JP2019020483A - Screen for display and method for manufacturing the same - Google Patents

Abstract

To prevent, in a transmission type screen including a microlens array, overheating of a light-shielding part from causing overheating of the entire screen.SOLUTION: A transmission type screen includes a microlens array, and further includes an aperture array arranged on a surface on the opposite side of a surface on which the microlens array is arranged. A light-shielding part of the aperture array is a metal film, and the metal film has a thickness of 50 nm or more and 200 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a display screen and a method for manufacturing the same, and more particularly to a transmissive screen.

In order to improve the contrast of a liquid crystal display, a plasma display, and a rear projection television, a technique for hiding a portion on the screen sheet that does not transmit image light is disclosed. Due to the concealment, it is possible to prevent external light such as sunlight that causes deterioration of visibility such as glare from entering the apparatus.
For example, Patent Document 1 discloses a method of concealing a portion through which image light is not transmitted, a method in which a black stripe sheet in which a black groove is filled with black ink in advance is used and overlapped with a screen sheet. Patent Document 2 discloses a method of using a material that changes to a non-adhesive substance by irradiating ultraviolet rays in order to simplify the alignment of the screen sheet and the black stripe sheet. In this method, it is necessary to irradiate ultraviolet rays from the screen sheet side to the adhesive sheet side, change the adhesive material of the part through which the image light is transmitted to non-adhesive, and paste and peel off the black sheet from above. The method of filling only the part with black material is adopted.

JP 2006-184609 A JP 2001-113538 A

In the method of Patent Document 1, the alignment tolerance between the two sheets is strict, and the image light is likely to be blocked by the light shielding portion, and the image may become dark. Further, in the method of Patent Document 2, when the screen lens pitch is reduced to several tens of μm in order to increase the resolution of the display, the black sheet can be separated at the boundary between the adhesive and non-adhesive when the black sheet is peeled off. Instead, it may remain in the transmission part of the image light.
Further, when a black material is used for the light shielding part, the light shielding part absorbs external light such as sunlight and is overheated. Therefore, the screen having the black material may be deformed by overheating.

  This invention is made | formed in view of such a situation, and it aims at providing the display screen which can suppress the overheating by external light, and its manufacturing method.

[1] A transmissive screen including a microlens array,
An aperture array disposed on a surface opposite to the surface on which the microlens array is disposed;
The light shielding portion of the aperture array is a metal film,
The metal film has a thickness of 50 nm or more and 200 nm or less,
screen.
[2] The screen according to claim 1, wherein the surface of the metal film has a reflectance of light having a wavelength of 380 nm to 780 nm of 80% or more.
[3] The screen according to [1] or [2], wherein the metal film has a surface roughness of 0.1 μm or less.
[4] The screen according to any one of [1] to [3], further comprising a protective layer on the metal film.
[5] A method of manufacturing a transmissive screen including an aperture array disposed on a surface opposite to a surface on which a microlens array is disposed,
When forming the aperture array on the surface opposite to the surface where the microlens array of the transparent substrate is arranged,
A negative resist is applied to the surface opposite to the surface on which the microlens array of the transparent substrate is disposed,
Irradiate exposure light from the microlens array side toward the transparent substrate,
Exposing the negative resist with the exposure light, further developing to form a resist pattern,
A metal film having a thickness of 50 nm or more and 200 nm or less is formed on the surface of the transparent substrate on which the resist pattern is formed,
Forming an opening array having a light-shielding portion made of the metal film by removing the resist pattern;
Screen manufacturing method.
[6] A method for manufacturing a transmission screen comprising an aperture array disposed on a surface opposite to a surface on which a microlens array is disposed,
When forming the aperture array on the surface opposite to the surface where the microlens array of the transparent substrate is arranged,
A metal film having a thickness of 50 nm or more and 200 nm or less is formed on the surface of the transparent substrate opposite to the surface on which the microlens array is disposed,
Forming an opening array having a light shielding portion made of the metal film by removing a part of the metal film;
Screen manufacturing method.
[7] The method for manufacturing a screen according to [5] or [6], wherein a protective layer is formed on the metal film after the opening array is formed.

  ADVANTAGE OF THE INVENTION According to this invention, the screen for a display which can suppress the overheating by external light, and its manufacturing method can be provided.

It is sectional drawing of a screen. It is a picked-up image of an aperture array. It is a schematic diagram of the optical system of a head-up display. It is a schematic diagram of application | coating of a resist. It is a schematic diagram of exposure of a resist. It is a schematic diagram of formation of a metal film. It is a schematic diagram of the incident light to a screen. It is a schematic diagram of exposure of a resist. It is a schematic diagram of formation of a metal film. It is a graph which shows the correlation with a vapor deposition angle and the light shielding rate of an opening array. It is a graph which shows the correlation with a vapor deposition angle and an exposure rate. It is a schematic diagram of the apparatus which evaluates a reflective characteristic. It is a graph which shows the relationship between a metal film thickness and diffused reflected light. It is a graph which shows the relationship between a metal film thickness and the transmittance | permeability. It is a graph which shows the measurement result of the diffuse reflection light of the screen of an Example and a comparative example. It is sectional drawing of a screen.

