JP2006162793A - Optical device, image display apparatus and head-mounted display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To join transparent base materials 22 and 23 with high adhesion power, without making the characteristics of an optical element 24 deteriorated. <P>SOLUTION: One transparent base material 22 to which an optical element 24 is stuck, and the other transparent base material 23 are jointed with an adhesive 25 to interpose the optical element 24 to constitute an eyepiece optical system 21 as an optical device. The transparent base materials 22 and 23 are jointed with different adhesives 25a and 25b in a first area P, including the entire optical element 24 between the base materials 22 and 23 and a second area Q, excluding the first area P, respectively. For example, the adhesive 25b has higher adhesion power than the adhesive 25a; while the adhesive 25a has a lower contraction rate than the adhesive 25b. By using different adhesives 25a and 25b, the transparent base material 22 and 23 can be jointed with high adhesion power, while utilizing characteristics of the optical element 24 as much as possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical device in which a plurality of transparent base materials are bonded with an adhesive so as to sandwich an optical element, an image display device using the optical device, and a head-mounted display using the image display device. is there.

  Optical elements such as holograms, half mirror coats, and beam splitter layers can be affected by the external environment such as humidity and oxygen if they are embedded in a transparent substrate (sandwiched between two transparent substrates). For example, it is very useful as a combiner for a head-up display or a head-mounted display.

Here, as a means for joining the transparent base materials in which the optical element is sandwiched, a pressure-sensitive adhesive sheet or an adhesive is generally used. For example, in Patent Document 1, in manufacturing a head-up display, a base material on which a hologram optical element is pasted and another base material are joined with an adhesive sheet. Further, for example, in Patent Document 2, a base material on which a plurality of hologram masters is pasted and another base material are bonded with an adhesive, and in Patent Document 3, a plurality of hologram masters having different film thicknesses are bonded to each base. It is bonded to the material with an adhesive. Furthermore, for example, in Patent Document 4, the embossed hologram surface laminated on the substrate is partially bonded to the transparent protective film with an adhesive having a strong adhesive force.
JP-A-7-234627 JP 2002-40909 A JP 2002-341731 A Utility Model Registration No. 2524092

  However, in the method using an adhesive sheet for bonding between transparent substrates, since the hologram optical element has a thickness, air bubbles easily enter the interface between the hologram optical element and the adhesive sheet. When bubbles enter the interface, the refractive index changes at that location, so that the visibility when observing an external image through the transparent substrate is reduced. Therefore, it is effective to use an adhesive capable of suppressing the mixing of bubbles in joining the transparent substrates.

  On the other hand, when an optical element such as a hologram is used as a combiner for a head-mounted display, for example, the optical element is disposed in front of the observer's eye while being sandwiched between two transparent substrates. For this reason, in order to avoid the danger to the observer by peeling of each transparent base material, it is necessary to raise the joint strength of transparent base materials. That is, in an application using the optical element as a combiner, an overwhelmingly high bonding strength is required, and it is necessary to prevent the bonding strength from being insufficient in actual use. In addition, in applications where the optical element is used as a combiner, the adhesive is required to “not adversely affect the optical element” in addition to the “strong adhesive strength” as described above.

  However, it is practically difficult to satisfy both of these characteristics in one adhesive, and there are not many adhesives that can be used for the above-mentioned applications that require strong adhesive strength. Therefore, the transparent substrates cannot be bonded with high adhesive force without adversely affecting the optical element.

  In addition, as in Patent Document 4, in the method in which the hologram surface is partially bonded with an adhesive, the properties of the hologram are slightly deteriorated at the bonded portion, and further, the air layer existing inside the bonded portion is Detrimental to optical properties.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical device capable of bonding a plurality of transparent substrates with a strong adhesive force without deteriorating the characteristics of the optical element. An object is to provide a device, a video display device including the optical device, and a head-mounted display including the video display device.

  In the optical device of the present invention, one of the transparent base materials (also referred to as a first transparent base material) to which the optical element is attached and the other transparent base material (also referred to as a second transparent base material) are the above optical elements. An optical device bonded with an adhesive so as to sandwich the first optical region between the transparent substrates as a first region, and the first region between the transparent substrates. When the region other than is the second region, each of the transparent substrates is bonded to the first region and the second region with different adhesives.

  According to said structure, a 1st transparent base material and a 2nd transparent base material are joined so that an optical element (for example, hologram) may be pinched | interposed. As described above, since the optical element is provided on the joint surface between the first transparent substrate and the second transparent substrate, the function of the optical element is also observed while observing an external image through the joint surface. An optical device can be realized.

  Moreover, each transparent base material is joined with a different adhesive in the first region and the second region. Here, the first region is a region including the entire optical element between the transparent substrates, may be a region only on the entire optical element, or a region wider than the entire optical element. May be. On the other hand, the second region is a region other than the first region between the transparent substrates.

  Thus, by setting each transparent base material to be bonded with different adhesives in the first region and the second region, for example, as an adhesive filling the first region on the optical element An adhesive that does not deteriorate the characteristics of the optical element can be selected and used, and an adhesive having a strong adhesive force can be selected and used as the adhesive in the second region that is not on the optical element. . That is, for bonding between the transparent substrates, an adhesive that is functionally separated such as an adhesive that can maximize the characteristics of the optical element and an adhesive that can be bonded with a strong adhesive force can be used. As a result, the transparent substrates can be bonded with a strong adhesive force without deteriorating the characteristics of the optical element.

