visibility and making it difficult to illuminate the entire display brightly. To solve these problems, incorporating a light diffusion plate into the display is considered. However, simply incorporating a typical light diffusion plate does not provide the diffusion required for good visibility, and attempting to achieve high diffusion results in light loss due to stray light and backscattering, impairing image clarity. To solve these problems, it has been considered to provide a light diffusion control layer between the viewer-facing surface and the reflective layer in reflective displays, which can transmit and diffuse incident light within a predetermined incident angle range with high intensity and low light loss (e.g., Patent Documents 1 and 2). The presence of this light diffusion control layer appropriately diffuses light reflected by the reflective layer, reducing the decrease in visibility that depends on the position of the light source.

[0004] Patent No. 6981984 Patent No. 6993976

[0005] Many recent smartphones and tablets have a function that changes the vertical orientation of the display content depending on the orientation of the display screen. That is, when the short side of the display screen is parallel to the ground, the vertical orientation of the display content is parallel to the long side of the display screen, and when the long side of the display screen is parallel to the ground, the vertical orientation of the display content is parallel to the short side of the display screen.

[0006] In such a reflective display device configured so that the up-down direction of the display content on the display surface can be changed, there is a problem in that the effect of improving visibility provided by the light diffusion control layer described above cannot be fully obtained when the up-down direction of the display content is changed. For example, even if good visibility is obtained when the short side of the display surface is parallel to the ground and the up-down direction of the display content is parallel to the long side of the display surface, if the long side of the display surface is parallel to the ground and the up-down direction of the display content is parallel to the short side of the display surface, the light diffusion control layer cannot fully exert its effect, and sufficient visibility cannot be obtained.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a reflective display device that can realize excellent visibility regardless of the vertical direction of the displayed content.

[0008] In order to achieve the above object, firstly, the present invention provides a reflective display comprising a light diffusion control layer having a regular internal structure with a plurality of regions with a relatively high refractive index within a region with a relatively low refractive index, a display device laminated on one side of the light diffusion control layer, and a diffusive reflector laminated on the side of the display device opposite the light diffusion control layer and having a reflective surface on the surface facing the display device, wherein the diffusive reflector has an uneven structure on the reflective surface, and at any one point on the surface facing the light diffusion control layer of the reflective display, When a light ray that forms an angle of 30° with the normal to the surface is irradiated from each of four directions, azimuth angles of 0°, 90°, 180°, and 270°, with the one point as the center, and reflected light that is diffusely reflected from the one point is generated for each of the azimuth angles, when the standard deviation of the luminance of the reflected light that travels within a plane that includes the one point and the normal and is perpendicular to the azimuth angle at which the light ray is irradiated and that forms an angle of 30° or less with the normal is calculated for each of the four directions, the average value of the four standard deviations is 0.25 cd / m ２ The present invention provides a reflective display device characterized by having a reflectance of less than 1000 nm (Invention 1).

[0009] In the above invention (Invention 1), the region with a relatively high refractive index is a columnar object extending from one side of the light diffusion control layer to the other side, and the light diffusion control layer has at least one layer having a columnar structure in which the columns are arranged in the region with a relatively low refractive index, and it is preferable that in at least some of the columns, a straight line parallel to the direction of extension is inclined with respect to the thickness direction of the light diffusion control member (Invention 2).

[0010] In the above inventions (Inventions 1 and 2), the diffuse reflector is preferably a reflective electrode (Invention 3).

[0011] In the above inventions (Inventions 1 to 3), when a light beam that forms an angle of 30° with the normal to the surface of the reflective display device is irradiated from four directions with azimuth angles of 0°, 90°, 180°, and 270° from the center of an arbitrary point on the surface of the light diffusion control layer side of the reflective display device, and when reflected light that is diffused and reflected from the point is generated for each of the azimuth angles, the luminance (cd / m ２ ) is measured in each of the four directions, and the maximum luminance among them is L ｍａｘ The minimum luminance is L ｍｉｎ In this case, the L ｍａｘ and the L ｍｉｎ However, 0.6≦L ｍｉｎ / L ｍａｘ It is preferable that the relationship: <1 is satisfied (Invention 4).

[0012] In the above inventions (inventions 1 to 4), it is preferable that the display content is configured so that the up-down direction can be changed (invention 5).

[0013] The reflective display according to the present invention can achieve excellent visibility regardless of the vertical direction of the displayed content.

[0014] Fig. 1 is a cross-sectional view of a reflective display body according to one embodiment of the present invention; Fig. 2 is a perspective view schematically showing an example of a regular internal structure (column structure) of a light diffusion control layer according to one embodiment of the present invention; Fig. 3 is a perspective view illustrating various directions related to a light diffusion control layer according to one embodiment of the present invention; Fig. 4 is a diagram illustrating a method for measuring optical properties of a reflective display body according to one embodiment of the present invention; Fig. 5 is a diagram illustrating a method for measuring optical properties of a reflective display body according to one embodiment of the present invention.

[0015] An embodiment of the present invention will now be described. Fig. 1 shows a cross-sectional view of a reflective display device according to one embodiment of the present invention. The reflective display device 1 according to this embodiment includes a light diffusion control layer 11 having a regular internal structure with a plurality of regions with a relatively high refractive index within a region with a relatively low refractive index, a display device 12 laminated on one side of the light diffusion control layer 11, and a diffusion reflector 13 laminated on the side of the display device 12 opposite the light diffusion control layer 11 and having a reflective surface facing the display device 12.

[0016] In the reflective display device 1 according to this embodiment, the diffusion reflector 13 has an uneven structure on the reflecting surface.

[0017] The reflective display body 1 according to this embodiment satisfies the following condition regarding reflection: When a light ray that forms an angle of 30° with the normal to the surface of the reflective display body 1 on the side of the light diffusion control layer 11 is irradiated from four directions, each of which has an azimuth angle of 0°, 90°, 180°, and 270° from the point as the center, to generate reflected light that is diffused and reflected from the point for each of the azimuth angles, and the standard deviation of the luminance of the reflected light that travels within a plane that includes the point and the normal and is perpendicular to the azimuth angle at which the light ray is irradiated and that forms an angle of 30° or less with the normal is calculated for each of the four directions, the average of the four standard deviations is 0.25 cd / m ２ It will be less than.

[0018] The reflective display body 1 according to this embodiment satisfies the above-mentioned conditions regarding reflection, and can diffuse and reflect external light incident on the display surface of the reflective display body 1 back toward the display surface. This reflected light allows the viewer to view the display content on the display device 12.

[0019] Furthermore, with regard to the regular internal structure in the light diffusion control layer 11, Fig. 2 schematically shows a columnar structure (described in detail later) as an example of such a regular internal structure. In this columnar structure, as shown in Fig. 2 (particularly Fig. 2(c)), a plurality of regions 111 (columnar objects) having a relatively high refractive index extend in the thickness direction, and are surrounded by regions 112 having a relatively low refractive index. Here, the regular internal structure refers to an internal structure in which a plurality of regions 111 having a relatively high refractive index are arranged with a predetermined regularity within the regions 112 having a relatively low refractive index (for example, an internal structure in which, when a cross section obtained by cutting the light diffusion control layer 11 along a plane parallel to the surface of the layer 11 at a position where the regular internal structure is present is viewed, the regions 111 having a relatively high refractive index are repeatedly arranged with a similar pitch within the regions 112 having a relatively low refractive index along at least one direction in the cross section). The regular internal structure here is distinguished from a phase-separated structure in which one phase exists without any clear regularity within another phase, and a sea-island structure in which approximately spherical island components exist within a sea component, in that the regular internal structure is formed by regions 111 having a relatively high refractive index extending in the thickness direction of the light diffusion control layer 11.