[screen]
FIG. 1 shows a cross-sectional view of a transmissive screen 20. The screen 20 includes a microlens array 21 and an aperture array 24. The aperture array 24 is disposed on the surface opposite to the surface on which the microlens array 21 is disposed. The microlens array 21 and the aperture array 24 are disposed on a transparent substrate 28 made of resin.

  The screen 20 shown in FIG. At this time, the individual microlenses 22 included in the microlens array 21 cause diffusion 32 of the image light 31. Therefore, the screen 20 functions as an optical screen because the direction of the optical axis of the image light 31 is dispersed. Further, the microlens 22 can be designed to have a desired diffusion angle in the diffusion 32. You may define as a full angle the position which becomes the half value of the center brightness | luminance of the image light 31 which spread | diffused the diffusion angle. The microlens 22 has a convex surface that projects outward from the screen 20, that is, downward in the drawing.

  The opening array 24 shown in FIG. 1 includes a light shielding part 25 and an opening part 26. Therefore, the image light 31 diffused as described above finally passes through the screen 20 via the opening 26. In other words, the light shielding portion 25 is preferably provided only in a portion other than the portion through which the image light 31 is transmitted.

  The inner diameter of the opening 26 shown in FIG. 1 is preferably equal to or larger than the diameter of the spread of the image light 31 on the cross section of the image light 31 in the opening 26. For example, a head-up display with a screen 20 is designed as such. In this manner, the image light 31 reflected from the inner surface 29 of the light shielding unit 25 can be reduced. The inner surface 29 is a surface that the light shielding unit 25 has and is a surface that is located on the top surface side of the transparent substrate 28. That is, the surface opposite to the outer surface 27.

  FIG. 2 is an image obtained by photographing one of the examples of the aperture array 24. As shown in the photographed image, the openings 26 are arranged in a lattice pattern on the opening array 24. The opening 26 is surrounded by the light shielding portion 25. The light shielding part 25 is a metal film. The metal film is preferably a film formed by any of vapor deposition, sputtering and electroforming. The metal film is preferably a deposited film.

The thickness of the metal film is 50 nm or more and 200 nm or less. The thickness of the metal film will be described with reference to FIGS. In this embodiment, since the metal film is a thin film having a matrix structure, when external light is incident on the metal film, it becomes diffracted light in the matrix.
As shown in FIG. 13, diffracted light detected as diffusely reflected light can be reduced by thinning the metal film. In the present embodiment, the thickness of the metal film is 200 nm or less. Thus, a screen in which the diffuse reflection light is suppressed can be obtained. On the other hand, as shown in FIG. 14, when the metal film is thinned, external light may pass through the metal film itself and the reflection effect of the metal film may be reduced. In the present embodiment, the reflectance of the metal film is improved by setting the thickness of the metal film to 50 nm or more, and external light such as sunlight that causes deterioration of visibility such as glare is caused by shielding the metal film. Light entering the apparatus can be suppressed, and a screen with excellent contrast can be obtained. The lower limit of the thickness of the metal film is preferably 50 nm or more, more preferably 70 nm or more, and still more preferably 100 nm or more.
Moreover, it is preferable that the surface roughness of a metal film is 0.1 micrometer or less by arithmetic mean roughness Ra prescribed | regulated to JISB0601: 2013.

  Returning to FIG. It is preferable that the outer surface 27 of the metal film constituting the light shielding portion 25 has a mirror surface. In the light shielding part 25, the outer surface 27 is a surface far from the microlens array 21. On the outer surface 27, the reflectance of light having a wavelength of 380 nm to 780 nm is preferably 80% or more, more preferably 83% or more, and further preferably 87% or more.

  The reflectance of the outer surface 27 shown in FIG. 1 is, for example, a metal film produced in the same manner as the light shielding portion 25 and having no opening, and light is reflected by a spectrophotometer. It is obtained from the value when the thickness is measured. In this measurement, the incident light is preferably incident on the outer surface 27 at an angle of 10 degrees with respect to the normal line of the outer surface 27. For example, U-4100 made by Hitachi High-Tech Science may be used as the spectrophotometer.