  If the first region is filled with the adhesive, the entire optical element is filled with the adhesive. Therefore, an adhesive layer is partially formed on the surface of the optical element. A conventional air layer is not formed. Therefore, the air layer does not adversely affect the optical characteristics of the optical element.

  Here, the optical element may be a hologram. In this case, since the hologram has wavelength selectivity, an optical device having both diffraction characteristics and transmission characteristics can be realized.

  The optical element may be a half mirror coat. In this case, an optical device having both reflection characteristics and transmission characteristics by a half mirror can be realized.

  Moreover, it is desirable that the adhesive in the second region has a higher adhesive force than the adhesive in the first region. In this case, in the first region, the adhesive force between the transparent substrates is reduced in the second region, that is, in a portion other than the optical device, while reducing the load applied to the optical device by the adhesive as much as possible. And a high bonding strength can be ensured.

  Further, it is desirable that the adhesive in the first region has a smaller shrinkage rate than the adhesive in the second region. In this case, the influence (deformation, etc.) on the optical element by the adhesive in the first region can be reduced to prevent the optical characteristics from deteriorating.

  The adhesive in the first region preferably has a viscosity of 2 Pa · s to 13 Pa · s. If the viscosity is less than the above lower limit value, the adhesive having a low viscosity has high fluidity, so that the adhesive may permeate the optical element and the characteristics of the optical element may be deteriorated. On the other hand, when the viscosity exceeds the above upper limit, the viscosity is too high (fluidity is too low), so that the handling is inconvenient. Therefore, when the viscosity of the adhesive in the first region is in the above range, it is possible to avoid the deterioration of the optical characteristics due to the penetration of the adhesive into the optical element and to facilitate the handling thereof.

  Further, the adhesive in the first region is desirably an ultraviolet curable adhesive or a thermosetting adhesive. Since these adhesives are of a type that does not contain a solvent, the adverse effect of the solvent on the optical element can be eliminated.

  In particular, the adhesive in the first region is preferably an ultraviolet curable adhesive. Since the ultraviolet curable adhesive has a small shrinkage rate, the deformation of the transparent substrate and the optical element and the damage to them can be suppressed as much as possible. Moreover, since heat is not required at the time of curing unlike a thermosetting adhesive, it is particularly advantageous when the transparent base material is made of, for example, plastic (deformation of the base material due to heat can be suppressed).

  In general, many adhesives other than the ultraviolet curable adhesive (for example, a thermosetting adhesive or an adhesive containing a solvent) have stronger adhesive strength than the ultraviolet curable adhesive. Therefore, as the adhesive in the second region that is not on the optical element, an adhesive other than the ultraviolet curable adhesive may be used in consideration of the adhesive force.

  When the adhesive in the first region is an ultraviolet curable adhesive, it is desirable that the adhesive in the second region is also an ultraviolet curable adhesive. In this case, since each transparent base material can be joined by simultaneously irradiating the adhesive of the first region and the adhesive of the second region with ultraviolet rays, the working efficiency is good.

  Further, the difference between the refractive index of the adhesive in the first region and the refractive index of the adhesive in the second region is preferably 0.02 or less. In this case, since there is almost no difference in refractive index between the two adhesives, these interfaces can be made inconspicuous.

  The difference between the refractive index of each transparent substrate and the refractive index of the adhesive in the first region and the second region is preferably 0.02 or less. In this case, since there is almost no difference in refractive index at the interface between each transparent substrate and each adhesive, the occurrence of distortion in the external image observed through the see-through through the bonding surface of each transparent substrate should be reduced as much as possible. Can do.

  In addition, it is desirable that each of the transparent substrates, the optical element, and the adhesive is made of an acrylic material. In the case of this structure, the adhesiveness of each transparent base material, an optical element, and an adhesive agent can be improved.

  The optical element is preferably in direct contact with the adhesive in the first region. Usually, in order to prevent an attack of other substances on the optical element, it is also possible to provide a barrier layer on the optical element and apply an adhesive thereon to bond the transparent substrates. However, since the adhesive force between the optical element and the barrier layer is relatively weak, the optical element and the barrier layer may be peeled off at the interface. Therefore, as in the present invention, such a peeling problem can be eliminated by adopting a configuration in which the optical element is in direct contact with the adhesive in the first region without passing through the barrier layer.

  In addition, by not providing a barrier layer on the optical element, there is a concern that the adhesive may adversely affect the optical element (deterioration of optical characteristics). However, this problem can be solved by selecting an adhesive that does not adversely affect the optical element as described above as the adhesive in the first region.

  An image display apparatus according to the present invention includes the above-described optical device according to the present invention and an image display element that displays an image and provides the image to the optical device. With this configuration, the observer can observe the image provided from the image display element through the optical device, and at the same time, can also observe the outside world image through the optical device.

  At this time, it is desirable that the optical element of the optical device is a volume phase type reflection hologram. In this case, by reflecting the image light provided from the image display element in the direction of the observer with the hologram, the observer can observe a virtual image. Moreover, since the volume phase reflection hologram has a high light transmittance of the external image, the observer can clearly observe the external image.

  Further, the optical element of the optical device may be a combiner that simultaneously guides an image provided from the image display element and an external image to the eyes of an observer. In this case, the observer can simultaneously observe the image provided from the image display element and the external image via the optical element.

