JP2010113056A - Polarization conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization conversion element having excellent transmittance and heat resistance. <P>SOLUTION: The polarization conversion element 1 includes a block body 20 which is a flat plate member wherein a first base material 11 and a second base material 12 are alternately disposed via a polarization split layer 13 or a reflection layer 14, and a retardation plate 15 is selectively arranged on a light emission face side of the block body 20. In the block body 20, a joint face 20A on the side for arranging the retardation plate 15 has a first joint layer 161 arranged on one surface, and when the first joint layer 161 is molecularly bonded to a second joint layer 162 arranged on a joint face 15A on the side to be connected to the bock body 20 of the retardation plate 15, a joint layer 16 is formed. The reflection layer 14 is disposed in an intermediate position between the adjacent polarization split layers 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarization conversion element.

In optical pickups, liquid crystal projectors, and other devices, an optical article formed by sandwiching an optical thin film between a plurality of optical members is used.
As such an optical article, a polarizing separation film is sequentially laminated between two optical members each provided with a reflection film therein, and a phase difference is formed on the light exit surface side of the polarization separation film of these optical members. There is a polarization conversion element (PS conversion element) provided with a plate.

These optical articles are manufactured by various methods, and one of them is a conventional example in which an optical member and a polarization separation film are bonded and fixed with an adhesive. For example, in a polarization conversion element, there is a conventional example (Patent Document 1) in which an ultraviolet curable adhesive is used to bond a retardation plate using quartz to a transparent member.
In addition, when bonding silicon and glass, etc., the bonded surfaces are subjected to hydrophilic treatment (activation) with oxygen plasma, the hydrophilic processed optical members are directly bonded, and heated at about 400 ° C. (Patent Document). 2).

JP 2003-302523 A Japanese Patent No. 3751972

In the conventional example shown in Patent Document 1, since the transparent member and the retardation plate are bonded and fixed with an adhesive, there is a problem in that a reflection loss occurs due to a difference in refractive index of each layer, resulting in a decrease in transmittance. Further, the adhesive layer made of an adhesive has a problem that the refractive index is different because the cured state of the adhesive is different within the surface, and the accuracy is lowered.
In the conventional example shown in Patent Document 2, since the optical members whose bonded surfaces are activated are directly bonded to each other, there is a problem that reflection loss occurs between the two optical members to be bonded due to a difference in refractive index.

  An object of the present invention is to provide a polarization conversion element excellent in transmittance and heat resistance.

[Application Example 1]
A polarization conversion element according to this application example is a polarization conversion element having a first optical member having a refractive index n _{1 and} a second optical member having a refractive index n ₂ (n ₁ ≠ n ₂ ), and is a plasma polymerization film. it is formed, with a bonding layer to molecular bonding the second optical member and the first optical member, wherein the refractive index n ₃ of the bonding layer is between n ₁ and n _2.
In this application example of this arrangement, between the second optical member first optical member and a refractive index having a refractive index of n ₁ is n _2, is a value between the refractive index of n ₁ and n ₂ A bonding layer formed of an n ₃ plasma polymerized film is provided. Therefore, since the difference in refractive index between the first optical member and the second optical member is small, reflection loss at the interface can be suppressed. That is, a polarization conversion element having excellent transmittance can be provided. In addition, since no adhesive is used, a polarization conversion element excellent in the accuracy of the refractive index of the bonding layer can be obtained.

[Application Example 2]
In the polarization conversion element according to this application example, the main material of the plasma polymerization film is polyorganosiloxane.
In this application example of this configuration, since the polyorganosiloxane that is the main material of the plasma polymerized film is relatively flexible, when joining the first optical member and the second optical member having different linear expansion coefficients. Furthermore, the stress accompanying the thermal expansion of both optical members can be relieved. Therefore, peeling between the first optical member and the second optical member can be reliably prevented. Moreover, since polyorganosiloxane is excellent in chemical resistance, it can be effectively used for optical articles that are exposed to chemicals for a long time. And if the main component of polyorganosiloxane is a polymer of octamethyltrisiloxane, this polymer is not only easy to handle but also a plasma polymerized film made of the polymer has excellent adhesion. Is preferable.

[Application Example 3]
In the polarization conversion element according to this application example, the first optical member is a glass substrate, and the second optical member is a retardation plate made of quartz.
In this application example having this configuration, a plasma bonding layer is provided between the first optical member that is a glass substrate and the second optical member that is crystal. There is a difference in the refractive index between the glass substrate and quartz, but by providing a plasma bonding layer between them with a refractive index that is intermediate between the refractive index of the glass substrate and quartz, reflection loss that occurs at the interface of each layer Can be suppressed. That is, a polarization conversion element having excellent transmittance can be provided.