As shown in FIG. 16, the screen 20 of this embodiment may further include a protective layer 49 on the metal film 24. By having a protective layer, damage and oxidation of the metal film can be suppressed.
The protective layer 49 only needs to have transparency, and can be appropriately selected from known resins used for optical films and the like. The protective layer 49 may consist of only one layer or may have a laminated structure of two or more layers. As the laminated structure, for example, a laminated structure having an adhesive layer and a reinforcing plate on a metal film in this order is preferable. This is because the adhesive layer fills the opening of the metal film to improve the protection of the metal film, and the rigid reinforcing plate improves the mechanical strength of the screen, resulting in a screen with excellent handling properties. .
The resin constituting the adhesive layer is not particularly limited, and examples thereof include acrylic adhesives, urethane adhesives, and epoxy adhesives. Moreover, a reinforcement board is not specifically limited, For example, a triacetylcellulose (TAC) film, a polyethylene terephthalate (PET) film, a polycarbonate film etc. are mentioned.
In the case of a laminated structure, the intensity of the diffused light can be lowered by providing a refractive index difference in each layer. Suitable combinations include, for example, a combination of an acrylic adhesive having a refractive index of around 1.50 as the adhesive layer and a polycarbonate film having a refractive index of around 1.60 as the reinforcing plate.

[Head-up display]
FIG. 3 shows an optical system 30 of a head-up display. Such a head-up display includes a screen 20. The screen 20 constitutes a part of the optical system 30.

  In FIG. 3, video light 31 represented by a solid line is projected onto the screen 20 from the microlens array 21 side. The image light 31 is generated by, for example, PGU (Picture Generation Unit). The image light 31 is guided to the screen 20 by the projection optical system.

  Video light 31 shown in FIG. 3 is diffused by the microlens array 21. The image light 31 passes through the screen 20. The image light 31 is emitted from the screen 20 as diffused light and is reflected by the concave mirror 35. Thereafter, the video light 31 is presented as a virtual image to an observer who views the head-up display.

  As shown in FIG. 3, the screen 20 includes a microlens array 21. For this reason, the diffusion angle and efficiency of the screen 20 can be easily controlled by the microlens array 21. Further, by using the microlens array 21, the image presented by the video light 31 can be adjusted to an angle of view that is easy for an observer to visually recognize.

  Consider a case where a head-up display is mounted on a vehicle and the vehicle is placed outdoors. In this case, sunlight may enter the optical system 30 shown in FIG. In FIG. 3, external light 34 represented by a broken line is reflected by the concave mirror 35. The external light 34 may reach the screen 20 after reflection.

  When the screen 20 shown in FIG. 3 is arranged on a plane perpendicular to the optical axis of the image light 31, the external light 34 that has entered from the opposite direction to the image light 31 is reflected by the screen 20. Specifically, the light is reflected by the microlens array 21 or the aperture array 24. At this time, since the optical axis of the video light 31 and the optical axis of the external light 34 are parallel, the external light 34 may be mixed with the video light 31.

  When the external light 34 is mixed with the video light 31 shown in FIG. 3, the image presented by the video light 31 is whitened. Therefore, the contrast of the image is lowered. For an observer, for example, a driver of a vehicle, not only the visibility of the image is deteriorated, but also a dazzling part is visually recognized in the image. Such a problem is not limited to the case where the external light 34 is sunlight. The same problem occurs even when the head-up display is not mounted on the vehicle.

  In the present embodiment, as shown in FIG. 3, the screen 20 is inclined so that the optical axis of the image light 31 emitted from the opening 26 and the optical axis of the external light 34 reflected by the light shielding unit 25 are not parallel. is there. The screen 20 is tilted so that the screen 20 is inclined with respect to the optical axis of the image light 31 projected on the screen 20 from the microlens array 21 side. Thereby, the incoming external light 34 can escape in a direction different from the optical axis of the image light 31. Accordingly, since the external light 34 is not easily mixed with the video light 31, whitening of the image is suppressed.

  As shown in FIG. 3, the head-up display of this embodiment further includes a light absorption unit 36. The light absorption unit 36 receives external light 34 reflected by the light shielding unit 25. The light absorption part 36 is subjected to black coating, anodizing, or the like. The light absorption unit 36 absorbs external light 34. For this reason, the external light 34 is suppressed from becoming stray light in the optical system 30.

  As described in the background art, the contrast of an image can be increased even when a black matrix such as a black resist is used as an alternative to the light shielding portion 25. However, since the external light 34 shown in FIG. 3 is collected on the screen by the concave mirror 35, the energy of the external light 34 is efficiently absorbed by the black matrix. Therefore, the screen tends to overheat with the black matrix.

  If the screen is made of a transparent substrate made of resin, there is a possibility that the screen is deformed or ignited. For this reason, in a head-up display, an absorption type contrast improving means such as a black matrix is not suitable for the screen. Such a problem is not limited to the case where the external light 34 is sunlight. The same problem occurs even when the head-up display is not mounted on the vehicle.