[0020] The light diffusion control layer 11 has the above-mentioned regular internal structure, and therefore transmits and diffuses incident light within a predetermined range of incident angles in an intense manner with low optical loss.

[0021] The reflective display 1 according to this embodiment combines the effect of diffusing and reflecting light with the effect of transmitting and diffusing light at a predetermined incident angle by the light diffusion control layer 11, thereby achieving sufficiently high brightness measured from the front direction regardless of the position of the external light source. This allows the viewer to view the display content with sufficient brightness in the reflective display 1 according to this embodiment. Furthermore, even when the reflective display is turned on its side to change the vertical direction of the display content, brightness fluctuations can be kept small. Furthermore, uneven brightness can be effectively suppressed when the viewing angle is changed (for example, when the display surface is viewed from an oblique direction). Therefore, the reflective display 1 according to this embodiment is preferably a reflective display configured so that the vertical direction of the display content can be changed.

[0022] 1. Light Diffusion Control Layer The light diffusion control layer 11 in this embodiment is not particularly limited as long as it has a regular internal structure with a plurality of regions with a relatively high refractive index within a region with a relatively low refractive index. From the viewpoint of facilitating the formation of such a regular internal structure, the light diffusion control layer 11 in this embodiment is preferably formed by curing a composition for a light diffusion control layer that contains a high refractive index component and a low refractive index component having a refractive index lower than that of the high refractive index component. In particular, it is preferable that the high refractive index component and the low refractive index component each have one or two polymerizable functional groups.

[0023] (1) High Refractive Index Component Preferred examples of the high refractive index component include (meth)acrylic acid esters containing an aromatic ring, and particularly preferred are (meth)acrylic acid esters containing multiple aromatic rings. Examples of (meth)acrylic acid esters containing multiple aromatic rings include biphenyl (meth)acrylate, naphthyl (meth)acrylate, anthracyl (meth)acrylate, benzylphenyl (meth)acrylate, biphenyloxyalkyl (meth)acrylate, naphthyloxyalkyl (meth)acrylate, anthracyloxyalkyl (meth)acrylate, benzylphenyloxyalkyl (meth)acrylate, and the like, as well as those partially substituted with halogen, alkyl, alkoxy, alkyl halide, or the like. Among these, biphenyl (meth)acrylate is preferred from the viewpoint of ease of forming a good regular internal structure, and specifically, o-phenylphenoxyethyl acrylate, o-phenylphenoxyethoxyethyl acrylate, and the like are preferred. Note that, in this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. The same applies to other similar terms.

[0024] The molecular weight of the high refractive index component is preferably 150 to 2500, particularly preferably 200 to 1500, and even more preferably 250 to 1000. This facilitates the formation of a light diffusion control layer 11 having a desired regular internal structure. Note that, if the theoretical molecular weight of the high refractive index component can be determined based on its molecular structure, the molecular weight of the high refractive index component refers to that theoretical molecular weight. On the other hand, if the theoretical molecular weight is difficult to determine because the high refractive index component is, for example, a polymer component, the molecular weight of the high refractive index component refers to the weight-average molecular weight obtained as a value converted into standard polystyrene by gel permeation chromatography (GPC). Note that, in this specification, the measurement method for weight-average molecular weight refers to the value converted into standard polystyrene by the GPC method.

[0025] The refractive index of the high refractive index component is preferably 1.45 to 1.70, more preferably 1.50 to 1.65, particularly preferably 1.54 to 1.62, and even more preferably 1.56 to 1.59. This makes it easier to form a light diffusion control layer 11 having a desired regular internal structure. Note that the refractive index in this specification refers to the refractive index of a predetermined component before the composition for the light diffusion control layer is cured, and this refractive index is measured in accordance with JIS K0062:1992.

[0026] The content of the high refractive index component in the composition for light diffusion control layer is preferably 25 to 400 parts by mass, more preferably 50 to 350 parts by mass, particularly preferably 75 to 300 parts by mass, and even more preferably 100 to 200 parts by mass, relative to 100 parts by mass of the low refractive index component. This ensures that the regular internal structure of the formed light diffusion control layer 11 has regions derived from the high refractive index component and regions derived from the low refractive index component in the desired ratio, making it easier to form the desired regular internal structure.

[0027] (2) Low refractive index component Preferred examples of the low refractive index component include urethane (meth)acrylate, (meth)acrylic polymers having (meth)acryloyl groups in their side chains, (meth)acryloyl group-containing silicone resins, and unsaturated polyester resins. Among these, it is particularly preferable to use urethane (meth)acrylate because it is easy to form a good regular internal structure. More specifically, it is preferable to use urethane (meth)acrylate formed from (a) a compound containing at least two isocyanate groups, (b) a polyalkylene glycol, and (c) a hydroxyalkyl (meth)acrylate.

[0028] Preferred examples of the (a) compound containing at least two isocyanate groups include aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biurets and isocyanurates thereof, as well as adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, alicyclic polyisocyanates are preferred, and alicyclic diisocyanates are particularly preferred.

[0029] Preferred examples of the polyalkylene glycol (b) include polyethylene glycol, polypropylene glycol, polybutylene glycol, polyhexylene glycol, etc., and among these, polypropylene glycol is preferred. The weight-average molecular weight of the polyalkylene glycol (b) is preferably 2,300 to 19,500, more preferably 3,000 to 14,300, and even more preferably 4,000 to 12,300.

[0030] Preferred examples of the (c) hydroxyalkyl(meth)acrylate include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 3-hydroxybutyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate, and among these, 2-hydroxyethyl(meth)acrylate is preferred.

[0031] The synthesis of a urethane (meth)acrylate using the above-mentioned components (a) to (c) as materials can be carried out according to a conventional method. In this case, from the viewpoint of efficiently synthesizing the urethane (meth)acrylate, the blending ratio of components (a) to (c) is preferably component (a):component (b):component (c)=1-5:1:1-5, and particularly preferably 1-3:1:1-3.

[0032] The weight average molecular weight of the low refractive index component is preferably 3,000 to 20,000, particularly preferably 5,000 to 15,000, and further preferably 7,000 to 13,000. This makes it easier to form the light diffusion control layer 11 having a desired regular internal structure.

[0033] The refractive index of the low refractive index component is preferably 1.30 to 1.59, more preferably 1.38 to 1.50, particularly preferably 1.42 to 1.49, and even more preferably 1.46 to 1.48, which makes it easier to form the light diffusion control layer 11 having the desired regular internal structure.

[0034] (3) Other Additives The composition for the light diffusion control layer described above may contain other additives in addition to the high refractive index component and the low refractive index component. Examples of the other additives include polyfunctional monomers (compounds having three or more polymerizable functional groups), photopolymerization initiators, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, polymerization accelerators, polymerization inhibitors, infrared absorbers, plasticizers, diluting solvents, and leveling agents.

[0035] (3-1) Photopolymerization Initiator The composition for the light diffusion control layer preferably contains a photopolymerization initiator as another additive, which makes it easier to efficiently form the light diffusion control layer 11 having the desired regular internal structure.

[0036] Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2- propyl ketone, benzophenone, p-phenylbenzophenone, 4,4-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamine benzoic acid ester, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propane], etc. These may be used alone or in combination of two or more.