[Application Example 4]
In the polarization conversion element according to this application example, the first optical member is a glass substrate, and the second optical member is a dielectric multilayer film.
In this application example having this configuration, a plasma bonding layer is provided between the first optical member, which is a glass substrate, and the second optical member made of a dielectric multilayer film. The dielectric multilayer film is a polarization separation film whose outermost layer is formed of SiO ₂ , and is designed so that no reflection loss occurs. There is a difference in refractive index between the outermost layer of the dielectric multilayer film and the glass substrate, but a plasma bonding layer having a refractive index intermediate between the refractive index of the glass substrate and the outermost layer made of SiO ₂ is provided between them. Thus, it is possible to suppress the reflection loss that occurs at the interface of each layer. That is, a polarization conversion element having excellent transmittance can be provided.

[Application Example 5]
In the polarization conversion element according to this application example, the bonding layer is formed on the entire bonding surface of at least one of the first optical member and the second optical member.
In this application example having this configuration, since the plasma bonding layer is formed on the entire bonding surface, a complicated process such as a mask is not required, and it can be easily manufactured, and productivity can be improved.

[Application Example 6]
In the polarization conversion element according to this application example, the bonding layer is formed in multiple layers, and each layer of the bonding layer has a large refractive index from the side of the first optical member and the second optical member having a small refractive index. The layers are stacked in ascending order of refractive index.
In this application example having this configuration, the bonding layer between the first optical member and the second optical member is formed in multiple layers. In this case, assuming that the refractive index of each layer of the bonding layer is n ₃₁ , n ₃₂ , n ₃₃ ,..., N _3n from the smallest, from the side of the first optical member and the second optical member having the smaller refractive index. n _3n are stacked in the order of n ₃₁ , n ₃₂ , n ₃₃ ,..., n _3n , and the refractive indexes n ₃₁ , n ₃₂ , n _{33 ,.} The value is between ₁ and the refractive index n ₂ of the second optical member. For example, when n ₁ <n ₂ , n ₁ <n ₃₁ <n ₃₂ <n ₃₃ <... <N _3n <n ₂ , and when n ₁ > n ₂ , n ₁ > n ₃₁ > N ₃₂ > n ₃₃ >...> N _3n > n ₂ Therefore, the difference in refractive index among the first optical member, the bonding layer, and the second optical member can be further reduced, and reflection loss at the interface can be further suppressed. As a result, it is possible to provide a polarization conversion element that is more excellent in transmittance.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a view showing an end face of a polarization conversion element according to this embodiment, and FIGS. 2 and 3 are cross-sectional views showing the main part of FIG. Here, the polarization conversion element is a PS conversion element (or a polarization beam splitter, Polarized Beam Splitter, PBS). This polarization conversion element is used in, for example, a liquid crystal projector device.
In FIG. 1, the polarization conversion element 1 includes a block body 20 that is a flat plate member in which a first base material 11 and a second base material 12 are alternately arranged with a polarization separation layer 13 or a reflection layer 14 interposed therebetween. In addition, a phase difference plate 15 is selectively provided on the light exit surface side of the block body 20. The joining surface 20A on the side where the retardation plate 15 of the block body 20 is provided has a first joining layer 161 provided on one surface, and is provided on the joining surface 15A on the side of joining the block body 20 of the retardation plate 15. The bonding layer 16 is formed by molecular bonding with the second bonding layer 162 thus formed. The reflection layer 14 is disposed at an intermediate position between the adjacent polarization separation layers 13.
The first base material 11 and the second base material 12 have a plane on the light incident side and a plane on the light output side parallel to each other, and the polarization separation layer 13 and the reflective layer 14 have an angle of 45 ° with respect to these planes. Are arranged parallel to each other. In the present embodiment, the polarization conversion element 1 has a left-right symmetric structure.