  On the other hand, in this embodiment, as shown in FIG. 3, the external light 34 that has reached the screen 20 can be released to the light absorber 36. This is because the screen 20 is provided with a light shielding portion 25 made of a metal film. The light shielding unit 25 reflects the external light 34 by regular reflection. For this reason, since the light shielding part 25 is hard to overheat, the screen 20 is also hard to overheat.

[Method for forming microlens array]
The microlens array 21 shown in FIG. 1 can be formed as a sheet according to a known method. The mold used for forming the microlens array sheet may be formed by cutting. Alternatively, a mold may be formed by photolithography, and a mold may be formed based on the mold. The mold may be produced by laser ablation. Any mold can be used as long as it can withstand the molding of the microlens array sheet.

  In the molding of the microlens array 21 shown in FIG. 1, means suitable for molding a resin sheet, such as injection molding, press molding, and molding by ultraviolet curing, can be widely used. Further, a sheet obtained by molding may be attached to the transparent substrate 28. Moreover, you may shape | mold resin arrange | positioned on the transparent base material 28. FIG.

[Method for forming aperture array]
On the other hand, it is necessary to pay attention to the following when forming the aperture array. That is, as shown in FIG. 3, the aperture array 24 blocks outside light 34 but does not block image light 31. Therefore, it is necessary to accurately form an aperture array pattern on the transparent substrate 28 based on the arrangement of the microlenses 22 in the microlens array 21.

  As an embodiment of the pattern forming method of the aperture array, a metal film having a thickness of 50 nm or more and 200 nm or less is formed on the surface of the transparent substrate opposite to the surface on which the microlens array is arranged, and the metal There is a method of forming an aperture array having a light shielding portion made of the metal film by removing a part of the film. In this embodiment, since the metal film is a relatively thin film with a thickness of 50 nm or more and 200 nm or less, even a light shielding portion formed by this method blocks external light and efficiently transmits image light. The screen to be obtained is obtained.

  However, in the present embodiment, it is preferable to use self-alignment exposure as a pattern forming method. In the self-alignment exposure, the photoresist is exposed using the condensing function of the microlens array 21 itself shown in FIGS. When using self-alignment exposure, it is preferable to combine a lift-off method in order to form the opening 26 by selectively removing an unnecessary metal film.

  A method for forming an aperture array on the transparent substrate 28 will be described with reference to FIGS. FIG. 4 is a schematic diagram of resist application. The microlens array 21 is formed on one surface of the transparent substrate 28, that is, the bottom surface 38. A resist 41 is applied to the top surface 39 of the transparent substrate 28. The top surface 39 is a surface opposite to the bottom surface 38. The resist 41 is a negative resist. The resist 41 is preferably a photosensitive resin.

  As a method of applying the resist 41 to the top surface 39 shown in FIG. 4, spin coating, die coating, spray coating, roll coating, or the like can be used. Further, drying is performed to volatilize the solvent of the applied resist 41. For drying, a hot plate, an oven, a vacuum dryer, an infrared heater, or the like can be used. As a method of not applying and drying, a method of laminating a film resist can be taken.

  FIG. 5 is a schematic view of resist exposure. Exposure light 44 is irradiated from the microlens array 21 side toward the transparent substrate 28. The exposure light 44 is preferably ultraviolet light. The exposure light 44 is collected by each microlens of the microlens array 21. The resist 41 is exposed with the exposure light 44. At this time, when a plurality of types of microlenses of the microlens array 21 are included, the aperture diameter may change according to the focal length and the diffusion angle of the microlens.

  As the exposure light 44 shown in FIG. 5, light including a wavelength capable of exposing the resist 41 can be used. The light source of the exposure light 44 is preferably a light source that can emit light having substantially the same projection angle and pupil diameter as the image light 31 shown in FIG. The light source of the exposure light 44 is preferably a light source having a small viewing angle.

  Performing self-alignment exposure as described above is suitable for allowing exposure light to pass through substantially the same optical path as the image light 31 as shown in FIG. That is, if the image light is irradiated onto the resist 41 shown in FIG. 4, it is suitable for exposing only a part of the resist 41 that is considered to transmit the image light. This portion of the resist 41 changes to an exposed resist 42 shown in FIG.

  FIG. 6 shows a process of forming the metal film 43. Before forming the metal film 43, the resist 41 and the resist to be exposed 42 shown in FIG. 5 are developed. At the time of development, the exposed resist is exposed to the developer together with the transparent base plate 28. As the developer, an alkali developer suitable for the material used for the resist 41 may be used. As the development method, an immersion method, a rocking method, a paddle method, a spray method, or the like can be used. After development, it is washed with pure water and dried.