[0037] When a photopolymerization initiator is used, the content of the photopolymerization initiator in the composition for light diffusion control layer is preferably 0.2 to 20 parts by mass, more preferably 0.5 to 16 parts by mass, particularly preferably 1 to 13 parts by mass, and even more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the total amount of the high refractive index component and the low refractive index component. This makes it easy to efficiently form the light diffusion control layer 11 having the desired regular internal structure.

[0038] (3-2) Ultraviolet Absorber The composition for light diffusion control layer preferably contains an ultraviolet absorber as another additive. When the composition for light diffusion control layer contains an ultraviolet absorber, when a coating film of the composition for light diffusion control layer is irradiated with active energy rays, the ultraviolet absorber selectively absorbs active energy rays of a predetermined wavelength within a predetermined range. By optimizing the type and amount of ultraviolet absorber, bending of the formed region 111 (columnar structure) having a relatively high refractive index can be easily caused without inhibiting the curing of the composition for light diffusion control layer. As a result, the light diffusion control layer 11 can achieve a wider range of light diffusion angles, making it easier to further improve brightness when viewed from the front.

[0039] Examples of the ultraviolet absorber include a benzotriazole-based ultraviolet absorber, a hydroxyphenyltriazine-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a hydroxybenzoate-based ultraviolet absorber, etc. Among these, it is preferable to use at least one of a benzotriazole-based ultraviolet absorber and a benzophenone-based ultraviolet absorber, and it is particularly preferable to use a benzotriazole-based ultraviolet absorber. The above-mentioned ultraviolet absorbers may be used alone or in combination of two or more.

[0040] When an ultraviolet absorber is used, the content of the ultraviolet absorber in the composition for the light diffusion control layer is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 1 part by mass, particularly preferably 0.03 to 0.5 parts by mass, and even more preferably 0.06 to 0.1 parts by mass, per 100 parts by mass of the total amount of the high refractive index component and the low refractive index component. This allows for efficient bending of the region 111 (columnar structure) with a relatively high refractive index. As a result, the light diffusion control layer 11 can achieve a wider angular range of light diffusion, making it easier to further improve brightness when viewed from the front.

[0041] (4) Preparation of composition for light diffusion control layer The composition for light diffusion control layer can be prepared by uniformly mixing the high refractive index component and low refractive index component described above, and, if desired, other additives such as a photopolymerization initiator and an ultraviolet absorber.

[0042] During the mixing, a uniform composition for a light diffusion control layer may be obtained by stirring while heating to a temperature of 40 to 80° C. Furthermore, a dilution solvent may be added and mixed so that the resulting composition for a light diffusion control layer has a desired viscosity.

[0043] (5) Regular Internal Structure As described above, the light diffusion control layer 11 in this embodiment has a regular internal structure therein that includes a plurality of regions 111 with a relatively high refractive index within a region 112 with a relatively low refractive index. Examples of the regular internal structure include the column structure described above, as well as a louver structure in which a plurality of plate-like regions with different refractive indexes are alternately arranged in any one direction along the film surface.

[0044] In the light diffusion control layer 11 of this embodiment, the regular internal structure is preferably a column structure, from the viewpoints of easily achieving good brightness when viewed from the front and easily suppressing fluctuations in brightness when the vertical direction of the display content is changed. More specifically, in the light diffusion control layer 11 of this embodiment, the region with a relatively high refractive index is preferably made of columns 111 extending from one surface side to the other surface side of the light diffusion control layer 11, and the light diffusion control layer 11 preferably includes at least one layer having a column structure in which the columns 111 stand in a forest in the region with a relatively low refractive index. Figure 2 is a perspective view schematically illustrating such a column structure.

[0045] When light incident on the light diffusion control layer 11 having such a column structure is within a predetermined range of incident angles, it exits the light diffusion control layer 11 while being strongly diffused with a predetermined opening angle. On the other hand, when the incident light is incident at an angle outside the above-mentioned range of incident angles, the light is transmitted without being diffused or is emitted with weaker diffusion than incident light within the above-mentioned range of incident angles. Note that, when a contrast medium is placed parallel to the surface of the light diffusion control layer 11, the diffused light caused by incident light within the above-mentioned range of incident angles due to the column structure becomes circular or nearly circular (e.g., elliptical) that spreads in both directions. On the other hand, when the weak diffusion caused by incident light outside the above-mentioned range of incident angles occurs, the diffused light becomes crescent-shaped.

[0046] Furthermore, in the light diffusion control layer 11 of this embodiment, from the viewpoint of more easily achieving good brightness when viewed from the front and more easily suppressing fluctuations in brightness when the up-down direction of the display content is changed, it is preferable that in at least a portion of the columns 111, the straight lines parallel to the extension direction are inclined with respect to the thickness direction of the light diffusion control layer 11. All of the three types of column structures shown in Figure 2 are inclined. Note that the column structure shown in Figure 2(b) has a form in which two layers of standing columns 111 are stacked, and in one layer (the upper layer on the paper surface), the columns 111 stand nearly vertically, while in the other layer (the lower layer on the paper surface) the columns stand at an incline.

[0047] The above-mentioned inclination will be explained in more detail with reference to Fig. 3. The perspective view of Fig. 3 shows only one relatively high refractive index region (columnar structure) 111 omitted for the sake of explanation, out of the multiple relatively high refractive index regions (columnar structures) 111 that would normally be present inside the light diffusion control layer 11. In Fig. 3, the relatively high refractive index region (columnar structure) 111 extends from the bottom to the top in Fig. 3, and a straight line parallel to the direction of extension (direction A) is inclined by an angle a with respect to the thickness direction (direction B) of the light diffusion control layer 11.

[0048] In addition, when the region (columnar structure) 111 with a relatively high refractive index is bent as described below, the above-mentioned extension direction (direction A) refers to the extension direction of the columnar structure from the bent portion to one end, and in particular, refers to the extension direction from the bent portion to one end on the viewer side.

[0049] In the reflective display device 1 according to this embodiment, the angle a is preferably greater than 0°, particularly preferably 1° or greater, and even more preferably 2° or greater. This allows the displayed content to be displayed brighter. The angle a is also preferably 30° or less, more preferably 15° or less, particularly preferably 8° or less, and even more preferably 5° or less. This allows the difference in brightness when the up / down direction of the displayed content is changed to be further reduced. The angle a can be measured by observing the cross section of the light diffusion control layer 11 using an optical digital microscope.

[0050] Furthermore, in the light diffusion control layer 11 of this embodiment, from the viewpoint of easily exhibiting the desired performance, it is preferable that the columns 111 in at least one layer of the columnar structure bend between one end and the other end. The column structure shown in Figure 2(a) is an example of a column structure having such bent columns 111. Also, in the column structure shown in Figure 2(b), the columns 111 are bent in the lower layer.

[0051] Furthermore, the light diffusion control layer 11 in this embodiment preferably includes two layers each having a columnar structure. That is, it is also preferable that the light diffusion control layer 11 be a stack of two layers each consisting of a forest of columns 111, as in the column structure shown in FIG. 2( b). In this case, the inclination and bending modes of each layer may be the same or different between the two layers. However, as in the column structure shown in FIG. 2( b), the light diffusion control layer preferably includes two layers: Layer 1 consisting of a forest of columns extending substantially parallel to the thickness direction of the light diffusion control layer (i.e., substantially perpendicular to the main surface of the light diffusion control layer), and Layer 2 consisting of columns that are inclined with respect to the thickness direction of the light diffusion control layer and bent partway along the extending direction. Furthermore, it is particularly preferable that Layer 1 of Layer 1 and Layer 2 be positioned closer to the viewer.