The 1st base material 11 and the 2nd base material 12 are optical members, and are shape | molded from glass including optical glass, such as BK7, white plate glass, borosilicate glass, and blue plate glass.
As shown in FIG. 3, the polarization separation layer 13 includes a bonding layer 131 including a first bonding layer 131A and a second bonding layer 131B, and a polarization separation film 132. The first bonding layer 131A and the second bonding layer 131B are formed of a plasma polymerized film and are molecularly bonded. The polarization separation film 132 is a polarization separation film formed of a dielectric multilayer film, and converts the incident light bundle (S-polarized light and P-polarized light) into an S-polarized partial light beam (S-polarized light) and a P-polarized light part. It has a function of separating into a light beam (P-polarized light), reflecting S-polarized light, and transmitting P-polarized light (see FIG. 2). The polarization separation film 132 is configured by stacking layers of different materials, for example, a layer of silicon oxide (SiO ₂ ), a layer of lanthanum aluminate, and a layer of magnesium fluoride (MgF ₂ ). These layers are composed of a plurality of layers. In the present embodiment, the layers are composed of, for example, five layers. The first layer, the second layer, the third layer, the fourth layer, and the fifth layer are provided from the second substrate 12 side toward the first substrate 11 side, and are provided directly on the second substrate 12. Of these layers, the first layer and the fifth layer are layers of silicon oxide (SiO ₂ ), the third layer is a layer of magnesium fluoride (MgF ₂ ), and the second layer and the fourth layer are lanthanum. It is a layer of aluminate.

The reflective layer 14 is formed of a dielectric multilayer film or a metal film, and has a function of reflecting S-polarized light incident on the reflective layer 14 as it is. The multilayer film constituting the reflective layer 14 is formed by evaporating a material such as silicon dioxide or titanium oxide, for example.
The phase difference plate 15 is an optical member, and for example, a strip-shaped half-wave plate formed of an inorganic crystal material can be used. Examples of the inorganic crystal material include quartz made of a single crystal of SiO ₂ , and this quartz may be artificial quartz or natural quartz.
The bonding layer 16 includes a first bonding layer 161 and a second bonding layer 162, and the first bonding layer 161 and the second bonding layer 162 are formed of a plasma polymerized film.

Here, if the refractive index of the second substrate 12 is n ₁ and the refractive index of the retardation plate 15 is n ₂ (n ₁ ≠ n ₂ ), the refractive index n ₃ of the bonding layer 16 is n ₁ and n _2. Between the values. That is, if n ₁ > n ₂ , n ₁ > n ₃ > n ₂ , and if n ₁ <n ₂ , n ₁ <n ₃ <n ₂ . For example, if the second substrate 12 is white glass, the refractive index is 1.518, and if the retardation plate 15 is quartz, the refractive index is 1.561. Therefore, the refractive index n ₃ of the bonding layer 16 is 1.518. <N ₃ <1.561.
Further, if the refractive index of the outermost layer formed of SiO ₂ of the polarization separation film 132 is n ₁₁ (n ₁₁ ≠ n ₂ ), the refractive index n ₁₃ of the bonding layer 131 is a value between n ₁₁ and n _2. It becomes. That is, if n ₁₁ > n ₂ , n ₁₁ > n ₁₃ > n ₂ , and if n ₁₁ <n ₂ , n ₁₁ <n ₁₃ <n ₂ . For example, if the second substrate 12 is white glass, the refractive index is 1.518, and the outermost layer of the polarization separation film 132 is SiO ₂ , so the refractive index is 1.460, and thus the refractive index n _{13 of the} bonding layer 131. Is in the range of 1.518> n ₁₃ > 1.460. Since the polarization separation film 132 is designed so that no reflection loss occurs, it is not necessary to consider the reflection loss in the polarization separation film 132.

Here, the plasma polymerization films of the first bonding layer 131A and the second bonding layer 131B that form the bonding layer 131 in the polarization separation layer 13 and the first bonding layer 161 and the second bonding layer 162 that form the bonding layer 16 are used. The apparatus to form is demonstrated.
FIG. 4 is a schematic view of a plasma polymerization apparatus used in this embodiment.
In FIG. 4, the plasma polymerization apparatus 200 includes a chamber 201, a first electrode 211 and a second electrode 212 provided inside the chamber 201, and a high frequency between the first electrode 211 and the second electrode 212. The power supply circuit 220 applies a voltage, the gas supply unit 240 supplies gas into the chamber 201, and the exhaust pump 250 discharges the gas inside the chamber 201.
The first electrode 211 supports the first base material 11 and the second base material 12 as base materials, and the first electrode 211 and the second electrode sandwich the first base material 11 and the second base material 12. 212 is arranged to face.