  As described above, the unexposed portion of the resist 41 is removed. Thereafter, a resist pattern 45 shown in FIG. 6 is formed. A metal film 48 is formed on the top surface 39 on which the resist pattern 45 is formed. The formation of the metal film 48 may be performed by any one of vapor deposition, sputtering, and electroforming, but is not limited thereto.

  The resist pattern 45 shown in FIG. 6 is removed from the transparent substrate 28. By removing the resist pattern 45, an opening array 24 made of the metal film 48 (FIG. 6) is formed as shown in FIG. An opening 26 as shown in FIG. 2 is formed at the portion where the exposed resist 42 is removed. Thus, the screen 20 can be manufactured.

  The removal of the resist pattern 45 shown in FIG. 6 is preferably performed by lift-off. In the lift-off, it is preferable to bring the solvent into contact with the resist 42 to be exposed. Further, it is preferable to remove the resist pattern 45 by immersing the transparent substrate 28 together in the lift-off solution. The lift-off solution may be warmed to facilitate lift-off. In order to promote lift-off, the transparent substrate 28 may be vibrated.

  In the lift-off, the exposed portion of the resist 42 shown in FIG. 6 that is not covered with the metal film 48 and is exposed is required. From the above viewpoint, a vapor deposition method is suitable as a means for forming the metal film 48 shown in FIG. In the vapor deposition method, the metal particles go straight as the vapor flow 47. For this reason, the metal particles rarely wrap around the side surface of the exposed resist 42. Therefore, the side surface of the exposed resist 42 is not easily covered with the metal film 48.

[Effect of self-alignment exposure]
As shown in FIG. 7, the aperture array blocks light other than the portion through which the image light 31 passes. This is because the exposure light 44 shown in FIG. 5 passes through the site where the opening 26 through which the image light 31 shown in FIG. 7 passes should be formed by the self-alignment method. That is, the essential point of the resist pattern formation of the present embodiment is to provide the resist 42 to be exposed at the site where the opening 26 is to be formed by the self alignment method.

  In the present embodiment, a head-up display can be manufactured by producing a screen by the self-alignment method and disposing the screen in the head-up display.

  At this time, the screen 20 is arranged so that the image light 31 is projected onto the screen 20 from the microlens array 21 side shown in FIG. In the head-up display manufactured by such a method, the image light 31 is efficiently transmitted through the opening 26. This is because, by the self-alignment method, the opening 26 is accurately provided in advance at a position where the image light 31 should be transmitted.

  Furthermore, in the head-up display manufacturing method using the self-alignment method, at least one of the exposure light 44 shown in FIG. 5 and the image light 31 shown in FIG. 7 may be adjusted. Specifically, the image point distance Ex of the exposure light 44 shown in FIG. 5 and the image point distance Im of the video light 31 shown in FIG. 7 may be adjusted to be equal. Alternatively, the difference between these image point distances is preferably in the range of 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1%.

  As described above, the inner diameter of the opening 26 shown in FIG. 7 can be made substantially equal to the diameter of the spread of the image light 31 on the cross section in the opening 26. While reducing the image light 31 reflected by the inner surface 29 of the light shielding part 25, the efficiency of reflection of the external light 34 by the light shielding part 25 can also be increased.

  According to the above aspect, it is possible to balance the transmission efficiency of image light and the reflection efficiency of external light according to the design of the optical system of the head-up display shown in FIG. 3, that is, the optical system 30 shown in FIG. Therefore, according to the request based on the design of the head-up display, it is possible to adjust both the improvement of the transmission efficiency of the image light and the improvement of the contrast.

[Relationship between image point of microlens and lift-off]
Returning to FIG. The image point 50 is an image point of the exposure light 44 relating to the microlens included in the microlens array 21. The image point 50 is in front of the applied resist 41 with respect to the microlens. Although the image point 50 is in the transparent substrate 28 in the drawing, the image point 50 may be in the microlens array 21 in other embodiments.

  Here, the exposed resist 42 shown in FIG. 6 becomes thicker as the distance from the microlens array 21 increases. The exposed resist 42 has a so-called reverse taper shape. This is because, as shown in FIG. 5, when the exposure light 44 reaches the resist to be exposed 42, the exposure light 44 has already passed the image point 50, and the exposure light 44 is in the process of diverging.

  When the steam flow 47 shown in FIG. 6 is sprayed on the top surface 39 from one direction, the angle of the steam flow 47 with respect to the top surface 39 is not limited. This is because the side surface of the exposed resist 42 having a reverse taper shape is always shaded in any direction with respect to the vapor flow 47.