[0052] In the columnar structure described above, the difference in refractive index between the relatively high refractive index region 111 (columnar structure) and the relatively low refractive index region 112 is preferably 0.01 or greater, particularly 0.05 or greater, and even more preferably 0.1 or greater. This allows for effective diffusion. The upper limit of this difference is not particularly limited and may be, for example, 0.3 or less. The refractive index used to calculate this difference refers to the refractive index measured for the cured products obtained by curing the materials of the relatively high refractive index region 111 and the relatively low refractive index region 112 individually. The material referred to here may contain, in addition to the high refractive index component and low refractive index component described above as essential components, other additives such as the photopolymerization initiator and UV absorber described above, as necessary. If other additives are used, the content and specific examples thereof may be as described above.

[0053] The above-mentioned columns preferably have a structure in which their diameter increases from one surface to the other surface of the light diffusion control layer 11. Columns having such a structure are more likely to change the direction of light traveling parallel to the extending direction of the columns than columns whose diameter remains almost constant from one surface to the other. This allows the light diffusion control layer 11 to effectively diffuse light.

[0054] Furthermore, the maximum diameter of the cross section of the columnar structure when cut along a plane horizontal to the extension direction is preferably 0.1 to 15 μm, particularly preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the maximum diameter is within the above range, the light diffusion control layer 11 can effectively diffuse light. Note that the cross-sectional shape of the columnar structure when cut along a plane perpendicular to the extension direction is not particularly limited, but is preferably, for example, a circle, an ellipse, a polygon, an irregular shape, or the like.

[0055] In the above-described columnar structure, the distance between adjacent columns is preferably 0.1 to 15 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the distance between adjacent columns is within the above range, the light diffusion control layer 11 can effectively diffuse light.

[0056] The dimensions of the regular internal structure of the column structure can be measured by observing the cross section of the column structure using an optical digital microscope.

[0057] (6) Thickness of the Light Diffusion Control Layer The thickness of the light diffusion control layer 11 is preferably 1 to 500 μm, more preferably 10 to 400 μm, and particularly preferably 30 to 300 μm. This facilitates achieving good brightness when viewed from the front and suppressing brightness fluctuations when the display content is rotated up and down. It also prevents image blurring and a decrease in total light transmittance. From the perspective of more easily achieving good brightness when viewed from the front, the thickness of the light diffusion control layer 11 is preferably 40 to 200 μm, particularly preferably 50 to 160 μm, and even more preferably 60 to 120 μm. Furthermore, from the perspective of more easily suppressing brightness fluctuations when the display content is rotated up and down, the thickness is preferably 50 to 280 μm, particularly preferably 75 to 260 μm, and even more preferably 100 to 240 μm, with 120 to 220 μm being particularly preferred.

[0058] When the light diffusion control layer 11 has the two-layer laminated structure shown in FIG. 2( b), the total thickness of the two layers is preferably 1 to 500 μm, more preferably 50 to 400 μm, particularly preferably 100 to 300 μm, and even more preferably 150 to 250 μm. Furthermore, of the two layers, the thickness of the layer located on the viewer side is preferably 1 to 300 μm, more preferably 25 to 200 μm, and particularly preferably 50 to 150 μm. Furthermore, of the two layers, the thickness of the layer located on the opposite side from the viewer is preferably 1 to 300 μm, more preferably 25 to 200 μm, and particularly preferably 50 to 150 μm. By satisfying the above conditions, it becomes easier to achieve good brightness when viewed from the front and to suppress fluctuations in brightness when the vertical orientation of the display content is changed.

[0059] 2. Display Device The display device 12 in this embodiment is not particularly limited and may be a display device incorporated into a general reflective display. For example, the display device 12 may be a liquid crystal display, an organic EL display, electronic paper, an electrophoretic display, a MEMS display, a solid-state crystal display, or the like. The display device 12 may also be a display having a touch panel laminated thereon.

[0060] 3. Diffuse Reflector As described above, the diffuse reflector 13 in this embodiment is not particularly limited as long as it has an uneven structure on its reflective surface. However, from the viewpoint of making it easier for the reflective display device 1 according to this embodiment to satisfy the above-mentioned condition for the standard deviation of luminance, it is preferable that the diffuse reflector 13 satisfy the following condition regarding reflected light.

[0061] As a premise, a light ray is irradiated onto any one point on the reflecting surface of the diffuse reflector 13 alone, at an angle of 30° with the normal to the reflecting surface, generating reflected light that is diffusely reflected from the one point. In this case, in the diffuse reflector 13 of this embodiment, it is preferable that the ratio of the brightness of reflected light that forms an angle of 40° or less with the direction of specular reflection to the brightness of all reflected light (hereinafter sometimes referred to as the "percentage within 40°") is 80% or more. Furthermore, in the diffuse reflector 13 of this embodiment, the ratio of the brightness of specularly reflected light to the brightness of all reflected light (hereinafter sometimes referred to as the "percentage of specular reflection") is 60% or less.

[0062] By satisfying the above conditions, the diffuse reflector 13 in this embodiment can appropriately diffuse and reflect external light incident on the reflective display device 1. As a result, in combination with the function of the light diffusion control layer 11, it is possible to achieve good brightness when viewed from the front and to easily suppress fluctuations in brightness when the vertical orientation of the displayed content is changed. From this perspective, the percentage within 40° described above is preferably 90% or more. The upper limit of the percentage within 40° described above is not particularly limited, and is preferably 99% or less, particularly preferably 95% or less, and even more preferably 90% or more. From the same perspective, the percentage of specular reflection described above is preferably 55% or less, and even more preferably 50% or less. The lower limit of the percentage of specular reflection described above is not particularly limited, and is preferably 20% or more, particularly preferably 30% or more, and even more preferably 40% or more. The proportion within 40° and the proportion of specular reflection can be calculated, for example, by irradiating a light beam onto any point on the reflective surface of the diffuse reflector 13 so that the angle with the normal to the reflective surface is 30°, and then measuring the resulting reflected light using a conoscope in reflection mode from the luminance distribution.

[0063] As described above, the diffuse reflector 13 in this embodiment has an uneven structure and satisfies the above-mentioned conditions for reflection, and is different from reflectors having a specular surface such as a mirror.

[0064] The diffuse reflector 13 in this embodiment has an uneven structure on its reflective surface, and its composition is not particularly limited as long as it satisfies the above-mentioned reflection conditions. A preferred example of the diffuse reflector 13 is a reflective electrode. In this case, the reflective electrode may be incorporated into the display device 12, for example. The reflective electrode is not usually provided so as to cover the entire display surface of the reflective display unit 1, and there are also portions where no electrode is formed. Therefore, in a reflective display unit 1 equipped with a reflective electrode, the reflective electrode can reflect external light, while the portions where no electrode is formed can transmit light from a backlight or the like provided on the back of the display device 12. The material of the reflective electrode serving as the diffuse reflector 13 is not particularly limited, and it can be formed from a common reflective electrode material.

[0065] 1, the diffusive reflector 13 is depicted as a component independent of the display device 12. The diffusive reflector 13 is depicted as existing across the entire lateral area (the entire surface of the display device 12 opposite the light diffusion control layer 11). However, the reflective display device 1 according to this embodiment is not limited to that shown in FIG. 1, and also includes those that include the above-described reflective electrode as the diffusive reflector 13.

[0066] Other examples of the diffuse reflector 13 include a semi-transmissive / semi-reflective member that exhibits both light transmission and light reflection properties, and a metal vapor deposition film obtained by vapor-depositing a metal on a predetermined surface. Preferred examples of the metal include aluminum, silver, and nickel. The diffuse reflector 13 made of a metal vapor deposition film may be provided on the surface of a resin film that serves as a support.