The power supply circuit 220 includes a matching box 221 and a high frequency power supply 222.
The gas supply unit 240 includes a liquid storage unit 241 that stores a liquid film material (raw material liquid), a vaporizer 242 that vaporizes the liquid film material to change it into a raw material gas, and a gas cylinder 243 that stores a carrier gas. I have. The carrier gas stored in the gas cylinder 243 is a gas that is discharged by the action of an electric field and is introduced into the chamber 201 in order to maintain this discharge. For example, argon gas or helium gas is applicable.
The liquid storage unit 241, the vaporizer 242, the gas cylinder 243, and the chamber 201 are connected by a pipe 202, and a mixed gas of a gaseous film material and a carrier gas is supplied into the chamber 201. ing.
The film material stored in the liquid storage unit 241 is a raw material for forming the first bonding layer 161 and the second bonding layer 162 on the first base material 11 and the second base material 12 by the plasma polymerization apparatus 200, and is vaporized. It is vaporized by the device 242 to become a raw material gas.

Examples of the source gas include methylsiloxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, octamethylcyclotetrasiloxane, and methylphenylsiloxane. Examples include gallium, trimethylaluminum, triethylaluminum, triisobutylaluminum, trimethylindium, triethylindium, trimethylzinc, triethylzinc, organometallic compounds, various hydrocarbon compounds, various fluorine compounds, and the like.
A plasma polymerized film obtained by using such a raw material gas is formed by polymerizing these raw materials (polymer), that is, composed of polyorganosiloxane, organometallic polymer, hydrocarbon polymer, fluorine polymer, etc. Will be.

Polyorganosiloxane usually exhibits water repellency, but can be easily desorbed by applying various activation treatments, and can be changed to hydrophilic. That is, polyorganosiloxane is a material that can easily control water repellency and hydrophilicity.
Even if plasma polymer films composed of polyorganosiloxane exhibiting water repellency are brought into contact with each other, adhesion is inhibited by the organic group, and it is extremely difficult to adhere. On the other hand, plasma polymerized films composed of polyorganosiloxane exhibiting hydrophilicity can be bonded particularly easily when they are brought into contact with each other. That is, the advantage that the water repellency and the hydrophilicity can be easily controlled leads to the advantage that the adhesiveness can be easily controlled. Therefore, the plasma polymerized film made of polyorganosiloxane is preferably used in this embodiment. Will be. Since the polyorganosiloxane is relatively flexible, even if the constituent materials of the first base material 11 and the second base material 12 are different and the linear expansion coefficients are different, the first base material 11 and the first base material 11 The stress accompanying thermal expansion generated between the two base materials 12 can be relaxed. Furthermore, since polyorganosiloxane is excellent in chemical resistance, it can be effectively used for joining members that are exposed to chemicals for a long period of time.

  Among the polyorganosiloxanes, those mainly composed of a polymer of octamethyltrisiloxane are preferred. A plasma polymerized film composed mainly of a polymer of octamethyltrisiloxane is preferably used in the bonding method of the present embodiment because of its excellent adhesiveness. The polymer of octamethyltrisiloxane is liquid at room temperature and has an appropriate viscosity, so it is easy to handle.

Next, a method for manufacturing the polarization conversion element 1 will be described.
First, the formation process of the block body 20 in which the first base material 11, the second base material 12, the polarization separation layer 13, and the reflection layer 14 are repeatedly laminated will be described.
A strip-shaped optical block for forming the first substrate 11 and a strip-shaped optical block for forming the second substrate 12 are prepared. The material of these strip-like optical blocks is the same as that of the first base material 11 and the second base material 12.

The polarization separation film 132 is formed on one surface of the strip-shaped optical block forming the first base material 11, and the reflective layer 14 is formed on the other surface. The polarization separation film 132 and the reflective layer 14 are formed by using a conventional method such as vacuum vapor deposition, ion assist vapor deposition, ion plating method, sputtering method or the like.
Next, a plasma polymerization film is formed on one surface of the strip-shaped optical block that forms the second substrate 12 and the surface of the polarization separation film 132 of the strip-shaped optical block that forms the first substrate 11. The method for forming the plasma polymerized film is as described above. Then, a plurality of laminated bodies in which the plasma polymer films are bonded together are laminated to form a plurality of laminated bodies. And this multiple laminated body is cut | disconnected for every predetermined space | interval along the direction L of 45 degrees with respect to the plane. One of the cut blocks has a parallelogram at its end face. The block has a structure in which the polarization separation layer 13 and the reflection layer 14 are arranged at predetermined intervals. Thereafter, a predetermined position of the block is cut along a direction V1 perpendicular to the plane, and the block body 20 is formed.