  Therefore, it is preferable that the direction of the vapor flow 47 impinging on the top surface 39 shown in FIG. 6 is not inclined with respect to the normal direction of the top surface 39. Further, the direction of the vapor flow 47 may be inclined from 0 ° to 20 °. The range of such inclination is preferably 0 ° to 10 °, more preferably 0 ° to 5 °. The smaller the inclination, the more efficiently the metal film 46 can be made thicker.

  The positional relationship between the image point 50 shown in FIG. 5 and the applied resist 41 can be arbitrarily adjusted. Such positional relationship can be adjusted, for example, by the thickness of at least one of the transparent substrate 28 and the base portion 19 of the microlens array 21. However, when the sum of these thicknesses increases and the image point distance Ex of the image point 50 does not change, the distance from the main surface of the microlens array 21 to the resist 41 becomes relatively large. In the figure, the image point distance Ex of the image point 50 also takes into account that the exposure light 44 is refracted at the interface between the microlens array 21 and the transparent substrate 28. The image point distance Im of the image light 31 shown in FIG.

  As described above, when the distance from the main surface of the microlens array 21 to the resist 41 is significantly larger than the image point distance Ex of the image point 50, each of the adjacent microlenses in the microlens array 21 has the same distance. The diffused exposure light 44 may overlap each other in the resist 41. In this case, most of the resist 41 is exposed. Accordingly, as shown in FIG. 2, the opening 26 surrounded by the light shielding portion 25 cannot be formed. For this reason, the aperture array 24 shown in FIG. 3 cannot reflect the external light 34 efficiently.

[When the resist is closer to the main surface of the microlens than the image point]
FIG. 8 shows another aspect of resist exposure. The exposure light 44 diffused by each microlens is partially omitted for convenience of explanation. When the total thickness of the transparent base material 28 and the base 19 becomes small and the image point distance Ex of the image point 50 does not change, the distance from the main surface of the microlens array 21 to the resist 41 becomes relatively small. In the drawing, the image point of the exposure light 44 relating to the microlens of the microlens array 21 is farther than the resist 41 with respect to the microlens. In FIG. 8, it is considered that the image point distance Ex of the image point 50 is that the exposure light 44 is refracted by the transparent substrate 28 and the resist 41.

  In the above case, the resist 42 to be exposed shown in FIG. 8 becomes tapered as the distance from the microlens array 21 increases. The exposed resist 42 has a so-called forward tapered shape. This is because, as shown in the figure, when the exposure light 44 reaches the resist to be exposed 42, the exposure light 44 has not yet passed the image point, and the exposure light 44 is in the process of convergence.

  In this case, a problem may occur in the lift-off described above. As shown in FIG. 8, when the exposed resist 42 has a forward taper, the resist pattern may not be lifted off. As shown in FIG. 9, when the vapor deposition is performed such that a vapor flow 47 perpendicular to the top surface 39 is sprayed, the resist 42 to be exposed is completely covered with the metal particles. This is due to the fact that there is no shadow portion on the side surface of the exposed resist 42 with respect to the vapor flow 47.

  In the above case, as shown in FIG. 9, by inclining the vapor flow like the vapor flow 51, the exposed portion of the side surface of the resist 42 to be exposed is not covered with the metal film 48. The magnitude of the inclination in the direction of the vapor flow 51 impinging on the top surface 39 is indicated by the vapor deposition angle Va with reference to the normal direction of the top surface 39. When the vapor deposition angle Va exceeds 60 °, the portion of the top surface 39 that is the shadow of the resist to be exposed 42 may become large. For this reason, a sufficient amount of metal to form the light shielding portion cannot be sent to the shaded portion.

  The graph of FIG. 10 shows the relationship between the deposition angle Va and the light shielding rate of the aperture array. The graph represents the light shielding rate of the aperture array when the deposition is performed while changing the deposition angle Va with respect to the top surface 39 shown in FIG. The exposed resist 42 has a substantially cylindrical shape with a diameter of 10 μm. The pitch of the openings in the opening array formed on the exposed resist 42 is 20 μm.

  The light shielding rate shown in FIG. 10 indicates the ratio of the area where the metal film is formed on the top surface 39 shown in FIG. The height of the exposed resist 42 is 1 μm or 5 μm. Compared with the height of 1 μm, the shadowed portion of the exposed resist 42 becomes larger in the case of the height of 5 μm. For this reason, when the height is 5 μm, the light blocking ratio is smaller than when the height is 1 μm. In the case where the height of the resist to be exposed 42 is 5 μm, the light shielding rate is drastically lowered when the deposition angle Va is larger than 60 °.