[0067] 4. Other Configurations The reflective display device 1 according to this embodiment may include components other than the light diffusion control layer 11, the display device 12, and the diffuse reflector 13 described above. For example, from the viewpoint of improving the adhesion between the light diffusion control layer 11, the display device 12, and the diffuse reflector 13, an adhesive layer may be provided between the light diffusion control layer 11 and the display device 12 and between the display device 12 and the diffuse reflector 13. The adhesive constituting the adhesive layer is preferably transparent. Although the adhesive is not particularly limited, an acrylic adhesive is preferred from the viewpoint of easily achieving the desired adhesive strength and transparency.

[0068] Furthermore, the reflective display 1 according to this embodiment may be provided with a surface coating layer, a cover panel, or the like on the side of the light diffusion control layer 11 opposite the display device 12. Furthermore, from the viewpoint of supplementing brightness, a backlight may be provided at a desired position (for example, on the side of the diffusion reflector 13 opposite the display device 12).

[0069] 5. Physical Properties of the Reflective Display Unit (1) Front Brightness In the reflective display unit 1 according to this embodiment, when a light ray that forms an angle of 30° with the normal to the surface of the reflective display unit 1 on the side of the light diffusion control layer 11 is irradiated from each of four directions with azimuth angles of 0°, 90°, 180°, and 270° from the point as the center, and reflected light that is diffused and reflected from the point is generated for each of the azimuth angles, it is preferable that the following condition be satisfied.

[0070] That is, the luminance (cd / m) of the reflected light (the light ray indicated by reference numeral 203 in FIG. 5(a)) reflected in the direction perpendicular to the surface is ２ ) is measured in each of the four directions, and the maximum luminance is defined as L ｍａｘ The minimum luminance is L ｍｉｎ In this case, the above L ｍａｘ and the above L ｍｉｎ However, 0.6≦L ｍｉｎ / L ｍａｘ It is preferable that the relationship:

[0071] By satisfying the above conditions, it becomes easier to achieve good brightness when viewed from the front, and it also becomes easier to suppress fluctuations in brightness when the up-down direction of the display content is changed. ｍｉｎ / L ｍａｘ is more preferably 0.62 or more, and particularly preferably 0.64 or more. ｍｉｎ / L ｍａｘ is more preferably 0.9 or less, particularly preferably 0.8 or less, and further preferably 0.75 or less.

[0072] Furthermore, L ｍｉｎ / L ｍａｘ From the viewpoint of easily satisfying the above-mentioned relationship, the luminance of the reflected light reflected in the direction perpendicular to the surface when irradiated from an azimuth angle of 0° is 0.1 to 100 cd / m ２ It is preferable that the brightness is 0.3 to 50 cd / m ２ It is more preferable that the brightness is 0.5 to 10 cd / m ２ It is preferable that the brightness is 0.7 to 5 cd / m ２ It is preferable that the brightness is 0.8 to 2 cd / m ２ It is preferable that:

[0073] Also, L ｍｉｎ / L ｍａｘ From the viewpoint of easily satisfying the above-mentioned relationship, the luminance of the reflected light reflected in the direction perpendicular to the surface when irradiated from an azimuth angle of 90° is 0.1 to 100 cd / m ２ It is preferable that the brightness is 0.3 to 50 cd / m ２ It is more preferable that the brightness is 0.5 to 10 cd / m ２ It is preferable that the brightness is 0.7 to 5 cd / m ２ It is preferable that the brightness is 0.8 to 2 cd / m ２ It is preferable that:

[0074] Also, L ｍｉｎ / L ｍａｘ From the viewpoint of easily satisfying the above-mentioned relationship, the luminance of the reflected light reflected in the direction perpendicular to the surface when irradiated from an azimuth angle of 180° is 0.1 to 100 cd / m２ It is preferable that the brightness is 0.3 to 50 cd / m ２ It is more preferable that the brightness is 0.5 to 10 cd / m ２ It is preferable that the brightness is 0.7 to 5 cd / m ２ It is preferable that the brightness is 0.8 to 2 cd / m ２ It is preferable that:

[0075] Also, L ｍｉｎ / L ｍａｘ From the viewpoint of easily satisfying the above-mentioned relationship, the luminance of the reflected light reflected in the direction perpendicular to the surface when irradiated from an azimuth angle of 270° is 0.1 to 100 cd / m ２ It is preferable that the brightness is 0.3 to 50 cd / m ２ It is more preferable that the brightness is 0.5 to 10 cd / m ２ It is preferable that the brightness is 0.7 to 5 cd / m ２ It is preferable that the brightness is 0.8 to 2 cd / m ２ It is preferable that:

[0076] The details of the method for measuring the brightness in the front direction are as described in the test examples below.

[0077] (2) Standard deviation of brightness In the reflective display device 1 according to this embodiment, as described above, when a light ray that forms an angle of 30° with the normal to the surface of the reflective display device 1 on the side of the light diffusion control layer 11 of the reflective display device 1 is irradiated from each of four directions with azimuth angles of 0°, 90°, 180°, and 270° from the point as the center, and reflected light that is diffused and reflected from the point is generated for each of the azimuth angles, the following condition is satisfied.

[0078] That is, when the standard deviation of the luminance of the reflected light traveling in a plane (plane P in FIG. 5B) that includes the one point and the normal line and is perpendicular to the azimuth angle at which the light ray is irradiated and that forms an angle of 30° or less with the normal line is calculated for each of the four directions, the average value of the four standard deviations is 0.25 cd / m ２ is less than.

[0079] By satisfying the above conditions, it becomes easier to achieve good brightness when viewed from the front, and it also becomes easier to suppress fluctuations in brightness when the vertical direction of the display content is changed. From this perspective, the average value of the above four standard deviations is 0.20 cd / m ２ More preferably, it is 0.18 cd / m or less, and particularly 0.18 cd / m ２ It is preferable that the brightness is 0.16 cd / m or less, and more preferably 0.16 cd / m or less. ２ It is preferable that the brightness is 0.14 cd / m or less, and more preferably 0.14 cd / m or less. ２ The lower limit of the average value of the four standard deviations is not particularly limited, and is, for example, 0.01 cd / m ２ It is preferable that the brightness is equal to or higher than 0.04 cd / m ２ It is preferable that the brightness is 0.07 cd / m or more, and more preferably 0.07 cd / m ２ It is preferable that this is equal to or greater than this.

[0080] Furthermore, from the viewpoint of making it easier to satisfy the above condition regarding the average value of the four standard deviations, the standard deviation when irradiated from an azimuth angle of 0° is set to 0.01 to 0.40 cd / m ２ is preferably 0.02 to 0.30 cd / m ２ More preferably, it is 0.04 to 0.25 cd / m ２ It is preferable that the brightness is 0.07 to 0.20 cd / m ２ It is preferable that:

[0081] In addition, from the viewpoint of making it easier to satisfy the above condition regarding the average value of the four standard deviations, the standard deviation when irradiated from an azimuth angle of 90° is set to 0.01 to 0.40 cd / m ２ is preferably 0.02 to 0.30 cd / m ２ More preferably, it is 0.04 to 0.25 cd / m ２ It is preferable that the brightness is 0.07 to 0.20 cd / m ２ It is preferable that:

[0082] In addition, from the viewpoint of making it easier to satisfy the above condition regarding the average value of the four standard deviations, the standard deviation when irradiated from an azimuth angle of 180° is set to 0.01 to 0.40 cd / m ２is preferably 0.02 to 0.30 cd / m ２ More preferably, it is 0.04 to 0.25 cd / m ２ It is preferable that the brightness is 0.07 to 0.20 cd / m ２ It is preferable that:

[0083] In addition, from the viewpoint of making it easier to satisfy the above condition regarding the average value of the four standard deviations, the standard deviation when irradiated from an azimuth angle of 270° is set to 0.01 to 0.40 cd / m ２ is preferably 0.02 to 0.30 cd / m ２ More preferably, it is 0.04 to 0.25 cd / m ２ It is preferable that the brightness is 0.07 to 0.20 cd / m ２ It is preferable that:

[0084] The method for measuring the standard deviation of the luminance is described in detail in the test examples below.