Next, the process of forming the phase difference plate 15 on the block body 20 will be described with reference to FIGS.
First, as shown in FIGS. 5A to 5C, a plasma polymerization film is formed on the bonding surface 20 </ b> A of the block body 20 including the first base material 11, the second base material 12, the polarization separation layer 13, and the reflection layer 14. Form (polymerized film forming step).
In this polymerization film forming step, the block body 20 is held on the first electrode 211 of the chamber 201 of the plasma polymerization apparatus 200. Then, a predetermined amount of oxygen is introduced into the chamber 201 and a high frequency voltage is applied from the power supply circuit 220 between the first electrode 211 and the second electrode 212 to activate the optical member itself (substrate activation). To do.
Thereafter, when the gas supply unit 240 is operated, a mixed gas of the source gas and the carrier gas is supplied into the chamber 201. The supplied mixed gas is filled in the chamber 201, and as shown in FIG. 5A, the mixed gas is exposed to the block body 20 as a base material.

The ratio (mixing ratio) of the source gas in the mixed gas is slightly different depending on the type of the source gas or carrier gas, the target film forming speed, and the like. For example, the ratio of the source gas in the mixed gas is 20% or more and 70% or less. It is preferable to set the degree to about 30% to 60%.
The frequency applied between the first electrode 211 and the second electrode 212 is not particularly limited, but is preferably about 1 to 100 MHz, and more preferably about 10 to 60 MHz. But not limited high frequency power density, in particular, is preferably about 0.01 to 10 / cm ^2, more preferably about 0.1 to 1 W / cm ^2.

The pressure of the chamber 201 during film formation is preferably about 133.3 × 10 ^{−5 to} 1333 Pa (1 × 10 ^{−5 to} 10 Torr), and is preferably 133.3 × 10 ^{−4 to} 133.3 Pa (1 × 10 ^{-4 to 1} Torr) is more preferable.
The raw material gas flow rate is preferably about 0.5 to 200 sccm, more preferably about 1 to 100 sccm.
The carrier gas flow rate is preferably about 5 to 750 sccm, more preferably about 10 to 500 sccm.
The treatment time is preferably about 1 to 10 minutes, more preferably about 4 to 7 minutes.
The temperature of the block body 20 as a base material is preferably 25 ° C. or higher, and more preferably 25 to 100 ° C.

By applying a high-frequency voltage between the first electrode 211 and the second electrode 212, gas molecules existing between these electrodes 211 and 212 are ionized to generate plasma. The molecules of the raw material gas are polymerized by the energy of the plasma, and the polymer is adhered and deposited on the surface of the block body 20 as shown in FIG. As a result, as shown in FIG. 5C, the first bonding layer 161 that is a plasma polymerization film is formed on the bonding surface 20 </ b> A of the block body 20.
The average thickness of the first bonding layer 161 and the second bonding layer 162 is 10 to 1000 nm, and preferably 50 to 500 nm. If the average thickness of the first bonding layer 161 and the second bonding layer 162 is less than 10 nm, sufficient bonding strength cannot be obtained, and if it exceeds 1000 nm, the dimensional accuracy of the bonded body is significantly reduced.

  Note that the refractive index of the bonding layer 16 including the first bonding layer 161 and the second bonding layer 162 varies depending on the degree of vacuum during film formation. Therefore, a desired refractive index can be obtained by adjusting the film formation vacuum degree of the first bonding layer 161 and the second bonding layer 162 according to the refractive index of the material used for the second base material 12 and the retardation plate 15. The bonding layer 16 having the following can be formed.

Thereafter, as shown in FIG. 6A, the first bonding layer 161 and the second bonding layer 162 are activated to activate the surface (surface activation step).
For the surface activation step, for example, a method of irradiating plasma, a method of contacting with ozone gas, a method of treating with ozone water, a method of treating with alkali, or the like can be used.
Here, activation means a state in which a molecular bond on the surface and inside of the plasma polymerized film is cut and an unterminated bond is generated, or a state in which an OH group is bonded to the cut bond. Or a state in which these states are mixed.
In this surface activation step, a method of irradiating plasma is preferable in order to efficiently activate the surface of the plasma polymerization film. The reason for irradiating the surface of the plasma polymerized film is that the molecular structure of the plasma polymerized film is not cut more than necessary, for example, until it reaches the boundary between the plasma polymerized film and the block 20, so that the characteristics of the plasma polymerized film are reduced. This is to avoid it.

As the plasma used in the present embodiment, for example, oxygen, argon, nitrogen, air, water, or the like can be used alone or in combination. Among these, it is preferable to use oxygen.
By using such plasma, it is possible to prevent a significant decrease in the characteristics of the plasma polymerized film, eliminate unevenness in a wide range, and perform processing in a shorter time. And since plasma can be generated with the same equipment as the apparatus for forming the plasma polymerized film, there is also an advantage that the manufacturing cost can be reduced.
The time for irradiating the plasma is not particularly limited as long as the molecular bond near the surface of the plasma polymerization film can be broken, but it is preferably about 5 to 30 minutes, more preferably 10 to 60 seconds. preferable.
OH groups are introduced on the surface of the plasma polymerized film thus activated.
In the present embodiment, a step of cleaning the block body 20 may be provided between the plasma polymerization film forming step and the surface activation step. This cleaning step is performed using chemicals, water, or other appropriate means.