  The optical device may constitute an eyepiece optical system that enlarges an image displayed on the image display element and guides the image as a virtual image to an observer. In this case, the observer can sufficiently visually recognize the video displayed on the video display element as a virtual image. In addition, the eyepiece optical system provides the viewer with the display image of the image display element as an enlarged virtual image, so the optical device constituting the eyepiece optical system can be made smaller and lighter, and the image display device can be made smaller and lighter. Can be realized.

  The eyepiece optical system preferably has non-axisymmetric (positive) optical power. In this case, even if the eyepiece optical system is downsized, it is possible to provide an observer with an image that has been favorably corrected for aberrations.

  The transparent base material of the optical device preferably has a configuration in which video light provided from the video display element is totally reflected inside and guided to the optical element. According to this configuration, it is possible to provide a bright image to the observer by using the image light provided from the image display element without waste. In addition, it is possible to dispose the image display element at a position away from the optical device, and a wide field of view of the observer with respect to the outside world can be secured.

  The transmittance of the optical element of the optical device is preferably 10% or more. In this case, the observer can sufficiently observe the external image through the see-through even through the optical element.

  A head-mounted display according to the present invention includes the above-described video display device and support means for supporting the video display device in front of an observer's eyes. According to this configuration, since the video display device is supported in front of the observer's eyes by the support means, the observer becomes hands-free and vacant while observing the external image and the display image on the video display element as a virtual image. A desired operation can be performed by hand. In addition, since the observation direction of the observer is determined in one direction, there is an advantage that the observer can easily search for a display image even in a dark environment.

  According to the present invention, since each transparent substrate is bonded with a different adhesive in the first region and the second region, the adhesive of the optical element can be used as an adhesive filling the first region on the optical element. An adhesive that does not deteriorate the characteristics can be selected and used, and an adhesive having a strong adhesive force can be selected and used as the adhesive in the second region that is not on the optical element. Therefore, even when each transparent substrate is bonded with the optical element interposed therebetween, the adhesive force of each transparent substrate can be increased without degrading the characteristics of the optical element. In addition, since the entire optical element is filled with an adhesive and an air layer is not formed on the optical element as in the prior art, there is no deterioration in the characteristics of the optical element due to the air layer.

An embodiment of the present invention will be described below with reference to the drawings.
2A is a plan view showing a schematic configuration of a head mounted display (hereinafter abbreviated as HMD) according to the present embodiment, and FIG. 2B is a side view of the HMD. (C) is a front view of HMD. The HMD has an image display device 1 and support means 2 that supports the image display device 1, and as a whole has an appearance in which one lens (for example, for the left eye) is removed from general glasses.

  The video display device 1 allows an observer to observe an outside world image with see-through, displays an image, and provides it to the observer as a virtual image. In the video display device 1 shown in FIG. 2C, the portion corresponding to the right eye lens of the glasses is configured by bonding two transparent base materials 22 and 23 (see FIG. 4) described later. The detailed configuration of the video display device 1 will be described later.

  The support unit 2 supports the video display device 1 in front of the observer's eyes (for example, in front of the right eye), and includes a bridge 3, a frame 4, a temple 5, a nose pad 6, and a cable 7. ing. The frame 4, the temple 5 and the nose pad 6 are provided as a pair on the left and right sides. However, when these are distinguished from each other, the right frame 4R, the left frame 4L, the right temple 5R, the left temple 5L, and the right nose pad 6R. The left nose pad 6L is expressed.

  One end of the video display device 1 is supported by the bridge 3. The bridge 3 supports the left frame 4 </ b> L and the nose pad 6 in addition to the video display device 1. The left frame 4L supports the left temple 5L so as to be rotatable. On the other hand, the other end of the video display device 1 is supported by the right frame 4R. An end of the right frame 4R opposite to the support side of the video display device 1 supports the right temple 5R so as to be rotatable. The cable 7 is a wiring for supplying an external signal (for example, a video signal and a control signal) and power to the video display device 1 and is provided along the right frame 4R and the right temple 5R.

  When the observer uses the HMD, the right temple 5R and the left temple 5L are brought into contact with the right and left heads of the observer, and the nose pad 6 is put on the nose of the observer so as to wear general glasses. The HMD is attached to the observer's head. In this state, when an image is displayed on the image display device 1, the observer can observe the image on the image display device 1 as a virtual image, and also observes the outside world image through the image display device 1 in a see-through manner. be able to.

  The HMD is not limited to the one provided with only one video display device 1. For example, FIG. 3A is a plan view showing another configuration of the HMD, FIG. 3B is a side view of the HMD, and FIG. 3C is a front view of the HMD. . As shown in these drawings, the HMD may be configured to include two video display devices 1 arranged in front of both eyes of the observer. In this case, the video display device 1 arranged in front of the left eye is supported between the bridge 3 and the left frame 4L. The cable 7 is connected to both the video display apparatuses 1, and an external signal or the like is supplied to both the video display apparatuses 1 through the cable 7.

Next, details of the above-described video display device 1 will be described.
FIG. 4 is a cross-sectional view illustrating a schematic configuration of the video display device 1. The video display device 1 includes a video display element 11 and an eyepiece optical system 21.

  The video display element 11 includes a light source 12, a unidirectional diffuser plate 13, a condenser lens 14, and an LCD 15. The light source 12, the unidirectional diffuser plate 13, and the condenser lens 14 constitute an illumination optical system that illuminates the LCD 15.