[0085] 6. Manufacturing Method of Reflective Display Unit The manufacturing method of the reflective display unit 1 according to this embodiment is not particularly limited, and it can be manufactured by a conventional manufacturing method. For example, the light diffusion control layer 11, the display device 12, and the diffusion reflector 13 can be prepared and manufactured, and then the reflective display unit 1 can be obtained by laminating them.

[0086] The method for forming the light diffusion control layer 11 is not particularly limited, and it can be formed by a conventionally known method.

[0087] For example, the composition for a light diffusion control layer described above is applied to one side of a process sheet to form a coating film, and then one side (particularly the release side) of a release sheet is laminated to the side of the coating film opposite the process sheet. Subsequently, the coating film is irradiated with active energy rays through the process sheet or through the release sheet to cure it, thereby forming the light diffusion control layer 11. By laminating the release sheet on the coating film in this way, a gap is maintained between the release sheet and the process sheet, preventing the coating film from being crushed, and facilitating the formation of a light diffusion control layer 11 having a uniform thickness and a desired regular internal structure.

[0088] Alternatively, for example, the composition for the light diffusion control layer described above may be applied to one side of a process sheet to form a coating film, and then the coating film may be irradiated with active energy rays for a first time to cause primary curing. Then, one side of a release sheet may be attached to the side of the coating film opposite the process sheet. The coating film may then be irradiated with active energy rays for a second time through the process sheet or the release sheet to cause secondary curing, thereby forming the light diffusion control layer 11. In this way, curing by irradiation with active energy rays in two stages facilitates the formation of a two-layer laminated light diffusion control layer 11 as shown in FIG. 2( b).

[0089] Examples of the coating method include knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating. The composition for the light diffusion control layer may be diluted with a solvent as needed.

[0090] The coating film is irradiated with active energy rays in different ways depending on the regular internal structure to be formed. Such irradiation can be carried out by a conventionally known method. For example, when the aforementioned columnar structure is to be formed, the coating film is irradiated with parallel light having a high degree of parallelism.

[0091] The active energy rays refer to electromagnetic waves or charged particle rays that have an energy quantum, and specific examples include ultraviolet rays, electron beams, etc. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle and can easily form a desired regular internal structure.

[0092] When ultraviolet rays are used as active energy rays to form a columnar structure, the irradiation conditions are as follows: a peak irradiance on the coating surface of 0.1 to 10 mW / cm ２ The peak irradiance here means the measured value at the point where the active energy rays irradiated onto the coating film surface exhibit the maximum value. Furthermore, it is preferable that the integrated light amount on the coating film surface is 5 to 200 mJ / cm. ２ It is preferable to set the following.

[0093] From the viewpoint of completing the curing more reliably, it is also preferable to irradiate the cured product with normal active energy rays (active energy rays that have not been subjected to a process for converting them into parallel light or band-like light, or scattered light) after curing using the parallel light or band-like light as described above.

[0094] 7. Method of Using the Reflective Display The reflective display according to this embodiment can be used in the same way as a conventional reflective display. In particular, as described above, the reflective display according to this embodiment can effectively suppress fluctuations in brightness even when the vertical direction of the displayed content is changed, and therefore is suitable for use as a reflective display in which the vertical direction of the displayed content can be changed.

[0095] In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also means "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is stated that "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[0096] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0097] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0098] Example 1 (1) Preparation of Composition for Light Diffusion Control Layer To 40 parts by mass (solids equivalent value; the same applies hereinafter) of polyether urethane methacrylate as a low refractive index component, which had a weight average molecular weight of 9,900 and was obtained by reacting polypropylene glycol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate, 60 parts by mass of o-phenylphenoxyethoxyethyl acrylate as a high refractive index component, which had a molecular weight of 268, 8 parts by mass of 2-hydroxy-2-methyl-1-phenylpropan-1-one as a photopolymerization initiator, and 0.08 parts by mass of a benzotriazole-based ultraviolet absorber (manufactured by BSF, product name "TINUVIN 384-2") as an ultraviolet absorber, were added, and the mixture was heated and mixed at 80°C to obtain a composition for light diffusion control layer.

[0099] (2) Formation of Light Diffusion Control Layer The obtained composition for light diffusion control layer was applied to the release-treated surface of a release sheet R1 (thickness: 188 μm) as a process sheet, which was a long polyethylene terephthalate sheet with one side treated with a silicone-based release agent, to form a coating film with a thickness of 110 μm. Subsequently, the release-treated surface of a release sheet R2 (thickness: 38 μm) of a polyethylene terephthalate film with one side treated with a silicone-based release agent was laminated on the surface of the coating film opposite to the process sheet.

[0100] The resulting laminate consisting of the release sheet R2, the coating film, and the process sheet was placed on a conveyor. The release sheet R2-side surface of the laminate was facing upward, and the longitudinal direction of the laminate was parallel to the conveyor flow direction. A parallel ultraviolet spot light source (manufactured by JATEC) with a central beam parallelism controlled to within ±3° was then installed relative to the conveyor on which the laminate was placed. The light source was positioned so that it could irradiate parallel light in a direction inclined by 5° toward the conveyor flow direction with respect to the normal direction of the coating film-side surface of the laminate.

[0101] Thereafter, the conveyor was operated to move the laminate while applying a peak irradiance of 1.02 mW / cm on the coating surface. ２ , cumulative light intensity 26.35 mJ / cm ２The coating film in the laminate was cured by irradiating it with parallel light (ultraviolet light from a high-pressure mercury lamp having a main peak wavelength of 365 nm, with other peaks at 254 nm, 303 nm, and 313 nm) with a parallelism of 2° or less under the conditions of (a) to (c) to form a light diffusion control layer having a thickness of 110 μm. As a result, a laminate was obtained in which the process sheet, the light diffusion control layer (thickness: 110 μm), and the release sheet R2 were laminated in this order.

[0102] Microscopic observation of the cross section of the formed light diffusion control layer confirmed that a columnar structure consisting of multiple columns standing tall throughout the thickness direction was formed within the light diffusion control layer. That is, the proportion of the columnar structure region extending in the thickness direction within the obtained light diffusion control layer was 100%. Furthermore, when the light diffusion control layer was examined in direction C in FIG. 3 , it was found that, when the UV-irradiated surface was facing upward, the conveyor traveling direction (MD direction) and direction C coincided. Furthermore, it was confirmed that the columns were bent midway along their extension direction. Furthermore, it was confirmed that the angle (angle a in FIG. 3 ) between the extension direction (direction A in FIG. 3 ) of the portion of the column closer to the UV-irradiated surface than the bent portion and the thickness direction of the light diffusion control layer (direction B in FIG. 3 ) was 3.2°. In this specification, the angle is expressed as a positive value when the A direction is inclined toward the conveyor travel direction (MD direction) with respect to the B direction, and as a negative value when the A direction is inclined toward the opposite side of the conveyor travel direction.