The block body 20 in which the surface of the first bonding layer 161 that is a plasma polymerization film is activated and the retardation plate 15 in which the surface of the second bonding layer 162 that is a plasma polymerization film is activated are bonded together. Integrate (bonding process).
That is, as shown in FIG. 6B, the block body 20 and the phase difference plate 15 are pressed against each other with the first bonding layer 161 and the second bonding layer 162 made of plasma polymerized films facing each other.
Since the activated state of the plasma polymerized film whose surface has been activated relaxes over time, the plasma polymerized film shifts to the bonding step immediately after the surface activation step. Specifically, after the surface activation step, it is preferable to shift to the pasting step within 60 minutes, and it is more preferable to shift within 5 minutes. Within this time, the surface of the plasma polymerized film is maintained in a sufficiently active state, so that sufficient bonding strength can be obtained at the time of bonding.

By bonding the plasma polymerization films together, these films are bonded together. This coupling | bonding is estimated based on the following (1) or (2) or the mechanism of (1) and (2).
(1) When two base materials, in this embodiment, the block body 20 and the phase difference plate 15 are bonded together, OH groups present on the surfaces of the respective plasma polymerization films are adjacent to each other. The adjacent OH groups attract each other by hydrogen bonding, and an attractive force is generated between the OH groups. In addition, OH groups attracting each other by this hydrogen bond are detached from the surface with dehydration condensation depending on temperature conditions. As a result, at the contact boundary between the two plasma polymerized films, the bonds in which the detached OH groups are bonded are bonded. That is, the respective base materials of the first bonding layer 161 and the second bonding layer 162 constituting each plasma polymerization film are directly coupled to each other to form one plasma polymerization film, that is, the bonding layer 16. . (2) When two base materials are bonded together, unterminated bonds generated on the surface and inside of each plasma polymerization film are recombined. Since this recombination occurs in a complicated manner so as to overlap (entangle) with each other, a network-like bond is formed at the bonding interface. As a result, the respective base materials constituting each plasma polymerization film are directly bonded and integrated to form one plasma polymerization film, that is, the bonding layer 16.

In this embodiment, after the bonding process, the block body 20 and the phase difference plate 15 are pressurized as necessary (pressure process). Thereby, the polarization conversion element 1 is manufactured.
In this pressing step, it is preferable to pressurize the block body 20 and the phase difference plate 15 with a large force in order to increase the bonding strength. Specifically, the pressure for pressurization is preferably about 1 to 10 MPa, and more preferably 1 to 5 MPa, although it varies depending on the thickness of the block body 20 and the phase difference plate 15 and the conditions of the apparatus and the like. The pressurization time is not particularly limited, but is preferably about 10 sec to 30 min.

After pressurizing the block body 20 and the phase difference plate 15, these are heated (heating process). By heating the polarization conversion element 1, the bonding strength can be increased.
This heating step is provided as necessary, and the heating temperature is 25 to 100 ° C, and preferably 50 to 100 ° C. If the temperature exceeds 100 ° C., the polarization conversion element 1 may be deteriorated or deteriorated. The heating time is preferably about 1 to 30 minutes.
In addition, although this heating process may be performed independently after a pressurization process, it is preferable to carry out simultaneously with a pressurization process, when strengthening joining strength.

  In this embodiment, since the polymer film that has not been activated is chemically stable, the block body 20 in which the first bonding layer 161 that is a plasma polymerized film is formed and the second polymer polymer film that is the second polymer polymer film. A number of retardation films 15 on which the bonding layer 162 is formed are manufactured in the polymer film forming step, and stored. And only the required number finally passes through a surface activation process, activates a plasma polymerization film, and can shift to a pasting process quickly, and can improve manufacturing efficiency of polarization conversion element 1.

Here, the relationship between the refractive index and the wavelength when the bonding layer 16 is formed under the following conditions is shown in FIG. The thickness of the plasma polymerization film formed under these conditions was 5 nm or more and 1500 nm or less.
(Conditions for polymerization film formation process)
Source gas: Siloxane gas 10sccm
Carrier gas: Argon gas 10sccm
Processing time: 220 sec
(Conditions for surface activation process)
Plasma: O ₂ gas 20sccm
Irradiation time: 60 sec
(Pressure process)
Pressure 10MPa

  As shown in FIG. 7, since the refractive index of the plasma polymerized film varies depending on the wavelength, it is possible to form a plasma polymerized film having a desired refractive index in a predetermined wavelength region by selecting these conditions. it can.