  The light source 12 is composed of an RGB-integrated LED that emits light in three wavelength bands whose central wavelengths are, for example, 465 nm, 520 nm, and 635 nm. The light source 12 may be a white light source that emits white light.

  The unidirectional diffuser plate 13 diffuses the illumination light from the light source 12, but the degree of diffusion differs depending on the direction. More specifically, the unidirectional diffuser plate 13 diffuses incident light by about 40 ° in the direction corresponding to the left and right direction when the HMD is worn by the observer (direction perpendicular to the paper surface of FIG. 4). Is diffused by about 2 ° in the up-and-down direction (direction parallel to the paper surface of FIG. 4) when the observer wears.

  The condensing lens 14 condenses the light diffused by the unidirectional diffusion plate 13. The condenser lens 14 is disposed so that the diffused light efficiently forms the optical pupil E. The LCD 15 is display means for displaying an image by modulating incident light based on the image signal.

  On the other hand, the eyepiece optical system 21 has two transparent base materials 22 and 23 and an optical element 24. This eyepiece optical system 21 constitutes an optical device in which an external image is observed through through the joint surfaces of the transparent base materials 22 and 23, and enlarges and observes an image displayed on the image display element 11. This constitutes an optical device that guides the person's eyes as a virtual image. Further, the eyepiece optical system 21 has a non-axisymmetric positive optical power, and the image light incident on the inside is favorably corrected for aberration.

  The transparent base materials 22 and 23 are made of, for example, an acrylic resin, and these are bonded with an adhesive 25 (see FIGS. 1A and 1B). The transparent base material 22 at this time is formed in a shape in which the lower end portion of the parallel plate is thinned toward the lower end so as to be wedge-shaped, and the upper end portion thereof is thickened toward the upper end. The transparent base material 23 is configured to be a substantially parallel flat plate integrated with the transparent base material 22 by forming the upper end portion of the parallel flat plate along the lower end portion of the transparent base material 22.

  For example, when the transparent base material 23 is not bonded to the transparent base material 22, the external world image is refracted when passing through the wedge-shaped lower end portion of the transparent base material 22, so that the external environment observed through the transparent base material 22 is used. The image is distorted. However, by joining the transparent base material 23 to the transparent base material 22 to form an integral substantially parallel flat plate, the refraction when the light of the external image passes through the wedge-shaped lower end portion of the transparent base material 22 is reduced. The material 23 can be canceled. As a result, it is possible to prevent distortion in the external image observed through the see-through.

  The optical element 24 is configured by a volume phase type reflection hologram that diffracts light in three wavelength bands, for example, 465 ± 10 nm, 520 ± 10 nm, and 635 ± 10 nm, which are incident at a specific incident angle. The optical element 24 is affixed to the inclined surface at the lower end of the transparent base material 22, and as a result, is sandwiched between the transparent base materials 22 and 23. The transmittance of the optical element 24 is set to 10% or more.

  Here, the volume phase type reflection hologram includes, for example, a process of attaching a photosensitive material such as a photopolymer on the transparent substrate 22, a process of exposing the photosensitive material with a laser beam, a fixing process by ultraviolet irradiation, and a baking process. It is formed through a bonding process by ultraviolet irradiation. In addition, as the optical element 24, an optical film having reflection / transmission characteristics may be pasted on the transparent substrate 22, or a half mirror coat in which an inorganic material is coated on the bonding surface of the transparent substrate 22 by vapor deposition or the like. It may be.

  With such a configuration of the video display device 1, the light emitted from the light source 12 of the video display element 11 is diffused by the unidirectional diffusion plate 13, condensed by the condenser lens 14, and enters the LCD 15. The light incident on the LCD 15 is modulated based on the video signal and emitted as video light. At this time, the image itself is displayed on the LCD 15.

  The image light from the LCD 15 enters the inside of the transparent base material 22 of the eyepiece optical system 21 from its upper end surface, is totally reflected a plurality of times by two opposing surfaces, and enters the optical element 24. The light incident on the optical element 24 is reflected and reaches the optical pupil E. At the position of the optical pupil E, the observer can observe an enlarged virtual image of the image displayed on the LCD 15. The distance from the optical pupil E to the virtual image is about several meters, and the size of the virtual image is 10 times or more that of the image displayed on the LCD 15.

  On the other hand, since the transparent base materials 22 and 23 and the optical element 24 transmit almost all the light from the outside, the observer can observe the outside world image. Therefore, the virtual image of the image displayed on the LCD 15 is observed while overlapping with a part of the external image. From the above, it can be said that the optical element 24 functions as a combiner that simultaneously guides the image provided from the image display element 11 and the external image to the eyes of the observer.

  As described above, the video display device 1 is configured to guide the video light emitted from the LCD 15 to the optical element 24 by total reflection in the transparent substrate 22. Thereby, the video display element 11 can be disposed at a position far away from immediately before the eyes of the observer, and a wide field of view for the outside of the observer can be secured. Moreover, the thickness of the transparent substrates 22 and 23 can be set to about 3 mm as in the case of a normal spectacle lens, and the video display device 1 can be reduced in size and weight.

  Further, since the optical element 24 diffracts only the light having the specific incident angle and the specific wavelength as described above, the optical element 24 does not affect the light of the external image transmitted through the transparent base materials 22 and 23 and the optical element 24. Therefore, the observer can observe the external image as usual through the transparent base materials 22 and 23 and the optical element 24. Further, since the transmittance of the optical element 24 is set to 10% or more, the observer can sufficiently observe the external field image through the transparent base materials 22 and 23 and the optical element 24.