[0103] The peak irradiance and the integrated light amount were measured by placing a UV meter equipped with a light receiver (manufactured by Eye Graphics, product name "Eye Ultraviolet Integrated Illuminance Meter UVPF-A1") at the position of the coating film. The thickness of the light diffusion control layer A was measured using a constant pressure thickness meter (manufactured by Takara Seisakusho, product name "TECLOCK PG-02J").

[0104] (3) Formation of Pressure-Sensitive Adhesive Layer 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid were copolymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight-average molecular weight (Mw) of the (meth)acrylic acid ester polymer was measured and found to be 400,000.

[0105] 100 parts by mass of the obtained (meth)acrylic acid ester polymer and 0.025 parts by mass of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane as a crosslinking agent were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of a pressure-sensitive adhesive composition.

[0106] The obtained coating solution was applied using a knife coater to the release-treated surface of a heavy-release type release sheet R3 (thickness: 38 μm), one side of which was a polyethylene terephthalate film treated with a silicone-based release agent, and then dried by heating in a drying oven at 90°C for 1 minute to obtain a coating layer with a thickness of 15 μm.

[0107] Next, the release-treated surface of a light-release type release sheet R4 (thickness: 38 μm), which was a polyethylene terephthalate film with one side treated with a silicone-based release agent, was attached to the surface of the coating layer opposite to the release sheet R3, and then the coating layer was cured for 7 days under conditions of 23°C and 50% RH to form a pressure-sensitive adhesive layer.

[0108] As a result, a laminate was obtained in which release sheet R3, a 15 μm thick adhesive layer, and release sheet R4 were laminated in that order. It was confirmed that the release strength of release sheet R3 in this laminate was greater than that of release sheet R4.

[0109] (4) Preparation of a Reflective Display Sample The release sheet R2 was peeled off from the laminate obtained in the above step (2) to expose the light diffusion control layer. Subsequently, the release sheet R4 was peeled off from the laminate obtained in the above step (3) to bond the exposed surface of the pressure-sensitive adhesive layer to the exposed surface of the light diffusion control layer.

[0110] Further, the release sheet R3 was peeled off, and the exposed surface of the adhesive layer was attached to one side of a reflective electrode (manufactured by Pictleap Co., Ltd., product name "PIC0401") as a diffuse reflector.

[0111] This produced a reflective display sample in which the process sheet, the light diffusion control layer, the adhesive layer, and the diffusion reflector were laminated in this order.

[0112] [Example 2] A reflective display sample was obtained in the same manner as in Example 1, except that the thickness of the light diffusion control layer was formed to be 60 μm. When the cross section of the light diffusion control layer (thickness: 60 μm) was observed under a microscope, the internal structure was found to be the same as that of the light diffusion control layer formed in Example 1.

[0113] Example 3 (1) Formation of Light Diffusion Control Layer A composition for a light diffusion control layer was obtained in the same manner as in step (1) of Example 1. The obtained composition for a light diffusion control layer was then applied to the release-treated surface of a release sheet R1 (thickness: 188 μm) as a process sheet to form a coating film with a thickness of 200 μm. The resulting laminate consisting of the coating film and the process sheet was placed on a conveyor. At this time, the coating surface of the laminate was facing upward, and the longitudinal direction of the laminate was parallel to the flow direction of the conveyor.

[0114] A parallel ultraviolet spot light source (manufactured by JATEC Co., Ltd.) with a central beam parallelism controlled to within ±3° was placed in front of the conveyor on which the laminate was placed, and the light source was installed so as to irradiate parallel light in a direction inclined by 10° in the conveyor flow direction with respect to the normal direction of the surface of the laminate facing the coating film.

[0115] Thereafter, the conveyor was operated to move the laminate while applying a peak irradiance of 1.06 mW / cm2 to the coating surface. ２ , cumulative light intensity 28.76 mJ / cm ２ Under the conditions above, parallel light (ultraviolet rays from a high-pressure mercury lamp having a main peak wavelength of 365 nm, with other peaks at 254 nm, 303 nm, and 313 nm) with a parallelism of 2° or less was irradiated (first stage irradiation).

[0116] Next, the release-treated surface of release sheet R5 (thickness: 38 μm), which was a polyethylene terephthalate film with one side treated with a silicone-based release agent, was laminated onto the exposed surface of the coating layer.

[0117] A parallel ultraviolet spot light source (manufactured by JATEC Co., Ltd.) with a central beam parallelism controlled to within ±3° was placed in front of the conveyor on which the laminate was placed, so that the light source could irradiate parallel light in a direction inclined by 0° in the conveyor flow direction with respect to the normal direction of the surface of the laminate facing the coating film.

[0118] Then, the conveyor was operated to move the laminate, and the peak irradiance on the coating surface was measured through the release film at 2.54 mW / cm. ２ , cumulative light intensity 46.76 mJ / cm ２ Under the conditions above, parallel light (ultraviolet rays from a high-pressure mercury lamp having a main peak wavelength of 365 nm, with other peaks at 254 nm, 303 nm, and 313 nm) with a parallelism of 2° or less was irradiated (second-stage irradiation).

[0119] This resulted in a light diffusion control layer having a thickness of 200 μm. As a result, a laminate was obtained in which the process sheet, the light diffusion control layer (thickness: 200 μm), and the release sheet R5 were laminated in this order.

[0120] Microscopic observation of the cross section of the formed light diffusion control layer confirmed that a columnar structure consisting of multiple columns standing throughout the thickness direction was formed within the light diffusion control layer in a two-layer stack. When the two layers were considered together, the proportion of the columnar structure region extending in the thickness direction within the light diffusion control layer was 100%. The structure of these two layers was similar to that shown in Figure 2(b). Specifically, in the layer on the UV-irradiated side (sometimes referred to as the "first layer"), the columns were found to stand nearly parallel to the thickness direction of the light diffusion control layer (i.e., nearly perpendicular to the main surface of the light diffusion control layer). In contrast, in the other layer (sometimes referred to as the "second layer"), the columns were found to be inclined with respect to the thickness direction of the light diffusion control layer and bent midway along their extension direction. When the second layer was examined in direction C in Figure 3, it was found that, when the UV-irradiated side was facing upward, direction C coincided with the conveyor traveling direction (MD direction). Furthermore, it was confirmed that the angle (angle a in Figure 3) formed between the extension direction (direction A in Figure 3) in the part of the second layer closer to the ultraviolet irradiated surface than the bent part and the thickness direction of the light diffusion control layer (direction B in Figure 3) was 6.4°.

[0121] (2) Preparation of Reflective Display Samples A reflective display sample was prepared in the same manner as in Example 1, except that the laminate obtained in the above step (1) was used.

[0122] Comparative Example 1 A reflective electrode (manufactured by Pictleap, product name "PIC0401") was prepared as a diffuse reflector, and this diffuse reflector alone was used as a reflective display sample according to Comparative Example 1.

[0123] Comparative Example 2 A light diffusion control layer was prepared in the same manner as in Example 1, and this light diffusion control layer alone was used as a reflective display sample according to Comparative Example 2.

[0124] Comparative Example 3: 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid were copolymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight average molecular weight (Mw) of the (meth)acrylic acid ester polymer was measured and found to be 400,000.

[0125] 100 parts by mass of the obtained (meth)acrylic acid ester polymer, 0.025 parts by mass of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane as a crosslinking agent, and 15 parts by mass of silicone particles (manufactured by Momentive Corporation; product name "Tospearl 145") were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of a pressure-sensitive adhesive composition.