Therefore, in the first embodiment, the following operational effects can be achieved.
(1) The bonding layer 16 is provided between the second substrate 12 and the retardation plate 15, and the refractive index n ₃ of the bonding layer 16 is the refractive index n ₁ of the second substrate 12 and the refraction of the retardation plate 15. plasma polymerization film to a value between the rate n ₂ are formed. That is, since the refractive index n ₁ of the second substrate 12 is larger than the refractive index n ₂ of the phase difference plate 15, the relationship of n ₁ > n ₃ > n ₂ is satisfied. Thus, since the difference in refractive index between each layer is small, reflection loss at the interface can be reduced. Therefore, it is possible to provide PBS with excellent transmittance.
Further, since the bonding layer 16 formed of the plasma polymerized film is relatively soft, it suppresses expansion cracking of the base material (the first base material 11, the second base material 12, and the retardation plate 15) due to heat. Can do. That is, it has excellent heat resistance.

(2) In addition, since a plasma polymerized film is used as the bonding layer 16 and an inorganic material such as polyorganosiloxane, organometallic polymer, hydrocarbon polymer, or fluorine polymer is used as the raw material of the plasma polymerized film, the inorganic material It is excellent in adhesiveness with the second base material 12 and the phase difference plate 15 formed in the above, and durability is improved.
(3) Furthermore, unlike the case where an adhesive is used, the adhesive does not protrude, so that a good appearance can be maintained.
(4) Moreover, since the plasma polymerized film is formed on the entire bonding surface 20A of the block body 20, a complicated process such as a mask is not required and can be easily manufactured. That is, productivity can be improved.

(5) The polarization conversion element 1 uses a plasma polymerization film for the first bonding layer 131A and the second bonding layer 131B, and the bonding layer 131 formed by bonding the first bonding layer 131A and the second bonding layer 131B. the refractive index n ₁₃ of, and is formed to have a value between the refractive index n ₁₁ of the outermost layer and the refractive index n ₂ of the second substrate 12 of the polarization splitting film 132. Therefore, reflection loss can be suppressed at the interface between the outermost layer of the polarization separation film 132 and the second base material 12, and the polarization conversion element 1 having more excellent transmittance can be provided.
In addition, since the bonding layer 131 is relatively soft like the bonding layer 16, it is possible to suppress expansion cracking of the base material (the second base material 12 and the first base material 11) due to heat. Furthermore, since an inorganic material is used for the plasma polymerized film that forms the bonding layer 131, the adhesion with the second base material 12 and the polarization separation film 132 regulated by the inorganic material is excellent, and the durability is improved.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the bonding layer 16 has a structure in which the first bonding layer 161 and the second bonding layer 162 are bonded together to form one layer. However, the bonding layer 16 is formed in multiple layers and is adjacent to the bonding layer 16. The layers of the bonding layer 16 may be stacked in order of decreasing refractive index from the layer having the smallest refractive index of the two layers. In this case, the refractive index of each layer of the bonding layer 16 is a value between the refractive indexes of the two layers adjacent to the bonding layer 16. Thus, by gradually changing the refractive index of the bonding layer 16, the difference in refractive index between the two layers adjacent to the bonding layer 16 is reduced, so that reflection loss can be suppressed. Therefore, the transmittance is excellent.

Hereinafter, examples will be described in order to confirm the effects of the present embodiment.
About the polarization conversion element of the structure shown in Examples 1-3 and Comparative Examples 1-3, the transmittance | permeability in each wavelength was measured.
[Example 1]
According to the manufacturing method in the above-described embodiment, a white plate having a refractive index n = 1.518 (product name “B270” manufactured by Schott), a plasma polymerization layer (refractive index n = 1.540, thickness t = 0.3 μm) A polarization conversion element having a structure in which quartz (artificial quartz) having a refractive index n = 1.561 was laminated in this order was prepared. Each refractive index is at a design wavelength of 600 nm.

[Example 2]
A polarization conversion element was prepared in the same manner as in Example 1 except that the thickness of the plasma polymerization layer was t = 0.26 μm.

[Example 3]
A polarization conversion element was prepared in the same manner as in Example 1 except that the thickness of the plasma polymerization layer was t = 0.22 μm.