Next, the joint part of the transparent base materials 22 and 23 will be described.
FIG. 5A shows a plan view of the transparent substrate 22 (first transparent substrate), and FIG. 5B shows a front view of the transparent substrate 22. FIG. 5C shows a plan view of the transparent base material 23 (second transparent base material), and FIG. 5D shows a front view of the transparent base material 23. Furthermore, FIG.5 (e) has shown the top view of the eyepiece optical system 21 to which the transparent base materials 22 * 23 were joined.

  The transparent base material 22 has a substantially quadrangular pyramid shape as a whole, and its upper surface and lower surface are connected by four side surfaces. These four side surfaces are configured by surfaces 22a, 22b, 22c, and 22d arranged counterclockwise around the upper surface in the plan view of FIG. These surfaces 22a, 22b, 22c, and 22d have mutually different normal directions. Further, a protruding portion 22e protruding upward from the upper surface is formed on one side surface (for example, the surface 22d) of these. The optical element 24 is attached to, for example, the surface 22b of the transparent substrate 22.

  On the other hand, the transparent base material 23 has such a shape that a parallel flat plate is formed by joining the transparent base material 22. That is, the transparent base material 23 has a shape obtained by cutting out the shape of the transparent base material 22 from a parallel plate. Here, in the transparent base material 23, the surfaces facing the surfaces 22a, 22b, and 22c of the transparent base material 22 when bonded to the transparent base material 22 are referred to as 23a, 23b, and 23c, respectively. The normal directions of these surfaces 23a, 23b, and 23c are different from each other.

  In this way, the other transparent base material 23 is bonded to one transparent base material 22 to which the optical element 24 is attached via an adhesive 25 (see FIGS. 1A and 1B) so as to sandwich the optical element 24. As a result, an eyepiece optical system 21 is formed as shown in FIG. The eyepiece optical system 21 is shaped like a spectacle lens in plan view. By using this eyepiece optical system 21, it is possible to observe an external image through the see-through through the joint surfaces (surfaces 22a, 22b, and 22c, surfaces 23a, 23b, and 23c) of the transparent base materials 22 and 23. .

  Here, FIG. 1A is a cross-sectional view of a part of the eyepiece optical system 21, and FIG. 1B is a cross-sectional view of the other part of the eyepiece optical system 21. When the area including the entire optical element 24 between the transparent base materials 22 and 23 is defined as a first area P, and the area other than the first area P between the transparent base materials 22 and 23 is defined as a second area Q, In the embodiment, the transparent base materials 22 and 23 are joined by the adhesive 25 having different characteristics in the first region P and the second region Q. More specifically, in the first region P, the transparent base materials 22 and 23 are bonded with an adhesive 25a, and in the second region Q, the transparent base materials 22 and 23 are bonded with an adhesive 25b. It is joined.

  In addition, as the 1st area | region P, the area | region between the surface 22b and the surface 23b can be assumed among the transparent base materials 22 * 23, and as the 2nd area | region Q, transparent base material 22 * A region between the surface 22a and the surface 23a and a region between the surface 22c and the surface 23c can be assumed. At this time, the first region P includes a region between the surface 22b and the surface 23b among the transparent base materials 22 and 23, and a part of the region or the surface between the surface 22a and the surface 23a. An area extending over a part of the area between 22c and the surface 23c may be assumed.

  As the adhesive 25a filled in the first region P and the adhesive 25b filled in the second region Q, it is desirable to use the following from the viewpoint of adhesive strength and shrinkage rate.

  As the adhesive 25b, it is desirable to use an adhesive having a higher adhesive strength than the adhesive 25a. For example, when an ultraviolet curable adhesive such as Hard Rock OP-1050 manufactured by Denki Kagaku Kogyo Co., Ltd. or NOA61 manufactured by Norland Optical Co. is used as the adhesive 25a, the adhesive 25b includes Aron Alpha manufactured by Toagosei Co., Ltd. Such solvent-based instant adhesives, photo-curing adhesives such as the Lux Track series manufactured by Toagosei Co., Ltd., epoxy two-component adhesives, and the like can be used.

  When the transparent base materials 22 and 23 are joined using such adhesives 25a and 25b, the adhesive force between the transparent base materials 22 and 23 is higher than the part joined with the adhesive 25a than the part joined with the adhesive 25a. Is stronger. Therefore, in the eyepiece optical system 21, the bonding strength of the transparent base materials 22 and 23 can be ensured at portions other than the optical element 24, and it is possible to reduce the impact of the impact and load on the optical element 24.

  Moreover, as the adhesive 25a, it is desirable to use an adhesive having a smaller shrinkage rate than the adhesive 25b. Here, the shrinkage rate is expressed as a percentage of (volume after shrinkage / volume before shrinkage). As a standard of the shrinkage rate of the adhesive 25a, 5% or less is desirable and 3% or less is more desirable. Examples of the adhesive 25a having a shrinkage rate of 5% or less include LCR0629B manufactured by Toagosei Co., Ltd. and NOA68 and NOA76 manufactured by Norland Optical. In general, there are many instantaneous adhesives and thermosetting adhesives with strong adhesive force, which have a large shrinkage rate, but the adhesive 25a filled on the optical element 24 has a low shrinkage rate, an ultraviolet curing. It is desirable to use a photocurable adhesive such as a mold.