[0126] The resulting coating solution was applied to the release-treated surface of release sheet R3 using a knife coater, and then dried by heating at 90° C. for 1 minute in a drying oven to obtain a coating layer with a thickness of 15 μm.

[0127] Next, the release-treated surface of release sheet R4 was attached to the surface of the coating layer opposite to release sheet R3, and the coating layer was then cured for 7 days under conditions of 23°C and 50% RH to form a microparticle-dispersed diffusive adhesive layer.

[0128] A reflective display sample was obtained in the same manner as in Example 1, except that the obtained fine particle-dispersed diffusive pressure-sensitive adhesive layer was used instead of the light diffusion control layer.

[0129] Test Example 1 (Measurement of Brightness of Reflective Display Body) (1) Measurement of Brightness in the Front Direction For the reflective display body samples manufactured in the Examples and Comparative Examples, a point on the surface (irradiated surface) on the light diffusion control member side was assumed as the irradiation point (point 201 in FIG. 4(b)) and four directions were assumed with azimuth angles of 0°, 90°, 180°, and 270° from the irradiation point as the center, as shown in FIG. 3. In this case, the direction C in FIG. 3 of the light diffusion control layer in the reflective display body sample was set to coincide with the azimuth angle of 270°.

[0130] Next, the reflective display sample 200 was placed in a conoscope (manufactured by Autronic Melcher), and in reflection mode, a light beam was irradiated from a direction at an azimuth angle of 0° relative to the irradiation point, and the luminance distribution of the diffusely reflected light was measured. At this time, the angle between the light beam 202 and the normal to the surface of the reflective display sample 200 was 30°, as shown in Figure 4(c).

[0131] Then, a light beam was irradiated onto the reflective display sample for each of the four azimuth angles, and the luminance distribution of the diffusely reflected light was measured. From the luminance distributions obtained for the four azimuth angles, the luminance (cd / m) of the reflected light (the light beam indicated by the reference symbol 203 in FIG. 5(a)) reflected in the front direction (the direction parallel to the normal to one surface of the reflective display sample) was calculated. ２ The results are shown in Table 2.

[0132] The maximum of the four obtained luminance values ​​is designated as L ｍａｘ The smallest one is L ｍｉｎ At the same time, L ｍａｘ L for ｍｉｎ The ratio (L ｍｉｎ / L ｍａｘ ) were calculated. These results are also shown in Table 2.

[0133] (2) Calculation of Standard Deviation In the same manner as in step (1) above, a light beam was irradiated onto the reflective display sample for each of the four azimuth angles, and the luminance distribution of the diffusely reflected light was measured. As shown in FIG. 5(b), a plane (plane P in FIG. 5(b)) was assumed, which included the irradiation point 201 and the normal to the irradiated surface, and was perpendicular to an azimuth angle of 0° (i.e., parallel to azimuth angles of 90° and 270°). The luminance of the reflected light traveling within this plane and making an angle of 30° or less with the normal to the irradiated surface was read from the luminance distribution, and the standard deviation (cd / m) of the luminance for an azimuth angle of 0° was calculated. ２ The results are shown in Table 2.

[0134] Furthermore, when light is irradiated from azimuth angles of 90°, 180°, and 270°, a flat surface is assumed in the same manner as above, and the standard deviation of luminance (cd / m) for azimuth angles of 90°, 180°, and 270° is calculated. ２ ) was calculated. The average value (cd / m ２ The results are shown in Table 2.

[0135] [Test Example 2] (Evaluation of Visibility) The reflective display samples produced in the Examples and Comparative Examples were visually evaluated for visibility under fluorescent lighting based on the following three criteria. The evaluation results are shown in Table 3.

[0136] (1) Brightness in the front direction: ◎: Very bright. ○: Bright. △: Somewhat dark, but still acceptable brightness. ×: Unacceptably dark.

[0137] (2) Uniformity of brightness when the vertical direction is changed ◎: When the vertical direction is changed, the difference in brightness is barely noticeable. ○: When the vertical direction is changed, there is a slight difference in brightness, but it is fully acceptable. ×: When the vertical direction is changed, there is a clear difference in brightness to an unacceptable extent.

[0138] (3) Unevenness in brightness when the viewing angle is changed within a viewing angle of 30°. Excellent: Almost no unevenness was noticeable. Good: There was some unevenness, but it was quite acceptable. Bad: The unevenness was clearly noticeable to an unacceptable extent.

[0139]

[0140]

[0141]

[0142] As can be seen from Table 3, the reflective display samples obtained in the examples were visible with sufficient and uniform brightness even when the display orientation was changed. Furthermore, even when the viewing angle was changed within a viewing angle of 30°, there was no unevenness in brightness and the display was easily visible.

[0143] The light diffusion control member of the present invention is suitably used in the manufacture of displays such as smartphones and tablets that are configured so that the up-down direction of the displayed content can be changed.

[0144] REFERENCE SIGNS LIST 1 reflective display body 11 light diffusion control layer 111 relatively high refractive index region (columnar object) 112 relatively low refractive index region 12 display device 13 diffusion reflector 1' reflective display body sample 201 irradiation point 202 light ray 203, 204a, 204b reflected light

Claims

1. A reflective display comprising a light diffusion control layer having a regular internal structure with multiple regions with a relatively high refractive index within a region with a relatively low refractive index; a display device laminated on one side of the light diffusion control layer; and a diffusion reflector laminated on the side of the display device opposite the light diffusion control layer and having a reflective surface on the surface facing the display device, wherein the diffusion reflector has an uneven structure on the reflective surface, and when a light beam making an angle of 30° with the normal to the surface is irradiated to an arbitrary point on the surface facing the light diffusion control layer of the reflective display from four directions with azimuth angles of 0°, 90°, 180°, and 270° centered on the point, and reflected light diffusely reflected from the point is generated for each of the azimuth angles, When the standard deviation of the luminance of the reflected light that travels in a plane that includes the one point and the normal line and is perpendicular to the azimuth angle at which the light ray is irradiated and that forms an angle of 30° or less with the normal line is calculated for each of the four directions, the average value of the four standard deviations is 0.25 cd / m ２ A reflective display device characterized in that the reflection angle is less than 100°.

2. The reflective display device of claim 1, characterized in that the region of relatively high refractive index is a columnar object extending from one side of the light diffusion control layer to the other side, the light diffusion control layer has at least one layer having a column structure in which the columns stand in a forest in the region of relatively low refractive index, and in at least some of the columns, a straight line parallel to the direction of extension is inclined with respect to the thickness direction of the light diffusion control member.

3. The reflective display device according to claim 1, wherein the diffusion reflector is a reflective electrode.

4. When a light beam that forms an angle of 30° with respect to the normal line of the surface of the reflective display device is irradiated from four directions of azimuth angles of 0°, 90°, 180°, and 270° with the point as the center to any one point on the surface of the reflective display device, and light that is diffusely reflected from the point is generated for each of the azimuth angles, the luminance (cd / m2) of the reflected light that is reflected in a direction perpendicular to the surface is calculated. ２ ) is measured in each of the four directions, and the maximum luminance among them is L ｍａｘ The minimum luminance is L ｍｉｎ In this case, the L ｍａｘ and the L ｍｉｎ However, 0.6≦L ｍｉｎ / L ｍａｘ 2. The reflective display according to claim 1, wherein the following relationship is satisfied: ##EQU1## 5. The reflective display according to claim 1, characterized in that the display content is configured so that its up-down direction can be changed.

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