  The graph of FIG. 11 shows the relationship between the vapor deposition angle Va and the resist exposure rate. The resist exposure rate represents an exposure rate based on the area of the side surface of the exposed resist 42 shown in FIG. There is almost no difference in the exposure rate when the height of the exposed resist 42 is 1 μm and when it is 5 μm. By making the deposition angle Va larger than 0 °, the side surface of the resist 42 to be exposed can be exposed.

From the above, the deposition angle Va shown in FIG.
The thickness of the deposited film,
The size of the portion to be exposed on the side surface of the exposed resist 42;
The size of the portion of the top surface 39 that is not deposited behind the exposed resist 42;
Can be determined in a complementary manner.

  Based on the above policy, the deposition angle Va shown in FIG. 9 can be in the range of 20 ° to 60 °. The vapor deposition angle Va is preferably 45 °. With this deposition angle Va, lift-off can be efficiently performed by suppressing metal deposition on the side surface of the resist 42 to be exposed. Furthermore, it is possible to efficiently deposit metal on a portion of the top surface 39 where the light shielding portion is to be formed.

When a protective layer is further provided on the metal film, the method for forming the protective layer is not particularly limited, and a known method can be used according to the material of the protective layer.
For example, in the case of a laminated structure having an adhesive layer and a reinforcing plate in this order, which is preferable as a protective layer, first, the composition for forming an adhesive layer is, for example, vacuum deposition, vapor deposition, sputtering, spin A laminated structure can be formed as a protective layer by applying a coat, dip coat, bar coat or the like on a metal film and then bonding a reinforcing plate on the adhesive layer.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the transparent substrate 28 and the microlens array 21 shown in FIG. 1 may be molded as a seamless integral member.

Example 1
A microlens array sheet including the transparent substrate 28 and the microlens array 21 shown in FIG. 4 was formed. The microlens array 21 was formed on a transparent substrate 28 made of polycarbonate film using an ultraviolet curable resin. The thickness of the polycarbonate film was 100 μm. An acrylic resin was used as the ultraviolet curable resin. The irradiation amount of ultraviolet rays was 500 mJ / cm ² .

  As shown in FIG. 4, a resist 41 was applied to the back side of the microlens array sheet, that is, the top surface 39. Application was performed by a spin coating method. The rotational speed of the microlens array sheet, which is a workpiece, was adjusted so that the film thickness of the resist 41 was 5 μm. As the resist 41, PMER N-CA3000, which is a negative photoresist manufactured by Tokyo Ohka, was used. The resist 41 was dried in an oven at 70 ° C. for 20 minutes.

The microlens array sheet was placed on the stage of the UV exposure apparatus. At this time, the microlens array 21 shown in FIG. Ultraviolet rays were irradiated from the microlens array 21 side. The exposure amount was 500 mJ / cm ² . After the exposure, the microlens array sheet was subjected to a PEB (post exposure bake) treatment at 70 ° C. for 20 minutes in an oven.

  For development, the microlens array sheet was immersed in an organic alkali developer (TMAH 2.38%). The microlens array sheet was rocked for 3 minutes. The microlens array sheet taken out from the developer was washed with pure water and further dried.

A metal film 48 shown in FIG. 6 was formed by a vacuum evaporation apparatus. However, the vapor deposition angle was 45 °. The deposition source was aluminum, and the weight of the deposition source was 10.4 g. The distance between the deposition source and the workpiece was 450 mm. The vacuum degree of the vapor deposition tank was set to 2.0 × 10 ⁻² Pa. The deposition rate was 0.88 nm / sec and the deposited film thickness was about 70 nm. The lift-off was performed by immersing the microlens array sheet after vapor deposition in NMP (n-methyl-2-pyrrolidone). The microlens array sheet was rocked for 180 seconds. As a result, the exposed resist 42 was dissolved to form the opening array 24 shown in FIG. This obtained the screen of Example 1. The screen taken out from NMP was washed with pure water and then naturally dried.

(Example 2)
A screen of Example 2 was obtained in the same manner as in Example 1 except that the deposition rate during metal deposition was changed to 1.5 nm / sec and the thickness of the metal deposition film was changed to 120 nm.

(Comparative Example 1)
A screen of Comparative Example 1 was obtained in the same manner as in Example 1 except that the deposition rate during metal deposition was changed to 2.9 nm / sec and the thickness of the metal deposition film was changed to 230 nm.

  For each of the screens of the example and the comparative example, the reflection characteristics of the back side of the microphone lens array sheet, that is, the top surface 39 side shown in FIG. 7 were evaluated.

  FIG. 12 shows a schematic diagram of an apparatus for evaluating the reflection characteristics. This apparatus is a goniometer for measuring the intensity distribution of reflected light according to the reflection angle when the test screen 60 is irradiated with external light 64. The test screen 60 was placed on the black sheet 59 with the microlens array side down.