  Since the shrinkage rate of the adhesive 25a is smaller than the shrinkage rate of the adhesive 25b when filling the optical element 24, the tensile force applied to the optical element 24 due to the shrinkage of the adhesive 25a at the time of curing can be reduced. Thereby, it is possible to prevent deterioration of optical characteristics due to deformation of the optical element 24 or the like.

  As described above, in the optical device 21 according to the present embodiment, the transparent base materials 22 and 23 include the adhesives 25a and 25a having different characteristics in the first region P and the second region Q between the transparent base materials 22 and 23, respectively. Joined at 25b. By separating the adhesive used for the first region P and the second region Q in this way, an adhesive that does not deteriorate the characteristics of the optical element 24 is selected as the adhesive 25a to be filled on the optical element 24. An adhesive having a strong adhesive force can be selected and used as the adhesive 25b filled in the region other than on the optical element 24. As a result, even when the transparent base materials 22 and 23 are bonded with the optical element 24 interposed therebetween, the adhesive strength of the transparent base materials 22 and 23 can be increased without deteriorating the characteristics of the optical element 24. Further, by separating the function of the adhesive 25 into the adhesive 25a and the adhesive 25b, the range of material selection for the adhesives 25a and 25b to be used can be expanded.

  Moreover, since the adhesive 25a is filled on the entire optical element 24, an air layer is not formed on the optical element 24. Therefore, the optical characteristics of the optical element 24 are not deteriorated by the air layer. is there.

  By the way, as the adhesive 25a filled in the first region P, it is desirable to use an adhesive having a viscosity of 2 Pa · s to 13 Pa · s. As the adhesive 25a having such a viscosity range, for example, LCR0628A manufactured by Toagosei Co., Ltd. or NOA68 manufactured by Norland Optical Co. can be used.

  If the viscosity of the adhesive 25a is less than the above lower limit value, the fluidity of the adhesive 25a is too high, so that the adhesive 25a penetrates into the optical element 24 and the characteristics of the optical element 24 may deteriorate. On the contrary, if the viscosity of the adhesive 25a exceeds the above upper limit value, the fluidity of the adhesive 25a is too low, so that the handling becomes inconvenient and the transparency is deteriorated. It is not desirable as an adhesive. Therefore, by using the adhesive 25a having a viscosity in the above range, it is possible to avoid the deterioration of the optical characteristics due to the penetration of the adhesive 25a into the optical element 24 and to facilitate the handling thereof.

  In addition, there is no restriction | limiting in particular about the viscosity of the adhesive agent 25b. However, from the viewpoint of ease of handling and the like, the viscosity of the adhesive 25b is preferably approximately the same as the viscosity of the adhesive 25a.

  The adhesive 25a in the first region P is preferably an ultraviolet curable adhesive or a thermosetting adhesive. That is, the adhesive 25a is desirably an adhesive that does not contain a solvent. Examples of such an adhesive 25a include LCR0628A manufactured by Toagosei Co., Ltd. and NOA61 and NOA71 manufactured by Norland Optical.

  In general, many adhesives with strong adhesive strength contain a solvent. However, when the optical element 24 is composed of a hologram as in the present embodiment, if an adhesive containing a solvent is used, the solvent contained in the adhesive penetrates into the hologram layer, so that the optical characteristics deteriorate. Moreover, since solvent molecules volatilize during curing, many solvent-containing adhesives have a large shrinkage rate, which adversely affects the optical element 24. Therefore, in order to avoid these inconveniences, it is desirable that the adhesive 25a be an ultraviolet curable adhesive or a thermosetting adhesive that is an adhesive that does not contain a solvent.

  At this time, the adhesive 25a is preferably an ultraviolet curable adhesive. Since the ultraviolet curable adhesive has a small shrinkage rate, deformation of the transparent base materials 22 and 23 and the optical element 24 and damage to them can be suppressed as much as possible. Moreover, since heat is not required at the time of curing unlike a thermosetting adhesive, even if the transparent base materials 22 and 23 are made of, for example, an acrylic resin, the transparent base materials 22 and 23 are prevented from being deformed by heat. can do.

  As described above, when the ultraviolet curable adhesive is used as the adhesive 25a filled in the first region P, the ultraviolet curable adhesive is used also as the adhesive 25b filled in the second region Q. May be. For example, when NOA68 manufactured by Norland Optical is used as the adhesive 25a, LCR0628A manufactured by Toagosei Co., Ltd. can be used as the adhesive 25b. In this case, when each of the adhesives 25a and 25b is cured, the transparent base materials 22 and 23 can be bonded to each other by only one ultraviolet irradiation step, so that the production efficiency is simple.

  In general, many UV-curable adhesives do not adversely affect the optical element 24 such as a hologram. However, few UV curable adhesives have high adhesive strength. Therefore, an ultraviolet curable adhesive is used as the adhesive 25a on the optical element 24, and an adhesive other than the ultraviolet curable adhesive (for example, a solvent-based instantaneous adhesive or a thermosetting adhesive) is used as the adhesive 25b. May be used. For example, NOA68 manufactured by Norland Optical may be used as the adhesive 25a, and 1521 manufactured by ThreeBond may be used as the adhesive 25b. By doing in this way, the transparent base materials 22 and 23 can be joined strongly, without damaging the optical element 24. FIG.