[Comparative Example 1]
White plate with refractive index n = 1.518 (Shot, trade name “B270”), insufficiently cured adhesive (Sunrise MSI, trade name “PHOTO BOND 300”, refractive index n = 1.478, thickness A polarization conversion element having a structure in which an adhesive layer composed of t = 5 μm) and a quartz crystal (artificial quartz) with a refractive index n = 1.561 was laminated in this order was prepared. Each refractive index is at a design wavelength of 600 nm.

[Comparative Example 2]
In Comparative Example 1, the adhesive was sufficiently cured. The refractive index of the adhesive layer at this time was n = 1.502.

[Comparative Example 3]
A white plate having a refractive index n = 1.518 (product name “B270”, manufactured by Schott) and a quartz crystal (artificial quartz) having a refractive index n = 1.561 were directly joined by plasma polymerization. Each refractive index is at a design wavelength of 600 nm.

  About these polarization conversion elements, the transmittance | permeability in each wavelength was measured using the spectrophotometer (Hitachi U4100). The measurement results are shown in FIGS.

  As can be seen from FIG. 8, in Example 1, the loss of interface reflection can be suppressed to 0.02% or less, and the transmittance is stably high as compared with Comparative Examples 1, 2, and 3. On the other hand, since Comparative Examples 1 and 2 use an adhesive, the transmittance decreases due to interface reflection loss, and interference fringes are also observed. In Comparative Example 3, although no interference fringes are observed, there is an interface reflection of about 0.02%, and in particular, in the range of 500 nm or more, the transmittance is lower than that of Example 1. Therefore, in this embodiment, excellent transmittance can be maintained by setting the refractive index of the plasma polymerization layer at the design wavelength of 600 nm within the range of 1.519 to 1.555.

  Further, as can be seen from FIG. 9, the peak wavelength shifts according to the thickness of the adhesive layer. That is, the transmittance characteristic is shifted according to the thickness of the adhesive layer. In FIG. 8, Example 1 shows a high transmittance in the red region (wavelength near 600 nm), Example 2 shows a high transmittance in the green region (wavelength near 550 nm), and Example 3 shows a blue region (around 500 nm wavelength). ) Shows high transmittance. Thus, the transmittance characteristic can be adjusted by adjusting the thickness of the adhesive layer.

  The present invention can be used for polarization conversion elements used in liquid crystal projectors and other devices.

The end elevation which shows the polarization conversion element of embodiment of this invention. The principal part expanded sectional view of FIG. The principal part expanded sectional view of FIG. Schematic of the plasma polymerization apparatus in the embodiment Schematic explaining the plasma polymerization film | membrane formation process in the said embodiment. Schematic explaining the bonding process in the said embodiment. The graph which shows the relationship between the refractive index and wavelength in the Example of this invention. The graph which shows the relationship between the transmittance | permeability in the Example of this invention, and a wavelength. The graph which shows the relationship between the transmittance | permeability in the Example of this invention, and a wavelength.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Polarization conversion element, 11 ... 1st base material, 12 ... 2nd base material, 13 ... Polarization separation layer, 14 ... Reflection layer, 131 ... Joining layer, 131A ... 1st joining layer, 131B ... 2nd joining layer, 132: polarization separation film, 15: retardation plate, 16: bonding layer, 161: first bonding layer, 162: second bonding layer

Claims (6)

A polarization conversion element having a first optical member having a refractive index n _{1 and} a second optical member having a refractive index n ₂ (n ₁ ≠ n ₂ ),
Formed of a plasma polymerized film, comprising a bonding layer for molecularly bonding the first optical member and the second optical member;
The polarization conversion element, wherein a refractive index n _{3 of the} bonding layer is between n ₁ and n ₂ . The polarization conversion element according to claim 1,
The plasma-polymerized film is a polarization conversion element characterized in that the main material is polyorganosiloxane. The polarization conversion element according to claim 1 or 2,
The polarization conversion element, wherein the first optical member is a glass substrate, and the second optical member is a retardation plate made of quartz. The polarization conversion element according to claim 1 or 2,
The first optical member is a glass substrate, and the second optical member is a dielectric multilayer film. In the polarization conversion element according to any one of claims 1 to 4,
The polarization conversion element, wherein the bonding layer is formed on the entire bonding surface of at least one of the first optical member and the second optical member. In the polarization conversion element according to any one of claims 1 to 5,
The bonding layer is formed of multiple layers,
Each layer of the bonding layer is laminated in order of decreasing refractive index from the side with the lower refractive index to the side with the higher refractive index of the first optical member and the second optical member. element.

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