  As the external light 64 shown in FIG. 12, LED pseudo-parallel light having a spread angle of 5 ° or less was used. A light source 61 that emits such parallel light is disposed. A part of the external light 64 is diffusely reflected by the test screen 60 and becomes diffusely reflected light 65. Part of the external light 64 is specularly reflected by the test screen 60 and becomes specularly reflected light 66. The regular reflection light 66 is inclined + 10 °.

  The intensities of the diffuse reflected light 65 and the regular reflected light 66 shown in FIG. The reflection angle was changed by changing the observation angle Ob of the surface luminance meter 62 from −60 ° to + 60 °. When the surface luminance meter 62 faces the test screen 60, the observation angle Ob is set to 0 °.

  In this measurement, the mounting angle of the test screen 60 when the test screen 60 is installed in the head-up display is assumed to be 10 °. For this reason, the optical axis of the light source 61 and the optical axis of the surface luminance meter 62 when the observation angle Ob is 0 ° are shifted by −10 °.

FIG. 15 is a graph showing the correlation between the brightness of the diffuse reflected light and the observation angle. The unit of brightness of the diffuse reflected light is cd / m ² . The intensity of the specularly reflected light 66 (FIG. 12) to be observed when the observation angle Ob is + 10 ° exceeds the upper limit of the graph range.

  As shown in FIG. 15, in the screens of Examples 1 and 2, the intensity of the diffuse reflected light was smaller than that of the comparative example in the region of 0 ° or less. For this reason, it is considered that the internally reflected light generated by reflecting the external light reaching the microlens is shielded by the aperture array.

  As described above, in this measurement, the inclination angle when the screen is attached to the head-up display is 10 °. Therefore, strong specular reflection light is prevented from entering the observer's eyes.

  In the case of the screen of the comparative example, it was found that the observer can visually recognize a part of the internally reflected light generated by the microlens. Such internally reflected light reduces the image contrast. The comparison between the comparative example and the example shows that the improvement in the contrast of the image can be expected by suppressing the leakage of the internally reflected light by the opening array of the metal film of the present example.

19 base, 20 screen, 21 microlens array, 22 microlens, 24 aperture array, 25 light-shielding portion, 26 aperture, 27 outer surface, 28 transparent substrate, 29 inner surface, 30 optical system, 31 image light, 32 diffusion 34 External light, 35 Concave mirror, 36 Absorbing part, 38 Bottom surface, 39 Top surface, 41 Resist, 42 Exposed resist, 43 Metal film, 44 Exposure light, 45 Resist pattern, 46 Metal film, 47 Vapor flow, 48 Metal film , 49 protective layer, 50 image points, 51 vapor flow, 59 sheet, 60 test screen, 61 light source, 62 surface luminance meter, 64 external light, 65 diffuse reflection light, 66 specular reflection light, Ex exposure light image point distance, Im image light image point distance, Ob observation angle, Va deposition angle

Claims (7)

A transmissive screen comprising a microlens array,
An aperture array disposed on a surface opposite to the surface on which the microlens array is disposed;
The light shielding portion of the aperture array is a metal film,
The metal film has a thickness of 50 nm or more and 200 nm or less,
screen.   The screen according to claim 1, wherein the surface of the metal film has a reflectance of 80% or more of light having a wavelength of 380 nm to 780 nm.   The screen according to claim 1, wherein the surface roughness of the metal film is an arithmetic average roughness Ra of 0.1 μm or less.   The screen according to claim 1, further comprising a protective layer on the metal film. A method for manufacturing a transmission screen comprising an aperture array disposed on a surface opposite to a surface on which a microlens array is disposed,
When forming the aperture array on the surface opposite to the surface where the microlens array of the transparent substrate is arranged,
A negative resist is applied to the surface opposite to the surface on which the microlens array of the transparent substrate is disposed,
Irradiate exposure light from the microlens array side toward the transparent substrate,
Exposing the negative resist with the exposure light, further developing to form a resist pattern,
A metal film having a thickness of 50 nm or more and 200 nm or less is formed on the surface of the transparent substrate on which the resist pattern is formed,
Forming an opening array having a light-shielding portion made of the metal film by removing the resist pattern;
Screen manufacturing method. A method for manufacturing a transmission screen comprising an aperture array disposed on a surface opposite to a surface on which a microlens array is disposed,
When forming the aperture array on the surface opposite to the surface where the microlens array of the transparent substrate is arranged,
A metal film having a thickness of 50 nm or more and 200 nm or less is formed on the surface of the transparent substrate opposite to the surface on which the microlens array is disposed,
Forming an opening array having a light shielding portion made of the metal film by removing a part of the metal film;
Screen manufacturing method. The manufacturing method of the screen of Claim 5 or 6 which forms a protective layer on the said metal film after forming an opening array.