  Further, the difference between the refractive index of the adhesive 25a and the refractive index of the adhesive 25b is preferably 0.02 or less. For example, if NOA76 manufactured by Norland Optical is used as the adhesive 25a and LCR0631 manufactured by Toagosei Co., Ltd. is used as the adhesive 25b, a refractive index difference of 0.02 or less can be easily realized. In this case, the boundary line between the two types of adhesives 25a and 25b can be made inconspicuous, and the appearance quality can be improved.

  As described above, when the refractive indexes of the two types of adhesives 25a and 25b are different, the two types of adhesives 25a and 25b may be mixed in the vicinity of the interface so that the refractive index difference changes stepwise. In this case, the boundary line of the interface can be made less noticeable.

  The difference between the refractive index of the transparent base materials 22 and 23 and the refractive index of the adhesives 25a and 25b is preferably 0.02 or less. For example, if the acrypet manufactured by Mitsubishi Rayon is used as the transparent base material 22 or 23, NOA76 manufactured by Norland Optical is used as the adhesive 25a, and LCR0631 manufactured by Toagosei is used as the adhesive 25b, the above refraction A rate difference of 0.02 or less can be easily realized. In this case, the interface between the transparent base materials 22 and 23 and the adhesives 25a and 25b can be made inconspicuous, and the appearance quality can be improved. In addition, since light refraction and scattering at the interface between the transparent base materials 22 and 23 and the adhesives 25a and 25b is reduced, the observer can visually recognize the external image without any problem (without distortion) through the joint. .

  By the way, as the transparent base materials 22 and 23, an acrylic material excellent in transparency and moldability is used, and as the optical element 24 made of a hologram, an acrylic material (acrylate derivative) showing an excellent refractive index change is used. It is desirable to use a photopolymer. Therefore, when the transparent base materials 22 and 23 and the optical element 24 are made of such a material to produce an optical device, the adhesives 25a and 25b for joining the transparent base materials 22 and 23 include acrylic materials ( It is desirable to use an acrylate derivative).

  More specifically, as the material of the transparent base materials 22 and 23, for example, a material containing a methacrylic resin (for example, an acrypet manufactured by Mitsubishi Rayon, a Delpet manufactured by Asahi Kasei Corporation) can be used. As the material (photosensitive material) of the optical element 24, for example, a material containing polymethyl methacrylate, phenoxyethyl acrylate, or chlorophenyl acrylate (for example, OmniDex manufactured by DuPont) can be used. In this case, as the adhesive 25a, for example, an adhesive containing an acrylic modified oligomer (for example, LCR0628A manufactured by Toagosei Co., Ltd.) is used, and as the adhesive 25b, an adhesive including tetrahydrofuruyl methacrylate (for example, NOA68 of Norland Optical) is used. be able to.

  Generally, the same kind of material is stronger than the dissimilar material in terms of adhesion (adhesive force) of the material. Therefore, when acrylic materials are used for both the optical element 24 (photosensitive material) and the transparent base materials 22 and 23, it is inevitably more powerful that the adhesives 25a and 25b are also made of acrylic materials. It becomes possible to join.

  By the way, when the optical element 24 is a hologram, for example, as in the present embodiment, the hologram is a film. Therefore, when the adhesive 25a contracts, for example, the optical element 24 is pulled by the adhesive 25a. In some cases, the optical characteristics of the optical element 24 deteriorate. Therefore, normally, as shown in FIG. 6A, a barrier layer 26 is provided between the optical element 24 and the adhesive 25a to reduce the adverse effect of the adhesive 25a on the optical element 24. Is taken. However, even if such a barrier layer 26 is provided, the adhesion state at the interface between the optical element 24 and the barrier layer 26 is not so strong, and the barrier layer 26 may peel off from the optical element 24 in some cases.

  Therefore, in the present embodiment, as shown in FIG. 6B, the optical element 24 is in direct contact with the adhesive 25a and not through the barrier layer 26. Thereby, such a peeling problem can be eliminated. At this time, there is a concern that the adhesive 25a directly deteriorates the optical characteristics of the optical element 24 due to the adhesive 25a being in direct contact with the optical element 24. This can be solved by selecting an adhesive that does not adversely affect 24.

  By the way, in this embodiment, although the joint surface of each transparent base material 22 and 23 demonstrated the structure containing several surface (surface 22a * 22b * 22c, surface 23a * 23b * 23c) from which a normal line direction differs. The bonding surface may be only one surface.

  For example, FIG. 7A is a plan view showing another configuration example of the transparent base material 22, and FIG. 7B is a plan view showing another configuration example of the transparent base material 23. (C) is a top view which shows the other structural example of the eyepiece optical system 21 to which the transparent base materials 22 and 23 were joined. The bonding surface of the transparent substrate 22 is only one surface 22f, and the bonding surface of the transparent substrate 23 is only one surface 23f. And the transparent base materials 22 and 23 are joined via an adhesive so that the surface 22f and the surface 23f face each other, and thereby the eyepiece optical system 21 is configured.

  As shown in FIGS. 7 (a) and 7 (b), the optical element between the transparent base materials 22 and 23, even if the joining surface is only one in each of the transparent base materials 22 and 23 as described above. 24, the first region P including the entire upper surface and the second region Q other than the first region P are filled with the adhesives 25a and 25b described in the present embodiment, respectively, and the transparent base materials 22 and 23 are filled. The effect similar to this embodiment can be acquired by joining each other.

  As described above, in this embodiment, various conditions are shown for the adhesives 25a and 25b, but by using the adhesives 25a and 25b that satisfy as many conditions as possible, a bonded optical device having excellent optical characteristics is manufactured. It becomes possible to do.

  In the present embodiment, the case where two types of adhesives 25a and 25b are used as the adhesive 25 has been described. However, if necessary, three, four or more adhesives may be used depending on the function. It is also possible to join the transparent base materials 22 and 23 by using them.

  In addition, although this embodiment demonstrated the case where the joint surface of transparent base materials 22 and 23 was a plane, it is not necessarily limited to this, For example, a curved surface may be sufficient.

  In the present embodiment, the example in which the video display device 1 is applied to the HMD has been described. However, for example, the video display device 1 may be applied to a head-up display.

  In the present embodiment, as the transparent base materials 22 and 23, those on a flat plate are used, but they may have a curvature. In this case, the eyepiece optical system 21 can have a function as a correction spectacle lens.

(A) is sectional drawing of a part of eyepiece optical system of the video display apparatus used for the head mounted display which concerns on one Embodiment of this invention, (b) is another part of the said eyepiece optical system. It is sectional drawing. (A) is a top view which shows the schematic structure of the said head mounted display, (b) is a side view of the said head mounted display, (c) is a front view of the said head mounted display. (A) is a top view which shows the other structure of the said head mounted display, (b) is a side view of the said head mounted display, (c) is a front view of the said head mounted display. It is sectional drawing which shows the schematic structure of the said video display apparatus. (A) is a top view which shows one schematic structure of the two types of transparent base materials which comprise the said eyepiece optical system, (b) is a front view of the said transparent base material, (c) ) Is a plan view showing a schematic configuration of the other transparent substrate, (d) is a front view of the transparent substrate, and (e) is a plan view of the eyepiece optical system. (A) is sectional drawing which shows the structure of the eyepiece optical system which provided the barrier layer on the optical element, (b) is sectional drawing which shows the structure of the eyepiece optical system which abbreviate | omitted the barrier layer. (A) is a top view which shows the other structural example of one transparent base material of the 2 types of transparent base materials which comprise the said eyepiece optical system, (b) is said other transparent base material. It is a top view which shows the other structural example, (c) is a top view which shows the other structural example of the said eyepiece optical system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support means 11 Image display element 21 Eyepiece optical system (optical device)
DESCRIPTION OF SYMBOLS 22 Transparent base material 23 Transparent base material 24 Optical element 25 Adhesive agent 25a Adhesive agent 25b Adhesive agent P 1st area | region Q 2nd area | region

Claims (21)

An optical device in which an optical element is bonded to one transparent base material and the other transparent base material are bonded with an adhesive so as to sandwich the optical element,
When a region including the entire optical element between the transparent substrates is a first region, and a region other than the first region between the transparent substrates is a second region,
Each said transparent base material is joined by the different adhesive agent in the said 1st area | region and the said 2nd area | region, The optical device characterized by the above-mentioned.   The optical device according to claim 1, wherein the optical element is a hologram.   The optical device according to claim 1, wherein the optical element is a half mirror coat.   4. The optical device according to claim 1, wherein the adhesive in the second region has a higher adhesive force than the adhesive in the first region. 5.   The optical device according to any one of claims 1 to 4, wherein the adhesive in the first region has a smaller shrinkage rate than the adhesive in the second region.   The optical device according to claim 1, wherein the adhesive in the first region has a viscosity of 2 Pa · s to 13 Pa · s.   The optical device according to claim 1, wherein the adhesive in the first region is an ultraviolet curable adhesive or a thermosetting adhesive.   The optical device according to claim 7, wherein the adhesive in the first region is an ultraviolet curable adhesive.   The optical device according to claim 8, wherein the adhesive in the second region is an ultraviolet curable adhesive.   The difference between the refractive index of the adhesive in the first region and the refractive index of the adhesive in the second region is 0.02 or less, according to any one of claims 1 to 9, Optical device.   The difference between the refractive index of each of the transparent substrates and the refractive index of the adhesive in the first region and the second region is 0.02 or less. An optical device according to claim 1.   The optical device according to claim 1, wherein each of the transparent base material, the optical element, and the adhesive is made of an acrylic material.   The optical device according to claim 1, wherein the optical element is in direct contact with the adhesive in the first region. An optical device according to any one of claims 1 to 13,
An image display device comprising: an image display element for displaying an image and providing the image to the optical device.   15. The video display device according to claim 14, wherein the optical element of the optical device is a volume phase type reflection hologram.   16. The video display device according to claim 14, wherein the optical element of the optical device is a combiner that simultaneously guides an image provided from the video display element and an external image to the eyes of an observer.   17. The eyepiece optical system according to claim 14, wherein the optical device constitutes an eyepiece optical system that enlarges an image displayed on the image display element and guides the image as a virtual image to an observer's eye. Video display device.   The video display device according to claim 17, wherein the eyepiece optical system has non-axisymmetric optical power.   19. The video display according to claim 14, wherein the transparent base material of the optical device totally reflects the image light provided from the video display element and guides the light to the optical element. apparatus.   20. The image display device according to claim 14, wherein the transmittance of the optical element of the optical device is 10% or more. The video display device according to any one of claims 14 to 20,
A head-mounted display comprising: support means for supporting the video display device in front of an observer's eyes.

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